Sheep Ovine Pulmonary Adenocarcinoma: Welfare and Control

Ovine pulmonary adenocarcinoma (OPA) is a contagious viral lung cancer in sheep that is always fatal. Biosecurity and early culling are the only welfare-protective responses.

Key Facts

OPA is caused by Jaagsiekte sheep retrovirus (JSRV) — a contagious retrovirus spread through respiratory secretions
It causes progressive lung tumor growth leading to respiratory failure over months to years
The "wheelbarrow test" (tipping the nose down causes fluid to pour from the nostrils) indicates advanced disease
There is no treatment and no vaccine — disease is invariably fatal
OPA is present in most sheep-farming countries including the UK, USA, South Africa, and Australia
Subclinically infected sheep spread virus for months before showing clinical signs

Welfare Considerations

OPA causes progressive respiratory failure — affected sheep experience increasing breathlessness, reduced exercise tolerance, and ultimately profound respiratory distress at the terminal stage. The prolonged course of disease means animals suffer for an extended period if not identified and culled promptly. Since there is no treatment, welfare management focuses on early identification using respiratory function assessment and the wheelbarrow test, followed by prompt humane euthanasia of affected animals. Biosecurity to prevent introduction of infected animals is the only way to protect a clean flock.

What You Can Do

Test all incoming sheep with the wheelbarrow test before introduction to the flock
Maintain strict biosecurity — OPA introduction is effectively irreversible in most systems
Monitor flock for respiratory signs and cull suspected OPA cases promptly to prevent suffering and spread
Work with your vet to establish a flock OPA management protocol appropriate for your farm context