- WASHINGTON (Reuters) - Scientists have discovered an easy method to diagnose
a serious brain disease that has been known to kill sheep for centuries,
the U.S. Agriculture Department said Thursday, a finding that could someday
lead to a diagnosis for mad cow disease.
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- Researchers, however, cautioned that
they have not conducted studies on cows and said a link might never be
found. Scrapie, a degenerative and eventually fatal disease that targets
the central nervous systems of sheep and goats, could be easily detected
before the animals start to show signs of the disease and before they infect
others.
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- Scrapie has been associated with mad
cow disease, or bovine spongiform encephalopathy (BSE), which has killed
more than 160,000 cattle and has forced the slaughter of millions more
in Britain. Scrapie, BSE and Creutzfeldt-Jakob disease, which targets humans,
all involve prions, which are naturally occurring brain proteins that experts
say mutate into infectious and dangerous forms, resulting in the diseases.
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- Researchers at the USDA and at Washington
State University discovered that the third eyelid in sheep and goats collects
prions and developed a way to test lymphoid tissues for the presence of
the proteins.
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- Researchers said it is possible that
someday their discovery could be used to test for BSE. However, they stressed
that they have not conducted any research on cows and said that scrapie
and BSE act in very different ways when they attack animals. ``Scrapie
has been the problem in sheep in the United States and that is where our
focus has been,'' USDA research leader Donald Knowles said. ``Any kind
of diagnostic test that is made is usually species specific. Any kind of
speculation fuels unfair fire.''
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- Scientists think BSE was spread after
cattle were fed body parts of sheep infected with scrapie. The scrapie
discovery someday may lead to eradication of the disease in sheep and goats
in the United States, an important discovery in itself.
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- ``Until now, scrapie could only be confirmed
by examining the brains of dead animals,'' USDA Secretary Dan Glickman
said in a statement. ``Clearly, this is an important step toward controlling
the disease.''
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- Scrapie has been discovered in more than
900 flocks throughout the United States, the USDA said. There is no cure
for the disease, and producers who discover a sheep or goat with scrapie
often must destroy many animals in the flock to stop the spread of the
disease.
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- Controlling scrapie is also complicated
by the fact that animals can have the disease for up to five years without
showing any signs that they have been infected. It is hard to estimate
how many sheep and goats have been killed by scrapie because researchers
estimate that a large number of animals that die of the disease are never
properly diagnosed.
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- The new method is still winding its way
through the regulatory process and researchers said it is unclear when
the test will be put into practice. The new test will cost approximately
$25 per animal. Biopsies can cost as much as $500, USDA said.
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