The Myth of the Zombie Deer

EdenBlog, Education

Deer in a forest

By Dale Barks, CPAWS Field Technician 

Humans have an innate fascination with The Unknown. We love to imagine the unimaginable, to plan our way through a thousand-and-one different “what-if” scenarios. This is why TV shows like The Walking Dead are so popular in contemporary culture—the allure of imagining a world so familiar to us, yet at the same time completely unfamiliar, is a captivating mix of terrifying and tempting that enthrals the human imagination. This is also why, when social media becomes inundated with news reports, blogs, and personal posts about topics such as “Zombie Deer,” we are so easily swayed from the rationally-thinking, fact-checking people that we all claim to be, to become just another victim in the war against fake and sensationalized news. The mystery of a disease that destroys the minds of its victims, leaving them mere husks of their once-healthy selves to roam mindlessly around the world, both horrifies and fascinates us. It resonates with the desire inside many of us to believe that there is something else out there, some aspect of life that our rational minds cannot explain, that defies the mundanity of our normal day-to-day existence. And so it is with great regret and personal turmoil that I inform you that there is no such thing as a “Zombie Deer.”

I’m sure many of you have seen these posts. Headlines such as “Zombie Deer Disease Has Spread to 2 Provinces and 24 States” or “Zombie Disease Killing Deer Could Spread to Humans” are running rampant around the internet. Some of the more reliable ones quote scientific papers, others simply speculate wildly about the impacts of such a disease without so much as a basic understanding of how it works or what it actually is. Still others  include gory images of animals they claim have been infected with this terrifying pathogen, but which, in reality, have absolutely nothing to do with the disease in question at all (one post in particular used photos of roadkill casualties, wolf-kills, and even perfectly-healthy-but-abnormally-tame deer to convince people of the horrors of this so-called ‘Zombie Disease’). Posts and news reports like this do little but contribute to mass hysteria and misunderstanding among people and can even cause significant damage to conservation efforts and wildlife itself. So, without further ado, here is the truth of the disease that has experienced such an explosion of popularity over the past week.

First, so that I can quit using the ridiculous term “Zombie Disease,” let me point out that its real name is Chronic Wasting Disease, or CWD. I realize that this is not really any less disturbing, but it is certainly more accurate. So from here on out, let’s call the disease by its real name. Next, to justify why my explanation of CWD may be slightly more complete than many of the other reports circulating around social media at the moment: I am a biologist (albeit a newly-minted one), who has had more experience dealing with the REAL disease than most people in North America. Now, this experience is not entirely by choice—I grew up on a farm that raised whitetail deer, and in 2007, our entire farm was put down because it had become infected by the wild population, within which CWD had already existed for a number of years. As a result, in a single day, I saw literally dozens of animals that were later confirmed to have the disease (and sadly, not one could be considered to be anything even remotely similar to a zombie). On top of that, I have written extensively about CWD ever since beginning my training as a biologist—apparently having an entire deer farm put down because of CWD when you are 13 years old can have a profound impact on one’s future interests (I am not the life of the party by any means, unless it is a party about discussing CWD. It rarely is). Through this writing, I have had the unique opportunity to meet with and learn from many of the world’s leading researchers of CWD and other similar diseases (and not one has ever used the term “Zombie Deer”). Finally, I have a database of 692 peer-reviewed papers saved on my computer, all pertaining to CWD and spanning from its discovery in 1967 to today. That is probably significantly more real information than many of these other hysteria-fueled reports have used.

The Basics

Here are some of the basics to keep in mind when reading about CWD online. Chronic Wasting Disease is a transmissible spongiform encephalopathy, or a TSE that affects deer species (whitetail, mule deer, elk, moose, caribou, etc). In simpler terms, it is a disease, capable of being spread between animals, that affects the brain by causing it to become ‘spongy’ as it degenerates. The disease itself is caused by a prion (not a “zombie virus” as many claim), which is a misfolded prion that causes other prions to misfold as it encounters them. As the prions accumulate in the victim’s brain and central nervous system, the deer loses body condition as the disease progresses, becoming underweight and experiencing behavioural changes that may cause infected individuals to leave the herd. Contrary to the tale being spun by many popular media outlets, CWD does not cause increased aggression in individuals, but rather causes the opposite—infected animals generally become listless and less aware of danger, likely leading to an early death by predation. A CWD-infected deer is not likely to attack a human or pet—if anything, it just won’t care that humans or dogs are nearby.

Unlike its cousin, BSE, CWD has never crossed the species barrier to infect humans. Although some articles claim that researchers are concerned that it will infect humans, these articles are significantly exaggerating the concerns of researchers. Yes, this is a viable concern, insofar as we need to be cautious because we can “never say never.” Some articles claim that “CWD has been shown to pass to nonhuman primates.” Again, this is true, but only partially—CWD has been shown to pass to some species, such as squirrel monkeys, but other species, such as macaques (an oft-used model for prion diseases due to their similarity to humans) have been repeatedly found to be resistant to the disease. Does this mean that we should throw caution to the wind and dismiss any risk that may exist? Of course not. Normal precautions such as avoiding eating or handling spinal tissue and fluid, brain tissue, etc should still be practiced, but let’s be honest: how many of us were really about to go gnaw on a deer head anyway? (If you put up your hand here, please contact your nearest health center: there may be no such thing as zombie deer, but I am very concerned for you). So, while there is always a risk that CWD could potentially pass to humans, it is not the immediate, pressing threat that many articles claim. Researchers are always concerned about “what-ifs” and “worst-case scenarios”; that doesn’t mean that the occurrence is likely (or even possible).

False Signs

Now to explain away some of the many false claims of ‘evidence’ of “zombie deer.”

  • Stamping of feet is not a sign of CWD. Animals that are snorting, stamping, or displaying any similar behaviour are not zombies about to attack, they are concerned deer that are trying to determine if someone or something is a threat from which they need to flee. A deer will often stamp on the ground to see if the person/pet that it sees will move in response. If so, the deer will generally turn tail and run away. Snorting has a similar affect. In fact, as deer with CWD often experience reduced situational awareness and threat-recognition, a severely-infected deer would actually be LESS likely to display this behaviour.
  • Similarly, videos or pictures of deer head-butting fences or trees are not illustrating behaviour of an infected individual, but rather are deer demonstrating typical rutting aggression. As hormones climb in the fall, male deer become more aggressive towards other deer, trees, fences, the deer-farmer who bottlefed them as a fawn… kind of like that friend who tries to impress a potential love-interest by becoming a jerk to the other friends in the group in an effort to make themselves look better. On a related note, pictures or videos of deer with bloody antlers and scraps of fuzzy skin hanging from their antlers are not showing a deer that just attacked someone, they are showing a deer that is in the process of shedding the protective layer that covers its antlers during the growing season.
  • A deer with black wart-like growths is also not suffering from CWD, as many claim. This is a common papilloma viral infection, and although it can look awful on some badly-infected individuals, it is generally not very harmful to the animal’s long-term health. The warts tend to dry up and fall off eventually. Again, warts are not one of the symptoms of CWD, they are simply due to a papilloma virus.
  • A tame deer is not necessarily a sick deer. Now, while the listlessness associated with CWD CAN cause a deer to appear tame, by the time the deer reaches this stage in the disease, it will be little more than skin and bones. So, a healthy-looking, tame deer is almost certainly just that—a tame deer. Deer are adaptable animals. They have learned that they are generally fairly safe in urban centers and often become very calm and tame as a result.
  • Pictures of deer with glowing eyes do not show zombie deer. Deer simply have reflective eyes when faced with a bright light in the night. That’s all there is to this one.
  • I can’t believe that this needs saying, but since I saw this picture in a post with over 100,000 shares, apparently it does: if you can see through the animal, it is not a zombie—it is dead. There is a picture circulating of a dead caribou, partially eaten by scavengers, that someone propped up in the snow alongside a highway as a joke. You can see right through the animal, because it is almost half-eaten. Sure, it may look like a White Walker’s horse from Game of Thrones, but it is just a wolf’s meal that some human decided to make a joke out of. Please, don’t fall for this one. This is just embarrassing.
  • Predators that eat infected deer do not become infected with CWD themselves, nor do they become more aggressive towards humans. Now, I don’t know if the people claiming otherwise are confusing CWD with rabies, or if they just enjoy making stuff up, but CWD is a deer-specific disease. Sure, some lab studies have shown that the odd other species can be forcibly infected (if injected directly into the brain with the infectious prion), but as a rule, CWD affects deer only. The only seed of truth here is that if predators consume an infected animal, they can carry the infectious prion in their stomach and deposit it in a new, previously prion-free area through their… um… waste. Those prions may eventually be picked up by another deer, and so the disease can be carried from place to place via predation. In other words, wolves and coyotes can act as vectors for the disease, but they can’t actually contract it themselves. And they certainly don’t become rabid through CWD. They only become rabid through… you know… rabies.

Chronic Wasting Disease is absolutely an issue of great concern. We are still learning about it, and we do not yet fully understand the threat it holds for deer populations. As far as has been discovered by researchers like Dr. Nick Haley, there are different levels of genetic resistance to the disease, however, the most-resistant genes are also often the rarest. It could be that resistant genetics will be naturally selected for in the long run, and that the disease may be naturally overcome in that way. It is also possible that CWD causes such a decline in deer populations that it impacts ecosystems on a larger scale, as deer are keystone species in many systems and have significant effects on trophic levels both above and below themselves (plants and predators). Consequently, loss of deer in an ecosystem would be a devastating blow to the ecology of a given area. In other words, CWD does pose a potential threat. In reality, we do not really understand just how significant a threat this is, or what the eventual impact of the disease will be. What we do know, however, is that it does not create “zombie deer.” The only thing creating zombie deer are the media and people who spread this misinformation to others. Thankfully, these zombies are only in our imagination, where they can’t pose any real threat.


Well, actually, the hysteria and misinformation that is buzzing around can cause significant damage—arguably almost as much as a herd of real zombie deer (not really, but you know, hyperbole is always fun to use). Seriously though, the hysteria is only contributing to the miseducation of vast numbers of people. As a result, it has the potential to significantly hinder conservation efforts, headed by those people who ACTUALLY understand the disease, in their efforts to combat the disease. It is really tough to convince people to protect an animal if the public belief is that deer are turning into violent zombies, attacking people and dogs, and transferring the disease to any predator that eats them. And that leads to the final victim of this hysteria—the deer themselves. As long as people are being misinformed about CWD, there is a high likelihood that people will kill deer that should not be killed. Just like every good zombie movie, once the hysteria strikes, every human is a potential zombie. And how do you make sure a potential zombie doesn’t attack you? You neutralize the threat. The last thing we want is a bunch of people, terrified of a monster that doesn’t exist, running around trying to neutralize a threat that isn’t there. So please, be careful about what you share on social media. Fact check everything, correct others (respectfully) when you see them getting sucked into the hysteria, and above all, don’t get drawn into the madness yourself. Let’s leave the zombies in the movies, and continue to enjoy spending time in the outdoors, admiring the wildlife that we are so blessed to be able to experience on a regular basis. Finally, let’s make sure to do our part to conserve that wildlife so that we, and future generations, can continue to enjoy it!