The agent for a deadly disease affecting deer and elk herds in Colorado and Wisconsin was not detected in any samples from Oregon obtained during last year's hunting seasons, the Oregon Department of Fish and Wildlife announced.
Hunters voluntarily provided brain tissue samples to ODFW from 124 deer and elk harvested in late 2001 throughout Oregon to allow testing for chronic wasting disease (CWD). Of those, 99 were usable. All tested negative for the agent believed to cause CWD. Previous to 2001, ODFW tested 12 animals over five years that showed symptoms characteristic of CWD. They also tested negative.
Despite these results, state biologists remain extremely cautious.
"We can't say the disease is not here. The results are not statistically significant and we need more samples," said Don Whittaker, ODFW wildlife biologist. He noted CWD has been found in wild deer from western Colorado, Wisconsin, and most recently, southern New Mexico, which indicates the potential exists for the disease to cross major rivers and mountain ranges.
Whittaker was one of three ODFW biologists who attended a national meeting on chronic wasting disease this week in Denver. More than 400 researchers and wildlife managers attended to hear the latest findings from leading experts on CWD and similar diseases.
Whittaker brought home two lessons: 1) Disease sampling efforts need to be enhanced to obtain more usable samples from all areas of the state, and 2) Oregon must begin efforts to develop a response plan in the case CWD is detected.
Toward that end, ODFW hopes to test at least 500 hunter-harvested deer and elk this fall and winter. Samples will be obtained from hunters who voluntarily allow biologists to collect a small portion of the lower brain during hunting seasons. The sample is collected from the base of the head and will not harm taxidermy mounts. Hunters may be contacted in the field or may choose to deliver heads to ODFW offices throughout the state within 24 hours of harvest.
CWD is found in free-ranging or captive mule deer, white-tailed deer and elk in Colorado, Wyoming, Nebraska, Kansas, South Dakota, Montana, Oklahoma, Wisconsin, New Mexico, Alberta, and Saskatchewan. The untreatable disease leads to progressive loss of body condition, behavioral changes, excessive salivation, and death. In the later stages, small holes in the brain tissue of affected animals are visible with a microscope, producing a spongy look characteristic of transmissible spongiform encephalopathy (TSE). Similar TSE diseases exist in domestic sheep (scrapie), cattle (bovine TSE or mad cow disease), and humans (Crueutzfeldt-Jakob disease).
Researchers believe an abnormal type of prion protein serves as the disease agent. Prions have been found to occur normally in many animals. However, the origin and transmission method of CWD is not clearly defined.
In addition, it may take up to three years before animals show symptoms. While a live animal test recently was developed for mule deer, it is not feasible for sampling large wild populations. No live animal test exists for elk.
CWD is one of several diseases currently of concern to Oregon's wildlife experts. Others include adenovirus in deer, brucellosis in elk, hair loss in black-tailed deer, and bovine tuberculosis in deer and elk.