A new Scottish Government-funded initiative to help increase the level of awareness and understanding of ovine pulmonary adenocarcinoma (OPA) or Jaagsiekte and its devastating impact on sheep flocks, has been launched.
While scientists have been researching this viral disease since the mid-1990s, it remains one of the biggest threats to the UK sheep industry when there remains no cure or vaccine.
This extremely contagious disease is further complicated as not all infected animals go on to develop contagious lung tumours caused by the Jaagsiekte sheep retrovirus (JSRV). Furthermore, while individual flockmasters may think an individual animal has the disease because it struggles to keep up with the flock and displays rough breathing under pressure, the only accurate diagnosis for OPA is through a post mortem.
At present, OPA which is known to produce losses of 2-7% per year in infected flocks, can only be controlled through ultrasound scanning the lungs of all breeding animals in a flockonce or twice a year. However, even this method is not 100% accurate when it is impossible to scan the full area of the lung.
The actual scan has also been the subject of debate in recent years when flockmasters end up culling females with any sort of lung lesion such as scarring or abscesses on the lung which might not necessarily be OPA.
“There are so many things that can happen in the lungs of sheep which might not necessarily be OPA,” said Eleanor Legg, from Clyde Vet Group, Stirling, who is one of the 13 vets joining the OPA scanning elite training and research programme.
“Many people think sheep with a rough throat, laboured breathing or those which have fluid coming out of their nostrils are positive for jaagsiekte, but such symptoms are not 100% accurate when pneumonia/pleurisy can produce the same signs.”
The new project aims to improve and evidence the accuracy of on farm ultrasound screening for OPA. The team of vets enrolled, who cover all areas of Scotland, will be able to view all individual lung scans from the project and agree on an end result with expert advice provided by leading expert Phil Scott FRCVS.
Signing up for the project means that a number of the sheep showing scarring, abscesses or tumours in the lung will be humanely slaughtered and post mortemed to confirm whether or not the sheep had any OPA involvement.
“If you are not sure if you have OPA in your flock, scanning your cull ewes, especially the older, leaner ones, is the best way to find out” added Dr Legg.
Flockmasters who sign up for the project will get the cull value and carcass disposal costs of any animal that is to be post mortemed but they will have to pay for the actual scanning which is based on an hourly rate and vet visit. It is also worth noting that while the scanning procedure is not complicated or difficult, it is labour intensive when individual sheep have to be physically turned around by hand to enable the vet to scan each side of the lung.
“People’s perception of OPA is changing. Some breeders are actively trying to do something about the disease while others don’t want to talk about it and deny they have a problem.
“I have seen Jaagsiekte or OPA in all breeds and cross-breeds and while it is possible that we may never be able to eradicate it, regular scanning by a professional should help towards establishing an accreditation scheme because at present there are no ‘proven’ clean flocks to buy from.
The biggest challenge with OPA control is the detection of early lung lesions before the disease appears. However, large OPA lesions are likely to be the biggest risk of transmitting the disease to other sheep in the flock and removing these is showing a good reduction in the number of cases in flocks that have previously seen many losses to OPA. The causal virus is transmissible via the breath of an infected animal and therefore can spread during close contact at trough feeding and housing. Furthermore, while it has traditionally been a disease of older sheep, infected ewes can pass it on to their lambs which can develop signs of the disease at a faster rate.
For more information email eleanor.legg@clydevetgroup.co.uk
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