Farmers within the State must be extra vigilant when inspecting their sheep, as they may miss the symptoms of foot-and-mouth, a UK veterinary expert has warned.
Sheep, in the current crisis, "are not showing many symptoms, and the disease is often diagnosed too late," said Dr Philip Duffus, of Bristol Veterinary School.
In the UK, the crisis has spread further than originally thought, and is moving rapidly from sheep into cattle, according to the UK chief veterinary officer, Mr Jim Scudamore.
This spread to cattle, which has been notable in recent days, is caused by direct contact with infected sheep, says Dr Bob Ward, of the University of Liverpool's veterinary faculty. "I think a lot of cases are being carried by sheep movement; cattle become infected when sheep move on to a cattle farm." Veterinary experts say sheep and cattle are also extremely susceptible to the virus, more so than pigs.
But the virus replicates more rapidly in pigs, which shed 3,000 times more virus than sheep or cattle. The UK Ministry of Agriculture (MAFF) two weeks ago imposed a ban on animal movement but is allowing limited movement to abattoirs under strictly controlled conditions.
The illegal movement of animals in the UK poses the greatest risk of spreading the virus further, said Prof Mac Johnston, of the Royal Veterinary College, University of London.
MAFF is currently tracing all sheep movements from Longtown Market, Carlisle, Cumbria, held on February 15th and 22nd. They believe, however, "a substantial number of sales" may not have been noted in market records.
The speed of trading also contributes to the spread, noted Dr Ward.
Animals are often bought in a market in one area of the UK and quickly transported and resold at another location.
A suspect animal, therefore, comes into contact with several other susceptible animals.
This makes tracing the animals a difficult and lengthy task.