How is Mycobacterium paratuberculosis Spread?
Transmission of M. paratuberculosis to susceptible animals is primarily by oral ingestion of feed and water contaminated by infected feces (1, 2, 5, 11). Fecal shedding of M. paratuberculosis from an animal with clinical disease can be as high as 5 trillion organisms/day. These animals are the primary source of environmental contamination on the farm (15). Infected runoff can contaminate a property and continually grazed pasture will remain infected indefinitely (1). Acidic conditions in the soil are associated with an increased prevalence of the disease, while alkaline soil caused the disease to be more self-limiting (5, 16). Mycobacterium paratuberculosis has also been detected in the colostrum and milk of infected cattle (17). Its presence in milk appears to be related to the level of fecal shedding, up to nearly 35% of animals with advanced clinical disease have M. paratuberculosis in their milk (18). In spite of this, some researchers suggest that infected milk is not an important
