Scientific advisers have asked the Ministry of Agriculture, Fisheries and Food (Maff) to draw up plans for a large-scale test for "subclinical" BSE where the animals are infected but appear healthy.
The survey falls short of a much wider programme of BSE testing which some scientists have sought. They believe official figures showing the epidemic's decline - based on animals with clinical symptoms - cannot be trusted due to under-reporting by vets and farmers.
Professor John Pattison, chairman of the government's Spongiform Encephalopathy Committee (Seac), said Maff has agreed to do the study as soon as the experimental protocol can be agreed.
"The reason for the survey is not to address the question of under-reporting of BSE," he said. "We recommended that Maff should develop protocols for looking for non-clinical disease.
"There are two states an animal may be in if they have evidence of infection but are not sick.
"One, strictly speaking, is preclinical, where if you wait long enough they will eventually fall sick. The other is subclinical infection where an animal shows some signs but never gets sick. It is to really to look at this question that we suggested to draw up a protocol."
Professor John Collinge, a Seac member, said the Swiss are already surveying abattoirs for subclinical BSE and he has argued for a wider test of cattle to investigate the possible appearance of different strains of the infective agent.
"You could broaden this survey. You could conceivably argue that there are different strains of BSE. Different strains may behave in different ways," said Professor Collinge.
"We have to address at least the possibility of there being multiple strains of BSE.
"One way of doing that, which I suggested to Maff [18 months ago], is to take 1,000 BSE brains and look at them to see if they have different patterns [of infection]."
The abattoir survey of healthy cattle brains will involve using a new test developed by Professor Collinge which might distinguish subclinically infected cattle from non-infected animals. Although the test has shown to be successful under laboratory conditions, Maff scientists have been unable so far to get it to work on a larger scale.
"This is not about strain typing, but about seeing whether there is evidence of BSE as a subclinical level in cattle."Reuse content