Livestock Welfare

Ovine Pulmonary Adenocarcinoma in Sheep

Understanding Jaagsiekte sheep retrovirus (JSRV) causing progressive lung cancer in sheep flocks.

Key Facts

Ovine pulmonary adenocarcinoma (OPA) is caused by Jaagsiekte sheep retrovirus (JSRV)
It causes slow-growing lung tumours that progressively replace functional lung tissue
The classic diagnostic sign is watery fluid pouring from the nose when the hindquarters are raised
There is no treatment — affected sheep progressively deteriorate until death
Prevalence in endemic flocks can be very high without active culling programmes

Welfare Considerations

OPA causes prolonged welfare impairment through progressive respiratory compromise. The tumour grows slowly over months before clinical signs appear. When fluid accumulation in the lungs becomes significant, affected sheep show exercise intolerance, laboured breathing, and rapid weight loss. The characteristic fluid draining from the nose when sheep are lifted by the hindquarters confirms massive pulmonary involvement.

By the time clinical signs are evident, the welfare burden is significant. Affected sheep cannot move without respiratory distress, lose body condition rapidly, and become severely debilitated. The disease is invariably fatal — progressive until respiratory failure or secondary complications cause death.

Control in endemic flocks requires surveillance for early clinical signs, prompt culling of affected animals, and biosecurity to prevent spread. There is no vaccine. Purchased sheep should be quarantined and observed before introducing to the main flock.

What You Can Do

Implement regular respiratory health monitoring in sheep flocks in endemic areas
Cull any sheep showing progressive respiratory signs and weight loss promptly
Use the wheelbarrow test (raising hindquarters) to check for nasal fluid in suspected cases
Quarantine purchased sheep and observe for OPA signs before mixing with the main flock
Work with your vet to develop a herd health plan for OPA surveillance