Distribution of Mycobacterium avium paratuberculosis in Minnesota Dairy Farms Using Bacterial Culture of Fecal Pools

Abstract

Paratuberculosis, or Johne's disease, is a chronic and progressive intestinal disease in ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). The usual route of infection is fecal-oral, with young cattle becoming infected by exposure to infected adults or their contaminated environment. The disease becomes manifest in adulthood and results in economic losses due to premature culling, reduced milk production and loss of body weight in cattle sold for slaughter. Johne's disease control programs have been developed in different countries and in several US states, with a goal to test and classify herds of cattle as infected or presumptively non-infected with maximum accuracy and least cost. Generally, these programs utilize recognized laboratory tests such as ELISA or direct microbiological individual fecal culture. However, these tests have several disadvantages, especially when applied in herds with subclinical disease or low prevalence. A pooled fecal culture method, which aggregates several cows' fecal samples to one culture unit, has been recently suggested as a good alternative strategy for lowering the procedure cost for herd screening programs for dairy cattle. The objectives of the current study were to: 1) describe the apparent fecal pool prevalence of MAP in known to be infected and non infected Minnesota dairy herds based on pooled fecal culture, 2) estimate the animal-level prevalence based on fecal pool results, 3) characterize the association between cow age and pool status and shedding level results, and 4) characterize the association between pooled culture results and serum ELISA results at the herd level.