EPIZOOTOLOGICAL STUDIES AND DIAGNOSTIC APPROACHES TOWARDS CATTLE BRUCELLOSIS IN THE SMALLHOLDER DAIRY SECTOR OF ZIMBABWE
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A cross-sectional study was conducted to study the epizootology and diagnostic approaches of cattle brucellosis in six smallholder cattle farming areas of Zimbabwe. Specifically, the seroprevalence and risk factors for brucellosis were investigated. Serological diagnostic tests were evaluated and bacteriological investigations of herds and characterisation of Brucella spp. were carried out. The overall mean individual animal and herd-level seroprevalences were 5.6% (95% CI: 4.4%, 6.8%) (81/1440) and 25.0% (95% CI: 18.1%, 31.9%), (52/203) respectively. The seroprevalence differed significantly (P<0.05) among the study areas. Young animals (2-4 years) were found to be 5 times (OR=5.0, 95% CI: 1.4, 16.7) more likely to be positive compared to old animals (>7 years). Animals in the age group 5.5-7 years were found to be approximately 5 times (OR=4.9, 95% CI: 2.0, 11.6) more likely to have aborted compared to those of the age group 2-4 years, but the risk subsequently decreased with increasing age. Keeping mixed cattle breeds was associated with increased risk of brucellosis (OR= 8.5; 95% CI: 2.7, 26.5). Seropositivity (OR = 3.0, 95% CI: 1.4, 6.6) and mixed breed herds (OR = 2.3, 95% CI: 1.1, 4.9) were respectively found to be associated with increased risk of abortions. The kappa statistic test indicated good agreement among the c-ELISA, RBT and the FPA. The FPA had a higher specificity compared to RBT. The biochemical profiles of the B. abortus biovar 1 (11 isolates) and biovar 2 (2 isolates) typed in this study were typical of those of the genus. In conclusion, brucellosis was present in all study areas. The age of cattle and the mixing cattle breeds are important risk factors for brucellosis. The FPA could be used as a confirmatory test for bovine especially in the field. It is likely that B. abortus biovar 1 is the predominant cause of brucellosis in smallholder cattle. Further tests are required to study molecular biology and the epizootology of B. abortus.