Chronic Wasting Disease, more commonly referred to as CWD, is a disease that infects white-tailed deer (Odocoileus virgianianus), mule deer (Odocoileus hemionus), elk (Cervus elaphus), and moose (Alces alces). CWD is related to other transmissible spongiform encephalopathy (TSE) diseases that include scrapie in sheep, mad cow disease in cattle, and Creutzfeldt-Jakob (CJD) disease in humans.
Unlike mad cow disease and its variant CJD, there is no evidence to date that humans can contract CWD from eating venison. However, relatively little is known about CWD and as a result, researchers and public officials err on the side of caution when dealing with the disease and public safety. Ongoing research will provide further insight into the wildlife and human health implications of CWD, but until then, it’s vigilance ensuring local deer populations are well monitored with plans are in place to contain the disease.
TSE diseases such as CWD are believed to be caused by prions, which are abnormal, proteinaceous, infectious particles. Prions are closely related to cell proteins that are typically produced in the tissue of the central nervous system and other body tissues. However, prions or abnormal cell proteins cannot be broken down by the body’s enzyme system. Prions collect in nerve tissue, cause the death of nerve cells and result in loss of normal neurological function. Damage to the brain’s nervous system tissue causes spaces (holes) visible under microscopic examination.
A CWD-afflicted deer. Note the emaciated features and sagging posture.
CWD is believed to be spread either by direct contact between animals or indirectly through the environment. The long incubation period is apparently no less than 15 months. CWD clinical signs only appear as the animal approaches death. Clinical signs include emaciated appearance, excessive thirst and urination, drooling, lack of coordination, and abnormal behavior. Such behavior includes holding the head and ears in a lowered position, remaining in an area with water sources, repetitive walking and standing with a widened stance.
Current Distribution: Initially, in the 1960s, CWD was thought to be a nutritional malady in captive mule deer in Colorado. In 1978 CWD was identified as a TSE. As of mid-2007, CWD has now been found in free ranging deer and elk in Colorado, Wyoming, Utah, Nebraska, South Dakota, Wisconsin, New Mexico, Illinois, New York and West Virginia, as well as the Canadian provinces of Saskatchewan and Alberta.
Captive deer and elk with CWD have been found in Colorado, Wyoming, Kansas, Montana, Nebraska, Oklahoma, South Dakota and New York, and in Saskatchewan and Alberta.
Status in Delaware: DNREC’s Division of Fish and Wildlife began sampling random hunter-harvested deer for CWD in 2003. Over the last four years, nearly 1,900 deer have been tested without detection of CWD in Delaware.
A healthy young white-tailed buck gambols toward its forage.
Under the current sampling regime, there is a 99 percent probability of detecting the disease if it is present in greater than 1 percent of the deer population. Along with random sampling of hunter harvested deer, the Division of Fish and Wildlife will conduct targeted surveillance on sick animals that exhibit symptoms associated with animals infected with CWD. Also, any live cervid (exotic or native) found to have been illegally imported into the state will be euthanized and tested.
