Johne’s Disease and Detection in Beef Cattle
Michelle Arnold, DVM
Ohio Beef Cattle Letter
What is Johne’s Disease? Johne’s (pronounced Yo-knees) Disease is a chronic disease of profuse, watery diarrhea and weight loss or “wasting” in adult cattle (Figure 1) caused by the bacterium Mycobacterium avium subsp. paratuberculosis, commonly referred to as “MAP”. This is a slow, progressive disease that begins when calves (not adult cattle) are infected with the MAP bacteria, most often around the time of birth but infection can occur up to 6 months of age and very rarely after.