Chronic Wasting Disease (CWD) is a growing concern for hunters and consumers of venison across North America. As deer and elk populations are increasingly affected by this fatal neurological condition, questions about the potential risk to human health have become common. Understanding the science behind CWD is essential for addressing the central question: Is there a risk to humans from eating infected deer meat? This article explores the current scientific understanding of CWD transmission and provides practical guidance for minimizing potential risk.
What Chronic Wasting Disease Is
Chronic Wasting Disease is a progressive, fatal neurological illness affecting cervids, including deer, elk, and moose. It is classified as a transmissible spongiform encephalopathy (TSE), characterized by damage to the brain and nervous system tissue. The disease is caused by infectious proteins called prions, which are misfolded versions of normal proteins found in the body.
Prions do not contain genetic material and are highly resistant to conventional sterilization methods like heat or radiation. Once an animal is infected, these abnormal prions cause normal cellular proteins to misfold, leading to a chain reaction that accumulates in the brain. Symptoms, which take months or years to appear, include drastic weight loss, behavioral changes, excessive salivation, and stumbling. This is why the condition is often referred to as “wasting.” (5 sentences)
First identified in captive mule deer in Colorado in the late 1960s, CWD has since spread geographically across the United States and Canada. The disease is now present in at least 32 U.S. states and three Canadian provinces. Transmission occurs through direct animal contact or indirectly via environmental contamination from saliva, urine, or feces, as prions can persist in soil for years, making it a widespread issue for wildlife management. (4 sentences)
Prions and the Human Species Barrier
The primary question for consumers is whether CWD prions can cross the species barrier and cause illness in humans. Public health agencies currently report no confirmed evidence of CWD naturally infecting humans. The concept of a “species barrier” describes the natural resistance that prevents prions from one species, such as deer, from efficiently infecting another, like humans.
This barrier is not absolute, as demonstrated by Bovine Spongiform Encephalopathy (BSE), or “Mad Cow Disease,” which crossed from cattle to humans, causing variant Creutzfeldt-Jakob Disease (vCJD). CWD prions must overcome significant molecular hurdles to infect human cells, a difficulty that provides a degree of protection. However, the long incubation period for prion diseases, which can sometimes last for decades, means surveillance must continue to monitor for any potential transmission. (4 sentences)
Scientific investigations have used various animal models to test the strength of this barrier. Studies involving cynomolgus macaque monkeys, a species genetically similar to humans, showed no clinical, pathological, or biochemical evidence of CWD transmission. This lack of transmission occurred even after up to 13 years of exposure through oral consumption or direct brain inoculation. These results suggest a robust barrier to CWD transmission for humans. (4 sentences)
However, other experimental models have shown mixed results, highlighting the need for caution in public health recommendations. Squirrel monkeys, for instance, proved highly susceptible to CWD prions through both oral and brain exposure. Additionally, transgenic mice engineered to express human prion protein showed resistance to CWD infection. Conversely, mice with a specific chimeric human/elk protein were highly susceptible to the disease. These laboratory findings indicate that while a strong barrier exists, the potential for an adaptation or a breakdown of that barrier cannot be entirely dismissed. (5 sentences)
Minimizing Risk When Handling Venison
Due to the scientific uncertainty surrounding the species barrier, public health officials recommend specific actions to minimize potential exposure to CWD prions. The Centers for Disease Control and Prevention (CDC) advises against consuming meat from any animal known to be infected with CWD. In CWD-endemic areas, the most effective action is to have the animal tested before consuming the meat. (3 sentences)
If an animal is harvested where CWD has been detected, the carcass should be isolated. The meat should not be processed or eaten until a negative test result is returned. If the test is positive, the entire carcass must be disposed of according to local regulations. If test results are not immediately available, the venison should be frozen, as freezing does not compromise the subsequent testing process. (4 sentences)
During field dressing, hunters should wear latex or rubber gloves and minimize contact with high-risk tissues, which concentrate prions at higher levels. These tissues include the brain, spinal cord, eyes, lymph nodes, and spleen. When processing the meat, it is best practice to completely bone out the muscle tissue. Hunters should also avoid sawing through the spinal column or cutting through the brain. (4 sentences)
Prions are not destroyed by typical cooking temperatures, meaning cooking venison to a high temperature does not make meat from an infected animal safe to eat. All equipment, including knives and surfaces, should be thoroughly cleaned after use. Afterward, soak the equipment in a 50% bleach-and-water solution for at least an hour to help inactivate any residual prions. (3 sentences)