Diseases - Chronic Wasting Disease Study
Chronic wasting disease (CWD) has emerged within the last two decades as a concern for deer and elk. This disease is a transmissible spongiform encephalopathy (TSE), similar to mad cow disease, in which the disease agent is thought to be a "prion" or abnormal protein particle. Spongiform encephalopathies are characterized by brain tissue that has a "spongy" appearance under microscopic examination. Clinical symptoms of CWD include loss of body condition and weight, excessive salivation, ataxia, and behavioral changes. The disease is transmissible between deer and elk and ultimately results in death.
To examine the factors associated with CWD, a 3-year study on both white-tailed and mule deer in Wind Cave National Park is being conducted by researchers from South Dakota State University. A helicopter capture in late February 2003 resulted in 27 mule deer captured, anesthetized, tested for CWD, and radio collared. A live test for CWD can be done on deer species (there is currently no live test for elk) by taking a biopsy sample of the tonsil. Prions accumulate in the tonsils before clinical symptoms appear. After the tonsillar biopsy, these deer were fitted with either a VHF or GPS (global positioning system) collar. The goal of 40 deer for the project was reached during March by trapping and darting 10 more mule deer and 3 white-taileds. One female 4.5-year-old mule deer did test positive for CWD and was found dead a few days later. All other animals tested were negative for CWD and are currently being monitored for clinical signs of CWD, movement patterns, including dispersal and migration, transgression of the park fence, and other factors relevant to CWD. These animals are relocated by radio telemetry 1-3 times a week. Since deer density may be important in CWD transmission and there are no reliable estimates of deer density at Wind Cave National Park, aerial surveys will be conducted over the next 3 years to estimate the deer population within the park.