Which bacterium is responsible for causing Johne's disease in cattle?

Mycobacterium paratuberculosis is the bacterium responsible for causing Johne's disease in cattle. This disease is a chronic intestinal infection that significantly affects the gastrointestinal tract of ruminants, especially cattle. Mycobacterium paratuberculosis is a slow-growing bacterium that can lead to severe diarrhea, weight loss, and can ultimately affect the productivity and health of the affected animals.

The disease often starts with a long incubation period, during which the animal may appear healthy, making it challenging to identify and manage. The presence of this particular bacterium has been linked to the specific symptoms and pathology observed in Johne's disease, underscoring its critical role in the disease's development and progression.

By contrast, Bacillus species and Salmonella are associated with other types of infections and diseases in livestock but are not connected to Johne's disease. Mycobacterium avium refers to a different organism within the Mycobacterium genus and is primarily involved in infections in birds and other species rather than ruminants. Therefore, Mycobacterium paratuberculosis is specifically the causative agent of concern regarding Johne's disease in cattle.