Chronic Wasting Disease

What is it?
Chronic Wasting Disease, often referred to as CWD, appears to be a prion disease that attacks the central nervous system and causes fatal damage to the brain of white-tailed deer, mule deer, and Rocky Mountain elk. CWD is similar to, but significantly different from, scrapie (documented in domestic sheep for over 400 years), Bovine Spongiform Encephalopathy (BSE and often referred to as mad cow disease) and variant Creutzfeldt-Jakob disease (vCJD), and Creutzfeldt-Jakob disease (CJD). CJD and vCJD are the only nonhereditary prion diseases found in humans. All of these diseases attack the central nervous system and cause small holes to form in the brains of infected animals.
What Are the Symptoms?
In the later stages of infection, deer and elk infected with CWD will show signs of progressive weight loss, listlessness, excessive salivation and urination, increased water intake, depression and, eventually, death. Animals can be infected with CWD for months or years before outward signs of infection are evident. These symptoms are also found when an animal is infected with other diseases.
What Causes CWD?
The exact cause of CWD is not known at this time but the best scientific minds in the country feel that it is a prion disease. A prion is a mutated protein in the body that causes other normal proteins to fold abnormally and cause sponge-like holes in the brain. A growing body of research evidence indicates that this prion is the causative agent for CWD. The origin and life cycle of these prions are the target of ongoing research aimed at ultimately developing a management plan to eliminate, or at least contain, the existence of these prions in both wild and captive herds, as well as in the environment.
How Is It Transmitted Between Animals?
Although the exact method of transmission is unknown, it is known that CWD is transmitted from animal to animal. In all probability, the transmission is through body fluids like feces, urine, or saliva. Animals that are crowded or confined have a greater chance of encountering the body fluids of other animals and, therefore, a higher likelihood of becoming infected if the rogue prion is present. Animals that have a social system that includes close contact with herd mates also have a higher chance of becoming infected. Recent research indicates that CWD prions can survive in the environment after infected and exposed animals are removed.
Where Does CWD Occur?
CWD is a disease unique to North America. On our continent, it has been found in wild deer and/or elk in Colorado, Wyoming, Nebraska, South Dakota, Wisconsin, Utah, New Mexico, Illinois, and Saskatchewan, Canada. In captive deer and or elk, it has been found in Colorado, Montana, South Dakota, Oklahoma, Kansas, Nebraska, Wisconsin, Minnesota, Saskatchewan, and Alberta. Captive operations in Cherry County, Cheyenne County, and Sioux County Nebraska have had elk test positive.
The Cherry County herd has not had an incident since 1997 and is currently considered CWD free. The Cheyenne County and Sioux County herds have been depopulated. In addition, a penned herd of white-tailed deer (associated with the infected elk herd) in Sioux County has had a high rate of infection. This penned deer herd has also been depopulated. In the wild, CWD has been found in both mule deer and white-tailed deer. Free-roaming deer from Kimball, Cheyenne, Scottsbluff, Morrill, Banner, Box Butte, Dawes, Sheridan, Arthur, Hall, and Sioux Counties have tested positive for the disease.
How are Animals Tested for CWD?
Currently, the acceptable tests require a microscopic examination of an animal's brain stem, retropharyngeal lymph node, or tonsil. For the brain stem or lymph node tests, the animal must be dead. The tonsil test only works on deer, not elk. Tonsil tests are not practical to use on wild animals as they must be tranquilized and held in captivity until results are known. The screening test for CWD is the ELISA test and takes two to three days; confirmation tests (IHC) require a much longer time to validate the initial finding.
Can Humans Be Infected with CWD?
There is currently no scientific evidence that CWD has or can spread to humans, either through contact with infected animals or by eating the meat of infected animals. The Centers for Disease Control and Prevention has conducted an exhaustive study of CWD and human risk and has stated: "The risk of infection with the CWD agent among hunters is extremely small, if it exists at all." However, as we are still learning about this disease, the Commission recommends that hunters take precautions to limit risks. First and foremost, do not harvest any animal that appears sick or is acting strange.