Paratuberculosis (Johne’s disease) is a chronic enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Identification of the agent: The diagnosis of paratuberculosis

Diagnosis of paratuberculosis is made on clinical grounds confirmed by the demonstration of MAP in the faeces by microscopy, culture, or by the use of DNA probes and the polymerase chain reaction. Diagnosis is made at necropsy by the finding of the pathognomonic lesions of the disease in the intestines, either grossly with the demonstration of typical acid-fast organisms in impression smears of the lesions or histologically, and by isolation of MAP in culture.