Chronic inflammation of the mucosa of the ileocecal valve and adjacent tissues of the gastrointestinal tract of cattle, sheep, goats, and captive wild ruminants, caused by the bacterium Mycobacterium paratuberculosis. Transmission of M. paratuberculosis is primarily by ingestion of feces from animals shedding the organism. The incubation period varies from 2 to 3 years or more. Diseased animals in advanced stages have intermittent or persistent diarrhea without fever and often become emaciated.

Johne's disease is diagnosed by serologic tests and mycobacteriologic examinations conducted on feces or tissues collected by biopsy or at necropsy. To confirm a diagnosis of Johne's disease, it is necessary to isolate and identify the etiologic agent.

Therapeutic drugs are not available for routine treatment of animals. A killed whole-cell vaccine is available for use in calves 1–35 days of age. Live attenuated strains of M. paratuberculosis have been used for vaccinating cattle in a few countries, but are not approved for use in the United States or Canada. Mycobacterium paratuberculosis has not been shown to cause disease in humans; however, a M. paratuberculosis-like organism has been isolated from a few individuals with Crohn's disease.Mycobacterial diseases