Map of North America showing locations where chronic wasting disease has been detected (2020)
Chronic wasting disease (CWD) was first discovered in a population of captive mule deer in Colorado in the late 1960s. Since that time, the disease has spread to wild populations in multiple states, as well as parts of Saskatchewan, Alberta, and British Columbia.
CWD is part of a unique group of diseases called transmissible spongiform encephalopathies (TSEs). This type of disease is not caused by a virus, bacterium, or parasite, but rather misfolded proteins called prions. Prions have the ability to misfold other surrounding proteins, effectively producing more prions within the organism. This accumulation of prions leads to gradual degeneration of the brain, and in the case of CWD in deer, the disease is fatal. While the biochemistry of CWD and the physiology of infected animals are understood, the origin of CWD-causing prions is still unknown, and the prevalence of CWD transmission from deer to deer is currently under investigation. To date, there is no cure for CWD.
The following video provides more information on the disease from the perspective of experts in the field as well as hunters: