Britain is on the alert for a midge-borne disease that can be fatal to sheep and cattle.

The bluetongue virus, which hit Northern Europe for the first time last summer as a result of climate change, has survived winter on the Continent and an outbreak was reported last week in Lower Saxony. Cattle and sheep in a 100-mile radius of the German outbreak are being locked inside.

The infection caused by the Culicoides midge does not affect humans, but scientists say it is a wake-up call about the effects of climate change. There is concern that tick-borne diseases such as Lyme disease could infect people more easily as infected midges become more widespread.

Last year there was surprise among scientists that bluetongue had spread from North Africa and the Mediterranean to the Netherlands, Belgium, Germany, Luxembourg and France, infecting 2,000 farms. Now Debby Reynolds, the Government’s chief vet, says that she is planning for when, and not if, the virus enters Britain. The virus can travel with midges on the wind up to 200 miles.

Most at risk are sheep and cattle farmed in Kent, Essex and East Anglia — places closest to the Continent.

One case of the disease, and animals will be quarantined. A hot, dry spell could produce a shortage of feed, and there could be the overcrowding and suffering among livestock seen in the 2001 foot-and-mouth disease outbreak. The midges can also infect deer and goats.

Meat from infected animals that survive is safe to eat.

John Gloster, a Met Office researcher seconded to the Institute of Animal Health, has identified days in each month when Britain is most at risk of infected midges arriving on the wind. If the virus becomes established in one region, “clean” midges might become infected and spread it to other areas. The biggest threat is thought to be next month, but news of the outbreak in Germany means the disease could be imminent.

In sheep the disease is known to wipe out 70 per cent of the herd, but experts believe the strain on the Continent may be less virulent, and suggest a mortality rate of 30 per cent in a sheep flock and as low as 10 per cent in cattle. The virus may be without symptoms in cattle, goats and deer.

Dr Reynolds said: “It is vital to take the situation seriously — it poses big challenges we have not faced before. Everything I see makes me think this virus is near enough to the UK to be a real risk this summer. Infected midges could blow in our direction and we can do nothing to stop it happening.”

She has ruled out mass culls or compensation — a matter under dispute with farmers.

All imported sheep and cattle are already being tested.

In sheep the symptoms of bluetongue are similar to foot-and-mouth disease. There is no known treatment for bluetongue, though scientists are testing insecticide sprays to see if animals can be protected.

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