- BSE has been transmitted naturally between sheep for
the first time, a study has shown. Confirmation that such a thing is possible
reinforces fears that the disease may have entered sheep as well as cattle
on farms in Britain.
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- The revelation that lambs at a government experimental
station appear to have caught BSE from their mothers coincides with plans
to relax anti-BSE controls in cattle and was not mentioned at a meeting
of the Food Standards Agency in London this week.
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- Scientists will now seek to estimate from ongoing experiments
whether there was ever enough infection in flocks to make the disease survive
for long. No evidence of BSE has emerged from testing sheep in abattoirs
or on farms, although this did not begin until well after the BSE epidemic
in cattle was in steep decline.
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- Safety advisers have previously warned that any sheep
with BSE entering the food chain would be potentially far more dangerous
than a single cow, since there are far more parts of the animal that can
carry infection.
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- The report on infected lambs, in the journal Veterinary
Record, also comes as officials review contingency plans in case BSE is
ever found in sheep on normal farms. The present worst case scenario assumes
that around 25m sheep might have to be destroyed. There would be severe
shortages of sheep meat, since an entire year's crop of lamb, some older
sheep bred for mutton and many breeding ewes would have to be killed.
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- But the plans have been based on hypothetical models.
Now scientists from the government's Veterinary Laboratories Agency have
revealed that two ewes fed 5mg of BSE-infected material had lambs that
died of BSE after showing signs of infection in their tonsils, 546 days
after birth.
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- Their mothers had shown no outward signs of the disease
at lambing, one showing them 73 days after lambing, and the other 198 days
after.
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- But it is still not certain that the lambs were infected
while in the uterus, or shortly before or after lambing. The disease may
have spread through the birthing fluids or in some other way. The evidence
so far suggests this is far more likely than the lambs catching the disease
from other apparently unaffected sheep.
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- It is already known that BSE-like diseases can be transmitted
via blood in humans as well as animals, but there has been no evidence
that it has been handed from dam to calf in cattle, or mother to baby in
people.
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- The sheep involved were of a genetic type that in lab
tests previously appeared most susceptible to BSE. But it is unclear how
many such sheep are in flocks on farms. There are 15 different genetic
types, and unlike in BSE in cattle, genetic type seems important.
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- Unfortunately at present there would be no way of identifying
resistant sheep in time for them to go into food, while banning others.
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- The fear about sheep has existed for years because, until
the late 1980s, they were fed the same sort of feed as was fed to cattle.
However if it was ever in sheep, there is no suggestion that it ever existed
on a large scale.
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- There is some good news. The lambs that seem to have
inherited BSE showed a brain signature similar to BSE in cattle. Officials
have been worried that some BSE in sheep, if it existed, might have been
masked by a similar disease called scrapie, not known to be dangerous to
humans. The relatively small scale of the vCJD epidemic in humans so far
might give some reassurance too, given the size of an enormous BSE cattle
epidemic.
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- Peter Jinman, a leading veterinary surgeon on Seac, the
scientific body advising the government on anti-BSE measures, said: "This
clearly is an important finding. It is another part of the jigsaw."
Seac would consider the implications next month.
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- The Food Standards Agency said the study "adds to
the scientific knowledge in an area of continuing scientific uncertainty".
It did not advise the public against eating sheep, but would continue to
recommed "precautionary and proportionate measures".
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- The environment department, Defra, pointed out that nearly
2,700 scrapie samples had been tested for BSE since 1998 with no sign of
the disease, although two samples with anomalous results were still being
tested, using mice.
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- Guardian Unlimited © Guardian Newspapers Limited
2005
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- http://www.guardian.co.uk/bse/article/0,2763,1550343,00.html
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