THOUSANDS of rainbow trout have been destroyed in a bid to halt a rare virus threatening to devastate fish farms.

Government officials have slaughtered 19.5 tonnes of fish at an unidentified trout farm in North Yorkshire.

The Centre for Environment, Fisheries and Aqua- culture Science (CEFAS) is now carrying out tests on nearby farms.

So far, the killer virus, viral haemorrhagic septicaemia (VHS), has only been found on one farm in the River Ouse catchment area, but stock movement restrictions have been put on 33 fish farms.

Nick Read, chairman of the British Trout Association, said: "VHS is certainly a serious disease in rainbow trout.

"Until now, the controls existing to protect the UK have prevented it from arriving on the mainland.

"So this case has to be taken extremely seriously and all necessary steps have been taken, and will be taken, to eliminate the disease."

But with the CEFAS test results not due for another three weeks, many fish farmers fear financial problems.

Those farms where fish are killed due to VHS will not get any compensation.

A spokesman for Swinton Trout Farm, near Ripon, said: "It has a lot of comparisons to foot-and-mouth. They are coming round testing us all and if we have it, then they will slaughter our stock without compensation.

"We don't know what is going to happen and there is the potential for a lot of businesses to fold."

He added: "We have a lot of business restocking fish farms and we are not allowed to move the fish around, so effectively we are closed.

"We expect to move stock on, and there is the space problem of keeping the fish here until we can."

Yorkshire is seen as an important centre for trout farming within the UK.

The disease is common in Denmark and France, but the only other British outbreak was in 1994 on the Scottish island of Gigha.

The disease, which cannot be passed to humans, is highly infectious in fish, spreading through contact and faeces.

Although found in the wild, it is more common in fish farms due to the trout being close together.

A Department for Environment, Food and Rural Affairs spokesman said tests were carried out to determine how the disease reached Britain.

He said: "All fisheries on the River Ouse downstream from, or near, the affected farm are being tested to reduce the risk of VHS spreading.