OPA Scanning

OPA is a contagious lung cancer of sheep, caused by the Jaagsiekte Sheep Retrovirus (JSRV).
The virus infects the lung’s alveolar epithelial cells, causing them to grow uncontrollably and form tumours. After infection, sheep often remain healthy-looking for months or even years before developing signs. By then, lung damage is usually severe. 

OPA spreads mainly through respiratory secretions, meaning the virus is present in the droplets sheep exhale, especially when they cough, sneeze, or breathe heavily. In practical terms, this means the disease can spread more easily in situations where sheep are close together and sharing air—such as in sheds, pens, or around feed troughs. Housing sheep indoors or feeding them closely from the same trough increases the risk of transmission. In contrast, sheep kept on open hillsides with plenty of space and fresh air are less likely to pass the virus between them. There may also be a risk of spread through colostrum and milk, though this is less well understood. 

Early signs are subtle. Affected sheep often appear outwardly healthy while disease is quietly progressing.
When symptoms do appear, they include:

• Breathing difficulties
• Weight loss despite a good appetite
• Poor exercise tolerance

In advanced cases, clear fluid may drain from the nostrils when the animal’s back end is lifted.
However, this only occurs in around 50–60% of positive cases.

Because symptoms are non-specific, OPA cannot reliably be diagnosed based on clinical signs alone.

Currently, there is no reliable blood test for OPA.
Post-mortem examination remains the gold standard for a definitive diagnosis.
Ultrasound scanning allows us to detect tumours in live sheep and are useful tool to screen a whole flock. 

At Lurgan Vet, we offer thoracic ultrasound scanning as a proactive tool to manage OPA within flocks.

Our recommended approach:

✔️ Act Early, Not Late

✔️ Regular Flock Screening

✔️ Immediate Culling of Positive Cases

✔️ Strict Biosecurity

✔️ Buy stock from scanned flocks  

✔️ Don’t keep lambs from Positive Ewes

Ultrasound, when performed by a well trained vet, is currently the best available tool for detecting and managing OPA in live sheep. It’s not perfect but the benefits in reducing long-term losses are significant.

Ignoring iceberg diseases like OPA can lead to devastating flock losses that take years to recover from.
Early diagnosis, rapid removal of infected animals, and strict biosecurity measures give you the best chance to protect your flock's health, welfare, and profitability.

At Lurgan Sheep Vet, you can be confident your flock is in experienced hands. Ann is an experienced OPA scanner who is involved in the Scottish Government’s OPA control project, a national initiative aiming to raise awareness and improve early detection of OPA across Scotland. She has the experience, knowledge and enthusiasm to help you tackle OPA and other Iceberg Diseases.  

 Scottish Government launches initiative to raise awareness | The Scottish Farmer