Libbie Miller: Chronic wasting disease cases remain low

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— Eight years ago, news of the discovery of chronic wasting disease in Northwest Colorado arrived like a thunderclap, with many communities expressing concern about the impact it would have on hunting in one of the state’s best big-game regions.

Fortunately, the worst fears have not come to pass.

CWD was first described as a clinical syndrome found in captive mule deer in Colorado in 1967 and was not documented in wild animals until 1981. By then, researchers had learned that CWD was among a small group of fatal neurological diseases called transmissible spongiform encephalopathies. These diseases now are thought to be caused by infectious protein particles called prions.

Throughout the past two decades, researchers have compared CWD to similar prion diseases, such as scrapie, bovine spongiform encephalopathy, or BSE, and Creutzfeldt-Jakob disease. Scrapie affects sheep and goats. BSE affects cattle. Creutz­­feldt-Jakob disease and kuru are extremely rare human diseases. A variant of Creutzfeldt-Jakob disease, described in 1996, is linked to consumption of BSE-contaminated meat and is distinctive from classic Creutz­feldt-Jakob disease.

Despite a number of epidemiological studies and laboratory experiments, no evidence has been found of CWD causing a human neurological disorder. Nevertheless, federal and state public health officials advise people to not consume any meat from a CWD-positive animal.

After the discovery of CWD on the Western Slope in 2002, CWD surveillance was increased, and wide-scale testing was implemented to learn more about where the disease was found and give hunters an opportunity to have their animals tested.

Roughly 2,000 samples were submitted statewide for CWD testing in 2001. The next year, that number skyrocketed to nearly 25,000. Since then, submissions have declined steadily each year, with fewer than 4,000 samples submitted in 2009.

We now know that CWD is widely distributed in Colorado. As of 2009, CWD has been detected in most of the Game Management Units in Northwest Colorado.

We also know that the disease remains relatively rare in most of the state. For example, in Northwest Colorado, estimated prevalence rates for elk and moose data analysis units average less than 1 percent, and estimated prevalence rates for deer data analysis units average less than 2.4 percent.

It’s possible that hunters in the field this fall may encounter an animal showing clinical signs of CWD. These animals may appear ragged and emaciated, lack coordination and generally fail to properly react to their surroundings. Hunters are advised to avoid these animals and notify the Division of Wildlife.

Most infected animals show no obvious signs, so the DOW advises hunters to take simple precautions when field dressing and processing animals. A complete list of these precautions can be found at http://wildlife.state.co.us/Hunting/BigGame/CWD.

DOW also continues to test hunter-harvested animals for $25.

In Northwest Colorado, hunters can drop off submissions at the DOW office in Steam­­boat Springs and the DOW warehouses in Craig and Walden.

CWD testing for moose is mandatory, and the testing is free.

Thankfully, CWD remains rare, but it appears it is here to stay. With a few simple precautions, hunters can continue to enjoy Colorado’s wonderful big-game hunting traditions confident that their days in the field will not only offer nutritious meals, but satisfying memories, as well.

Libbie Miller is the district wildlife manager in Yampa.

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