March 10, 2005
Prions: From the lab to the barnyard and wildlife
Transmissible brain diseases among livestock and wild game have become a growing concern in veterinary medicine, agriculture, and public health.
Mad cow is probably the most widely known of these diseases in farm animals. There is also scrapie, a degenerative disease recognized since the 1700s. Scrapie attacks the central nervous system of sheep and goats.
Out in the woods, chronic wasting disease has been found in mule deer, white-tailed deer, and elk. An affected animal will become very thin, slobber and drool, urinate excessively, and lose its shiny coat. Death occurs about four months after symptoms appear. Mink and wild cats have wasting diseases, too.
All of these disorders are thought to be prion diseases. The prion is a normal protein that, through a process that is not yet understood, changes its shape and becomes toxic to the central nervous system. At autopsy, a brain affected by abnormal prions looks riddled with tiny holes and small tunnels and resembles a sponge. Because of this anatomical damage, these diseases are called spongiform encephalopathies.
This year’s WWAMI Science in Medicine Lecture is Dr. Donald Knowles, who heads the research program in persistent infectious diseases at the Animal Disease Research Unit of the Agricultural Research Service, United States Department of Agriculture (USDA). This unit is located within the College of Veterinary Medicine, Washington State University (WSU) in Pullman.
This laboratory, in collaboration with the WSU College of Veterinary Medicine and the National Animal Disease Center at the USDA Agricultural Research Service, validated the lab test used in diagnosing the first cases of bovine spongiform encephalopathy in the United States and in Canada. The program is now determining the methods by which prion diseases are transmitted, and defining role of prion genetics in resistance to prion diseases.
Knowles will speak on, “Prion Diseases in Domestic Animals: Are Only the Cows Mad?” at noon, Thursday, March 24, in Room T-625 of the UW Health Sciences Center. His talk is free and open to everyone. It will be simultaneously televised to the Harborview Medical Center Research and Training Building Auditorium, and to Room 518, Building 1, of the Veterans Affairs Puget Sound Health Care System.
Each year a noted scientist who teaches University of Washington first-year medical students at one of the other five state universities in the WWAMI (Washington, Wyoming, Alaska, Montana, and Idaho) program of regionalized medical education is invited to the UW to give the WWAMI Science in Medicine Lecture.
Knowles is a research leader of the Animal Disease Research Unit, USDA Agricultural Research Services, and a professor on the WSU graduate faculty in the Department of Veterinary Microbiology and Pathology. He is also a UW affiliate professor of comparative medicine. He has lectured on prion diseases in a UW epidemiology course on diseases communicable from nature. At WSU he has lectured on animal infections of international significance, such as those that can result in trade prohibitions or that might be used in attacks on agricultural settings.
Knowles’ research group, including Katherine O’Rourke from the USDA Agricultural Research Service and Steven Parish and Timothy Baszler from WSU, is best known for developing the first, practical, live-animal diagnostic test for scrapie. The test uses antibodies to detect prion protein. The test checks a tiny specimen taken from the third eyelid of a sheep or goat, and can be used before symptoms appear. Previously, the disease could be detected only by slaughtering animals suspected of having the illness, and contained by quarantining and culling the herd.
Related findings, as well as his team’s discoveries on prion distribution in goat scrapie and genetic resistance to sheep scrapie, have become the basis of the National Scrapie Eradication Program. The goal is for the United States to eventually be declared free of scrapie.
The creation of the scrapie test built on previous achievements of Knowles’ research teams. Their studies have led to diagnostic methods or management recommendations for four other persistent infections of large, domestic animals. For example, his team developed a tool for detecting caprine arthritis-encephalitis viral infections. This slow virus can cause chronic swelling of a goat’s joints, and, rarely, inflammation of its brain. His group and collaborators combine the disciplines of immunology, genomics, molecular biology, and pathology to study a group of diseases that cause life-long infections in domestic animals.
Knowles has received numerous honors, including several USDA Certificates of Merit and the Secretary of Agriculture Award for Professional Excellence. In 2001 he was named the Senior Distinguished Scientist for the Agriculture Research Service of the USDA. This past year WSU named him a world-class inventor for the technology transfer and commercialization of several infectious disease tests.
Knowles is a 1978 alumnus of the University of Illinois, where he received a bachelor’s degree. He studied to be a veterinarian at the College of Veterinary Medicine of the University of Illinois at Urbana. There he was a research associate while earning a D.V.M. degree. He obtained a Ph.D. degree in veterinary pathology and microbiology from Washington State University. He is a diplomate in the American College of Veterinary Pathologists.
