Factors associated with seroprevalence to Mycobacterium paratuberculosis in small-ruminant farms in the Madrid region (Spain).

A cross-sectional study was conducted in a population of small ruminants in the Madrid region (Spain) to determine the Mycobacterium paratuberculosis seroprevalence and to identify farm factors possibly associated with paratuberculosis (PTB). Farming-management information and sera were collected from 60 sheep or goat flocks. The relationship between seropositivity and the variables in the questionnaire was assessed by unconditional logistic regression, followed by random-effects logistic regression analysis to adjust for overdispersion between herds. The seroprevalence to M. paratuberculosis was 11.7% (64 out of 546) using agar-gel immunodiffusion assay (AGID). According to the sensitivity and specificity of the AGID test the true prevalence could be as high as 44%. A herd size of between 200-400 head and the presence of foreign breeds and their crosses were significantly associated with seropositivity (OR = 4.05 and OR = 4.32, respectively). A higher replacement rate was also associated with seroprevalence to M. paratuberculosis (24.2% in positive herds vs. 18.1% in negative). All these three factors were related to more intensive management in the surveyed area. In contrast, membership of a professional livestock association appeared to be a protective factor against PTB (OR = 0.28). No variables related to veterinary assistance were associated with seroprevalence, probably reflecting the current lack of interest in PTB on the part of the animal-health administration and veterinary services in Spain.