February 27, 2012

expert reaction to recent cases of Schmallenberg livestock virus

The emerging livestock disease caused by the Schmallenberg virus hit the headlines after infecting a substantial number of British farms and causing major birth defects in sheep and cattle.

Prof Malcolm Bennett, Professor of Veterinary Pathology at the University of Liverpool, specialising in zoonoses and emerging diseases, said:

“Schmallenberg virus is the latest emerging disease of animals to hit the headlines. The first outbreaks of what look like a new disease of lambs and calves were detected in Germany and the Netherlands in the late summer and autumn of last year, and by mid-November the causative virus had been discovered using novel genetic techniques at the Friedrich Loeffler Institute in Germany. This approach allowed the rapid development of diagnostic tests, which are already being used across Europe and recently enabled the detection of virus in southern England.

“The virus is very closely related to a group of viruses that cause similar disease in cattle and sheep, mainly in the Far East and some areas of the Middle East and Africa. These viruses are spread by biting insects, in particular midges. The distribution of affected farms along the south coast of England, and the fact that none of these farms have imported any sheep, suggest that the virus was probably introduced through midges blown across the Channel last autumn.

“Bluetongue was the last midge-transmitted virus to be introduced to the UK from mainland Europe, but in handling that we had the advantage of knowing more about the virus and being able to deploy a vaccine. In this case we are still learning about the virus and, because it is so new, it will be some time before a vaccine can be developed. And, of course, controlling the movement of midges is very difficult.

“Other viruses in the group do not infect people, so Schmallenberg virus is unlikely to be a direct risk to public health. However, the economic and social effects of the disease for farmers whose animals are infected are still to be seen. The main effect in sheep is on unborn lambs, so only now, as we enter the peak period for lambing, are we beginning to see the extent and severity of the disease. Reports so far suggest that on affected farms between 10% and 50% of lambs are lost to the infection, and this could easily ruin an industry that has only just begun to recover after years of economic struggle. Because of the difference in the lengths of pregnancy between sheep and cattle, it will be another three to four months before we know what effect it might have on the cattle industry.”

The SMC also held a background briefing on the Schmallenberg virus on Thursday 1 March which can be viewed in the ‘Press Briefings’ section.