A team of veterinary epidemiologists and pathologists at Colorado State University is working with European researchers to study tests currently used in Europe for screening and diagnosis of bovine spongiform encephalopathy, and adapt them for diagnosis of chronic wasting disease in hunter-killed deer and elk in Colorado.
Epidemiologists with CSU’s Animal Population Health Institute and pathologists with the CSU Veterinary Diagnostic Laboratory are working with researchers from Prionics AG of Switzerland, and Bio-Rad France to devise faster, less expensive and less labor intensive screening tests for the disease before the fall hunting season arrives.
"We are in the process of validating these tests for our use because, although similar, BSE and CWD are not identical," said Dr. Mo Salman, director of the APHI at Colorado State. "So we are in the process of evaluating each company’s test through scientific-based validation, using our own stringent protocol."
Salman said the APHI has established the scientific, blind-test protocols and is overseeing the studies for validating the European tests. The CSU team includes technicians from the CSU Veterinary Diagnostic Laboratory, the Rocky Mountain Animal Health Laboratory of the Colorado Department of Agriculture, the Colorado Division of Wildlife and the USDA. The study is supported by the CSU Center for Economically Important Infectious Animal Diseases, which is funded, in part, by the USDA’s Cooperative State Research, Education and Extension Service.
The team will work with researchers from each company to conduct a study of at least four tests that are routinely used for the screening of BSE in cattle in Europe. Only tests that are reasonably valid for screening CWD will be selected for adaptation and implementation at the Diagnostic Laboratories in Colorado, then throughout the United States as more cases of CWD are being diagnosed in other states.
The Animal Population Health Institute works closely with the Veterinary Diagnostic Laboratory to provide reliable and scientifically based diagnostic tests for use in all potentially infectious animal diseases.
Hunters in Colorado may bring the killed deer or elk specimens into the Veterinary Diagnostic Laboratory for tests to determine possible infection by transmissible spongiform encephalopathies (TSEs).
"During the hunting season, the laboratory can handle up to 240 hunter-killed specimens daily, in addition to our other work," said Dr. Barbara Powers, Director of the CSU Veterinary Diagnostic Laboratory. "We use an immunohistochemical test, which we helped develop, and is now considered the ‘gold standard."’
But IHC testing is labor intensive, requiring technicians skilled in the preparation of tissue samples and slides. That means it’s also costly and ties up key staff. A rapid test would quickly eliminate animals that are negative and don’t require a more detailed test.
"We’re talking about going from 3-5 days for each hunter-killed specimen to 24 hours. This is a considerable difference," Powers says. "Furthermore, up to1000 samples can be processed per day by one or two laboratory technicians."
A rapid test would be used to determine if a sample has a "potential" for the presence of the disease agent. If the test shows a potential for CWD, then the IHC test would be utilized to confirm a negative or positive. If the rapid test shows no potential, the IHC test would not be required.
Transmissible spongiform encephalopathies are a group of neurodegenerative disorders that include scrapie, BSE and CWD in animals, and Creutzfeldt-Jakob disease and kuru in human beings. The TSEs are characterized by the accumulation, in the central nervous system, of an abnormal form of the naturally occurring prion protein, or PrP. The abnormal form is called PrPsc, for Prion Protein Scrapie.
"We are hoping that, together with other research we are conducting and disease control measures, a rapid method for the diagnosis of CWD in hunter-killed elk and deer will allow us to accumulate more specific information for studying the epidemiology and the pathogenesis of the disease," said Dr. Salman.
Researchers at CSU are also engaged in researching other methods of testing for CWD in live animals, eliminating the necessity for euthanizing those suspected of infection before a test can be conducted.