Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


The research consisted of a literature review of the epidemiology of anaplasmosis and a descriptive epidemiological study of anaplasmosis in the Red River Plains and Southeast areas of Louisiana. The prevalence of anaplasmosis assessed by indirect fluorescent antibody (IFA) testing of 11,085 serum samples that had been obtained from cattle located in the study areas was 7.8%. Beef cattle appeared to show a higher Anaplasma antibody prevalence than dairy cattle, that is 11.2% to 3.8%, respectively. Among breeds, the Angus and Angus-cross animals seemed to show an increased susceptibility to infection. The prevalence of infection in free-roaming deer was determined by serologically testing 331 deer serum samples. Six, or 1.8%, of the deer serum samples were positive by the IFA test for Anaplasma antibodies. Incidence rates of clinical anaplasmosis in beef cows, bulls and dairy cows were determined by producer surveys to be 0.31, 0.50 and 0.21%, respectively. Peak incidence of cases reported by producers and veterinary practitioners occurred in July, August and September as 88% of 256 cases were seen during these three months. The recognized principal vectors of anaplasmosis in Louisiana are the Tabanidae which are most abundant from mid-May to near the end of July. Hence, the clinical cases occurred 4-12 weeks after the peak abundance of the tabanid vectors. The majority of the cases were 4-6 years of age and the outcome was death in close to 50% of the cases. The relationship of clinical anaplasmosis in herds with other disease morbidity, nutritional supplementation, vaccinations, external and internal parasite control, tetracycline supplementation, reproductive management and use of veterinary services could not be found statistically. Herd location of seropositive animals and clinical cases of anaplasmosis was related to Tabanidae abundant areas of bottomland hardwood vegetation. Death loss, value of cull loss, dairy milk production loss, veterinary service, treatment and prevention costs in beef cows, beef bulls and dairy cows were valued at close to $0.5 million for the study areas in 1983. This determination was achieved through extrapolation of the epidemiological and economic parameters computed from the survey results.