Bluetongue: more lethal than foot and mouth, but not contagious

What farmers fear most is that bluetongue virus could become established in Britain, ravaging herds and bringing economic catastrophe. Unlike foot-and-mouth, it cannot be eradicated by culling and a confirmed outbreak would add to the series of hammer blows which rural Britain has suffered recently.

This strain of the virus, called serotype 8, kills up to 70 per cent of herds, and has infected nearly 3,000 animals in northern Europe since July. Although it is more lethal than foot-and-mouth, it is not contagious. It spreads more slowly and is transmitted by midges of the Culicoides species which can fly up to 200 kilometres (125 miles) a day with wind assistance.

But there is no reliable way of containing it. Culling is useless against a disease spread by insects, and an effective vaccination is still at least a year off.

The Department of Environment, Food and Rural Affairs warned last month of the risk of the disease spreading across the Channel and urged farmers to be vigilant.

The sheep and cattle affected have developed a fever, swelling of the head and neck, ulcers in their mouth and on their nose and eyelids, lameness and breathing difficulties. Once an outbreak is confirmed, all movements of livestock would be banned in a zone 20 kilometres around the infected farm. A protection zone of at least 100 kilometres would also be set up, with no animals allowed to cross in or out of it.

The only control measures available to farmers would be to spray insect breeding sites such as manure heaps with insecticide and douse livestock with insect repellent. But these measures would at best reduce the level of infection.

David Catlow, president of the British Veterinary Association, said yesterday: "At the moment [we face] a frightening prospect of a serious disease but have no means of protecting animals from it."