Johne's disease (paratuberculosis), caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic progressive enteritis of ruminants causing significant and prolonged welfare compromise. It is widespread in UK cattle herds and causes substantial production losses alongside its welfare impact.
Disease Progression & Welfare
Johne's disease progresses through stages over years:
Silent infection: Animals infected as calves may carry MAP for years without clinical signs. During this period they shed bacteria and infect other animals.
Sub-clinical disease: Reduced production, reduced immune competence. Animals appear healthy but are compromised.
Clinical disease: Progressive weight loss despite maintained appetite, chronic profuse diarrhoea, and eventually "bottle jaw" (submandibular oedema from hypoproteinaemia). This stage causes significant suffering over weeks to months before death.
The welfare concern is substantial: once clinical signs appear, the animal is experiencing chronic malnutrition (due to protein-losing enteropathy), hunger, weakness, and diarrhoea-related discomfort. Clinical cases should be euthanised promptly on welfare grounds rather than managed until they die naturally.
Control Strategy
Johne's disease cannot be cured, but herd prevalence can be reduced over time through: