Schmallenberg virus, a new livestock disease discovered last year which causes birth deformities in sheep and cattle, has re-emerged this summer and could spread all across Britain in the weeks to come, scientists warned today.
The disease, which has no effects on humans, is carried by biting midges and is believed to have arrived in Britain last autumn when infected insects were blown across the Channel from the Netherlands and Germany, where it was first identified.
It is closely related to the much more serious blue tongue virus, which is also midge-borne and arrived in Britain in 2007, but was wiped out by an emergency campaign of vaccination the following year.
While blue tongue can have a very high mortality rate, Schmallenberg virus hardly affects adult animals, but if sheep and cattle are pregnant when they catch it their foetuses can be seriously damaged, resulting in abortions or birth abnormalities.
A total of 276 farms in Britain were affected last autumn and winter, mainly in the south and the midlands.
It was hoped that the disease might naturally disappear with the winter die-off of midges, but today senior veterinary scientists announced that that the pathogen had overwintered and new infections of cattle had been found, in the middle of the summer midge season – meaning that the insects could now spread it to anywhere in Britain.
“Animals that had originally been negative for antibodies against the virus became positive between March and June 2012, indicating that the virus has survived the winter and is circulating here during the current midge season,” said Professor Peter Mertens of the Institute for Animal Health.
“We had hoped that it might simply burn itself out and fail to make a reappearance this year, but this has not been the case.”
He added: “As we have found infected animals in the few places where we have looked, so we would expect disease has also occurred elsewhere. I would expect the outbreak to spread, really from now, and I see no reason why it shouldn’t spread to cover most of the country.”
A Schmallenberg vaccine is being developed, but it is unlikely that it will be ready for use before next year. There is little that farmers can do to defend themselves, other than bring all their livestock indoors, or try to alter mating times. It is not a notifiable disease, which means there are no major Government measures such as movement restrictions swinging into action.
Although stressing that it much less serious than blue tongue, leading veterinary scientists admit that the outbreak can be upsetting for farmers. On average fewer than five per cent of lambs or calves are born deformed, but on some farms the total has been very much higher. “So far we have seen a relatively limited impact from the disease on English farms and those in the rest of Europe, but we understand that it can be distressing for individual famers,” said the Government’s Chief Veterinary Officer, Nigel Gibbens.