Detection and Management of Chronic Wasting Disease in Wisconsin White-Tailed Deer (Odocoileus virginianus)
Chronic wasting disease (CWD) is a progressively degenerative and ultimately fatal disease of deer (Odocoileus spp.) and elk (Cervus elaphus) associated with transmissible protease-resistant prion proteins.3 From the recognition of CWD as a transmissible spongiform encephalopathy in 1978 until 2000, the range of CWD in wild cervids was thought to be limited to Colorado, Wyoming and Nebraska. In the last 3 yr, CWD has also been detected in wild deer and elk in Illinois, New Mexico, Saskatchewan, South Dakota, Utah, and Wisconsin. CWD has been documented in captive cervids in Alberta, Colorado, Kansas, Minnesota, Montana, Nebraska, Oklahoma, Ontario, South Dakota, Saskatchewan, Wisconsin, and Wyoming.
The detection of CWD in Wisconsin was the first report of CWD in wild cervids east of the Mississippi river. Between 1999 and 2001, the Wisconsin Department of Natural Resources (DNR) had tested 1100 white-tailed deer for the presence of CWD. In 2001, three males, 2.5–3.5 yr of age and shot within 3 miles of each other, were found to have CWD on immunohistochemical analysis of brainstem samples. After subsequent sampling of 476 deer within an 11 mile radius of the three index cases revealed 15 additional CWD-affected deer, Wisconsin initiated a CWD management program with the goal of controlling spread of the disease and, if possible, eliminating it.1
Wisconsin's CWD management to date has included intensive statewide surveillance, significant deer population reduction in the known affected area, the passage of legislation to ban deer feeding and baiting for hunting, and the implementation of an import moratorium and CWD monitoring program for farmed cervids. Since the beginning of 2002, lymph nodes from approximately 40,000 wild white-tailed deer harvested by hunters across the state have been screened by immunohistochemistry for evidence of CWD. Over 200 CWD-affected deer have been detected, all within 35 miles of the index cases in south-western Wisconsin.2 Using liberal hunting seasons and targeted harvesting by agency staff, the deer population in the affected area has been reduced by 25%. Mandatory testing of all farmed cervids transferred live or slaughtered has resulted in the detection of three CWD-affected farms (one elk farm, two white-tailed deer farms).
The Wisconsin CWD outbreak is part of a significant expansion of the known range of this disease, and evokes particular concern as very high deer densities in southern Wisconsin may facilitate rapid transmission of the agent and may have significant negative impacts on this important wildlife resource.
The authors would like to thank the many colleagues in the Wisconsin state agencies, USDA-Veterinary and Wildlife Services, the U.S. Geological Survey, and University of Wisconsin for their contributions to the work summarized in this report.
1. Bartelt, G., J. Pardee, and K. Thiede. 2003. Environmental impact statement on rules to eradicate chronic wasting disease from Wisconsin's free-ranging white-tailed deer herd. Wisconsin Department of Natural Resources Pub-SS- 980. http://www.dnr.state.wi.us/org/land/wildlife/whealth/issues/cwd/. (VIN editor: link could not be accessed on 2/9/21)
2. Williams, E.S., M.W. Miller, T.J. Kreeger, R.H. Kahn, and E.T. Thorne. 2002. Chronic wasting disease of deer and elk: a review with recommendations for management. J. Wildl. Manage. 66:551–563.