Ovine respiratory disease complex is a leading cause of morbidity and mortality in sheep, caused by a combination of infectious agents and management factors, and represents a significant and preventable welfare burden in global sheep flocks.
Respiratory disease in sheep causes both acute suffering — fever, laboured breathing, inability to eat — and, in the case of Maedi-Visna, a prolonged deteriorating course over months to years. The chronic nature of ovine pulmonary adenocarcinoma and Maedi-Visna means affected sheep may suffer for extended periods before death or culling. Prevention is far more effective than treatment for most forms of ovine respiratory disease. Housing design that maximises air flow, minimises stocking density, and separates age cohorts dramatically reduces pneumonia incidence. Eradication of Maedi-Visna through flock testing and removal of positive animals has been achieved in several European countries and is achievable where producer commitment and support exist.