An update on the epidemiologic situation of bovine brucellosis in the state of Espirito Santo, Brazil

A cross-sectional study was carried out between January 2012 and May 2014 to estimate the prevalence of bovine brucellosis in the state of Espirito Santo, Brazil. This study was carried out 11 years after the implementation of the immunization program for heifers with a vaccine derived from the S19 strain of Brucella abortus. The state was divided into two regions. Three hundred farms from each region, with reproductive activity, were randomly chosen and included as primary sample units. A fixed number of cows were randomly selected and tested for antibodies against Brucella spp. A farm was considered to be infected when at least one female tested positive for Brucella spp. In the selected farms, an epidemiological questionnaire based survey, focused on herd traits as well as husbandry and sanitary practices, was conducted, to evaluate the factors associated with the risk of infection. The overall prevalence of infected herds was 9.3% (95% confidence interval, 95% CI = 7.1-11.8%), varying from 8.7% (95% CI = 5.7-12.6%) in region 2 to 9.7% (95% CI = 6.8-13.4%) in region 1. There was no significant difference in the prevalence between the regions. The apparent prevalence of Brucella spp. positive farms across the regions and the state was similar to the prevalence observed 11 years earlier. The prevalence of positive animals was 3.8% (95% CI = 0.9-10.1%), varying from 1.5% (95% CI = 0.82.4%) in region 1 to 7.9% (95% CI = 1.9-20.3%) in region 2, without a significant difference between the regions. There was no difference in the number of Brucella spp. positive animals after 11 years of the immunization program. The risk factors associated with brucellosis were (i) more than 10 cows per herd (OR = 5.0; 95% CI = 2.5-11.1) and (ii) equipment, feedstock, or personnel sharing (OR = 2.2; 95% CI = 1.1-4.2). The state of Espirito Santo should seek systematic vaccination coverage targeting more than 80% of the eligible heifers. An efficient animal health program, which educates the farmers to test replacement animals for brucellosis before introducing them to their herds, to avoid equipment, personnel or feedstock sharing with farms of unknown sanitary conditions, and to increase awareness of the importance of good sanitary procedures during artificial insemination, should be implemented.