Chronic Wasting Disease

Chronic Wasting Disease (CWD) is a fatal neurodegenerative disease caused by prions, similar to bovine spongiform encephalopathy (mad cow disease). Prions are infectious proteins that trigger abnormal protein folding in normal proteins, especially in the central nervous system.  CWD affects cervids such as deer, elk, moose, caribou, and reindeer. 

CWD was first identified in 1967 in Colorado. It has now been found in cervids living in Canada, Finland, Norway, Finland, South Korea, Sweden, and 35 states within the United States.

Prions replicate in the lymphoreticular system and then spread to the peripheral nervous system and the brain.Studies of cervids infected with CWD prions have detected prions in blood, body fluids, excreta, lymphoid tissues, muscles, peripheral nerves, and muscles. Infected animals shed CWD prions in body fluids, which can spread to other cervids through direct contact or through contact with contaminated soil, food, or water. 

Infectious chronic wasting disease prions have also been detected within fetal and reproductive  tissues of white tail deer. Female deer (does) with CWD can transmit the disease in utero to their offspring. Fawns can be infected with CWD at birth and may be infectious to other animals much, much earlier—even if they look healthy. Fawns often travel outside their family unit when trying to establish their own home range. If they are infected, they can transmit CWD to susceptible deer outside of their regular family group. 

Once introduced into an area or farm, CWD prions are highly contagious and can spread quickly. More than a year might pass before an infected animal develops symptoms which include drastic weight loss (wasting), stumbling, listlessness and other neurologic symptoms. CWD is fatal and there are no treatments or vaccines.

CWD prions have been detected in raw, cooked (grilled and boiled), and cured meat from infected elk. Grilling meat to medium-well substantially increased detection of prions. Heat disrupts tissues and releases prions trapped within them.

So far, CWD has not been detected in humans. However, there is a potential risk of human exposure to small numbers of prions through handling and consuming infected cervids.

References

Osterholm MT, Anderson CJ, Zabel MD, et al. Chronic Wasting Disease in Cervids: Implications for Prion Transmission to Humans and Other Animal Speciesexternal icon . MBio.2019 Jul 23;10(4). pii: e01091-19. doi: 10.1128/mBio.01091-19

Centers for Disease Control and Prevention, Chronic Wasting Disease, https://www.cdc.gov/prions/cwd/index.html

Van Beusekom, M. CWD prions found in moose, deer, reindeer muscles in Norway, highlighting potential risk to people. cidrap.umn.edu, January 14, 2025

Benavente R, Brydon F, Bravo-Risi F, Soto P, Reed JH, Lockwood M, et al. Detection of chronic wasting disease prions in raw, processed, and cooked elk meat, Texas, USA. Emerg Infect Dis. 2025 Feb [date cited]. https://doi.org/10.3201/eid3102.240906

Sandoval, A.M., Nalls, A.V., McNulty, E.E. et al. Vertical transmission of chronic wasting disease in free-ranging white-tailed deer populations. Sci Rep 15, 28553 (2025). https://doi.org/10.1038/s41598-025-12727-8