Testing for chronic wasting disease (CWD) in tissues from deer and elk has begun in a specially outfitted facility in the New York State Animal Health Diagnostic Laboratory at the Cornell College of Veterinary Medicine.

The tests are part of a nationwide surveillance effort by the U.S. Department of Agriculture (USDA) to track the spread of the nervous system disease, which has infected deer and elk in several states but has yet to reach New York state. The Cornell lab is one of about a dozen nationwide to be designated by the USDA. Tissue samples are sent from a USDA center in Ames, Iowa, to regional laboratories where board-certified veterinary anatomical pathologists examine the samples for evidence of CWD and report results back to the agency.

The tests are being carried out by the state diagnostic laboratory at Cornell in cooperation with the USDA and the New York State Department of Environmental Conservation (DEC) and Department of Agriculture and Markets.

CWD is one of the family of diseases known as transmissible spongiform encephalopathies (TSE), caused by a folding "error" that changes the shape of normal body proteins called prions. Other TSEs include scrapie, which affects sheep and goats; bovine spongiform encephalopathy (BSE), or "mad cow" disease in cattle; and the human version of BSE, new variant Creutzfeldt-Jakob disease. In its present form, CWD is believed unlikely to affect humans, according to a study by the World Health Organization.

First detected in Colorado in 1967, CWD subsequently appeared in captive herds of deer and elk in Montana, Nebraska, Kansas, Oklahoma and South Dakota, as well as the Canadian provinces of Saskatchewan and Alberta. More recently, wild deer have been found infected with CWD in Colorado, Wyoming, Nebraska, Wisconsin, New Mexico and Illinois, prompting bans on interstate shipment of captive deer and elk as well as controlled hunts to kill all deer in selected areas, and widespread monitoring and surveillance by the USDA.

The test for CWD involves microscopic examination of brain tissue from dead animals, thin-sliced and stained with a marker specific for abnormal prion protein, according to Bradley Njaa, D.V.M., the pathologist in charge of CWD testing in the diagnostic lab. Preserved tissue samples undergo a series of mechanized steps to prepare them for examination. But the final call -- as to whether tissue samples show signs of CWD -- depends on visual examination under high magnification by a pathologist.

The USDA samples come from deer and elk that died as the result of seasonal hunting and controlled hunts, highway accidents and state-directed culling of animals. After test results are reported back to the USDA, samples will be stored at the Cornell facility for at least one year.

At present there is no reliable CWD test with living animals, although a test of tonsil tissue, taken from sedated animals, is under development. An eyelid test has been approved to diagnose scrapie in sheep, but a similar test for CWD in deer and elk has yet be to validated.

State Agriculture Commissioner Nathan L. Rudgers comments: "The introduction of CWD and other TSEs, coupled with the evolution of a global marketplace, has highlighted the need for prion diagnostic centers throughout the United States. I am proud that New York was selected to assist USDA in the development of new TSE technologies and am pleased to provide a technician to assist the New York State Animal Health Diagnostic Laboratory in protecting the health of our livestock as this country works diligently to detect, control and eradicate existing and emerging diseases, such as CWD."

DEC Commissioner Erin M. Crotty says: "New York state has implemented an aggressive program to prevent the introduction of chronic wasting disease, including a comprehensive sampling program to check for the presence of this disease in the state's deer herd. We continue to work closely with various partners to keep CWD out of New York state and have committed $260,000 for Cornell's new testing lab, which will greatly enhance our monitoring efforts and help us maintain a healthy deer herd."

"This is exactly the kind of work we should be doing as part of our mission at the New York State Animal Health Diagnostic Laboratory," says lab Director Alfonso Torres, D.V.M.. He notes that the lab is the only full-service, multidisciplinary animal-disease diagnostic facility in an area covering New York state and New England. "We are dedicated to improving the health of all animals and preventing infectious diseases that impact human and animal health," he says.

Torres adds: "Chronic wasting disease, if it can't be controlled, has the potential for serious consequences for elk and deer populations in the United States and Canada. We welcome the opportunity to do our part."