The best hope for farmers facing the new threat of bluetongue in livestock is a cold winter which would stop the disease, experts said yesterday.

Professor Philip Mellor of the Institute of Animal Health at Pirbright, where bluetongue samples are currently being tested, said the virus replicated in the body of insects at temperatures above 15C, so a cold winter could stamp out a possible outbreak.

"What we really need is a cold, wet autumn and winter with weather from the Atlantic," he said. "If we get a cold snap where it never gets above 10C for a month, the virus would not be able to replicate. And if the temperature gets really low, it will kill the insects."

But he warned it would take more than a few days of bad weather to eradicate the virus.

Deputy chief veterinary officer Fred Landeg also said farmers' best hope if bluetongue has established itself is a frosty winter, which would wipe out the midge population.

He said a vaccine for the disease is being developed, hopefully for next summer.