A new animal disease which causes severe birth defects and miscarriages in livestock could spread across the whole of Britain this year, experts have warned.
There have been 276 cases of Schmallenberg virus, which first emerged last year in the Netherlands and Germany, in cattle and sheep on farms across southern and eastern England since early 2012.
Adult animals which were infected during their pregnancies last autumn by virus-carrying midges, thought to have blown across the Channel, gave birth to deformed or stillborn lambs and calves this spring.
Despite midges dying off during the winter months, tests since March on around 150 cattle and more than 1,000 sheep belonging to the Royal Veterinary College (RVC) showed a small number of animals which had previously tested negative for the disease have now tested positive.
Two of the RVC's small herd of alpacas have also tested positive for Schmallenberg. The results revealed the virus had survived the winter and was still circulating in the UK in the current midge season.
Professor Peter Mertens of the Institute of Animal Health said: "On the basis it spread last year very effectively, I see no reason why it couldn't spread to cover most of the country this year."
While the impact varies, with as many as 30% of young being born deformed or stillborn on some farms, the incidence rate is generally low - around 2% to 5% of flocks or herds giving birth to deformed offspring, chief vet Nigel Gibbens said.
He said: "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 farmers."
But the veterinary experts moved to quell fears of a repeat of bluetongue which spread to the UK from the Continent in 2007, and prompted an emergency response of widespread vaccination amid concerns that it could kill 25-30% of the country's sheep, around 8-10 million animals.
Prof Mertens said of Schmallenberg: "It's still serious, and particularly serious for individual farmers, but if bluetongue had really got hold of the UK, it would have been devastating. This is very important but it's on a different level."