The aim of this study was to investigate the risk factors for Mycobacterium avium subsp. paratuberculosis (MAP) seroprevalence in sheep in the Trás-os-Montes e Alto Douro region, Portugal. A structured questionnaire was used to collect information. The effects on seroprevalence of several variables such as: individual characteristics; farm management practices; farm characteristics; animal health; and available veterinary services were evaluated. This information was used in a multivariable logistic regression model to identify risk factors for MAP seropositivity. Univariable analysis was used to screen the variables used in the logistic regression model. Variables that showed p<0.15 were retained for the multivariable analysis. Fifteen variables were associated with seropositivity in univariable analysis. Multivariable logistic regression model identified a number of variables as risk factors: when the sheep were a pure local breed and/or a cross of a local breed (OR=2.02; 95% CI: 1.28, 3.18); a herd size of between 31-60 head (OR=2.14; 95% CI: 1.34, 3.41); culling during the Spring-Summer season (OR=1.69; 95% CI: 0.93, 3.08); the use of an anti-parasitic treatment such as Ivermectin as the only anti-parasitic medication(OR=5.60; 95% CI: 1.85, 16.99); use of Albendazole with other anti-parasitic treatment (OR=3.89; 95% CI: 1.71, 8.89); use of associations of Closantel and Mebendazol (OR=2.83; 95% CI: 1.13, 7.09). Contrastingly, a number of factors which appeared to offer protection against paratuberculosis came to light. These were: ensuring the winter housing period lasts for less than six months; not spreading manure in fields to be used for grazing; and preventing access to areas where manure is stored.

Considering the paucity of epidemiological reports in the region and the absence of any data concerning factors related to either the prevention or the spread of the disease, our results could make a useful contribution towards the prevention of ovine paratuberculosis in the area.