Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's disease or paratuberculosis, a gastro intestinal inflammatory condition in ruminants and other animals, which is similar to Crohn's disease (CD) that occurs in man. The role of MAP in the causation of CD has been under intense investigation in the last few decades. This review summarizes the status of MAP in animals and the food chain and its association with CD in man.