B-1426 January 1983 a Economic and Ep idemio l0 gical Implications of An aplasmo s i s in Texas “e ef ~18 The Texas Agricultural Experiment Station, Neville P. Clarke, Director, The Texas A&M University System, College Station, Texas In cooperation with VeterinaryServices, APHIS, U.S. Department of Agriculture. CONTENTS pd ha \O \O\O\O® CD \IUIIPI\)I\J IQ 11 11 11 11 12 12 15 15 16 INTRODUCTION The Problem Source of Data EPIDEMIOLOGICAL RESULTS Areas of Anaplasmosis Incidence by Areas Incidence by Herd Size Seasonal Occurrence Vectors PHYSICAL AND ECONOMIC LOSSES Death Loss Weight Loss Chronic Cases Abortions TREATMENT AND PREVENTIVE MEASURES AND COSTS Treatment Costs Preventive Measures and Costs Vaccination Low-Level Chlortetracycline Vector Control Oxytetracycline Injections TOTAL CLINICAL CASES, ANAPLASMOSIS LOSSES AND COSTS Total Estimated Clinical Cases Total Anaplasmosis Losses and Costs Extrapolation of Disease Costs Extrapolation of Prevention Costs CONTROL PROGRAM COMPARISONS AND BENEFIT/COST RATIOS CONCLUSIONS ACKNOWLEDGMENTS LITERATURE CITED‘ SUMMARY Anaplasmosis is a bovine disease that creates physical and financial losses for some Texas cattle producers. The incidence of anaplasmosis, the extent of loss, the regions of the state where loss occurs, and the value of preventive measures have not been documented previously. This study was designed to provide benchwork data for analyzing the anaplas- mosis problem in Texas. Two questionnaire survEys, one mailed to veteri- narians and one to beef cow/calf producers, provided the basic data for this study. Tabulation determined that Texas could be divided into three areas with respect to the incidence of anaplasmosis: (1) where clinical cases of anaplasmosis were not reported or rarely reported, (2) where clinical cases were few to moderate in number, and (3) where there was a high number of cases. In 1980, the incidence of clinical cases of anaplasmosis in Texas was estimated to be 0.276 percent of the adult breeding cattle. The occur- rence of anaplasmosis peaked in the summer season in Texas, but the seasonal occurrence of the disease varied considerably among regions within Texas. Survey results indicated that winter ticks, horseflies, and, to some extent, mosquitoes were the vectors transmitting anaplasmosis. Losses sustained by the producer survey respondents averaged $424 per clin- ical case as a result of death, weight loss, chronic cases, and/or abortion. The direct cost of anaplasmo- sis to Texas beef producers during 1980 was es- timated to be $6.37 million. Preventive measures cost- ing $2.59 million made the total cost of the disease equal to $8.96 million. The three most common alternative preventive measures used by producers in 1980 included (1) vaccination, (2) low-level chlortetracycline, and (3) vector control. Estimated benefit/cost ratios, which show the dollars returned per dollar expended, ranged from 3.8 to 4.0 for vaccination, low-level chlortetracycline, and vector control. The exception was the benefit/cost ratio of 2.2 for low-level chlortet- racycline when used in herds of more than 300 head. KEYWORDS: Anaplasmosis/beef cattle/physical loss/economic losses/treatment costs/preventive measures/benefit-cost ratios/vectors/clinical CESES Economic and Epidemiological Implications of Anaplasmosis in Texas Beef Cattle Herds Fred ]. Alderink and Raymond A. Dietrich* INTRODUCTION Anaplasmosis is a disease in cattle that creates physical and financial losses for cattle producers. Anaplasma marginale, the primary micro-organism causing the disease, parasitizes erythrocytes of cattle. Transmission of the disease agent is accomplished by vectors transferring minute amounts of blood from infected to susceptible cattle. Incubation is usually four to six weeks. When the host's immune response to the infected erythrocytes destroys some of its red blood cells, clinical signs of anaplasmosis become evident: anemia, marked fatigue, jaundice, anorexia, and fever. The hosts of known importance of Anaplas- ma marginale in the U.S. are cattle and the Columbian black-tailed deer. Physical losses from anaplasmosis in cattle in- clude death and, in survivors, weight loss, chronic cases, and abortion. The extent of these losses is dependent on the annual incidencel of anaplasmosis. Incidence is affected by the vectors and the reservoir of infection. The primary vectors of anaplasmosis in Texas are certain species of ticks, horseflies, and mosquitoes. The number and activity of these vectors is related to weather and associated ecological factors. Consequently, incidence varies from year to year and among different ecological regions. Control measures often used by producers against anaplasmosis in- clude vaccination, feeding of low-level chlortetracy- cline, vector control, and oxytetracycline injections. The Problem Published information concerning physical and economic losses attributable to anaplasmosis is sketchy in scope; often it includes undocumented estimates. McCallon (1973) estimated that annual losses due to anaplasmosis in U.S. cattle herds to- taled $10O million. Vaughn (1973) reported a $10 million loss in Texas in 1968. Neither of these figures was based on formal research, but on the best opin- ions of experts in the field. *Respectively, veterinarian, Veterinary Services, APHIS, USDA, and associate professor, Texas Agricultural Experiment Station (Department of Agricultural Economics), College Station. ‘Incidence as used in this Bulletin is the percent of the cattle over two years of age diagnosed as becoming clinically affected with anaplasmosis during the period of one year. This study was designed to develop detailed information on the economic costs of anaplasmosis to Texas cattle producers. The study also was designed to determine the incidence of anaplasmosis within Texas, associated physical and economic losses, pre- ventive measures and costs, and estimates of benefits from applying various preventive measures. Source of Data Two mail questionnaires, one to practicing veter- inarians and one to cattle producers, were designed to obtain the necessary data for this study. A random sample of 307 veterinarians was selected by using a random number table. The veterinarians sampled were licensed practitioners whose practice included 5O percent or more large animals. A random sample of 2,297 producers was drawn in cooperation with the Texas Department of Agriculture and the U.S. De- partment of Agriculture. The questionnaires were designed to include only cattle two years and older since cattle under two years of age either do not show clinical anaplasmosis, or show only mild disease with minimum loss. The data obtained from the survey were retros- pective in type. The producer responses were divided into two categories: (1) herds with a recent history of anaplasmosis and (2) herds with no recent history of anaplasmosis. Herds with a recent history of anaplas- mosis were defined as herds with clinical casesz dur- ing 1978-80. Therefore, herds with no clinical cases in 1980 were classified as having an anaplasmosis prob- lem if they had cases in 1978 or 1979. However, estimates of clinical cases, death loss, abortions, chronic cases3, and costs for treatment and preven- tion reported by producers were based on calendar year 1980 to develop annual estimates. The veterinar- ian responses were based on what they considered to be historically a typical year during 1978-80. zClinical cases were determined by the veterinarian in their survey and by the producer's veterinarian or the producer in the produc- er survey. Subclinical cases are cases that can be detected by serology, but do not show overt signs of disease and consequently no noticeable economic loss. 3Survivors normally recover in one to three months. Chronic cases are defined as survivors that require more than three months to regain lost weight. TABLE 1. COMPARISON OF VETERINARIAN AND PRODUCER RESPONDENTS TO THE RANDOM FOLLOW-UP SAMPLE OF NONRESPON- DENTS, BY GEOGRAPHIC AREA OF INCIDENCE, TEXAS, 1980 Veterinarians“ Producersb Follow-up Follow-up Variable Respondents Sample Respondents Sample Number of usable responses 83 16 499 67 Number of respondents reporting anaplasmosis 58 12 78 6 Number of responses from Area 1° 12 3 107 18 Number of responses from Area 2d 45 8 280 35 Number of responses from Area 3e 26 5 112 14 Total cases reported 1,290 198 231 2 Total cases reported from Area 1 & 2 315 67 42 0 Total cases reported from Area 3 975 128 189 2 “Veterinarian chi-square statistic = 0.5636. “Producer chi-square statistic = 3.425. "dflGeographic areas of incidence as delineated in Figure 3. Eighty-three veterinarians returned usable ques- tionnaires for a response rate of 27% (Table 1). The 2,297 cattle producers surveyed returned 580 ques- tionnaires, of which 499 were usable, for a response rate of 21.7%. The unusable responses were almost all from producers who had quit the cattle business or only had feeder cattle for grazing purposes. The lone dairy respondent was deleted, making this a survey of beef producers only. A follow-up survey of the nonrespondents ac- complished by telephone determined the respon- dents were representative of the two random sam- ples. The follow-up samples were composed of 24 veterinarians and 88 producers. Both follow-up sam- ples were selected from the nonrespondents by using a random number table to insure randomness. The correlation with respect to location of anaplasmosis between the respondents and nonrespondents with a history of anaplasmosis during 1978-80 was very close (Table 1). In additon, respondent and nonres- pondent characteristics with respect to herd size were also very similar. EPIDEMIOLOGICAL RESULTS The three factors necessary for clinical cases of anaplasmosis to occur are: (1) the disease agent, (2) susceptible hosts, and (3) a vector to transmit the agent. Any one of the factors alone or their interrela- tionship affects the incidence of clinical cases and accompanying economic costs to the producer. The seasonal occurrence 0f disease losses affects produc- ers financially due to the seasonal price variation for cattle. The relationship between epidemiology and economic costs of anaplasmosis holds especially when methods of control are considered. Different preventive measures have different epidemiological effects on disease because they vary as to which factor for disease occurrence they are designed to control. For this reason, each preventive method may have a different effect on incidence; however, each method also has a different economic cost to the 2 producer. The economics and epidemiology of the disease are inseparable. Areas of Anaplasmosis The incidence of anaplasmosis varied greatly among regions within Texas during 1980. Both the distribution and area delineation of clinical anaplas- mosis reported by practicing veterinarians (Figure 1) closely resembles the survey results reported by pro- ducers (Figure 2). In general, the northeast region of Texas and the eastern portion of the Edwards Plateau had a heavy concentration of veterinarian-diagnosed anaplasmosis cases and a high number of producer farms on which the disease occurred. Producer re- sponse from the northern section of the Gulf Coast was low, but half of the producers who did respond reported a problem with the disease. These results support the high concentration of cases per year as reported by veterinarians on the north Gulf Coast. The remainder of Central and East Texas shows scattered locations of clinical cases (Figures 1 and 2). Apparently, a much higher proportion of cattle and ranches are free of losses from anaplasmosis here than in Northeast Texas and the eastern Edwards Plateau. West Texas, part of South Texas, and a small region southeast of the Edwards Plateau were almost devoid of the problem. Texas can be divided into three major areas by incidence with respect to the concentration of ana- plasmosis cases as reported by veterinary practition- ers and producers (Figure 3). These are classified as follows: Area 1: clinical cases not reported or rarely reported; Area 2: clinical cases less than 1 percent incidence; and Area 3: high number of cases, ranging from 0.6 percent to 2.2 percent incidence. Incidence by Areas The population base of individuals at risk is necessary to calculate incidence figures. Since veteri- narians were unsure of the number of cows in their practice area, the veterinarian survey was not used to Each dot = 1 case per year Figure 1. Distribution of clinical anaplasmosis cases during 1978-80 as reported by a random survey of 83 veterinary practitioners and a telephone survey of 65 veterinary practitioners, Texas, 1980“. “The 65 veterinarians were selected to include parts of Texas not covered by the random survey and to determine the boundaries of the areas with a high number of cases. determine incidence. Therefore, all incidence figures are derived from the random producer survey. Total producer survey respondents reported 231 clinical cases of anaplasmosis during 1980 in 90,903 head of cattle at risk to the disease, or an overall incidence of 0.254 percent (Table 2). Producer and veterinarian surveys concurred on variation of inci- dence in the three areas shown in Figure 3. The white Area 1 (including Subareas 1a and 1b) shows the regions from which veterinarians and producers re- ported no clinical cases of anaplasmosis except for two small localities in West Texas and the Panhandle, indicated by shaded areas. Subarea 1b, which has a high concentration of beef cows (Figure 4), had no reports of any clinical cases. With the increased ex- change of cattle within Texas today, however, carrier cattle from infected areas have very likely been moved into Subarea 1b. Insufficient vector numbers and vector activity is the most logical explanation for the lack of reported clinical cases in this subarea. The overall incidence in Area 2 is less than 0.1 percent of the cattle population two years and older in that area (Table 2). Portions of Area 2 adjoining boundaries of Area 3 have more reported cases (see Figure 1 for distribution of cases). Area 3 with its high incidence of 1.2 percent is divided into four subareas (Table 2 and Figure 3), which are different in ecology and geographically separated. Area 3 contained 81.8 percent (189 of 231) of the clinical cases of anaplasmosis reported by the 3 Herd Size: I 1 to 19 head 20 to 49 head O 50 to 99 head O = 100 to 199 head A = 200 to 499 head Q = 500 or more head Figure 2. Location and herd size of 78 beef producers from a random survey of producers reporting an anaplasmosis problem, Texas, 1980. producer respondents (Table 2). Subarea 3 represents the eastern half of the Edwards Plateau, which has relatively rough terrain and an arid climate. At 2.2 percent, Subarea 3a has the highest incidence in the state (Table 2). Producer operations in that area are range type and quite dispersed. Subarea 3b, which has an incidence of 0.6 percent, is in the Blacklands with extensive cropland and concentrated livestock operations. Northeast Texas, Subarea 3c, with a rela- tively high concentration of livestock, has approxi- mately a 1 percent incidence of anaplasmosis. The northern part of the Gulf Coast, Subarea 3d, has a subtropical climate and heavy rainfall, and relatively heavy stocking rate. It revealed an incidence of slight- ly more than 1 percent. 4 The percent of herds reporting anaplasmosis and the incidence within herds reporting clinical cases follow the same pattern as area incidence; both were higher in Area 3 than in Area 2 (Table 3). This was to be expected. The incidence within herds reporting clinical cases in Area 2 and Subarea 3b (1.2 percent and 1.0 percent, respectively) is similar to the inci- dence Safford (1965) and Utterback et al. (1973) re- ported. Herds with clinical cases in Subareas 3a, 3c, and 3d reported an incidence of 3 to 5 percent (Table 2). Incidence by Herd Size Larger herds appear to sustain anaplasmosis in- fection more persistently than smaller herds, as the El = Area 1, incidence is rare a = Area 2, incidence averaged less than 1 percent fi = Area 3, incidence ranged from .6 percent to 2.2 percent Figure 3. Delineation of anaplasmosis areas according t0 number 0f clinical cases, Texas, 1980. percent of herds reporting clinical cases increased as herd size increased (Table 3). In Area 2, herd infec- tion rates4 averaged 3 percent in herds with less than 200 head, but it ranged from 7 to 1O percent in herds with 200 or more head. In Area 3, the proportion of herds reporting the disease was much greater than in Area 2. Herd infection rates ranged from 9 to 3O percent in herds with less than 200 head while herd infection rates were 50 percent or higher in herds with 200 or more head. High absolute numbers of carriers in a herd probably increases the odds of transmission of Anaplasma marginale from carriers to 4Herd infection rate is the percent of the herds reported to have clinical cases of anaplasmosis during 1980. susceptible individuals. For example, 4O percent car- riers in a herd of 400 (160 head) would provide a much larger reservoir of infection than would 40 percent in a herd of 4O (16 head). Incidence and herd size, however, had a nega- tive relationship as larger herds revealed lower inci- dence than smaller herds. Incidence in herds in Area 3 averaged 6 percent in herds under 200 head, where- as it decreased to less than 1 percent in herds over 500 head (Table 3). Seasonal Occurrence In order to attribute clinical cases to the season in which transmission by the vectors occurred, several months were taken out of traditional context. For 5 TABLE 2. NUMBER OF BEEF HERDS AND BEEF CATTLE, NUMBER OF CLINICAL CASES OF ANAPLASMOSIS, RANDOM SURVEY OF BEEF PRODUCERS, TEXAS, 1980 Number Cattle Clinical of In Cases In % Herds % Incidence in Producer Respondent Respondent Incidence‘ Reporting Herds Reporting Area“ Respondents Herds Herds (%) Anaplasmosis Clinical Cases Area 1 101 25,365 4 0.0158 2.0 0.27 Subarea 1a 73 20,745 4 0.0193 2.7 0.27 Subarea 1b 28 4,620 0 -- 0 -- Area 2 286 50,153 38 0.0758 10.1 1.2 Area 3 112 15 385 189 1.228 42.0 2.9 Subarea 3a 28 4,110 91 2.214 43.0 5.2 Subarea 3b 21 3,622 23 0.6350 57.1 1.0 Subarea 3c 52 5,055 47 0.930 34.6 3.2 Subarea 3d 11 2,598 28 1.078 45.5 3.2 Total Survey 499 90,903 231 0.254 15.6 2.1 “Geographic areas of incidence as delineated in Figure 3. “Clinical cases were determined by the producer’s veterinarian or the producer in the producer survey by whatever methods they used to arrive at a diagnosis. ‘Incidence is the percent of the cattle over two years of age diagnosed as becoming clinically affected with anaplasmosis during the period of one year. TABLE 3. PERCENT OF BEEF HERDS REPORTING CLINICAL CASES OF ANAPLASMOSIS, INCIDENCE WITHIN HERDS, BY GEOGRAPHIC AREA OF INCIDENCE AND HERD SIZE, RANDOM SURVEY OF BEEF PRODUCERS, TEXAS, 1980 Area 2 Area 3 % Incidence % Incidence Herd Size Number % Herds in Herds Number % Herds in Herds in Number of Reporting Reporting of Reporting Reporting of Head Herds Clinical Cases Clinical Cases Herds Clinical Cases Clinical Cases 1-19 42 4.8 8.6 10 O -- 20-49 45 2.2 2.3 23 8.7 6.7 50-99 67 3.0 3.3 31 19.3 4.6 100-199 46 2.2 0.57 23 30.4 6.5 200-499 59 10.2 1.4 18 50.0 3.4 500+ 27 7.4 0.54 7 57.1 0.7a example, September was declared a summer month TABLE 4. SEASONAL OCCURRENCE or CLINICAL CASES or SO the Cases diagnosed during Inonth would be ANAPLASMOSIS DURING A TYPICAL YEAR, RANDOM SAMPLE assigned to the horseflies responsible for transmis- OF VETERINARIANSJEXAS’197380 sion of Auaplasma marginale during August. Cases Cases occurring in October and November (fall) were the Occuring in result of transmission in September and October Edwards Plateau Cases l" Area? Total Cases when mosquitoes were suspected as the primary Seam" (Subama 3a) “d A'°a53b‘d Repmted vector. March was designated a winter month be- Number % Number % Number % cause cases occurringduring this month were most Winterb 103 492 72 627 175 13b likely the results of winter tick activity in February. - c h _ _ 2 Spring 39 18.7 131 12.1 170 13.2 T e data from the veterinarian survey showing Summera 44 2m 619 57.3 663 514 the seasonal ‘occurrence of anaplasmosis in Texas 1S pane 23 110 259 23,9 232 213 summarized in Table 4. Summer was the peak season T0131 209 100_0 1,031 100_0 1,290 100,0 for anaplasmosis in Area 2 and most of Area 3 during 1978-80, followed by fall, spring, and winter. The “Months in which clinical cases occurred were assigned to the season of vector transmission of Anaplasma marginale. peak season in the Edwards Plateau (Subarea 3a), in bwinte, = Decembfl, Janwy, February, Marc}, contrast, occurred in winter. The extent of the winter ‘Spring 1 April, May, lune. concentration of cases in the Edwards Plateau is dSummer = ]uly, August, September. highlighted by the fact that the Plateau accounted for “Fall = October, November. 6 Each dot = 1,000 head Source: 1980 Texas Livestock Dairy and Poultry Statistics of Texas Crop and Livestock Reporting Service. Figure 4. Distribution of beef cows that have calved, Texas, Ianuary 1, 1980“ “The eastern Edwards Plateau is outlined in the center of Texas. about 9 percent of the Texas beef cows in 1980, but accounted for 50.9 percent of the clinical cases diag- nosed in Texas during the winter months. By con- trast, the Plateau accounted for only 6.6 percent of the summer cases in Texas. The Gulf Coast, in contrast to other regions of Texas, represents a region where more cases occurred in the fall than any other season. Veterinarians from the Gulf Coast reported 1, 10, 15, and 18 cases in the winter, spring, summer, and fall, respectively. In areas of Texas that experienced clinical cases of anaplasmosis during the winter in the absence of the winter tick, Dermacentor albipictus, veterinarians often reported stress as a factor causing asymptomat- ic carriers to break into clinical symptoms. The causes of stress most commonly implicated were parturition, severe malnutrition, and heavy lactation. The producer survey corroborated the veterinari- an survey as to seasonality of anaplasmosis. Of the 36 producers reporting the months during which the majority of their cases occurred, 21 designated the summer months. Of the seven producers who desig- nated winter as the severe anaplasmosis season, five were from the Edwards Plateau. None of the 21 producers designating the summer months ranched in the Edwards Plateau. Vectors Because all other practical vectors of Anaplasma marginale are inactive during the winter (except for 7 humans), the circumstantial evidence incriminating the winter tick, Dermacentor albipictus, is difficult to refute. Seven 0f twelve veterinarians suspecting ticks as the primary vector during the winter were located in the Edwards Plateau area. This is not the first time Dermacentor albipictus has been suspected as a natural vector of anaplasmosis. Edwin (1963) believed the winter tick was a vector in the ”Hill Country” of Texas (Edwards Plateau). However, Teel (1981) had found that the winter tick range in Texas is not restricted to the Edwards Plateau, although veterinar- ians in other areas of the state seldom reported it as a vector. Horseflies were identified as the principal vector by three-fourths of the veterinarians specifying vec- tors for ]une through October. During September and October, six veterinarians, three of whom practiced in the Gulf Coast area, suspected mosquitoes as the main vector. Since the absolute numbers of vectors and their efficiency in transmitting Anaplasma marginale is im- portant with regard to incidence, regional variation in incidence over the state is probably affected more by the numbers and activities of vectors than any other factor. With transfer of cattle due to sale and pur- chaser, and to ranchers moving cattle between widely separated land holdings, it is unlikely that any area of the state is devoid of anaplasmosis carrier cattle. Therefore, it is highly probable that vector activity, or lack of it, is of prime importance in determining whether clinical cases are present in an area. Der- macentor albipictus appears to be an efficient vector in the Edwards Plateau. Except for Jasper and Newton Counties, Subarea 3d coincides with the rice-growing area of Texas. This makes the black riceland mos- quito, Psorophora columbiae, a suspect as a vector. Olson5 (personal communication, 1981) states that this mosquito prefers the bovine species to other mammals as its host. Davis (1981) reported Tabanus abactor comprised over 97 percent of the horsefly species present in approximately a four-county-wide strip on the west side of Area 2 (Figure 3). This strongly incriminates T. abactor as the only summer vector in that region. According to Thompson (1977), Tabanus sulcifrons is a common species in the central part of Area 2, includ- ing Subarea 3b. Tabanus fusicostatus and T. lineola (Thompson, 1974) are present in high numbers in the Pineywoods area of Northeast Texas. The greenhead, T. nigrovittatus (Thompson, 1973), is the dominant species along the coast; however, in a transmission study by Wilson it failed to transmit Anaplasma mar- ginale. Thompson (1977, 1974, 1973) recorded the presence of many other tabanid and Chrysops spp. (deerflies) in these areas. Vector activity, relatively low in most of Subarea \1a, is postulated as low or ineffective in transmission of the disease agent in Subarea 1b. 5]immy K. Olson, Toxicology and Entomology Research Laborato- ry, College Station, Texas: USDA. 8 TABLE 5. CATTLE CLASSES, AVERAGE PRICES, AND WEIGHTS FOR FIVE MARKETS“ 1980 Price Per Head or per 100 Pounds of Class Liveweight (cwt.), $ Weight, lb. Brood Cow $ 575.00/head 900 Replacement bull 1,2S0.00/headb NA Weaner heifer calf 69.00/cwt. 350 Weaner steer calf 81 .50/cwt. 425 Canner cow 32.00/cwt. 800 Cutter cow 43.00/cwt. 900 Slaughter bull, low boning 49.00/cwt. 1,250 Slaughter bull, average boning $ 58.00/cwt. 1,425 “San Antonio, Sealy, Madisonville, Terrell, Sulphur Springs. “The average price for a replacement bull was assumed to be $1,250. PHYSICAL AND ECONOMIC LOSSES Physical losses associated with anaplasmosis, which also translate into direct costs to producers, include death, weight loss, chronic cases, and abor- tions. Additional direct expenses include veterinary service, labor and management, drugs, and added husbandry given to the clinical cases. In order to estimate direct costs associated with physical losses, it was necessary to estimate prices for various classes of cattle. Cattle prices were estimated from weekly quotations reported by the Texas Live- stock Market News for 1980. An average price was derived for each class using market quotations from the San Antonio, Sealy, Madisonville, Terrell, and Sulphur Spring markets. The classes, average prices, and weights used in this study appear in Table 5. Death Loss The producers reported a death rate of 35.9 per- cent in the 231 clinical cases during 1980 (Table 6). Of the 83 deaths reported, 75 were cows and 8 were bulls. Therefore, bulls comprised 9.6 percent of the death losses although they made up only 4 percent of the adult bovine populationf’ This suggests that bulls are more susceptible to anaplasmosis than cows, which may be due to a sex difference or to a lack of exposure to Anaplasma marginale when young, an exposure that local heifers are more likely to experi- ence. For example, producers in Area 3 may purchase breeding bulls from breeders in nonanaplasmosis areas (Area 1). Heifers retained in herds located in anaplasmotic areas develop a natural immunity to anaplasmosis in contrast to bulls obtained from nonanaplasmotic areas. Replacement bulls for breeding were valued at $1,250 per head in this study. The average brood cow in 1980 was estimated to weigh 900 pounds (lb) and was valued at $575 per head. Death losses attributed to anaplasmosis by producers responding to the sur- vey were estimated to total $53,125 in 1980 (Table 6). °Assumes a 25 to 1 cow/bull ratio. Weight Loss The average weight loss reported per head be- cause of anaplasmosis was 190 pounds (lb). The esti- mates ranged from 75 lb to 350 lb. The estimated value of weight loss in cows was based upon the average market value 0f cutter-grade cows of $43 per hundredweight (cwt) in 1980, for a loss in value of $81.70 per cow. Bulls were estimated to lose 300 lb at $58/cwt, which amounted to a per head loss of $174. The 148 surviving clinical cases reported in the pro- ducer survey consisted of 133.8 cows and 14.2 bulls. The total loss in value due to weight loss for these surviving clinical cases amounted to $13,402 (Table 6). Chronic Cases Producers were asked to report the number of clinical anaplasmosis cases that survived but re- mained ”chronic” and culled as a result of that condi- tion. Cattle convalescing from anaplasmosis have a long recovery period to replace lost erythrocytes and regain weight. Cattle that did not regain their weight were classed as chronic cases. Twenty-eight percent, or 42 of the 148 survivors, were classified as chronic cases. The grade and weight used for estimating the value of a cow that became a chronic case was a canner cow weighing 800 lb at $32/cwt ($256). Fur- ther, a stock cow that recovered and regained her lost weight was estimated to weigh 900 lb and was valued at a cutter price of $43/cwt or $387 per head. Conse- quently, a cow with a chronic case of anaplasmosis was estimated to be worth $131 ($387 minus $256) less than the cow that clinically recovered. A chronically affected bull would not be considered satisfactory for breeding and would have to be replaced. Such a bull at an assumed weight of 1,251 lb and a slaughter bull price of $49/cwt would have a market value of $612.50. A bull with a chronic case was estimated to be worth $637.50 ($1,250 minus $612.50) less than the replacement breeding bull. The 42 chronic cases were composed of 4 bulls and 38 cows. Producer losses as a result of anaplasmosis cases becoming chronic for cows was $4,978 and for bulls was $2,550, for a total loss of $7,528 (Table 6). Abortions It was noted previously that producers surveyed reported 231 clinical cases in 1980 which resulted in 83 deaths. The 148 survivors were estimated to con- sist of 133.8 cows. The Texas Crop and Livestock Reporting Service statistics revealed an 84 percent calf crop average during 1976-80 in cows that had calved. Thus, of the 133.8 surviving cows, 84 pecent or 112 would normally be carrying a calf. The 32 reported abortions resulted in an abortion rate of 28.6 percent among the 112 pregnant cows. The 1980 Texas Livestock Statistics indicate mor- tality between birth and weaning in Texas beef calves averaged 5 percent. Therefore, 2 of the 32 aborted TABLE 6. NUMBER OF CLINICAL CASES OF ANAPLASMOSIS, BY TYPE OF PHYSICAL LOSS, ASSOCIATED DOLLAR LOSS AND TOTAL DOLLAR LOSS, AND TREATMENT COST, RANDOM SUR- VEY OF BEEF PRODUCERS, TEXAS, 1980 Number of Clinical Value Per Total Cases and Case or Survey Physical Physical Losses Item Losses Loss and Costs“ Death Loss Cows 75 $ 575.00 $43,125 Bulls i 1,250.00 10,000 Totals 83 53,125 Survivors 148 -- Weight Loss ‘ Cows 133.8 81.70 10,931 Bulls 174.00 2,471 Totals 148.0 13,402 Chronic Cases Cows 38 131.00 4,978 Bulls _4_ 637.50 2 550 Totals 42 7,528 Abortions Heifer calves 15 241.50 3,622 Steer calves Q 346.00 5 190 Totals 30 8,812 Cost of Treatment and Labor 231 65.44 15,117 Total 231 $ 424.1%’ $97,904 ‘Total survey losses and costs are an intermediate calculation to obtain the average value per clinical case of $424.17. bAverage value per clinical case. calves would have been expected to die if they had been born alive. The reduction in calf crop attribut- able to anaplasmosis-induced abortion, then, is 26.8 percent among the 112 surviving pregnant cows es- timated from the producer survey. Economic losses for these 30 calves were estimated as follows, assum- ing a sex ratio of 50:50. For heifer calves: 15 heifer calves at an average weight of 350 lb >< $69/cwt = $241.50, or a total loss of $3,622. The value of steer calves was estimated using an average weight of 425 lb >< $81.50/cwt = $346 for a total of $5,190 for 15 steer calves. The total value of the calves lost by the respondents to anaplasmosis-attributed abortion was $8,812 (Table 6). TREATMENT AND PREVENTIVE MEASURES AND COSTS Treatment Costs Four variables that were used to estimate the cost of treatment are (1) cost for veterinary service, (2) drug costs, (3) owner-estimated value of labor and management required to handle the sick and dead, and (4) the number of head treated and/or handled. Twenty-one producers reported cost data for all four variables as follows: Total cost of veterinary service $2,434 Total drug cost 1,988 Total labor and management cost 3,955 Total cost of treatment $8,377 These 21 producers had 128 cases for an average per head treatment and labor cost of $65.44. The treat- ment and labor cost for the 231 clinical cases reported in this study was estimated to total $15,117 (Table 6). Preventive Measures and Costs The three alternative methods commonly used by producers to prevent anaplasmosis included (1) vaccination, (2) feeding low levels of chlortetracyc- line, and (3) vector control. Oxytetracycline injections were used to a lesser extent. The method or combina- tion of methods chosen by a producer depends on which method is more adaptable to his ranch opera- tion, economics, and his personal preference. Only data from herds with a reported anaplas- mosis problem were used to evaluate the different control methods. Herds were assigned to the princi- pal control method utilized. For example, herds in which vaccination was the primary method of con- trol, although spraying was also used to control horn flies, were assigned to vaccination only and not to vector control. Similarly, herds using intensive vector control measures and vaccination of bulls for anaplas- mosis were not included in the vaccinating category but were placed under vector control. Further, re- spondents assigned to the control program listed used the program for more than one year. Vaccination The seven herd owners who relied predomi- nantly on vaccination, vaccinated 1,472 head in 1980 TABLE 7. ANAPLASMOSlS CONTROL METHODS UTILIZED, BY NUMBER OF HERDS, NUMBER OF BEEF CATTLE, AND ANNUAL COST PER HEAD, RANDOM SURVEY OF BEEF PRODUCERS, TEXAS, 1980 Number Number Annual Cost Control Method of Herds“ of Cattle per Head No controlb 20 5,761 NA Vaccination 7 3,593 $1.73 Low-level chlortetracycline 22 3,824 2.88 Oxytetracycline injections 6 820 2.04 Vector control Vector Control 1‘ 8 1,290 1.95 Vector Control 2°‘ 1e 2,794 $4.53 “Only herds in which the specified method was the principal means of anaplasmosis control are included in this column. bNo control includes herds using vaccine in a minor way such as vaccinat- ing bulls only, plus herds on low-level chlortetracycline 0r vector control each at a cost equal to or less than $1.00 per head annually. ‘This category of producers spent from $1 to less than $3 annually per head for vector control. “This category spent $3 or more annually per head for vector control. 10 at a cost of $2.91 per dose of vaccine and $1.32 per head for labor, for a total cost of $4.23 per head vaccinated. However, these producers did not vacci- nate all their susceptible cattle annually. The seven herds consisted of 3,593 head that were protected by a $6,225 annual vaccination cost. This lowered the annual cost per head protected to $1.73 (Table 7). The total amount of vaccine used by respondents, whether it was the primary control method or not, was 2,071 doses for a total cost of $9,008.85 for the vaccine and labor. Anaplaz7 was the only vaccine used by the pro- ducers surveyed. Premunition with infected blood as a vaccination method was not reported by any of the respondents. Low-Level Chlortetracycline Twenty-two producers, most of whom resided in Northeast Texas (Subarea 3c), used low-level chlortet- racycline in a feed or mineral mix as the primary method of control. Brock (1957) was one of the first to demonstrate that clinical anaplasmosis is effectively prevented at the 1.1 milligram per kilogram of body weight per day (0.5 mg/lb/day) level of chlortetracy- cline ingested daily. The 22 producers using the low- level chlortetracycline as the primary method of con- trol reported an annual cost of_.$2.88 per head for a total cost of $11,013 during 1980 (Table 7). Some respondents fed low-level chlortetracycline to select- ed animals in the herd which increased the reported cost of this preventive measure to $12,499. However, the total cost of low-level chlortetracycline for all respondents using it (the 22 producers plus those using it in a more incidental manner) totaled $12,499. Vector Control From the survey data, it was determined that vector control that cost less than $3 per head annually had limited effectiveness in reducing the incidence of anaplasmosis cases. This level of usage was desig- nated ”Vector Control 1" (Table 7). Vector control at a cost of $3 or more per head per year was designated ”Vector Control 2.” Both Steelman (1977) and Turner (1972) determined that insect or tick control — by relieving cattle of the pain, worry, and blood loss — increases production more than enough to compen- sate for the labor and overhead required to spray or dip cattle. Therefore, only the cost of the insecticide was considered a liability of anaplasmosis control. Of the 16 producers using Vector Control 2 as the princi- pal preventive measure, 9 ranched in areas where the winter tick was the most likely vector and 7 where horseflies were the most probable vector. This sug- gests that both of these vectors may have their ana- plasmosis transmission efficiency reduced by an ec- toparasite control program. For extrapolation purposes, vector control at an average annual cost of $1.95 per head will not be considered as a means to control anaplasmosis, but 7Amzpluz is the proprietary name for the vaccine produced by Fort Dodge Laboratories, Fort Dodge, Iowa. rather to reduce the other economic losses attribut- able to ectoparasites such as bite worry and blood loss. The $3 and greater per head cost for insect and tick control will be utilized for estimating state-wide costs since control at these cost figures provided desired protection levels. The total expenditure for vector control to prevent anaplasmosis reported by the survey respondents was $12,650 or $4.53 per head per year. Oxytetracycline Injections The survey results of oxytetracycline injections as a control measure appear questionable mainly because the number of producers (six) reporting us- ing it as their primary method of control was low. Also, the average cost per head injected at $2.04 appears low (Table 7). Subtracting $1.05 per head for labor to inject the cattle results in only a $1.00 per head cost for the oxytetracycline. Oxytetracycline injections are used two ways. One method is to inject the herd every 29 to 30 days during the vector season. This method takes advan- tage of anaplasmosis’ long incubation period, which is usually four to six weeks. One injection will subdue the infection in an animal that has been exposed and is incubating the disease. If this animal is reinfected a few days after the injection, theoretically it would not become ill until 30 to 40 days later. However, if the animal receives another injection of oxytetracycline prior to the end of the 30- to 40-day incubation period, it would be protected from clinical disease for another month. Another technique for using oxytetracycline as a preventive measure is to wait until the first clinical case appears in the herd and then inject the entire herd. If the first clinical case appears early in the vector season, injections will have to be repeated at 30-day intervals. If the first case appears toward the end of the vector season, the herd will need to be treated only once. A practical application of this method may be used where the horsefly, Tabanus abactor, is the pri- mary vector of Anaplasma marginale. This horsefly, known as the cedar fly, is a dryland horsefly ob- served by Sanders‘; (personal communication, 1981) which apparently does not emerge from its puparium without adequate rainfall. If the summer has average rainfall, the cedar fly emerges regularly in rather constant numbers. But often in the Rolling Plains of Texas, there are dry spells broken by a sudden heavy rain. When this happens, the cedar fly is thought to emerge in very small numbers during the dry spell. Then, a few days after the rain, it emerges in swarms, often with counts of over 100 flies feeding on each cow. When rainfall occurs after a dry spell, it may be possible to control anaplasmosis by giving the first injection of oxytetracycline to the herd approximately 30 to 35 clays after the rainfall. This would save “Darryl P. Sanders, Department of Entomology, Texas Tech Uni- versity, Lubbock. injecting the cattle during a dry summer before the first good rain. A combination of vaccination and oxytetracycline injections is often used on herds that have had no previous history of anaplasmosis and are experienc- ing their first outbreak. The oxytetracycline provides immediate protection, and the vaccine will provide immunity within three weeks. These herds were not included in either the vaccination or the oxytetracy- cline injection programs in Table 7. The survey results indicated 12 cattle producers used oxytetracycline injections as a primary means of control or in conjunction with another control meth- od. These 12 producers reported a drug cost of $3,175 along with $1,365 for administering the drug for a total of $4,540. TOTAL CLINICAL CASES, ANAPLASMOSIS LOSSES, AND COSTS Total Estimated Clinical Cases When the area incidences from the producer survey are weighted by the number of cattle at risk for each area, the incidence for Texas during 1980 was 0.276 percent (Table 8). Further, anaplasmosis clinical cases are estimated to have totaled 15,015 in Texas during 1980. Total Anaplasmosis Losses and Costs Extrapolation 0f Disease Costs The total physical loss to producers which in- cludes death, weight loss, chronic cases, and abor- tions totaled almost $5.4 million in 1980 (Table 9). The death loss of more than $3.4 million accounted for almost 64 percent of this loss. The cost of treatment which included veterinary service, drugs, and labor, approached $1 million and when added to the physi- TABLE 8. ESTIMATED TOTAL CLINICAL CASES OF ANAPLASMO- SIS, BY GEOGRAPHIC AREA OF INCIDENCE, TEXAS, 1980 1978 Cow Geographic Census Estimated Area of Adjusted lncidence Clinical Incidence for Bulls“ % Cases Area 1 1 465 578 4 Subarea 1a 1,093,567 -- 4 Subarea 1b 372,011 -- 0 Area 2 2,839,419 0.0758 2,152 Area 3 1 137,765 1.130 12 859 Subarea 3a 202,911 2.214 4,492 Subarea 3b 213,287 0.635 1,354 Subarea 3c 516,930 0.930 4,807 Subarea 3d 204,637 1.078 2,206 State Total 5,442,762’ 0.27s 15,015 “The Bureau of the Census "beef cows and heifers that have calved” were expanded to include bulls by assuming that Texas beef cattle herds contained one bull per 25 cows. “This total does not include 152,424 beef cows which were in the category, “farmers not on mail list,” of the 1978 Livestock Census, Bureau of the Census. 11 TABLE 9. TOTAL ESTIMATED ANAPLASMOSIS LOSSES, BY TYPE OF PHYSICAL LOSS, ASSOCIATED DOLLAR LOSS AND TOTAL DOLLAR LOSS, AND TREATMENT COST, BEEF PRODUCERS, TEXAS, 1980 Total Estimated Value per Total Clinical Cases Case or Estimated and Physical Physical Losses Item Lossesa Loss and Costs Death Loss Cows 4,873 $ 575.00 $2,801,975 Bulls 517 1,250.00 646,250 Totals 5,390 3,448,225 Survivors 9,625 -- -- Weight Loss Cows 8,701 81.70 710,872 Bulls 925 174.00 160 776 Totals 9,625 871,648 Chronic Cases Cows 2,463 131 .00 322,653 Bulls 261 637.50 166,387 Totals 2,724 489,040 Abortions Heifer calves 993 241.50 239,809 Steer calves 993 346.00 343 578 Totals 1,986 583,387 Cost of Treatment and Labor 15,015 65.44 982,582 Total 15,015 $ 424.57 $6,374,882 ‘The same proportion of physical losses to clinical cases was used as reported by the random survey of beef producers (Table 6). The total cases were derived in Table 8. cal losses resulted in a total loss and treatment cost of almost $6.4 million. Extrapolation of Prevention Costs Producers used four control methods in attempt- ing to prevent anaplasmosis, including vaccination, feeding low-level chlortetracycline, injecting oxytet- racycline, and vector control. Producers using these four control methods expended almost $2.6 million on preventing anaplasmosis in Texas during 1980 (Table 10). Survey respondents from Area 1 did not incur any of this expense; therefore, it is all attribut- able to prevention measures used in Areas 2 and 3. Feeding low-level chlortetracycline accounted for the largest statewide expenditure for prevention at al- most $900,000. Vector control placed second and vac- cination third in the estimated amount spent by beef producers on preventive measures during 1980. \ The sum of the losses due to anaplasmosis and cost of treatment ($6,374,882, Table 9) and the pre- vention costs ($2,589,411) resulted in an estimated total direct cost to Texas beef cattle producers equal to $8,964,293 during 1980. 12 TABLE 10. ESTIMATED TOTAL EXPENDITURES FOR ANAPLASMO- SIS PREVENTIVE MEASURES, BY METHOD OF CONTROL AND GEOGRAPHIC AREA OF INCIDENCE, TEXAS BEEF HERDS, 1980 Costs From Estimated Producer Total Cost Control Method Survey by Area“ Vaccination Area 2 $ 5,463.60 $ 309,322 Area 3 3 545.25 262 181 Totals 9,008.85 571,503 Low-level chlortetracycline Area 2 1,797.70 101,737 Area 3 111 7111.1111 791.3211 Totals 12,499.00 893,107 Oxytetracycline injections Area 2 408.00 23,099 Area 3 4 132.1111 3115.573 Totals 4,540.00 328,672 Vector controlb Area 2 8,160.00 461,979 Area 3 4 4911.1111 3§2,1M§ Totals $12,650.00 794,027 State Total $2,587,411 “Estimated cost by area = cost from producer survey X area expansion factor. Area expansion factor = area cattle population (Table 8)/area cattle population surveyed (Table 2). Area 2 expansion factor = 56.6151 = 2,839,419/50,153. bVector control is the same as the Vector Control 2 of Table 6. CONTROL PROGRAM COMPARISONS AND BENEFIT/COST RATIOS The data from this study show the results of the control methods as used by the producers respond- ing to the questionnaire. The producers apparently selected control programs dependent upon their management situation, available physical facilities, economics, and personal preference. Three prevention methods were compared in herds with an anaplasmosis problem by using the specified herd sizes of 122 and 553 head. The average size for herds less than or equal to 300 head is 122 head; 553 is the average for herds greater than 300 head. Vaccination revealed a slight advantage over low-level chlortetracycline feeding in the over-300- head herd-size group in Area 3 (Table 11). The results of the producer survey also showed that vaccination as a control method was equal to or slightly better than vector control in reducing incidence of clinical cases in both herd size groups in Area 2 (Table 12). The herds less than or equal to 300 head in Area 3 in which vector control was used had an incidence of 0.659, considerably lower than the incidence of 1.549 TABLE 11. ANAPLASMOSIS CONTROL METHODS UTILIZED IN AREA 3, BY NUMBER OF HERDS, NUMBER OF BEEF CATTLE, NUMBER OF CLINICAL CASES AND INCIDENCE, AND BY HERD SIZE AND ESTIMATED CLINICAL CASES IN TWO SPECIFIED HERD SIZES, RANDOM SURVEY OF BEEF PRODUCERS, TEXAS, 1980 Herd Size s 300 % Reduction in Estimated Cases From N0 Number Total Number Cases in a 122 Control in a Method of Herdsa Cattle of Cases Incidence Head Herd“ 122 Head Herd No control 5 532 19 3.571 4.357 NA Vaccination 0 - - - - - Low-level chlortetracycline 16 1,549 24 1.549 1.891 56.6% Oxytetracycline injections 4 510 4 0.392 - - Vector control‘ 7 910 6 0.659 0.804 81.5% - % Reduction in Herd Slze > 300 Estimated Cases From N0 Number Total Number Cases in a 553 Control in a Method of Herds“ Cattle of Cases Incidence Head Herd“ 553 Head Herd No control 4 1,950 28 1.436 7.941 NA Vaccination 2 1,250 3 0.240 1.327 83.8% Low-level chlortetracycline 4 1,725 6 0.348 1.924 75.8% Oxytetracycline injections 0 - - - - - Vector control‘ 0 - - - - - ‘Number of herds represents the number 0f producers using the method specified as their principal method 0f control. “Herd size of 122 head is the average size of all herds s 300 head using a control method or no control. ‘Vector control is the same as the Vector Control 2 of Table 7. “Herd size of 553 head is the average size of all herds > 300 head using a control method or no control. TABLE 12. ANAPLASMOSIS CONTROL METHODS UTILIZED IN AREA 2, BY NUMBER OF HERDS, NUMBER OF BEEF CATTLE, NUMBER OF CLINICAL CASES AND INCIDENCE, AND BY HERD SIZE AND ESTIMATED CLINICAL CASES IN TWO SPECIFIED HERD SIZES, RANDOM SURVEY OF BEEF PRODUCERS, TEXAS, 1980 Herd Size s 300 % Reduction in ' Estimated Cases From No Number Total Number Cases in a 122 Control in a Method of Herds‘ Cattle of Cases Incidence Head Herd“ 122 Head Herd No control 8 1,279 24 1.876 2.289 NA Vaccination 3 493 1 0.203 0.247 89.2% Low-level chlortetracycline 1 50 0 - - - Oxytetracycline injections 2 310 3 0.968 - - Vector control‘ 6 709 2 0.282 0.344 85.0% Herd Size > 300 _ % Reduction in Estimated Cases From No Number Total Number Cases in a 553 Control in a Method of Herds“ Cattle of Cases Incidence Head Herd“ 553 Head Herd No control 3 2,000 5 0.250 1.3825 NA Vaccination 2 1,850 0 0 0 100% Low-level chlortetracycline 1 500 0 - - - Oxytetracycline injections 0 - - - - - Vector control‘ 3 1,175 0 0 0 100% ‘Number of herds represents the number of producers using the method specified as their principal method of control. “Herd size of 122 head is the average size of all herds s 300 head using a control method or no control. ‘Vector control is the same as the Vector Control 2 of Table 7. “Herd size of 553 head is the average size of all herds > 300 head using a control method or no control. 13 sustained by the herds 0n low-level chlortetracycline. Estimating the percent reduction in number of cases from no control that occur in herds of 122 and 553 head when using one of the three control meth- ods provides further comparison of the preventive measures. The effectiveness of vaccination and vector control are similar as revealed by a reduction of clinical cases of 8O to 100 percent in both herd sizes compared to herds not using control measures (Tables 11 and 12). Low-level chlortetracycline feed- ing as estimated in 553-head herds in Area 3 showed a 76 percent reduction of clinical cases while the 122- head herd size showed a 57 percent reduction com- pared to the no controls (Table 11). Vaccination and vector control as reported by the producers in this study were almost equally effective in controlling anaplasmosis. The number of clinical cases reported by respondents using low-level chlortetracycline puts it in third place relative to effectiveness in reducing incidence. Comparison of the returns to the anaplasmosis control methods reported by respondents was accom- plished by calculating benefit/cost ratios and net ben- efits to each method when used in the two specified herd sizes in Area 3. Benefit/cost ratios are designed to estimate the dollars of benefits per dollar of total expenditure for each preventive method employed. The reduction in production costs and increase in output provided by each of the three control pro- grams were compared to no control by applying the incidence to anaplasmosis occurring under each con- trol program as reported by producers (Table 13). Low-level chlortetracycline and vector control had similar benefit/cost ratios of 4.02 and 3.84, re- spectively, in the 122—head herd size (Table 13). How- ever, the higher cost of vector control over feeding low-level chlortetracycline had less effect on the net benefit from each control method than on the bene- fit/cost ratio, which resulted in a $500 advantage to vector control in net benefits. This amounts to $6.80 more return per head in the 122—head herd when using vector control instead of low-level chlortet- racycline. Comparison of vaccination and low-level chlor- tetracycline in the 553-head herd indicated vaccina- tion had higher returns as measured by both bene- fit/cost ratio and net benefit. This advantage is largely due to the lower per head cost of vaccination as compared to low-level chlortetracycline. Vaccination and vector control could not be compared directly because no producers in Area 3 with herds of 300 head or less reported using vaccination and likewise none with herds more than 300 head reported using vector control. Data on the 553-head herd size in Area 2 showed a benefit/cost ratio for both vaccination and vector control of less than 1 and a net dollar loss to both programs (Alderink, 1982). The total loss due to ana- plasmosis in herds larger than 300 head in Area 2 was too small for a control method to show positive returns. Ranchers with the larger herds in Area 2 appeared to use vaccination as insurance against the risk of occasional years when the incidence of ana- plasmosis may be high due to increased vector activi- ty. The calculated returns to control programs using Area 3 data may be more applicable since more than 80 percent of the losses due to anaplasmosis in Texas occurred in Area 3. Benefits to each preventive measure other than the benefit of controlling anaplasmosis vary among TABLE 13. BENEFIT/COST RATIOS AND NET BENEFIT ASSOCIATED WITH THREE ANAPLASMOSIS PREVENTIVE METHODS IN BEEF HERDS OF 122 HEAD AND OF 553 HEAD IN AREA 3 WITH AN ANAPLASMOSIS PROBLEM, TEXAS, 1980 Reduction Returns of Increase in to Cost of Benefit/ Production Total Value Control Control Cost Net Control Method Costsa Product“ Method Method Ratio‘ Benefit“ $ ---- --$ ----- -- 122 Head Herd Vaccination“ - - - - - - Low-level chlortetracycline 951.09 461.22 1,412.31 351.36 4.02 1,060.95 Vector control 1,370.46 750.51 2,121.95 552.66 3.84 1,569.31 553 Head Herd Vaccination 2,499.88 1,237.11 3,736.99 956.69 3.91 2,780.30 Low-level chlortetracycline 2,321.07 1,125.38 3,446.45 1,592.64 2.16 1,853.81 Vector control’ “Production costs include losses due to death loss, weight loss, chronic cases, and the cost for veterinary service and labor used on the clinical cases. blncrease in Total Value Product 1 increase in feeder calves sold as result of reduced abortion rate and reduced replacement calves required to replenish losses due to death and culled poor doers. ‘Benefit/Cost Ratio = Returns to Control Method/Cost of Control Method. "Net Benefit = Returns to Control Method — Cost of Control Method. 5N0 producer with a herd size < 300 head (average 122 head) reported using vaccination as the principal anaplasmosis control method in Area 3. ‘No producer with a herd size > 300 head (average 553 head) reported using vector control as the principal anaplasmosis control method in Area 3. 14 the three methods. Vaccination has no external bene- fit in addition tothe benefit of reducing the incidence of anaplasmosis. Low-level chlortetracycline has very little external benefit, but vector control has value to producers other than for anaplasmosis control (by relieving cattle of pain, worry, and blood loss as- sociated with insect bites). Producer respondents with no anaplasmosis problem substantiated this as 54 producers said they used ectoparasite control mea- sures while only four volunteered the fact they fed low levels of chlortetracycline. By contrast, ranchers using one of these two programs with the goal of minimizing anaplasmosis losses were evenly divided; 24 used ectoparasite control and 24 fed a low level of chlortetracycline. The benefit/cost ratio of 3.84 for vector control would likely be substantially higher if the benefit of reduced worry, irritation, and blood loss was in- cluded with decreased incidence of anaplasmosis. CONCLUSIONS This study supports the observation that ana- plasmosis has a marked, adverse economic impact on producers with infected herds. Producers, veterinari- ans, and others closely allied with the beef cattle industry and acquainted with the disease, agree with this observation. Anaplasmosis is common over much of Texas, with certain areas having a greater problem. Other diseases may be more costly, but few command more attention. Symptoms and associated losses due to anaplasmosis border on the dramatic, quickly alerting producers, in contrast to insidious losses, which usually remain unnoticed. This ex- plains in part why most producers with first-hand experience with the disease institute control pro- grams. The following 11 statements briefly summarize the findings of this research. 1. Forty-two of the 254 counties in Texas sus- tained more than 80 percent of the anaplas- mosis losses in the state. 2. Texas producers experienced more than 15,000 clinical cases of anaplasmosis during 1980. 3. The overall incidence of anaplasmosis in Tex- as was 2.76 head per 1,000 head adult breed- ing cattle per incidence area. 4. Incidence within herds has a negative rela- tionship to herd size. 5. Each clinical case of anaplasmosis averaged direct costs to Texas producers of $425. 6. The components of the direct cost of anaplas- mosis are: death, weight loss, chronic cases, abortions, cost of treatment, and cost of pre- vention. 7. The total direct cost in Texas due to anaplas- mosis was $8.96 million in 1980. 8. The benefit/cost ratios at 1980 price levels for vaccination, vector control, and low-level chlortetracycline when used in areas of high incidence ranged from 3.8 to 4.0. The excep- tion was low-level chlortetracycline which, when used in herds of over 300 head, had a benefit/cost ratio of 2.2. 9. Vaccination reduced incidence more than or equal to the other control programs and was used predominantly by ranchers with larger herds. 10. Vector control afforded good protection from clinical cases whether horseflies or winter ticks were the vector. 11. Low-level chlortetracycline was used by more producers than any of the other control methods. ACKNOWLEDGMENTS Funding for this research and course of study leading to a master's degree in Agricultural Econom- ics for Fred I. Alderink, Veterinary Services, Animal and Plant Health Inspection Service, U.S. Depart- ment of Agriculture, was furnished by VS, APHIS, USDA. The research and graduate program was under the direction of Raymond A. Dietrich, As- sociate Professor, Texas Agricultural Experiment Sta- tion (Department of Agricultural Economics). Information contained in this report is based upon "Economic and Epidemiological Implications of Anaplasmosis in Texas Beef Cattle Herds,” master's thesis, by Fred]. Alderink, Department of Agricultur- al Economics, Texas A&M University, College Sta- tion, Texas, May 1982. 15 Mention of a trademark or a proprietary product does not constitute a guarantee or a warranty of the product by The Texas Agricultural Experiment Station and does not imply its approval to the exclusion of other products that also may be suitable. a All programs and information of The Texas Agricultural Experiment Station are available to everyone without regard to race, color, religion, sex, age, or national origin. 2.5M—1-83