Chronic Wasting Disease (CWD) is a fatal neurological disease impacting deer, elk, and moose across North America and in some other countries. While no human cases have been confirmed, public health agencies advise caution regarding the consumption of meat from affected animals. Understanding this disease and its implications is important.
Understanding Chronic Wasting Disease
Chronic Wasting Disease is a type of prion disease, similar to Bovine Spongiform Encephalopathy (BSE) in cattle or scrapie in sheep. Prions are misfolded proteins that cause normal proteins to also misfold, leading to the accumulation of abnormal proteins in the brain and spinal cord, resulting in neurodegeneration. CWD spreads among cervids through direct contact with infected animals or indirectly via contaminated bodily fluids like saliva, urine, and feces. Prions are durable and can remain infectious in the environment for many years, contaminating soil, water, and plants, posing a long-term transmission risk.
Implications for Human Health
No confirmed evidence of CWD transmission to humans exists. However, public health organizations, such as the Centers for Disease Control and Prevention (CDC), recommend against consuming meat from CWD-infected animals as a precautionary measure due to the theoretical risk of prion diseases crossing species barriers.
A “species barrier” is the natural resistance of one species to prions from another, often due to protein structure differences. While this barrier generally prevents cross-species transmission, experimental studies show CWD can transmit to non-human primates, like squirrel monkeys and macaques, when they consume infected deer or elk brain tissue.
Recent research using human cerebral organoids, laboratory models of human brain tissue, suggests a strong species barrier to CWD prions, as they did not become infected even with direct exposure. However, the long incubation period of prion diseases means potential human cases could take decades to manifest, requiring ongoing vigilance. Prions are not destroyed by standard cooking temperatures.
Recognizing and Testing for CWD
Recognizing Chronic Wasting Disease in live deer is challenging, as symptoms often appear only in late stages. Common clinical signs include:
Drastic weight loss
Decreased interaction with other animals
Listlessness
Lack of fear of humans
Excessive salivation
Increased thirst and urination
Stumbling
Drooping ears and teeth grinding
These signs are not exclusive to CWD, making definitive diagnosis difficult based on observation alone. Laboratory testing is necessary for a confirmed diagnosis, typically involving post-mortem examination of specific tissues.
Diagnostic tests commonly analyze tissues from the medial retropharyngeal lymph nodes or the obex region of the brain stem. State wildlife agencies or university diagnostic laboratories perform these specialized tests. Animals can appear healthy for months to years after infection, shedding prions into the environment and complicating detection in the wild.
Recommendations for Hunters
Hunters play a significant role in CWD surveillance and prevention. Avoid consuming meat from any deer that appears sick or tests positive for CWD. When field dressing or handling harvested carcasses, wear latex or rubber gloves.
Minimize contact with high-risk tissues, which concentrate prions:
Brain
Spinal cord
Eyes
Spleen
Tonsils
Lymph nodes
Proper disposal of these tissues and the entire carcass is important to prevent environmental contamination. Recommended disposal methods include burial on the harvest site, deep enough to deter scavengers, or disposal in approved, lined landfills.
Avoid disposing of carcasses in waterways or attempting to destroy them by burning, as prions are resistant to these methods and can spread.
Check local and state wildlife agency regulations for specific guidance on CWD surveillance, testing, and carcass disposal protocols in your hunting area. If hunting in a CWD-present area, consider having your harvested deer tested and wait for results before consuming the meat. Processing deer individually can help prevent cross-contamination.