Johne's disease (paratuberculosis) causes progressive wasting in sheep. Control through testing and biosecurity is welfare-protective at both individual and flock levels.
Johne's disease causes prolonged welfare deterioration in affected sheep. The clinical phase — typically beginning in 2-5 year old sheep — involves chronic, watery diarrhoea and progressive protein loss causing bottle jaw (submandibular oedema), weight loss despite maintained appetite, and eventual emaciation. Affected sheep may survive for months in this deteriorating welfare state, becoming increasingly thin and weak while continuing to shed MAP organisms and contaminate pasture.
Early welfare-protecting decisions — culling test-positive animals before severe clinical signs develop — are both more humane for affected individuals and more effective for flock control than waiting for clinical disease to dictate culling decisions. Regular ELISA testing at sale and market events enables identification of shedding animals before they enter naive flocks.