SCHMALLENBERG virus is the provisional name that has been given to the cause of a new disease that was first identified in the town of Schmallenberg in Germany, although the largest number of cases have now been seen in Holland, with more in Belgium and recently at a number of premises in the South East of England.
The disease, which has affected cattle, sheep, goats and may possibly affect camelids, is caused by an Orthobunya virus which is most likely to be spread by biting insects, mainly midges, although direct transmission cannot be ruled out at this stage.
It appears that midges pick up the virus very easily when biting, much more though than Bluetongue virus. Symptoms in adult cattle are of fever, reduced milk yield, loss of appetite and possible diarrhoea. In adult sheep and goats the disease is thought to be that the infection passes virtually unnoticed. The major problem is when animals are affected when pregnant, leading to the birth of deformed offspring and abortions.
At present it is thought that infection in the first third of pregnancy is likely to lead to severe brain damage such as hydrocephalus, under-development and abortion.
Infection in the middle third of pregnancy leads to limb deformities and in the final third 'dummy' offspring are produced which show inco-ordination, inability to suck and sometimes fits.
Up to 50% of animals within a group have been affected, leading to large losses. It is thought that in the first year of infection this could be devastating, but as the flock/herd immunity increases, the losses should decrease to a low level especially affecting first-time breeders. But this is dependent on the length of immunity stimulated by infection. Production of a vaccine is possible, but it is likely to take at least two years before it gets to the market.
Tests are limited with blood serology not available at the moment, but the presence of the virus can be detected. It is hoped that now that the virus has been properly isolated that a full range of tests will be available soon. Although the condition is not notifiable in the UK it would be wise to submit any births with congenital defect to the local AHVLA or SAC laboratory. Updated information on the disease and its spread are available on the Defra website.
There is no evidence that this virus can affect humans, but vets and farmers are advised to take routine hygienic precautions when handling potentially infected animals or carcases. Pregnant women should avoid contact with sheep and goats at lambing/kidding time for other reasons, but also for this condition, just in case.
Iain Carrington of Intake Vets in Hexham
