“Zombie Deer” Warnings Have Been Issued By The CDC — Here's What That Means

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As if the world weren’t enough of a post-apocalyptic horror movie, the CDC has issued a warning about “zombie deer”. Cool, cool, cool — we’re just throwing the word “zombie” around now. A little on the nose, but I guess it’s fine.

To clarify, “zombie deer” is the very chill nickname non-scientists have given to chronic wasting disease. Chronic Wasting Disease (CWD or, if you’re feeling dramatic “zombie disease”) is a type of prion disease (a category of neurodegenerative disorders) that that can affect deer, elk, reindeer, sika deer, and moose. Its symptoms include ”drastic weight loss (wasting), stumbling, listlessness and other neurologic symptoms.” It also makes infected animals, like deer, less afraid of approaching humans. Thus, the “zombie deer.”

Starting in January 2019, the CDC warned that cases of CWD had been reported in at least 24 states across the U.S. and two provinces in Canada. Free-ranging deer, elk, and moose have all been cited in reports of infection. Again, these “zombie deer” are not eating other deer or chomping down on humans. Nor do they appear as ghost-like entities, haunting backyards and highways. They’re just more lethargic, likely skinnier, and may seem bolder in their attempts to interact with humans.

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Per the CDC, it may take over a year for an infected animal to show signs of the disease, and some infected animals “may die without ever developing the disease.” There are currently no vaccines or treatments for CWD and it is fatal to animals like deer.

According to the CDC, there have been no reported cases of humans infected with CWD to date. So, there isn’t too much to be worried about (...she said ominously). However, some studies suggest the disease may pose a risk to other meat-eating primates. Thus, there is concern about the risk of coming into contact with CWD-infected animals may pose to humans.

The current warning is primarily to keep hunters and anyone who eats deer meat from ingesting or handling potentially infected meat. Per the CDC’s website, “the World Health Organization has recommended that it is important to keep the agents of all known prion diseases from entering the human food chain.”

Experts advise not to go near any venison that seems sick or is found dead or handle any animal meat in infected areas.

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The CDC’s map of infected states looks a bit dramatic if we’re talking “zombie apocalypse.” If we’re talking actual, real science, it should still be taken seriously. Just not “get a bunker ready” serious.

Wyoming has more infected counties than not, per the CDC’s map. Colorado, Nebraska, western Kansas, southern Wisconsin, and northern Illinois each have a significant number of infected counties as well. CWD has spread as far east as Pennsylvania (five counties have reported infected animals) and one county in New York.

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If it’s any comfort, “zombie-like” diseases are nothing new to the animal kingdom. You’ve likely heard tale of the parasite that makes mice love cats. Toxoplasma gondii is a parasite that reproduces in the intestines of a cat and is expelled in the cat’s feces. If mice consume food or water contaminated with that infected feces, they become infected with the parasite. The parasite infects the rodent’s brain, hence the “zombie” reputation.

Infected mice lose their natural instinct to fear cats and avoid the smell of cat urine. Because the parasite resides in the rodent’s amygdala, the fear- and emotion-processing part of the brain, infected rodents are essentially pre-programmed to not only not fear cats but become attracted to them. As Smithsonian magazine explains, “When male rats infected with Toxoplasma smell cat urine, they have altered activity in the fear part of the brain as well as increased activity in the part of the brain that is responsible for sexual behavior and normally activates after exposure to a female rat.” In non-scientific terms, the parasite makes them horny for death.

Like with the recent “zombie deer,” humans contracting the infection and life-threatening symptoms are slim. (AKA your cat isn’t making you crazy and we’re not all going to get bitten by zombie deer.) However, in the case of the CWD outbreak, it’s best to heed the advice of the CDC and avoid direct contact with potentially infected animals.