But some experts believe the findings do not present any new dangers for humans and believe current public health measures are adequate. Scientists from the Medical Research Council Prion Unit, based at St Mary's Hospital, west London, discovered proof of a so-called sub clinical form of BSE where animals could be infected but show no symptoms of the disease. They injected material from BSE-infected hamsters into mice. Mice have always been thought to have an effective barrier against the disease. Although the animals showed no signs of illness, the researchers found they had high levels of potentially lethal abnormal prions in their brains.
Prions are the infectious agents in the disease.
Professor Andrew Hill, of the Medical Research Council's Prion Unit, said the research showed it was necessary to re-examine the way species barriers are measured in the laboratory. He said it was important to repeat the research using different strains of prions. Hugh Pennington, professor of bacteriology at Aberdeen University, played down any new fears. He is reinforcing what we know already. Variant CJD, which first emerged in 1996, is now known to be BSE in a human guise.