Prevalence and herd-level risk factors of bovine tuberculosis in the State of Santa Catarina

Abstract

With the aim of supporting the strategic planning of the National Program for Control and Eradication of Brucellosis and Tuberculosis, different Brazilian states have been conducting cross-sectional studies, coordinated by the Ministry of Agriculture, Livestock, and Supply and with scientific support from the University of São Paulo and the University of Brasilia. In Santa Catarina, the State Animal Health Agency (CIDASC) conducted a study on bovine tuberculosis (TB) prevalence and assessment of risk factors in 2012. The state was divided into five regions and, in each region, independent sampling was performed in two steps: (i) cattle herds with reproductive activity were randomly selected; and (ii) in each herd, a sample of females aged 24 months or older underwent the intradermal comparative tuberculin test. A questionnaire was used to collect data on production characteristics and management practices that could be associated with the tuberculosis infection. Herd prevalence of bovine TB was 0.50% (95% confidence interval [CI]: 0.074–0.93%) while the prevalence of TB in adult females was 0.06% (95% CI: 0–0.12%). No significant difference in the prevalence of infected herds and of positive females was observed among the five regions. The logistic regression model revealed that herds with 19 or more females showed an odds ratio (OR) of 7.68 (95% CI: 1.22–48.39) compared to smaller herds, while dairy herds presented an OR of 10.43 (95% CI: 2.00–54.25) relative to beef or dual-purpose herds. The results suggest that dairy herds, in which animals are kept in partial or total confinement, and larger herds, which tend to acquire animals more often, are at a higher risk of bovine TB. Given the low prevalence and the type of higher-risk properties, a bovine TB surveillance system should be targeted at the state’s dairy basins, particularly the western region that accounts for the major industries and more intensive dairy farms.