Johne's Disease

Johne’s disease is an untreatable, chronic, progressive bacterial intestinal disease of cattle caused by Mycobacterium avium subspecies paratuberculosis or MAP. A study conducted in 2009 by Good et al. estimated that the prevalence of Johne’s disease in Ireland is 20% in dairy herds and 6% in beef herds. The disease is characterised by scour, reduced production – lower milk yields and feed conversion, weight loss leading to emaciation, soft swelling of the jaw or brisket (bottle jaw), and eventually death.

An infected animal can shed MAP bacteria over a long period and infect others before developing clinical signs of the disease. Calves and young animals are particularly susceptible to infection so it is therefore important to identify infectious animals and remove them from the herd as part of a control strategy.