Contamination of alpine pastures by Mycobacterium avium subsp. paratuberculosis: Evaluation of cattle and red deer contribution through environmental fecal samples

Paratuberculosis is a chronic enteritis of ruminants (Bovidae, Cervidae) caused by Mycobacterium avium subsp. paratuberculosis (MAP). The prevalence of shedding animals, together with fecal MAP loads, is critical to the biocontamination of the environment. Surveillance for paratuberculosis has been introduced within the frame of European Health Law (Regulation EU 2016/429) both in livestock and wild ruminants. Semi-extensive and extensive livestock production may determine exposure to MAP infection and intraspecies and interspecies transmission on pasture. In the present study MAP prevalence and viable shedding in red deer and cattle were assessed through environmental fecal sampling over two summer seasons in the Alps. A low but widespread percentage of MAP-positive feces in both species was observed, indicating a small proportion of MAP grazing shedders. Consequently, the risk for MAP exposure on alpine pastures seems to be low. The highest contamination was reported mainly in overlapping areas for both species. The present study supports the utility and reliability of environmental fecal sampling as a non-invasive sampling approach to assess paratuberculosis shedding in grazing animals.