Johne’s Disease: Cattle

Cause

The bacteria Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's disease. It is related to the bacteria that cause tuberculosis.

The bacteria initially reside in the last section of the small intestine – the ileum. Over time, often over several years, the number of bacteria grows and the animal’s body responds with inflammation. All this causes the intestinal wall to thicken until it is unable to absorb nutrients. As the disease progresses, the bacteria may also spread to other tissues, including lymph nodes, uterus, and mammary tissues. Bacteria are shed in manure, colostrum, and milk to become a source of new infections.

Although MAP does not replicate in the environment, it is hardy and has been shown to survive up to 9 months in manure pits, 11 months in soil, and 17 months in water.