Chronic Wasting Disease (CWD), one of the transmissible spongiform encephalopathies, is a fatal disease of the central nervous system of wild and captive elk, mule deer, white-tailed deer and moose. It has been found in wild populations in Colorado, Wyoming, Nebraska, Illinois, Wisconsin, Utah, South Dakota, New Mexico, West Virginia and New York as well as Saskatchewan and Alberta, Canada. CWD has been found in captive herds in several more states.
The causative agent is believed to be a sub-viral protein able to commandeer the normal protein-production system of brain cells, causing sheets of abnormal prion proteins to be produced in the brain; a “spongy” brain and signs of brain degeneration result.
Signs of illness are seen in mature animals, not young animals, because it takes a while for brain damage and signs of illness to develop. These signs include changes in behavior, weight loss, incoordination, tremors, circling or other repetitive walking, weakness, drooling, gait abnormalities and increased drinking and urination. Affected animals eventually become unable to rise. Death is inevitable.
Diagnosis of the disease is made by finding evidence of the abnormal prion protein in the brain or the characteristic “spongy” changes by microscopic examination. The abnormal protein can also be found in tonsils and lymph nodes during early incubation in some species, but not reliably.
The disease may be spread from infected females to their offspring by contact with the placenta or birth fluids or to herdmates through infected saliva, blood and possibly feces. Contaminated pastures or feeding areas may be a continued source of infection. Interspecies transmission between deer and elk is suspected as well.
There is no evidence that CWD is a human health concern, but certain disease control steps should be taken by hunters, meat processors, taxidermists and others who work with species at risk of CWD: