Risk factors of brucellosis (re-)incidence in sheep and goat flocks in an endemic area of Portugal.

This study aimed to determinate the main risk factors of brucellosis recurrence or highest animal incidence in flocks, under pastoralism, in an endemic area of Northeast Portugal. An epidemiological survey was performed on 25 recurrent (n = 18) or highest seropositive (n = 7) sheep and mixed goat flocks and 19 historical (≥ 10 years) brucellosis-free flock, between 2014 and 2017, within the same epidemiological area presenting an average annual incidence around 6%. According to the multivariable logistic model (P < 0.001), the lack of neighboring brucellosis-free flocks (odds ratio OR = 7.79; CI % 1.49-65.06), the occurrence of more than 50% of lambing or kidding in common paths and pastures (OR = 24.17; CI % 3.0-606.54), and the animal replacement with Rev.1 non-vaccinated young animals (OR = 18.47; CI % 2.54-408.21) were the causes that influence the recurrence and highest animal incidence in flocks. In extensive production systems, the confinement of the peri-parturient and the small ruminant replacement with Rev.1 vaccinated young females seems to play a major role on brucellosis control and eradication.