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March 17, 2023

Leader of the Pack

Leader of the Pack

In this episode, the hosts discuss a fascinating paper about a parasite called Toxoplasma gondii and its impact on wolves in Yellowstone National Park. The paper, published in Nature Communications, explores how this single-celled organism can alter the behavior of wolves and even the dynamics of their packs. The hosts delve into the life cycle of the parasite, its prevalence in humans and animals, and its ability to manipulate behavior in prey animals.

In this podcast episode, the hosts delve into a fascinating paper published in Nature Communications about Toxoplasma gondii, a single-cell parasite that can alter the behavior of its hosts. The study focused on cougars and wolves in Yellowstone National Park, where their territories overlap, allowing for the spillover of the pathogen. The hosts discuss the importance of Toxoplasma gondii, which can infect warm-blooded animals, including pets, livestock, and birds, and is zoonotic, meaning it can be transmitted to humans. They also highlight that the direct host is a feline, and everything else is an intermediate host.

The hosts discuss how the parasite can affect behavior, making prey animals bolder and more prone to doing risky things, which puts them at risk around wild cat predators. They compare this subversive style to rabies, where herbivores become more docile when they infect, making them easier prey for predators. The hosts point out that Toxoplasma gondii infects around two billion people in the world, with a high prevalence in the population, but most people deal with the infection without developing any clinical symptoms or disease.

The episode is a fascinating deep dive into the science of Toxoplasma gondii, with insights into its behavior-altering effects and the dangers it can pose to both animals and humans. The hosts also touch on the clinical aspects of the parasite, highlighting the guidelines for screening and treatment in immunocompromised individuals. Overall, it is an engaging and informative episode that will appeal to anyone interested in microbiology, parasitology, and infectious diseases.

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Thanks for listening to the Infectious Science Podcast. Be sure to visit infectiousscience.org to join the conversation, access the show notes, and don’t forget to sign up for our newsletter to receive our free materials.

We hope you enjoyed this new episode of Infectious Science, and if you did, please leave us a review on Apple Podcasts and Spotify. Please share this episode with others who may be interested in this topic!

Also, please don’t hesitate to ask questions or tell us which topics you want us to cover in future episodes. To get in touch, drop us a line in the comment section or send us a message on social media.
Twitter @Infectious_Sci
Instagram @tick_virus
Facebook Infectious Science Podcast

See you next time for a new episode!

Transcript

What we're doing today is we're talking about a paper, a little bit of a journal club. Yeah, journal club. And we're all going to talk about this paper. Danielle, you brought this paper, it was so cool to read. I've never read about this topic before. So it was really interesting for me to delve into it. Tell us what this paper is. So this paper is a really exciting paper and it was blowing up all over science Twitter a few months ago when it came out. And it was published in Nature, which is a really high impact journal Nature Communications. And it's about a parasite that you may have heard of, it's texel plasm, gone di and this parasite. They're looking at it in cougars and wolves and discovering that it might be altering the behavior of wolves. And even altering pack dynamics. Even if the parasite infects just a single Wolf, it can change that dynamics of the entire pack. And I just think that's so exciting that something so small can have such an incredible impact. And that's kind of to me, just like the epitome of why microbiology is so cool. Yeah, this is super cool. So I did see this paper on Twitter as well. But why did you really like picot? And and like, what captured your interest? And why did you select this paper? Well, most of what we know about Toxoplasma gondii. I think most of it we know about in prey predator dynamics, and we'll talk about that a little bit later. And Yellowstone National Park is this really interesting area. And that's where the study is being done, where wolves and cougars, their territory is kind of overlapping. And so we have this really exciting multi predator multi carnivores system that we don't normally see that wolves and cougars are usually, even though they have the same prey are usually kind of selecting to be separate. So this really interesting area is allowing for this interesting spillover of a pathogen, which I just think is just this really interesting area and I will kind of want to go to Yellowstone National Park. So it's a nice place to think about. Yeah, I've never been either. So listener if you're interested in sponsoring a an infectious science trip out to Yellowstone, we know take Venmo Cash App, Zell. So Dennis, you're the vet tell us about toxic so I only know about it and humans, right, we learn about and I've taken care of folks who've been infected with toxo mostly immunocompromised people, people with HIV AIDS usually advanced, the HIV they're immunosuppressed. They have low immune systems, they can't fight off viruses and bacteria like someone who's got all of their white cells and then we also hear about it in pregnancy. You know, those don't clean the cat box, you know if you're pregnant, because you may aerosolized the feces and inhaled it or be exposed to it. What is this pathogen and what does it look like in animals? You know, in vet school, you've Toxoplasma gondii is obviously a staple that you have to learn about, but not so much because it causes you know, devastating disease and animals but obviously, because it's a zoonotic disease and can be transmitted to humans, but we do learn about it. Obviously, cats being the main host and know a lot of Veterinary Medicine. focuses on domestic animals on cats and dogs. But it's not just house cats, right? No, that's That's correct. Toxoplasmosis is a disease cause you know, as we talked Toxoplasma gondii i and it theoretically can infect any or many warm blooded animals, including pets, livestock birds, and obviously people so I think the reason why we focus on cat so much domestic cats is because they live in close close proximity to us and a big one health question humans and pets and close proximity and, and human infection can occur through domestic cats. And I think that's why this is part of the education and why we learn about this so much. And, you know, typically most infected adult cats, they appear healthy. However, some cats may develop pneumonia, liver damage or some other health problems, but in most of the time, it's really avert, there's no signs of illness in cats, maybe if they are infected, they are lethargic, loss of appetite, but it's not really just a big deal in vets medicine. So some people are some people from cats being people, cat owners. So some cats, that mean do they manage? Some of them don't have any symptoms at all right? I mean, they can most of them. Yeah, most of them. And if you have an immunocompromised cat or a kitten, for example, feline HIV, right F IV that can immunosuppressed, the cat, then the parasitic infection has no control or is not controlled, and then we'll just go rampid in the cat and then the cat will get sick. Okay, so I'm hearing why it's important for cats certainly know why it's important for humans. So Daniel, when you were reading this stuff, what prompted these guys to do this study, what was the main problem they were trying to understand. So let's back up a minute, because there's a couple of things I really want to emphasize. Okay, emphasize emphasize this, this is a protozoan, just a single cellular parasite. And like Dennis said, It infects warm blooded animals in general, the real big important key here is it needs some type of feline to replicate. This is really, really critical part of its lifecycle, the direct host is some kind of Feline, everything else is like an intermediate host. And when it spread from an animal that's not a cat, it escapes the intestinal lining, and it can form me cysts, and muscle and brain tissue. And there's a lot of evidence that it could affect behavior. Now, the way it's spread is by basically three ways you can be spread by consuming the parasite eggs, but that can only come from one of the cats, and it can be through eating the cat, or it can be through coming in contact with feces of the cat or the scat or something that's been contaminated with it. The other way you can contract it is if you eat infected meat, anything that's been infected with the parasite. So it can be an infected cat or an infected dog or cow or anything like that. But the really important thing that you have to remember for the rest of the story is it's only replicating in cats, or cougars and our story. And so you use a couple terms there. I just want to like clarify. So you said direct host and an intermediate host right? So can you kind of flesh those out a little bit? Because I in my head, I was actually reversing them. I was like, Oh, the intermediate host must be the one where it's replicating. And then the direct one is where it's reversed, right? Yeah. So the direct host is where it's replicating. And that's cats. Everything else is an intermediate host, you can get it from eating the intermediate host. But you're not going to get it from coming into contact with the feces of the host. So are you saying in the intermediate host says no replication in the none at all, no. amplification of the parasite in the intestine? No, it just kind of travels from the intestine to kind of muscle or brain tissue and forms assists to protect itself and it goes chronic, it kind of just hangs out and doesn't do anything unless you're immunocompromised. And then it can start to cause some kind of inflammation in some disease, but it will just hang out forever indefinitely, but not replicate. And I'm against scare tactics. I'm against just anybody knows me. I don't like people would be scared. But the numbers that we're seeing were pretty crazy. Like 2 billion people in the world. Probably infected. Yeah. Okay. That's a lot a lot. Right. I don't know the exact number. But it's a very high prevalence in the population, which is something we don't always think about. Right? Yeah, well, probably because it's not causing any disease in most of those people. And in most of those animals that's not causing any disease. Yeah, I think this is something that the major take home messages I would say is that a lot of people get exposed to toxoplasma and they will deal with the infection, but they will just seclude the parasite and there's no clinical signs as no threat to help in any way. So that's the most common outcome of an infection or an exposure with toxoplasma. I think that's kind of like really something we need to emphasize. Yeah. Okay. So that's kind of The basics of the parasite. But what's really, really cool is this kind of idea that this little micro unicellular organism is there's a lot of evidence that it can change behavior, even in these hosts where it's not doing anything else, and it's just hanging out. So, for example, in rodents, and monkeys, and hyenas, it all really makes them more prone to do risky things. In rodents, it makes rodents less adverse to house cat urine, and in monkeys that makes them less averse to leopard urine. And in hyenas specifically, it makes them a lot more bold around lions, right? These are all really dangerous things, this increases the likelihood that these animals that are infected are going to be around a wild cat that can eat them, and then that cat would become infected. So this parasite makes the animals bolder, these prey animals Boulder, puts them at risk, and put some around these cat predators and then kind of perpetuates itself. And that kind of interesting kind of subversive style almost sounds a little bit like rabies, right? Like where you have herbivores that all of a sudden become more docile when they infect an easier prey for predators. Correct. Do you would you agree? Yeah, for sure. Yeah, it was so interesting, Danielle, because you sent me down a rabbit hole when you sent this paper because I started thinking, oh, man, like, I only know the clinical part right out, I know, the dose of antibiotic you're supposed to give I know when you're supposed to, you know, the guidelines for HIV say you're supposed to screen for talkshoe. And when you're supposed to treat and so I know those things, but I didn't know anything else about what toxic do to behavior.