Farmers' worst fears were confirmed today as Britain's top vets said the bluetongue virus had officially become a full-blown outbreak.A control zone was immediately put in place at all locations within 150km of the confirmed cases in Suffolk.

Farmers' worst fears were confirmed today as Britain's top vets said the bluetongue virus had officially become a full-blown outbreak.

A control zone was immediately put in place at all locations within 150km of the confirmed cases in Suffolk. The zone takes in all of Norfolk, Suffolk and Essex.

The jump from isolated cases to an outbreak came as deputy chief vet Fred Landeg announced that a number of animals had been found to have been carrying bluetongue for longer than 30 days.

Mr Landeg said he thought the country would see “significant numbers” of new cases in October and November.

The news means bluetongue, which is spread by midges, is not only being carried by insects that have blown across the English Channel from northern Europe, where thousands of animals have been culled.

Instead, Mr Landeg confirmed that bluetongue was spreading among native midges and livestock.

He also said there was no effective vaccine available for this strain of bluetongue.

Mr Landeg said the virus was “circulating”, but would not say how many cases had been identified, or how many farms were now affected.

The first two cases of the disease in Britain were confirmed at a rare breeds farm at Baylham, near Ipswich. A third case was found at a dairy farm at Lound, near Lowestoft.

Two more have since been confirmed, including one at a farm at Burstall, near Ipswich.

Mr Landeg said there would be “no cull of affected animals”, as the disease was spread by infected midges, not through transfer from animal to animal.

He said if any animal was “suffering” as a result of bluetongue, it was the “responsibility of the keeper” to decide whether to cull it.