PULLMAN, Wash.–USDA scientists working in collaboration with researchers in the Washington State University College of Veterinary Medicine have discovered that sheep eyelids hold the key to an easy, inexpensive test for diagnosing scrapie, a fatal brain disease in sheep.
Scrapie is a degenerative disease affecting the central nervous system of sheep and goats. It is a type of spongiform encephalopathy, similar to the disease known as Mad Cow Disease. In fact, current theories suggest Mad Cow Disease in Britain may have arisen from sheep scrapie. The announcement of the groundbreaking test’s development came late last week from the office of Agriculture Secretary Dan Glickman.
The test will allow producers and veterinarians, for the first time, to easily detect scrapie in sheep before the animals show signs of the disease. Until now, scrapie could only be confirmed by examining the brains of dead animals. The new test is an important step toward controlling the disease.
“This cutting edge scientific finding is yet another example that Washington State University’s College of Veterinary Medicine has the capacity and personnel to effectively attack diseases that truly have a global impact,” said Dean Borje Gustafsson. “Being in the forefront of disease research like we are here is essential to protecting both human and animal health in the state, the region, and worldwide.”
There is no known cure or treatment for scrapie, and scientists do not fully understand how it is transmitted. Sheep can harbor the disease for up to five years before they show signs such as trembling, incoordination or scraping against objects.
Under current USDA regulations, producers with confirmed cases of scrapie in their flock often must destroy animals in an effort to eliminate the disease.
The scientists estimate that the new eyelid test will be performed for about $25 per animal once it is commercially available. Current tests require biopsies of internal organs, which is more risky and can cost up to $500 per animal.
In developing the test, researchers at the USDA’s Agricultural Research Service in Pullman, working with WSU veterinary researchers, discovered that the third eyelid in sheep collects prion proteins believed to cause scrapie. They also developed a new antibody to identify the disease-causing form of the proteins in a sample of eyelid tissue.
The scientists have applied for patents on both discoveries. The WSU/USDA research team has been researching spongiform encephalopathies for nearly two decades.
ARS microbiologist Katherine I. O’Rourke led the team responsible for the breakthrough. Others on the team include Donald P. Knowles, who heads the Pullman ARS lab; Timothy V. Baszler and Steven M. Parish, both faculty members in the WSU veterinary college; and Janice M. Miller at the ARS National Animal Disease Center in Ames, Iowa.
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Editors and Reporters: Donald P. Knowles, 509/335-6022; fax 509/335-8328; dknowles@vetmed.wsu.edu. A USDA fact sheet on scrapie is available on the World Wide Web at
