Johne’s (pronounced “Yo-nees”) disease is a chronic, contagious bacterial disease that affects the small intestine of ruminants such as cattle, sheep, goats, deer, antelope and bison. All ruminants are susceptible to Johne’s disease.
Johne’s disease is caused by Mycobacterium paratuberculosis, a hardy bacterium that embeds itself in the wall of the lower part of the small intestine known as the ileum. As an immune response, infected tissues attempt to regenerate healthy tissue which leads to visible thickening of the intestines. This prevents nutrient absorption, resulting in weight loss. Late in the infection, antibody production by the animal can be found in serum of animals and is an indicator that clinical signs of disease and death from the infection will soon follow.