16,000 In UK May
Have Mad Cow

By Roger Highfield
The Telegraph - UK
Between 1,300 and 16,000 people may harbour the human form of BSE, depending on who interprets the findings of a study published today.
Eight years after vCJD was linked with BSE the Department of Health-backed study fails to show how many people will eventually die.
The scientist who reports the work said he would rather not have estimated vCJD prevalence, given various caveats, and the head of the Prion Unit in London said it was "worrying" and might suggest current vCJD patients are the first wave of a bigger epidemic.
The findings will increase pressure to use new decontamination methods, since they underline fears that routine operations may spread the disease.
The research is published in The Journal of Pathology by Dr David Hilton, of the Derriford Hospital, Plymouth, and colleagues who examined 12,674 appendix and tonsils (mostly the former), from people from the highest risk group, mostly in their twenties.
Three vCJD positives emerged. Extrapolating, Dr Hilton estimates 3,800 people have human BSE but stressed caution in interpreting the results.
Given the handful of positives, the survey lacks statistical power; because the samples were fixed in paraffin wax, the team was unable to use a definitive vCJD test; nor was it able to establish the genetic subtype of the affected people; and two of the three positives appear different from samples taken from vCJD patients.
Dr Azra Ghani, of Imperial College London, the co-author, listed three possibilities: perhaps there were two false positives, so the projected number of cases will be 1,300, in line with recent estimates.
Perhaps the level of infection is higher than thought: the positives are in a different genetic subtype of person than vCJD cases to date and there could be a second wave of longer incubation outbreaks in other subtypes.
Perhaps some infected people do not go on to develop symptoms, consistent with a recent decline in the number of reported vCJD cases, though may still be able to spread vCJD.
But the real situation could be worse, said Prof John Collinge, head of the Prion Unit at University College London. The majority of samples were from appendices, which harbour lower levels of rogue prions than tonsils.
According to his research on patients who had died of the disease, only one out of four appendices showed a positive, when tonsils are always positive in vCJD.
This would imply that the number of affected people is 16,000. Prof Collinge would not be drawn on numbers but said the results are "very concerning".
"No test is going to be 100 per cent effective, and you don't know at what stage in the incubation period the test either on tonsil or appendix will be positive."
He said the Government should re-examine the question of using disposable surgical instruments.
Advice to use them was introduced for a time but withdrawn in England about two years ago because of safety worries.
A spokesman for the Department of Health, which has spent £200 million on sterilisation equipment and throwaway instruments, said: "The results reinforce the need for a continued precautionary approach."
The Health Protection Agency is currently engaged in a major vCJD screening project in which 100,000 fresh tonsil samples will be directly tested, on an anonymous basis, for vCJD prions and can also be analysed for genetic subtype.
Prof Pat Troop, the chief executive, said it "should provide better estimates of the number of people who may be affected".
"This is urgent," said Prof Collinge, "we need to get on with it."
© Copyright of Telegraph Group Limited 2004.



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