Seroprevalence and Risk Factors Associated with Brucella Infection in Sheep Flocks in Ecuador

Brucellosis is an important infectious disease affecting livestock worldwide, causing reproductive losses in small ruminant production systems and representing a persistent challenge for animal health and public health under a One Health perspective. Despite its importance, epidemiological information on ovine brucellosis in Ecuador remains scarce. This cross-sectional study aimed to estimate the seroprevalence of Brucella spp. infection in sheep at both the individual and herd levels and to identify potential risk factors associated with infection. This study represents the largest epidemiological investigation conducted to date on ovine brucellosis in Ecuador, covering the main sheep-producing regions of the country (more than 95% of the national sheep population). Between 2024 and 2025, a total of 970 sheep from 385 farms were sampled. Serum samples were analyzed using a commercial ELISA assay, and epidemiological information was obtained through structured farm surveys. Statistical analyses included bivariate tests and a multivariable model using Generalized Estimating Equations (GEE). The overall individual seroprevalence was 5.1% (49/970), while herd-level prevalence reached 7.5% (29/385). Multivariable analysis identified abortion rate (OR = 1.045; 95% CI: 1.016–1.074) and isolation of sick animals (OR = 2.843; 95% CI: 1.150–7.027) as factors associated with seropositivity, whereas access to technical advisory services was identified as a protective factor. These findings provide essential epidemiological evidence to support surveillance programs and improve biosecurity and veterinary extension strategies in Ecuadorian sheep production systems.