Abstract:
Reproductive disorders have negative impact on performance in cattle worldwide. Studies on infections causing reproductive disorders
in Tanzania are few and fragmented, which complicates targeted disease prevention. To investigate the prevalence of selected infections and their
associations with reproductive disorders and risk factors in cattle under different management systems, a cross-sectional study was conducted in
two bordering regions in the southern highlands in Tanzania. Herd and individual animal level data were collected by direct observation and a semistructured
questionnaire interview of the farmer. Sera from 658 cattle from 202 herds were analyzed using a commercial ELISA kits for antibodies
to Bovine Viral Diarrhea Virus (BVDV), Brucella spp. and Neospora caninum. The logistic regression model identified herd size (odds ratio (OR):
14.5), location (OR: 23.1) and management system (grazing strategy) (OR: 22.7) as risk factors for Brucella spp. The same risk factors were also
identified for BVDV herd size (OR: 2.8), location (OR: 12.7) and management system (OR: 2.9). History of abortion was associated with seropositivity
for Brucella spp. (OR: 4.6). No risk factors, including location and presence of dogs, nor any association with reproductive disorders were identified
for N. caninum. In one region the herd level sero-prevalence was 66.7% for BVDV and 36.1% for Brucella spp., while in the other it was 6.5% for
BVDV and 0.6% for Brucella spp. In total, BVDV specific antibodies were found in 15.2% of the animals in 17.9% of the herds, and Brucella spp.
specific antibodies were detected in 5.4% of the animals in 7.4% of the herds. Anti- N. caninum antibodies were found in 4.5% of animals in 8.4% of
the herds. In conclusion, prevalence and impact of BVDV and Brucella spp. differed significantly between geographically closely related areas, most
probably due to differences in management system that affects the potential for survival of the agents in the population. This shows that all control
measures must be based on accurate epidemiological knowledge of the occurrence of the infection. Low-prevalence areas are highly susceptible for
introduction of infection, while in the high-prevalence areas control measures must be implemented to reduce the impact and the risk of transferring
Brucella spp. from livestock to humans.
