Chronic Wasting Disease of North American Cervids

Abstract

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy that has been reported in captive and free-ranging mule deer (Odocoileus hemionus hemionus), white-tailed deer (Odocoileus virginianus), Rocky Mountain elk (Cervus elaphus nelsoni) and moose (Alces alces shirasi). CWD has been reported in free-ranging cervids in 11 states and two Canadian provinces. CWD has been found in captive cervids in eight states and two Canadian provinces, but all of these herds have been depopulated except for three herds in Colorado. The mode of transmission of CWD is not known, but thought to be associated with ingestion of contaminated food or water from a contaminated environment. The primary clinical signs in cervids with CWD include weight loss and excessive salivation. Primary gross lesions include emaciation with loss of body fat. The hallmark histological lesion of CWD is spongiform encephalopathy. Diagnosis can only be confirmed with examination of the brain and/or lymphoid tissues with immunohistochemical staining. ELISA tests are used for screening large numbers of samples, for example during hunter kill surveys.