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From The
State Vet’s Office

by Tony Frazier

What is Chronic Wasting Disease?

Chronic wasting disease (CWD) is an infectious neurological disease of cervids, which include North American deer and elk. CWD is a transmissible spongiform encephalopathy (TSE), caused by an abnormal protein or "prion." This is similar to the disease agent that causes scrapie in sheep and BSE in cattle.

From the time the disease was first recognized as a clinical entity in 1967 it has mostly been limited to the geographic region of the western states and western Canada. More recently, it has spread into some mid-west states, then as far east as New York (diagnosed in March 2005) and most recently found in free roaming deer in West Virginia. The disease has not been diagnosed in any countries other than the United States and Canada, and there is no evidence of any relationship between CWD and other prion diseases in animals or man.

CWD was first reported in captive mule deer in the mid 1960s from a wildlife facility in Colorado. The exact origin of the disease cannot be established because, like many diseases, it may have existed for a while before it was recognized as a separate disease. That fact, along with the long incubation of prion diseases, makes it very difficult to pinpoint the cause of the original cases of the disease. CWD is a disease of adult deer, with the youngest documented case being in an 18-month-old deer. Most cases fit into the three- to four-year-old range, and have occasionally been seen in the eight- to nine-year-old range.

Chronic wasting disease is named for its most consistent characteristic—chronic weight loss accompanied by dehydration. The disease causes progressive degeneration of the central nervous system. Other clinical signs include changes in temperament (loss of fear of humans, nervousness, hyperexcitability), changes in behavior (teeth grinding, walking in repetitive patterns), incoordination, excessive thirst and urination, drooping of the head and ears, and excessive salivation. The incubation period (the time between becoming infected and showing signs of illness) is usually 18 to 24 months, but can range up to 36 months. The health of the animal usually deteriorates over a period of 12 months. There is no treatment for CWD and the infection is 100 percent fatal.

While the exact method of transmission is unknown, most experts think that CWD is most likely spread among cervids (deer) through contact with bodily fluids such as blood, saliva, urine and feces. Evidence exists that the disease may be transmitted from mother to offspring. The disease may be transmitted simply through a contaminated environment. Feeding areas tend to concentrate deer and may facilitate animal-to-animal transmission. For that particular reason, the disease prevalence in positive captive herds may approach 90 percent. And because of the concentration of animals and the environmental factors, it is very difficult to eradicate from a captive herd once the disease enters the herd.

Again, it is worth emphasizing that CWD has no proven human health risk. Because BSE is also a TSE, questions have been raised about the public health implications of CWD. A thorough investigation was done by the Center for Disease Control (CDC) and Prevention after two cases of classical Cruetzfeldt-Jacobs Disease (CJD), a human TSE was diagnosed in two men who were avid deer hunters. All related factors of these cases have been thoroughly investigated by the CDC and the official declaration from the center is that while caution in the hunting and processing of deer in CWD endemic areas is recommended, there is no known risk to the human population.

The State of Alabama Department of Agriculture and Industries, in cooperation with the USDA Veterinary Services and the Alabama Department of Conservation and Natural Resources have developed a CWD Surveillance Program through our state veterinary diagnostic laboratory system. Over the last three years more than 2,000 deer were sampled as a part of the surveillance program and all have tested negative for CWD. The surveillance program is already underway this year as well. There have been no CWD positive deer diagnosed in Alabama or neighboring states, and Alabama conservation laws restricting the importing of deer into the state serves as a firewall to keep the disease out.

It is strongly suggested that meat from deer that appear sick not be consumed. There are a number of diseases that could cause deer to be ill, some of which could affect humans. It is also recommended that the meat should be deboned using rubber gloves and be free of brain tissue, spinal cord or lymph nodes. If a hunter or landowner should see or harvest a deer that appears sick please contact the Alabama Department of Conservation and Natural Resources at 334-242-3469 or my office at 334-240-7253 to determine if any testing would be needed.

I want to encourage sportsmen and women to continue enjoying the outdoors of Alabama by hunting and rest assured of the safety of this great natural resource. 

Happy New Year!

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Date Last Updated January, 2006