OPA is a classic ‘iceberg’ disease farmers warned

With its ability to establish itself without sheep producers picking up on the level of infection in their flocks, ovine pulmonary adenocarcinoma (OPA) has been labelled as an “iceberg” disease.

This week, NFU Scotland and Livestock Health Scotland have combined to warn sheep farmers of the rising incidence of this fatal and infectious lung condition in flocks.

OPA, which has been recognised as a cause of sheep losses for generations of flock managers, is normally picked up in the later stages of infection by the accumulation of fluid within the affected animal’s lungs.

In recent years, surveys at sheep abattoirs and of fallen stock have demonstrated the reach and severity OFOPA. Accordingtolivestock Health Scotland, the disease is now being diagnosed in all regions of Scotland and is probably impacting on all breeds.

In the absence of an accurate laboratory test for the disease, lung scanning as a diagnostic tool has been developed at the animal diseases institute at Moredun. This test can identify tumours at an early stage.

Through combining the resources of experts from Moredun, SAC and sheep veterinarians, Livestock Health Scotland and NFU Scotland, a brief guide to OPA lung scanning has been produced so that sheep keepers can discuss a strategy to cope with the disease with their vets.

Livestock Health Scotland chairman Nigel Miller, a former NFUS president who is himself a qualified vet, said: “Like other iceberg diseases, OPA can establish unseen within a flock until infection rates rise and start to erode performance and trigger increased mortality.

“With no specific laboratory screening available, control is a real challenge and intervention is crucial attwolevels.inopa-affected flocks, action is needed to reduce infection rates, and in those flocks unaffected by OPA, you must seek to maintain disease freedom.

“The introduction of ultrasound lung scanning provides a much-needed diagnostic tool. Through the identification of early lung lesions, scanning can pinpoint risk animals before clinical disease is apparent. Lung scanning has a role in a test and cull programme in OPA affected flocks but may also be used to screen purchased breeding stock to reduce the risk of introducing disease into clear flocks.”

He warned that lung scanning could not demonstrate freedom from the disease but it could be a key part of disease risk management and control.

NFU Scotland’s animal health policy manager Penny Middleton added: “OPA has been cropping up more and more as a priority disease which producers are very concerned about. The focus has mostly been from flock owners concerned about buying in the disease, knowing that control can be difficult.

“Industry needs to start asking for this service and encouraging vets to undergo the training to be able to offer this service more widely.”