Chronic Wasting Disease (CWD) is a serious neurological disorder afflicting cervids (deer, elk, and moose). This disease has been found in free-ranging and captive populations across North America and in other countries, leading to widespread concern among hunters and the public. The central question remains whether this fatal animal disease can cross the species barrier and threaten human health. This article explores the nature of CWD, the current scientific understanding of its human risk, and the practical precautions individuals can take.
Understanding Chronic Wasting Disease
Chronic Wasting Disease belongs to the Transmissible Spongiform Encephalopathies (TSEs), which also includes scrapie in sheep and bovine spongiform encephalopathy (BSE) in cattle. The cause of CWD is not a virus or bacterium, but an infectious, misfolded protein known as a prion. These abnormal prions compel normal cellular proteins in the host’s brain and nervous tissue to misfold, leading to progressive damage.
The disease has a long incubation period before an infected animal shows observable signs. Symptoms in cervids typically include drastic weight loss, stumbling, listlessness, excessive salivation, and behavioral changes, ultimately leading to death. CWD spreads among animals through direct contact with bodily fluids like saliva, urine, and feces, or indirectly through environmental contamination, as prions can persist in soil for years.
Current Scientific Assessment of Human Risk
Public health officials consider the risk of CWD transmission to humans to be theoretical, as no confirmed cases of human infection have been reported. The primary defense against cross-species transmission is the “species barrier,” a biological hurdle that makes it difficult for prions from one species to corrupt the normal proteins of another. Research has focused on testing the integrity of this barrier.
Laboratory studies using non-human primates, such as squirrel monkeys and cynomolgus macaques, have shown that CWD prions can be transmitted under specific experimental conditions, including oral consumption of infected meat. These results raise concerns about the potential for human infection, especially since the consumption of infected meat is believed to be the most likely route of exposure if a spillover were to occur. However, a recent National Institutes of Health study using human cerebral organoids—small, lab-grown models of the human brain—demonstrated a strong resistance to CWD prions from various deer and elk sources.
This finding supports the presence of a strong species barrier, but experts caution that the risk is not zero, particularly since prion strains can evolve over time. Because of the nature of prion diseases, which can have incubation periods spanning decades, health organizations like the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) strongly recommend keeping the infectious agent out of the human food chain. The consumption of meat from any CWD-positive animal is strongly discouraged.
Essential Safety Measures for Hunters and Consumers
Individuals who hunt or consume venison must adopt specific precautions to minimize any hypothetical exposure to CWD prions.
- Never shoot, handle, or consume an animal that appears sick, is acting abnormally, or was found dead.
- Check with state wildlife agencies to determine if testing is required, and strongly consider testing the animal before consumption.
- When field dressing or processing, wear latex or rubber gloves and minimize contact with high-risk tissues (brain, spinal cord, spleen, tonsils, and lymph nodes).
- Bone out the meat (removing it from the bone and spinal column) and avoid sawing through bone or cutting through the central nervous system tissue.
- Tools and work surfaces should be thoroughly cleaned and disinfected using a solution of 50% household chlorine bleach and water for at least an hour.
- If using a commercial processor, request that your animal be processed individually to prevent cross-contamination with meat from other animals.
Ongoing Surveillance and Research Efforts
The management of CWD involves efforts by public health and wildlife organizations to monitor the disease’s spread and assess any changing risk. State wildlife agencies and the United States Geological Survey (USGS) actively track the prevalence of CWD in cervid populations across North America. This surveillance informs management decisions, such as establishing CWD management zones and recommending specific testing protocols for hunters.
Researchers are working to develop more effective tools for detecting CWD in live animals and are investigating the role of scavengers in the disease’s ecology. Researchers are characterizing different CWD strains and how mutations might affect the species barrier and human risk level. Collaborative efforts, such as the CWD Data Warehouse, facilitate interagency data sharing to ensure surveillance planning is efficient and based on the best available science. The CDC and WHO continue to monitor for any atypical human prion cases that might signal a transmission event.