Chronic Wasting Disease (CWD) is related to a group of diseases known as transmissible spongiform encephalopathies (TSEs). TSEs include such diseases as scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle (aka Mad Cow Disease) and Creutzfeldt-Jakob disease of humans. TSEs are diseases of the nervous system that result in distinctive lesions in the brain. The causative agent is believed to be a modified protein (prion). These modified proteins are typically found in nervous and lymphatic tissues, but recent experimental evidence shows prions can occur in muscle tissue of mice.
The recent detection of CWD in the wild white-tailed deer herd in Wisconsin is of particular concern. White-tailed deer appear more susceptible than mule deer and elk to CWD with a greater percentage of the herd becoming infected. Until now, CWD was found in white-tailed deer herds in Colorado, Wyoming, and Nebraska where deer occur at densities of approximately 2-5 deer per square mile. In contrast in Wisconsin, deer are found at 75+ animals per square mile (conservative estimate by WDNR). No one knows how rapidly CWD will infect white-tailed deer at these densities or what long term affect this disease will have on a herd of this size (approximately 1.6 million animals).