LONDON, Dec 21 (AFP) - Britain's senior government medical officer warned Tuesday that the full scale of the fatal human brain condition linked to mad cow disease may not be known for years. The official, Liam Donaldson, said new research by British and U.S. scientists did not bring very positive results. He said that their findings had come "as close as you can get to proof" that bovine spongiform encephalopathy (BSE), or mad cow disease, could spread to humans in the form of Creutzfeldt-Jakob Disease (CJD).
The scientists concluded that the same infectious agent caused BSE and CJD; a conclusion dealing a huge blow to those who had hoped a "species barrier" could protect humans. Donaldson appeared to agree with their study, which was published in the U.S. journal Proceedings of the National Academy of Sciences. In their findings that were documented in that periodical, they warned that "a large section of the population" in Britain might be "at high risk."
Donaldson told BBC radio, "We are not going to know for several years whether the size of the epidemic will be a small one - in other words in the hundreds - or a very large one in the hundreds of thousands."
The problem is that because of CJD's long incubation period, it is hard to estimate how many people who ate infected beef may be affected. "It is very unfortunate, but we are just going to have to wait and see what eventually the size of the outcome is," Donaldson added.
The scientists from the University of California at San Francisco and Britain's National CJD Surveillance Unit, based in Edinburgh, Scotland, reached their conclusions after a series of tests on mice.
Britain has seen by far the biggest incidence of BSE and new-variant CJD - as the sister illness is called - of any country, and 48 people have died of the human disorder. Fears of links between CJD and BSE prompted the European Union to impose a worldwide embargo on British beef exports in 1996. It was only lifted on Aug. 1 this year.
Steven DeArmond, of the University of California, warned that "we are just seeing the early leading edge, and incubation times could be from five years to 20 years. "We just don't know and we just don't understand why only young individuals come down with the disease, that's also very bizarre," he added. "The behavior of this disease is very, very peculiar."
A marathon official inquiry in Britain into BSE closed Friday after nearly two years. Its chairman, Lord Phillips, also warned that the number of people who had already died from CJD could be "just the tip of the iceberg." His report, due out in March, is expected to criticize the government over its handling of the crisis.
Meanwhile, the top civil servant in the agriculture ministry at the height of the BSE crisis, Richard Packer, is leaving his job. He denied his departure had anything to do with the BSE inquiry.
Newswires
