Just as concerns were abating, research published Friday suggests that the human form of mad cow disease in Britain could be more widespread than thought.
Scientists have estimated that 3,800 people in Britain could be unwittingly carrying the prion protein responsible for variant Creutzfeldt-Jakob Disease (vCJD), a fatal brain-wasting condition.
“Our findings need to be interpreted with caution, but cannot be discounted,” said David Hilton, of Derriford Hospital in Plymouth, and lead author of the report published in The Journal of Pathology.
Hilton and scientists from the CJD Surveillance Unit in Edinburgh, Scotland, and Imperial College in London studied 12,674 stored appendix and tonsil samples removed during routine operations in the late 1990s from people in their 20s. Three showed evidence of prion protein accumulation associated with vCJD.
Based on their findings, they came up with the 3,800 figure.
“There is still much to learn about vCJD and the presence of the protein in these tissue samples does not necessarily mean that those affected will go on to develop vCJD,” Hilton added.
Further investigation needed
The scientists stressed that only one of the three positive samples showed a pattern of the prion accumulation similar to that seen in known vCJD cases. The other two were different so their significance is uncertain.
Sir Leszek Borysiewicz, of Imperial College in London, said the figures are not in the alarmist range but warrant further investigation to get to more accurate answers.
“They scream out at me that we still need better diagnostic tests,” he said in an interview.
“It is a relatively unusual condition but every case is one more than you would want,” he added.
Since vCJD was first detected and linked to eating meat contaminated with mad cow disease, or bovine spongiform encephalopathy, in the mid-1990s, 141 people have died of the illness, which is caused by prion brain proteins that transform themselves into infectious agents.
It is difficult for scientists to predict how may people may get the illness or when it will peak because of the long incubation period, which experts say can be from 10-20 years or longer, and genetic factors that could influence susceptibility to the illness.
Previous estimates have ranged from less than 100 to up to 50,000.
“Although the numbers of cases are currently in decline, the possibility of further rises cannot be excluded,” the researchers said in the report.
They added that the findings reinforce the importance of safety measures to reduce the spread of vCJD through blood transfusions or surgical equipment.
Britain banned people who have had transfusions in the past two decades from donating blood after a report of what is thought to have been the world’s first case of vCJD caused by a blood transfusion.