International Association of Fish and Wildlife Agencies
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Phone: 202-624-7890
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Website: www.iafwa.org

• An Overview of Chronic Wasting Disease -- A Threat to Wildlife
• Special Chronic Wasting Disease Issue

An Overview of Chronic Wasting Disease -- A Threat to Wildlife

Chronic wasting disease (CWD) is an immediate and severe threat to the deer and elk of North America. Once confined to a small area in the western United States, CWD now has been found in wild deer in additional locations, as well as in herds of captive elk in several states and provinces. CWD can dramatically alter the management of wild deer and elk, and it has already begun to do so: In Colorado, Nebraska, Wisconsin, and Saskatchewan, efforts are underway to drastically reduce local wild cervid populations to eliminate CWD in areas where it recently was found. Wildlife enthusiasts, managers, and others must recognize the threat that CWD represents to our vast wildlife resources and take immediate actions to stop its spread throughout North America.

The origin of CWD is unknown. It was first recognized as a syndrome in captive mule deer held in wildlife research facilities in Colorado in the 1960s, but it was not identified as a transmissible spongiform encephalopathy (TSE) until the 1970s. CWD is distinctly different from other TSEs, which include Creutzfeldt-Jakob Disease of humans, scrapie of sheep and goats, and bovine spongiform encephalopathy, also known as mad cow disease. CWD occurs naturally only in cervids (members of the deer family) and currently there is no evidence that CWD poses a risk for humans or domestic animals. However, public health officials recommend that human exposure to the CWD agent be avoided as they continue to evaluate any potential risk. Scientists believe that unique infectious agents called prions, which fatally damage the brain, cause CWD and other TSEs. Lateral (animal to animal) transmission of CWD is thought to be the primary mechanism for maintenance of the disease in cervid populations. The minimal incubation period between infection and development of clinical disease appears to be approximately 16 months. The maximal incubation period is unknown, as is the point at which shedding of the CWD agent begins during the prolonged course of infection. Thus, deer and elk may shed the causative agent long before they appear to be sick. Currently, there is no practical live animal test, treatment, nor vaccine for CWD.The causative agents of TSEs, including CWD, are extremely resistant to degradation, which also raises the potential for indirect transmission via contaminated environments.

In the 1980s and 90s, CWD was recognized in wild elk, mule deer, and white-tailed deer in a limited area of northeastern Colorado and southeastern Wyoming. Through increased surveillance, this endemic focus has been determined to extend into adjacent western Nebraska. However, the recent identification of CWD in wild deer in areas remote from the endemic focus is much more alarming. Since late 2000, CWD has been detected in free-ranging deer in western Saskatchewan, northwestern Nebraska, southwestern South Dakota, southern Wisconsin, and the Western Slope of Colorado. The source of infection for wild deer in these areas is undetermined, but there is spatial correlation with infected, privately owned elk herds in at least three of these cases.

Since the mid-1990s, CWD has been documented in privately owned captive elk herds in Colorado, Kansas, Montana, Nebraska, Oklahoma, and South Dakota as well as in Alberta and Saskatchewan. There are confirmed epidemiological links between some, but not all, of the infected captive elk herds. In Saskatchewan, 38 herds of captive elk with CWD have been linked to a single "source" herd that apparently imported infected elk from a captive South Dakota herd in 1989. In late 2001, CWD infection was detected in captive elk shipped to three Colorado and Kansas herds from an infected facility in Colorado. This infected facility had shipped exposed elk to commercial operations in 19 states over the course of several years. In some positive captive herds in the United States, the source of infection is unknown. Most infected captive elk herds in North America were depopulated once detected, and federal efforts to eliminate CWD from the industry are being implemented or developed in the United States and Canada. However, undetected spread via trade of infected animals will probably continue until uniform surveillance and control programs are adopted and enforced.

The apparent spread of CWD between captive and wild cervids is a matter of hot debate. Although strong circumstantial evidence suggests that CWD has spread from positive captive elk to wild cervids in some instances, it may never be proven which group of animals represents the source of infection. Regardless of the direction of CWD's spread between wild and captive cervids, the threat that CWD represents to all deer and elk warrants immediate action by managers and authorities to mitigate risks.

Recognizing the risk for introduction of CWD via the movement of live animals, several state and provincial departments of agriculture and/or wildlife management recently have imposed bans or stringent regulations on live deer and elk importation. These regulations apply only to animals originating from areas where CWD has been detected in some cases, while in others, there is total prohibition of live cervid importation. Additionally, some states and provinces conduct mandatory surveillance of captive deer and elk, including herd records, individual animal identification and CWD testing of all cervid deaths, regardless of cause. Furthermore, millions of dollars have been spent in the United States and Canada, to buy, kill, test, and properly dispose of positive or exposed captive cervids.

Managing CWD in free-ranging deer and elk is extremely difficult because of the long incubation period, uncertainty about the mechanism of transmission, the possibility of new infections emanating from captive cervid facilities, and the potential for persistence of the causative agent in the environment. All of these difficulties are compounded by the inherent problems of detecting and managing diseases in wild populations. Thus, prevention must be regarded as the primary and most effective tool to combat CWD. Once established in a wild population, diseases are extremely difficult, and sometimes impossible, to eradicate. The current strategies to depopulate wild cervids by agency sharpshooters on Colorado's Western Slope and by public hunting in southern Wisconsin illustrate the dramatic efforts already underway to fight CWD.

There are several actions that can be taken by the wildlife community to prevent the establishment of CWD throughout North America's deer and elk:

Dealing with CWD will be difficult, expensive, and require extensive cooperation; however, the consequences of inadequate action must be considered. The wildlife viewing, hunting tradition, and tremendous economic stimulus provided by deer and elk easily justify swift, sound, and large-scale efforts to prevent CWD's spread. Public wildlife management and animal health agencies, private conservation and agricultural organizations, the captive cervid industry, hunters, wildlife watchers and the citizens of the United States and Canada must act quickly and strongly to preserve our wildlife heritage. A partnering effort that is focused, committed, and accountable is necessary to ensure that our nation's deer and elk remain healthy to be enjoyed by future generations.

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Inside IAFWA - June 2002
Special Chronic Wasting Disease Issue

CWD update
The recent identification of Chronic Wasting Disease in free-ranging deer in southern Wisconsin and the western slope of Colorado has drawn heightened attention to the disease and its potential for significant impact on deer and elk.

The state fish and wildlife agencies’ response to this real threat to North American deer and elk has been prudent, measured and focused, since there is much that is still unknown about this transmissible spongiform encephalopathy (TSE). Several states have passed, or are in the process of promulgating, emergency regulations prohibiting the importation into and transportation within the state of captive live cervids.

IAFWA has asked all state fish and wildlife directors to provide updated information on regulations regarding importation and transportation of live deer and elk in each state so that this information can be shared. An overview of CWD, assembled by IAFWA's Fish and Wildlife Health Task Force, has been made available for our members to use and distribute. It is also available through the Association's Web site at http://www.iafwa.org. Another good source of information is a special newsletter by the Southeastern Cooperative Wildlife Disease Study in Athens, GA. The newsletter can be accessed at the following address: http://www.uga.edu/scwds/briefs/0402brief.pdf.

Congressional action on CWD
The House Resources Committee held a hearing on CWD last month. Representatives from state agencies from four CWD endemic states (Wis., Colo., Neb., Wyo.) testified, as did representatives from the US Department of Agriculture, the US Department of the Interior and non-government organizations. The subcommittee chair asked federal agencies to provide Congress with an interagency strategy to help state agencies deal with this health problem. Witness testimony is available online at http://resourcescommittee.house.gov/107cong/forests/2002may16/agenda.htm.

Currently, there are two House and one Senate authorizing bills addressing CWD issues. The FY2002 supplemental appropriations bills include funds for work on TSEs. The House version provides approximately $10 million in funding, while the Senate version provides approximately $21 million. The supplemental appropriations bill is currently in conference committee.

Federal-state cooperative initiative underway on CWD
The recently established USDA/USDI task force on CWD has been expanded by co-chairs Steve Williams, director of the U.S. Fish and Wildlife Service and Bobby Acord, administrator of APHIS, to become a federal-state task force. The task force will draft a plan to assist the states in managing CWD, and although they are working under an ambitious deadline for Congress, both co-chairs have affirmed that nothing will go forward until the plan is a product states can support. State fish and wildlife agency representatives sit on the task force and its six working groups.

Chronic Wasting Disease symposium to be held in Denver
The Colorado Division of Wildlife, in cooperation with the Kansas Department of Wildlife and Parks, Nebraska Game and Parks Commission, Wyoming Game and Fish Department, and several NGOs, is hosting a national CWD symposium Aug. 6 and 7 in Denver. The symposium replaces the one originally scheduled for last September in Wichita. For more information, contact Rick Kahn, CWD conference coordinator, Colorado Division Wildlife, at 970-472-4342. More information will be available soon.

National Biological Information Infrastructure/CWD database developed
The National Biological Information Infrastructure program under BRD has funded a wildlife disease data system though the USGS National Wildlife Health Center in Madison, Wis. that creates a system to track the occurrence of Chronic Wasting Disease in Wisconsin.

According to project leader, Dr. Joshua Dein of the USGS, the system is capable of incorporating a large volume of data from the states and uses a GIS-based Internet Map Server to show where CWD is and is not occurring. The system can secure access to qualified individuals and organizations, incorporates many states’ data, maps other diseases, and links additional data.

Please contact Gary Taylor 202-624-7890 or gtaylor@sso.org for more information on these activities regarding Chronic Wasting Disease. For technical questions on CWD, contact Dr. John Fischer, chair of the Association’s Fish and Wildlife Health Task Force at 706-542-1741 or jfischer@cvm.vet.uga.edu.

The International Association of Fish and Wildlife Agencies represents all 50 state fish and wildlife agencies. For almost 100 years, IAFWA has been dedicated to the protection and management of our nation's fish and wildlife resources.

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