Seroprevalence and risk factors associated with Brucella seropositivity in dairy and mixed cattle herds from Ecuador

An extensive cross-sectional study to determine the seroprevalence of and associated risk factors for Brucella infection was performed in dairy and mixed (dairy-beef) cattle herds in Ecuador. A total of 2666 serum samples from 386 farms were analyzed using Rose Bengal test and a blocking ELISA test. In addition, a questionnaire with 57 variables related to management, feeding, facilities, biosecurity, and animal health was filled in every cattle farm. A Generalized Estimating Equations model was used to determine the factors associated with Brucella seropositivity. The true prevalence of Brucella seropositivity in dairy and mixed cattle from Ecuador reached 17.0% (CI95% 15.6-18.4%). The herd prevalence was 45.1% (174/386) (CI95% 40.1-50.1%), and the within-herd prevalence ranged from 10 to 100% (mean 38.9%; Q1 14.3%, Q2 26.8%, Q3 52.5%). Seven factors were included in the GEE model for Brucella seropositivity: the nominal variables sex (OR 2.03; CI95% 1.32-3.13), herd type (dairy) (OR 1.79; CI95% 1.11-2.87), closed facilities in the farm (OR 1.80; CI95% 1.19-2.74), and ad libitum feeding (OR: 0.32; CI95%: 0.19-0.54), and the quantitative variables age (OR 1.005; CI95% 1.001-1.009), average slope in the farm (%) (OR 1.013; CI95% 1.002-1.024), and annual abortion rate (OR 1.016; CI95% 1.002-1.031). This study remarks the high spread of Brucella infection in cattle farms from Ecuador. In addition, it reports the risk factors associated to this infection in the predominant extensive system existent in this country.