- Scientists could take years to determine whether new
BSE-like diseases really are occurring in sheep, it has emerged.
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- Monitoring of thousands of animals has thrown up 26 more
unexplained results since the nightmare possibility that BSE had leapt
from cattle to sheep was revealed by government officials in September.
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- At that time 28 results from samples of nearly 30,000
sheep brains tested up to March were troubling experts. But the puzzling
results are continuing at roughly the same rate, scientists on the spongiform
encephalopathy advisory committee (Seac) were told.
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- Government and EU scientists are trying to establish
whether there is a problem with the testing method, and whether an unknown
type of scrapie, a BSE-like disease in sheep which has never been known
to be dangerous to man, or the far more lethal BSE is indeed in our flocks.
Meanwhile, the Food Standards Agency is not advising against the consumption
of lamb or sheep meat.
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- The unexplained results come from a rapid screening test
which should produce results overnight. Indications of a scrapie-like disease
have to be confirmed by another test that takes up to three weeks. In total
54 results have now not been confirmed but this might be because the quick
test is better at detection.
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- Work on establishing the tests' reliability might take
months, even after issues of commercial confidentiality over their exact
components have been settled. But meanwhile scientists want to start feeding
and injecting mice and sheep with brain material that provided the puzzling
results.
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- But this could take months or years and still prove inconclusive.
It is quite possible that the brain tissue of sheep has changed its "signature"
from normal but is not clinically infected with disease and therefore would
have no obvious effect on the laboratory animals. Some types of scrapie
also do not transmit at all to mice.
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- Scientists hope they might get an indication of what
might be happening from an experiment that is being conducted in Germany,
using material from a sheep there that threw up a confusing result.
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- Chris Bostock, the Seac member heading the investigations,
said: "We do not understand the basis for and significance of these
samples." The report from his group presented at Seac yesterday said
that the hypothesis that the samples represented pre-clinical BSE in sheep
could not be ruled out on the available evidence. But the patterns revealed
did not resemble those from sheep deliberately given BSE in the laboratory.
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- The scientists are seriously concerned by the lack of
brain material they can use for further tests. This is because abattoirs
have to safely dispose of heads of sheep before test results come back.
This rule might have to be altered.
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- Even sheep supposedly resistant to scrapie have shown
unexplained results, worrying for contingency planners already trying to
get farmers to breed these types. Scientists have suggested that sheep
known not to have scrapie should be tested but finding enough of these
in Britain would be difficult.
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- Some sheep have been imported from scrapie-free New Zealand
to use in BSE research but far larger numbers would be needed and it is
far from certain that the authorities in scrapie-free countries could,
or would want to, provide the numbers needed.
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- Guardian Unlimited © Guardian Newspapers Limited
2003
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- http://www.guardian.co.uk/bse/article/0,2763,1093937,00.html
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