Zombie Deer Disease and the Concern for Human Infection

What is zombie deer disease?

Zombie deer disease, also known as chronic wasting disease (CWD), is a neurological disorder that causes progressive degeneration of the brain in cervids, a group of animals that includes deer, elk, reindeer, sika deer and moose. The disease is caused by misfolded proteins called prions, which can induce normal proteins in the brain to misfold as well, leading to brain damage and death.

The origin of the term “zombie deer” is unclear, but it may refer to the symptoms that infected animals exhibit, such as drooling, stumbling, aggression, weight loss and a vacant stare. The disease has a long incubation period of about a year, and there is no treatment or vaccine available.

How does zombie deer disease spread?

Zombie deer disease spreads through direct or indirect contact with bodily fluids of infected animals, such as saliva, urine, blood or feces. Prions can also persist in the environment for years, contaminating soil, plants and water sources. The disease can affect both wild and captive populations of cervids.

Where is zombie deer disease found?

Zombie deer disease was first discovered in Colorado in 1967. Since then, it has been detected in at least 31 states in the US and three provinces in Canada, as well as in Norway, Finland, Sweden and South Korea. In November 2023, a deer carcass in Yellowstone National Park tested positive for CWD, raising alarm among scientists and conservationists.

What is the risk of human infection?

While there is no conclusive evidence that zombie deer disease can infect humans, there is a possibility that it could cross the species barrier through the consumption of infected meat. Prion diseases have shown the ability to jump from animals to humans before, such as mad cow disease in cattle and Creutzfeldt-Jakob disease (CJD) in humans. The outbreak of mad cow disease in Britain resulted in the slaughter of millions of cattle and led to 178 human deaths attributed to CJD since 1995.

Studies have shown that prions responsible for CWD can infect and propagate within human cells under laboratory conditions. Reports suggest that between 7,000 to 15,000 CWD-infected animals were consumed annually by humans in 2017, with projections indicating a 20% annual increase. In regions where CWD prevalence is high, such as Wisconsin, thousands of people may have unwittingly consumed meat from infected deer.

However, detecting and diagnosing prion diseases in humans is challenging due to the lack of immune response and reliable tests for live animals or humans . Therefore, the true extent of human exposure and infection remains unknown.

How disease can be prevented?

The World Health Organization advises against allowing animals infected with known prion diseases into the human food chain. Hunters are advised to avoid shooting or handling animals that appear sick or abnormal, and to wear gloves and use proper tools when field dressing carcasses. They are also encouraged to test their harvested animals for CWD before consuming them.

CWD can be prevented by reducing the contact and transmission of prions among cervids and their environment. This can be done by limiting the movement and concentration of cervids, banning the use of cervid urine as a hunting lure, disposing of carcasses properly, and decontaminating equipment and clothing that may have come into contact with prions.

Zombie deer disease is a serious threat to wildlife health and conservation. It also poses a potential risk to human health. More research is needed to understand the nature and extent of this risk, and to develop effective strategies to prevent and control this emerging prion disease.

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