More About CWD

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CWD is the most significant threat to the future of healthy deer populations, deer hunting, and the hunting industry that we have ever encountered. It is a neurological disease that affects deer, elk, reindeer and moose.  CWD is an always fatal brain disease that affects members of the deer family (cervids) and is caused by prions (misshaped proteins) that create holes in the brain and eventually lead to death. There is currently no vaccine or treatment. Once a deer is infected with CWD, it may take up to 24 months to show clinical signs.

CWD is highly contagious, and the infectious agent known as prions may be passed in feces, urine, blood, saliva and semen. Recent research suggests that infected prions can also bind to soils and vegetation where it can be later taken up by animals. Experts believe prions can remain in the environment for several years, if not decades, so other animals can contract the disease even after an infected animal has died. There is no evidence that CWD can be transmitted to people despite thorough attempts to find a link to similar human diseases, such as Creutzfeldt-Jakob disease and Alzheimer’s disease.

CWD is currently known to exist in 26 states, as well as three Canadian provinces, Finland, Norway, and South Korea. Some areas in the U.S. have documented a nearly 50 percent prevalence rate. State wildlife agencies are increasing monitoring and surveillance, which is coming at the expense of other important wildlife programs due to a lack of funding to address the disease.

CWD has caused declines in deer populations in areas where CWD prevalence (the percentage of animals infected) is high. For example, in one area of Wyoming where CWD prevalence is currently greater than 35 percent, the mule deer population dropped from more than 14,000 in 2001 to approximately 6,000 in 2018. In another area of Wisconsin where 55 percent of adult male white-tailed deer are infected with CWD, research showed that 75 percent of infected deer died within the first year; three times the rate of uninfected deer.

CWD is an unprecedented threat to healthy deer herds. Unlike other known or visible diseases though, CWD does not kill large amounts of deer at the same time, and affected deer often don’t show signs or symptoms until death is near. These factors, in addition to other communication and non-scientific-based reasoning from vocal groups and individuals, can leave hunters and members of the public confused, or without a sense of urgency of what’s at stake.


To learn more about the science of CWD, read up-to-date news on the disease, and view the latest listing of infected areas, please visit these helpful resources:



The mission of the CWD Alliance is to promote responsible and accurate communications regarding CWD, and to support strategies that effectively control CWD to minimize its impact on wild, free-ranging cervids including deer, elk, and moose.



The USGS National Wildlife Health Center is the only national center dedicated to wildlife disease detection, control, and prevention in the United States. Its mission is to advance wildlife health science for the benefit of animals, humans, and the environment.


USGS distribution of chronic wasting disease in North America.




The Pennsylvania Wildlife Futures Program, a science-based, wildlife health program serves to increase disease surveillance, management and research to better protect wildlife across the Commonwealth.