Chronic Wasting Disease
Understanding the Impact on Our Local Deer Population
Idaho Department of Fish and Game (IDFG) provided an important update on Chronic Wasting Disease (CWD), a serious and fatal condition affecting our local deer population and the deer population elsewhere. Similar to other Transmissible Spongiform Encephalopathies (TSEs), CWD is caused by abnormal prion proteins that disrupt normal neurological functions in infected animals.
Under normal circumstances, prion proteins in the body are broken down and recycled. However, in CWD-infected animals, these proteins become misfolded and resist degradation. Over time, the accumulation of these abnormal prions leads to severe brain degeneration, resulting in motor function impairment and diminished ability to respond to environmental threats.
CWD spreads primarily through direct contact with infected bodily fluids such as saliva, urine, and feces, and through environmental contamination. Bucks are more likely to contribute to the spread due to their high mobility and frequent contact with other deer during the breeding season. There is also emerging evidence that prions may be transmitted from infected does to their offspring, though further research is needed to confirm the mechanisms of maternal transmission.
Once contracted, CWD has an incubation period of 18 to 24 months, with most infected animals not displaying symptoms until around 16 months post-infection. The disease is always fatal, and no treatment or vaccine currently exists.
While there are no confirmed cases of CWD transmission to humans, the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) recommend not consuming meat from CWD-positive animals as a precaution. Notably, Creutzfeldt-Jakob Disease (CJD) (the TSE that affects humans) remains rare, with an incidence rate of about 1 in 1,000,000 worldwide. To date, there is no evidence linking human cases of CJD to consumption of CWD-positive venison.
Locally, Boundary County reported its first CWD-positive case in July 2024—a deceased deer found on private land. In response, Idaho Fish and Game launched a comprehensive surveillance effort, establishing a CWD Management Zone and implementing restrictions on carcass transport. Mandatory sampling for hunters was also introduced.
By the end of the 2024 hunting season, approximately 1,000 deer samples were collected within the management zone. Of those, only three tested positive for CWD. These cases were dispersed throughout Boundary County with no clear geographic pattern and were in addition to earlier detections during summer surveillance and special hunts.
The long-term presence of CWD poses significant challenges. Prions can remain viable in the environment for years, persisting in soil, vegetation, and water. As such, even with reduced deer populations, CWD can continue to spread.
Effective management strategies focus on reducing deer density and adjusting population demographics, such as altering buck-to-doe ratios, to slow the rate of transmission and increase the likelihood of harvesting healthy animals. Without intervention, however, the disease will continue to impact the region’s cervid populations for the foreseeable future.
For more information go to idfg.idaho.gov