Mule deer doe with CWD.
Photo Courtesy of Wyoming Game and Fish Department
Chronic Wasting Disease (CWD) is a transmissible neurological disease of deer and elk that produces small
lesions in brains of infected animals. It is characterized by loss of body condition, behavioral
abnormalities and death. CWD is classified as a transmissible spongiform encephalopathy (TSE), and is
similar to mad cow disease in cattle and scrapie in sheep.
Infectious agents of CWD are neither bacteria nor viruses, but are hypothesized to be prions. Prions are
infectious proteins without associated nucleic acids.
Although CWD is a contagious fatal disease among deer and elk, research suggests that humans, cattle and
other domestic livestock are resistant to natural transmission. While the possibility of human infection
remains a concern, it is important to note there have been no verified cases of humans contracting CWD.
CWD can reduce the growth and size of wild deer and elk populations in areas
where the prevalence is high, and is of increasing concern for wildlife managers
across North America. The disease was long thought to be limited in the wild to
a relatively small endemic area in northeastern Colorado, southeastern Wyoming
and southwestern Nebraska, but has recently been found in several new areas
across the North American continent. The disease also has been diagnosed in
commercial game farms in several states and provinces.
Please refer to the Frequently Asked Questions and Map for an
up to date summary of CWD distribution.