British scientists warned yesterday there was the risk of a major rise in the human death toll from vCJD if sheep had become infected by BSE. However, they admitted the estimate was beset by many unknowns.
The estimate, by epidemiologists from the Imperial College of Science, Technology and Medicine in London, was published online by the weekly British science journal Nature.
Scientists are trying to find out whether BSE has been transmitted to sheep, possibly via feed supplements - the suspected way in which cattle became infected.
The Imperial College team devised a computer model to predict how many fatalities might occur among people who ate both infected beef and sheepmeat.
Between 2001 and 2080, the number of deaths in Britain from eating BSE-contaminated beef would generally be from 50 to 50,000, with a worst-case peak of 100,000, according to their estimate.
If sheep are also assumed to be infected, the overall toll in some scenarios would remain unchanged. But in many other scenarios, it would be 20 to 50 per cent higher.
Under the worst-case scenario, 150,000 would die over 80 years, through eating infected sheepmeat and beef.
The team stressed there are many unknowns, notably about the incubation period of the agent, which, even assuming that it exists, could take an unknown number of years before causing clinical symptoms in humans.