PARATUBERCULOSIS (JOHNE'S DISEASE)

Causative Agent(s)

Mycobacterium avium subsp. paratuberculosis

Clinical Presentation and Epidemiology

Paratuberculosis in cattle is characterised by weight loss and diarrhoea in the late phases of infection, but infected animals can appear healthy for months to years. In cattle, diarrhoea may be constant or intermittent; in sheep, goats, and other ruminants, diarrhoea may not be seen. It typically does not contain blood, mucus, or epithelial debris and is passed without tenesmus. Throughout weeks or months, the diarrhoea becomes more severe, further weight loss occurs, coat colour may fade, and ventral and submandibular oedema may develop due to a protein-losing enteropathy.

Paratuberculosis is a listed disease by the OIE, meaning it is a priority disease for international trade. The infection has also been recognized in captive and free-ranging wild ruminants. Distribution is worldwide. Many countries have national control programs. The highest published prevalence is in dairy cattle, with 20%–90% of herds infected in most major dairy-producing countries.

Diagnostic Considerations

Samples include faecal and tissue.

PCR is the primary method currently used

There are many commercially available tests for paratuberculosis, which focused on detecting the organism in faeces or tissue (culture, PCR), or on detecting antibody to MAP antigens (ELISA).

Management and Treatment Prevention

Identify and cull or segregate infectious adult animals. No satisfactory treatment is known. Control requires good sanitation and management practices aimed at limiting the exposure of young animals to the organism.

Isoniazid at 20 mg/kg administered orally q24 h for the rest of the animal's life. This treatment is palliative rather than curative

Control

Control measure requires good sanitation and management practices aimed at limiting the exposure of young animals to the microorganism.