‘Zombie deer’ are roaming the prairies. Should we be worried about this?

CLIP You’re listening to a frequency podcast network production in association with City News.

Jordan Heath Rawlings I’m going to start by pitching you a movie. It’s about a disease that begins in the animal population and spreads. It crosses borders, it moves between types of animals. It begins to infect both wild and farmed populations. Hunters start to test the animals they’ve bagged, and most of them come up positive. Researchers warn that this disease is seeping into the environment and could cross over into other species that share the same food or habitat. And what does this disease do? It rots the animal from the inside out, leaving them looking like zombies, wasting away while walking around. That’s the first five minutes of my movie. You are already thinking it’s a horror film, and you’re probably screaming at the screen to government officials to please just listen to the scientists. You know what happens next. Well, now, let me introduce you to chronic wasting disease, a very real threat currently running rampant in deer and other similar animals on Canada’s prairies. It has already given us the term zombie deer, and it’s a cousin to mad cow disease, which you probably remember, right? Alarm bells have been sounding for a few years about just how quickly this disease is spreading and how many animals are affected. It has not yet passed into humans the way mad cow did, but it is possible. So why is funding for this so hard to come by? Why haven’t you heard more about it? Why, in this era of viruses and mutations and variants and diseases running rampant, aren’t we being a little more proactive, a little more suspicious about what a bad outcome might look like? Or is there really just nothing to worry about and everything will be fine? And that knock on the door in the middle of the night in a rainstorm is probably just the nice neighbor wanting to borrow a cup of sugar.

Jordan I’m Jordan Heath-Rawlings. This is The Big Story. Debbie Mackenzie is a professor at the University of Alberta who has studied prion diseases for 35 years. Her research is currently focused on chronic wasting disease. Hello, Debbie.

Debbie Mackenzie Hello.

Jordan As I just mentioned, you’ve spent decades researching these diseases. Can you just explain to people who aren’t familiar with them what they are and what they can do to animals?

Debbie Mackenzie Of course. So prion diseases are an interesting infectious disease because they are, as I said, infectious. They cause disease in animals and in people, but they don’t have the same DNA that you would find in viruses and bacteria. So the diseases are caused by a normal protein that we all have in our bodies. All mammals have prion protein, and under certain conditions, it misfolds into an abnormal form, which the body can’t easily get rid of. And eventually it migrates into the brain, where it’s toxic and it causes a fatal disease.

Jordan Can we cure these things?

Debbie Mackenzie And how much effort has been made in that capacity, we can’t cure them. There’s no treatment either in animals or in people that have these diseases. It’s been just over 40 years since we first determined that these were caused by this abnormal protein. This was work done by Stan Prusner at UCSF. He won a Nobel prize for this work. And ever since it was discovered, people have been trying a whole variety of different methods to treat or cure or prevent the disease, and we have not had any success yet.

Jordan How would most people be familiar with these kinds of diseases and where do they remember it from?

Debbie Mackenzie Mostly, I think, the most famous of the prion diseases is mad cow disease, or scientifically it’s bovine spongeiform, encephalopathy. This is a disease that showed up in cattle in the United Kingdom in the 1980s, and it’s actually one that jumped into humans with the first human cases of, in quotes, mad cow disease showing up in the mid 1990s.

Jordan Did you research that back then?

Debbie Mackenzie Actually, no. At the time I was in Wisconsin, at the University of Wisconsin in Madison, and we weren’t allowed to work directly with mad cow disease infectious agent because Wisconsin is the dairy state and they were very concerned about disease getting into their cattle.

Debbie Mackenzie And now you’re working on chronic wasting disease.

Jordan So let’s talk about that because this is impacting Canadian animals right now. So what is it and how did it give birth to the term zombie deer, which we began hearing recently?

Debbie Mackenzie So, chronic wasting disease is a prion disease that affects mule deer, whitetail deer, elk, moose, and more recently, it’s been seen in reindeer in Norway, Finland, Sweden. It’s one where the number of animals infected keeps increasing so that early in the infection, when it arrives in an area, there will be one or two animals detected is positive. There’s now areas in the, for example, south Saskatchewan river valley in Saskatchewan, where prevalence is about 80% in mule deer bucks, a huge number of the animals are infected. The reason is called zombie deer. This is actually a term coined by professor Ed Hoover at Colorado state university. And basically the fact that this is an abnormal protein, the normal form we all have, when it’s converted to the abnormal form, our bodies don’t recognize it as not self. So they sort of move it throughout the body and it spreads. And then it’s basically toxic to the neurons. So it eats the neurons from inside of our bodies and then the animal itself will present as wasted. So clinically affected animals look, have a hunched back, they have very weird behaviors and they look like they’re they’re wasting away like they’re starving.

Jordan Do we know where it came from and how it got to Canada?

Debbie Mackenzie Yes, we think so. One of the things with these diseases that makes it really complicated to study them is that the disease itself, from the time an animal is infected or a person, it takes a very long time before they look sick. So you can have perfectly healthy, normal looking animals that with mule deer and white tail deer and elk are actually shedding infectivity in saliva, urine and feces. What we think happened was that there was elk moved from South Dakota to Saskatchewan and that the elk, at the time that they were moved, looked healthy, but later went on to develop chronic wasting disease. With time, the chronic wasting disease spread between deer farms and eventually moved to animals outside of the fence. And then as it moved outside of the fence in about 2000, was the first Saskatchewan wild deer CWD cases. And then we saw it in about 2005 in Alberta and the numbers just keep increasing and the geographical range keeps increasing as well. So it started in Saskatchewan, eventually moved to the Alberta Saskatchewan border. It’s now moving very close to the national parks. In the last two years it’s moved into Manitoba. It’s already in places like North Dakota, Montana, et cetera. So it just keeps spreading.

Debbie Mackenzie Do we have any idea of, I guess, how many animals roughly are affected? And the way you describe it, moving sounds quite rapid. Has anything slowed it?

Jordan I can’t find a number that gives us the precise number. I know that there was about eleven, 1200 positive deer last year in Alberta. And you know, these are just the ones that were hunters turning the heads to be tested. So it’s not catching all of the infected animals for sure. But we’ve been averaging 1000 plus a year in Alberta and the numbers are going to be very similar in Saskatchewan. So thousands and thousands of deer. Now one of the things that appears to have slowed it down initially is that if you aggressively depopulate an area when you first detect CWD, it seems to really slow it down. It doesn’t necessarily stop it. I think that this is effective because initially the transmission is deer to deer, so like physical contact with each other. But as time goes by, because they shed infectious prions into the soil, etcd through the saliva, urine and feces, the environment becomes contaminated. And then as deer are grazing, they’re going to ingest soil that has infectivity in it and then it continues to spread. And I think that as the density or as the number of infected animals increases, obviously the environmental contamination increases and it makes it more difficult to stop it. This has been going on for a long time already.

Jordan As you mentioned, it’s recently spread to a lot more land area, at least in Canada. How is this different from mad cow disease?

Debbie Mackenzie When that was happening in the 1990s, that was a huge story. And I think I’ve seen like bits and pieces on, quote unquote, zombie deer over the past several years, but nothing close to what we saw over mad cow.

Jordan Why not?

Debbie Mackenzie I think a couple of reasons. First, mad cows in a farmed population. So obviously the beef industry, the dairy industries are critical both in the UK and in Canada. When we had our first case of home growing mad cow disease, all of the international borders to the beef industry shut down. So it had a huge economic cost. The second thing with mad cow disease is that even though it was first detected in the 1980s, by 1995 or so we saw that it could jump into humans, which makes a huge difference, I think, to people’s perception of a disease. Right. We have not seen any cases of human prion disease that can be linked to chronic wasting disease. So I think we’re talking for the most part, a disease that’s affecting wild animals, so maybe not a direct economic impact to Canada. I think it plays a huge indirect impact because as it gets, for example, into the national parks in Alberta, I don’t know what kind of an impact that’s going to have when there’s no deer and no elk to be seen in the parks anymore, or if you do see one, it’s wasted, emaciated, et cetera. So I think that the costs are very different and I think that a lot of publicity about diseases, et cetera, has a lot more to do with both economic and impact on directly on human populations.

Debbie Mackenzie People do eat deer. You mentioned deer farms. There’s a lot of hunters in the prairies. Could it jump to humans? You know, you mentioned they’re testing deer heads that hunters catch. What would happen if hunters ate these things without getting them tested?

Jordan We don’t know. The experimental evidence suggests that the barrier for transmission from deer to humans is high. That doesn’t rule it out. One of the things that’s difficult is, first of all, that long incubation period. So it was at least ten years in the UK from the first recognition of mad cow disease in cattle to the first human cases. So inevitably it could be a ten year or more incubation period in humans. We don’t know what the disease is going to look like with mad cow disease, when it jumped into humans, it affected younger people, so an average age of about 27, whereas the other human prion diseases generally affect people 55 plus. And it looked different to clinicians. So if CWD jumps into humans and it looks different, then I think we’ll see it. But if it looks more like the normal sporadic human disease, then I think it’s going to be more difficult to determine that it actually came from deer. Given that this disease is so rampant and yet doesn’t attract a ton of attention, what are the challenges in researching this and trying to either find a cure or, I guess, find a vaccine? Right?

Debbie Mackenzie There’s a number of challenges. One is that we can do a lot of preliminary work in the lab using mice that have been modified to express the deer prion protein, we can ask some basic questions that way. What we have is a lack of facilities both in Canada and the US. To do deer studies. And ultimately, everything that we want to look at in terms of treating or developing a vaccine is going to require testing in the deer. There are a few deer facilities in Canada, at the CFI facilities in Lethbridge, and there’s one in Vito and one more in Ottawa, but they all hold like small numbers of deer. That makes it very difficult. The long incubation periods of these diseases has an impact. When I was in Wisconsin, I did do one set of deer studies. The shortest incubation period from the time that we infected the deer until they got sick was just over two years. The longest was five years. So that’s a really long time to run an experiment. Then it becomes expensive. And so one of the things that’s difficult is often funding is for two years, maybe three years, and you set up an experiment that’s going to take five minimum, right? And that’s just until the deer gets sick. Then you still have to do all the analysis. And so lack of funding is a critical component for all of this because what do I do if I get funding? I get the experiment set up, but then, for whatever reason, when I try to renew that funding in two or three years, it doesn’t get funded. Now what do I do with these deer? Because I can’t pay for them anymore. So one of the things that would be very helpful always would be solid what we call core funding, that helps fund the animal facilities so that it doesn’t have to come directly out of the grant money that I have.

Jordan Does the government fund any of these core facilities? And given that the conversation we’ve had so far has touched on hunters and national parks, shouldn’t they?

Debbie Mackenzie There is not any federal funding directly mandated for pre on research right now in Canada, we had funding back in the 2000s, early 2010s, that was a federal funding agency, but it was set up primarily for mad cow disease. And so once the number of cases of mad cow disease decreased to none, that funding dried up. And we were spoiled in Alberta because we did have the Alberta Prion Research Institute from about 2005 until last year that provided resources as well. But again, that funding has decreased basically again on the premise that mad cow disease isn’t a problem anymore. So therefore that funding isn’t required.

Jordan So I’m not trying to ask a leading question or be hyperbolic here, but why haven’t we learned this lesson from mad cow or even from our recent pandemic experiences in terms of, like, funding this kind of disease research?

Debbie Mackenzie That it’s not a concern until all of a sudden it is a great comment. I think that it’s something that all of us that do research struggle with is that there tends to be a reactive response to any disease outbreak rather than proactive. And I guess, to be fair, there’s a lot of infectious diseases out there, and trying to decide where to put the dollars is always tricky. But yes, given the COVID pandemic, the fact that chronic wasting disease like COVID can evolve or adapt into different strains, different variants that have different properties, all of our research to date suggests that the most common strain of CWD out there right now doesn’t jump to humans. I would never say it’s not going to. I’ve learned that over the years. But all it takes is a variant of chronic wasting disease to become predominant, and that changes where it can move to. And it could move to humans, but it could also move to other animals. They’re all exposed. Everything that shares the environment with deer is potentially exposed to chronic wasting disease, be it pronghorn, antelope, bighorn sheep, mountain goats, voles, beavers, you name it, they’re going to be exposed. And the big one is actually caribou. We’re looking right now that caribou and infected white tail deer now overlap in their range, suggesting that CWD could jump into caribou. Is that what keeps you up at night jumping to other animals or eventually humans? What are your worries when you look at the level of funding that this gets and what could happen? I think that movement into other species is very worrisome because we know that when prion diseases move and adapt to a new host, it then changes the number of other species that they could infect. So the data is pretty strong right now that CWD does not, for example, orally infect cattle. But if CWD was to get into, say, the metal vole population and then the metal vole agent could then jump to cattle, and then we would have a different cattle disease from mad cow. Those kinds of things are worrisome. The human side of things also concerns me always. The number of deer that are infected continues to increase. Like I said, there’s places where 80, 85% of the mule deer bucks are positive. Many of those are being consumed. And we don’t know if it’s going to move into humans. But given an incubation period that could be ten plus years. People could be getting infected now and we won’t know for 1011, 1220 years. That worries me. It worries me that if I, as someone in my 60s, consume something that’s going to give me a disease in 20 years, that’s a risk. That might be worth it, I guess. But if you’re feeding venison to small children, that always concerns me. And it also concerns me when we look at some of the indigenous communities where virtually all of the protein that’s consumed is coming from deer, elk, moose. And again, we don’t know what the risk is.

Jordan Debbie, thank you so much for this. I hope you get the funding you need. And I hope none of the stuff we talked about ever happens.

Debbie Mackenzie You and me both.

Jordan That was Debbie McKenzie. Matt was the big story. For more from us, except, sadly, no more bmovie pitches. You can head to the Big Story podcast. CA you can find us on Twitter at The Big Story. FP n. You can email us hello at the bigstorypodcast CA, and you can call us 416-935-5935. The Big Story is available wherever you get your podcasts. It’s available on a smart speaker if you ask it to play The Big Story podcast. Thanks for listening. I’m Jordan Heath-Rawlings. We’ll talk tomorrow.