Stuff You Should Know - How has toxoplasma turned the world into zombies?

Episode Date: July 14, 2009

Toxoplasmosis is a parasitic infection that favors cats, but it can also be found in humans. Discover the disturbing details of how toxoplasma gondii finds a host -- and how it affects human beings -- in this podcast from HowStuffWorks.com. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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and LVT. For cleaning tips and exclusive offers, visit Bona.com slash Bona Clean. Brought to you by the reinvented 2012 Camry. It's ready. Are you? Welcome to Stuff You Should Know from House.Works.com. Hey, and welcome to the podcast. I'm Josh Clark.

With me is the always lovely and effervescent Charles W. Bryant. I have on shorts today. You do. You look like you're ready to go to the beach or play basketball or play beach at the basketball. And I'm at the opposite of that. Play basketball at the beach. Yeah. You can do that in Southern California, buddy.

You can do anything in Southern California to show us what I hear. Yeah. I can do anything because my wife's out of town. I know. Chuck's a bachelor today. Batchin' it, as we say. He looks terrible. He's dressed shabbily.

Yeah. He clearly hasn't showered. Batchin' it for a few days. He's got stuff stained on the front of his shirt. Probably steak. And his beard. That's a big hunk of steak on your beard. It is.

So, Chuck, how are you feeling? I feel a little tired and under the weather because of my bachelor experiences. But I am ready to go. Are you? Yeah. You're bringing it? Yes. So, Chuck, you know how neurotic I am, right?

Like, right now, I'm thinking about what you're really thinking about me. Yeah. You're a little neurotic. I wouldn't say hugely neurotic. I'm definitely not Woody Allen neurotic. No, no, no. But things like guilt, self-doubt. Right.

What was the third one? Self-doubt. You always think you stink on the show, which is just ridiculous. Well, I do. Because you're good. Regardless, these things drive me, right? Yes, they do. They do.

So, yeah, I would consider myself fairly neurotic. And I recently found out, Chuck, actually thanks to a new show that has inspired this podcast and the next one. We're doing a pair of them on Parasites. It's an animal planet show, actually, called Monsters Inside of Me. Yes. And the staff is parasite crazy right now. It's all over the blogs.

The blogs are lousy with parasites. Lousy with parasites. Because it's a really cool show. Have you seen it yet? I've seen parts of it. Yeah. On the DMC. It's wicked cool.

Yeah. It is wicked cool. And frightening. Yeah. I like it. I think it's cool. Mainly, though, because it relieves me from any responsibility for my own personality. My own horrible, disappointing, obnoxious personality, actually probably is the result

of a latent infection by a little thing called toxoplasma gondii. Yep. T-gondii. T-gondii. I'm going to call it toxo. I'm going to call it toxo. You can call it T. You can call it T. I'll call it toxo.

Okay. Yeah. Just for ease of pronunciation. Yes. But yeah, this is a parasite. It's a zoonotic disease, which means we catch it from animals. Right. It's relative of malaria.

It is. It is possibly running the world. Yeah. This is a little disturbing, I got to tell you. A tad bit. So let's talk about T. Let's talk about toxo. Yeah.

It is a parasite, as we said, and has a complex life cycle, like most parasites. And the life cycle has a purpose to get into its final host. That word just creeps me out, host. Or definitive host. Yeah. Yeah. This one is unusual because it completes its life cycle in one place, in one place only. And that is inside of a cat.

A cat's gut, actually. A cat's gut. Yeah. This is where T wants to be. Yes. Because this is where it gets it on. And reproduces. Yeah.

Everywhere else, it does. It goes to incredible lengths to get back into the cat gut. Yeah. It's crazy. Honestly, we haven't gotten into this yet, but this is like master blaster from Thunderdome. It's like the little guy just running things and making whatever it needs to carry it to the cat gut, do whatever it wants to get it into the cat gut. And toxoplasma is actually really common.

Just run into as much as 80% of the world population is infected, has a latent infection with toxoplasma. Right? Yeah. 67% of Brazilians alone. Yeah. But then on the other side, 7% of the UK is infected. So yeah.

It's lopsided. And this may sound familiar already because for many, many years, we've known that pregnant women should stay away from cat feces, which is where you can pick up a T infection. Just go ahead and say that our guest producer, we have a guest producer this week. Oh yeah. Hey Lizzie. He's lovely and fetching Lizzie. She thought I was kidding with her when I told her that.

Oh really? That pregnant women can't clean out the cat box. She thought I was pulling her leg and I was going to like pull one on her. That was actually like the first public health warning I ever came across. Yeah. I've known that since I was, you know, knee high to a grasshopper. Yeah. I love that phrase.

Yeah, I know you do. So yeah, you're not allowed. You're not allowed. You're not supposed to clean out the cat box if you're with child because fetus is one of the ways, one of the things that can be harmed. Yeah. Grown adults supposedly can't be harmed. Like serious birth defects.

So yeah, if you are, if your lady is pregnant, you want to go ahead and take care of cleaning out the cat box during that nine months because that's how toxoplasma infections result from handling cat feces or more specifically, and I got the impression that it's much more virulent when cat feces mixes with soil. It has much more staying power, that kind of thing. So if you have a cat that likes to poop in your garden and you're a big gardener, you're going to want to murder your cat and get rid of all of your topsoil and start over again. I imagine you could also get it from eating a rat because rats and mice tend to get it

as well. You can also very easily get it from eating undercooked livestock that has been around cat feces. I mean, how many farms have cats on them? Quite a few, I would say. So let's talk about the life cycle of this because it's interesting that you mentioned rats or mice because these things are under arguably the most control of tea, you know? That confuses me because I had a car named Tea.

So all right, I'll call it Toxo. Okay, all right. I had a car named Toxo as well. Man, that's not true. Did you have one named Tea, Gandhi? No. Okay, well, I'll go with that one. Thanks, Chuck.

You know I have a speech impediment. We'll go with Toxo. Okay, so Toxo gets into the soil. Let's say your little kitty goes and poops outside and Mouse passes by the soil, passes over it, eats it, rolls around in it, plays with it, makes a little clay sculpture out of it, and that's his friend. And the rat's infected. So this parasite actually goes through the bloodstream and travels to the brain where

all sorts of freaky, freaky stuff start happening to the rat's behavior, rat or mouse. And that's slightly alarming to us because as everyone knows, which is why we use lab rats, we have very similar brains to rats. Yeah. Chemically, the way it's put together, the whole deal, which I've always thought was interesting. Well, let's talk about rats as the intermediate host. So now a rat is infected with Toxo plasmosis.

Gross. Its brain is being taken over. What are some of the weird things that begin happening? Well one thing that I thought was most disturbing was they actually become fond of cat urine. They do. They're attracted to the scent of cat urine, which is the opposite of what's supposed to happen. Yeah, they did a test where they, did you see the one with the little sleeping, they made

the little beds for the rats, and one of them was soaked in cat urine, and they would actually go for that bed. They prefer that bedding over their normal bedding. Which is really weird. Really weird. I wrote another study that found that these rats were actually attracted to cat urine, not just the scent of it, they would go and investigate cat urine. And they investigated the brains of these rats, meaning they chopped their heads off

and cut their rhythm open. And they didn't just ask some questions? No. Although they did do studies, like they did different trials, and what they found essentially was that the rats or rodents lose specifically their fear of cat urine. That's it. Everything else remains intact. All other innate fears that they have, that all rats and mice display, remain intact.

It's just their fear of cat urine. So they're attracted to cat urine, plus also, toxo has an effect on your motor reflexes. So you're not quite as fast as you used to be. So these two things together, an attraction to cat urine, the scent of cat urine, and slow reflex time, means that you can get eaten by a cat. And that means you get into your final host. Right. That means the toxoplasma has made its way back into its definitive host, the guts of

the cat. By controlling the brain of the rodent. It is the coolest, most frightening thing I've ever heard of in my entire life. It really is. Just like you said, Chuck, rodent brains are very similar to humans in composition, at least chemically, right? That's why we're always experimenting on rodents to find out how we can treat schizophrenia, that kind of thing, which leads us to since 80% of the human population is infected with

a latent toxoplasma infection. Is it having an effect on us? It looks like yes. Well, yeah, for many, many years, they always said, oh, so many people have it, but it's really not the big of a deal because once it enters the human body, it's kind of, we're not going to get eaten by a cat anymore, like a lion or a tiger, so probably doesn't matter. Once we're infected, they go and inform resistant cysts, and basically just hide. And that's it.

They don't do anything. They set up camp in your body. Right. But generally, that's it, unless you have AIDS or another repressed immune system disease. Sure. That's when it gets infected. Right. But it's going to just sit there because we have antibodies that can keep them in check.

But that's what we thought. Exactly. But around, I think 1992 is when they really started to begin to look to see what kind of behavioral changes toxoplasmosis might cause in humans, and we started to find some startling results, like that lowered motor reflex time. Right. And that's that, I know they did a couple, one where they were supposed to stroke a specific keystroke on the keyboard in a certain amount of time, and another where they showed a white

recognition test where they showed like a white square on the screen, and you were supposed to react when you saw the white square. And they found that people that had the latent toxoplasmosis, there was a lag that were definitely behind the rest of the crowd in recognizing these things. Right. You know who conducted that study? Your buddy. A guy named Dr. Yaroslav Fleger.

You just talked to him. I just talked to the guy on the phone. This guy is arguably the preeminent expert. He's a parasitologist out of Charles University in Prague. Did you call Prague just now? Uh-huh. No way. No way.

Wow. And I need to expense that because I did it on my cell phone because you know I'm not comfortable talking at my desk because I'm neurotic because I have toxoplasmosis. Yes. Because you play in cat poop. Right. So Dr. Fleger, who is arguably the foremost authority on toxoplasmosis, he conducted that study.

And many more. Right. I think he conducted 11 and in nine of the 11 studies there was a significant difference between people who were infected with toxoplasmosis and people who weren't. Yeah. In humans there is actually an equal and opposite effect defined by gender. This is what I thought was really interesting. It's odd.

It was almost dead opposite the way men and women were affected by this thing. Yeah. Women kind of got out ahead in this deal. Yeah. Wouldn't you say so? These are the women we love, the toxoplasmosis infected women. That's my favorite. Women who are T-infected and not Chuck's car but the other kind, they tend to be warm-hearted,

outgoing, conscientious, moralistic. These are wonderful women. The salt of the earth. Yeah. But also outgoing. Like, everybody loves a gala who's willing to just try anything but also has a line which is moralistic. So, yeah.

Men, though, men got the bad end of the stick. We tended to be stupider but more loyal. Is stupider a word? Are you toxoplasmatic? I am. Less intelligent, more loyal, frugal, which was interesting, and mild-tempered. And dogmatic. Did you say dogmatic?

I did not. I was meaning inflexible, basically. Right. But they're both neurotic. Basically, guys who are infected with toxoplasmosis are jerks. And women who are infected are cool. Right. Yeah.

But they're both neurotic. That was the one shared trait. Right. And so, I talked to Dr. Fleger and I was asking, you know, where are we as far as understanding how toxoplasmosis could affect us physiologically, our brain? And one thing I saw that kept coming up was neurotransmitters. He said the likeliest candidate is dopamine, or dopamine, as he put it. Right.

Did he really? He said it increases levels. And he also has found that there are increased levels of testosterone in men, lowered levels of testosterone in women who are infected with toxoplasmosis. That makes sense. So, he said, in his opinion, that would account for it. Again, he's a stickler on pointing out correlation, not causation. We are definitely at the correlation stage in understanding how toxoplasmosis can affect

human behavior, but he's finding some really cool stuff. For people who love food, there's no place on earth quite like Mississippi, where a melting pot of culinary talent blends the flavors of yesterday and today. Sweet, savory, spicy, and smoky flavors that'll satisfy your spirits wherever you choose to wander. Join your next dining adventure at visitmississipi.org slash dining, Mississippi Wanderers Welcome. Has your household been hit with COVID-19? Learn about a research study from the Comfort of Home.

We are looking at ways to help people with COVID-19 feel better, faster. Learn more at active6study.org slash radio. That's activ6study.org slash radio. Yeah. That's interesting about the, it kind of makes sense with the testosterone levels because they found that, like we said earlier, 67% of Brazilians are infected with this stuff. In countries, they found where there were a lot of people infected with this or more likely to have masculine sex roles in this country.

Or more divergent gender roles or more pronounced distinction among genders. Exactly. Like the men go out and they're masculine, they do the hard work and the women. They work inflexibly. Exactly. Yeah. And the women are just like, that's my man. Yeah.

Yeah. Very interesting. Yeah. I mean, think about it. If 80% of the population is infected with a latent toxoplasmosis, then yeah, this would conceivably alter cultures. Still a little hinky if you ask me. I don't know, man.

It's still new research, but I'm thinking it started to look like this parasite rules the world. Well, it could be one factor. Because we ruled the world. We're ruled by toxoplasma, ergo, toxoplasma rules the world. I think it's a bunch of factors. That's me. Quite.

That's my camp. So, you know, Flager also conducted a study back in 2002 in Prague, where he- It's a driving test? Yeah. He, I think it was 167 people who were identified as the causes of car accidents. Right. Either as pedestrians or drivers. Yeah, which I thought was also interesting.

And he found that people with toxoplasmosis are 2.65 times more likely. That's almost three times as likely to be involved in a car accident as someone who's not infected. I think that goes back to the latent reaction time. Wouldn't you think? Could be. The delayed reaction? Again, though, there's, well, yeah, yeah, how it affects our motor skills.

Oops. Right. Crash. Sure. It's more reckless, like, if you're a man. Because we said that you're more willing to break rules if you're a man infected with toxoplasmosis. Right.

Red light. Screw it. Exactly. Or, this car will stop for me if I walk out in front of it. That kind of thing. But, again, we're at the correlation, not causation stage. So- Everyone points that out.

It's entirely possible that people in Prague who have cats and would be more likely to be infected with toxoplasmosis are also more likely to zone out while driving, thinking about how a princess lady would look really good in a little cat-tr that you saw online that morning. They said it could be a personality thing, which I thought that was a little hinky, too. But there's also a correlation between schizophrenia and toxoplasmosis. Not hinky. No.

This is, there's a definite link, and there's also a neurotransmitter called nitric oxide. This is not Flager. Flager actually said that he had not done much research on nitric oxide or nitric oxide, as he called it. But actually, some guys from Toledo, my hometown, some psychiatrists have been researching into it. And there are increased levels of nitric oxide in schizophrenics and toxoplasmatics. And schizophrenics are more likely to own cats, which I thought was odd, so says the University

of Maryland. Right. They own cats because the toxoplasmosis and the neighbor's dog tell them to. Right. Actually, not the University of Maryland. Sorry. Stanley Medical Research Center in Maryland. I got you.

Just wanted to clear that up. So Chuck, what do you think? Do you think it's still hinky? I think it's slightly hinky. I think there's something to it, but I think it's, like I said, I think it's one of many factors probably. I don't think you can chalk up the machismo of the Brazilian man to cat poop just yet. So that's toxoplasmosis.

And if you are into parasites or this podcast has piqued your interest, Chuck and I would both strongly recommend that you watch that new show Monsters Inside of Me on Animal Planet. What is it? Wednesdays at 9? Wednesdays at 9. It's a cool show. Yeah. Cool graphics, like CG, they get inside your body as if you were a parasite.

Yeah. Our parent company, Discovery, definitely threw some money at this one. It looks very cool. Definitely. Yeah. So check that out. And we also have tons of cool stuff. You can also check out the Monsters Inside of Me website.

Yeah. Robert Lam. Robert Lam wrote some really cool stuff and actually we have to give him a big thanks for pointing us in the right direction for research on this particular podcast. He knows what he's doing. He's parasitastic. Yeah. And of course, HowStuffWorks.com has tons of stuff on it and if you're interested you

can also read all of our blog posts on it. There's like five million of them and each one's better than the last. Yeah, that's it for plug-in, isn't it? I think so. Yeah, plug heavy for change. Which means, buddy, it is time for Listener Mail. So Josh, I'm just going to call this, We're Awesome because we saved a woman's life. Yeah, this is crazy.

It is. Slightly hanky, but I'll take credit. Bonnie from Boulder, Colorado wrote in and Bonnie says this, Hi guys, stuff you should know just saved my life, the facts for these, I was driving home and it just finished listening to your hypermiling podcast. As a result, I was only going 40 miles per hour on a stretch of highway where I usually go 60. All of a sudden there was a pair of headlights right in front of me.

Some genius was going the wrong way in the same lane of the highway as me. Short story, even shorter, I ended up facing the wrong way on the highway. Thanks to some recent rain and some awful skidding and sliding, but due to the late hour lack of other cars and my slow speed, I avoided hitting anything. Who knows if I would have had a head on collision if I'd been going my normal speed, but I do know that thanks to YouTube and you're always a lightning podcast, I will never have to know. Many thanks.

You're immensely appreciative listener and fan Bonnie of Boulder, Colorado. Thank you Bonnie. Dude, awesome. Honestly, what if she would have been going 20 miles an hour? That could have made all the difference. Oh yeah, definitely. Even if it was just a fluke thing, I'll take credit. Yeah, even if it wasn't fluke, we still picked up an indentured servant for life.

Yeah, and I personally, I think we should get a key to the city of Boulder, so. Yeah, I've been angling for one of those for a long time. A key to any city? No, Boulder. Oh, okay. Yeah. So this is our inn for sure. I hope so.

Maybe a t-shirt even. Sure. Yeah. I saved Bonnie's life and all I got was this lousy t-shirt. That's a good one. If you have any good t-shirt ideas or any instances of how Chuck and I saved your life, you can send them in an email to stuffpodcastathowstuffworks.com. For more on this and thousands of other topics, visit howstuffworks.com.

Want more howstuffworks? Check out our blogs on the howstuffworks.com homepage. Brought to you by the reinvented 2012 Camry. It's ready. Are you? Our travel brings a basket full of learning in Mississippi with family-friendly places like the Mississippi Aquarium, the Hattiesburg Zoo, and Tupelo Buffalo Park. Explore today at visitmississippi.org slash family fun.

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