Easy "Mad Sheep"
Protein Test Found:
"Mad Cow" Test Possible?
By Barbara Hagenbaugh
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.
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.
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.
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.
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.''
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.
``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.''
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.
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.
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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