Environmental Distribution of Mycobacterium avium paratuberculosis (MAP) on Michigan Dairy Farms

Johne's disease (JD) is an important infectious disease of cattle caused by Mycobacterium avium subspecies paratuberculosis (MAP). It is estimated that over 50% of US dairy herds are infected with MAP. Environmental contamination with MAP is considered the major reservoir of infection for susceptible cattle. While MAP does not multiply in the environment, it can persist for months in manure, lagoons, manure packs--areas that are found in abundance on most dairy farms--even in below-freezing temperatures. Very little information is published on distribution of MAP on dairy farms. The objectives of this study were to: 1) perform serial environmental culturing on six Michigan dairy herds, enrolled in a JD control program over several years; 2) characterize the distribution of MAP contamination on dairy farms; and 3) determine if and how that distribution changes as herd fecal culture prevalence changes.