Reportable Disease of the Month: Chronic Wasting Disease

board of animal health

Reportable Disease of the Month

Chronic Wasting Disease


Chronic Wasting Disease (CWD) is a neurodegenerative disease affecting deer, elk and moose (members of the Cervidae family) and is always fatal. Abnormally shaped infectious proteins called prions cause the disease and convert normal proteins into infectious ones, which eventually leads to the animal’s death. CWD was discovered in Colorado in the 1960’s and is found in the United States, Canada, and more recently, in Europe. It belongs to a group of diseases known as transmissible spongiform encephalopathies.


The disease is believed to be spread from one animal to another through direct contact and/or environmental contamination. Infectious prions can be spread via saliva, feces, blood, urine, and other bodily fluids. CWD and other prion diseases are difficult to control because, unlike bacteria and viruses, prions are resistant to inactivation by heat, freezing, ultraviolet light, and chemical disinfectants. Prions are also resilient in many environments and can remain infectious for extended periods of time.


Because CWD is a slow and progressive disease, signs of infection may take a long time to appear. Typical signs include behavioral changes, lack of coordination, stumbling, tremors, drooling, and weight loss. These are not the only symptoms and are not necessarily specific to CWD. Animals exhibiting these clinical signs often die within months.

It is confirmed by testing tissue samples from a dead animal’s central nervous system and/or lymph nodes. Tests, like immunohistochemistry, work by detecting antigens (prions) in those tissues. There is no treatment or vaccine for CWD. The disease is fatal for infected deer, elk or moose.

Human Risk

There has been no evidence that CWD has been transmitted to humans. In addition, CWD has not been identified domestic animals (including dogs and cats) or livestock other than deer or elk. However, in the laboratory, species barriers can be breached for many of the prion diseases including CWD. This means that a prion disease normally found in one species can be made to infect another species in a laboratory setting. For this reason, The Centers for Disease Control and Prevention (CDC) and the Minnesota Department of Health do not recommend that people consume meat from a CWD-infected animal, or from any animal that appears ill.


Preventing CWD starts with surveillance, monitoring, biosecurity and early detection. Farmed deer and elk, 6 months of age and older, must be tested for CWD if they die or are slaughtered. In Minnesota, tissue samples (brain stem and lymph nodes) are tested at the University of Minnesota Veterinary Diagnostic Laboratory in St. Paul. Deer and elk farms are also annually inspected by the Board and producers are required to report all deer or elk deaths and when animals are moved into or out of the herd. In the event of a positive test result for CWD, the Board will quarantine, depopulate and CWD-test the affected herd.

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