North America: Chronic Wasting Disease
CWD belongs to a family of diseases known as transmissible spongiform encephalopathies (TSE). Within this TSE family of diseases, there are three predominant variants that affect animals: scrapie, which has been identified in sheep for more than 200 years; bovine spongiform encephalopathy in cattle (sometimes referred to as Mad Cow Disease); and CWD in deer and elk (cervids).
CWD has been endemic in portions of northeastern Colorado and southeastern Wyoming since its discovery in wild deer in 1981. However, recent discoveries of CWD in free-ranging deer in Nebraska, South Dakota, Wisconsin, Saskatchewan, and the west slope of the Rockies in Colorado have heightened concerns about the distribution and prevalence in wild deer and elk populations throughout North America.
CWD had also been found in captive cervid facilities in at least five states and provinces. Additional discoveries in captive operations have also increased awareness of the movement of privately owned animals across the country, and the potential for CWD to spread through the transport of unknowingly-infected animals. Twenty-three states perform captive cervid testing for CWD in dead animals and others are in the process of developing surveillance. Fourteen states have specific restrictions for importing from certain states or provinces.
While disease testing has been required for interstate movement of privately owned animals have been required, no live animal test for CWD existed prior to this year. Researchers in Colorado have developed a test that will work on live animals, but the procedure apparently works only for mule deer. The procedure is costly and the animal must be tranquilized to be tested.
Several states have begun monitoring programs for CWD in hunter harvested deer in the last few years, with the most extensive testing being done by Colorado and Wyoming. Wisconsin had looked at a cumulative sample of approximately 1000 hunter harvested deer during the past three years and found the positive animals in this past year's sample, when 400 were tested.
What to do while in the field:
- Be alert for deer, elk, or other cervids acting abnormally or appearing to look sick, report any such animals to agency officials.
- Wear rubber or latex gloves when you field-dress your animal.
- In areas where CWD has been reported, minimize your contact with a dead cervid's brain and spinal cord and wash your hands after contact.
- Don't eat a cervid's brains or spinal cord.
- Bone out your meat and discard the brain, spinal cord, eyes, spleen, and lymph nodes.
- If animal is from a CWD-suspect area, unused parts, especially skull and spine, should be disposed in an approved landfill or incinerator.
As with the cases of TB discovered in Michigan, hunters are generally the first to notice something unusual in harvested deer and report these cases to the agency. Agencies are currently developing rules and guidelines for the upcoming year, so hunters should inquire whether sampling is being done in their hunting area and contribute animal samples whenever possible. Get informed about CWD research in the state and area you hunt.
Where CWD has been discovered, states are taking action to reduce animal population densities well below current levels. In some cases, such as the west slope of Colorado, complete eradication of deer and elk within a five-mile radius before spring migration begins is being attempted. Wisconsin has announced that a 90% reduction in deer numbers in their affected area is the immediate goal. Hunters and landowners should assist agencies by purchasing licenses when available and harvesting animals in those management units where population reduction is recommended by the agency.
Where authority is given, agencies are also beginning to regulate those practices that are conducive to disease spread, such as supplemental feeding and the use of bait. In other states, legislatures are being petitioned to take action through the legislative process or to grant such authority to agencies. While many may believe that these traditional practices of supplemental feeding and the use of bait are important to wildlife conservation, the threat of disease may require a re-examination of these practices.
At least five states (Michigan, Texas, New York, Indiana, Illinois) and some Canadian provinces have closed their borders to importation of all captive cervids (deer and elk). Some states allow only boned meat, hide, and/or antlers (no skull) to be removed from CWD areas. Other states are prohibiting importation from states or portions of states with documented CWD. Further action may occur as new regulations are being developed. Hunters from other countries should check with appropriate officials to determine if a CWD test is required to import trophies (either wild or from high-fence facilities) into their country of origin.
New information appears almost daily on CWD, www.cwd-info.org/. Check your state wildlife agency website for information and links to other sites.