Chronic Wasting Disease (CWD) is a fatal neurological disorder affecting deer, elk, and moose (cervids). Detected in wild and captive populations across North America and other countries, the increasing geographic spread of CWD raises concerns for hunters and consumers of venison. Understanding the nature of this disease and the current scientific risk assessment is important for anyone who handles or eats cervid products.
Understanding Chronic Wasting Disease
CWD is a transmissible spongiform encephalopathy (TSE), a progressive and fatal neurological disorder. It is caused by an abnormally folded protein called a prion, not a virus or bacterium. These misfolded prions cause healthy proteins in the host’s brain and nervous system to also misfold, creating microscopic holes in the brain tissue. This process leads to characteristic neurological symptoms, including drastic weight loss, stumbling, listlessness, and behavioral changes.
The disease has a long incubation period, often taking months or years before an infected animal shows visible signs. During this silent phase, prions are shed into the environment through saliva, urine, and feces, contributing to high transmissibility among cervids. CWD is 100% fatal, and no treatments or vaccines are currently available. Since its identification in the late 1960s, the disease has expanded significantly across U.S. states and Canadian provinces.
The Current Status of Human Transmission Risk
There are currently no confirmed cases of CWD infection in humans, and no human neurological disease has been definitively linked to the consumption of infected venison. The primary barrier preventing transmission is the “species barrier,” which typically prevents prions from crossing from one species to another. However, the species barrier is not absolute, as evidenced by the transmission of Bovine Spongiform Encephalopathy (BSE, or “mad cow disease”) to humans, resulting in variant Creutzfeldt-Jakob Disease (vCJD). This historical event indicates that an animal prion disease can potentially jump to humans under sufficient exposure.
Epidemiological surveillance is ongoing, with health officials monitoring human prion diseases like Creutzfeldt-Jakob Disease (CJD) to detect any atypical cases linked to CWD exposure. While some early reports of CJD in hunters raised concern, subsequent investigations found no strong evidence of a causal connection. The overall consensus is that the risk of infection to humans is extremely small, but avoiding exposure to the infectious agent remains a public health recommendation.
Identifying High-Risk Tissues
Prions concentrate in specific tissues rather than distributing evenly throughout the body of an infected animal. The highest concentrations of infectious prions are found in the central nervous system (CNS) and certain parts of the lymphatic system. Tissues that should be avoided regardless of an animal’s testing status include the brain, spinal cord, eyes, tonsils, spleen, and lymph nodes.
Muscle meat, which is the primary venison consumed, is considered low-risk because it contains significantly lower levels of prions. The main danger to muscle meat comes from cross-contamination during the field dressing and processing of the animal, especially if cutting tools come into contact with the spine or brain. Careful handling is necessary to ensure the edible muscle is not contaminated with nervous or lymphatic material.
Guidelines for Safe Consumption and Handling
Hunters and consumers in CWD-endemic areas should take proactive steps to minimize any theoretical risk. A primary recommendation from the Centers for Disease Control and Prevention (CDC) is to have the harvested animal tested for CWD before consuming the meat. If an animal tests positive for the disease, the meat should not be eaten or distributed.
Safe Handling Practices
When processing cervids, follow these guidelines to reduce the risk of exposure:
- Wear latex or rubber gloves when field dressing to prevent direct contact with tissues and fluids.
- Avoid sawing through bones, particularly the spine or skull, and minimize handling of the brain and spinal cord, as these tissues harbor the highest concentration of prions.
- “Bone out” the meat by separating the muscle from the bone without sawing, which reduces the chance of contamination from the spinal column.
- Thoroughly clean all processing tools and surfaces, as prions are resistant to standard cooking temperatures and household cleaning products.
To inactivate prions on equipment, a solution of 40% to 50% household bleach mixed with water can be used for a minimum of five minutes, but all organic material must first be removed. If using a commercial processor, request that your animal be processed individually to avoid cross-contamination.