- Sheep with scrapie may be able to pass a kind of mad
cow disease to humans, a new study shows.
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- Cattle get bovine spongiform encephalopathy -- BSE or
mad cow disease -- from a dangerous prion (an abnormal form of normal cell
protein) called PrPsc. When humans eat PrPsc in contaminated beef, it can
give them the human version of mad cow disease called variant Creutzfeldt-Jakob
disease (vCJD). Scientists say vCJV comes from eating nerve tissue (such
as that in the brain and spinal cord) from cattle infected with mad cow
disease.
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- Sheep have their own form of the disease. It's called
scrapie -- a fatal, degenerative disease affecting the central nervous
system of sheep and goats.
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- Eating meat -- which is muscle -- of sheep with scrapie
is not supposed to be dangerous to humans. But now researchers report finding
PrPsc in sheep muscle. The findings, by Olivier AndrÈoletti of the
National Veterinary School of Toulouse, France, and colleagues appear in
the May 23 advance online edition of Nature Medicine.
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- "Dietary exposure to scrapie is currently considered
nonhazardous to humans," AndrÈoletti and colleagues write.
"However, the presence of PrPsc in muscles from sheep naturally infected
with scrapie calls for a review of this question."
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- Making such a "review" more urgent is the recent
finding that sheep can become infected with BSE as well as scrapie.
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- It's not clear exactly how much PrPsc-contaminated meat
a sheep would have to eat to pose a danger to humans. Sheep have about
5,000 times less PrPsc in their muscles than they do in their brains. And
the sheep in the AndrÈoletti team's study had to eat massive amounts
of PrPsc to accumulate significant levels of the protein in their muscles.
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- "This is the first evidence for PrPsc in muscle
from TSE-incubating animals of a species that enters the human food chain,"
AndrÈoletti and colleagues note.
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- SOURCE: Andreoletti, O. Nature Medicine, May 23, 2004;
advance online edition.
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- © 2004 WebMD Inc. All rights reserved.
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- http://my.webmd.com/content/article/87/99548.htm?
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