A Skin Test Survey for the Prevalence of SCHISTOSOMIASIS FO in Puerto Rico LIC HEALTH U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE, PUBLIC HEALTH SERVICE ¥ 3 : t ig - 5, - = =r - . : EH < : 4 rae Lox - Y vr Ban ¥ - rz E ‘ " : 3 ‘ et Rl a Cn i a a I LE RES Ea Bde 350 SEH 5 A SKIN TEST SURVEY FOR THE PREVALENCE OF SCHISTOSOMIASIS IN PUERTO RICO Contribution of Irving G. Kagan Chief, Parasitology Unit, Laboratory Branch, Communicable Disease Center Henry Negron Research Medical Officer, Technology Branch, Communicable Disease Center Jesse C. Arnold Public Health Statistician, Epidemiology Branch, Communicable Disease Center Frederick F. Ferguson Chief, Puerto Rico Field Station, Technology Branch, Communicable Disease Center and Laboratory, Epidemiology and Technology Branches of the Communicable Disease Center, Public Health Service, U. S. Department of Health, Education, and Welfare, Atlanta, Georgia; the Bilharzia Control Unit, Vector Control Branch, Bureau of Environmental Sanitation, Puerto Rico Department of Health, and the Department of Public Instruction, San Juan, Puerto Rico. U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE PUBLIC HEALTH SERVICE BUREAU OF DISEASE PREVENTION AND ENVIRONMENTAL CONTROL NATIONAL COMMUNICABLE DISEASE CENTER Atlanta, Georgia 30333 + eOR wil Al. Te aiid Public Health Service Publication No. 1525 September 1966 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON : 1966 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 65 cents ACKNOWLEDGEMENTS The survey task was made possible by the capable and worthy effort of the Health Education Section of the Department of Public Instruction (headed by Mrs. Virginia Belaval) and 60 health educators working all over the island. We wish to thank the assistants in the Statistics Section, Epidemiology Branch, Communicable Disease Center, for their help in tabulating the data. 3 Co QS FAC 44 Ch | 1 = \J 5 ~~ PUBLIC HEALTH LIBRARY CONTENTS 1. THE SURVEY, RESULTS, AND DISCUSSION ..........commmersmummmmnsssososssiisossessos ainsi bmi mss so a ions tom ess $5 sim sorasiasion 1 Material and Methods oe eee omen enema anne anne esse enn eeeseeenseseeseenneenean nD Skin Test ......connmmnsnsons es 3 Survey Population we 3 Criteria for Delineating Major Watershed ATBas ........ccmcminmmmmmmmsmosiimssstommmintsestoss sm istssasissssssssspsss mans 4 SHIDIE DESIG. w.onnsnsosoismsmsnsns inmsiisianinimuinismsmansms isin sso EE hs AS SEA 5 Collection and Analysis of Data _. we 5 Results... ET rE CR EE ET TITS err esse roy cheeses ss ersiussb igs assenmusall 7 DISCUBHION vivnssimmsmnsrsssivmsies imissonini msm nmtomsm sass amass tsa Tn iene tetas rs eS SAR A EEE TE AE UE SE ETERS A 3 IT: 0 ANALYSIS OF STUDY AREAS... isn imma sess astaenis ames ios ie ee oS Bess ep a STO o Se Ras ees 17 BIBLIOGRAPHY ooo eeesssnmssansmmants sms spe sete er so A EE POTEET EER ARR ETT Ss TEST eee eee 81 APPENDIX. 1 .......coooncsonmesonmssesensssmmepsrse sms sss sbr sosmmesss sims anes msnestmmsssmstns = - 33 RPPERDIX. 2 | cvnnesivismniismsnserssisemis nie sammie meessnsesessensesmrs stot asi sgsmatmmimemnsssss sess svsasbnssnbsatasansmebrrassmsstans eta dainine 84 BPPENDIR 3 ... .ociniiniinsninsid iiss shi some is oa SoA ed TO ERE IE eR etree ises sheep seston endus users 88 APPENDIX 4 ooo ssmessvssta samen samen bass mses statin seam essa SiR SEAS Gre Eo SA a SA ES eS St ais 91 LIST OF FIGURES: FEGOTC LincMap Of SUHUY GIOHS ..c.ronsisisnmimisiosiress sms oni os se ses ses 435 EA 3 A A SR HS S50 cor Figure 2.—Study areas with sub-watershed zones Figure 3.—Prevalence rates in urban areas Figure 4.—Prevalence of schistosomiasis in rural sub-watershed areas . 11 Figure 5.—Combined urban and rural prevalence rates for schistosomiasis ........... 12 Figure 6.~Rural communities inn Puerto: RiG0: conwmnmmnmmmismmntiissmmsmmso rasa mans ta sess ss seve stsssscusctusen 14 LIST OF MAPS: Map 1, Area No. Map 2, Area No. Map 3, Area No. Map 4, Area No. Map 5, Area No. Map 6, Area No. Map 7, Area No. Map 8, Area No. Map 9, Area No. Map 10, Area No. Map 11, Area No. Map 12, Area No. Map 13, Area No. Map 14, Area No. Map 15, Area No. Map 16, Area No. Map 17, Area No. Map 18, Area No. Map 19, Area No. Map 20, Area No. Map 21, Area No. Map 22, Area No. Map 23, Area No. LIST OF MAPS: (Continued) Map 24, Area No. 24 Map 25, Area No. Map 26, Area No. Map 27, Area No. Map 28, Area No. Map 29, Area No. Map 30, Area No. Map 31, Area No. LIST OF TABLES: Table A.—Sample size and classroom data for study areas Table B.—Average of antigen wheal (cm?) and control wheal (¢cm2) by watershed area Table C.—Prevalence rates (percent) of skin reactivity in urban areas Table D.—Prevalence rates (percent) of skin reactivity in rural areas Table E.—Prevalence rates (percent) of skin reactivity for each study area for urban and rural schools combined Table 1A.—Distribution of positive skin reactors by individual sample classrooms Table 1B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 1C.—Distribution of positive skin reactors by watershed area, age, and type school Table 1D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area... Table 2A.—Distribution of positive skin reactors by individual sample classrooms... Table 2B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 2C.—Distribution of positive skin reactors by watershed area, age, and type school Table 2D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area Table 3A.—Distribution of positive skin reactors by individual sample classrooms Table 3B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 3C.—Distribution of positive skin reactors by watershed area, age, and type school Table 3D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area Table 4A.—Distribution of positive skin reactors by individual sample classrooms Table 4B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 4C.—Distribution of positive skin reactors by watershed area, age, and type school Table 4D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area... Table 5A.—Distribution of positive skin reactors by individual sample classrooms Table 5B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 5C.—Distribution of positive skin reactors by watershed area, age, and type school Table 5D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area Table 6A.—Distribution of positive skin reactors by individual sample classrooms Table 6B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 6C.—Distribution of positive skin reactors by watershed area, age, and type school Table 6D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area Table 7A.—Distribution of positive skin reactors by individual sample classrooms Table 7B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 7C.—Distribution of positive skin reactors by watershed area, age, and type school Table 7D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area Table 8A.—Distribution of positive skin reactors by individual sample classrooms Table 8B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 8C.—Distribution of positive skin reactors by watershed area, age, and type school Table 8D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area Table 9A.—Distribution of positive skin reactors by individual sample classrooms Table 9B.—Distribution of positive skin reactors by watershed area, stratum, sex and type Table 9C.—Distribution of positive skin reactors by watershed area, age, and type school vi school school school . school . LIST OF TABLES: (Continued) Table 9D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and waterSRed Grea .....omiuumsnmmsinmm——— Fr 35 Table 10A.=Distribution of positive skin reactors by individual sample classrooms... 36 Table 10B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school . +36 Table 10C.—Distribution of positive skin reactors by watershed area, age, and type school .......... ten nen TO Table 10D.—Skin reactor rates and percentage distribution of positives by length of ‘residence, type School and Watershed BIER cuisines ss sh 37 Table 11A.=Distribution of positive skin reactors by individual sample classrooms .......... rms sien 38 Table 11B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school ._......... 38 Table 11C.=Distribution of positive skin reactors by watershed area, age, and type school 38 Table 11D.—Skin reactor rates and percentage distribution of positives by length of residence, type SCHOOL GRA WOIBTBREE ATCO ...onveessrssrmsiinsmnesms ts ssnesprismpsve ns spre ssp assssssns sn pss snsssisns ins 39 Table 12A.—Distribution of positive skin reactors by individual sample classrooms — 39 Table 12B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school . 40 Table 12C.—Distribution of positive skin reactors by watershed area, age, and type school 40 Table 12D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area... 41 Table 13A.—Distribution of positive skin reactors by individual sample classrooms 42 Table 13B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school ._........... 42 Table 13C.=Distribution of positive skin reactors by watershed area, age, and type school 43 Table 13D.—Skin reactor rates and percentage distribution of positives by length of residence, type SCHOOL GIL WOIBTBROD QIBA ......vceensesrsssrerirssns sms rsssmsmessissmpms ramen sass ssnsns abuses mg sins 43 Table 14A.=Distribution of positive skin reactors by individual sample classrooms 44 Table 14B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school ............ 44 Table 14C.—Distribution of positive skin reactors by watershed area, age, and type school 45 Table 14D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area... 45 Table 15A.—Distribution of positive skin reactors by individual sample classrooms .............................. 46 Table 15B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school . 47 Table 15C.—Distribution of positive skin reactors by watershed area, age, and type school 47 Table 15D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area ................... 47 Table 16A.—Distribution of positive skin reactors by individual sample classrooms... 48 Table 16B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school ........._._.._. 48 Table 16C.~Distribution of positive skin reactors by watershed area, age, and type school 49 Table 16D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area... 49 Table 17A.=Distribution of positive skin reactors by individual sample classrooms ................... . 50 Table 17B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school 50 Table 17C.=Distribution of positive skin reactors by watershed area, age, and type school 51 Table 17D.—Skin reactor rates and percentage distribution of positives by length of residence, type School and WatErSROR QRER .....rwvrermsmissimmsioms asin ATR AE Oe sa 51 Table 18A.—Distribution of positive skin reactors by individual sample classrooms 52 Table 18B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school _......._.._. 52 Table 18C.—Distribution of positive skin reactors by watershed area, age, and type school 53 Table 18D.—Skin reactor rates and percentage distribution of positives by length of residence, type School and WOLETSAOL GEE ..........orvevses res sesssspms eemprsms sess spnsi seme s SSRAAR STOESRS 53 Table 19A.—Distribution of positive skin reactors by individual sample classrooms... 54 Table 19B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school .._..._._...._. 55 Table 19C.—Distribution of positive skin reactors by watershed area, age, and type school 55 Table 19D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area ........................ 55 Table 20A.—Distribution of positive skin reactors by individual sample classrooms 56 Table 20B.—Distribution of positive skin reactors by watershed area, stratum, sex and type . 57 Table 20C.—Distribution of positive skin reactors by watershed area, age, and type school 57 Table 20D.—Skin reactor rates and percentage distribution of positives by length of ’ residence, type School anid WALErSREE GrEQ ....... cw rercsrrreresssinsmsesesessssinsmsmersnsisssbsasmsiansistniaia CHAE 57 Table 21A.—Distribution of positive skin reactors by individual sample classrooms... 58 Table 21B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school _....._._._._. 59 vii LIST OF TABLES: (Continued) Table 21C.=Distribution of positive skin reactors by watershed area, age, and type school ._.............._... 59 Table 21D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and WalerShed IEG .......ccumimimmnspismnmn i mS oasis Table 22A.—Distribution of positive skin reactors by individual sample classrooms Table 22B.—=Distribution of positive skin reactors by watershed area, stratum, sex and type Table 22C.—Distribution of positive skin reactors by watershed area, age, and type school Table 22D.—Skin reactor rates and percentage distribution of positives by length of residence, type Sehool and watershed GIEQ sw. mswmm ————— 61 Table 23A.—Distribution of positive skin reactors by individual sample classrooms ........................... 62 Table 23B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school ............ 63 Table. 23C.—=Distribution of positive skin reactors by watershed area, age, and type school ................. 63 Table 23D.—Skin reactor rates and percentage distribution of positives by length of residence; type School and WoteTSRET MICO... mamma 64 Table 24A.—Distribution of positive skin reactors by individual sample classrooms... 65 Table 24B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school .. « 63 Table 24C.—Distribution of positive skin reactors by watershed area, age, and type school 66 Table 24D.—Skin reactor rates and percentage distribution of positives by length of residence, type school ond WoleTSREd BIER ....ccoompmmmirmmmismrmismim mt aS 66 Table 25A.—Distribution of positive skin reactors by individual sample classrooms ............................... 67 Table 25B.—=Distribution of positive skin reactors by watershed area, stratum, sex and type school .......... 67 Table 25C.—Distribution of positive skin reactors by watershed area, age, and type school .................... 67 Table 25D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed Aroq ..o.c..usmmemmusnmumnsstrsn ir ———— Sumit 68 Table 26A.=Distribution of positive skin reactors by individual sample classrooms... 69 Table 26B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school ............. 70 Table 26C.—Distribution of positive skin reactors by watershed area, age, and type school 70 Table 26D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and WALEISREB ATER ous mimosa rye ae tama s Table 27A.—=Distribution of positive skin reactors by individual sample classrooms Table 27B.=Distribution of positive skin reactors by watershed area, stratum, sex and type Table 27C.—=Distribution of positive skin reactors by watershed area, age, and type school Table 27D.—=Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed Grea ......oawpsvimmnmmms is Rk Be 72 Table 28A.—Distribution of positive skin reactors by individual sample classrooms 73 Table 28B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school 74 Table 28C.—Distribution of positive skin reactors by watershed area, age, and type school 74 Table 28D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area 74 Table 29A.—Distribution of positive skin reactors by individual sample classrooms 75 Table 29B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school 76 Table 29C.—Distribution of positive skin reactors by watershed area, age, and type school .........._........ 76 Table 29D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area ........................ 76 Table 30A.—=Distribution of positive skin reactors by individual sample classrooms 77 Table 30B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school 78 Table 30C.—Distribution of positive skin reactors by watershed area, age, and type school 78 Table 30D.—Skin reactor rates and percentage distribution of positives by length of residence, type School ang WaterTSRed Gren .... cummins isis osessisersmmm raves ins 78 Table 31A.=Distribution of positive skin reactors by individual sample classrooms... 70 Table 31B.=Distribution of positive skin reactors by watershed area, stratum, sex and wpe school __........... 79 Table 31C.—Distribution of positive skin reactors by watershed area, age, and type school 80 Table 31D.—Skin reactor rates and percentage distribution of positives by length of q residence, type school and watershed area .................. 80 viii I. THE SURVEY, RESULTS, AND DISCUSSION Puerto Rico is part of a series of moun- tainous islands (Greater and Lesser Antilles) that stretch from Florida to Venezuela and separate the Caribbean Sea from the Atlantic Ocean, It is situated at 18°N, latitude, within the tropics, approximately 1,000 miles east- southeast of Miami, Florida. This island, (100 miles long and 35 miles wide), receives relatively large amounts of rainfall created by uplift of moisture-laden trade winds from the northeast. A classical rain forest has been created as a result of the first impact of trade winds in the north- east highland at El Yunque where annually as much as 200 inches of rain may fall. In contrast, the dry Lajas Valley in the southwest corner of the roughly rectangular island may receive as little as 20 inches of rain per annum. The overall average annual rainfall for the island measures 68.8 inches. A south- central, east-west escarpment, ‘‘Cordillera central,”’ ranging mostly 2,000-3,000 feet in elevation assures that more rain falls on the northern than the southern slopes and thus the largest of many rivers and creeks flow northerly into the Atlantic (Bogart, et al., 1964). None of the streams is navigable, and many serve as an important source of hydro- electric power and water supply for both irrigation and population needs. One large north coast and three south coast irrigation systems serve the sugar cane industry. The 1960 U.S. Census placed the popu- lation at 2,349,544, of which 44.2 percent was urban in nature. Within an area of only 3435 square miles the general population is considered relatively very dense, averaging 686 individuals per square mile (Stat. Absts. of the U.S., 1963). The average family income in 1960 was $1,268 per annum, as compared to the median figure of $5,660 for the con- tinental United States. An average of 4-6 years of schooling had been completed as of 1960 (U.S. Census of Population, 1960). Endemicity of schistosomiasis mansoni, or bilharziasis, is favored by several factors. Many rivers, artificial lakes and hundreds of small creeks serve as permanent snail habitats for Australorbis glabratus, the single known intermediate host of Schistosoma mansoni in Puerto Rico. In arid valleys when surface waters are increased by irrigation the snail flourishes. Fresh water marshes and swamps are common habitats, and there are several hundred man-made farm ponds. A majority of the water bodies are found north of the south- central escarpment. The distribution of A. glabratus is directly related to these water- body patterns. Snails are found in three of the irrigation canal systems but have not become established in the fourth system (Lajas Valley). Distri- bution in the irrigation systems is usually discontinuous. Neither prevailing water tem- peratures, water pH, nor any other physio- chemical factor except gross pollution appears to limit the population density of A. glabratus. The primary effect of alpine terrain is to increase the stream velocities with adverse effect on the snail populations. Streams of higher than a two percent gradient have fewor no A. glabratus (Harry and Cumbie, 1956a and 1956b; Pimentel and White, 1957). Stream flushing at all altitudes kills many snails and also redistributes them to new habitats. In protected upland alluviated plains (for example, at Aibonito) and in limited paralotic sites (usually in marshy pasture land and in very small creek tributaries) A. glabratus will thrive as a potent epidemiologic factor in the transmission of bilharziasis all year long (Pimentel and White, 1959a, and 1959b). The Barranquitas Valley, a classic bilharzia focus, has been studied for seasonal snail population density and distribution. In 1953 A. glabratus occurred abundantly in most parts of the high gradient valley stream system. Subsequently, annual surveys revealed marked population declines; in 1956-1958 a detailed snail survey covering every water body disclosed no bilharzia snails. A. glabratus reappeared in early 1960 and became numerous in 1961-1964. Presumably, infection inthis watershed occurs sporadically (Ritchie, Radke, and Ferguson, 1962). Warm-blooded animals do not seem to be part of the schistosomal life cycle in Puerto Rico, but the subject is worthy of detailed in- vestigation based on the fact that several species of rodents, including common rats, harbor the same species in Brazil (Barbosa, et al., 1958). Crowding of human populations under both urban and rural environments fosters the endemicity of schistosomiasis which is correlated with unsanitary living conditions and ignorance of the occurrence of trans- mission of the disease. Within limits, heavy concentration of slum type housing closely associated with streams provides some organic pollution stimulating the growth of colonies of A. glabratus; industrial pollution, however, generally decimates snail colonies. Although poor housing and poor sanitation practices may provide a vehicle for maintenance of schisto- somiasis in many parts of Puerto Rico, the infection may be contracted by the emerging middle socio-economic class because of close relation of infested streams to large suburban housing developments. Disposal of schis- tosome-bearing feces is important epidemio- logically under these circumstances: (1) random waste depositions in farm fields near, or in, water bodies; (2) depositions near streamside homes lacking latrines; (3) de- positions under stream bridges; (4) situations where latrines flow over, or septic tanks leak to ground surface and liquid wastes are led away purposefully to the nearest water body. Some types of municipal sewage systems allow passage of a very low percent of viable S. mansoni eggs to receiving streams which is an unevaluated factor in the epidemiology of schistosomiasis. In endemic areas, residents contact in- fested water through work when watering animals and washing vehicles; during bathing, swimming, and water play; and by drinking from cercaria infested sources. Most in- fections in Puerto Rico appear to start early in life as a result of children playing in water bodies. The infection rate rises sharply to a peak in the 16-20-year-old group (Kagan, 1958). Schistosomiasis is known to be distributed intermittently on the island, but is more concentrated in watersheds east of an Arecibo- Utvado-Ponce line. Certain towns are classic foci: Ceiba, Comerio, Caguas, Aibonito, Barranquitas, Patillas, Guayama, and May- aguez. Metropolitan San Juan, which includes one-fifth of the total population, is free of bilharzia infection hazard except for the southern sub-urbanizations of Rio Piedras and Bayamon. Fortunately, the most extensive areas of low economic housing are located in close proximity to, or are backed up to brackish water channels which are incapable of supporting A. glabratus. Health officials in Puerto Rico view the disease as a significant problem but not to be dissociated from the total problem of gastroin=- testinal syndromes including malnutrition, intestinal malabsorption, and common helminth parasitoses. The public views it as a debilitating bothersome infection which may lead to important chronic conditions. Educated and informed persons, when infected, suffer emotionally. There is a strong public concern for the development of methods for abatement of bilharzia, Bilharzia in Puerto Rico has received the attention of a host of investigators since its discovery in Mayaguez in 1904 (Gonzalez- Martinez, 1904). A bibliography of 271 references covering the period 1904-1962 has been published (Casas de Lopez, 1963). These studies include all phases of the parasitology, biology, epidemiology, and medical aspects of the disease. What little is known about bilharziasis control is also an important com- ponent of this history. On the basis of promising results in several small control projects developed during 1952-1954 by the Puerto Rico Department of Health and the Communicable Disease Center, Public Health Service, interest has increased greatly in recent years with regard to information on the prevalence of schistosomiasis mansoni. During 1962-1963 a literature survey was made with regard to the diagnosis of S. mansoni in order to provide a reference framework for the skin test investigation reported in this paper and for other control purposes (Ferguson, 1965). Perusal of the literature revealed some conflicting information with regard to the prevalence of infection depending on the diagnostic method used. With the technique of examining micro- scopically a single stool specimen using either simple saline smears or concentration methods, a total of 240,605 examinations was reported, of which 23,266 (10%) were positive for ova of S. mansoni (Maldonado and Oliver- Gonzalez, 1958, 1962; Febles and Brooke, 1961; Friedman and Shookhoff, 1957). Diagnosis by microscopic examination of 292 rectal biopsy snips indicated 109 (37%) were positive for S. mansoni ova (Lyons and Benson, 1954; Trubowitz and Redish, 1950; Pons and Reyes, 1950; Latty, et al., 1954; Gouveia and Beamer, 1955; Springharn, et al., 1957; and Kagan, et al., 1962). Evaluation of 3,066 autopsy specimens for schistosomal pathology showed 467 (15%) with evidence of tissue damage caused by schisto- somes (Burke, 1929; Pons and Reyes, 1950; Koppisch, 1931, 1941; Lambert, 1927, 1928; Lambert and Burke, 1928; Martinez-Rivera and Koppisch, 1956). Skin tests for detection of antibodies in a total of 11,932 individuals revealed 1,811 (15%) with positive reactions (Horstman, etal., 1954; Kagan, 1959, 1961; Kagan, et al., 1962). Serologic tests, specifically the comple- ment fixation test, were made on 276 sera, of which 44 (16%) were positive (Horstman, etal., 1954). Evaluation of these reports indicated thata single estimation of the prevalence rate for bilharziasis on the island cannot be made due to inherent difference existing between the various testing methods employed. Prevalence from examination of single stools indicated a rate of 10%; results from rectal biopsy ex- aminations showed a rate of 37%; figures from autopsy records pointed to a rate of 15% of the subjects investigated with frank pathology; the infection rate based on detection of sero- logic antibody or intradermal antibody appears to be 15%. The generally held opinion regarding the Puerto Rican infection rate is that it does not exceed 20% of the total population for the period of record, 1904 to 1964. The present investigation was designed to estimate the prevalence of infection with S. mansoni on the island of Puerto Rico. At the present time it is not possible to provide the definitive prevalence rate for this disease. However, this study does clarify the picture in a restricted section of the population during a period of less than one year. It is the first comprehensive survey made for schistoso- miasis prevalence in Puerto Rico covering every part of the island and including Vieques Island. The survey tested a randomly selected population of school children in the fifth grade in the age range of 10 through 13 years. The project involved a total of 10,824 intradermal injections performed on groups of children in 390 schools between December 1962 and June 1963. Skin sensitivity against an antigen prepared from adult worms of S. mansoni was the test criterion. All of the injections were made by one of the authors (H. N.) using a single lot of antigen. The watershed area was chosen as the ideal geographic study unit since the endemicity of schistosomiasis is directly correlated with the presence of infected snails in streams and near water bodies. Material and Methods Skin Test The skin test employed was similar to the procedure used previously by the senior author in Brazil (Kagan, et al., 1961). The antigen was an extract of adult worms of S. mansoni in modified Coca’s solution (NaHCOj;, 0.275g; NaCL, 0.5g; MerthiolateR, 0.02g in 100 ml of distilled water). Exactly 0.05 ml of antigen and a control injection of Coca’s solution were inoculated on two sites on the back of the individual. After 15 minutes the edge of induration was outlined by a ball point pen, and the outline was transferred to a data sheet (Appendix I) which had been slightly moistened with alcohol. The area of the wheal was measured with a template (Pellegrino and Macedo, 1956). A wheal area 1 cm? or larger and at least two times greater than the control wheal constituted a positive test (Kagan and Pellegrino, 1961). Survey Population Approximately 90% of Puerto Rican chil- dren in the school age range attend the elementary section of the public instruction system. Any of the first six grades furnish relatively complete population samples for diagnostic survey purposes since attendance is compulsory. Population sampling excluded all private schools of whatever sponsorship, the Univer- sity of Puerto Rico Elementary School, and the Antilles Command School System. At the time the protocols were formulated, it was believed that the group to be sampled would be available at a later time should further studies of the survey population seem desirable. For this reason, the fifth grade school population, which would be available during the following year, was selected for the survey sample. Data were available on the sensitivity of the intradermal test among children in this age group from other studies of this type (Kagan, et al., 1961). Schools in Puerto Rico are located relatively close to where students live and are well dispersed throughout the island, thus providing a fairly reasonable geographical representation of the distribution of the children. It should be noted that not all children in urban designated schools are urban residents but live close to the urban area. A list by school districts of all schools having one or more classrooms of fifth grade children was furnished by the Statistics Section of the Puerto Rican Department of Public Instruction. The list gave the name of the school, total children by sex, and number of fifth grade classrooms for each school con- taining a fifth grade. All schools with a fifth grade, along with the name of the school and the school code number, were precisely located on a 1:30,000 projection U.S. Geological Survey Topographical map. The schools were then further located with an identification number on a 1:120,000 projection working map of a more convenient size. The schools were iden- tified on the map as urban or rural and by the respective municipality in which they were located. Criteria for Delineating Major Watershed Areas Puerto Rico can be divided into 53 major watersheds (Pico, 1950; Pimentel and White, 1957; Harry and Cumbie, 1956a; and Ferguson, 1965), and the epidemiology of schistosomiasis is generally directly correlated with trans- mission within these watersheds. Watersheds with similar physical conditions and similar expected prevalence rates were combined and a total of 30 watershed areas covering the entire island was designated for sampling (Fig. 1). The nearby island of Vieques was also included, making 31 separate study water- shed areas. The 30 study areas were further sub-divided topographically (Fig. 2) in order to have smaller, more workable units and as an aid in pinpointing focal areas of endemicity. These divisions were based upon the same criteria (minor watersheds within the larger watershed area) as was used for the major areas. The prevalence of schistosomiasis was known to be higher on the eastern half of the island before the survey was designed (Pimentel and White, 1957; Faust, 1933; Ferguson, et al., 1958; Weller and Dammin, 1945). Watershed areas on this portion of the island were purposely subdivided further so that endemic areas could be more ac- curately surveyed. Some of the large eastern watersheds were divided into two and three study areas. Study areas 4, 5 and 8 comprise one major watershed. Areas 12, 18 and part of 19 com- prise another watershed. For the most part, the watersheds are smaller in the eastern section of Puerto Rico and some of the study areas, even though small inarea, contain more than one watershed. In the western half of Puerto Rico where the watersheds are larger, schistosomiasis is not as great a problem. Accordingly, the study are- as in the western half of the island were made Figure 1.—Map of study areas. Mayaguez Figure 2.—Study areas with sub-watershed zones. larger by combining several watersheds. A substantial sample was drawn from these large areas In order that estimates of prevalence rates for each of the watersheds within the respective study area might be made with some degree of precision. The schools were regrouped on the above basis, so that for each major study area there was a list of all fifth grade schools, classified by type of school (urban or rural) and location within the subdivision of each major watershed area, Boundaries for the 30 major study water- shed areas were marked on both 1:30,000 and 1:120,000 projection maps, thus clearly defining the school populations to be sampled for each area. Within each major watershed area, boundaries were also drawn to define the in- dividual sub-areas (strata). Sample Design The survey used a stratified random cluster sampling technique. The primary and only sampling units were fifth grade classrooms, of which the children within the classroom were the elements of the cluster. The schools were geographically stratified by the sub-watershed areas and sampled in proportion to the number of classrooms within the strata. Thus, the probability of a particular school being included in the sample was pro- portional to the total number of fith grade classrooms in the school, and the number of schools selected within a sub-area was pro- portional to the total fifth grade classrooms within the particular strata. Urban and rural schools were sampled with different sampling ratios in order to obtain separate estimates for each. Sampling in this an manner, the data could be pooled to make an overall estimate of the prevalence rate for the major watershed area and, if desirable, major watershed areas could be grouped to estimate prevalence rates for regions of the island (two or more watershed areas). The total sample for the entire island included 390 classrooms from a population of approximately 1,666 fifth grade classrooms, or about 1 classroom in every 4 on the average. The sample sizes were calculated sep- arately for each major study area using a finite correction factor since the sample comprised a sizeable proportion of the total fifth grade population. The sample sizes were calculated so that the maximum expected absolute error of the estimated prevalence rates would be approx- imately 5 percent or less. Ideally, the sample size would be estimated using the variance formula for the ratio statistic (Cochran, 1963). In order to use this formula in calculating the sample size needed for a specified degree of precision, several population parameters must be estimated in advance. However, in this study it was not possible to obtain accurate estimates of these population parameters, so the sample size was determined by calculating the sample size needed assuming simple random sampling of students with the estimate proportion of positive reactors equal to 0.5, and increasing the sample size 15-30 percent, depending on the amount of in- formation that was known about the particular area with regard to the prevalence of schisto- somiasis. Collection and Analysis of Data Since it was impractical to hand-tabulate the data, the forms on which the information for each individual child was collected (Appendix 1), were coded (Appendix 2), and punched on data processing cards. The cards were then tabulated with the use of a sorting machine. Records were kept on the total number of children, number of forms, name of school, major area, and sub-areas for each individual classroom surveyed. The statistic used in the analysis was a ratio estimate in which the numerator (the number of positive skin reactors) and the de- nominator (the total number of children) were both considered as random variables. If X and Y represent the total number of positive skin reactors and the total number of children, respectively, for any given area, then let x and y be the sample estimates of the respective population totals. If R = X/Y denotes the true ratio of positive skin reactors to the total children in the population, then r - x/y (where x and y are defined above) can be shown to be a consistent estimator of R. Definition of symbols is as follows: M = total fifth grade classrooms in stratum h h h=1,2,----L m= sample number of classrooms in stratum h N = total children in classroom i, stratum h jul, I wen N n = sample children in classroom i, stratum h Then: x= x} = ro X,. = — — ’ h hPh 7 hi Tf mp § Wp hi is an unbiased estimate of X. Similarly Y may be estimated by formula (1) by substituting y’s for x’s. The approximate variance of the ratio estimate can be calculated from the following formula: 2 02 RZ LM, Mp -m 4 Ma h where 2 2 2:2 Si Spy + RIS} - RS, 2 =~ 5% Bry Tu hx M -1 and similarly defined for the Y’s, Mo (X xy) vy, -Y h h hxy Mm, -1 ) Confidence intervals for the ratio estimate were calculated from the following formulas: Lower Limit: {9 r+t Ss a r Upper Limit: where t is the normal deviate, « is the level of significance and 832 is the sample estimate of af . A great deal of time involved in this study was the travel time required in reaching a school and then preparing the room and children for the skin testing. The time required for the skin test and reading of the tests was relatively short. Therefore, the survey team could test an entire classroom in only slightly more time than would have been required for sampling only a proportion of the classroom. For this reason, there was no second-stage sub-sampling in- troduced into the survey. Ideally, it would have been better to sample a larger proportion of schools (primary units) ‘and a smaller propor- tion of the listing units (children within a classroom). Had this been feasible, the precision could have been considerably greater with the same number of children sampled, or the number of children sampled could have been reduced and still have been within the margin of error previously decided upon. However, since the larger proportion of time and cost involved in the survey was in reaching the school, and not in the actual testing upon ar- rival, fewer primary units were sampled taking 100 percent of each. A detailed exposition of selection of sample points (classrooms) for area 12 (the first area tested in the survey) is outlined in Appendix 3. The methods used to calculate ratios of positive skin reactors to total number of children, estimated variance of the ratio estimate, and the 95 percent confidence interval for the population ratio are outlined in Appendix 4. Results From 1,666 fifth grade classrooms in Puerto Rico, 390 (23 percent) were sampled (Table A); 11,867 children were registered and 10,824 (91 percent) were skin tested. The average wheal areas for urban and rural populations are listed in Table B. In only four watershed areas (#1, 2, 3, 5) were average wheal areas equal to or greater than 1.0 cm? and in only two water- sheds (#2, 3) were the combined wheal areas in this range. The size of the average wheal area may be a reflection of the intensity of infection. The prevalence rate of skin sensitivity in urban school children is tabulated in Table C. Prevalence rates of 32 percent and 37 percent were obtained in areas 3 and 5, respectively (Fig. 3). Rates in the twenty percentile group were obtained in areas 2, 7, 8, 12 and 13. All of the high urban school prevalence rates are in the eastern third of the island. The relatively high rate of 18 percent for area 22 and 19 percent for area 28 is expected since these two regions are known endemic areas for bil- harziasis. The highest urban school skin reactor rate was 61 percent in one school in Juncos in area 5. The island-wide prevalence rate of skin sensitivity for urban school students ad- justed for sample size was 12 percent. Rural school prevalence rates are tabu- lated in Table D. Areas of high skin reactivity are found again in the eastern third of the island (Fig. 4). The high skin reactivity (42 percent) in area 2 was unexpected. Snails were collected from the streams adjacent to the schools sampled Table A.—Sample size and classroom data for study areas Total Number Number Percent Atos number | Number Sample classrooms not : not classrooms tested size . sampled tested tested in area Lee som wc 0 cvs i msn BOE SBE RE AV REE 18 10 217 13 230 5.7 lr on i 1 es anil is 2 Fei lanier od #5 he es Ben 5 22 10 230 29 259 11.2 eT Tal 17 8 220 25 245 10.2 srs + i mon 0 ow Te we Bw EE 39 11 309 21 330 6.4 B Lvs minr min uns smi MERE AE EERE MER HT WE 39 12 375 21 396 5.3 6 Te 101 oe 50 © 5 tr 0 Boia 3 oh i 4 Wn 3 00 4 2 00 Wie AAR 27 10 331 35 366 9.6 To sinew em 0 6 EW WS WE 44 11 334 20 354 5.6 Bru nS EE A NIG GB RB RF ee 8 BE ERE AE PAE ee 15 14 437 29 466 6.5 000 wnloid ol see nles Fes hs eo! hbo ares! fo Yn oblate) rien 4 204 17 516 72 588 12.2 0 or 5 2 0 ww 0 0 ES PEE EE PY PC EEE EOE SHEE 106 16 496 24 520 4.6 LE cron sem cron 1m re Bs ees 0 we nh nto stn i She 7 5 120 13 133 9.8 Nc rion wr Ts armpit Rin to ign ny Be oe sis ia oF iy si 76 16 512 34 546 8.2 13 concn me vr mn rE AE SERRE ER RAE SE RSS ES 30 11 294 38 332 11.4 PN 42 13 397 31 428 7.2 1 IE ea TE Toy for ed TIE r OLE Fron Porry 69 15 411 59 470 12.6 MG Lor. +f cont Bs ll 0 Tok) 8 Bic, et 0 dd cc. B58 oe sh ED 9) iB rd 24 9 292 12 304 3.9 I 21 9 188 24 212 11.3 UB cv: 1 1 serson oon cor 2 lesen vs see or ny 03 rss dh Bat 38 12 366 38 404 9.4 XG ins mn 2 2 rE en ES Ei HY PY Ve pei Brg 90 16 479 50 529 9.5 DO och v5 WE 50 RR TNS BEY HB ES EE 41 13 380 27 407 6.6 2 en ye ww ww 37 12 300 44 344 12.8 DO 1 75 & me RE AR FE PUES SE RAT WE PE LET EE Rh 67 18 456 48 504 9.5 OY + oc i # rk or As We BB RE Br ARE AEE RE 8 93 18 505 58 563 10.3 Bh eve es as AT ke 66 17 458 40 498 8.0 RE IT I, TIT 15 5 88 11 99 H.1 D0 «1650 5 die bn ross 6 Bk scion che rend Behl BD Sl Bonar ® Bat 2 is Winnie 188 28 706 60 766 7.8 2 i ii terrae a eae 42 14 344 33 377 8.8 Ree 1. To ToT 39 10 281 21 302 7.0 BO 1 tes grr of vs lS i hse Sc wos cb ed fds oi 55 15 387 42 429 9.8 | eT IIT IL TTI Tr. 31 11 297 52 349 14.9 4 | 4 4 98 19 117 16.2 Table B.—Averages of antigen wheal (em2) and control wheal (cm?2) by watershed area* Watershed area Urban schools Rural schools Urban and rural combined Average Average Average Average Average Average Number : . Number . Number : tested antigen antigen tested antigen control tested antigen control area area area area area area Loocinssamannmameswnannes unis 135 0.70 0.52 82 1.15 0.58 217 0.97 0.56 An BR 94 0.80 0.50 136 1.05 0.45 230 1.00 0.46 Birnie dr ensue pp 78 1.00 0.45 142 1.22 0.42 220 1.17 0.43 A hse Sn BEE shen 119 0.70 0.48 190 0.75 0.53 309 0.74 0.52 Be el al Weber re 188 1.02 0.38 187 0.94 0.42 375 0.96 0.41 B's 0 wnat s HEBREWS BE 149 0.90 0.50 182 0.94 0.52 331 0.93 0.51 Tie Te TR mens yes tee 123 0.91 0.47 211 0.85 0.50 334 0.86 0.49 po 219 0.85 0.43 218 0.87 0.42 437 0.87 0.42 D0 m0 00 2 20 0 Ha Sa ts Ra 298 0.79 0.54 218 0.81 0.53 516 0.79 0.53 Bn et itvards wk 3 Els 266 0.65 0.42 230 0.70 0.45 496 0.68 0.44 11 oinsnmernenn sim iimis noms - - - 120 0.68 0.40 120 0.68 0.40 Y2 imiiinns pues musa veins sma 217 0.75 0.38 295 0.66 0.37 512 0.71 0.38 IB 0m unas sme rns costing wins us + wimils 124 0.92 0.50 170 0.83 0.46 294 0.87 0.47 ME + ah Sy 179 0.71 0.42 218 0.70 0.43 397° 0.70 0.43 IB ..vmsmerminsnme ents nds va ssans 173 0.71 0.46 238 0.78 0.48 411 0.76 0.47 JG eo enon dentist eae irs Won ite 85 0.75 0.50 207 0.58 0.38 202 0.61 0.41 17 sovvomvnmins sng nan vu s was wns 59 0.75 0.50 129 0.65 0.47 188 0.68 0.48 18 ssnrrnss ons sist assame nnn sme 140 0.63 0.50 226 0.70 0.46 366 0.68 0.47 Britto teinte ni nel lee et ee 243 0.64 0.45 236 0.66 0.45 479 0.66 0.45 20 vee we frm sams REE Ems Ba 162 0.56 0.38 218 0.59 0.40 380 0.58 0.40 IN cer iin die din 4 a 8 es 167 0.77 0.42 133 0.62 0.38 300 0.69 0.40 SC ge 137 0.98 0.62 319 0.93 0.63 456 0.94 0.63 2B nies wit ARM Gn EAE hn ns 284 0.62 0.43 221 0.69 0.51 505 0.65 0.47 Lv wre ee dee ail oe 2 Ye 207 0.58 0.40 251 0.72 0.48 458 0.69 0.46 DB worms rman mau samy: HELA — - - 88 0.70 0.58 88 0.70 0.58 D0 5m nh a ie iy wn 4 in 361 0.60 0.39 345 0.64 0.41 706 0.63 0.40 T vv vmvnmn ewe vue enw ewes wg 18H 98 0.78 0.45 246 0.70 0.51 344 0.71 0.50 2 i vanes 8 RBA BE EAE hn enn 2 229 0.81 0.41 52 0.57 0.37 281 0.77 0.40 AO Ft n yi fi Ltt oh boda wd 178 0.73 0.50 209 0.67 0.39 387 0.64 0.43 0 oohpavmrsmenaes amen: vm pn de 152 0.74 0.50 145 0.65 0.45 297 0.68 0.47 31 (Vieques) ..............c.... 22 0.70 0.50 69 0.87 0.50 98 0.78 0.50 Total :ussnessnivinisnnsns 4,893 * * 5,931 * % 10,824 * % *Averages not calculated for totals because of unequal sampling ratios. Table C.—Prevalence rate (percent) of skin reactivity in urban areas [Urban schools] Area Subarea 1 | Subarea 2 | Subarea 3| Subarea 4 Total Standard urban | deviation (1+2) rk ie HTS, STR dn Rr A et BT 1 cerrviin 1 mim woe 1) ee a de aE 6.7 1.7 Dc er hn En Teas TE Ean ie Tm Pils tan Reet 3 | comresion || mene sme mete 21.3 4.4 B 0k 5 in TE Dn an dT TRE RN Bak 5 0 Sn A aD 0 meter BPA Viste Sb trie 32.1 7.6 (1+2+3) Be nn Cr RES SR ERE HED EE RE BE LE EE BOL Lh tiation |r mmsdnrmlh wn ems as 10:1 1.0 (1+3) De Re tu mi Tle Dar © ms A rrr mR EI Err] B73 | csmrrnms | evsmase | weimasva 37.3 6.7 Br eaTnite Fo ATT ween sols ws wsdl ERs reer oreo be nal Tod — 18) 0 wvsv nme wns wien 18.1 1.6 ad nvr Sn mF sire A vw BE wr Dt ened Bale 22.6 BLA | u.inerec] siswsins 28.2 3.3 (1+2+3) CRN ete impr cman opie os Ts es oe ose Pa a eR 20.8 le ae dtr bos ot wrt amd) ere die 22.8 3.6 OF wiv wars oid oa 5 SE SRE SS BIE Ee RE Be 10.9 BO | viinisme | ve eemeinm 10.7 2.2 (1+3) YO ccs mmo cms wim 5 20s 0 900 + Biws win © 5 06 WEE GRE FREE M2 J cinsseme | monae iim i sms senes 16.2 2.4 ria i reared ee ef, Inti ee rt betel ado _— mE Ln hrs rir nla —- - (2+3) RD es 4s = Seis si Bt ts BT SER A el vt ec sh 7.3 V6.7 [obo 46.3 20.4 3.2 I Se NE po MOTD A Re ro 26.2 | ..cuenes 13:6 | swremmes 20.2 3.5 pr TIT LI tL IIT TI TL rrr (rn 4.5 196 | penne 14.9 3.2 (1+2) (3+4) 15 avo win von o wim 5 wes wm 8 SHWE I WY ER ER EE 0.7 | seonuine YoY iss sien 9.6 3.0 ee ere con Ee os #7 os Bt ie coal svgzsere. ice rns 15.3 loweonvuwn | icrcrmnsy 15.3 1.3 BE rcs 5s vn ne vr Cwiets hn © Pra Tn ety tw Ah sl B10 | wovevsem ll wevsmsns | tarsaess 11.0 2.4 UB i500 atin wird vn i ats sf le SEER BR RIT | Hk wile 7.4 9.7 | ens 8.6 1.2 (1+2) (3+4+5) LO ri ones von 5a I 6 RRS NRE RE SRE REE Sd ZB fo vrrmmeni 6.0 | eons 6.7 0.6 DD rs ws: lien een Be ce dn ERE Epon femoral ws mie goons ein, 29 «ism fm wie ee 4.9 0.5 0 re ox en 5 EE © re Eh RSE EE REE 186° commis sovemvem | Sonermes 18.6 3.7 (1+2+4) ere Sooty oc one el gots a Bo eens ces Fe toon, eg RTE © (ioe cnmmvininl Bree ime Low Baas 17.5 5.8 23 ere 5 ove Sunn BE EE © WE FE ERE 8 PEE EY etl | ks fe 4:8 | cocina 3.9 4.3 1.0 (1+2) tori vous mono abn lier of cl sin vgn ie 4.9 | sesemsses 16 || comiour: 3.5 1.4 OB os hE EERE ESR EW RE A SS SE TE EE AE A - - — - - - (1+2) (3) (4+5) (6+8) D0) vic si BCR BE © eS SAGE BE HRE 5 ahe § 5.2 6,2 5.1 3.6 5.0 1.1 (2+3) DT ceo s ong os me ol ns © ST © ETT § EE GRE RETR] 4 Oe Rai 16.3 | visivnns | vevuvans 16.3 2.4 DB iis CE A SRE ER EEE ERE SBE Ee Be eden ra 1837 = J | orm smn] bent innne J) 10h Mtns 18.7 6.0 (2+3) DO. ive ww 2 SE ERE 5 CE SU Ee ESR ER EEE EAE 9.5 Y0.B" | womommna | ot ation 10.1 1.7 OI cassie eis stn Ps Lb abs sss met hed sv lt at pr 79 | conremes J cnmremes | wrmesnes 7.9 1.3 Revit Bias tee oo i 1 et 0 al HRT AEE EA EA Sd swsswmes | ssmarkas f wena 3.4 Figure 3.—Prevalence rates in urban areas. Table D.—Prevalence rates (percent) of skin reactivity in rural areas [Rural Schools] Area Subarea 1 | Subarea 2 | Subarea 3 | Subarea 4 Total Standard rural | deviation Le cs tbe 5 vn ne hd es Bn cs ee oo SE 4 38.7 BLidh (rrr x Ania Ri 34.0 2.0 AE DE DE Bh BY EB #8 BB 35.4 479 | sewsvmee | smwsswne 41.7 3.8 BL cons et ow 9 st Et LN AD 2 HEL 42.6 260: ll omavhes bmn ani 31.6 3.7 BY co 75 5 en en BRE BR 8 REE WD £ RE § ERRATA 17.5 14.0 4.7 [| cewenmne 9.2 3.4 B cna i BEA RE IE EI WEA RAE MEE BERGA AE RE 16.3 40.7 32.9 [| covwisms 31a 3.6 0 0 i x ww ww wn RW 28.6 5.9 cores wm 26.9 10.2 (3+4) ER os cic bn ts ese nen Rich bn Bf i. de hl ihe a of 16.7 21.8 BL]. Li. dsevean 26.2 5.8 BY cv EB OE BE EE BE OE § © FO 5a © EY § 24.1 16.7 28.3 | cineavns 22.6 3.5 Dk EE REA REE Se GE EE ST ARE EE EE SOE 19.0 4.2 |) sameswas | siwennms 15.6 4.8 JO hei nigiion 3 vo oes on ow dl wi wf on 2 pa rp SE 7.6 6.4 96 | civevume 8.3 2.0 TT mT TTT” 153.0 | soviwvnn | sumuswrs bo vovmenns 15.0 2.7 (3+4) ED a nai ump et ee rE TDR TOE A TB RE TE 13.0 5.9 1726 | ..cuvun. 12.8 2.9 (2+3) LT viv mw mi 0 WE 14.5 1858 | cuvciwin [ vonmmones 17.3 5.3 DE im i ms wo 0 Rn ®VE WE eS ES SRR 1.2 32.9 13.8 | wsncrrus 17.1 7.6 tr cee tl Wns eh to ts bs 2 2 stv be codon nds ss is Bo ld 17.9 8.3 14.1 9.8 13.0 4.9 1 1 1 HCI 5.0 48 | cevvenee | sienna 4.8 0.8 UT ii and di 2 il 55 TEE Bark © oie Horde 6 i Bs 8 HF i 6 4.4 5.0 | .iessmes | crassa 4.6 1.4 Bn 5a wit win es ns Rin ele Ea Bo i He lo RoE 7.0 6.6 i: JE Ep 9.6 1.9 (1+2) (3+4) (5) 10 4.7 2.2 V2.7 . If Foe fone 5.5 1.0 RO 5c 0m £0 5 50 © eB BER RR TE © Ep RE @ REE EG § 8.8 D2 | cemzames |) srwnsewe 6.2 1.6 IONE 8 oct: nes cin ee Bol es es os ir Wil ois be, Bd) i ns Zi. | cemrmnnn ll] sown ames Blo vos an 7:8 4.0 DD cv wr 7 EE gE 6 EE EE 9 EE EE 24.0 8.6 5.7 21.2 16.2 2.6 D3 ERE REE EE EEE GN EER RE RE 9.8 $4.1 Uf icesaes 1.8 5.6 17.3 (1+2) D0 oi i SE EE BU BD EB A SR BA % SE 8 6.2 J} sweemmis 11.8 13.1 10.2 4.1 DB tm om. a #4 wh mn on EH WR Se Bd | ceeremin bl remermre | ermine 3.4 1.2 (nn @] 3) (5+7) (6) (8) VB csi a EEE REIS BRT EAE EY GET ES — 3.6 13.3 — 5.6 3.6 10.6 8.1 1.8 DT i x tro www ew a wy ep 3.8 4.9 44 | ........ 4.4 1.3 BB som snr tomesi ss mms ses hs nanos tess awe I 88 | cemeomenl] sonsrams § vinmarne 5.8 0 B00): Yutors ee stim. sons vs i ch ves is lis se ae vo do Tpl i he secioon 9.8 7.4 8:8 | Liens 7.6 1.0 BO io cin xvi = wi EE BE RE UE © EE SE RHEE AE 8 | cuscamen] semeswas | simmesms 4.8 1.6 BL ots scm cos 3s 1 Sh RF Ss VIB | voenmmen ff rommamen Bi wo ime vos 14.5 0 *Vieques Island 10 Figure 4.—Prevalence of schistosomiasis in rural sub- watershed areas. and A. glabratus shedding cercariae of S. mansoni were found, confirming that trans- mission was taking place in this area. Two new small areas of endemicity related to the develop- ment of ‘‘parcels’’ (housing developments for rural people) was found in area 18 and in the southwestern corner of area 15. Of interest is the distribution of positive reactions in area 4 with one sub-area of low prevalence. The high endemic area along the coast in area 14 (sub- watershed #2) is well known and is due to extensive sugar cane acreage with irrigation. This also accounts for the high prevalence in the southwest corner of area 15 (subwatershed #1). The two high areas in watershed 22 are recognized endemic areas in the Utuado and Jayuya regions. The island-wide rural preva- lence rate was 13 percent. The combined prevalence for urban and rural schools is tabulated in Table E. The endemicity of bilharziasis is 20 percent and higher in areas 2, 3, 5, 6, 7, and 8, and 15 per- cent to 20 percent in areas 11, 12, 13, 14, 22, and 28. In only two areas (#23 and #25) were the combined prevalence rates less than 5 per- cent (Fig. 5). The total prevalence for both urban and rural school populations was 12 per- cent, A general gradient of the prevalence of bilharziasis from east to west can best be discerned from perusal of the tables and from a detailed analysis of results obtained in each study area found in Section B of the manuscript. Data for each watershed area is summarized in four tables as follows: TABLE A - Distribution of positive skin reac- tors by each sampled classroom 11 i] 5-10% [J ro- Cl d under 5% Cl 15-20% over 20% TABLE B - Distribution of positive skin reac- tors by watershed area stratum, sex, and type of school TABLE C - Distribution of positive skin reac- tors by age and type of school TABLE D - Distribution of positive skin reac- tors by length of residence and type of school. In the analysis of study areas (Part II) each table is identified by an arabic number designating the watershed. There is a detailed map of each watershed area which includes the exact location of each school with a fifth grade classroom and the schools sampled; above each school sampled is the school number, the type of school (indicated by a black star for rural and circled white star for urban school), and the rate of skin sensitivity found in each school. Perusal of these maps will bring out the focal nature of infection on the island. Discussion The present study is probably the first at- tempt to measure the prevalence of a parasitic disease in a given population based on a sta- tistical design. The findings in the study are supported by data from previous studies made on the island and reveal new epidemiologic information for watershed areas #2, #18, and #15. From the design of the study, the focal nature of the disease is brought out very sharply as evidenced from the prevalence rates in Table E.—Prevalence rates (percent) of skin reactivity for each study area for urban and rural schools combined Area Rate per 100 rural-urban schools combined Standard deviation LID vw ww we Nw EN LW NS I WR WE a le ee We Ee 15.6 36.3 31.7 9.4 34.3 23.6 26.5 22.7 11.4 9.5 15.0 16.4 18.2 16.2 11.6 6.6 6.1 9.4 5.9 5.8 13.2 16.6 4.7 8.4 3.4 5.7 6.1 18.2 8.8 6.0 11.2 1.3 3.2 4.6 2.6 3.6 6.3 4.9 2.5 2.0 1.7 2.7 2.2 3.8 4.6 3.0 0.7 1.0 1.5 0.7 1.1 2.7 2.5 1.0 3.2 1.2 1.3 1.1 5.7 1.0 1.2 0.0 Figure 5.—Combined urban and rural prevalence rates for schistosomiasis [J under 5% £] [] 5-10% 10-15% PA 15-20% N74 over 20% rural sub-areas. For control purposes this may be very significant as a source of information where the disease may be transmitted and where it is highly endemic. Students 10 to 13 years of age were tested in this study. We know from evaluation of the skin test that the test measures only about 75 percent of the positive individuals in this age group. This indicates that the overall reactivity figures obtained may be in error by a factor of 25 percent. The overall prevalence of schis- tosomiasis as obtained in this study was 12 percent which could mean that corrected for the lack of sensitivity in the terms of the test that the skin prevalence rate for the island for this age group may be approximately 15 percent. Previous studies on the prevalence of schistosomiasis were based almost entirely on stool examinations. This is a difficult, ex- pensive, and time-consuming procedure, and is limited in the amount of material that can be examined in a circumscribed period of time. On the other hand, the 10,824 children representing 396 schools on the island were skin tested within 6 months, giving a prevalence rate for a confined period of time. One in- dividual was able to skin test and one record this population. A similar study of this scope made by stool examination would require many more individuals to collect the material and ex- amine it. At least one year or longer would be needed to process all the samples by more than two individuals. In watershed areas 3, 12, 13, and 14, at the time when the students were being skin tested, stool examinations were made on one stool collected from each student. In these areas, only 25 percent (range of 19 percent to 31 percent) of the stools collected in skin reactive individuals were positive for eggs of S. mansoni. This is indicative of the difference in prevalence obtained by two diagnostic systems. To approximate the true prevalence by stool examinations, as many as five stool specimens should be collected and examined from each student. Previous fecal surveys per- formed in these areas in 1958 when most of the skin tested children should have been in first grade give the following results: area 3 - 20 percent, area 12 - 3 percent, area 13 - 7 per- cent, and area 14 - 2 percent. Two questions are relevant, First, is the difference due to the diagnostic technique? Second, is transmission occurring in an older age group than first graders? In previous studies the percentage of false positives in the skin test has been re- 13 ported to be less than 5 percent (Pellegrino, et al., 1959). In the present study, only 29 of 1,154 students tested with a negative skin test had eggs in their stools, indicating a false negative rate in these four areas of 3 percent. From data obtained by previous fecal sur- veys, in the eastern one-third of the island on a line from Loiza (area 9) to Santa Isabel (eastern edge area 15) the endemicity of schistosomiasis is high (above 20 percent). This part of the island has more rainfall and con- tains the greatest number of streams. It is also the most populous side of the island. Except for area 22 with the towns of Utuado and Jayuya, and area 28 with Mayaguez, the preva- lence of schistosomiasis in the western third of the island is uniformly low compared to the eastern third of the island. In the Ponce area, the endemicity was very low. The reason for this probably is the low humidity, lack of rain- fall, high gradient streams and lack of major irrigation systems in this area. In spite of the low endemicity in area 23, watershed sub-area #1, school #301 (Coto Laurel) 21 percent of the students were skin reactive. In area 15 just adjacent to the same watershed area, school #301 (Arus) had a prevalence of 36 percent. This indicates the focal nature of the infection in various parts of the island, es- pecially in these dry areas. A direct comparison of this study with previous studies made on the prevalence of schistosomiasis on the island cannot be readily made. Almost without exception the studies made by stool examinations were biased samples since randomly selected populations were not sampled. Investigators did not go into areas where schistosomiasis was known to be low or where it was not an acute problem. The only study that had previously attempted a statistical sample was Weller and Dammin (1945), but this study was made on adult male army recruits after induction into the Army. Since the known i11 and the physically unfit adult males were rejected prior to induction, a study made on the inductees is a selected population. The study made by White, et al., (1957) by stool examina- tions was made on elementary school children in the first to third grades. It would be dif- ficult to compare the data obtained on these young children with the data obtained on the older children in cur study because the method of sampling was not random. The areas of high endemicity obtained in previous studies were also the areas of high prevalence of skin reac- tivity obtained in this study except for areas 2, 18, and part of 15. In general, the overall prevalence of schis- tosomiasis as determined by the present study (12 percent) indicates a lower rate for the entire island than was anticipated. Our prevalence figures compare very favorably with the preva- lence figures obtained years ago by previous workers who used stool examinations. It is recognized from a number of carefully made studies that in routine stool examinations (usu- ally only one stool), depending on the age group, the true prevalence obtained may be in error by a factor of 50 percent. This is especially true for adults and may be lower for children. If this is the case, the fact that the prevalence obtained with the skin test is of the same magnitude as the prevalence obtained by stool examination may indicate a decrease in prevalence because the skin test measures at least 75 percent of the infected individuals, whereas one stool ex- amination is not as sensitive. Another explanation for this difference in prevalence rate may be the differences re- flected in obtaining a sample population dis- regarding the socio-economic factors. Pre- vious studied had a tendency to be more selective and to pick schools or groups of individuals who were probably infected or had a higher chance of being infected in endemic watersheds. Puerto Rico is in a state of transition evolving from a predominantly agricultural economy into a light industrial economy. This entails a relocation of people away from the land into urban areas. In Puerto Rico this has been facilitated by the development of rural communities called ‘‘parcelas’’. In Figure 6, distribution of these parcelas is shown and the extent to which the number of such com- munities developed in the past decade indicate the extent to which this socio-economic transi- tion is taking place. In spite of this, the preva- lence or endemicity of schistosomiasis in Puerto Rico has not changed radically. In our study we did note that in urban areas there was a higher prevalence, probably due to the influx of rural children into the urban schools. In fact, in many urban schools the students are predominantly nearby rural children who come daily to the urban schools for their education. Two examples of this are the urban school in Luquillo (area 2) with a 27 percent prevalence rate and the one in Rio Grande with a 19 percent prevalence rate where the students are predominantly rural children. In area 5 in Juncos the same situation was also found when the children’s addresses were reviewed. Two classrooms were sampled; skin prevalence rates of 61 percent and 20 percent were found. In the school with the 61 percent prevalence rate, the majority of the children lived in rural areas, and in the school with the 20 percent prevalence rate the majority of the children were urban. The growth of urban areas frequently ex- tends into endemic rural foci of schistoso- miasis. This is true for the Rio Piedras and Bayamon areas which are part of the metro- politan San Juan complex. Schistosomiasis is an international prob- lem and the socio-economic evolution of Puerto Rico will be reflected in similar developments in other parts of the world and the effect of schistosomiasis on the population will be simi- lar—infected people moving intourbanareas or Figure 6 —Rural communities in Puerto Rico. 14 e single rural communities @® expanded rural communities into non-endemic areas with their schistoso- miasis. In developing areas, as socio-economic changes take place, this process can be mirrored in what is taking place in Puerto Rico. In other words, the situation in Puerto Rico as itexists today may represent situations that will take place tomorrow in other parts of the world. The present study may have significant ap- plications for future control purposes because it presents a profile of the endemicity of the disease In various parts of the island and planning can now be made on a more intelli- gent basis due to evidence of skin reactivity in the people living in each area. For the eradication or control of any par- asitic disease, the first step is adequate epi- demiology of the disease. The present skin test study, despite its shortcomings, gives a very good profile of the relative prevalence of the disease in the 10-to-13-year-old age group dis- tributed throughout the island. It must be em- phasized that the students tested in this group were selected completely at random within each watershed area. The relative prevalence of skin sensitivity reflects the endemicity of schisto- somiasis in the area and for this reason the study is very useful for future control pro- grams, With a map of the distribution of bilharzia in rural areas and with a map of the distribution of bilharzia in urban areas plus knowledge of the epidemiology of transmission 15 within these areas, effective control and pos- sible eradication of schistosomiasis can be undertaken in the future. There is no reason why schistosomiasis should not be eliminated completely from Puerto Rico. The life cycle, life history, and ecology of the snail is well understood. We have available very effective molluscucides (chemical and biological techniques). We have field programs on the evaluation of various methods for using these molluscucides. Control programs in various study areas of the island carried on over the past decade have shown that the control of schistosomiasis can be achieved. In study areas 13 and 14, stool ex- amination of children entering grade school five or more years after the initiation of molluscociding and control of bilharziasis in that watershed showed a drop of positive stools to 5 percent from a high of 20-30 percent in that same area. This may be a reflection of the effectiveness of control in the area. With the information obtained on the skin reactivity in every major and minor watershed area on the island, evaluation to demonstrate.that schisto- somiasis can be controlled on an island-wide basis and, in time, eliminated as a public health hazard may be achieved. The data obtained on each major and minor watershed area of the island would be very useful for future control programs and are analyzed in detail in Part II of this study. = _ II. ANALYSIS OF STUDY AREAS eo Area 1 comprises three watersheds con- taining the Rios (rivers) Fajardoand Demajagua and the Quebrada (creek) Fajardo. The urban communities of Fajardo and Ceiba are found in this watershed (Map 1). The total population MAP 1, AREA NO. 1 _.--f- 000 — School Number * — Type of School 00 — % Infection SUB-AREA QUrban * Rural @® Not sampled of this area is approximately 24,000 people. The area is made up of alluvial coastal plains and low valleys, and includes part of the U.S. Navy Roosevelt Roads station. There were 18 fifth grade classrooms in this area from which 10 were selected (5 urban and 5 rural) and 217 students were skin tested. There is evidence of uniformity in the proportion of positive reactors in the rural schools between sampled classrooms but not in the urban schools (Table 1A). Combined preva- lence for both urban and rural schools was 16 percent. Except for stratum 2, rural male students were more skin reactive than rural females. In general, a high rural and low urban prevalence rate was noted (Table 1B). It pos- sibly may be significant that little opportunity is afforded for infection within the towns due to heavy pollution of the few existing streams which deters the growth of Australorbis. No large difference in the prevalence rate between the age groups tested was noted (Table 1C) and 78 percent of the urban reactors and 88 percent of the rural reactors resided for 5 or more years in the vicinity of the school (Table 1D). Table 1A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 1] Number | Number Rate Average Average Stratum School code toh per | antigen | control tested | positive 100 area area Urban: 1 YJIBLVON ,inusomionsomes wns wv sss omnes PUT owes Ts shys ons 29 2 6.9 0.7 0.5 2 YPETLAD ov orc 0600 0.5 itinn Se 8 eels 2 AEB BB 2 Hs BE DRE RIES 25 0 0.0 0.7 0.5 2 BBBTLOL crn» sve sss on m1 2 3 300s 00 rts 0 so om is sci oe 35 4 11.4 0.7 0.5 2 Y20YVOH | uicicnmunvmn sme sss vnbins omehmis vies Sis Seb ws hss 18 0 0.0 0.6 0.6 2 BION AD =. her cc cl ori 1s shin sos wins wow; edo mello of voce. 28 3 10.7 0.8 0.5 Boal = Sous vin ais cords 200 © GIG £5 5 wi 4 S00 PES vn SRE wi 135 9 % 0.7 0.5 Rural: 1 118200 .uuivomssmnrmmas sins ies ss sam 2s 05s GHEE E2043 wae 9 4 44.4 1.2 0.5 1 LUBTUOD vw onin mo mos wowons wm mmm sn ws sm 3 ow ns wm 22 8 36.4 1.2 0.6 2 1262006 ..ovswmsmusnmis mms bmssssodos esse ssmesbos wis 15 3 20.0 0.8 0.4 2 BDEDUNG 5 ce st wie res cies vse we Pe ns os es fe he orc Bm 13 5 38.5 1.4 0.8 2 LIBIVOA: vv cmos mows amen mw vow 4 4 ww moms wom 5 0m 9 & 905 © wom: 5 whe © 23 8 34.8 1.2 0.6 TOLL ; crs 000 5 tre 0 hitler re SARE en 6 ills. ie 82 28 % 1.2 0.6 Grand BovaY oo oi vo wnium mn vm s sw 0 00s ¥ iw ww gS HE BE 8 217 37 3% 1.0 0.6 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 17 Table 1B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 1] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per | male male per | female female per |urknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Uban ......oovvvune 29 2 6.9 14 1 7.1 15 1 3 - - Rural ............... 31 12 38.7 19 10 52.6 12 2 16.7 - —- Stratum 2: Urban ............... 106 7 6.6 63 6 9.5 43 1 2.3 - — Bural «oinnismasaving 51 16 31.4 28 8 28.6 23 8 34.8 - - Total ............ 217 37 ® 124 25 ® 93 12 * — - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 1C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 1] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under10years....................oonnnn. 24 6 25.0 12 0 0.0 12 6 50.0 VO Years: «crus nanawes mms ams «wm wis 5 sie sou 80 14 17.5 53 5 9.4 27 9 33.3 11 years oo... 59 8 13.6 40 3 7.5 19 5 26.3 12 VCAIS ui wn runs & wre wml is wows 6.10 $000 4.5 940 4 30 5 16.7 16 1 6.2 14 4 28.6 13yearsandover ..............c0vvuunnnn 24 4 16.7 14 0 0.0 10 4 40.0 Totads ss on vm som 5 ois 5 6 3 0008 512.5 00 5 wi 3 217 37 *¥ 135 9 x 82 28 % *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 1D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area \ [Watershed area 1] Length of Total Total Rate Number Number Rate Number Number Rate . Percent : Percent Percent residence number number per ositive urban urban per ti rural rural per iti (years) tested positive 100 posta tested positive 100 Pasiive | | sted positive 100 postive Less than 1 ..... 14 1 7:1 2.9 13 1 2:7 11.1 1 0 ® 0.0 14............. 43 4 9.3 11.8 32 1 3.1 11.1 11 3 27.3 12.0 7 SR 45 8 17.8 23.5 29 2 6.9 22.2 16 6 31.5 24.0 10:14........... 104 21 20.2 61.8 55 5 9.1 55.6 49 16 32.7 64.0 Unknown ........ 11 3 * * 6 0 * * 5 3 X * Talal. ....s vais 217 37 * 100.0 135 9 * 100.0 82 28 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 18 In watershed area 1, schistosomiasis has been endemic for a long period of time (Ferguson, 1955; Maldonado and Oliver- Gonzalez, 1958), For individuals below 15 years of age, Maldonado and Oliver-Gonzalez (1958) reported prevalence rates obtained by stool examinations from Ceiba municipality of 33 percent, 18 percent and 10 percent for 1953, 1954 and 1955, respectively. Pimentel and White (1957) reported an infection rate of 5 percent- 20 percent for this municipality. White, Pimentel and Garcia (1957) reported an infection rate of 29 percent during 1953 for Ceiba, and Weller and Dammin (1945) a rate of 21 percent. Our data indicated a rural rate of 36 percent for the Ceiba area. ° Area 2 comprises four watersheds which include the Rios Sabana, Rio Grande, Espiritu Santo, Mameyes and Herrera, and the towns of Luquillo and Rio Grande (Map 2). The area consists of rugged mountain and alluvial plain. The total population of this area is approximately 26,000 people. From the 22 fifth grade class- rooms in this area, 10 were selected (3 urban and 7 rural) and 230 students were skin tested. In one urban school in Stratum 2 (Rio Grande), two classrooms with prevalence rates of 3 percent and 32 percent were noted. In the rural schools prevalence rates from 20 percent MAP 2, AREA NO. 2 000 — School Number * — Type of School 00 — % Infection RIO GRANDE OQ Urban * Rural ® Not sampled to 61 percent were observed (Table 2A), Com- bined prevalence for both urban and rural schools was 36 percent. Males were more skin reactive than females and reactivity in rural schools was approximately two times as high as that for urban schools (Table 2B). Skin sensitivity showed a sharp increase with age and students 13 years and over were twice as skin reactive as 10-year-olds (Table 2C). Al- though 60 percent of the urban children and 76 percent of the rural students who were skin reactive had lived in the area 5 or more years, only 45 percent had lived there all of their lives. The data in table 2D indicates a great Table 2A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 2] Number | Number Rate Average Average Stratum School code “ip per | antigen | control tested | positive 100 area area Urban: 1 BERIT... ecco cin roi 7 hse ont ssn os hs Ss cs i br ie hl sets 30 8 26.7 0.8 0.5 LE TT 34 11 32.4 1.0 0.5 2 1BOTXOND. «over com mam we #3 coe 0 wom 0 es cv ss 50 8 it wh 30 1 3.3 0.7 a.5 Total Lo 94 20 * 0.8 0.5 Rural: 1 VAA2LT0 ui vvimmssnunmesmusnmanman@ss ns amos es sss 19 7 36.8 1.0 0.4 1 THAIN... cc 2 tein vom wf rs mcs se ot Bs 0 cl BRI 8 0 0s 26 12 46.2 1.2 0.5 1 ABOOBON. oii «wins mie 5 00 5 00 6 0 1 § 0 0 5 0 0 9 590 § 9° 9 20 4 20.0 0.8 0.4 2 AB9ZLIG. vo hv von como scm wm ims 50 6 ok 50 58 9 8 0 60 5 BE 8 9 6 28 13 46.4 1.0 0.4 2 LB ODDIE ris 5 x 5 0 ws cv rh tml a of mi ot of nnn 3 cel 16 8 50.0 1.2 0.5 2 ABODNND, isin mim 2 10 3 000 00 5600 9 5 005 50 6% 6 6 W508 P03 0 B08 0 8 HE 9 2 22.2 0.7 0.5 2 IBD2U0B ov vvvin sms nmnam rs wnn rome emns mn wns nn a 18 11 61.1 1.5 0.5 TIAL «ois vs in mst As STFS MEF RE SSE EE RES BRS RHEE WES BT 136 57 % 1.0 0.5 Gran@ total «vm mas mas sor EERE EE PE YR ER RS EE EE 230 7 * 1.0 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 19 Table 2B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 2] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban ..vsvssnmsnwass 30 8 26.7 23 5 21.7 7 3 Li - - Rural .......c.n..... 65 23 35.4 38 18 47.4 27 5 18.5 - - Stratum 2: Urhahi ous ome's nviammsss 64 12 18.8 28 8 28.6 36 4 11.1 - - Rural ............... 71 34 47.9 45 26 57.8 26 8 30.8 - - Taral ..cnsdiisniines 230 7 % 134 57 * 96 20 *% — - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 2C.—Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 2] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested “positive 100 Under 10years .............covnvnunnnnnns 7 2 * 3 0 * 4 2 * 10 years «ions omsns comin sn soms sme wes ve 80 22 27:5 37 4 10.8 43 18 41.9 11 years ........cvvvnvneneuunnnnnnnnnnns 68 15 221 34 8 235 34 7 206 AD YEAES orn simmer nin nswin smn sms am we soe 45 21 46.7 14 6 429 31 15 48.4 13 VEATS ANA VEE oo vu vivo mins ims vnc 5 550m 1 sm 29 16 55.2 6 2 * 23 14 60.9 Age unknown ........... 1 i * 0 0 * 1 1 ® ROTAL ol rr 5 ie iis wd sol i 5 woof en 230 77 * 94 20 * 136 57 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 2D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 2] Length of Total Total Rate ’ Number Number Rate Number Number Rate residence number number per Percent rb b Parcent rural rural r Percent he p positive Bay oon pot positive la wo pe positive (years) tested positive 100 tested positive 100 tested positive 100 Less than1l ..... 14 7 50.0 9.3 9 4 * 20.0 5 3 * 5.5 14. osviinniiuns 46 14 30.4 18.7 26 4 15.4 20.0 20 10 50.0 18.2 BY ahs ie nd 60 20 33.3 26.7 20 3 15.0 15.0 40 17 42.5 30.9 10-04 .onivs inns 105 34 32.4 45.3 39 9 23.1 45.0 66 25 37.9 45.5 Unknown ........ 5 2 * % 0 0 * wt 5 2 ® * Total... cues auss 230 7 * 100.0 94 20 * 100.0 136 57 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 20 deal of movement for the sampled population. Although past records indicate that schisto- somiasis has not been strongly endemic in these areas for a long period of time (Ferguson, 1955), the data indicates that it is now entrenched in both urban and rural areas, Weller and Dammin (1945) reported for Luquillo a positive schistosomiasis rate of 11 percent and for Rio Grande 8 percent. The relatively high prevalence of schistosomiasis found in our study was unexpected. In Fig. 6 the location of ‘‘parcelas’, or low cost rural communities, is shown. By coincidence almost all of the schools sampled were located within parcelas. Recent examination of several streams in the area resulted in the discovery of A. glabratus shedding cercariae of S. mansoni. ® Area 3 comprises two watersheds con- taining the Rios Daguao, Santiago, Cubuy, Icacos and Blanco, and the town of Naguabo (Map 3). The area has both mountainous and coastal plain sections. The total population is approxi- mately 21,000 people. There were 17 fifth grade classrooms in this area from which 8 were selected (2 urban and 6 rural and 220 students were skin tested. A high prevalence of skin reactivity was obtained in both urban and rural schools (Table 3A). Combined prevalence for both urban and MAP 3, AREA NO. 3 000 — School Number * — Type of School 00 — % Infection 2 1 2.4 301 ° ¥ . 0 1 ° 2 - 02 ° } * NAGUABO © Urban * Rural ® Not sampled rural schools was 32 percent. Males were much more skin reactive than females and in stratum 2, urban students were more sensitive than rural ones (Table 3B). Age distribution indicated higher prevalence rates in the 13-year group but uniformity among the remaining age groups (Table 3C). In both urban and rural schools 76 percent of the skin reactors had resided in the area all of their lives (Table 3D). Schistosomiasis has been endemic in some of these areas for a long period of time (Ferguson, 1955) and transmission at present appears to be both in rural and urban areas. Weller and Dammin (1945) reported a prevalence rate of 8 percent for Naguabo. Our findings compared to general historic data (Ferguson Table 3A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 3] Number | Number Rate Average Average Stratum School code i per | antigen | control tested | positive 100 area area Urban: 2 BBE VODET vin cit 0.0m smn +6 se cs 5 sw ok cn vo, on sh it ve 37 17 45.9 1.2 0.4 2 IBRTVODEN vn sms pies 5 ER SI EB ES 0% PRE BES SEES 41 8 19.5 0.8 9.5 BOE 1 ore ors nd in 0 rt of he Bo e's a SPI 0 woe B10 78 25 %* 1.0 0.5 Rural: 1 ETN cr 1. io sv oh th sh id 4 nor He he tes fs vats ol ie 20 36 18 50.0 1.3 0.5 1 FLB2T0B viv v5 swims moms own a wg 8 ww EB ERB EE EE 18 5 27.8 0.8 0.4 2 IBIZL00. vsti smash moa a 9 HAS HERR EAE 0 BES EE REY 30 3 10.0 0.6 0.3 2 NSE Hs, cialis: o/s widest on wei scm Sst se bo oe 3,20 do sss Ws 7 1 14.3 0.7 0.5 2 ABO, im co ie 5 00 ims 9 0S ER EB PE EE 4 28 12 42.9 1.2 0.4 2 EBLTULB ce vv vo orm ow ows wn mm m0 9 ams 0 cm arm co 900 cn 23 7 30.4 0.9 0.4 Total «o.oo 142 46 * 1.2 0.4 Grand total ............ LL. 220 71 %* 1.2 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 21 Table 3B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 3] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urhan sonsswrsnn svn: - - - - - - - — —- — — BUral ic vin cnn mins 54 23 42.6 23 14 60.9 31 9 29.0 - — Stratum 2: Urban .............. 78 25 82.1 45 18 40.0 33 7 2.2 —- - Rural ..crvmrennsnns 88 23 26.1 46 15 32.6 42 8 19.0 - — Tota) ov sinnsnis » muti 220 71 * 114 47 * 106 24 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 3C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 3] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under \0 years.» viumnsnn rows mer masamepmas 14 3 21.4 2 1 ¥ 12 2 167 10years .......... iii 65 19 29.2 27 8 29.6 38 11 28.9 ll years o.oo comrspesnvsrmiimasn sams mss 65 21 32.3 20 6 30.0 45 15 33.3 DDIVBATE ou uns 55 sts set oe bb mc oi 3 ld #0 vii 0 44 13 29.5 14 4 28.6 30 9 30.0 13 years and over .................. a... 32 15 46.9 15 6 40.0 17 9 529 TOUR: 25.5 00 550 Bi & ts bs oo 5 6 wir 220 71 ¥ 78 25 *¥ 142 46 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 3D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 3] Length of Total Total Rate Number Number Rate Number Number Rate ’ Percent Percent Percent residence number number per ti urban urban per ti rural rural per tive (years) tested positive 100 POSTIVE | tested positive 100 POSTIVE 1 tested positive 100 Rosi Less than 1 ..... 5 2 % 2.8 4 2 * 8.0 1 0 * 0.0 1-4... 11 4 36.4 5.6 4 1 *¥ 4.0 7 3 * 6.5 BD vusandamannns 31 11 355 15.5 10 3 30.0 12.0 21 8 38.1 17.4 10:14. ....c00 vn 173 54 31.2 76.1 60 19 31.7 76.0 113 35 31.0 76.1 Unknown ........ 0 0 * * 0 0 ¥ * 0 0 % %* Towal.......cc- 220 71 * 100.0 78 25 * 100.0 142 46 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 22 1955; Maldonado and Oliver-Gonzalez, 1958) indicate a much higher prevalence rate (32 per- cent), It should be noted that endemic streams originating in areas 1 and 3 flow through U.S. Naval Station, Roosevelt Roads, where bilharzia control by a biological technique is a matter of concern (Ritchie, Jachowski and Ferguson, 1960). eo Area 4 is part of the Lolza River water- shed containing communities associated with the Rios Cubuy, Canovanas, Canovanillas, and part of Rio Grande De Loiza and the Quebradas Grande and Maracuta. The area includes the urban areas of Loiza, Trujillo Alto, and Caro- lina (Map 4). The study area contains mostly mountainous land cut by long narrow rivers. The coastal strip is devoted to sugar cane growth. The total population of this area is approxi- mately 52,000 people. There were 39 fifth grade classrooms in this area from which 11 were selected (4 urban and 7 rural) and 309 students were skin tested. In this watershed, reactivity was very focalized and varied greatly between schools. In rural schools Stratum 3, the average preva- lence was 5 percent, increasing to 14 percent in sub-area 2 and 18 percent in sub-area 1, with a combined average of 9 percent (Table 4A). MAP 4, AREA NO. 4 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled Combined prevalence for both urban and rural schools was 9 percent. Except for one rural school, males were more skin reactive than females and urban schools had equal or higher prevalence rates than the rural schools (Table 4B). In the 13 year and older age group, there was a distinct increase in prevalence rates (Table 4C). In urban schools 46 percent of the reactors have resided in the area 10 or more years; whereas in rural schools 79 percent of the reactors were life-long residents (Table 4D). Table 4A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 4] Number | Number Rate Average Average Stratum School code ny per | antigen | control tested | positive 100 area area Urban: 1 B70LIO0L vsmnsmmenmunns ames sms pws swiss yy we sa wanes ens 35 3 8.6 0.6 0.4 2 BABLIOT-L cr oon iso i 0 aie ni inl 59 si + ot 4 ib 4 ck ot 3 26 2 7.3 0.7 0.5 2 LIBLION-2 .icivrevnsnmosmesmmssmasmus mas nmann ss wus ame 28 4 14.3 0.8 0.5 3 LABANOL 5: + si + mir 7 i 20k 00 & ti 003 3 00% BRD BR RABE BRA Fd 30 3 10.0 0.7 0.5 TOraL.... sinew 1 mins ins 3 me 2 dvs min y pms mom $0 0 wen 4 nies 2 oo wi 2 119 12 * 0.7 0.5 Rural: 1 Y702UXD impr ome man nn npg soins 3 uno ole § IH ¥ 00S A905 £00 4 00 # 15 5 33.3 0.9 0.5 1 A702302 ovis vss mnesnnmns sna smn mms sas ses annnnns sna 25 2 8.0 0.7 0.5 2 BIB2ULY vss mmemunn mms ois mvs 30s 3 in 1 win 6 Sin 0 ime 0 i 8 ou 4 20 4 20.0 0.8 0.5 2 VEBBUD0) i. + ov vin mis 0 55 Sh i 2 200 3 B05 ot ¥ ll B10 8 0 # A 8 23 2 8.7 0.6 0.5 3 1432103 Lovie 24 4 16.7 0.9 0.6 3 TAB2U08 nen snes ams mys wipes mes mins pe a8 sma suss nis 47 1 21 0.6 0.5 3 RABOB0D sinh wet 4 Bir $k F hak © 20 RI BRS ch £0 5000 K So a 36 0 0.0 0.7 0.6 Total osama vmtsms roms wns aes bin s Bs amas ais ar 2 03 1 350+ 190 18 ¥* 0.8 0.5 Grad ABEL ots fies as snp 0 i tiie oi we i AT ey mal 309 30 % 0.7 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 23 Table 4B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 4] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: TIEBAGN Locsin mim eat adn 35 3 8.6 21 3 14.3 14 0 0.0 - - Raral .:snmsresemssns 40 7 17.5 19 2 10.5 21 5 23.8 — - Stratum 2: Urban uous ims m sens 54 6 11.1 29 6 20.7 25 0 0.0 - - Rafal ii os be soe 43 6 14.0 23 5 21.7 20 1 5.0 — —- Stratum 3: Urban. . cussnssnmsmme 30 3 10.0 16 2 12.5 14 1 7.1 — - Rural, oni suns 107 5 4.7 56 4 7.1 51 1 2.0 - - Total c:svesvvsnns 309 30 * 164 22 145 8 ¥ - wi *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 4C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 4] Total Total Rate number number per tested positive 100 Number Number Rate urban urban per tested positive 100 Number Number Rate rural rural per tested positive 100 Under 10 years 10 years 11 years 12 years 13 years and over Age unknown BH WR SE eR AR RE BW | 17 0 0.0 1 0 * 16 0 0.0 108 7 6.5 57 4 7.0 51 3 5.9 81 8 9.9 26 2 77 55 6 10.9 52 4 7.7 19 1 5.3 33 3 9.1 50 11 22.0 15 5 33.3 35 6 17.1] 0 * 1 0 * 0 0 * 309 30 * 119 12 * 190 18 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 4D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 4] Length of Total Total Rate Number Number Rate Number Number Rate residence number number per Pitesit urban urban per Patogns rural ~~ rural per Percen (years) tested positive 100 POSIIVE | | ested positive 100 positive | ested positive 100 Positive Less than ..... 13 2 15.4 8.0 11 2 18.2 18.2 2 0 * 0.0 14... .......... 45 4 8.9 16.0 30 1 33 91 15 3 20.0 21.4 BD snc rnmrenrane 56 3 5.4 12.0 28 3 10.7 27.3 28 0 0.0 0.0 10-14... cixidais 171 16 9.4 64.0 43 5 11.6 45.5 128 11 8.6 78.6 Unknown ........ 24 5 * * 7 1 * * 17 4 ¥ Je Total. ...« won wins 309 30 * 100.0 119 12 * 100.0 190 18 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 24 Schistosomiasis was thought to be lightly endemic in these areas for a long period of time (Ferguson, 1955). Weller and Dammin (1945) obtained a prevalence in Loiza of 7 percent, Trujillo Alto of 7 percent, and Carolina of 1 percent; while White, Pimentel and Garcia (1957) obtained a prevalence in Carolina of 4 percent, Both studies were based on ex- amination of single stools for S. mansoni ova. The present data indicate that there is a shift of population of rural families moving into urban areas which may account for some of the skin reactivity noted in urban schools. ® Area 5 is also part of the Rio Grande de Loiza watershed containing communities as- sociated with the Rios Valanciano, Gurabo, and part of the Rio Grande de Loiza, plus the towns of Juncos, Gurabo, and Las Piedras (Map 5). The study area is comprised mostly of alluviated plains crossed by numerous small streams. The total population of this area is approximately 52,000 people. There were 39 fifth grade classrooms in this area from which 12 were selected (5 urban and 7 rural) and 375 students were skin tested. In this watershed high prevalence rates were obtained in both urban and rural schools (Table 5A). The average urban school preva- MAP 5, AREA NO. 5 000 —: School Number * — Type of School 00 — % Infection O Urban * Rural ® Not sampled lence rate was 37 percent and the rural rate was 32 percent, Combined prevalence for both urban and rural schools was 34 percent. Males were more reactive than females, and in stra- tum 1 students in urban schools revealed a higher skin sensitivity than in rural schools.In stratum 3 the trend was reversed (Table 5B). Evidence of homogeneity in skin reactivity in the 10-12-year group witha marked increase in prevalence in the 13-year and over group was shown (Table 5C). In urban schools, 73 percent and in rural schools 81 percent of the reactors have resided in the area for ten or more years (Table 5D). Table 5A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 5] i Number | Number ] Rate Average Average Stratum School code Se per | antigen | control tested | positive 100 area area Urban: 1 ABBANBT cores cm on 51 1 5 wine ns +1) sie bo ris of scans ss il of oe bs 0 oes © td nd 41 8 19.5 0.8 0.4 1 IBBLNOD ovu ims in vio wiv v sim o 4% #8 605 5 510) £5 B05 § B08 850 830 vm sw 28 17 60.7 1.3 0.3 1 1421100) . cv trv rr m rman Sins as Aa Ss RAED FED EGE HE 41 13 31.7 1.0 0.4 1 NANTON + 7 5:01 wrest 5-001 6 soa nnn 5 od i ed eis sas i ce cr) oe 43 24 55.8 1.2 0.4 3 1301100 ic cvnmmomenuusMmus Mor aMERW Ean s #i0 8h AB TYE ps 35 8 22.9 0.8 0.4 TROEAL v5 1 5 nRI0 § MIE CIF BI 2 7 3 G9 Eee 000 ge: wes ol ass tro sh 188 70 ¥ 1.0 0.4 Rural: 1 138 18 tira mn ns man Gus PY PEE Fy BEES EET SW Ww 25 6 24.0 0.8 0.4 1 1382300. ...ovicrnmen mbm HE Eh BRAS MEE BR MR ARE & f 24 2 8.3 0.6 0.5 2 ADBDNNT. 2 igen woos wiv wit 55 avantn owes ot slp sod ol bo ose vale ols vb lO 26 10 38.5 1.2 0.4 2 YAPTTU6 civ soins Sm sR EE El Sil S15 5 IE ¥ 3 05 § 96S HUT 000% 33 14 42.4 1.1 0.4 3 1312108 27 5 18.5 0.8 0.4 3 IB12V00 is ivrmes muss aism spies iE enmagbiss@ismusmysy we 43 20 46.5 1.1 0.5 3 TBAZTOD nv cs vi dine rms v0 le tn die ion 3 Bd 0 00040 0 0 0 8 nl 0 8 9 1 11.1 0.8 0.4 Tall) 7 wns dir vs m0 Tere? i 2 0 6 fv Tn weighs wie send 92 40 tse 4 ein 187 58 * 0.9 0.4 CTEREIEOVAL ov. 0 wcrc wid of owe 20 hss el hin) ts WE 0 3 375 128 % 1.0 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 25 Table 5B.=Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 5] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban. «ou omen 00m ss 153 62 40.5 78 43 55.1 75 19 253 - — Rural .............. 49 8 16.3 16 3 18.8 33 5 15.2 - — Stratum 2: Biba. «ov sonin minim nmi « - —- - - - — - - — - Rural .cwimecemmens: 59 24 40.7 28 14 50.0 31 10 32.3 — - Stratum 3: Urban .............. 35 8 229 23 6 26.1 12 2 16.7 - - Rural es envemmsone 79 26 32.9 37 15 40.5 42 11 26.2 — - i 7 | SEP. 375 128 * 182 81 * 193 47 - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table SC.—-Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 5] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10°years . ; ova sss vm avn sans 3 £4 4 50 4 0 % 2 0 * 2 0 we 10years ....... iii 83 20 24.1 31 11 35.5 52 9 17.3 1) VEBIS: wien ims s mind win 300 hans b Sin § BREE Rs BN 136 44 32.4 76 27 35.5 60 17 28.3 V2 VBHTR ac + Led 2 semen tant nko sicalis rose eo sie dere 83 24 28.9 43 12 27.9 40 12 30.0 13 years and OVEr .. ui suis 2mm sms prod we a 15 69 40 58.0 36 20 55.6 33 20 60.6 TDOLEL 1. ors 2 sen ames ans iss sins 1 ig) wh shes his 375 128 % 188 70 * 187 58 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 5D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 5] Length of Total Total Rate p . Number Number Rate p " Number Number Rate Devcon residence number number per shoes urban urban per Sr rural rural per ositive (years) tested positive 100 POSTIVE | tested positive 100 POSIEIVE | tested positive 100 P Less thanl ..... 18 1 5.6 0.8 10 0 0.0 0.0 8 1 * 1.7 Bnd i ms 50 20 40.0 15.6 35 17 48.6 24.3 15 3 20.0 5.2 I 39 9 23.1 7.0 14 2 14.3 2.9 25 7 28.0 12.1 10-14 ........... 262 98 37.4 76.6 124 51 41.1 729 138 47 34.1 81.0 Unknown . vs 5 + 6 0 * * 5 0 % ® 1 0 x 3 Total .......... 375 128 %* 100.0 188 70 * 100.0 187 58 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 26 Records indicate that schistosomiasis was lightly endemic in these areas for along period of time (Ferguson, 1955). Concerning fecal test data, White, Pimentel and Garcia (1957) re- ported a prevalence rate of 20 percent in Juncos and 6 percent in Gurabo. Weller and Dammin (1945) reported 19 percent and 31 percent for these two communities. There is current indication that considerable trans- mission has taken place in this watershed study area as shown by the overall positive test average of 34 percent. ® Area 6 comprises two watersheds with the Rios Anton Ruiz and Humacao and Quebrada Mariana plus the towns of Humacao (Map 6). MAP 6, AREA NO. 6 000 — School Number * — Type of School 00 — % Infection Aor 19813 o ° HUMACAO 2 © Urban * Rural ® Not sampled The generally flat alluvial plain is used for growing sugar cane. The total population of this area is approximately 32,000 people. There were 27 fifth grade classrooms in this area from which 10 were selected (4 urban and 6 rural) and 331 students were skin tested. In the schools of Humacao, prevalence rates from 14 percent to 25 percent with an average of 18 percent were obtained. In rural schools prevalence rates were very focal, ranging from 3 percent to 63 percent, Combined prevalence for both urban and rural schools was 24 percent. High skin reactivity in both urban and rural schools was noted (Table 6B) with very little change in the total age groups (Table 6C). Eval- uations on the length of residence and preva- lence of skin sensitivity indicate that there is a great deal of movement into urban areas, while in rural schools 90 percent of the students resided in the area 5 or more years (Table 6D). Schistosomiasis has long been known in this area (Ferguson, 1955) and Weller and Dammin (1945) reported a prevalence rate of 17 percent in Humacao. We found a rate of 28 percent, ® Area 7 comprises four watersheds con- taining the Rios Ingenio, Guayanes, Limones Table 6A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 6] Number | Number Rate Average Average Stratum School code poi per | antigen | control tested | positive 100 area area Urban: 2 BALTO2=L. & vii www ov ws wins www wows an # wins 0 Bik 3008 SME IDB ESTED 35 5 14.3 0.6 0.4 2 3A T10232 . rs td aw vou § TIER Tre wa £ oa Siow Wins be ert ialieretel iors 32 8 25.0 0.8 0.5 2 BANNOB-L . oo 5 wii 5545 95 Bow 0 E5500 RA EROTE £0 6 400 RE 6 Bi 3 39 6 15.4 1.2 0.6 2 EBA T0322 , ors yc wv ww ww wins ios ww nes 8 rn nin in such el 5.0005 © So #0 43 8 18.6 1.0 0.5 Total ovens mas RETEmes wos HEI AW FFP es WES POT Sw dy 149 27 % 0.9 0.5 Rural: l TBAT ov «br ww ov mime we wow cn: & sh Bt 8 HE BW 4 EE 40 1 2.5 0.8 0.6 1 0 rs Tis wr mir gsi SI es, A Tk: es of lil. lle or HI 30 19 63.3 11 0.5 2 AB42106. . oi ovis 8 a BES 6 9 BS B04 BI WE © BINS BBE 25 7 28.0 1.1 0.6 2 1330100 2 ts ve vrs me rn ei fr on Nd jae: se Sng swell weer Smee 37 16 43.2 1.0 0.4 2 TA2UAD. vermis ss nT IRE PIE I PRT PR CRE ME SH 23 3 13.0 0.7 0.4 2 YA S000 ir 15 0 fri vpn lind © wong on hoes asl ho BRR SIRS ARR 27 3 11.1 0.9 0.5 TORRY vd nv mikon ed os & of B50 000 © 008) 3 Wie HB 9 0 8 Bie Wi 182 49 ® 0.9 0.5 Grand BLA) « ; Te 5500 Sluis $1 FRrn ama Sl wre: LR BAe To 331 76 %* 0.9 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 27 Table 6B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 6] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: UEBAR voi cine s sisisigasin — - - —- - —- —- - — - Rural voveews sos snnes 70 20 28.6 33 15 45.5 37 5 13.5 —- - Stratum 2: Urban .............. 149 27 18.1 76 19 25.0 73 8 11.0 = - Rural «usinormsinis 112 290 25.9 49 16 32.7 63 13 20.6 —- - Total ::cueunennss 331 76 ¥ 158 50 * 173 26 - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 6C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 6] Total Total Rate number number per tested positive 100 Number Number Rate urban urban per tested positive 100 Number Number Rate per tested positive 100 rural rural Under 10years ................ccvuuunn.. 18 1 5.6 12 0 0.0 6 1 * YO YORE: wr suv 4 4 £ Bt 200k £ Bn 5% 1 bh Wim 4 wie wana 131 28 21.4 71 10 14.1 60 18 30.0 VL Years ....cosmssamesmsnusvms smesnssmnss 89 21 23.6 28 9 321 61 12 19.7 ADIYOALS iv ocvas vinnie sms ams ainn mn smins sions 63 18 28.6 23 6 26.1 40 12 30.0 13 years and over ....................innn 29 7 24.1 15 2 133 14 5 35.7 Age unknown ....iniismismisnis nesses 1 1 * 0 0 %* 1 1 % Totalma., ot vu sons sini porn dints sie 331 76 * 149 27 ¥ 182 49 % *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 6D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 6] Length of Total Total Rate Number Number Rate Number Number Rate residence number number per Percent urban urban per Percent rural rural per Porcent (years) tested positive 100 POSItVE | ested positive 100 positive | | cted itive 100 Positive positive Less thanl ..... 19 1 5.3 1.3 12 1 8.3 3.7 7 0 * 0.0 LE 72 15 20.8 19.7 49 10 20.4 37.0 23 5 21.7 10.2 2 64 13 20.3 17.1 33 3 9.1 11.) 31 10 323 20.4 10-14... 0s cnns vn 171 47 27.5 61.8 51 13 25.5 48.1 120 34 28.3 69.4 Unknown ........ 5 0 * * 4 0 * * 1 0 * * Total. sr00: 50 331 76 * 100.0 149 27 * 100.0 182 49 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 28 Maunabo, and Cano de Santiago plus the towns of Maunabo and Yabucoa (Map 7). The area con- MAP 7, AREA NO. 7 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled tains mostly rolling hills intersected with ex- tensions of coastal alluvial plains. The total population of this area is approximately 45,000 people. There were 44 fifth grade classrooms in this area from which 11 were selected (4 urban and 7 rural) and 334 students were skin tested. Prevalence rates were high inurban schools (28 percent) and focal in some rural schools (Table 7A), ranging from 6 to 42 percent with an average rural school prevalence of 26 per- cent. Combined prevalence for both urban and rural schools was 27 percent. The proportion of male and female reactors in urban and rural schools in sub-area 1 was equal. In stratum 2, male students in urban schools showed higher percentages of infection than in rural schools. Male and female students in stratum 3 and 4 were equally reactive (Table 7B). In the total population tested there was a sharp increase in skin sensitivity between the 11 and 12 year olds noted (Table 7C). In urban schools only 19 percent of the reactors resided in the area 10 or more years whereas 76 percent of the rural students who were skin reactive resided in the area for that length of time (Table 7D). Schistosomiasis has been moderately en- demic in these areas for the period of record (Ferguson, 1955). Weller and Dammin (1945) reported for Maunabo a positive schistosomiasis rate of 17 percent based on fecal testing; a rate of 21 percent was found in our study. Their study showed 7 percent for Yabucoa and ours 25 percent. We also showed that active trans- port of students into this urban area was taking place. eo Area 8 is part of the Rio Grande de Loiza River watershed including the Canas, Bairoa, Table 7A.—Distribution of positive skin reactors by individual sample classrooms (Watershed area 7] Number | Number Rate Average Average Stratum School code tt per | antigen | control tested | positive 100 area area Urban: 1 TNO) os nssniivmrrmesma sams mms MEINE SHU? PR LNW 200 25 3 12.0 0.7 0.5 1 4711002... evn vines sama smn amma smn rm sone vend 28 9 32] 1.0 0.5 2 ETOYTOLL ui sim vo mas sma dims a @ 08 wus wn v wow we secs 's wim w shows eo 35 9 25.7 0.9 0.5 2 YTOVYOL-D... co oo 5 5505 20 700 £5 5 53 58 5 5Y6 & 0:01 4 & 900 500 4 900» S09 35 13 37.1 1.0 0.4 Tolad sues ivvomesrmnammspmns may wiv mms om ss wns md dw «oi 123 34 ¥ 0.9 0.5 Rural: 1 VATIVON oo om vnmos won mms mes ® as 6 8 WIR 0 HER 5 WW 5 300 4 4H © $1000 18 1 5.6 0.7 0.5 1 BATZLOB .... coo mine 5 ves i nn wos 8 wish 0 cs: 0 om 0 60 008 $02 $003 12 4 333 0.8 0.5 2 ATOBVDO avin i nin sim n 5rn wm 200» iH 8 wow wim = woke amon ¥ sees 0 ri 43 13 30.2 0.9 0.5 2 XT62B07 eosin inman mes mss hm 800 £208 & WEES E500 SSF 3 4 2 35 4 11.4 0.7 0.5 3 1762105 Lotta 26 2 7.7 0.7 0.5 3 YTODBOZD ... o.oo 5 £ 5.5055 50 4 55 + 3008 5000 £600 F T0000 ¢ 30 0 34081 5 34 12 35.3 1.0 0.5 4 USATVUD os oti 2 e's ot fiom 3 ima of srablconic 3 ss sme # ws bandh ie Senet 43 18 41.9 1.2 0.5 OLB .. . cvs 50s 5 5c 3 Tord 5015 3 0 £0000 4 3 EE 500 0 0 Bw £90k wR 211 54 * 0.9 0.5 GB Toba; vor rns me 5 Top asin ial vy vie wast as. dw rs el 334 88 * 0.9 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 29 Table 7B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 7] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban : ves sabn tans wn 53 12 22.6 24 4 16.7 29 8 226 - - Rural. ... corse ims os 30 5 187 17 3 17.6 13 2 154 - - Stratum 2 Urban ...vvsvvsvinson 70 22 314 34 12 35.3 36 10 27.8 - — Rural csimasisemass 78 17 21.8 46 12 26.1 32 5 15.6 - — Stratum 3 than «cum somramsss - —- — - - — - —- - - - REFBL oie eivin in wos sotiarns 60 14 23.3 35 8 22.9 25 6 24.0 - - Stratum 4 WIEBE ross 204 ote initio - - - - — — - —_ - — - Rutols' wv. crveswssninien 43 18 41.9 20 8 40.0 23 10 43.5 - - Total ..oivmernsss 334 88 * 176 47 * 158 41 ¥ - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 7C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 7] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ................cooovnun.... 15 3 20.0 6 2 ¥ 9 1 ¥ AO YAS: v5 5 niors 5ws 5.0m 3 Bibs 0 4 0) $55 450 4 € Hk 130 29 22.3 58 17 29.3 72 12 16.7 LL YEAS ....c. vovis im ovr iin wirm x vm inns feiss wv ies 90 18 20.0 29 6 20.7 61 12 19.7 A YEAS. oinsuin sow iv wim oom oe 4 6 on & Wel AAR 49 19 38.8 20 6 30.0 29 13 44.8 13 years and Over .......uvuneuornnineom sn 49 19 38.8 2 * 40 16 40.0 Age unknown ............... lL 1 0 w 1 0 ¥ 0 0 % TBORAY 5s simainins ost ik Eri remes » iin fo wl ive 334 88 % 123 34 oe 211 54 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 7D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 7] tugs) of Tosa! is Rate Percent Nadie pg Rate Percent Bn Rushes fake Percent residence number number per positive urban urban per positive rura rural p souitive (years) tested positive 100 tested positive 100 tested positive 100 Less than1 ..... 13 3 23. 3.5 9 3 * 9.4 4 0 *¥ 0.0 Yall orien wine ie 56 19 33.9 22.4 30 12 40.0 37.5 26 7 26.9 13.2 BoD ws nin hams wd 63 17 27.0 20.0 43 1n 25.6 34.4 20 6 30.0 11.3 10-14 ........... 196 46 23.5 54.1 38 6 15.8 18.8 158 40 295.3 75.5 Unknown ........ 6 3 * se 3 2 * * 3 1 % * Total. ....cov via 334 88 % 100.0 123 34 * 100.0 211 54 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 30 Caguitas, Turabo, Cayaguas, plus the towns of Aguas Buenas, Caguas, and San Lorenzo (Map 8). The study area is mostly mountainous but MAP 8, AREA NO. 8 | AGUAS BUENAS 000 — School Number * — Type of School 00 — % Infection OUrban * Rural ® Not sampled has considerable alluvial plains in the Caguas Valley. The total population of this area is approximately 101,000 people. There were 75 fifth grade classrooms in this area from which 14 were chosen (6 urban, 8 rural) and 437 students were skin tested. Prevalence rates obtained in this study were relatively high for urban (23 percent) and rural (23 percent) schools (Table 8A). Combined prevalence for both urban and rural schools was 23 percent. In two of the three strata preva- lence rates in urban males were higher than in rural male students. In stratum 3 the prevalence rates in rural students reversed (Table 8B). Skin reactivity increased with age in males in urban schools. There is a general trend for higher prevalence of infection in older children (Table 8C). Length of residence data show that in urban schools 47 percent and in rural schools 43 percent of the reactors resided for 10 or more years in the area, indicating an apparent influx of infected students (Table 8D). Area 8 is a well recognized schistosomia- sis focus (Ferguson, 1955). Weller and Dammin (1945) reported a prevalence rate of 30 percent in Aguas Buenas, 11 percent in San Lorenzo, and 26 percent in Caguas. On the same test basis, White, Pimentel and Garcia (1957) re- ported infection rates in Caguas of 24 percent and 35 percent for females and males, re- Table 8A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 8] Nunber | Nowber Rate Average Average Stratum School code op per | antigen | control tested | positive 100 area area Urban: 1 JBBVVOL 5: 55 ie om 5 win 5.000 + BRT HRE #900 2 400 1 $08 4.9006 4 100 4 405 ¥ Biwi 40 14 35.0 0.9 0.5 2 TUBULIN os niet ur 2h 4 ite as ie 0 412 0 li OR a8 4 33 11 33.3 1.0 0.5 2 BABAIAOL ; oss mins ovr vss 01 500 297% £ wT yo 8 0.95% 8 950 4 000 $05 0 31 6 194 0.8 0.4 2 VUBYVOB ois ois wits ama ois #55454 bok 5 BEE 5 5 58 05 R551 5007 § 315 5 Bk 40 6 15.0 0.8 0.3 2 Bia by 4 rc ey i meen ele os ion Sy 0 39 9 23.1 0.9 0.4 3 AOQIDO) .ooinvvnnvnmormons somes wma aes ois ves ois ov $00 36 4 11.1 0.7 0.5 MOBERL. ods ii gon vt Fg Br eT vale a Wiens wi aml oi EE 219 50 * 0.9 0.4 Rural: 1 652106 10s uv 5 vv 5 ww vam v pwns whim wins 300g $v 2 prs hens 8 oy oo 25 6 24.0 0.8 0.5 1 YBODVEB: «co sii ok 2 5050 ed tn, rod 310 Rie Hh i 8 BL 0 rt ol 30 10 33.3 1.0 0.4 1 VO BY is vi rn ree wn i £ wn WL SO EL OE Le 5 a by 32 5 15.6 0.8 0.4 2 AVBAUYL vos nim v9 52 5003 55 2 3002 RHETT 56 3 5505 WF ARTE F308 5 od 22 2 9.1 0.6 0.3 2 AIB2187 .orvrinr nmr arm sawn mn ys nn 29 8 27.6 0.9 0.4 2 JAB2203. ,vcomsemrsmuvamponwss vias abs smnsivs sess sm sen 27 3 na 0.7 0.4 3 TUBDNDD |. vcvimusimen imum s hums sod binds bons 088 4 50004 Buk 8 00 22 9 40.9 1d 0.5 3 IBA0L is vavvamsamsnnsomus mer ymes mesa senns muy putyn 31 6 19.4 0.9 0.4 EIEN 4a 00 7 ih touts onic wih SE 0: vse Ad HY oir 218 49 * 0.9 0.4 Grand Botal ... oo om 0m + 00 4 1 5s £500 34 0 9 8 4 5 5 00 8 908 5 98 437 99 * 0.9 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 31 Table 8B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 8] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per [unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: DAR + wos iscnr # wuss in 40 14 35.0 22 11 50.0 18 3 16.7 - — Rural ows sv smn es 87 21 24.1 42 11 26.2 45 10 22.2 — - Stratum 2: Urban «seme ews smn eve 143 32 224 66 23 34.8 77 9 11.7 - - Rural ows sins smaswa 78 13 16.7 42 8 19.0 36 5 13.9 _- - Stratum 3: Urban cows: mmssms ssn 36 4 11.1 20 4 20.0 16 0 0.0 —- - Rural Se csc ie cine 53 15 28.3 24 9 37.5 29 6 20.7 —- - Total ws oon vom 5 sine 437 99 * 216 66 ¥ 221 33 _- - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 8C.—Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 8] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years soos ses mmrans snes eras pe 12 2 16.7 7 0 * 5 2 Ld 10 years .......c.iiiiiiiiii 131 2 16.0 83 11 133 48 10 20.8 1) YRATS vies inom ev nim 5350 © 555 5 Wi 2 58 E Brey BY 126 26 20.6 56 11 19.6 70 15 21.4 AD BRIER: uc sno bin win shuns se ies Wind nae’. hdl ond 90 29 32.2 42 15 35.7 48 14 29.2 13 years and OVE . uv surs mms mns an cmnt nn 76 21 27.6 29 13 44.8 47 8 17.0 ARE GARKBOWIR 5. vot 6 oie 4.09: 85 505 508 4 Bok 3 5 8 8 le 2 0 * 2 0 * 0 0 * Total ......oovvi 437 99 %* 219 50 * 218 49 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 8D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 8] Length of Total Total Rate Number Number Rate Number Number Rate : Percent Percent Percent residence number number per ti urban urban per ti rural rural per sith (years) tested positive 100 POSTIVE | tested positive 100 POSILIVE | tested positive 100 positive Less than ..... 40 9 225 9.2 25 4 16.0 8.2 15 5 333 10.2 Lehi 102 27 26.5 27.6 69 17 24.6 34.7 33 10 30.3 20.4 BY pvusmussnis on 91 18 19.8 18.4 41 5 12.2 10.2 50 13 26.0 26.5 10-14 ........... 201 4 21.9 44.9 82 23 28.0 46.9 119 21 17.6 42.9 Unknown ........ 3 1 x * 2 1 x * 1 0 J 5 Total.......... 437 99 * 100.0 219 50 * 100.0 218 49 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 32 spectively. In San Lorenzo a rate of 8 percent was found. Faust, et al (1934) reported in the Caguas area a prevalence rate of 31 percent. In our study, Aguas Buenas had an urban school rate of 11 percent, Caguas had a combined urban-rural school rate of 22 percent, and San Lorenzo had a combined urban-rural school rate of 27 percent. ® Area 9 comprises two of the watersheds of the Rio Piedras stream system, Quebrada San Anton, and a network of brackish water marshes and lagoons. Metropolitan San Juan includes the island of San Juan, and the municipalities of Santurce and Rio Piedras (Map 9). The southern part of the study area is piedmont and the northern part is coastal plain. The total popu- lation of this area is approximately 507,000 people. There were 204 classrooms in thisarea from which 17 fifth grade classrooms (10 urban and 7 rural) were selected and 516 students were skin tested. Prevalence rates for urban schools ranged from 0-25 percent with an average of 11 percent and in rural schools from 3-31 percent with an MAP 9, AREA NO. 9 Sen Juan and Rio Piedras area O Urban * Rural ® Not sampled 000 — School Number * — Type oi School 00 — % Infection average of 16 percent (Table 9A). Combined prevalence for both urban and rural schools was 11 percent. In stratum 1 urban and rural schools, prevalence was greater in males than in fe- males; this was true for urban schools of stratum 2, but in rural schools female students were more reactive than males (Table 9B). The distribution of positive skin reactors by age showed a sharp increase hetween 11 and 12 year olds in reactivity in both rural andurban schools Table 9A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 9] Number | Number Rate Average Average Stratum School code os per | antigen | control tested | positive 100 area area Urban: 1 YOOLIL0 .... «vis mv wv wl ol oe 3 080% 0% ¥ 900080 0% 3 90 00 0 Ey i 29 4 13.8 0.9 0.5 1 TBOOLYDS ... cnn worn wim & mown wh 0 0818 ni 55.5000 7 000 0 WINE 4 OH 2 20 8 i 20 5 25.0 0.8 0.6 1 FOOTITT cn ic mmc roe oo vi ws of ss os i Al 0 BEI % Rit 34 4 11.8 0.8 0.5 1 YOOUZON ..sooun mis os emis vimn s HH 5 DIE 6 © 5 5 000 8 5 4 350 4 930 & mower v 34 1 2.9 0.7 0.6 1 FOOV0D .... oc. wooo res 3 ns v2 ovr 0 ws wis we msn 3 rom msl § ios #8 86 8 0 600 3 33 2 6.1 0.8 0.5 1 NOTXROD, co 2 com 7 5.0500 5 5 5 fi To © 00 7 TCU B20 © ay ave bs at io whe 26 0 0.0 0.7 0.5 1 FOATL0T7 ins oer dns oid ts 0 coh ck 3 955 5 05 9 WE ¥ BU 0 B08 47 6 12.8 0.8 0.5 1 1801106 oot eee 25 5 20.0 0.9, 0.5 2 YOOVY2D: inns prs sums Sis ines i S05 B05 85 5 8 379 wins mom 6 14 1 7: 0.7 0.5 2 YOOL20B ... cv mc vit vem 1 cts ww ch con ot 5 40 BAY HE 6 TRE REE 36 3 8.3 0.8 0.6 TOta . conv om nmin bins vain 5 EE 26600 BEER LPS BEE pe 298 31 %* 0.8 0.5 Rural: 1 I602130 ov nr toms mis EE SITET EAE HR SAW AHIR 3 2 6.1 0.7 0.5 I 1602302 ott 33 12 36.4 1.4 0.6 1 ROOTS: ns p vin sm 2 7 om oh 0 ET STW 2 5 BR By BE pen a ln le 18 2 111 0.7 0.5 2 VIBIROD cies acs wx ho i ch i $0 3 ot 0% EHH ERE BR BO 5 3 37 3 8.1 0.6 0.5 2 1152300 oo 35 1 31.4 0.9 0.5 2 IBZ . overt ceom nmr was 0 pi 2 i 5 SEER BET HERB EE 29 4 13.8 0.8 0.6 2 ANE S08 |; 0p 1s nl 71 Be 0 Gy © 0 0h np homens ee) inc. We ws 33 1 3.0 0.6 0.5 TOLAL . ves vn ven mmr mrtn ni An EI IRE EONAR GEE MEER RE 218 35 * 0.8 0.5 Grand BoTal 21 cw sme mi swan ans wmssmn ws bd snl we ole sks wm 516 66 * 0.8 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 33 (Table 9C). Only 32 percent of skin reactive students from urban schools were residents of 10 years or longer, and 86 percent of students in rural school areas were in this category (Table 9D). Only a few parts of the Metropolitan San Juan complex can support endemic schistoso- miasis. Fresh water bodies do not exist on the island of San Juan; while the few remaining streams in Santurce are becoming increasingly less capable of supporting Australorbis due to generalized pollution. Streams of the Rio Piedras municipal area are still hazardous as they have been for decades. Thus, significantly, this study detected evidence of infection for the most part in migrants from numerous endemic areas of Puerto Rico. Weller and Dammin (1945) reported for the San Juan area a prevalence rate of 7 per- cent and in our study we found an average of 11 percent. White, Pimentel, and Garcia (1957) reported for Rio Piedras a rate of 24 percent and Weller and Dammin (1945) reported a rate of 17 percent for the same area. We found the rural school rate to be 16 percent. e Area 10 contains part of the Rio Bayamon watershed and all of the Rio Guaynabo, plus the towns of Catano, Bayamon, and Guaynabo. The total population of this area is approximately 119,000 people (Map 10). The area consists of rolling hills and flat coastal plains. There were 106 fifth grade classrooms in this area from which 16 were selected (8 urban and 8 rural) and 496 students were skin tested. Prevalence of skin reactors in urban schools ranged from 3 percent-18 percent with an Table 9B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 9] Total Total Rate number number per tested positive 100 Type school male Number Number Rate male tested positive 100 Number Number unknown unknown tested positive Number Number Rate female female per tested positive 100 per Stratum 1: Urban .............. 248 27 10.9 115 18 15.7 131 8 6.1 1) 1 Burd) io vine sms vwiv 84 16 19.0 47 10 21.3 87 6 16.2 - - Stratum 2: Urban cu. swnssmsnsss 50 4 8.0 22 4 18.2 28 0 0.0 - - Bural ....ossaiems 134 19 14.2 64 7 10.9 68 12 17.6 2 0 Total , vse »vivsvnins 516 66 % 248 39 *% 264 26 * 4 1 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 9C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 9] Total Total number number tested positive 100 Number Number Rate rural rural per tested positive 100 Number Number Rate urban urban per tested positive 100 Rate per Under 10 years ...............coovnvnnnn... 28 2 7.1 20 2 10.0 8 0 * 10/YOARS vos vimmss mes dir 2 450 5 9% 55 6585 5 253 161 12 7.5 105 8 7.6 56 4 71 LLYBAES ... «ior sinis moni en von wmenaevn nh ce 164 14 8.5 104 9 8.7 60 5 8.3 12 VATE ov suis vis vows 5 5005 008 4 430 Wid 8 STH Wine 87 17 19.3 44 7 159 43 10 23.3 13 years afd OVEr ..... coum vminnn vs vwive suns 73 21 28.8 22 5 22.7 51 16 314 Age QDKNOWR 2 oop yup runs ws sm sms so wins 3 0 * 3 0 i 0 0 % TOBY 000s vind sins man aden smh on sn gions Sane 516 66 * 298 31 * 218 35 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 34 Table 9D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 9] Length of Total Total Rate p : Number Number Rate p t Number Number Rate Percent residence number number per afaed urban urban per an rural rural per een (years) tested positive 100 POSTIVE | tested positive 100 POSIIVE | tested positive 100 positive Less than l ..... 32 3 9.4 4.5 13 1 7.7 3.2 19 2 10.5 5.7 1-4 ............. 110 16 14.5 24.2 94 14 14.9 45.2 16 2 12.5 5.7 7 JE A 90 7 7.8 10.6 70 6 8.6 19.4 20 1 5.0 2.9 10-14... 0c vn u 276 40 14.5 60.6 114 10 8.8 323 162 30 18.5 85.7 Unknown ........ 8 0 * * 7 0 * * 1 0 * * Total. -w.acnpns 516 66 * 100.0 298 31 * 100.0 218 35 ¥ 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. MAP 10, AREA NO. 10 SATAN, 2d Bos * o 301 o 000 — School Number * — Type of School ws 4 00 — % Infection 3 BAYAMON OQ Urban * Rural ® Not sampled average of 8 percent (Table 10A). Combined prevalence for both urban and rural schools was 10 percent, Little difference inprevalence rates between rural and urban schools was noted (Table 10B), and highest skin reactivity was found in 11-year-old rural students and 12-year- old urban students (Table 10C). Only 35 percent of urban and 58 percent of rural schools skin reactors were life-long residents and evidence of large movement of both urban and rural students was evident (Table 10D). Schistosomiasis is still being transmitted in Area 10 in the swamps of the Catano suburbs, and the streams and swamps of Bayamon over- run by expanding urbanization; a few small tributaries of the Rio Guaynabo are still po- tential foci for infection. The relative high number of skin reactors who have lived in the 35 area for less than five years attests to the active migration of individuals from other areas into more urbanized housing. Weller and Dammin (1945) reported for Catano prevalence rates of 8 percent and for Bayamon 3 percent. It should be noted that these surveys were conducted prior to current major urbanization expansion in these towns. Our study gives an overall rate of 10 percent. e Area 11 is part of the Bayamon River water- shed and contains a portion of the Rio Bayamon and Lago (Lake) Cidra (Map 11). This piedmont MAP 11, AREA NO. 11 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled area is devoted to tobacco and sugar cane production. There are no urban schools in the study area. The total population is approxi- mately 15,000 people. There were 7 fifth grade Table 10A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 10] % Nusber | Number Rate Average Average tratum School code tot per | antigen | control tested | positive 100 area area Urban: 3 BULIVOD oo. or 25 ins oie i onc on Bonen sce iil sec wel 34 8 23.5 0.8 0.4 3 VIVVIDD ov vm oman ms a mon 500m 3 00 60 000 4 900 530% & 6 0 7 000 5 S003 BEL 4 36 4 11.4] 9.7 0.4 3 0 URN 33 3 9.1 0.6 0.5 3 VIVID oe vomsnms noms aw so hn ames WE HS 655% EAS WH E8030 % 9 36 5 13.9 0.7 0.4 3 BUBTTOT cc vs no won co brn ion ss + i es vs. i 32 0 0.0 0.6 0.4 3 1I6FLIY 4s snmesmsromanmmss msn ss BusnE soso mas sHEa® som 29 1 3.4 0.6 0.5 3 YVOVNYS isi 55 008 cs 3 i 7 5m 0h i #0 3 i 5 Fos ei oe» 34 4 11.8 0.7 0.4 3 NBOABOU cen visi io ole i © om in 3 45 on ns #30 iy 2 32 1 3.1 0.5 0.4 TORY cc 5 os 2 0 ci oot sr 003 es se So 23 3 sa ss 3, 266 26 * 0.7 0.4 Rural: 1 DBODVDD ...... cn os simi sis 0 0 i is cn nr 0 cs Tet 0 28 1 3.6 0.7 0.4 1 1602127 25 3 12.0 0.9 0.6 2 BVVDBOG vnsuvsvmrsmssmiaasrnss dmasvios Mpsamsnind mes ny 35 2 5.7 0.6 0.4 2 VIOZTOH cc nici ios sin 0: sevice bso vn 27 2 7.4 0.6 0.4 3 IVZUOO oo isrmrnnrs mons muramos use Hasenas® emis mss ey 25 3 12.0 0.7 0.4 3 1112301 .... errr area 33 6 13.2 0.8 0.4 3 MBLTB io vuminmra mes manmsremsnm swe gms pmesw ys sgs wr 28 1 3.6 0.5 0.4 3 169230) ,cisnssmasmabmiinispmermat mass mas nasssimasme 29 1 3.4 0.7 0.6 TPB Go. 7 ws si overt 0 0 510500 ol ois os veo ss i 0 90 ve i 230 19 * 0.7 0.5 GHANA BOUAL i... 00s nn 6 5 hse 5 en Sm 496 45 * 0.7 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 10B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 10] Type school Total Total Rate number number per tested positive 100 male male Number Number Rate per tested positive 100 Number Number Rate female female per tested positive 100 Number Number unknown unknown tested positive Stratum 1: Urban Rural Stratum 2: Urban Rural Stratum 3: owe 53 4 7.5 20 1 5.0 33 3 9.1 - - ‘3% we 62 4 6.5 39 3 7.7 23 1 4.3 —- - : pe 266 26 9.8 142 21 14.8 124 5 4.0 - - § HE 115 1] 9.6 64 10 15.6 51 1 2.0 — - . W158 496 45 ¥ 265 35 ® 231 10 * — —- *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 36 Table 10C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 10) Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 JOAIE .. «cut v non v's nin 4 at S054 5 305 $3002 83 7 0 * 7 0 * 0 0 * ID YEATES sowrsmnsmnsvvssmusmrsmermmrgraan 134 6 4.5 78 5 6.4 56 1 1.8 llyears .........ovvivnrninnrvnncannnnsen 192 21 10.9 96 8 8.3 96 13 13.5 D2 YRETS iss wn o ms insu eng pv pe wn n 101 12 11.9 64 10 15.6 37 2 5.4 13 years and OVEI wovus sss nms mse mm suns 62 6 9.7 21 3 14.3 41 3 7.3 kala s mest vd te samp arte ion 4. npn suse ey 496 45 % 266 26 * 230 19 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 10D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 10] Length of Total Total Rate Number Number Rate Number Number Rate . Percent Percent Percent residence number number per siti urban urban per ti rural ~~ rural per ti (years) tested positive 100 POSTIVE | tested positive 100 POSTIVE | tested positive 100 posiLive Less than1 ..... 36 1 2.8 2.2 23 1 4.3 3.8 13 0 0.0 0.0 14 wcinessnanms 135 12 8.9 26.7 93 9 9.7 34.6 42 3 7] 15.8 59 116 12 10.3 26.7 64 7 10.9 26.9 52 5 96 26.3 10-04. smvrams 198 20 10.1 44.4 81 9 11.1 34.6 117 11 9.4 57.9 Unknown ........ 11 0 * * 5 0 * * 6 0 x * Toralvi : on rsmms 496 45 * 100.0 266 26 * 100.0 230 19 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. classrooms in this area from which 5 were chosen and 120 students were skin tested. Skin reactivity lacked homogeneity in this area and averaged 15 percent (Table 11A). Males were more reactive than females (Table 11B) and no marked change in sensitivity with increase in age through 12 years was noted. There were no positive reactors among fifteen 13-year-olds (Table 11C). In this watershed area only 33 percent of the reactors have resided less than five years (Table 11D). Schistoso- miasis is known to be lightly endemic in this area (Ferguson, 1955). e Area 12 is part of the Riode la Plata River watershed and contains the Rio Guavate, a southern portion of Rio de La Plata, and the Rios Arroyata and Usabon plus Lago Carite. The watershed includes the urban areas 37 Comerio, Barranquitas, Aibonito, Cidra, and Cayey (Map 12). The area is partly hilly and partly mountainous. The numerous streams, up- land bogs, and Lago Carite furnish excellent MAP 12, AREA NO. 12 O Urban * Rural ® Not sampled 000 — School Number * — Type of School 00 — % Infection Table 11A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 11] Nusber | Nowber Rate Average Average Stratum School code on per | antigen | control tested | positive 100 area area Rural: 1 BOUDTNO iy nnn ssw ain 508s 50 900 4 5 0 S00 HW 00d 5 ie 9 2 22.2 0.7 0.4 1 LOUDTTD iv iin e 5 005s 500 ss ie 3. le 0 wi ss wl 22 1 4.6 0.6 0.4 1 BOAZBON «cc ovo ove nie mvs Bis 3 we 9 win wt i oe 27 1 3.7 0.6 0.4 1 1202007 | on inniomas ons vio shmans ne ins sis snes sesas sass 34 6 17.6 0.7 0.4 1 ER ORTON i 4.500 eat bets Foals dint lt i 7 0 bi mee 28 8 28.6 0.8 0.4 Grand BUA 5; gis 500 2 0000005 5095000 wt 2 wn sim on 1 ise 120 18 * 0.7 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 11B.-Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 11] Total Total Type school number number per tested positive 100 Rate Number Number Rate male male per tested positive 100 Number Number Rate female per tested positive 100 female Number Number unknown unknown tested positive Stratum 1: Urban .............. - - — we - - = = — pe = Rural .uosvninmnsomes 120 13 15.0 52 Il 21.2 68 7 10.3 - — Total vovueinnervs 120 18 * 52 I * 68 7 %* - —- *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 11C.—Distribution of positive skin reactors by watershed area, age, and type school (Watershed areall] Total number number tested positive 100 Total Rate per Number Number Rate urban tested positive 100 urban per Number Number Rate rural tested positive 100 rural per Under 10 years .................cc0vvnnn... 5 0 % - - - 5 0 h YOYERES: vv wom 5 i 2500 5 50 5 ke» Fri ind #4 on nn 34 5 14.7 — - - 34 5 14.7 HY VEaIS ov inet Joy Td pe PE ES TE 30 5 16.7 — —- — 30 5 16.7 YD VRAES: ws ins nme #4 0 400i 0D B06 Baki Rake $2 kk 36 8 22.2 - - — 36 8 22.2 13 years and over ........................ 15 0 0.0 - - - 15 0 0.0 Total. coun ums ime vm wnrsnesmsvhisans 120 18 * - - — 120 18 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or ior unknowns. 38 Table 11D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 11] Length of Total Total Rate Number Number Rate Number Number Rate residence number number per Posogat urban urban per Peon: rural rural per Paroent (years) tested positive 100 posiuive | tested positive 100 POSIIVE | tested positive 100 Positive Less than ..... 8 2 g 11.1 - - - - 8 2 * 111 Ralls vids ddd vos 16 4 25.0 22.2 — - —- — 16 4 25.0 22.2 5 11 0 0.0 0.0 — - - - 1 0 0.0 0.0 10-14.......c.0n. 84 12 14.3 66.7 —- —= — - 84 12 14.3 66.7 Unknown ........ 1 0 x X - —- —- — 1 0 ® * Total. ......... 120 18 * 100.0 —- —- - — 120 18 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. habitats for Australorbis. The total population of this area is approximately 90,000 people. There were 76 fifth grade classrooms in this area from which 16 were chosen (6 urban and 10 rural) and 512 students were skin tested. Prevalence rates in urban schools were high and varied from 2 percent to 51 percent (average 20 percent). Skin reactivity in rural schools also varied with strata 3 and 4 high, 2 low and 1 medium (Table 12A), The overall Table 12A.—Distribution of Positive skin reactors by individual sample classrooms [Watershed area 12] Number | Number Rate Average Bane Stratum School code wested | posivive 3 antigen | contro area area Urban: 1 TLZATOZ sven ure wim moms min 3 Hk B80 # BEES B03 0 aw win wc 42 1 2.4 0.5 0.4 1 ARZUTOD vais om 5 www om ot St 2 8 B00 5% 0 £400 8 ow www 36 5 13.9 0.6 0.4 2 TZOULOB oven win tis sim 52 315s Wms wim swim ww monn om 3 BoA ¥ B78 4 4 36 5 13.9 0.7 0.4 3 TOBIRIOL ., ns vonrmmr mmm romn mrs BRAS E RBI 2 BE sa Waa mw ewww 36 7 19.4 0.7 0.3 4 VEOTTOL ss mone viv b5 mms www orn bomom wow ww wc $45 3 SEE HEED 3 32 13 40.6 1.0 0.4 4 BATE urns vos win # wins 8 56 590 § Hi 0 Bw 6 8 00 ww 0 ww wn 35 18 51.4 12 0.4 PAY. ooo 55 00 5 GES 5 5 8 BA Bs We wail 8 hk 3 BERBERS 217 49 % 0.8 0.4 Rural: 1 AUT2B03 conversa mesmunmmenmesmes maroon: ba dain 38 wes 38 3 7.9 0.5 0.4 1 172002 cies cman na FRR RRR SWS an wis Sots www wd 0s 32 5 15.6 0.6 0.4 1 ABO2UO00 55000 7 mwa 91m 93 00050 wim wim 0 & cs F050 3 MHEG 90 $8 00 22 4 182 0.8 0.4 2 ROBTBOT ev vnon vo mins io SATE AE SRS BE ow an ew Bmw was 26 1 3.8 0.5 0.3 2 TZOZ10B . ov vevrrmrsmmemmsancrmurmns sn tsnstnssnssees 39 2 5] 0.6 0.3 2 A2BTO0 vs ce vn iis E58 HT AE EB ERE B00 @ wor wots ww iw 4 Hi? 36 3 8.3 0.6 0.4 3 BOBZLOD: i, si su x iw wom wi min ok iE BEETS 3 BBE GRE 9 wwmiw s 3 3 9.7 0.6 0.3 3 DDABNNE o.oo mew ws won # HE 1.008 3 cs oe wn 4 on ink 8 B00 BBA 16 0 0.0 0.6 0.4 3 ROBOT x vs von wows www ono ki £0 8 HI 0 4 8 tei ws wow oo 19 10 52.6 1.1 0.4 4 TODOBOD .. cois vis 50 5 00 5 Bi 3 id Hee ecb + won 2 0 WE ER 0 5 36 5 13.9 0.7 0.3 TORAL 44s ssn mie some w vo oan somahoh $500 5 5 B00 2 0 SEY Bins a 295 36 * 0.7 0.4 Grand COAL ve cov smisams masses ens ems wins suse neem sv 512 85 * 0.7 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 39 rural school average was 13 percent. Endemicity Schistosomiasis has been known to be en- in this watershed area appears to be focal in demic in some of these areas for along period nature. Combined prevalence for both urban and of time (Ferguson, 1955; Maldonado and Oliver- rural schools was 16 percent. Prevalence rates Gonzalez, 1958). Our data indicate large move- in urban schools were greater than in rural ments of population in both urban and rural schools for strata 2, 3, and 4 (Table 12B). In areas. Maldonado and Oliver-Gonzalez (1958) urban areas a steady increase in skin reactivity reported for 1955 prevalence rates of 8 percent with age was noted (Table 12C). In urban and 6 percent in Comerio and Barranquitas, schools 49 percent of the reactors have resided respectively. In 1953 rates of 14 percentand 11 in the vicinity for 10 or more years and in percent were obtained. Weller and Dammin rural schools 49 percent (Table 12D). (1945) reported the following: Comerio 22 per- Table 12B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 12] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per |unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban: =. omits nioa 78 6 7:7 38 2 5.3 40 4 10.0 - — Baral coo somsnwusans 92 12 13.0 43 9 20.9 49 3 6.1 - - Stratum 2 Urban, sumone sss nme 36 5 13.9 16 4 25.0 20 1 5.0 - - Rural esscnssmenine 101 6 5.9 53 6 11.3 48 0 0.0 X - Stratum .3 Urban, caus 00isemssns 36 7 19.4 16 5 31.2 20 2 10.0 —- - RAtAl . cov ionislioii ow anvne 66 13 19.7 38 9 23.7 28 4 14.3 - - Stratum 4 Urban .............. 67 3 46.3 38 16 42.1 29 15 51.7 - - Rural .ocsvissonsmes 36 5 139 19 4 21.1 17 1 5.9 Taal... oni mms goon 512 85 * 261 55 * 251 30 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 12C.~Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 12] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ....................ou... 22 3 13.6 16 2 12:5 6 1 * LO YOUFS cvs svins am sadist bres is mow monn s mon sn 183 18 9.8 81 14 17:3 102 4 39 LY Yous: ote pny sms Sl Fu A LFW ES TE 140 28 20.0 69 17 24.6 71 11 15.5 12 YRarS nv vmiimot an sumer Bis uiiam ss Bas muns 98 21 21.4 30 10 33.3 68 11 16.2 13 years and over ........................ 69 15 21.7 21 6 28.6 48 9 18.8 TORRY: os vv ee iw 5 8 5 Hw Bk © iki» eine 5.8 orm 512 85 * 217 49 ® 295 36 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 40 Table 12D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 12] Length of Total Total Rate Number Number Rate Number Number Rate ; Percent Percent Percent residence number number per ti urban urban per i rural rural per sitiv (years) tested positive 100 POSIIVE | tested positive 100 POSILIVE | 4 ested positive 100 po ° Less thanl ..... 23 8 34.8 9.5 13 5 38.5 10.2 10 3 30.0 8.6 IB .isusanismsss 103 20 19.4 23.8 34 8 23.5 16.3 69 12 174 343 5-9... 74 15 20.3 17.9 40 12 30.0 24.5 34 3 8.8 8.6 {11.3 7 a 289 41 14.2 48.8 127 24 18.9 49.0 162 17 10.5 48.6 Unknown ........ 23 i * * 3 0 * * 20 1 * Total.....cu::4 512 85 ® 100.0 217 49 * 100.0 295 36 % 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. cent, Barranquitas 14 percent, Aibonito 22 per- cent, Cidra 15 percent, and Cayey 29 percent. An average for this area calculated from their data is 22 percent. Our urban school preva- lence rate of 24 percent was similar. ® Area 13 comprises three watersheds with the Rios Patillas, Chico, and Nigua. The urban areas are Arroyo and Patillas (Map 13). The MAP 13, AREA NO. 13 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled two branches of Rio Patillas and irrigation canal served by Lago Patillas have been recognized sources of bilharzia, The total population of this area is approximately 30,000 people. There were 30 fifth grade classrooms in this area from which 11 were selected (4 urban and 7 rural) and 294 students were skin tested. Skin reactivity in the urban schools of Patillas averaged 26 percent and in Arroyo 14 percent. In rural schools an average rate of 17 percent was obtained. Combined preva- 41 lence for both urban and rural schools was 18 percent. In stratum 1 the highest prevalence rates were observed in urban schools (Table 13A), with more positive reactors among girls than boys. Prevalence rates in stratum 3 were the same for female students in urban and rural schools (Table 13B). Distribution by age showed a slight increase in positive skin reactors with increase in age (Table 13C). In both urban and rural areas a sharp increase in skin reactivity between 11 and 12 year olds was obtained. In urban schools 25 percent of the reactors have resided for less than 5 years and in rural schools 32 percent (Table 13D). The Patillas-Arroyo area is one of the classic foci in Puerto Rico (Ferguson, 1955). Weller and Dammin (1945) reported preva- lence rates of 20 percent and 21 percent in Arroyo and Patillas, respectively, while White, Pimentel, and Garcia (1957) reported a prev- alence rate of 22 percent for rural individuals in Patillas and 52 percent for urban individuals. Our data also reflects a slightly higher inci- dence in urban schools (20 percent compared with 17 percent in rural schools). ® Area 14 comprises four watersheds in- cluding the Rios Salinas, Majada, Jajome, Lapa, Guamani, Seco, and Melania, as well as several creeks and two major irrigation systems. In addition to the natural waterbodies cited, one of the important endemic factors has been two major irrigation canals whichcourse through the area from east to west and the numerous temporary water retention earthen tanks. Historically and as reflected in this study, endemicity has been confined to the coastal parts of this study area which was Table 13A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 13] Nusber| Funiber Rate Average Average Stratum School code a per | antigen | control tested | positive 100 area area Urban: 1 IBALUOUA) oc... hs wm nw hiss where 0 mime 0 0 00 00 7 E000 2 30 11 36.7 1.1 0.5 1 IBATV0LD. «hn sms non wn mi wi 000 m0 0 0 35 6 17.1 0.9 0.5 3 BOBILOVAL ov ivi sions mss Ran 8 80 03 0 5 9 0.080 B06 32 5 15.6 0.9 0.5 3 LOB IOLA amici ea hones sinus oh mich raise wnt he 9 ir So 27 3 11.1 0.8 0.5 TBOVELL: cs vivir sn nik & rk 2b 30 0 5 in £510 2 ST SE 0 0» 124 25 * 0.9 0.5 Rural: 1 ABADUIY. snr unis s asim 2 0mi0% 5% 5 mts mst no Sid's hs won 3 2s 4 min 26 4 154 1.0 0.5 1 ABAABOL . «rss wird ars wr woes sl 4 39s wit 5 © 9 FRG ES Rr ERA 24 3 125 0.6 0.5 1 ISADN0Z soo covmn rman dom irs spans ss sis Syss@ion ss aso 12 2 16.7 0.8 0.3 2 TBUTLTIE ooo 0 tir itor ol si hn smi i in 3 i Te 18 2 11.1 0.7 0.4 3 YOBIVOT coe v nimmmns wins woo sw 3iuw wna 0 SHEE GEE 22 10 45.5 12 0.5 3 TOBDZO: vem wiv bw 0000.5 ie #90008 000 0 © 8.50% 90 0 0 rd 37 1 27 0.6 0.5 3 LOBIBOL a 20:0 sv 4 on olgion i tte es Boba nimi RE 0 deg i 31 7 22.6 0.9 0.5 TORRY duh tive te 5 52 5 20 2.85 5 3 Hom tm £4 0 on it #0 170 29 * 0.8 0.5 Grand Total. ooo uns ons wis wes ns SBI © 0 BLE Po Rot 294 54 * 0.9 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 13B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 13] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per [unknown unknown tested positive 100 | tested positive 100 | tested positive 100 tested positive Stratum 1: TEEDAR oo 5h mw i wr 65 17 26.2 31 ? 22.6 34 10 29.4 - - Rural .onsscssnmsan 62 9 14.5 40 7 17.5 22 2 9.1 - - Stratum 2: Urban susie s sn swipes = - ~ ~ - — - — - - - Rural wsoesismvnmins 18 2 11.1 7 0 * 11 2 18.2 - - Stratum 3: Urbano: vie van» swiss 59 8 13.6 34 4 11.8 25 4 16.0 —- - Baal ssw sve smunin 90 18 20.0 40 10 25.0 50 8 16.0 - - Total svvsvvesnsss 294 54 * 152 28 * 142 26 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 42 Table 13C.-Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 13] Total Total Rate number number per tested positive 100 Number Number Rate urban urban per tested positive 100 Number Number Rate rural rural per tested positive 100 Under10years............covvvnvevnnnn.. 7 1 * 5 1 3 2 0 * 10 Years oi mrsmnuvnssmvsmames smsvsnwe 74 11 14.9 28 3 10.7 46 8 17.4 BL VERT on dois sidls kis hs 4 sia jietemils Rian dio 108 16 14.8 51 9 17.6 57 7 12.3 12 Y0ars ow vmsemas mes vursmasms ss ss ons ve 57 15 26:3 23 7 30.4 34 8 23:5 13 years and OVer ........ovumennorominnsen 48 11 22.9 17 5 29.4 31 6 19.4 Potals zis wis» wins vs presse 331% Low vain ve 294 54 * 124 25 * 170 29 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 13D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 13] Length of Total Total Rate Percent Number Number Rate Percent Number Number Rate Percent residence b : , iden number number per positive urban urban per positive rural rural per positive years) tested positive 100 tested positive 100 tested positive 100 Less than ..... 14 4 28.6 8.2 10 0 0.0 0.0 4 4 % 16.0 1-4 ooo vmsvnssnns 30 10 33.3 20.4 21 6 28.6 25.0 9 4 * 16.0 59... 60 13 21.7 26.5 28 5 179 20.8 32 8 25.0 32.0 10-04; .vonnzinn: 159 22 13.8 449 56 13 23.2 54.2 103 9 8.7 36.0 Unknown ........ 31 5 * % 9 1 * ¥ 22 4 * * Total.w:vcosovms 294 54 ¥ 100.0 124 25 * 100.0 170 29 ¥ 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. reflected in this study. The towns in this area are Salinas, Central Aguirre, and Guayama (Map 14). The total population is approxi- MAP 14, AREA NO. 14 © Urban * Rural ® Not sampled 000 — School Number * — Type of School 00 — % Infection 43 mately 57,000 people. There were 42 fifth grade classrooms in this area from which 13 (5 urban and 8 rural) were selected and 397 students were skin tested. Prevalence rates obtained in urban schools in Salinas and Central Aguirre were low (5 percent) but rose to 19 percent in stratum 3 in Guayama. In rural schools prevalence was 19 percent in stratum 1, 33 percent in stratum 2, and 14 percent in stratum 3. The overall rural school average was 17 percent. En- demicity in rural schools ranged from 0 per- cent to 61 percent (Table 14A). Combined prevalence for both urban and rural schools was 16 percent, Positive skin reactors were more numerous in urban students of stratum 3 with a higher percentage among males than females. In stratum 2 the rural school children were considerably more reactive (Table 14B), In both urban and rural schools there was a slight increase in prevalence with increased age (Table 14C). In urban schools 25 percent of the reactors have resided for 10 or more years and in rural schools 58 percent with indications of large migration intourban areas (Table 14D). This watershed is a well known bilharzial focus (Ferguson 1955). Maldonado and Oliver- Gonzalez (1958) reported for the year 1955 Table 14A.-Distribution of positive skin reactors by individual sample classrooms [Watershed area 14] , Number | Number Rate Average Average tratum School code pp per | antigen | control tested | positive 100 area area Urban: 2 NBRATOZ . 6 coi iors ssi se emt = ws ASR 50 8 BIE 44 BERRA RF BS 34 1 29 0.5 0.4 2 BB2VBOL:| .. oc to 5 is 5 gs 3 ws 3 sir oy rss sm ses 3 vw or ne ea 33 2 6.1 0.6 0.4 3 YZBUIO03 isumimsvmramrsn so gaa me soins ws WHE ESHER BEY WEL IED 36 10 27.8 0.9 0.4 3 DZBUTON oe wos nom st mont cts it 8 io ont ot 8 2 35 8 22.9 1.0 0.5 3 MIBVUOR . , sve s smn wre gan imins oom owns fokon os ow wis ses wes 41 4 9.8 0.6 0.4 TOUR... « vor + orm a'r snc nk mi 1 htt 8 Ht Ph te 8 179 25 ¥ 0.7 0.4 Rural: 1 WEZOVOT .. o.s nt oer 1 Bw 2 Sis vs 5 seni se rsa es wh vr re 34 0 0.0 0.5 0.4 1 YO22V08: onus mrsnonn ss BETHEL HF AFA VRE LW BRE EE OE AH 22 1 4.6 0.6 05 1 BBZANOL ovis smibtramus muss i mas Bh SRS EBB E EE WA 24 0 0.0 0.5 0.3 2 BGO 0: «25m i ols rms os Twn s mab im Ghosts del een ee rin 27 0 0.0 0.5 0.4 2 IB2VVG oven win si aie 5 4 RA 8 E00 5 UL BB EE SIS} EEE BE RR 1 13 4 30.8 1.0 0.5 2 1282301 oe 33 20 60.6 1d 0.4 3 A2B2B0D 5 iso ven 5s 5 wf 8 BERET GI HERE FTES EE Py 29 1 3.4 0.5 0.4 3 U2BIXAB.. . vii voniso eho ha zest o soon of 4 904 hie intr athe te she en 2 36 8 22.2 0.8 0.5 Total ,simisvms vn ron sam EEE RRC EIS EIR EEE TA 218 34 * 0.7 04 GRAB BOEAL . .... cows vain vr airimimn iw dition #4 nts 8 397 59 ¥ 0.37 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 14B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 14] Number Number Rate Number Number Total Total Rate | Number Number Rate Type school number number per male male per tested positive 100 | tested positive 100 unknown unknown tested positive female female per tested positive 100 Stratum 1: LIEBBH J « cononims » aio aan a 5 — - ~ - wi — — - = Rural .............. 80 1 1.2 43 0 0.0 37 1 2.7 - —- Stratum 2: Urban .............. 67 3 4.5 36 2 5.6 31 1 3.2 - - Bural w.cvesvsssmins 73 24 32.9 41 15 36.6 32 9 28.1 — - Stratum 3: Urban .............. 112 22 19.6 59 14 23.7 53 8 15.1 — — Baral (oo sos sone 0500 2 2 65 9 13.8 25 4 16.0 40 5 12.5 —- - Total vu ius isu 2 wis 397 59 % 204 35 x 193 24 * - _ *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 44 Table 14C.=Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 14] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under JO Years wu « «ww wns wow som wo on mms in wn 5 1 * 5 1 * 0 0 ie LO YEARS &iwvuomvnins mine vim «nits sms diss oes 115 6 3.2 61 4 6.6 54 2 3.7 AL YORTS: 'u nv movm vw om in wis sg sen x sw sons #0 132 16 12.1 52 7 13.5 80 9 11.2 12 ¥6ar8 ..uisvneimmssimantis emesis ivesns® 7 19 24.1 29 5 17.2 50 14 28.0 13 years and OVAr ....cuuuwcamrrmemns mesa 66 17 25.8 32 8 25.0 34 9 26.5 WotR): coiinuisnmss mormon din sons ms ar vss 397 59 * 179 25 * 218 34 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 14D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 14] Length of Total Total Rate Number Number Rate Number Number Rate ; Percent Percent Percent residence number number per ti urban urban per i rural rural per ti (years) tested positive 100 POSTIVE | tested positive 100 POSTIVE | tested positive 100 positive Less than1l ..... 13 2 15.4 3.8 10 0 0.0 0.0 3 2 * 6.1 1-4 onsnmmonnss 55 6 10.9 11.3 35 4 11.4 20.0 20 2 10.0 6.1 59... 74 2 28.4 39.6 38 11 28.9 55.0 36 10 27.8 30.3 10-14. ccavsvinss 202 24 11.9 45.3 51 5 9.8 25.0 151 19 12.6 57.6 Unknown ........ 53 6 % * 45 8 * * 8 1 * x Total. un. meses 397 59 * 100.0 179 25 * 100.0 218 34 *¥ 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. prevalence rates of 35 percent in Guayama. In 1953 a rate of 60 percent was obtained. Weller and Dammin (1945) reported prevalence rates of 10 percent in Salinas and 30 percent in Guayama., In the Guayama urban schools we obtained rates of 20 percent and in rural schools of stratum 2 (the coastal area) a rate of 33 percent. e Area 15 contains three watersheds con- sisting of the Rios Coamo, Jacaguas, Descal- abrado, Toa Vaca, Cuyon, and Jueyes and Lagos Guayabal and Coamo. The study areas include the urban towns of Juana Diaz, Villalba, Santa Isabel, and Coamo (Map 15). Endemicity is mostly confined to the flat coastal strip. Stratum 1 of this watershed is served by an MAP 15, AREA NO. 15 45 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled extensive irrigation system which contains A. glabratus. The total population of this area is approximately 84,000 people. There were 69 fifth grade classrooms in this area from which 15 (5 urban and 10 rural) were selected and 411 students were skin tested. Prevalence rate for urban and rural schools was very focal and varied from 3 per- cent to 24 percent with an average of 10 per- cent in the former and from 0 percent to 36 percent, with an overall average of 13 percent in the latter (Table 15A), Combined prevalence for both urban and rural schools was 12 per- cent. In general higher rural school prevalence rates were noted except for stratum 3 where urban school students tended to be more skin reactive (Table 15B). Distribution of skin reactivity by age showed little variation in the age groups tested. A slightly higher incidence in older rural students was noted (Table 15C). In urban schools 53 percent and in rural schools 63 percent of the reactors have resided for ten or more years in the area (Table 15D). Historically, the study area was known to be lightly endemic (Ferguson, 1955). Our data suggest that transmission may be taking place in both urban and rural areas in strata areas 1 and 3 near the coast. Weller and Dammin (1945) reported the following prevalence rates: Juana Diaz 7 percent; Villalba 4 percent; Santa Isabel 30 percent, and Coamo 5 percent. Their average prevalence rate was 9 percent, and we obtained an average rate in our study area of 12 percent, e Area 16 is part of the Rio Manati river watershed; the principal tributary is the Rio Orocovis. The only urban town is Orocovis (Map 16). This area consists of rugged mountains entrenched with numerous small streams. The total population of this area is approximately 30,000 people. There were 24 fifth grade classrooms in this area from which 9 (2 urban and 7 rural) were selected and 292 students were skin tested. In urban schools 15 percent of the students were skin reactive whereas in the rural schools Table 15A.-Distribution of positive skin reactors by individual sample classrooms [Watershed area 15] g Number | Number Rate Average Average tratum School code oo per | antigen | control tested | positive 100 area area Urban: 1 BIZVLEO) umsnmermas ams smon wes ss ina vs MET HERE ER REAR AEN 38 4 10.5 0.7 0.5 2 ASUS it or visas Bel row Eo dn in: 0 we Wes i is Wi 37 1 7 0.6 0.4 3 Y6TLIOL «over ours 0 x Eman ws sobs 3 BEB MAS WEE SME 4 H AWTS 20 7 24.1 0.9 0.4 4 IBENRON. ios ho ms sah spe oles wom 1 ms tgs Jono 0: 0 rail 33 2 6.1 0.6 0.5 4 AZVIVO6 + vsemrsmmrnssomis das mea snst wes mes Ser ames mary 36 3 8.3 0.8 0.5 FOAL | vam rss 5 mn 0m pcm 0 i hn 3 0 1 173 17 * 0.7 0.5 Rural: 1 EETTOL, ol Toe lie 0 1 ras ss seh 0 ts Ste os Be 31 1 3.2 0.7 0.5 1 1372000 1 ununwimemmanmanios ars mes sms sas gale ems smisy 25 9 36.0 1] 0.5 2 TTBTUOD: oes enn conn me cnt 4 mom 3 0ma 8 mews wp es ip wai 4m are hom 28 1 3.6 0.7 0.4 2 1782009 couvvmmrrnismvnmas nin s BEER EET SHIRE ES ER SH ERD HES 15 0 0.0 0.6 0.5 2 EES Soci ton R005 50 in 5 es ST To Bots. ne te sot) HFT 2 4 17 4 23.5 0.8 0.5 3 IDUBBON vx oom is oo wi test rm vo x oom m0 m0 on mw 50 3 cn 24 0 0.0 0.5 0.4 3 672800, ivrwnrrnvanssprsnnsae iomisamsmsstnes es nnis 24 6 25.0 1.0 0.4 3 OP B00 vii oo Fi i oo hE aon wi A es Hr stil 23 4 17.4 0.9 0.5 4 122002 .pvrnm ssn mena sos Sv aE BELA E AERRE SE 11 0 0.0 0.6 0.5 4 VRIBABB: 0. ris wiaihaile el os nim tly smilie iis sh oo Gv veoh hl ron 40 5 12.5 0.8 0.5 Total |, oosuivuimusn somes ons pus sess amssnsems inns ves 238 30 * 0.8 0.5 Grand total .... coon imme mmr rn nn 411 47 * 0.8 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 46 Table 15B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 15] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban w.omsenesmnere 38 4 10.5 15 1 6.7 23 3 13.0 - — Rural «aes enssnnsns 56 10 17.9 29 6 20.7 27 4 14.8 — - Stratum 2: Urban .: ou canes smens 37 1 2.7 14 A 71 23 0 0.0 — —- Rural o:ceesmmswiessn 60 5 8.3 34 3 8.8 26 2 7.7 — - Stratum 3: Urhan «ovis moe caves an 29 7 24.1 14 4 28.6 15 3 20.0 — — Rural isms smesonens 71 10 14.1 43 7 16.3 28 3 10.7 - - Stratum 4: Urban w. gos smxrsmran 69 5 7.2 33 5 15.2 36 0 0.0 — - Rural .............. 51 5 9.8 27 4 14.8 24 1 4.2 - — Total avs cnn som sam 411 47 * 209 31 x 202 16 & — —- *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 15C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 15) Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 URAEE 10 YATE wivs wis sin + s wr whip ams waits 21m 2500 7 0 * 5 0 * 2 0 * 10 years uv rvnmerm nso eo me ans cameos ng 83 6 7.2 52 3 5.8 31 3 9.7 11 YeRar8 ....vvvevmsnnnsvssmusnmsnrms amiss 171 19 11.1 63 8 12.7 108 11 10.2 12 ¥€arS ouviimacomenmn smn os REE BETTE 92 1) 12.0 35 4 11.4 57 7 12.3 13 years and OVEF ou iunv uum rmd voi oimesnmnrn 58 11 19.0 18 2 11.1 40 9 22.5 Total, . vosmv vvssmus ns aman vores s 411 47 ¥ 173 17 * 238 30 ¥ *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 15D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 15] Length of Total Total Rate Number Number Rate Number Number Rate residence b b Percent b rb Demsent rural rural er Parotnt number number per positive urban urban per positive ra p positive (years) tested positive 100 tested positive 100 tested positive 100 Less than 1 ..... 18 6 33.3 12.8 nn 4 36.4 23.5 7 2 %* 6.7 1-4 .:vcinmavmans 91 Ll 12.1 23.4 27 3 11.1 17.6 64 8 12.5 26.7 59... 68 2 2.9 4.3 23 1 4.3 5.9 45 1 2.2 3.3 10-14 on cumosmesns 228 28 12.3 59.6 107 9 8.4 52.9 121 19 15.7 63.3 Unknown ........ 6 0 * * 5 0 * * 1 0 * * Totalevvvinniis 411 47 * 100.0 173 17 * 100.0 238 30 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 47 MAP 16, AREA NO. 16 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled skin reactivity ranged from 0 percent to 8 percent (Table 16A). Combined prevalence for both urban and rural schools was 7 percent. Urban male and female students were most reactive (Table 16B). In rural schools there was no increase in skin sensitivity with age but in urban schools a sharp increase between the 11 and 12 year group was noted (Table 16C). In urban schools 54 percent of the reactors have resided for 10 or more years in the area and in rural schools 80 percent (Table 16D). Bilharzia has not been commonly reported from the area (Ferguson, 1955). Weller and Table 16A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 16) Number | Number Rate Average Average Stratum School code os per | antigen | control tested | positive 100 area area Urban: 2 ABBITO-T , oon vimernsn madmen wm s am asim ps wes ews nuns wes wes 47 8 17.0 0.8 0.5 2 IBBYIOF-2. csnrsmis mr rns sR ER IA SE PHA MERGERS HER 38 5 13.2 0.7 0.5 Total ite 85 13 «| os 0.5 Rural: 1 VHODION + oct: Trion wo inssnfin am wamEans is 10 sims 0 00 eam ei dso wend i 24 1 4.2 0.7 0.4 1 YOB2V02 ,sumss vss mstniines BUTI A NEI MET EEN EE Ryu 36 2 5.6 0.5 0.3 2 YBOZVID nn vvnmmn sms meson ssn ns i HR SRE ESTEE TER WS 38 1 2.6 0.6 0.5 2 VBOPTHG ; soins an 3 wins 57% wins 5nop 5. se Fia as onse Don esrsdd wai ib 19 0 0.0 0.5 0.4 2 IBBBYR) i usmmromas ms mas EE EWE W yh CR PIE HE ERE ES 18 1 5.6 0.6 0.4 2 1532302 oie 38 3 79 0:5 0.3 2 ABB2BOB. usm vara Was Er TEE ARR PERE PEL UAE UR WE 34 2 5.9 0.6 0.5 Total .... oe 207 10 * 0.6 0.4 Grand tots) cu anesnismes sas ars mas mus LEE RE A 2G LED I PE 292 23 * 0.6 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 16B.=Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 16] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban sons sms rmrsuns - - - - - - - - - - - Bural .soivnsamesans 60 3 5.0 36 2 5.6 22 1 4.5 2 0 Stratum 2: Urban : wos we 5 awe s 90s 85 13 15.3 35 6 17.1 50 7 14.0 —- - Rural .............. 147 7 4.8 73 4 5.5 74 3 4.1 — - Total os0meruasmms 292 23 * 144 12 * 146 11 * 2 0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 48 Table 16C.—Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 16] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years :vvirvrassrniemus ams nina 6 0 * 4 0 ® 2 0 % BOERS: 1 vo. vor wives bake sti id ae dd oss. 54 3 5.6 17 2 11.8 37 1 2.7 YL YORE wivuwenmonsmsmmsnms ides nds mms san 98 7 7:1 27 2 7.4 1 5 7.0 12 YEAS otitis 70 8 11.4 21 5 23.8 49 3 6.1 13 years and over ....comianensasenes venus 59 5 8.5 16 4 25.0 43 1 2.3 AGE WNKROWR os vino s mms mina s ms smss bie 354 5 0 * 0 0 ¥ 5 0 * Total ..vocvwrsvsivmismosmornmrsmus ens 202 23 * 85 13 * 207 10 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 16D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 16] Length of Total Total Rate Number Number Rate Number Number Rate : Percent Percent Percent residence number number per ositi urban urban per it rural rural per it (years) tested positive 100 POSTIVE | tested positive 100 POSTIVE | tested positive 100 positive Less than 1 ..... 10 2 20.0 8.7 5 2 % 15.4 5 0 ¥ 0.0 A oswsssmunne 26 2 7.7 8.7 15 2 13.3 15.4 11 0 0.0 0.0 59... 57 4 7.0 17.4 19 2 10.5 15.4 38 2 5.3 20.0 10-04 cuisines: 188 15 8.0 65.2 44 7 15.9 53.8 144 8 5.6 80.0 Unknown ........ 11 0 * * 2 0 ie ¥ 9 0 ¥ * Totaliv.one:sn. 292 23 % 100.0 85 13 * 100.0 207 10 % 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. Dammin (1945) reported a prevalence rate of only 1 percent in Orocovis. Although only 16 percent of the urban school children who had lived in the area all their lives were skin reactive, this represents 54 percent of all the skin reactives and indicates that schistoso- miasis has been transmitted mainly near the urban schools. eo Area 17 is part of the Rio Grande de Manati watershed containing the tributaries Rios Bauta, Toro Negro, Matrullas, Ci- alitos, plus the Lagos Matrullas and Guineo. Ciales is the only town. The watershed is mountainous (Map 17). The total population is approximately 25,000 people. There were 21 fifth grade classrooms in this area from which 49 MAP 17, AREA NO. 17 000 — School Number * — Type of School 00 — % Infection O Urban * Rural ® Not sampled 9 were selected (2 urban and 7 rural) and 188 students were skin tested. Average prevalence rate per classroom in the same school in Ciales ranged from 8 per- cent to 17 percent, with a combined urban average of 12 percent. In rural schools preva- lence rates were low, ranging from 0 percent in 3 schools to 11 percent (1 reactor) in one school (Table 17A). An average rate of 5 per- cent was found. Combined prevalence for both urban and rural schools was 6 percent. Of the nine skin reactors, five were urban school students (Table 17B). No definite trend with age was demonstrated (Table 17C). Only 28 of the 188 students tested had resided in the area less than 5 years. Of the 13 skin reactors in this area only 3 had lived there less than 10 years (Table 17 D), Weller and Dammin (1945) reported a prevalence of 9 percent in Ciales. White, Pimentel and Garcia (1957) reported Table 17A.-Distribution of positive skin reactors by individual sample classrooms [Watershed area 17] Nuvber | Nowber Rate Average Average Stratum School code i per | antigen | control tested | positive 100 area area Urban: 1 YUDLVOL-D cov nmnnms os oars 8000 88040 76 E0R'S 33% 5065 2705 5 09 36 3 8.3 0.7 0.5 1 USN MOND, 4 ocr bday ion disins. ce 0 Wl mrt fms # i 0 Aint 23 4 17.4 0.8 0.5 Total... onsianisv isms Russ T emesis MEST vi bins Bes ve 59 7 * 0.7 03 Rural: 1 MOBO oe sins olimiincilit ne sms Henson aia Wc. 5 nse Amel isd SRA pt 23 2 8.7 0.7 0.4 1 6:1 8 0 0.0 0.7 0.6 1 UBBOUDE: ions ior rio dels i ve ib rh ers cn op 9 I 11.1 0.7 0.4 1 ABBIBOA .ivoims nmr viode my dms ding pms s Sins ewes tems voesus 31 1 3.2 0.6 0.4 1 IBBRBOB cio noted ose ori mis os i ie 4 WB 0 WAAR 0 0 RRS 18 0 0.0 0.6 0.4 2 ATO0O0 rons usa t ns samo nahn swe 1303 Bo i bi 5 12 0 0.0 0.7 0.5 2 YBB2BOF comin s nasa ands aw a8 ha Tm sums 33 £44 La00 8 08 £ 2500 28 2 7.1 0.6 0.5 BOX ser antdnnigs fatima «vf wird wil « wires Je 129 6 * 0.7 0.5 Grand ROERL . uc. «vows ws wus vn ms moms dinnn mn moon om 0 am 2 9.00 188 13 * 0.7 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 17B.=Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 17] Total Total Rate |Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per [unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban iu: swesmvervss 59 7 11.9 31 5 16.1 28 2 7.4 - —_ BEAL ods 2 sini iis ovine 89 4 4.5 54 3 5.6 35 1 2.9 - - Stratum 2: UrBan sw ss ve sme somes - —- — - - = = on oes = = Rural .............. 40 2 5.0 25 1 4.0 15 1 6.7 _- - Total cours amesnvs 188 13 * 110 9 * 78 4 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 50 Table 17C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 17] Total Total number number tested positive 100 Number Number Rate rural per tested positive 100 Number Number Rate urban urban per tested positive 100 Rate per rural Under 10 Years « vs vet swssws sims snr sms e mie 1 20 1 0 E 0 0 % 1 0 * JOVERTE lore oir nlmiondiocn, a tei ils wlth ls mini 33 2 6.1 10 1 10.0 23 1 4.3 11 YEAS wiv inv sow su vw waits wisi iw Wins oi 70 5 7.1 27 3 11. 43 2 4.7 12 Years .....viiiiiiiiii a 46 4 8.7 14 1 74 32 3 9.4 13 years and over «us cessnrrno mur eaw ans sun 38 2 5.3 8 2 * 30 0 0.0 TOtaL. vv + ves ww vir svi www nb wy a 188 13 * 59 7 * 129 6 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 17D.=Skin reactor rates and percentage distribution of positives by length of residence, P 8 p y leng type school and watershed area [Watershed area 17] . Length of Total Total Rate Number Number Rate Number Number Rate ’ Percent Percent Percent residence number number per iti urban urban per Hive rural rural per ositive (years) tested positive 100 POSTIVE | tested positive 100 posits tested positive 100 P Less than1 ..... 7 1 * 77 1 * 14.3 0 0 % 0.0 Ye cine vnn vans 21 0 0.0 0.0 15 0 0.0 0.0 6 0 * 0.0 50; iii 05 590s 2w 21 2 9.5 15.4 1 * 14.3 12 1 8.3 16.7 10-18... ... 0000s 119 10 8.4 76.9 28 5 17.9 71.4 91 5 5.5 83.3 Unknown ........ 20 0 x * 0 ¥ %* 20 0 %* * Total. .«osu 59 188 13 * 100.0 59 7 * 100.0 129 6 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. for the general area a prevalence of 4 percent and we found 6 percent. eo Area 18 is part of the Rio de La Plata watershed containing the Rios Lajas and Guadiana. The only artificial impoundment is near Comerio. The urban areas are Naranjito and Toa Alta (Map 18). The area is mountainous with a total population of approx- imately 54,000 people. There were 38 fifth grade classrooms in this area from which 12 (4 urban and 8 rural schools) were selected and 366 students were skin tested. Skin reactivity in urban schools was low, and in one school (Naranjito) a high prevalence (14 percent) was found in one classroom and 6 percent in the other. The combined urban school average was 9 percent, In rural schools, prevalence was also heterogenous and focalized 51 MAP 18, AREA NO. 18 000 — School Number * — Type of School 00 — % Infection $9 © NARANJITO QUrban * Rural ® Not sampled (Table 18A). The average prevalence rate for rural schools was 10 percent. Combined preva- lence for both urban and rural was 9 percent. In stratum 2, urban school males were more skin reactive than females or rural school males. In stratum 3, urban school females were more reactive than urban males and rural school females. In this area, highest preva- lence rates were found in rural school males (Table 18B). A sharp increase in skin re- activity in the 12 year age group in rural and 13 year age group in urban areas was noted Table 18A.-Distribution of positive skin reactors by individual sample classrooms [Watershed area 18] Number | Number Rate Average Average Stratum School code oy per | antigen | control tested | positive 100 area area Urban: 2 EE TT 38 3 7.9 0.6 0.5 2 TBZULOV-D . .... . coe vc 0 vir mon mvnn ins mits 3 ch £063 HH ETE 8 BARS 30 2 6.7 0.6 0.5 3 VEBLVOUsY, os 55.05 wr mond wins 190% 4 83 S090 4 os tims 3 wae Hops ww gn 36 2 5.6 0.6 0.5 3 YOBYYOV-2 i500 005 om % 7 5k 3 07 G0 8 Wet £ F TR WES DIE 2 IHR EWES 36 5 13.9 0.7 0.5 TORE 57 or nine vr Somes odd iw 2 TERE FUER 4 0 LTE Han pe a ve ee 140 12 * 0.6 0.5 Rural: 1 1112303 ooo 43 2 4.7 0.7 0.4 1 202003: .ouivmi oman a®ns mas 560 oi £0 GE 4 VFL TREE GE RGES HALE 14 2 14.3 0:7 0.4 2 ASBONDE ; oui 5500 2 57e 2. nds renin emi waniion Msiibedimarasonacis seb hobo 34 1 2.9 0.5 0.5 2 BORON icine nes dias Was TE 2 HE FRWAS 00 TREE SHG 8 EDS HELE 26 2 3 0.7 0.5 2 1682106 16 2 12.5 0.7 0.5 3 | Ry ET PE 22 2 9.1 0.6 0.5 3 OBINOA vis ins on dns sin sao nb pedis 0h 4 il BT RB TEES RA 38 6 15.8 0.8 0.5 3 1682301 .. 33 6 18.2 0.9 0.5 OERL cc vo cons cs 5 hom 0 os cs 5 EE BE ri E23 A 2 226 23 X 0.7 0.5 Grand total ...c..ioiimirmsimisannamuinmennmarmeriass 366 35 * 0.7 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 18B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 18] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per [unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban .o.ovsinnsnnss — - - _- - - - — - - - Rural ....ccomvivnss 57 4 7.0 23 1 4.3 34 3 8.8 - - Stratum 2: Drban casvmssmnsnmes 68 5 7.4 34 4 11.8 34 1 2.9 - - Rural .............. 76 5 6.6 44 4 9.1 32 1 3.1 - - Stratum 3: Urban .............. 72 ? 9.7 32 2 6.2 40 5 12,5 - - Rural vovsmsomonnmns 93 14 15.1 46 13 28.3 47 = 1 2:1 - —- Total ..vvvneinnns 366 35 % 179 24 * 187 11 * - — *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 52 (Table 18C). In urban schools 82 percent of the reactors have resided for 10 or more years, and in rural schools the figure was 57 percent (Table 18D), The area was known to be lightly endemic (Ferguson, 1955). Weller and Dammin (1945) reported prevalence rates of 2 percent and 1 percent in Naranjito. ® Area 19 comprises part of the Rio de La Plata and the Rio Cibuco watersheds, with the Rios, Indio, Morovis, Unibon, Mavillas, and Cocal. The only impoundment is the Laguna Tortuguero which is semibrackish and supports populations of A, glabratus in its eastern parts. The urban areas are Toa Baja, Dorado, Vega Baja, Morovis, Vega Alta, and Corozal (Map 19). The area consists of lime- stone hills, piedmont, and flat coastal zones. The total population of this area is approxi- mately 109,000 people. There were 90 fifth MAP 19, AREA NO. 19 QUrban * Rural ® Not sampled 000 — School Number * — Type of School 00 — % Infection grade classrooms in this area from which 16 (7 urban and 9 rural schools) were selected and 479 students were skin tested. Table 18C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 18] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under TO YBAIS wi vs wvrmnsnins emus oe sins muss 18 0 0.0 12 0 0.0 6 0 * 10 years .......oiiiiiiii ii 110 9 8.2 51 5 9.8 59 4 6.8 11 years :iuisnciiwisnarsmsmmemin ss munmase 119 5 4.2 40 2 5.0 79 3 3.8 REVERIE rat smu fase i ele tl ls i 4 fos od 63 7 Ha 23 1 4.3 40 6 15.0 13 years and over .. iu sme immiranrmarmuns 56 4 25.0 14 4 28.6 42 10 23.8 Total, civ svisnmist Giana FERAL RB EOME LH 366 35 * 140 12 * 226 23 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 18D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 18] Length of Total Total Rate Number Number Rate Number Number Rate . Percent Percent Percent residence number number per iti urban urban per ti rural rural per ti (years) tested positive 100 POSILIVE | tested positive 100 POSTIVE | tested positive 100 pRsitive Less than1 ..... 13 1 77 3.1 8 0 X 0.0 5 1 * 4.8 I 42 4 9.5 12.5 17 2 11.8 18.2 25 2 8.0 9.5 59 ..viivnramans 57 6 10.5 18.8 32 0 0.0 0.0 25 6 24.0 28.6 10-04 .....on00 un 224 21 9.4 65.6 78 9 11.5 81.8 146 12 8.2 57.1 Unknown ........ 30 3 * .; 5 1 * * 25 2 * * Total... cco 0s 366 35 * 100.0 140 12 * 100.0 226 23 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 53 Fairly uniform prevalence in all urban sample classrooms was observed with the pro- portion of reactors being 10 percent or less in all schools. Combined urban school skin re- activity averaged 7 percent. The prevalence rates were less than 7 percent in all rural schools In strata 1, 2, 3, and 4. In rural schools stratum 5, the combined average prevalence was 13 percent (Table 19A), Com- bined prevalence for both urban and rural schools was 6 percent. Except for stratum 5, prevalence rates in urban and rural schools were generally higher than in rural schools. No large differences were demonstrated be- tween the sexes (Table 19B). No trends with age were demonstrated (Table 19C), In urban schools only 36 percent and in rural schools 57 percent of the reactors have resided for ten or more years (Table 19D). Bilharzia has not been a prominent problem in this study area (Ferguson, 1955). Weller and Dammin (1945) reported prevalence rates of 1 percent in Toa Baja, 1 percent in Vega Baja, 14 percent in Morovis, 1 percent in Vega Alta, and 1 percent in Corozal. White, Pimentel and Garcia (1957) reported 0 percent in Vega Baja. Our study indicates that very little transmission may be taking place in this watershed. eo Area 20 is part of the Rio Grande de Manati watershed containing the coastal portion of the principal river plus theurbancommuni- ties of Barceloneta and Manati. This area con- sists mostly of rough limestone hills and a flat coastal strip. The total population of this area is approximately 50,000 people (Map 20). There were 41 fifth grade classrooms in this area from which 13 were selected (5 urban and 8 rural) and 380 students were skin tested. Low skin reactivity in urban schools was observed with an average of 5 percent. Skin reactivity in rural schools was also low ex- cept for one school in stratum 1 with a prevalence rate of 22 percent. The average Table 19A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 19] % Number | Romber Rate Average Average tratum School code ihe per | antigen | control tested | positive 100 area area Urban: 1 VIBIBON vsvnms cosones putea is mEs® EI MATE £45 me Rats Saws 40 3 7.5 0.7 0.5 1 WODRABL cove viet: » mam i foi aim 4 ie 4 vo sets soil sop Tien 30 2 6.7 0.7 0.5 2 1731101 oovonmenncsmusnmavns musing sm rae ss esses wes os 39 3 7.7 0.6 0.4 4 YT20R0S woven Sollee a mi hin sisi SATA Stl ese a gnd 30 3 10.0 0.7 0.5 4 AT2UNOU coos vm 5 som ns wo 6 0 60000 1 wid Wo 3 0 5 R0IW 5 4B 30% 3 504 + 0 35 2 5.7 0.6 0.4 5 IOTHAOL ci: «vies is ah sd Gin wists st hh hat rm Abn 33 4 34 2 5.9 0.6 0.4 3 101102 vv cnvemnvgnranssar mans warsmsvasanssossvasss 35 1 2.9 0.5 0.4 Total ...... 243 16 * 0.6 0.4 Rural: 2 1252302 «oo vivs sun suv smu snsn nossa misses sues sosss 36 1 2.8 0.6 0.5 1 RABAT ives ims 55 5 ate 0.0 8000 $0.00 60.0 Abt hom ot 65 008 il 3 i 17 1 5.9 0.7 0.5 2 BISNIS on vraiment x9 5 § rob wen wet wollte ns ile a 4 AE 31 2 6.5 0.7 0.5 4 YTBOVNT coon mime monn » sie sail ov 0 5 00 0 HG 5 6000 00 4.408 3 0 3 00 6 0 19 0 0.0 0.6 0.4 3 BZD: elma old or ATi: 5 + yas ss Ha N a sc 0 4 hoot 38 2 5.3 0.6 0.4 4 1732302 ovrunvmsrmnnwseimgs mvt £005 0s HEE E6058 BETRE 32 0 0.0 0.6 0.4 5 J2BBOL vvvovnmime smn mos gms mm mons mn a wom wien som cto nw in 25 2 8.0 0.6 0.4 5 ADBIBOD vv vv women www ws om wip ns wn 8 ER nS A 16 2 12.5 0.6 0.4 5 DB2BULD oo . ; imo vim wns dine 6 00 0 4 HET $550 2 900 4 66 2 BE BS 22 4 18.2 1.0 0.5 EET ae i 2 1 +s apis os vs sid Bs et 7 5 Eli's 236 14 * 0.7 0.4 Grand Total uum uv: oo damn tum basis 55 has dies was 5iHm 479 30 * 0.7 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 54 Table 19B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 19] Type school Number Number Rate per tested positive 100 Total Total Rate number number per tested positive 100 male male Number Number Rate female female per tested positive 100 Number unknown unknown Number tested positive Stratum 1 and 2: Urban Rural Stratum 3 and 4: Urban Rural Stratum 5: Urban 109 8 7.3 52 4 7.2 57 4 7.0 —- - 84 4 4.8 37 0 0.0 47 4 8.5 — - 65 5 7 30 10.0 35 5.7 — — 89 2 2.2 44 1 2.3 45 1 2.2 - —- 69 3 4.3 33 2 6.1 36 1 23 — — 63 8 12.7 39 5 12.8 24 3 125 — - 479 30 % 235 15 *% 244 15 * - — *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 19C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 19] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years «os swsvm evs omens s sins sms 16 0 0.0 6 0 * 10 0 0.0 TOI VEBEE va hes Mas iris its 5. es’ 8 50 0 ison iin 144 14 9.7 68 9 13.2 76 5 6.6 VV years ;uonvwm somerns omonms ues s Gob EES 165 7 4.2 88 2 2.3 77 5 6.5 ATYPEETE 1. - cover nies ile is oar dopo 5 wimg tims 0 0% 96 6 6.2 51 3 5.9 45 3 6.7 13 years and over ...............iinn... 57 3 53 29 2 6.9 28 1 3.6 Age unknown ....izsssmennenn vm nme mmen 1 0 * 1 0 * 0 0 * Bota nse wes red Ered me dE 7 479 30 i 243 16 X 236 14 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 19D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 19] Length of Total Total Rate p . Number Number Rate p . Number Number Rate Percent residence number number per a urban urban per Oe rural rural per on (years) tested positive 100 PV | tested positive 100 P°*'"'V | tested positive 100 PO%"'VC Less thanl ..... 20 1 5.0 3.6 15 0 0.0 0.0 5 X % 7.1 LE IT TT 85 8 9.4 28.6 57 5 8.8 35.7 28 3 10.7 21.4 BD un vmneawenmns 84 6 7.1 21.4 51 4 7.8 28.6 33 2 6.1 14.3 10-04. .cvoiv ime s 280 13 4.6 46.4 114 5 4.4 35.7 166 8 4.8 57.1 Unknown ........ 10 2 * * 6 2 * * 4 0 * %* Toral.... cca: 479 30 * 100.0 243 16 * 100.0 236 14 x 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 55 MAP 20, AREA NG. 20 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled rural school rate was 6 percent (Table 20A). Combined prevalence for both urban and rural schools was 6 percent. Males were more re- active than females except in rural stratum 2 where the two skin reactors were females (Table 20B). Prevalence rate for 11-year-old rural and urban school children was much higher than the other age groups (Table 20C). In urban schools 38 percent and in rural schools 54 percent of the reactors resided in the area for 10 or more years (Table 20D). Low prevalence rates for bilharzia have been reported from this area (Ferguson, 1955). Weller and Dammin (1945) reported a preva- lence rate of 3 percent in Manati and 1 percent in Barceloneta. eo Area 21 is part of the Rio Grande de Arecibo river watershed with the Rio Tanama, the delta of the main river and Cano Tiburones. This watershed includes a small irrigation system as well as a complex system of canals draining a productive sugar cane area. The large delta at the mouth of Rio Arecibo furnishes an excellent habitat for A. glabratus. The land is mostly made up of limestone hills (Map 21). The total population of this area is approximately 59,000 people. There were 37 fifth grade classrooms in this area from which 12 (6 urban and 6 rural) were selected and 300 students were skin tested. A high, rather uniform, prevalence rate in urban classrooms with an average of 19 percent was observed. Except for one rural classroom which is located in a school near the river, and has a 29 percentreactivity rate, rural schools generally had low. prevalence Table 20A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 20] Number | Nomber Rate Average Average Stratum School code tested ti per | antigen | control Este POSTIVE | 100 area area Urban: 2 JOOLIOL 1 cavum ississwssn vs amas Maas FRmss wns wes mp a®vey 30 2 6.7 0.6 0.4 2 JOOL10)-2 . suuninvmsmsssvnsomss mss sms pwssmasnss wes wna 32 2 6.2 0.6 0.4 2 MABYYOL-Y ... oo «rvs oe 0 im 0 cs sp moh 0 msn os mse 6 it 8 30 1 33 0.5 0.3 2 1451100-2 .... sun ssvsnnsnussumssmsnnne sas onevnsamrannsa 30 ) 3.3 0.5 0.4 2 U4B1102 ;ouison sommes nt a@eaa vas nuns me © win 5 86 1 BEE BEE 044 40 2 5.0 0.6 0.4 Pobal aves mnsnessonnme sm oo umes mes wes Bye Heian pms 162 8 % 0.6 0.4 Rural: 1 1072302 uno somsmmines ami sds nmss sm OMI BEI FEW EMRE 28 3 10.7 0.6 0.4 1 YOT2307 vs vins sorts 5a ohn fi 68 did 4 8 ik WEB Rt itn AW ES WHE a 18 4 22.2 0.8 0.4 1 YOORNOG!. soir nino won sume £0 i» or plopmpn i bromine got eg, will 4 23 0 0.0 0.4 0.4 1 1092301 .covnnisnsnns tad BEathais EEE URE NAIRII RG RO MTRD 23 1 4.4 0.6 0.4 1 1092401 o.oo 33 3 9.1 0.6 0.3 2 ABZL05! saivvs ows sms mvs whos 56 TE amas Ws sm ER NFS FAT 3 31 0 0.0 0.5 0.4 2 YADSDATG | + siunv osvusn sion” rile Birnie 91 os om sais oo ome cscs Wie onesie beanie 34 1 2.9 0.6 0.4 2 TAB2B0) ..n.snvvonmsmvsvms smes mes sus who ses os oss ines 28 1 3.6 0.6 0.5 TOHAL co iuiaioio ommminin lw iss won sn sw i oe . c 218 13 * 0.6 0.4 GIANA TORY... os + ve wi wis wwii 5 wan 00 0 0 i rw 0 380 21 * 0.6 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 56 Table 20B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 20] [ 1 Total Total Type school number number per tested positive 100 Rate Number Number Rate male male per tested positive 100 Number Number Rate female female per tested positive 100 Number unknown unknown tested positive Number Stratum 1: Urban .............. = = = = — = = = Pe = a Rural .oisvnisvusvnis 125 11 8.8 52 8 15.4 72 3 4.2 1 0 Stratum 2: Urban .............. 162 8 4.9 70 6 8.6 90 2 2.2 2 0 RUTAL von ta tonis mann 93 2 22 51 0 0.0 41 2 4.9 1 0 i117 + | RE —— 380 21 % 173 14 * 203 7 % 4 0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 20C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 20] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ........................... 6 0 * 4 Y * 2 0 * 10 YER wo nmarwmsaminmobs 23m ue gv apim as wes 99 4 4.0 51 2 3.9 48 2 4.2 BE VBAERE . nv leis ante wl bin aed of en i oh 109 11 10.1 44 4 9.1 65 R 10.8 12 YRArS vison mursmtamssvwaa nas ssames 100 3 3.0 44 1 2.3 56 2 3.6 13 years and over ................ 00... 61 2 3.3 18 1 5.6 43 1 2.3 Age anknown ......cvcevvsvewssmvsenevie 5 1 * 1 0 * 4 1 ¥* Total sscssossmersiasmasussmusnasinss 380 21 % 162 8 x 218 13 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 20D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 20] Length of Total Total Rate Number Number Rate Number Number Rate . Percent Percent Percent residence number number per ti urban urban per ti rural rural per ti (years) tested positive 100 P%""'V¢ | tested positive 100 POSTIVE 1 tested positive 100 positive Less thanl ..... 25 2 8.0 9.5 18 1 56 12.5 7 1 % 7.7 LT Ee 78 4 5.1 19.0 29 2 6.9 25.0 49 2 4.1 15.4 BD cisarinnisase 74 5 6.8 23.8 27 2 7.4 25.0 47 3 6.4 23.1 10-14 ........... 198 10 5.1 47.6 87 3 3.4 37.5 111 7 6.3 53.8 Unknown ........ 5 0 * * 1 0 % * 4 0 * x Total.......... 380 21 ¥ 100.0 162 8 * 100.0 218 13 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 57 MAP 21, AREA NO. 21 ARECIBO 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled rates ranging from 0 percent to 7 percent. Combined prevalence for both urban and rural schools was 13 percent (Table 21A). Urban school children were considerably more skin reactive than rural school children and males more reactive than females (Table 21B). There was no increase in prevalence with age ob- served; however, the 1l-year-olds demon- strated a higher prevalence for both urban and rural school children (Table 21C), In urban schools 32 percent of the reactors have resided for 10 or more years in the area and in rural schools this figure was 90 percent. Influx of recent residence (less than 5 years) shows a skin reactivity of 29 percent in urban schools (Table 21D). Bilharziasis is known to be an urban problem in Arecibo and appears to be less endemic and absent in many rural school areas. Weller and Dammin (1945) reported a prevalence rate of 12 percent in Arecibo. e Area 22 is part of the Rio Grande de Arecibo watershed with the Rios Yunes, Limon, Saliente, Jauca, Grande de Jajuya, Caonillas, Vivi, Pellejas, and Tanama plus three lakes Lagos Dos Bocas, Garzas, and Caonillas. The towns in the area are Adjuntas, Utuado, and Jayuya. The area is a mixture of old province and rough limestone mountain terrain (Map 22), The total population of this area is approxi- mately 68,000 people. There were 67 fifth grade classrooms in this area from which 18 (4 urban and 14 rural) were selected and 456 students were skin tested. In stratum 1 a prevalence rate of 2 percent was observed in the urban area of Adjuntas increasing to 16 percent in Utuado (sub-area 2) and 24 percent inJayuya (sub-area 4); the over- Table 21A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 21] Number | Number Rate Average Average Stratum School code fod per | antigen | control tested | positive 100 area area Urban: 1 BOTIVOZ. ; civ vumnsvirammaanibn mus nase # Es Mes BF 2 60 3 99 bE wand 22 1 4.6 0.6 0.4 1 BOZTHOA os owner ih pe 0 etn is th sii wit ol soi 28 5 17.9 0.9 0.5 1 JOTUI0D: ovo inns s pusnmurassss sms ames ens sn an 32 5 15.6 0.7 0.3 1 BOZRAOG: . .... cs vn olin ron irsin mmission shine 0 ete bd ode Bi 400 23 5 21.7 0.8 0.5 1 BOTRAAT I Loc 2 coslie fprw spent wwe Banton WEA Rr Hits well dare 28 11 39.3 0.9 0.4 1 YOTIIAL .oocnmunnrvnmonnsbnmssmes iin saws s wn sum seis panes 34 4 11.8 0.7 0.4 RN ale Jule 1 tHe 4 ot Bop asses ters wom actos 167 3 * 0.8 0.4 Rural: 1 JOT2132 .vvvvrsmrsemsnussnrrmnssmennss mes smenossnrds 24 7 29.2 0.9 0.4 1 BO72UBB .uivsiwinmicomssmosis PERE TE EH LE SHS BEES 21 0 0.0 0.6 0.4 1 YOTABL: . evo sim i wmode seni 8 ow wonton fi sei aon 2. or 16 0 0.0 0.5 0.4 1 BOT2B08 «onivnmee mes sm nam now 6 a@ss ams ored wie 2 wh 230528 008 4 23 1 4.4 0.5 0.4 1 FOTDBOA: os tegen ite a msi is om css sn hel nals os wi Toes 29 2 6.9 0.6 0.4 1 TO72808. « vnvsnue vues mn swe rope pas ws peas ain 4 amas we Swe 4 20 0 0.0 0.6 0.3 ORAL ors rats la ain, moni mm rw i nc 133 10 * 0.6 0.4 Grand Boal cs io sii sass foi Hint ions v bide Si Himarsi Fo in nin’ 300 41 * 0.7 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 58 Table 21B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 21] Type school Total number number Total Rate | Nomber Number Rate | Number Number Rate | Number Number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban 167 31 18.6 83 18 21.7 84 13 15.5 - — 133 10 7.5 64 7 10.9 69 3 4.3 — - 300 41 * 147 25 * 153 16 - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 21C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 21] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years «css vrs ars pnspussmupmnsssss 10 0 0.0 7 0 ¥ 3 0 ? TO YEE .ivvnrniniBesBitmuabie GoRnEAMmETn 55 7 12.7 33 5 15.2 22 2 9.1 VL years ssussmespvrawssnismisnhssmepmwyes 112 20 17.9 55 13 23.6 57 7 123 IZ Years .coooniiiminninsimessaramernasn 59 6 10.2 33 5 15.2 26 ¥ 3.8 13 years and over ................ coo... 61 7 11.5 38 7 18.4 23 0 0.0 Age anknown sews svcr meres nmener murs any 3 1 * 1 1 * 2 0 * Total co 300 41 % 167 31 ® 133 10 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 21D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 21] Length of Total Total Rate Descent Number Number Rate p ‘ Number Number Rate p residence number number per re urban urban per on rural rural per Sent (years) tested positive 100 positiv tested positive 100 POSILIVE | ested positive 100 positive Less than1 ..... 14 3 21.4 7.3 10 3 30.0 9.7 4 0 % 0.0 1-4... 51 7 137 17.1 44 6 13.6 19.4 7 1 * 10.0 BS do vrs vis 2 953 77 12 15.6 29.3 62 12 19.4 38.7 15 0 0.0 0.0 10-04... vines 156 19 12.2 46.3 51 10 19.6 32.3 105 9 8.6 90.0 Unknown. . ; sux a 5 2 0 x * 0 0 * * 2 0 * * BEL. vars wld 300 41 ¥ 100.0 167 31 * 100.0 133 10 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 59 MAP 22, AREA NO. 22 000 — School Number * — Type of School 00 — % Infection ‘ig 2 ADJUNTAS OUrban * Rural @® Not sampled all urban school average was 18 percent, Prevalence rates were high (24 percent) in rural schools of sub-area 1, low in stratum 2 and 3 (3 percent and 6 percent), and high in stratum 4 (21 percent). This pattern indicated two focal endemic areas in the watershed (Table 22A), Combined prevalence for both urban and rural schools was 17 percent. In stratum 1 rural school students’ rates were high; in stratum 4 (Jayuya) both urban and rural school students were skin reactive. In stratum 2 skin reactivity in urban schools (Utuado) predominated (Table 22B). Preva- lence rates were high in all age groups for this area (Table 22C). Length of residence and prevalence of skin sensitivity showed that in urban schools only 38 percent of the reactors have resided for 10 or more years, and in rural schools 43 percent have resided for the same period of time. A large influx of skin reactive individuals who have resided less than five years in the area was also noted in both urban and rural schools (Table 22D). It has been known for decades that the bilharzia problem was mostly confined tourban or semi-urban streams of Utuado and Jayuya (Ferguson, 1955). The lakes in the area do not Table 22A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 22] Number | Nuriber Rate Average Average Stratum School code tested | positive | PF | 2utigen control P 100 area area Urban: 1 VOLVIOY sui vo mss 5 mons mim 5 3 000 5.00000 000 3 6 10 © $0.0 500 8 6% 5 0 41 1 2.4 0.8 0.7 2 AZVTVO2) . sisnmcmn dain sales mas mv SRE % SIRS Wins a $0003 Rv 32 5 15.6 0.8 0.5 2 NTARADDED cnc hr apes Com whieh ibn velo monger £10 1 4 deine wal gos Ao 4 30 10 33.3 1.0 0.6 4 ABBLA02 i, : vv vsnnsnnermirPee Ems 108s GAMES FREE BRI SURE BE 34 8 23.5 1.3 0.7 TBUAL 520 i scoraimmitin ase sods sass ces of obs sit: ois cot wt ges 137 24 * 1.0 0.6 Rural: 1 WOI2I30 oconusmesmmermer mrss Er ss Er EPPS A RRS 8 1 12.5 1.0 0.6 1 TANNIN ovis mn tin mons stihs Bag 5 008 Bn 53 E44 B00 008 en 15 3 20.0 0.9 0.6 1 A71213B svi mcson ome nmew wis s nonin win was wes © £3 ms Sve 23 9 39.1 1.2 0.6 1 YPA230) inves mus uma naa REm ERIE 8 HED 00 LBIGE 4040 A E00 8 28 6 21.4 1.0 0.6 1 1712306 «oo 23 5 227 i | 0.8 1 APAUPOL ; unvsmrsumsomspm is matuash Bes EERE EEE os HH EMD 28 6 21.4 1.0 0.7 2 TARTAN 220 4 5 woralin ane indiiin rile soishs # anh io Rthilbics winks We dl 0 1 eit hol 24 2 8.3 0.9 0.6 2 1712802 suis murwnsmaspuiswssssssmannepnrhusawnswrns 34 3 8.8 0.8 0.6 3 1192302 .iicisnmsnbasms emer mmass 88s aes mes vies bids sil s 28 2 731 0.7 0.5 3 BBB... rs: War he 4 sin of el Boi tind ew ee core rsd sd 30 0 0.0 0.8 0.7 3 712122 nisms amv sms REIS RRMA TWF A ME SEE ATE BE 12 2 16.7 0. 0.6 4 1362104 17 2 11.8 0.9 0.6 4 AB62Y00 ..svonusnmismsnmasmusams sess was iwnewes ensnss 26 11 42.3 1.5 0.7 4 ABODE i. viii in 4 ein id Ff as Wt hs. i 8 406 2 BR 23 1 4.4 0.8 0.7 Total ...u:runsnmssnes isomssmmsimpsmesvweswrssnsnds 319 53 iu 0.9 0.6 Gronditotal ,. vu uivvmsmnsemrsmrsrast mus awssn Eons nas 456 77 * 0.9 0.6 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 60 Table 22B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 22] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban us oons vn s nme vi 41 1 2.4 20 0 0.0 21 1 4.8 - = Rural :snsvemsamune 125 30 24.0 75 20 26.7 50 10 20.0 - - Stratum 2: Urban =:om cs mes amass 62 15 24.2 30 10 33.3 32 5 156 — — Baral o.en sams sommes 58 5 8.6 23 2 8.7 35 3 8.6 —- - Stratum 3: Urban =. ou wns vm en - — — — - —- —- — — - - Rural ».osaismsrmess 70 4 5.7 38 3 7.9 32 1 3.1 — —- Stratum 4: Urban =«:o.rmwrsmess 34 8 23.5 19 5 26.3 15 3 20.0 — —- Rural .............. 66 14 21.2 32 9 28.1 34 5 14.7 —- - Total sos emassmssn 456 77 x 237 49 219 28 * —- —- *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 22C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 22] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 Years c..:ou-omesnsiowsim: bm sameis 2 1 * 0 0 * 2 1 * HOYears ms oie oi dvi si on Bish’ ov omg vas 66 10 15.2 23 4 17.4 43 6 14.0 BU VCATE 152 «we waren 0000 5b 40 8 4 hobo # 05th 50 163 27 16.6 54 12 22.2 109 15 13.8 I YOAPS vv virns rims mornin wien ms np we wane nm 114 17 14.9 39 4 10.3 5 13 17.3 13 years and over ....v:soswssmussmaru nas 109 22 20.2 20 4 20.0 89 18 20.2 AGE QRKAOWA «vrs sss ems tt vnmm smn s amsnms on 2 0 * 1 0 * 1 0 * Botal coins mntims dm 55 wee mds wot Loe La 456 77 * 137 24 * 319 53 % *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 22D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 22] Length of Total Total Rate Number Number Rate Number Number Rate . Percent Percent Percent residence number number per ti urban urban per Feive rural rural Per itive (years) tested positive 100 POSIIVE | tested positive 100 posifry tested positive 100 P Less than1 ..... 21 3 143 3.9 9 1 * 4.2 12 2 16.7 3.8 bed on corr vim: 105 21 200 27.3 43 6 14.0 25.0 62 15 24.2 28.3 BD ene cmt orld Red 100 21. 21.0 272.3 37 8 21.6 33.3 63 13 20.6 24.5 10-24 ,..0c0nis me 220 32 15 486 45 9 200 37.5 175 23 13.1 43.4 Unknown ........ 10 0 * % 3 0 * * 7 0 * * Total: vss swsnus 456 77 x 100.0 137 24 * 100.0 319 53 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 61 appear to be involved in the transmission. Weller and Dammin (1945) reported a preva- lence rate of 36 percent in Utuado, 37 percent Jayuya, and 48 percent in Adjuntas. Maldonado and Oliver-Gonzalez (1958) reported rates of 8 percent in Utuado (21 percent in 1953) and 17 percent in Jayuya (6 percent in 1953). White, Pimentel and Garcia (1957) reported 23 percent in Jayuya and Faust et al. (1934) reported 41 percent in the Utuado area. Our data confirms most of these observations. eo Area 23 comprises one watershed con- taining the Rios Canas, Portugues, Pastillo, Chiquito, Bayagan, Guayo, San Patricio, Cer- riollos, and Inabon; Quebradas Indalecia, Poncha, Limon, and Agua. Several farm ponds are called collectively Lagos Poncena. There were no large lakes or major irrigation canals. The area has relatively little flat land but is a mass of rugged hills. High gradient streams subject to numerous annual floods make the area generallyunfit for a A. glabratus. The area contains one large city, Ponce (Map 23). The total population of this area is approximately 152,000 people. There were 93 fifth grade classrooms in this area from which 18 were selected (8 urban and 10 rural) and 505 students were skin tested. Endemicity both inurban and rural schools was low. In stratum 1, rural rate of 10 percent (in stratum 1) was obtained due to a high prevalence of skin reactivity (21 per- cent) in one school (Table 23A). Combined prevalence for both urban and rural schools was 5 percent. Skin reactivity for both male and female students in urban and rural schools were almost equal except for rural stratum 1 (Table 23B). It is noted that rural school males in stratum 1 were much more skin reactive than any other group. The informa- tion on distribution of positive skin reactors by age and type school indicated no change in skin reactivity with increased age (Table 23C). Length of residence and prevalence of skin Table 23A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 23] Number | Number Rate Average Average Stratum School code wsted | positive per | antigen | control 100 area area Urban: 2 AB6YTLY Luin vu uimrvimss wm sn os iss oe 89 + 84 8 B00 Sow © § wg awe 35 2 5.7 0.6 0.4 2 IBBULYD ven viw v woww no wim nm cow wm nom com om cows om 3604 3 4 32 0 0.0 0.5 0.4 2 YSOYYTY nov viv v0 mn 5 orn 030 v0 53 08 30 50 ss de Ws wr 0 Som wv 5 wie ioe 37 3 8.1 0.7 0.5 4 IBBLIDD ..vvniiidms mn som sma RSG 0 7 EAS HS DY SURES TE 3 34 2 5.9 0.6 0.4 4 1561106 . .. oa 40 1 2.5 0.6 0.4 4 YBOYYOT vivo ion vims wives sd 97655 wins 58 £55 #3 0% #903 300 8 30 8 gi 31 1 3.2 0.6 0.4 4 NBOYNNS: cs co cient oie tedcnsin ts wre scene Yok wg ir bn, Soir ccs nhs of 39 1 2.6 0.7 0.5 4 1561104 oo 36 2 5.6 0.7 0.5 gr TTI IL 284 12 * 0.6 0.4 Rural: i} 1372120 oe 16 0 0.0 0.7 0.5 1 YB02U0 ; ic iin ic vne som oa 5 § IE 6 RES SI 4 2505 $55 S04 BEY 85 2 4s 38 3 7.9 0.7 0.5 1 NSBTUTOE . trove victors wc rics shies 6 co cvs we vdeo hn es i'n ATi i 10 0 0.0 0.8 0.6 1 1 28 6 21.4 0.9 0.6 2 IBB2UDA cov nriimii snr snd BRIAR ETA A PFET RITES TEE 31 1 3.2 0.6 0.5 2 YBBILBB: ov v vim wi wir osm 0 1 we nc io 0 rn om 0 5 9 oc i ch 8 0 0.0 0.7 0.6 2 YSBDNDT vs mms voi 505 5 S00 6 8 00 2 RAE Ee 5 WEE SE BEBE SE A 11 0 0.0 0.8 0.5 2 1562145 ee 24 2 8.3 0.7 0.5 4 YSOZADY vie 5 wie 5 mie mim bob 5% © GEOR 5 6 0 008 S00 BER 4 6 0 § 6 We 4 26 0 0.0 0.6 0.5 4 ASETIOD . ..ces «f ton GF IND it ws to is ioe em BE 29 1 3.4 0.6 0.4 Tota] . ov cove v wivin wium wi 5 0 00 vivre wie vw kw ee gS 221 13 %* 0.7 0.5 Grandtotal ............... ccc 505 25 de 0.6 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 62 MAP 23, AREA NO. 23 000 — School Number * — Type of School 00 — % Infection O Urban * Rural ® Not sampled sensitivity data indicated that in urban schools 83 percent of the reactors have resided for 5 or more years, and in rural schools 77 percent (Table 23D) have done the same. Bilharziasis has not been a significant problem in recent decades in this watershed (Ferguson, 1955). Weller and Dammin (1945) reported a prevalence rate of 4 percent in Ponce and White; Pimentel and Garcia (1957) reported a rate of 0.3 percent. ® Area 24 comprises three watersheds with the Rios Tallaboa, Guayanilla, Yauco, Gua- yanes, and Loco. Lagos Luchetti and Loco are large impoundments of the Lajas Irrigation District. The towns located in this watershed are Penuelas, Guayanilla, and Yauco. The Table 23B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 23] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per |unknown unknown tested positive 100 | tested positive 100 | tested positive 100 tested positive Stratum 1: Urbans sun's» wil s wir 's wees ae - - - - — - -— ~ = = Bural ..c.smasame swe 92 9 9.8 47 6 12.8 45 3 6.7 - —- Stratum 2: Urban vn esnss ems ony 104 5 4.8 47 4.3 57 3 5.3 — - Rural .......c00s00s 74 3 4.1 36 1 2.8 38 2 5.3 — — Stratum 3: Uban coe eomis eves wn - - - - - — - - - - - Bural ou coecnomecnns - - - - - - —- —- - —- - Stratum 4: Urban ......cc0vvnn. 180 7 3.9 92 4 4.3 88 3 3.4 — - Bural suomasmmssnes 55 1 1.8 31 1 3.2 24 0 0.0 - - Total oven. 505 25 % 253 14 3 252 13 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 23C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 23] Total Total Rate number number per tested positive 100 Number Number Rate urban urban per tested positive 100 Number Number Rate rural rural per tested positive 100 Under 10 years 10 years 11 years 12 years 13 years and over Age unknown i kt sell ce mors 2 0 * 2 0 * 0 0 ¥ PI TTT T" 92 4 4.3 59 ¥ 1.7 33 3 9.1 fst ew orem eee 183 9 4.9 106 6 5.7 77 3 3.9 3 WR I SR 133 7 5.3 73 4 5.5 60 3 5.0 2 NA olde A B ch + BOAT 93 5 5.4 42 1 2.4 51 4 7.8 3 HIER EAT RR Te wy 2 0 * 2 0 % 0 0 * os id rics 9% A in oer 505 25 * 284 12 * 221 13 i *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 63 Table 23D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 23] Length of Total Total Percent Number Number Rate p . Number Number Rate p ’ residence number number salt B urban urban per ed rural rural per Sa (years) tested positive 100 positive tested positive 100 POSIIVE | ested positive 100 Positive Less thanl ..... 25 1 4.0 17 1 5.9 8.3 8 0 * 0.0 I-A iii 125 4 16.0 83 1 1.2 8.3 42 3 7:1 23.1 1 Sp 103 5 20.0 56 3 54 25.0 47 2 4.3 15.4 10-14 ........... 243 15 60.0 127 7 5.5 58.3 116 8 6.9 61.5 Unknown ........ 9 0 * 1 0 # * 8 0 ¥ * Total. ......... 505 25 * 100.0 284 12 * 100.0 221 13 ¥ 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. area is primarily roughly mountainous with a limited coastal alluvial plain. The total pop- ulation of this area is approximately 69,000 people (Map 24). There were 66 fifth grade classrooms in this area from which 17 were selected (7 urban and 10 rural) and 458 students were skin tested. In urban schools prevalence rates were generally low (0 percent-7 percent) except for one school which had a prevalence of 14 percent. The average urban school prevalence rate was 4 percent. In rural schools prevalence rates ranged from 0 percent to 27 percent, with an average of 10 percent (Table 24A). MAP 24, AREA NO. 24 000 — School Number * — Type of School 00 — % Infection © Urban * Rural ® Not sampled Combined prevalence for both urban and rural schools was 9 percent. Rural school children were considerably more skin reactive than urban school children, and very little dif- ference in prevalence rates between male and 64 female individuals was observed (Table 24B). Prevalence rates were low in the 10-12 year category and rose sharply in the 13 year and over group (Table 24C). In urban schools 62 percent of the reactors have resided for ten or more years and in rural schools 60 percent (Table 24D) have done the same, Bilharzia is known to be lightly endemic in this area (Ferguson, 1955). Weller and Dammin (1945) reported prevalence rates of 2 percent in Penuelas, 1 percent in Guayanilla and 3 percent in Yauco. e Area 25 is part of the Rio Anasco water- shed with the Rios Prieto and Blanca and the Lagos Yahuecas, Guayo, Toro, and Prieto which serve as the source of the Lajas Ir- rigation District. Communities are small (map 25), and the great majority of them are located at high levels from the water bodies due to the precipitous and sudden rise of MAP 25, AREA NO. 25 000 — School Number * — Type of School 00 — % Infection QO Urban * Rural ® Not sampled Table 24A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 24] Number |. Number Rate Average Average Stratum School code or per | antigen | control tested | positive 100 area area Urban: 1 XSBUAOLEL wo be sis: w somin ts omen Shri wid ho or ns se so spy is on vgs WP 35 5 14.3 0.8 0.4 1 EBB =D. cc i ies vf nis se so in mas beet kien 5 im of 42 wis es wom 29 0 0.0 0.6 0.4 2 ABOVVLD: ons rvs iv 45 50m 0 vw vp 5.50000 WE G80 2 WISH LF 4 10 8 HEY EAE 23 0 0.0 0.6 0.4 2 1201120-1 Loe 28 2 7.1 0.6 0.4 2 YI0V120-2 . s vvs mn emmns mes mus ens wok sed 5% E BW LEE 088s HOE 29 0 0.0 0.5 0.4 3 BZTLNO AN oc 1.55055: 55 Goo i de sis Fie es ts be 0 sere Sn 29 1 3.4 0.6 0.4 3 1771100-2 34 0 0.0 0.5 0.4 TOUEY. ts wm 02 055 5008 205 8 Ros £3 500 & ee 2 mn foie 4 a es 0 9 207 8 * 0.6 0.4 Rural: 1 1552109 oo 27 4 14.8 0.6 0.3 2 LOTT 5 v5 5 i 5555 5505 5 dl 0 5 8 1 cm 0 8 he hit 8 23 0 0.0 0.6 0.4 2 L2O2BO. ois rv iin «wi i cows 3% wi evn we 3 0 08 0 1 6 4) 8 22 0 0.0 0.6 0.4 2 ABBOT wins am snimss me sms bie ds BE EER FR MEE BURSTS BESS 25 2 8.0 0.6 0.5 3 1702000 ovrrrermrr nner rm een se 19 0 0.0 0.6 0.5 3 YEARNS vcs paws Tow EE ns VET SAR WR WEE ATE EE 25 0 0.0 0.8 0.6 3 ER BL 0 a ie 0.05 2 0c ae os bl ls cv 16 eb 0 0s on SI 15 2 13.3 0.7 0.5 3 1772802 viii trae rasa se EE Se se eee 34 9 26.5 1.1 0.6 4 LA 25 0 0.0 0.5 0.4 4 LTT 20S: co: « sons ss svn ss 0 ws ee £0 4 9 8 0 BF 3 Sr 36 8 22.2 1.0 0.6 TORE ins 0 00 0 000 3 05 0 WE 50 6 its es cvs te ts 251 25 % 0.7 0.5 Grand total ............... 458 33 % 0.7 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 24B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school (Watershed area 24) Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per [unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: PBR asin vw vas wits 64 5 7.8 30 2 6.7 34 3 8.8 — —- Rural .............. 27 4 14.8 11 2 18.2 14 2 14.3 2 0 Stratum 2: Urban .............. 80 2 2.5 34 0 0.0 45 2 4.4 1 0 Burl wasnt imis ms 70 2 2.9 32 2 6.2 38 0 0.0 2 - Stratum 3 Urban «5.6 sins si sae 63 1 1.6 30 0 0.0 33 1 3.0 - - RurBL i. ie» wos 4 non 9 93 11 11.8 55 7 12.7 38 4 10.5 - — Stratum 4 Urban .......vvvunn. ~ - - - - = - = - - - Rural Fo; voto munis 2 swe vi 61 8 13.1 24 3 12.5 37 5 13.5 —- - Total cu vse sui sna 458 33 * 216 16 % 239 17 %* 3 0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 65 Table 24C. Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 24] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ...........ccovvvnnnnnnnn... 16 0 0.0 11 0 0.0 7 0 10 years ........ooiiiiiiiiniiiii 126 7 5.6 44 2 4.5 82 5 6.1 VE SEOBEE 006m se 0s 5 Fe 5 mse id Bs. Bei 133 10 7.5 61 1 1.6 72 9 12,5 12 YEAS wu cw ss wwe min 6 8 wiv g wie 5 apn mus way own 112 5 4.5 53 1 1.9 59 4 6.8 13 years and OVE :sussmesmsrnassmennes wus 68 11 16.2 36 4 11.1 32 7 21.9 Age unknown ......... o.oo 3 0 % 2 0 * 1 0 * Total :cusinisomasnormsinusmnssmssnss 458 33 * 207 8 * 251 25 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 24D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 24] Length of Total Total Rate Number Number Rate Number Number Rate : Percent Percent Percent residence number number per iti urban urban per tive rural rural per osltive (years) tested positive 100 positive | rested positive 100 posit tested positive 100 P Less than1 ..... 34 2 59 6.1 17 2 11.8 25.0 17 0 0.0 0.0 4c ivninussmes 79 4 5.1 12.1 46 1 22 12.5 33 3 9.1 12.0 BD i oro conn i 80 7 8.8 2.2 35 0 0.0 0.0 45 7 15.6 28.0 VOX4 osuinv simi 253 20 7.9 60.6 103 5 4.9 62.5 150 13 10.0 60.0 Unknown ........ 12 0 * * 6 0 * * 6 0 * * Total. ....c552: 458 33 * 100.0 207 8 * 100.0 251 25 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. water levels in this area. The area consists of rugged mountains. The total population of this area is approximately 16,000 people. There were 15 fifth grade classrooms in this area from which 5 rural classrooms were selected and 88 students were skin tested. Prevalence rates from 0-7 percent were observed in this watershed area. Average prevalence for rural schools was 4 percent (Table 25A). A total of three skin reactors— all boys—was found (Table 25B). Two of the boys were 11 and one was 13 years of age (Table 25C); and they had resided in the area over 10 years (Table 25D), eo Area 26 comprises three large water- shed with the Rios Camuy, Guajataca, Cule- brinas, and Sonador and Lago Guajataca. The urban areas are Aguada, Aguadilla, Moca, 66 Isabela, San Sebastian, Lares, Quebradillas, Rincon, Camuy, and Hatillo (Map 26). The study area is about half limestone and old province alpine terrain and half flat land. The total population of this area is approximately MAP 26, AREA NO. 26 000 — School Number * — Type of School 00 — % Infection ® Not sampled Table 25A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 25] Nunbier) Number Rate Average Average Stratum School code tor per | antigen | control tested | positive 100 area area Rural: 1 TOUTING «src wm vv nw mins 39m» wow 0.5 900 68 55 9 3 Sons 4 00 wens wpm 3 wine 15 1 6.7 0.8 0.6 1 YA0ZI26 ..vosmumvsmompsinimssmosans sess @eosdsssnmesanss 14 1 7.1 0.7 0.6 1 VAOTYRD .. oes 1 vivo ou mtn & i dit Sai 3 SHIA BEL HE I AS BN TR WES 22 0 0.0 0.7 0.6 1 YAOIBOT en's 7.55 5.5 52 3% 8 90% 597077 S0.5.955 7 5 570 £8 7% Fw EF Wy. 24 1 4.2 0.7 0.6 1 YZT2LLB or cvromm mmm nam ns mnie bed RAFAH EI EIS PARE TRE 13 0 0.0 0.6 0.5 Grand total ............ i 88 3 % 0.7 0.6 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 25B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 25] Total Total number number Type school per tested positive 100 Rate Number Number Rate male per tested positive 100 male Number Number unknown unknown tested positive Number Number Rate female female per tested positive 100 Stratum 1: Urban ....eonvvunne. = — - — = - - —_ — a - Bural vues ems ome wes 88 3 3.4 30 3 10.0 57 0 0.0 1 0 Total vv wou v vs ene 88 3 * 30 3 % 57 0 % 1 0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 25C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 25] Total number number tested positive 100 Total Rate | N per urban tested positive 100 Number Number Rate rural ~~ rural per tested positive 100 umber Number Rate urban per Under 10: years wus uss mesons mmeswsmss wma 0 0 * - - - 0 0 * AB VEBATE! vs sion was wir «om in + + sos imi 11 0 0.0 - —_ - 11 0 0.0 1] years: ooeum es wim nnnmy mmr ome vw vy we ne rss 18 2 11.1 - - - 18 2 11.1 12 years o.oo. 32 0 0.0 - - —- 32 0 0.0 13 yearsand over ............. coin... 27 1 3.7 — —- - 27 1 3.7 Total. .....oovii 88 3 % - — - 88 3 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 67 Table 25D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 25] Length of Total Total Rate Number Number Rate Number Number Rate residence number number per Percent urban urban per Percent rural rural per Percent (years) tested positive 100 positive | ested positive 100 POSILIVE | ested positive 100 positive Less than1 ..... 5 0 ® 0.0 —- - — —- 5 0 * 0.0 1d oi cnmminn 6 0 % 0.0 - - —- - 6 0 % 0.0 Bel vias iw ssmunmss 3 0 * 0.0 - —- — —- 3 0 * 0.0 10-14 ........... 72 3 4.2 100.0 _— - —- - 72 3 4.2 100.0 Unknown ........ 2 0 * * ic = —_ - 9 0 * * Total. ounssums 88 3 * 100.0 - - = = 88 3 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 240,000 people. There were 188 fifth grade classrooms in this area from which 28 were selected (12 urban and 16 rural) and 706 students were skin tested. The overall urban school prevalence rate was 5 percent. Rural schools in stratum 3 had a prevalence rate of 13 percent and in stratum 8 a rate of 11 percent. In other watershed strata, prevalence was much lower, ranging from 0-18 percent (Table 26A). Combined prevalence for both urban and rural schools was 6 percent. The distribution of positive reactors by sex, type school, and watershed stratum showed a mixed pattern. There was very little difference between prevalence rates for the sexes. The highest rates were obtained in the rural schools strata 3 and 8, and in the urban schools stratum 4 (Table 26B). The distribution of positive skin reactors by age and type school indicated uniformity between the age groups tested except for rural school children in the 13 year and over group from which 10 percent were reactive (Table 26C). In urban schools 50 percent of the reactors have resided for 10 or more years in the area and in rural schools 55 percent (Table 26D). Bilharzia appears to be lightly endemic in parts of this study area and may be influenced greatly by the influx of individuals from other parts of the island. Weller and Dammin (1945) reported prevalence rates of 1 percent in Moca, 2 percent in Aguadilla, 6 percent in Isabela, 3 percent in Quebradillas, 2 percent in Camuy, 2 percent in Hatillo, 4 percent in Lares and Rincon, and 10 percent in San Sebastian. Their overall average prevalence rate for the 10 towns was 4 percent, White, 68 Pimentel, and Garcia (1957) obtained a rate of 0 percent in Quebradillas. Our overall rate was 6 percent for these urban and rural schools. e Area 27 is part of the Rio Anasco water- shed with the Rios Canas and Guaba. The urban areas are Las Marias and Anasco (Map 27). The area is steeply ridged with a limited MAP 27, AREA NO. 27 000 — School Number * — Type of School 00 — % Infection O Urban * Rural @® Not sampled coastal alluvium plain. The total population of this area is approximately 36,000 people. There were 42 fifth grade classrooms in this area from which 14 were selected (4 urban and 10 rural) and 344 students were skin tested. Prevalence rates in urban schools ranged from 10-26 percent. The average urban school rate was 16 percent. In rural schools preva- lence rates were lower, ranging from 0 per- cent to 8 percent (Table 27A)., The average rural school rate was 4 percent. Combined prevalence for both urban and rural schools was 6 percent, Urban school males in stratum Table 26A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 26] Number | Number Rate Average Average Stratum School code a: per | antigen | control tested | positive 100 area area Urban: 1 YOSNNON ios vinn nt onto wii oo may Su ave 2% BI 000 Sire 4 SEN 4 £ Ts 38 2 5.3 0.6 0.4 2 10B1T00 .uvvvismssmiimisRussaismsbne isms massBesmes nes 18 0 0.0 0.6 0.4 2 1031103 Lo 30 2 8.7 0.7 0.4 2 T401I01 icv vmmammunmivs sims simusim ep iins sme isdn mas® games 30 2 6.7 0.7 0.5 3 ABTA, 1 ois oti de 00 Br RE 7 od en Td ht Bs i 34 2 5.9 0.6 0.4 3 1351100-2 . 30 2 6.7 0.6 0.4 4 YOBUYDL, oc ves svn sr. i ci i eB i 9 2 vor ay 36 5 13.9 0.8 0.3 5 VAOLTON. 1s 5m viel ost be sl bbe voi vos ed ae oi is moms gpl ni 30 0 0.0 0.5 0.4 5 Ei eT Tl TTT 32 0 0.0 0.5 0.4 6 1141101 oe 25 0 0.0 0.5 0.4 6 ABTLYON oivvuv oman ewmns wi hom sss so nme Ges om 4 ese 0 Es wed 30 2 6.7 0.6 0.4 8 ABFTATHIN. 1 vari be oi i se 8 tl sos Ss iro + ie a ots ns 0 3 ee 28 1 3.6 0.5 0.3 TOMA eee eee eee 361 18 «| 06 0.4 Rural: 1 1582107 Li ee ee eae 17 0 0.0 0.5 0.4 1 1582109 oe 13 0 0.0 0.6 0.5 2 102230 sini vim s wis won’ iors 5 5 1 45% 5 00 BREE 4 RIES WEE BIE 34 0 0.0 0.5 0.4 2 LOOT ih 1% 0 5 Rr i Bel Pid 8 cl © lh 6 os WE ie ee a re th 19 2 10.5 0.7 0.5 3 1032302 oi 31 3 9.7 0.8 0.4 3 13B2VN0 oo ims i mes ma nai os Sm aS oa md § 55 750 5 Eran ooh Bow me mn 16 3 18.8 0.7 0.4 3 TARDE ct is chin sind es oe ss ow of st hd vi oo 8 28 4 14.3 0.6 0.3 4 1662133 oe 29 0 0.0 0.4 0.4 4 1OB2UBO. ivi vn im bmw mom mm 3 0 50s #030 8 9% 50 4 cs cr 1 5 8 22 0 0.0 0.5 0.4 4 XOBBTOS, ori vn 5 vin ve wr 0 wird 3 ob 0 090 0 2 SE TD © LE 25 0 0.0 0.5 0.3 5 1IA2900. svnv nis ats srs bos nea moins BIB RMETH EL HES Mak bus 11 2 18.2 0.9 0.4 6 1142104 oe 9 0 0.0 0.7 0.4 6 1182105: omc mos sv snmrnr ss omes oss sms osm es nes owes ns 19 1 5.3 0.7 0.4 7 YO DTNOD: ims it 0d SREB i BRS Bod 8 os ed #4 ss 25 0 0.0 0.6 0.4 8 1072130 Li 17 0 0.0 0.5 0.4 8 1B22UN4 oivomimsinsommamme vm sss vn dinss wssie sig sod ass ms 30 5 16.7 0.7 0.4 Total .... 345 20 * 0.6 0.4 Grand total ............ 706 38 x 0.6 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 69 Table 26B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 26] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 tested positive Stratum 1: I TT 38 2 5.3 19 1 5.3 19 1 5.3 - - Rural .............. 30 0 0.0 15 0 0.0 15 0 0.0 - - Stratum 2: Urban .............. 78 4 5.1 42 3 7.1 36 1 2.8 — - Bural .ouvwvinmssnes 53 2 3.8 25 2 8.0 28 0 0.0 - — Stratum 3: Urban .uivwssswsnnss 64 4 6.2 26 1 3.8 38 3 7.9 - — Ruta] cv con swine win in 75 10 13.3 44 7 15.9 31 3 9.7 — - Stratum 4: Urban cv.snisaninnis 36 5 13.9 17 2 11.8 19 3 15.8 - - Rural .............. 76 0 0.0 40 0 0.0 36 0 0.0 - — Stratum 5: Urban .............. 62 0 0.0 26 0 0.0 36 0 0.0 - - Rural .............. 11 2 18.2 7 2 * 4 0 * - - Stratum 6: Urban .............. 55 2 3.6 33 1 3.0 22 1 4.5 — - Bural oivwesmmenies 28 1 3.6 12 1 8.3 16 0.0 - - Stratum 7: Urban cs :omisnmsmmns — - - - —- —- - - _ - — Bural ..:ss-smisamis 25 0 0.0 12 0 0.0 13 0 0.0 -— - Stratum 8: Urban vosvvismssvsas 28 1 3.6 17 0 0.0 11 1 9.1 —- - Rural .............. 47 5 10.6 22 3 13.6 25 2 8.0 - - Total. cosvsiisass 706 38 %* 357 23 ¥ 349 15 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 26C.—Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 26] Age Total Total Rate number number per tested positive 100 Number Number Rate urban urban per tested positive 100 Number Number Rate rural per tested positive 100 rural Under 10 years ............coovvvinnn.... 10 years 11 years 12 years 13 years and over 33 1 3.0 24 1 4.2 9 0 * 175 12 6.9 90 8 8.9 85 4 4.7 215 8 3.7 110 2 1.8 105 6 5.7 153 8 5.2 66 4 6.1 87 4 4.6 130 9 6.9 71 3 4.2 59 6 10.2 706 38 * 361 18 * 345 20 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 70 Table 26D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 26] Length of Total Total Rate Number Number Rate Number Number Rate residence number number per Pocans urban urban per Boom rural rural per Poent (years) tested positive 100 POSILVE | tested positive 100 POSTIVE | ested positive 100 postive Less thanl ..... 35 3 8.6 7.9 21 1 4.8 5.6 14 2 14.3 10.0 4 vwrsnsinwiin 107 7 6.5 18.4 74 3 41 16.7 33 4 12.1 20.0 DED he sin shins: nd 135 8 59 21.1 76 5 6.6 27.8 59 3 51 150 10-04 cuunsniesa 423 20 4.7 52.6 185 9 49 50.0 238 11 46 55.0 Unknown ........ 6 0 * * 5 0 ¥ * 1 0 * * Toral..n.somins 706 38 * 100.0 361 18 * 100.0 345 20 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 3 were most skin reactive (Table 27B) and urban 10 to 12 years old students were the reactive age groups (Table 27C). In urban schools only 33 percent of the reactors re- sided in the area for ten or more years, and in rural schools 55 percent resided for the same period of time (Table 27D). Bilharzia is known to be lightly endemic in this study area (Ferguson, 1955). Weller and Dammin (1945) reported prevalence rates Table 27A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 27] Number | Number Rate Average Average Stratum School code 253 per | antigen | control tested | positive 100 area area Urban: 2 TA11I0) Givmsnvismismesm snes Mats SE ums BBs ORs REELS 29 3 10.3 0.9 0.6 3 YOOLIOZ-L. «vv vivivnn ovmoe v5 evn vo won s 500 3 ims 3 vw © 00 #0 60m is 0 ov 0% 27 7 25.9 0.8 0.3 3 YOBLIOD-D vv sumvmms vives mms Sms nm saws vais 6058 we 5 5 4 Gas 27 3 11.1 0.6 0.4 3 1061102-3 oe 15 3 20.0 0.8 0.5 5 LE 98 16 * 0.8 0.5 Rural: 1 1412302 © oo 25 2 8.0 0.9 0.6 1 GANT » swims vnsaliis mn iru imi B rs ORL H CE TR TEs Wu 28 0 0.0 0.8 0.7 2 1062017 .iincrimitmeniii ais misisspR sims nis Basu Es mds 15 0 0.0 0.5 0.3 2 1412007 eee 13 0 0.0 0.7 0.6 2 482300=) wo ovnvrnmuomns wins mss mss messy ues sime Bess oes 35 2 5.7 0.5 0.4 2 BAS ri i th on 050: 2 hate bs fds © 0 se sho of fe es awd hal fe id af 40 3 7.5 0.6 0.3 3 1062109 . oo 14 1 71 0.5 0.3 3 YOBZIDT oviiioi oon 65.6 5 5 £5 Bik 2 Sod 5.5 00 § Grit 60 nds § 00 6 8 Bl § i © 24 2 8.3 0.7 0.5 3 BOBBIN: nis vf iminis wrtel sh so ok wis 2 mim Soko snp, ir of ves Boo sn we be in 27 0 0.0 0.7 0.5 3 1062302 csi snmonmn ums Sues mat Bete sess hme wks ons Bs 25 1 4.0 0.6 0.4 BBERL, crc wc le oi dsl dozer #00 0 Bh ie an se aes Eee 246 11 * 0.7 0.5 Grand total ...........cc.iiiiiiii 344 27 * 0.7 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 71 Table 27B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 27] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per [unknown unknown tested positive 100 | tested positive 100 | tested positive 100 tested positive Stratum 1: Uibam uo sws sw snivss - - -— -— - — - - -— - - Baral co. oot nti sista » 53 2 3s 30 1 3.3 23 1 4.3 - —- Stratum 2: Urban .............. 29 3 10.3 22 3 13.6 7 0 * - - Rural ouvrnssamronse 103 5 4.9 49 3 6.1 54 2 3.7 - - Stratum 3: Urban .............. 69 13 18.8 27 7 25.9 42 6 14.3 - —- Rural :onsumssasanes 90 4 4.4 51 4 7.8 39 0 0.0 - - Total ............ 344 27 * 179 18 % 165 9 ® - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 27C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 27] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ...........ooviiiniiinnn... 7 1 * 1 1 * 6 0 * YO VEArS: sic sniv sows ons ness wa 4 59 5 aks S58 Las 91 4 4.4 925 3 12.0 66 1 1.5 LL VOATS: ir 2 nes im pinion = vim & oy i cig 50 112 10 8.9 41 6 14.6 71 4 5.6 12 YEATES: «nu som sn nes 5 vom 8 Lon 20a 7 ei 5 5 4 79 8 10.1 19 6 31.6 60 2 3.3 13 years and over .................ii.i... 52 4 7.2 11 0 0.0 41 4 9.8 Age unKIOWN ws: nssmesmmsvwrsmasnss bos vms 3 0 % 1 0 ® 2 0 % Total ..........c.oiiiiiiiiii iin 344 2% * 98 16 ” 246 11 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 27D.—-Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 27] Length of Total Total Rate Number Number Rate Number Number Rate : Percent Percent Percent residence number number per ti urban urban per ti rural rural Per sitive (years) tested positive 100 POSILIVE | tested positive 100 POSTIVE | tested positive 100 P Less than1 ..... 19 4 21.1 15.4 6 1 % 6.7 13 3 23.1 27.3 Tein ciinmiin e wivna 79 5 6.3 19.2 21 5 23.8 33.3 58 0 0.0 0.0 A , 73 6 82 231 20 4 20.0 26.7 53 2 3.8 18.2 10-14 .umsnvnrn 164 11 6.7 42.3 46 5 10.9 33.3 118 6 5.1 54.85 Unknown ........ 9 1 * * 5 1 * * 4 0 * * Total.......... 344 27 * 100.0 98 16 * 100.0 246 11 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 72 of 0 percent in Las Marias and 26 percent in Anasco. Their average prevalence rate for these cities was 16 percent. White, Pimentel and Garcia (1957) reported a prevalence of 3 percent for Anasco. We found a skin reac- tivity rate of 9.5 percent for Anasco and 6 per- cent for Las Marias. ® Area 28 comprised one watershed, that of the Rio Yaguez which flows through the city of Mayaguez (Map 28). The area is mostly MAP 28, AREA NO. 28 000 — School Number * — Type of School 00 — % Infection 103 01 107, 49 55 12 © o 105 1oo® 9,092 4 12 6 MAYAGUEZ O Urban * Rural @® Not sampled mountainous with a flat urbanized plain. The total population of this area is approximately 63,000 people. There were 39 fifth grade class- rooms in this area from which 10 were selected (7 urban and 3 rural) and 281 students were skin tested. Prevalence rates varied from 0 percent to 55 percent in urban schools (average 19 per- cent) and from 0 percent to 14 percent in the 3 rural schools (average 6 percent) Urban school children were much more re- active than rural school children (Table 28A), Combined prevalence for both urban and rural schools was 18 percent. The urban school males were considerably more skin reactive than the other groups tested (Table 28B). Prevalence rates in 10- and ll-year-old students were lower than in 12 and 13-year- old individuals (Table 28C). In urban schools 37 percent of the reactors have resided for 10 or more years in the vicinity, and in rural schools 67 percent have done the same (Table 28D). Faust et al. (1934) reported a prevalence rate of 10 percent in the Mayaguez area and Weller and Dammin (1945) 11 percent. Our data indicated a 15 percent skin reactivity rate for Mayaguez. ° Area 29 comprises one watershed, that of the Guanajibo river with its tributaries the Rios Rosario, Hoconuco, Cupeyes, and Flores, and the urban areas of Sdbana Grande, San Germén, Cabo Rojo, Hormigueros, and Maricao (Map 29). The area consists of rol- ling hills and mountains. The total population Table 28A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 28] Number | Number Rate Average Average Stratum School code os per | antigen | control tested | positive 100 area area Urban: 1 AABYI0Y inci vmsrasvmsam on ouss ods 23602 ms nw ey ass aes 22 12 54.6 1.2 0.4 1 BABUROB i oo. 10 ch: wie 0 4 sr hom brat oo ps ele st eid 4 oh 3 BL ld 41 0 0.0 0.6 0.4 1 1481105 oo 28 13 46.4 1.1 0.4 1 YABINOT iivivnmus do mms hmv a Wisse mes ms § 5 45 4m S00 008 bw 25 3 12.0 0.7 0.4 1 DEBTRRG rs ov be vii nie be Bon Bis we at ot cy tn ll oe io 3 2 44 6 13.6 0.7 0.4 1 YABYV1AD ivuviv si wos some ss Gus osu ma Sumas wes Biel d Mes 3H 083 32 2 6.2 0.6 0.5 i BABIN AD i oi di Shove oon ww boris 8 Brenna ar on ore cmc: Hil cd eid 37 7 18.9 0.8 0.4 Total oo vvnvom eros ems ens sews masses ow bs ss sess ons: oe 229 43 % 0.8 0.4 Rural: 1 Y4B2A34 oi ini imine it BORE INO IR SC CE NERC EE EEE PRO EEN§ 19 0 0.0 0.6 0.4 1 NABBLE crc ions ts vesivd vn 7 estes es ens nh ss evs on orn ol ves ve oma 14 2 14.3 0.6 0.3 1 YAB2BO0D-D. 5 oso vm ve wins 50 5595 50 6 ais BS 59 WHE HEE IES 19 1 5.3 0.5 0.4 OER ITE coe pierniint we 8 ovis oma on snore so ne nn oc os ties fies 52 3 * 0.6 0.4 GEARAUBERL . . . o « vilieed sucess ss 8 isi ns srw eTocs i # 281 46 * 0.8 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 73 Table 28B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 28] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 | tested positive Stratum 1: Urban cosasissianenn 229 43 18.8 121 33 27.3 106 10 9.4 2 0 Rural .............. 52 3 5.8 29 1 3.4 23 2 8.7 0 0 Total sow rsminnien 281 46 * 150 34 * 129 12 * 2 0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 28C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 28] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ........................... 3 0 * 3 0 * 0 0 * YO VeRrS ....:vovuivenn vn wus mows wons 5 udu sss O08 76 9 11.8 69 8 11.6 7 1 * DL WOOTE 0000 50 1 50h £5 sesh rd doin se sc wi 95 13 13.7 83 13 15.7 12 0 0.0 12years .......... cc iii 56 12 214 38 10 26.3 18 2 11.1 13 years and OVEr «qo iusi mms bss ons bom sme 50 12 24.0 35 12 34.3 15 0 0.0 Age unknown .............. Ll 1 0 * 1 0 0 0 E Total os:nvsunrssmosmssnssnmsnmssmes og 281 46 * 229 43 %* 52 3 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 28D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 28] Length of Total Total Rate Number Number Rate Number Number Rate id Percent Percent Percent residence number number per osiil urban urban per ot rural rural per it (years) tested positive 100 P°°'"'V¢ | tested positive 100 positive | ested positive 100 positive Less than1l ..... 32 T 219 152 28 7 25.0 16.3 4 0 * 0.0 1-4 ............. 73 12 16.4 26.1 64 12 18.8 27.9 9 0 ¥ 0.0 BD viiniimaninne 58 9 15.5 19.6 53 8 15.1 18.6 5 1 * 33.3 10-14... 115 18 15.7 39.1 84 16 19.0 37.2 31 2 6.5 66.7 Unknown ........ 3 0 * * 0 0 ¥ * 3 0 * % Total. ......... 281 46 ¥ 100.0 229 43 * 100.0 52 3 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 74 MAP 29, AREA NO. 29 000 — School Number * — Type of School 00 — % Infection fr go 'T HORMISUEROS /* © Urban * Rural ® Not sampled is approximately 78,000 people. There were 55 fifth grade classrooms in this area from which 15 (6 urban and 9 rural) were selected and 387 students were skin tested. Urban school prevalence rates varied from 4 percent to 17 percent, with an average rate of 10 percent, In rural schools rates from 0 percent to 11 percent were observed with an average of 8 percent (Table 29A). Combined prevalence for both urban and rural was 9 percent. In stratum 1 both urban and rural school students showed similar prevalence rates with female students more skin reactive than males; in strata 2 and 3 urban school students were more reactive than rural ones (Table 29B). In the 10-12 year age groups, prevalence rates were lower than in the 13 year age group (Table 29C), In urban schools 31 percent of the reactors have resided for ten or more years in the vicinity and in rural schools 86 percent have done the same. (Table 29D). Schistosomiasis is lightly endemic in this study area Weller and Dammin (1945) reported prevalence rates of 0 percent in Sdbana Grande, 3 percent in San Germdn, 5 percent in Cabo Rojo, 14 percent in Hormigueros, and 3 percent in Maricao. Their average preva- lence rate for these areas was 4 percent, White, Pimentel, and Garcia (1957) reported 1 percent in San Germéin. Our prevalence rate in Hormigueros was 10 percent, in Cabo Rojo- Table 29A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 29] Number | Nomber Rate Average Avetage Stratum School code vested | postive per | antigen | contro 100 area area Urban: 1 YOUTYON ,ioiosrvs mes wins om soma, ws i 6 wom wie 5.0 5 570 F 3009 % ws 27 1 3.7 0.8 0.6 1 1631102 oe 29 5 17.2 0.7 0.4 1 TGBIY0B covisomismesviussme pws bay smes sREpv Ean ss BRI IHESH 39 3 T.7 0.6 0.3 2 WEDNUON |, ci be ls mil ef ens: sshd es 0 lit 0 tb rs 4 Bl ei FL 24 3 12.5 0.7 0.5 3 1331100 Lo ee 28 3 10.7 0.7 0.5 3 JABLI0NL . .vvvcrrmr rime smns amis md sn BERR MEI FAI FEED 31 3 9.7 0.9 0.7 Total 178 18 % 0.7 0.5 Rural: 1 1632124 ..ccvnvisminmismesnaioimssonaons fms swme nesses sen 18 2 1.3 0.5 0.3 1 NBIOBOD. ctrl crs iin eh ise ecole Rl ha ice 3 0 5: in) of lr 23 2 8.7 0.5 0.4 2 1632116 «oo 25 2 8.0 0.7 0.4 2 NGBDBOL. . car v5 mm 5 ren i oes 5 5 rds # ch & Soke cs ws 0 ie oS B63 H0 9 18 2 11.1 0.8 0.5 2 NBRI0BL., iv civ © vm + wives serena § wars © 190 50 9006 © tine svn as» © lie 3 2 1 3.7 0.5 0.4 2 NOBDB0DD. vs ms swims 50504 000 Iw 53 0% 3 06 RES BW BEE BS RRS 24 2 8.3 0.6 0.4 3 1122105 oii eee 15 0 0.0 0.5 0.3 3 TAB21BD viv vos mms vm vs mas mos poss dig sams sues ames swse 27 3 11.1 0.6 0.4 3 BABDUBT ich 1 Sor ce, eds hele of a bd 0 I did em EA Es 3 32 2 6.2 0.6 0.5 Tobal i sis sme vais ai s sme » 0 2 ois & 08 00% 00 2008 4 600 8 49 209 16 ¥ 0.6 0.4 Grand total .................. iii 387 34 * 0.6 0.4 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 75 Table 29B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 29] Total Total Rate | Number Number Rate | Number Number Rate | Number Number Type school number number per male male per | female female per | unknown unknown tested positive 100 | tested positive 100 | tested positive 100 tested positive Stratum 1: Urban «co comin mg snins 95 9 9.5 48 6.2 47 6 12.8 —- - Baral :5nsiiosine snes 41 4 9.8 Nn 1 4.8 20 3 15.0 - —- Stratum 2: Urban sonsvvssnas ons 24 3 12.3 9 1 *® 15 13.3 — - Bat@ll . .oiunmvioinions 94 7 7.4 47 6 12.8 47 1 2.1 - —- Stratum 3: Uban .:..vsismasans 59 6 10.2 24 3 12.5 35 3 8.6 - - Baral co cums vues sis 74 5 6.8 45 3 6.7 29 2 6.9 - — Total zooms raise mins 387 34 % 194 17 ¥ 193 17 ¥ — - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 29C.—Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 29] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years ............covvvvininnnnn. 7 0 * 5 0 * 2 0 % years ovuevwssnesnmsnnssnss mame ames 91 8 8.8 52 5 9.6 39 3 7.7 TL YORIS ..iviv rnin mn omnis ins now an yams 129 12 9.3 59 7 1.9 70 5 7.1 12 YE vintners mes mins wmes vr u@anmany 86 5 5.8 33 2 6.1 53 3 5.7 13.YEAIS AAA. OVOF 1. ouiins 2 nitive a viol nas wind 3 73 9 123 28 4 143 45 5 11.1 Age ONRDOWR. Pros iuisvs insane sness veh 1 0 * 1 0 * 0 0 * Bota thd i nis vot elo ie A will iM 387 34 # 178 18 * 209 16 i *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 29D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 29] Length of Total Total Rate Number Number Rate Number Number Rate . Percent Percent Percent residence number number per ti urban urban per ti rural ~~ rural per sitive (years) tested positive 100 P°5'"'V® | tested positive 100 P%'''VC | tested positive 100 P Less thanl ..... 29 1 3.4 3.1 20 1 5.0 6.2 9 0 * 0.0 bed vo inn snr anus 75 8 10.7 25.0 55 6 10.9 37.5 20 2 10.0 12.5 59... 76 9 11.8 28.1 24 4 16.7 25.0 52 5 9.6 3.2 10-14 co oni inns 182 14 7:7 43.8 68 5 7.4 31.2 114 9 79 56.2 Unknown ........ 25 2 % * 11 2 * * 14 0 * * Total: seesves 387 34 * 100.0 178 18 * 100.0 209 16 % 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 76 7 percent, in Sdbana Grande 1 percent, and in San Germén - 9 percent. eo Area 30 comprises one watershed with a 26,000~-acre irrigation project and the Laguna Cartagena, There are afew small streams with intermittent flow plus the towns of Guénica, Ensenada, and Lajas (Map 30). The total MAP 30, AREA NO. 30 000 — School Number * — Type of School 00 — % Infection GuANICA 106 u ”" ENSENADA © Urban * Rural @® Not sampled population of this area is approximately 40,000 people. There were 31 fifth grade classrooms in this area from which 11 (5urbanand 6 rural) were selected and 297 students were skin tested. Prevalence rates in urban schools ranged from 3 percent to 14 percent with an average of 8 percent. Rural school prevalence rates ranged from 0 percent to 15 percent with an average of 5 percent (Table 30A). Combined prevalence for both urban and rural schools was 6 percent. Urban school male students were the most reactive group (Table 30B), and prevalence rates did not varygreatly between age groups (Table 30C). In urban schools 33 percent and in rural schools 71 percent of the reactors have resided for ten or more years in the vicinity (Table 30D). There has been little evidence of active transmission of schis- tosomiasis in this dry valley during the past decade. Weller and Dammin (1945) reported a prevalence rate of 3 percent in Guénica and 7 percent in Lajas. Our overall prevalence rate may be due mainly to the influx of infected school children from other parts of the island. eo Area 31 is comprised of one-third of the island of Vieques and the town of Isabel Segunda (Map 31). The island has mostly rolling hills and coastal alluvium plain, There are 36 small streams which flow intermittently. The total population of this area is approximately 7,200 people. There were 4 fifth grade class- rooms in this area from which all 4 (1 urban and 3 rural) were selected and 98 students were skin tested. Prevalence rates varied from 3 percent to 25 percent for both rural and urban schools Table 30A.=Distribution of positive skin reactors by individual sample classrooms [Watershed area 30] Number | Number Rate Average Average Stratum School code i per | antigen | control tested | positive 100 area area Urban: 1 TATTU02=L ones ms mmm vim vx mw ws v0 cow x om ww mw #20 ww a 22 3 13.6 0.9 0.6 1 I270002-2 .sncnnasomes Hes amts miami nm isms armas assnn 33 4 12.1 0.8 0.5 1 BOTA 1 vm ses aout min ime oho wis hn. ie Sb 3 i 36 2 5.6 0.7 0.5 1 12700082 i uvinmsoniooianm ames @eisassols vs smes ssp 29 1 3.4 0.7 0.5 1 1391101 oo 32 2 6.2 0.6 0.4 "TOUAY soon cin mm diss HOE 2 8 HF 30 Wl 0 BKK WIE BIR EF WE E50 152 12 k 0.7 0.5 Rural: 1 YYCVND ini gin wai hi 3 48 53 R05 0.5 8 i £3 Bi 0 0 10 1 10.0 0.6 0.4 1 ZZN06 sts. 100+ cis isn 0 is wd od eb id so. dc es edo he 13 2 15.4 11 0.6 1 1302017 oom ran nr HAE ME EF BEEBE SERRE EE FEEL EE YO 24 2 8.3 0.6 0.5 1 1392122 Lo eas 31 1 3.2 0.6 0.4 1 130280) .uvrvvsvmisnrnmerrmrrnremasaminmernrs ass matas 31 1 3.2 0.6 0.4 1 BEIDTOL or 200s 00 iim 0m iis © 0 B84 8 i 3 Fa 40 i 8 ot RS 36 0 0.0 0.4 0.4 TOTAL (pos insampswnsrnsarusrasemn sin seen onal Bisse 145 7 * 0.7 0.5 Brand RORY, ov soos wom 2 win pi nog 2 BE PRP PEE EEE 5 Eu 297 19 *% 0.7 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 77 Table 30B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 30] Total Total Type school number number Rate per tested positive 100 Number Number Rate male per tested positive 100 male Number Number Rate female female per tested positive 100 Number Number unknown unknown tested positive Stratum 1: Urban ..oisnvisnssns 152 12 7.9 74 8 10.8 76 4 53 2 0 Rural .............. 145 7 4.8 68 5 7.4 7 2 2.6 - - Total cusavssnssns 297 19 * 142 13 % 153 6 ¥ 2 0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 30C.—Distribution of positive skin reactors by watershed area, age, and type school [Watershed area 30] Total Total Rate | Number Number Rate | Number Number Rate Age number number per | urban urban per | rural rural per tested positive 100 | tested positive 100 | tested positive 100 Under 10 years. ; comms emsnmesmns miss wes so 6 1 % 5 1 1 0 oh VOSTERTE: wi vie ceva soos nibh of» chi Wt of set iso wine 55 5 9.1 32 3 9.4 23 2 8.7 1) YORE: wnsumsiim some emus mis Pars me mms sms 113 6 5.2 46 4 8.7 69 2 2.9 12 years .......... iii 69 5 7.2 36 3 8.3 33 2 6.1 13 years and Over ...oiucsmrimmssnerses ens 50 2 4.0 31 1 3.2 19 1 5.3 Age WIRDOWI 25 oon evisniosmnss meses wisn 2 0 ® 2 0 ¥ 0 0 * Total .ovirnsismrimnrmnymmemmes mens 297 19 * 152 12 * 145 7 * *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 30D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 30] Length of Total Total Rate Number Number Rate Number Number Rate . Percent Percent Percent residence number number per ti urban urban per ti rural rural per it (years) tested positive 100 PO%'"'V¢ | tested positive 100 PP" | tested positive 100 POSU'VC Less than1l ..... 28 2 7A 10.5 26 2 7.7 16.7 2 0 % 0.0 1-4............. 64 4 6.2 21.1 36 3 8.3 25.0 28 1 3.6 14.3 BD anvswsrmens 43 4 9.3 21.1 21 3 14.3 25.0 22 1 4.5 14.3 10-14 ........... 132 9 6.8 47.4 45 4 8.9 33.3 87 5 5.7 71.4 Unknown ........ 30 0 % * 24 0 x : 6 0 * ¥ Tol... ....o0.. 297 19 * 100.0 152 12 * 100.0 145 7 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 78 MAP 31, AREA NO. 31 000 — School Number * — Type of School 00 — % Infection 002 isasEL SG 'secunoa Vieques Island © Urban * Rural ® Not sampled (Table 31A). Combined prevalence for both urban and rural schools was 11 percent, Rural school children were the most skin reactive grqup with rural males being higher than rural females (Table 31B). Skin reactivity varied considerably between 10- and 12-year-old stu- dents (Table 31C). In urban schools the single reactor resided in the area 10 or more years, and in rural schools 80 percent resided in the area 10 or more years (Table 31D). Weller and Dammin (1945) reported a prevalence rate of 21 percent in Vieques. The absence of skin reactors in the 5 to 9 year residency group indicated that there may be no transmission in this area at the present time and this may be due to the control project started in 1954, Table 31A.—Distribution of positive skin reactors by individual sample classrooms [Watershed area 31] A s School cod Number | Number | a1 | Toereft | FHorhes gratam choot code tested | positive 100 area aTes Urban: 1 YZATV0D von mmanvs owes Sanam as maa eww wins am ssw smn sy 29 1 3.4 0.7 0.5 Total 29 1 * 0.7 0.5 Rural: 1 V742004 ...cinviinivmissirs Rasnsismis Nemes oni smes wey 24 6 25.0 1.1 0.5 x WZBIUOT. wee cv 5 3 evr is howe eo) coms he 3 snd on bo, vd of oss svi o ic on Sos 28 2 7.2 0.7 0.4 1 YTATNOG wo socovv wim o vio swim b 5 900 8 B15 55505 8 RIE #5 608 0» ¥ 1950s ¥ 40904 % 000 8 17 2 11.8 0.8 0.6 TRBEEH cs ves agann ie soc bom os 0 inn es miso mth 10 dd se he 69 10 ¥ 0.9 0.5 CTBT LOVE... nite st aso sh se sone tl he eh he i i 0 AG 98 11 * 0.8 0.5 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 31B.—Distribution of positive skin reactors by watershed area, stratum, sex and type school [Watershed area 31] Type school Total Total Rate number number per tested positive 100 Number Number Rate male per tested positive 100 male Number Number Rate female female per tested positive 100 Number Number unknown unknown tested positive Stratum 1: Urban .............. 29 1 3.4 19 1 5.3 0 0.0 - - Rural .............. 69 10 14.5 39 7 17.9 3 10.0 - - Total ............ 98 11 % 58 8 % 3 * - - *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. 79 Table 31C.-Distribution of positive skin reactors by watershed area, age, and type school (Watershed area 31] Total Total Rate number number per tested positive 100 Number Number Rate urban urban per tested positive 100 Number Number Rate rural rural per tested positive 100 Under 10 years... uassais nis visnniomssns 1 0 oi 0 0 i 1 0 : 10 VRAIS: cr ven ny 40 lr lw 0s 0 wed wt 14 2 143 4 0 % 10 2 20.0 ll years su ionsussnuirmvanas sts m@man Honus 42 1 2.4 15 0 0.0 27 1 3.7 VD YBAEBI th riers in lenis cette fe a? Bp Wns i 19 4 21.1 4 0 * 15 4 26.7 13 years and over ....issismerarss vruusams 22 4 18.2 6 1 g 16 3 18.8 DBE. cities a: Midst itt inst Bt midi a feds 98 11 % 29 1 » 69 10 ¥ | *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios or for unknowns. Table 31D.—Skin reactor rates and percentage distribution of positives by length of residence, type school and watershed area [Watershed area 31] Length of Total Total Rate Number Number Rate Number Number Rate : Percent Percent Percent residence number number per ti urban urban per 4 rural rural per tiv (years) tested positive 100 POSILIVE | tested positive 100 POSILIVE | tested positive 100 Posiuve Less than 1 ..... 1 0 * 0.0 1 0 ® 0.0 0 0 0.0 4. iainss menses 3 2 154 18.2 5 0 % 0.0 8 2 » 20.0 BID oii inn es went 6 0 ® 0.0 1 0 ® 0.0 3 0 % 0.0 10-04 cai 5 00 050s if] 9 11.7 818 22 i 4.5 100.0 55 8 14.5 80.0 Unknown ........ 1 0 * * 0 0 * % 1 0 % 5 Total: ::n::n.: 98 11 * 100.0 29 1 * 100.0 69 10 * 100.0 *Rates not calculated where number tested was less than 10 or for totals based on unequal sampling ratios. Unknowns excluded from totals in calculating percentage distributions. 80 BIBLIOGRAPHY Barbosa, F.S., Coelho, M.,V. and Continbo- Abath E. 1958. Infestacao natural e ex- perimental de alguns mamiferos de Per- nambuco por Schistosoma mansoni. Rev. Brasil de Mal, Trop. 10:137-144, Bogart, D. B., Arnow, T., and Crooks, J. W, 1964. Water resources of Puerto Rico— A progress report. Puerto Rico Water Resources. Bull. No. 4 (unpublished). San Juan, 16 pp. Burke, A. M. 1929. Report of the Pathology Department oI the School of Tropical Medicine for the first three years ending April 15, 1929. P. R. J. Pub. Hlth, and Trop. Med. 5:48. Casas de Ldpez, L. 1963. Bilharzia (schis- tosomiasis mansoni) in Puerto Rico—A bibliography, 1904-1962. Processed re- port, University of Puerto Rico, School of Medicine, Library—San Juan, 18 pp. Cochran, W, G. 1963. Sampling techniques. John Wiley & Sons, Inc., New York (2nd edition). Faust, E. C, 1933. Studies on Schistosomiasis mansoni in Puerto Rico. 1. The history of schistosomiasis in Puerto Rico. P. R. J. Pub. Hlth. and Trop. Med. 9:154-161. Faust, E. C., Hoffman, W, A,, Jones, C. A, and Janer, J, L., 1934. Studies on Schis- tosomiasis mansoni in Puerto Rico. 1. The epidemiology and geographic dis- tribution of schistosomiasis area in Puerto Rico. P. R. J, Pub. Hlth. and Trop. Med. 9:447-491, Febles, F. and Brooke, M. 1961. Personal communication. Ferguson, F. F. 1955. Chronologic summary of fecal surveys for bilharziasis in the Antilles with special reference to Puerto Rico. USDHEW, Public Health Service, CDC - Atlanta, Processed report, 5 pp. Unpublished. Ferguson, F. F, 1965. Occurrence of schisto- somiasis mansoni in Puerto Ricans. Public Health Reports 80:339-345. Ferguson, F, F., Rowan, W, B, and Palmer, J. R. 1958. Bibliografia Seleccionada sobre 81 bilharzia antillano o esquistosomiasis mansoni Dept. Publ. Instr., San Juan, pp 66. Friedman, E. A. and Shookhoff, H, B, 1957. Schistosoma mansoni infections in hos- pitalized Puerto Rican patients. N, Y. State J. Med. 57:3994-3996. Gonzalez-Martinez, I, 1904. La bilharziosisen Puerto Rico. Tip. Bol. Merc. San Juan, P. R. p. 32. Gouveia, O, F. and Beamer, W, D, 1955, The importance of microscopic granulomas (Pseudotubercles) in the diagnosis of Manson’s schistosomiasis. Gastroenter- ology 28:634-641. Harry, H., W, and Cumbie, B. G., 1956a. The relation of physiography to the types of freshwater environments and the presence of Australorbis glabratus in Puerto Rico. Am. J. Trop. Med. Hyg. 5:742-755, Harry. H, W, and Cumbie, B. G. 1956b. Stream gradient as a criterion of lotic habitats suitable for _Australorbis glabratus in Puerto Rico. Am. J. Trop. Med. Hyg. 5: 921-928. Horstman, H. A., Jr., Chaffee, E. F. and Bauman, P, M. 1954. Schistosomiasis mansoni in Puerto Rican soldiers. Am. J. Trop. Med. Hyg. 3:914-917. Kagan, I. G., 1958. Contributions to the im- munology and serology of schistosomia- sis. Rice Institute Pamphlet 45:151-183. Kagan, I, G. 1959-1961. Unpublished. Kagan, I. G. and Pellegrino, J. 1961. A critical review of immunologic methods for the diagnosis of bilharziasis. Bull. WHO 25: 611-674. Kagan, I, G., Pellegrino, J. and Memoria, J. M.P., 1961. Studies on the standardization of the intradermal test for the diagnosis of bilharziasis. Amer. J. Trop. Med. Hyg. 10:200-207. Kagan, I. G., Rairigh, D. W, and Kaiser, R. L. 1962. A clinical parasitologic and im- munologic study of schistosomiasis in 103 Puerto Rican males residing in the United States. Ann. Int. Med. 56:467-480. Koppisch, E. 1931. Report of the Pathology De- partment of the School of Tropical Medi- cine, April 1929 — June 1930. P.R.J. Pub. Hlth, and Trop. Med. 6:334. Koppisch, E. 1941. Studies on Schistosomiasis mansoni in Puerto Rico. VI, Morbid anatomy of the disease as found among Puerto Ricans. P.R.J. Pub, Hlth, and Trop. Med. 16:395-455. Lambert, R. A, 1927, Studies on Schistoso- miasis mansoni in Puerto Rico. II, Pre- liminary report on findings in 100 routine autopsies. P. R. Rev. Pub. Hlth, and Trop. Med. 3:231-234. Lambert, R. A, 1928. Some observations on the pathology of schistosomiasis (S. mansoni) in man and experimental animals. Bol de la Assoc. Med. de Puerto Rico 21:15-20. Lambert, R. A. and Burke, A, M. 1928, Studies on schistosomiasis (S. mansoni) in Puerto Rico. IV. Correlations of clinical and autopsy findings with case reports. P.R. Rev. Pub. Hlth, and Trop. Med. 3: 403-415, Latty, S. G., Hunter, G. W., Moon, A. P., Sullivan, B, H., Burke, J. C., and Sproat, H. G. 1954. Studies on schistosomiasis. X. Comparison of stool examination, skin test, rectal biopsy and liver biopsy for the detection of Schistosoma mansoni. Gas- troenterology 27:324-333. Lyons, R. T. and Benson, J. 1954, Schistosoma mansoni. A study of 26 Puerto Ricans ina non-endemic area. Ann, Intern. Med. 40: 1194-1206. Maldonado, J, F, and Oliver-Gonzalez, J. 1958. The prevalence of Schistosoma mansoni in certain localities of Puerto Rico—a three-year study. Am. J. Trop. Med. and Hyg. 7:386-391. Maldonado, J. F. and Oliver-Gonzalez, J. 1962, The prevalence of intestinal parasitism in six selected areas of Puerto Rico—5 years afterwards. Bol de la Asoc. Med. de Puerto Rico 54: 133-148. Martinez-Rivera, E, and Koppisch, E. 1956. Las manifestaciones pulmonares de la esquistosomiasis de Manson en Puerto Rico. Bol de la Asoc. Med. de Puerto Rico 48:402-422, Pellegrino, J. and Macedo, D. G. 1956. Novo criterio de leitura da reacao intradermico na esquistossomose. Rev. Bras. Malar. 8: 499-509, Pellegrino, J. and Rezende, C. L., Memoria, J.M.P,, Mourdo de Gord, Brener, Z. 1959. Diagnostico de laboratorio de es- 82 quistossomose mansoni na criznca J. Pediat. (Rio de Janerio) 24:211-230. Pico, P. 1950, The geographic regions of Puerto Rico. Univ. Puerto Rico Press Rio Piedras, P. R. — pp. monograph, Pimentel, D. and White, P. C., Jr. 1957. Geographic distribution of Australorbis glabratus, the snail intermediate host of Schistosoma mansoni in Puerto Rico. Am. J. Trop. Med. and Hyg. 6:1087-1096. Pimentel, D. and White, P, C., Jr. 1959a. Biological environmental and habits of Australorbis glabratus. Ecology 40: 541- 550. Pimentel, D. and White, P. C., Jr. 1959h. Physiochemical environment of Aus- tralorbis glabratus, the snail intermediate host of Schistosoma mansoni in Puerto Rico. Ecology 40(4):533-541. Pons, C. A, and Reyes, F. M, 1950. Manson’s schistosomiasis in Puerto Rican soldiers. P.R.J. Pub, Hlth, and Trop. Med. 25: 319-323. Ritchie, L. S., Jachowski, L, A, and Ferguson, F. F. 1960. ‘‘Bilharzia’’—a military prob- lem in Puerto Rico. Mil. Med. 125:253- 257, Ritchie, L. S., Radke, M. G. and Ferguson, F. F, 1962, The population dynamics of Australorbis glabratus in Puerto Rico. Bull, WHO 27:171-181. Springharn, C. L., Edelman, M, H., Gold, T., Yarms, H. and Twiell, R. 1957. Value of rectal biopsies in the diagnosis and treat- ment of Schistosoma mansoni infections. N. Eng. J. Med. 256:290-294. Statistical Abstracts of the United States. 1963 U. S. Dept. Commerce. Trubowitz, S. and Redish, M. H., 1950. The rectal mucosal punch biopsy in the diag- nosis of Schistosomiasis mansoni. Gas- troenterology 14:391-394. United States Census of Population, 1960. Puerto Rico. U., S, Dept. Commerce. Weller, T. H, and Dammin, G. J. 1945. The incidence and distribution of Schistosoma mansoni and other helminths in Puerto Rico. P.R.J. Pub. Hlth. and Trop. Med. 21:125-141. White, P, C., Pimentel, D. and Garcia, F. C. 1957. Distribution and prevalence of hu- man schistosomiasis in Puerto Rico in 1953. Am. J. Trop. Med. and Hyg. 6: 715-726. APPENDIX 1 PRFS Form 9 NAME OF SCHOOL 12/62 WATERSHED AREA WATERSHED SUBAREA CODE # SKIN & FECAL TEST DATA SHEET Surname (Paternal & Maternal) First Name MN, Identicication # Age Sex Address Father’s Name Mother’s Name Previous history of schistosomiasis infection: Yes () No ( ) Unknown ( ) How long have you lived in this area? Months Years Previous area of residence Date of testing Tester Reader Time of Injection Tracing of Reaction + 15 min, Time of Reading Antigen Area Control Area Fecal Sample: Yes ( ) No ( ) Date Collected Results 83 APPENDIX 2 Item No. CARD CODE Puerto Rico Schistosomiasis Skin Test Survey Item Study Identification Form Number Watershed Area Watershed Subarea School Code Number PR63 1962-1963 Code Record as Stamped As Recorded As Recorded As Recorded Type of School Public Academic Private Accredited Private Not-Accredited Public Vocational Private Vocational Public (Music) Public (Exceptional Students) Private (Exceptional Students) Administered by Other Governmental Agencies Elementary Elementary and Intermediate Elementary and Intermediate (complete) Elementary and Secondary 84 Columns 1-4 5-9 10-11 12 13-20 CTI. Col. 13 wi wren 8 Cols. 14-15 iW Col. 16 see Col. 17 Grades 0-6 0-8 0-9 0-12 Item No. Item Code Columns SOLIBE v . vv vivir sine vied daw ud Cols. 18-19 Numbers are progressive in series depending on Column 17, For example: Elementary Schools — the first one listed gets 01, the second one 02, and so on within each municipality. Class Number , + . « vs vv vv vv vw vis Col. 20 As Coded If blank, leave blank 6 Total Children As Coded in Red (circled number below 21-22 in Classroom school code number) Note: 8=08 25 = 25, etc. 7 Student Identification As Recorded 23-24 Number 8 Students Age in Years As Recorded 25-26 If Blank or Unknown, Punch 99 9 Students Sex As Recorded 2 Male (M) -1 Female (F) -2 Unknown or Blank - 9 10 Previous History of As Coded 28 Schistosomiasis Infection Yes -1 No - 2 Unknown or Blank -9 11 How Long Lived As Recorded 29-32 in Area MONNE uv ine wore wiles ie wie Cols. 29-30 As Recorded; except if in years, leave blank. If less than 1 month, code 00 YOUUS cians vs msds viams Cols. 31-32 As Recorded; except if in months, leave blank If both months and years are blank or unknown, punch 99. 85 Item No. Item 12 Date of Testing 13 Antigen Area 14 Control Area 15 Results Code As Recorded If blank, leave blank January - 01 February - 02, etc. Date of Month , , ...... 1=01 2 = 02, etc. 1962 = 62 1963 = 63 As Recorded 0.9 = 09 32=12 4,7 = 47, etc. Not listed = Other reasons Refusal If absent If blank or unknown As Recorded (Same as above) “Eww Cols. 33-34 EEE EW Cols. 35-36 CTE Cols. 37-38 96 97 98 99 As Coded in red to right of Antigen Area Positive Negative Unknown If blank, leave blank 1 2 9 Columns 33-38 39-40 41-42 43 REMAINING ITEMS (16-18) APPLY ONLY TO WATERSHED AREAS 3, 12, 13, and 14, FOR ALL OTHER AREAS, STOP HERE, EXCEPT ITEM 19. 16 Fecal Sample 17 Date Fecal Sample Collected As Checked Yes No Unknown If blank, leave blank As Recorded If blank, leave blank 86 DN = 44 45-50 Item Item Code Columns No. ne —_— == Month ............0000... Cols. 45-46 January = 01 February - 02, etc. Dateof Month ............... Cols. 47-48 1=01 2=02, etc. Years ... viet ieee Cols. 49-50 1962 = 62 1963 = 63 18 Results As Coded 51-61 If number is circled, punch 1 in appropriate column; if blank, leave blank. 0 - Negative Col. 51 1 - Ascaris (A) Col. 52 2 = Trichuris (T) Col. 53 3 - Hookworm (H) Col. 54 4 - Schistosomiasis (Schisto) Col. 55 5 - Strongyloides Col. 56 6 - E. histolytica Col. 57 7 - E. coli Col. 58 8 - G. lamblia Col. 59 9 - Others Col. 60 Not Tested Col. 61 19 Erythema Present As Recorded at bottom of form 62 If present, punch 1 If blank, leave blank 87 APPENDIX 3 Selection of Sample Points for Model Watershed Area Using watershed area 12 as a model area we will show in detail the methods used for selecting sample points and for estimating the ratio of the total number of positive skin reactors to the total number of children tested. Calculations for the estimated variance of the ratio esti- mate and for the confidence interval on the true population ratio will also be shown. The following is the list of all schools having one or more fifth grade classrooms for water- shed area 12. Each school is listed by a code number given by the Insular Department of Education in Puerto Rico, name of school, sex, total fifth graders in school, number of fifth grade classrooms, and average number of fifth graders per classroom. The schools are grouped by the municipality in which the school is located. Listing 1.—Fifth grade school population [Watershed area 12] School Name Type Male) Female! Total Number Average / code school classrooms | classroom Aibonito: 1051101 Federico Degetau........................... Urban 58 59 117 3 39.0 10321041 Caonilla® wouiivseisivcsinmomannsass iis rhrs Rural 8 6 14 1 14.0 1052107 | Llanos Adentro........................o.... Rural 14 11 25 1 25.0 1052108 | Llanos Carretera ........................... Rural 9 13 22 1 22.0 1052109 Rabanal conouss oss 5 vummmmaoam ess s 39% 3 5253 Rural 23 11 34 1 34.0 1052112; Suen. Torres ....... om vummmsmrrccsnsrvnenns Rural 36 23 59 2 29.5 1052301 SU. ABOMANLE +. . i vou smpmmanine ss sagas densa Rural 32 30 62 2 31.0 1052302 S.U.LaPlata. .................ccovvvvunn.. Rural 29 35 64 2 32.0 10523037 Battle Paso: . « ou vuivs wsimstisimmisnink's 5% £9» 40s 0.4 Rural 35 3 66 2 33.0 Barranquitas: 1101101 | Elemental Urbana Quedlo Urban .............. Urban 63 49 112 3 37.3 T0105] La'Vega o.. ::vommvmmmnns munsons soy isatens Urban 24 21 45 1 45.0 1102112 Quebradillas #1 ........................... Rural 13 9 22 1 22.0 1102301 | S.U. La Loma ...covevnnrnrvrnenssnnsomomns Rural 28 42 70 2 35.0 1102302 8.1. Helechal, . ; i ov svwwmmumns v3 593 3 4 43 2 4553 Rural 30 30 60 2 30.0 Cayay: 1171100 | LvizM. Rivera... ..coonivivmnessrvcnsrmmnne Urban 72 65 137 4 34.3 AY70002) Benigno Carrion, .ovouwin owas x83 3 v3 5 8 winone Urban 79 96 175 4 43.8 1171103 NUR oes ok 00 masibosimeniiie ol 48 4 « ol dined Urban 116 96 212 5 42.4 1172108.) Buena Vista. ,.ocemvimewens ass ss iesss ss uoemes Rural 24 37 61 2 30.5 1172106 Maton Abajo ............................... Rural 14 13 27 1 27.0 TV72102 VeRAS ...uvivssissmonumunens ss isss iss vivis Rural 21 24 45 1 45.0 1172106) Farallon .. cvs sosmmmmin s5us sv own vos ow nae Rural 6 8 14 1 14.0 1172301 SU. Montellano . ....onovnnennsrennses mnnmns Rural 43 43 86 2 43.0 1172302 | S.U. Tota ..... cvvvnwmvms owns ss sess es sms Rural 36 22 58 2 29.0 1172303 | S.U. Rexford G. Tugwell .................... Rural 41 33 74 2 37.0 1172304 | Guabate Gerardo Selles Sola ................ Rural 23 23 46 1 46.0 1172109 | Rinson Marina. ............................. Rural 17 8 25 1 25.0 M7210] St. THOMAS . ov ivnnmmmsmmn sos vs sss vss bemme Rural 13 18 31 1 31.0 Cidra: 1201105 L.M. Rivera ....................ciuuinn.. Urban 144 118 262 % 37.4 1202106 Barrio Batriz . ;ooeumnacnssisussossenenemmns Rural 24 Nn 51 2 25.5 1202108 Bo. Rabinal................................ Rural 19 22 41 1 41.0 1202109 Bo. Rio Abajo. ............................. Rural 15 13 28 1 28.0 1202302 SU. BINCOn unpre ss sess sss is « sommnivien ems Rural 34 32 66 2 33.0 Coamo: 1212115] Palguillas A. ..couvinsiiniiins er inmmmmmmmen Rural 6 10 16 1 16.0 1212116 Pulguillas B............................... Rural 11 7 18 1 18.0 Comerio: 122125 Cuba Libre ................................ Urban 95 93 188 5 37.6 1222109 Sabana........oviviiiiiiiiiiiii in Rural 24 18 42 1 42.0 1222116 | Pinas Arfiba ; vonvonms vss ss 5450 2 posmmmaei Rural 11 8 19 1 19.0 1222302| S.U.RioHondo ............................ Rural 20 17 37 1 37.0 1222123 Cas #2 oo. omnis ds 585 8.55 45% tow asim issnses Rural 3 ? 10 1 10.0 Guyama: 1282100 C.Cambrene....oovrvvesrersnrenrmnmmnsnens Rural 7 13 20 ¥ 20.0 In order to arrive at separate estimates for the urban and rural schools, separate samples were taken for each of the two classifications. Since we were interested not only in separate estimates of the prevalence rates for urban and rural schools but also in any indications of small endemic pockets where schistosomiasis is a problem, the major watershed areas were sub-divided into minor watersheds. These subareas were considered as strata in this par- ticular survey design. The following is the listing of all rural schools having a fifth grade in watershed area 12. The listing is shown by sub-watersheds (strata) and gives the respective school code number and number of classrooms in the school. Listing 2.—Rural schools by sub-watershed areas Stratum 1 Number Stratum 2 Nuwher Stratum 3 Number Stratum 4 Number classrooms classrooms classrooms classrooms 1282109. ..... 1 1172106. ..... 1 1052303. ..... 2 1102112... . «i: 1 1172308...... Db mira sm enw] nmr mone 1052301... .... 2 1222302...... 1 1172116... ov» 3 1172302, ..... 2 1052109... Lb | wosmensmunmads J sninnesemns AMN72108,.. 54+ 2 1052302. ....... 2 1052113... ..0 2 1 ff Ta mn i ne Vea ede emote 1172301...... 3 1202108. ..... 1 1212115. ..... A oma 55 5s sae si wn 2172312. 0 50 5 1 12021009...... 1 1052108. ; 50 + 1 essemsimesnns | swevmnsnas 172304... « 1 1222116...... 1 1052104... ..... Limi en eee} ems retin 1202302. ..... 2 1222123. 0x vue 1 1052107...... Y ob wes se remmemele |e oes mes mes 1202106. : : «- - 2 1222109...... 1 1212116. ..... 1 all re hi et iene Gt mie ntte 11721114... LX raion raul wre ped ee 1102302...... 2 ru re ere ee re ma x fe 1172109... 0» A | sissenmsimenn] awareness 1102301... on DY - ll fs Sine dacs Sar Ls ease lies Total .. .. 1 | wesuruarimeey 10 {| wrsmecumenmes 16 | wos mm we 3 els 2 Sample classrooms were allocated to sub-watershed areas in such a manner that each stratum has a number of sample classrooms in proportion to the number of fifth grade class- rooms it contains (proportional allocation of sample points). As can be seen from Listing 2 above, there were 44 rural classrooms in area 12. Ten classrooms were included in the sample, thus making a classroom sampling ratio of 10/44 = 1/4.4, A random number between 0 and 4.4 was then selected from a table of random numbers. In this case the number was 3.1. The sample classrooms were allocated to the sub-watershed areas by adding the sampling ratio to the random number selected in a manner as is demon- strated in the following table. Table 1.—Allocation of sample points Stratum Number classrooms | Cumulative total | Sampling ratio=1/4.4 | Classrooms in sample Bc ents ble wie Sie Ms ain 4 de 2 16 16 3.1, 7.5,11.9 3 Dsus mma mes pus EE ss was 10 26 16.3, 20.7, 25.1 3 B iiiremiimisnmsnsianrmsin 16 42 29.5, 33.9, 38.3 3 Cn eit Wee BR hein islet hr st 2 44 42.7 1 89 After allocating the sample points, the required number of classrooms for each stratum is selected at random. This is done by assigning a number to each classroom within a stratum and selecting the required number of classroom by use of random number tables. The randomly selected classrooms for the rural schools of major watershed area 12 are shown in Listing 3. Listing 3.-Selected sample classrooms for rural schools —major area 12 Code | Stratum Name Total Number Average/ classrooms | classroom 1172303 1 S.U. Rexford G. Tugwell ................................... 74 2 37.0 1172112 1 WBHHE coi rome hum se as hts nfs os 3 01 3 ee 0 id Gl 45 1 45.0 1202106 1 Barrio Batriz .............. 51 2 25.5 1052302 2 SU. Lim Platbois vcs sions 5k 5 ww © 505 45.550 5 050 5 954 4 0 4 5 G08 S000 63 9 5 aid & 64 2 32.0 1202108 2 Bo.Rabinal ................iiii i 41 1 41.0 1222109 2 Sabana: ivnmzs ome wwe smn nom eT Lp 5 08 Ve SEW E09 5 SRW HOE SHEE BE 42 1 42.0 1052109 3 Rabanal ............ 34 1 34.0 1212115 3 Pulguillas A... 16 1 16.0 1052107 3 LARNOS AQCHED 5c vm os wo som s wid 25 55 50 4.596 § #05 € » Gi 4 WHE HEE Wns 25 1 25.0 1222302 4 Rio Hondo. ......... iii 37 1 37.0 TO RN vv coi mn vnm sui £50 5% as ibis #inas 0k 6 G0 6500 #55 4 4 Win 5 Wi 5 B10 4 00% ¥ HI 08 06 5 04 0 334.5 Selection of the sample classrooms for urban schools was done in the same manner as was done for rural schools. The urban schools that were included in the sample for watershed area 12 are listed below. Listing 4.—Selected sample classrooms for urban schools — Major area 12 Code | Stratum Name Total Naber Average classrooms | classroom 1171102 1 Benigno Carrion. ..........covivvnivnmisnerninnnnrncncernes 175 4 43.8 1171103 1 Yomuri. coiomisuis ovina smi ams Bes sns Buia nmin ses BeRmas ama 0 212 5 42.4 1201105 2 LL.M Rivera... .....uiiii i eee 262 7 37.4 1051101 3 Federico. Degetan ....ou: vu sonsmrisnrsmsrmmrsmes one mmenmen 117 3 39.0 1101101 4 Elemental Urbana Quedlo. ....cv.oncincrsssinsnndss Sesmas amas 112 3 37.3 1221125 4 H.M. Towner Pedro N. Ortiz .................coovniinnunnn. 188 5 37.6 IIE irs Sines ge costed wien mc wom hiss wc ond sch hows i BW cof a9 4, hb ited 60 237.5 90 APPENDIX 4 Calculation for Estimation of Variance and Confidence Intervals The following table presents the sample data and calculations for the rural classrooms in a convenient way for estimating the ratio of positive skin reactors to the total number of children, estimating variances of the ratio estimate and the 95 percent confidence interval for the popu- lation ratio. Only the calculations for the rural sample schools will be shown in detail since the procedures are the same for the urban classrooms and for the overall sample of the combined (combining rural and urban sample) watershed area. Definitions of notation and calculating formulas are given in the ‘‘Analysis of Data’’ section of the text. Rural sample classrooms [Watershed area 12] Stratum 1 Stratum 2 Stratum 3 (3+4) Classroom Total X1i Yi; | Xo Yo; | X3; Ys; GT i i Se ent ret ss 0 EO 3 38 | 1 26 | 3 31 |...... BB et tre sls» peri I — 5 32 | 2 39 | — 16 |...... Coit en ne bree eae heh ens 4 22 | 3 36 | 10 19 |...... D ear rrre aaron = - | = -{ 8 36 |...... A 0.1304 0.0594 0.1765 0.1283 B+ 0 4H RE EWE EYEE AER aS ARE RAR Fk A is 1.0000 1.0000 17.6667 | ...... Bu svar mesa tomas wna 2 ren nn 65.3333 46.3333 91.0000 |...... SIPs tum dunia a rus Sor DHS Hal TT a FRR £0 —3.0000 5.0000 1.3333 |...... SZ ee 2.8478 0.4815 18.8261 |...... Therefore the individual stratum estimates of the proportion of positive skin reactors is 13 percent, 6 percent, and 18 percent for strata 1, 2, and 3 (3 + 4) respectively. The overall estimate of the ratio for the rural classrooms was 13 percent, Using the formula for calculating the estimated relative variance, we have My My - my) = s?=0.0512 my, 3 v2.1. = dl LETS We may get an estimate of the variance by multiplying v? by r 2 as follows: (0.0512) (0.0165) = 0.000845 = s 2 Then the 95 percent confidence interval for R, using the normal approximation would be. r+ty/s?=0.1283 + 0.0570 Applying the same methods for the urban sample, the individual stratum estimates of r were 8 percent, 17 percent and 46 percent for strata 1, 2 (2 + 3), and 4 respectively. The over- all estimate was 20 percent. The 95 percent confidence interval on R for the urban schools was 20 percent * 6 percent. Combining the urban and rural samples produced an estimate of 16.44 percent positive skin reactors for the watershed as a whole, with a 95 percent confidence interval on R of 16.44 percent + 4,21 percent. 91 * U.S. GOVERNMENT PRINTING OFFICE : 1967 0—245-388 I Maa: RR Erde ee it Rai idee Shea Toe hr Tol tat Pas mE TT eee nt eo. 50 ai Public Health Service Publication No. 1525 Nin (029420bb9 ETT ga