Chronic Wasting Disease

What is CWD?

Chronic wasting disease is a fatal prion-based disease that affects mule deer, white-tailed deer, elk, moose, and caribou. Prion diseases are a family of progressive neurodegenerative disorders that affect both humans and animals. The abnormal folding of prion proteins leads to brain damage and a number of behavioral symptoms. CWD infection can occur through either direct contact with an infected animal or indirect contact with a contaminated surface. Unfortunately, the prion agent can remain viable and infectious in the environment (e.g. in the soil, on leaves or other surfaces) for many years. Once established in an area, CWD is nearly impossible to eradicate.

Is CWD a risk to humans?

To date, there have been no reported cases of CWD infection in humans. However, studies suggest CWD poses a risk to non-human primates, such as macaques, that eat meat from CWD-infected animals or come in contact with brain or bodily fluids from infected deer or elk. These studies raise concerns that there may also be a risk to humans. People should avoid exposure to animals exhibiting unusual behavior in areas where CWD is suspected to occur.  Public health experts, including the CDC, recommend that people avoid consuming meat from animals suspected or confirmed to be CWD-positive.

How does CWD impact wildlife?

Currently, there are no vaccines or treatments for CWD. No immunity, recovery, or resistance to infection has been documented in any of the affected species. Left unmanaged, CWD is believed to be capable of severely depressing or even completely eliminating populations of susceptible species. Intensive management can sustain populations, however, through site-specific, intensive culling and general population suppression to reduce the prevalence of the disease. In either case, population declines are likely to occur where CWD is suspected or confirmed.

How is CWD detected?

Because of CWD’s sometimes low relative prevalence and prolonged latent period, detection remains difficult. Symptoms of CWD, which may take over a year to develop, include drastic weight loss (wasting), stumbling, listlessness, and other neurologic symptoms. Infected animals can shed the prion before the onset of clinical signs, sometimes for months, and some infected animals may exhibit no symptoms at all. Tissues with the highest concentration of infectious material include the brain, spinal cord, eyes, lymph nodes, and tonsils. In general, clinical testing of an animal’s lymph nodes is used to verify CWD in an animal. As a result, states where CWD is believed to be present have generally expanded hunting opportunity as a method to obtain high numbers of samples for testing. However, hunters are strongly discouraged from consuming meat from CWD-positive animals.

How is CWD managed?

While eradication of CWD is generally impossible, the spread and intensity of infections can be managed through intensive culling and general population suppression to reduce disease prevalence. These steps also provide wildlife managers with the samples needed to monitor infection rates and detect the spread of CWD into new areas.

To enhance sampling efforts, in Fall 2021 the state of Idaho authorized additional deer tags for state-licensed hunters within an enhanced surveillance area including the greater Riggins-Grangeville-Elk City area. Recent data indicate a CWD prevalence rate of 1.2% for mule deer and 3.3% for white-tailed deer in Idaho’s GMU 14. While hunters have been encouraged to harvest deer in this area to enhance surveillance efforts, please be aware that all animals harvested within this area should be tested, and animals that test positive should not be consumed.

Maps of regional CWD Enhanced Surveillance Zones are linked below. More information can be found at WDFW’s website and IDFG’s website.