PA (PA News) / Fri, Apr 28, 2000 / By John von Radowitz and Sam Greenhill, PA News
A study aimed at predicting how many people are likely to die from human
mad cow disease today left scientists no closer to knowing the answer.
Government-funded experts found no signs of variant CJD in 3,000 tonsil
and appendix specimens removed in operations since the 1980s, but warned
the results should not be seen as an all-clear.
The scientists, from the CJD surveillance unit in Edinburgh and
Derriford hospital in Plymouth, pointed out that these were the first
findings from a survey that will eventually examine tissue from around
18,000 samples.
At a news conference at the Department of Health in London, the
government's chief medical officer, Professor Liam Donaldson said: "The
fact that no positives have been found is welcome news, but these early
results should not be taken as an indication of an `all clear'.
"The methods of analysis used on the small sample of specimens have some
limitations. In addition we do not know at what point in the incubation
period tissues such as tonsils or appendices would turn positive, how long
the incubation period would be, or even whether any individuals who were
found positive would necessarily go on to develop the disease."
Variant CJD emerged in 1995 as a previously unrecognised form of the
human brain disease, and to date has claimed 53 confirmed victims in the
UK.
Most experts now accept that the variant CJD is a human version of the
cattle disease BSE and acquired from eating contaminated beef.
The majority of infections are thought to have occurred in the late
1980s before the introduction of controls to prevent contaminated meat
entering the human food chain.
How many people eventually succumb to the disease largely depends on the
length of its incubation period, which may be up to 20 years or more.
Estimates of the size of the epidemic range from just 100 or so cases to
hundreds of thousands.
Variant CJD is associated with a rogue prion protein which some experts
believe may be the infective agent.
It was the discovery of the abnormal protein in lymphatic tissue which
led to the new study being undertaken.
In late 1988 abnormal prions were found in the appendix of a man who had
developed variant CJD.
In addition scientists led by Professor John Collinge at St Mary's
Hospital, London, discovered the abnormal protein in the tonsils of
patients who had died from the disease.
Professor Les Borysiewicz from the University of Wales College of
Medicine led a scientific committee which reviewed the results of the
tonsil and appendix analysis.
He said that the study was limited but pointed out that scientists still
had no reliable diagnostic test to detect the presence of the disease while
it was incubating.
"This is the best we can do at the present time, but clearly other
methods as they come along will be used as well."
Prof Donaldson said: "This doesn't take us any further forward. We have
to still rely on the very, very wide estimates that scientists have already
made.
"This is a complex and mysterious disease and the results of today's
study throws a little bit more light on it, but it's very much an evolving
conundrum."
He said a perspective study had been commissioned from Prof Collinge
which would look at freshly taken samples of tonsil and appendix tissue.
One of the drawbacks of the current study was that the samples had been
stored for a long time.
Dot Churchill, whose 19-year-old son Stephen became the first confirmed
vCJD victim in 1995, said she was not surprised by the lack of positive
cases.
"It's not a lot different from what we expected," she said. "They are
half way through the research and this is quite a small sample.
"I think it's just too early to make any predictions, and as the chief
medical officer said we should not see this as the all clear.
"The disease is a very unknown quantity and we shall just have to wait.."
Mrs Churchill, from Devizes, Wiltshire, whose husband David chairs the
Human BSE Foundation, nevertheless thought the study worthwhile.
"Any research that gives us any answers at all has got to be welcomed,"
she added.
Copyright 2000 PA News
(posted without permission)
