What Is Zombie Deer Disease (Chronic Wasting Disease)?

Zombie deer disease, also known as chronic wasting disease, is an infectious condition that primarily occurs in deer and elk. The infection is related to mad cow disease (bovine spongiform encephalopathy), and it can be present in animals for at least one year before symptoms develop. There is no cure for the disease, and the condition is always fatal. Some animals die without ever having displayed any symptoms, and others experience rapid weight loss, lethargy, coordination difficulties, and confusion. As of 2019, twenty-four states in the United States and two Canadian provinces have reported cases of chronic wasting disease in free-range deer and elk.

Some of the major facts about this condition are outlined below.

Basic Definition

Chronic wasting disease is a progressive neurodegenerative disease spread by prions. Prions are infectious proteins that act as transmission vehicles for spongiform encephalopathies, including zombie deer disease and mad cow disease. Scientists first identified zombie deer disease in the 1960s, and the condition leads to symptoms that resemble dementia, ultimately resulting in death. The disease is spreading among wild deer populations, and it is also increasing in captive populations of deer, elk, and reindeer. Experts believe the increases are largely due to the ways in which humans trade hoofed mammals and deer. In addition to deer, elk, and reindeer, the condition can also infect moose. The fact that zombie deer disease is spread by prions is one of the reasons it is always fatal. Unlike bacteria and viruses, prions cannot be killed, and this makes treatment very difficult.

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Where It Occurs

Currently, experts have identified zombie deer disease in free-range deer populations in twenty-four states and two Canadian provinces. In the United States, Western states such as Wyoming, Montana, Colorado, and Utah have a particularly high prevalence of this condition, and it has been reported in Eastern states such as Pennsylvania and New York too. The disease can only be diagnosed by testing brain tissue after an animal's death, so current methods will only indicate where the disease was in the recent past, not necessarily everywhere it might be at any given moment. Since free-range deer often travel forty miles or more, infected animals could spread the disease in their feces and urine, and any disease transmission that occurs in this way would not be picked up by existing tracking methods. In terms of other places where it occurs, zombie deer disease has also been identified in Norway and South Korea. Some outbreaks of chronic wasting disease have been traced to holiday petting zoos; reindeer are often transported to other countries for these.

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How Humans Are Affected

In terms of how humans are affected, no cases of zombie deer disease have yet been diagnosed in humans. However, scientists believe the disease could be transmitted to humans, just as mad cow disease and certain avian and swine flu strains have been, and they are currently studying potential transmission routes to try to destroy these. Animal studies conducted in squirrel monkeys and rats modified with human genes showed zombie deer disease was capable of being transmitted to these particular animals. In another animal study, macaque monkeys were fed meat infected with the disease, and the monkeys then contracted chronic wasting disease themselves. Cellular studies in Petri dishes have shown the prions associated with chronic wasting disease can infect human cells, and experiments are currently being conducted on environmental samples such as rocks or wood covered with infected prions. When placed in cages with hamsters, the hamsters have developed chronic wasting disease. Although these animal and cellular studies raise concerns about the potential for transmission to humans, more research is needed, and some contradictory evidence has emerged. In 2005, a group of individuals ate venison exposed to chronic wasting disease, and scientists have been tracking their health since that time. So far, no one in the group has developed any symptoms associated with chronic wasting disease. Scientists believe the disease could still be incubating in their bodies, and it is also possible they might have been exposed to a mild version of the disease or the prions could not infiltrate their cells for some reason.

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Treatment Options

Currently, no curative treatment options exist for chronic wasting disease, and scientists can only recommend practices that could contain the disease in the animal population. However, containment can be very difficult since tests for the condition can only be done after an animal has died, and results can take up to two weeks. Currently, treatment options would focus on treating the symptoms instead of attempting to cure the disease. If the disease did transfer to humans, patients would be given supportive care such as oxygen therapy, breathing assistance, anticonvulsants, and intravenous fluids. Scientists hope one day a vaccine or an oral treatment may be available for both animal and human use. Researchers are also looking into the development of a test that could rapidly identify whether a piece of deer meat is infected with zombie deer disease. This would help hunters protect themselves and make an informed choice about whether to eat the meat of a particular animal.

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How To Prevent It

Since chronic wasting disease is fatal and is increasingly prevalent in deer, doctors are focused on ways to protect hunters and other individuals who interact with deer and wild game. In terms of how to prevent it, experts advise that hunters have any deer they kill tested for chronic wasting disease. If a deer appears to be stumbling or otherwise acting abnormally, contact with the animal should be avoided, and any meat from them should not be handled or eaten. The brain and spinal cord of a deer should not be handled or cut through, and individuals should refrain from eating lymph nodes, eyes, spleen, or tonsils from deer. Gloves are essential when handling deer meat, and contact with deer feces and urine is not recommended. Individuals who see deer behaving strangely should contact their local health or wildlife department.