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New Study Indicates Thousands of Britons May Be Incubating Mad Cow Disease

>From BBC News (UK) 5/21/04

Thousands may be harbouring vCJD

The scientists studied over 12,000 tissue samples
Scientists have found evidence to suggest that more people could be
harbouring the human form of BSE than previously thought.
Researchers at Plymouth's Derriford Hospital and the CJD Surveillance
Unit tested 12,674 appendix and tonsil samples - three showed signs
of vCJD.

Extrapolating their findings to the whole population, they estimated
that 3,800 Britons may harbour the disease.

The findings are published in the Journal of Pathology.

A total of 141 people have died from vCJD in the UK since the disease
emerged in 1995.

Scientists have been suggesting that the number of deaths from the
disease had peaked.

Q&A: How many are infected?
A recent study by researchers at Imperial College London predicted
the disease would claim no more than 540 lives.

However, the truth is nobody knows how many people carry the disease,
let alone how many will die from it.

This is because scientists do not know the incubation period of the
disease - how long it lies in the body before symptoms appear.

'Much to learn'

The scientists who carried out this latest study said their findings
should be interpreted cautiously.

"Our findings need to be interpreted with caution, but cannot be
discounted," said lead researcher David Hilton.

"There is still much to learn about vCJD and presence of the protein
in these tissue samples does not necessarily mean that those affected
will go on to develop vCJD."

Professor James Ironside of the National CJD Surveillance Unit in
Edinburgh said the findings suggest some people could carry the
disease without ever showing any symptoms.

"There would seem to be more positives than you would expect given
the known number of vCJD cases and the fact that they seem to be
declining.

"That may be because of genetic differences and susceptibility, but
it may also be that you can have a sub-clinical infection which never
progresses to produce symptoms - a 'carrier state'.

"I think the findings do have to be taken seriously. Generally, one
has to be cautious about interpreting these data, but they may
indicate that there are people who are not infected in the normal way
but could represent a source of infection."

The researchers said the findings highlighted the importance of
reducing the risks of people transmitting the disease.

In March, the UK government announced that Britons who had a blood
transfusion after 1980 would be banned from donating blood.

It followed reports that one man who died from vCJD may have
contracted the disease as a result of transfusion.

'Very concerning'

Professor John Collinge, head of the Medical Research Council Prion
Unit at St Mary's Hospital, London, said the government should look
again at whether surgeons should use disposable instruments in
operations where there may be a risk of transmission, such as the
removal of tonsillectomies.

He said he was worried by these latest findings and suggested
estimates that 3,800 people have the disease may be too low.

"I find these results very concerning," he said. "Our experience is
that looking at appendix samples will under-estimate the true
picture.

"In addition, no test is going to be 100% effective, and you don't
know at what stage in the incubation period the test will be
positive."

The scientists, who carried out this latest study, have been carrying
out tests on appendix and tonsil samples for a number of years.

In 2002, they announced that they found vCJD prions in one out of
8,300 samples tested.

It prompted the government to set up a national tissue archive to
enable scientists to carry out further tests.

Scientists hope to collect 100,000 tonsil samples left over from new
operations. These will be tested, on an anonymous basis, for vCJD
prions.

Professor Pat Troop, chief executive of the Health Protection Agency,
said: "The larger scale of the study should provide better estimates
of the number of people who may be affected."

A Department of Health spokesman said: "There is still much to learn
about vCJD and this study is important for future research.

"The results reinforce the need for a continued precautionary
approach to minimise people's exposure to BSE and vCJD.

"The Department of Health has already put in place measures to reduce
any risk of possible transmission of the disease via blood products
and surgical instruments."

http://news.bbc.co.uk/2/hi/health/3729901.stm
<http://news.bbc.co.uk/2/hi/health/3729901.stm>