Radiolab - Parasites

Episode Date: September 7, 2009

What's gotten into you? In this hour, Radiolab uncovers a world full of parasites.

Wait, you're listening. Okay. All right. Okay. All right. You're listening to Radio Lab. Radio Lab. From W. N. Y.

C. See? Yeah. And NPR. I thought we would begin by looking backwards at a wonderful moment in the history, cinematically, of parasites. The cinematic history of parasites? Mm-hmm.

Okay. So do you remember that movie? I'm not going to tell you. the name of it. Yeah. Starts out. In fact, I have the script right here. Setting.

Space. Okay. Vast, empty space. The script continues. The stars shine cold and remote, like the love of God. Ooh. Do you imagining this?

Yes. Now, floating in that vast nothingness is a tiny dot of a ship, you can barely see it. Cut to the interior of the ship. I feel dead. Here we are in a ship full of astronauts who are tired and dirty. Anybody ever tell you you look dead?

And they're, you know, paling around. And you just get the feeling this is a normal day in their astronaut life. Until... What? There, on the computer radar, there is a disturbance. Oh, some kind of distress signal. A transmission? Out here?

Yeah. They think we got to check this out, so they trace the signal, eventually get into a pod, and shon! And they find themselves at this abandoned ship. Totally abandoned. It's like a ghost ship. I've never seen anything like it. I wonder what happened is it crow?

It's empty except for these weird eggs, and the astronauts are like looking at the eggs and touching the eggs and going... Okay, now fast forward. We're back into the first ship. Okay. Everything's fine, for the most part. And then something happens. And I want you to...

I've got the computer there in front of you. Okay. Well, push the space bar. Space bar. All right. Describe what you're saying. They're at the table. Everyone's dressed in white.

The first thing that I'm going to do when I get back is to get some decent food. They're talking and chatting. They're all having like salad. Yeah, they're just eating and talking. One of the guys gets a little weird, right? Oh, he's not feeling so good, one of the guys. What's he doing? Uh-oh, now he's coughing.

Coughing? Oh, he's having trouble breathing. He's fallen back onto the table. His chest is heaving. Rest, oh my God, he's He's shaking his head wildly and he's like flexing all over the table And something

He's like right Oh Oh, oh God Oh God So there's a red thing A red, horrible snakey thing This is of course the classic scene from the original alien movie The scene where the little thing

Burst out of the guy's chest and like hisses Why didn't you make me see this? Because I think I figured out why that scene is scary. I mean, when I first saw this movie, that scene went over and over and over in my mind. And it's had this effect on a lot of people. And I think I know why. What do you know? It's not that the little creature is disgusting, which it is.

It's that it was there all along. Sitting there. Yeah, inside him, like incubating, waiting. To think that you sitting in that seat right there could have in your gut these little. worms that are wriggling around and doing more or less what that alien was doing and I can't even see them in you? I can't even talk about it.

So it's not. Today's subject on Radio Lab will be Flowers in Meadows coming up after this. No, we're not doing that. We're doing an hour on parasites. These little creatures that live inside us invisibly

and yet can have a huge influence over who we think we are. What is a parasite precisely? a moocher. And just to sort of slide us in, get us into the mood. I'm already not in the mood. We thought we would get things started. Maybe I'll just move this.

Okay. Well, there really is no other way to start a show on parasites, except with this guy. You should introduce yourself. My name is Carl Zimmer. Carl's a science writer. Yeah. And parasites have been on his radar ever since he was a little boy. I grew up on a little farm and my mother would raise tomatoes sometimes in a vegetable garden.

and sometimes there would be these caterpillars feeding on them, and my mom would be very annoyed. And every now and then I would notice that some of them didn't look very well, and they had this little sort of fuzzy white bumps on them. And I didn't really know what they were. Well, it turned out that they had been attacked by a parasitic wasp, which had laid its eggs inside of it. Those eggs had hatched and had become larvae. And those larvae were swimming around inside that caterpillar while it was eating my mother's tomatoes,

and they were growing. Growing inside the caterpillar. And then finally, when they were ready, they came out, and only then did their host die. And when he finally found out that that is what was happening, inside those fuzzy white bumps? This profound situation. This whole universe of babies growing into adolescence.

That's when I guess I sort of got very hooked. Which is probably an understatement. Because you are sort of like capital P parasite man. And if you look, in the New York Times or science magazine or any of the places Carl writes, a suspicious number of his articles are pretty flattering to parasites. People have been dismissing parasites for a long time, calling them degenerates. Now, I would argue that parasites are not degenerate. They have gained the ability to live inside three, four, five, six different species. So do you find that you sort of, you're a lawyer for them?

Hey, sir, you call this degenerate. How dare you, sir, say that? I think I'm a defender of all neglected and put upon species out there. Why wouldn't a parasite be what I think you mean when you say degenerate? Because the tiny little thing, it infects something else, it sucks whatever. It's not independent. Right. So when you say it's not degenerate, why do you say that? Well, let's start with saying it's not independent.

Are any of us independent? Kit Carson. If you stripped all the bacteria out of Kit Carson, Kit Carson would get very sick. Daniel Boone, on the other hand. Now there's a guy. Independent, alone in the woods. What does Daniel Boone eat? I guess Daniel Boone eats pigeon like the rest of us.

What's your point, Carl Zemar? My point is that Daniel Boone eats meat. He ate bread, which came from plants. Well, there's a question of degrees, though. We're not living inside the intestinal tract of some other creature. So why does living inside seem like it's a degenerate thing as opposed to us? You know, we can't even synthesize a lot of our own vitamins anymore. We're degenerates in a lot of ways.

No, Carl. No, car. If you are a creature that lives off someone else's vitality. Cheaters would be another way of putting it. But listen, can you appreciate how hard it is? And I'm just going to cut this short right here. Carl says no. No, no.

They're amazing. Time and time again, he says no. And the argument went on. Still waiting to hear about how you are able to photosynthesize yourself. It's true. I eat plants that do it for me, but I go about it in a manful way. You can't even do it yourself. Like I said, the argument went on and on with Robert saying one thing and Carl firing back and me adding another.

And here's what we're going to do. Just to be fair and square about this, we're going to bring in an independent moderator. Lolo! Yeah? Come. You're going to be the moderator. Yeah. You get that mic right. You're going to be the moderator. And you listening right now, we will leave it to you. Your decision. In this one lightning round of, go ahead. Shall I do? Okay.

Yeah. Parasites. Are they evil? Or are they awesome? Starting with number one. The parasitic wasp. There are probably 200,000 species of parasitic wasps out there. Big wasps, small wasps. They're generally pretty tiny. And they go after all sorts of things.

So some will lay them in... Carl's caterpillars, spiders, or the one Carl's gonna tell us about? This particular wasp is called Ampilex Compressa. Goes after... A cockroach. And for those of you who never thought you'd feel sorry for a cockroach, keep listening. So what it does is it flies around and it looks for a cockroach. And once it finds that cockroach, it lands.

And then, the fight began. They tumble back and forth, around, around, until finally the wasp somehow manages to arch its back around the body of the cockroach. And stings it. Right in the belly. The cockroach twitches for a second, and then falls. Boom. The cockroach is paralyzed.

Now the wasp takes its time, repositions itself. puts its butt up right near the cockroach's head. And delivers a second sting. The stinger actually sort of threads its way to a particular spot in the brain. And this does something odd. Moments later. The cockroach recovers, sort of stands up and can walk again. But something is wrong.

Very wrong. It just stands there. Like, I'm awake, but... It can't run away. Can't move. It has essentially lost its will. What does that mean? It's a puppet.

Yes, it is a puppet. It's become a zombie, basically. And so now the wasp will literally grab onto the cockroaches' antenna and start pulling on it. How does it grab? With what does it grab? I believe with its mouth. Imagine a tiny wasp guiding a cockroach across the desert floor. Like a dog on a leash. And so it leads it, down, down, down.

down. Down into a little burrow it's made. And the cockroach says, okay, wherever you want to go. Then, once the wasp has the roach in the burrow... It lays its eggs on the underside of the cockroach. So now you've got this drugged roach sitting on top of some wasp eggs. And then the wasp goes out and it seals the burrow. It buries the cockroach alive?

Well, it's in... It's in a cell. It's in a little chamber. I mean, it doesn't want to kill the cockroach because this cockroach is going to feed it. It's young. It's young, yeah. So then the eggs hatch, and then they drill inside the cockroach. You're still just sitting there.

How's it staying alive at this point? Well, parasites are very careful. You know, they won't eat vital organs that will kill it. Instead, Carl says, they just feast on the extra stuff. There's a lot of stuff inside of a cockroach, a lot of fluid just floating around. Pits of wonder bread. Essence of skin, old hair. And you can just feed on.

And the host stage. alive. Wow. And then what happens? Eventually the little baby wasp larva grows up inside the cockroach and develops into an adult. And then one day the wasp eats its way up a little hole out of the out of the cockroach's body, shakes off its wings and flies off. And then the roach dies. Then the roach dies. And only then. Yeah. That to me sounds like of the purest description in nature of evil that I can imagine. Wouldn't you agree? Well, Darwin certainly said that God should not be personally blamed for having created parasitic wasps. But if you ask Carl, he'll have you think about that moment, the moment where the wasp stings the brain.

Parasitic wasp can attack a cockroach and insert its stinger into one specific part of the cockroach's brain and inject a precise little cocktail of drugs that they're then turns the cockroach into its slave. I know that that wasp didn't get a PhD in neurobiology. And yet it has performed a kind of brain surgery. Very precisely, in a very elegant way. Or evil. Might be the other way.

Okay, so go ahead. But there's a complexity there that you can't deny. Or can you? We leave it to you, bringing us to example number two. Parasitic nematode. I mean, here's another example that I actually was looking at today. You're holding your computer up to the glass? And on the screen is a big black ant.

It looks like it's carrying a cherry? Right. A cherry that's about twice the size of the ant. That red cherry is actually parasites inside of the ant, making it look like a red cherry. What part of the ant is that? Is that its butt? Essentially, yeah. Wait a second. It looks like it's sticking its big red butt up into the air. Yeah, their behavior has changed, so they waggle around their tail, as it were.

Now, why on earth would a parasite turn an ant's butt red and then make it stick its butt up into the air? Well, let's say you put an ant down that has this bright red rear end and an ordinary ant in front of a bird. Birds can go for that red ant very quickly. Because it thinks it's a berry. Yeah. And then what? It's going to swallow this little package full of nematode eggs. So that's the way the nematode eggs get into the sky.

They buy their airplane tickets by advertising themselves as berries. Yes. What's the benefit of being in the air? Well, the only place that this parasite can reproduce is inside the bird. And how better to spread your seed far and wide than to drop from the sky? With the bird's droppings. That is brilliant. That's brilliant.

I mean, look at the, it's red is up in the air. Yeah, it's amazing. It's like, how can a stupid little thing be so brilliant? Because they're not degenerates. But they're still cheating. And then just to bring his point home. Just to pick a common one. Carl offered up his third and final example.

Number three, blood flukes. Blood flukes are related to flatworms, tapeworms. So their eggs start out in the water. freshwater in Africa, Asia, parts of South America. And the first part of their life, they go into a snail and they come back out into the water. And they're swimming around, and they start looking for a human. So imagine a foot going into the shallow end of the pond. I see toes. I see bottom of foot. I see ankle.

Well, if you're a blood fluke, you don't see anything. You don't have eyes. Oh, sorry. But eventually you find a foot. Secrete a little enzyme. basically turn a little bit of skin into butter. And you slip into the vein, and now you're going to swim my circulatory system. You're going to ride along in the blood. And now it's time to find a mate.

A mate? So there's sex, so there's male and female, is what you're saying? Sure, they're animals. They're animals. I would have never called them animals. That's interesting. You say that. That's a whole other topic, I guess.

So, all right. So the female is very thin. in, sort of a standard issue worm kind of thing. But the male is very strange. It's kind of like a canoe. It's got a big trough down the middle. And at one end, it's got a giant sucker. Should we urge some of our listeners to tune away at this point?

Because what is about to happen may not be acceptable in family hour? Well, actually, blood flukes are fairly monogamous and loyal. So, you know, if you're looking for animals to reinforce your family values, blood flukes are pretty good. And eventually two blood flukes find their way toward each other, and the male does a sort of courtship. For whatever reason, the female says, yes, I accept your courtship. The female joins the male, so fits in the trough.

Oh, so it's like a groove. The female goes and occupies the groove. Right. Now, this isn't mating. This is way beyond mating. The males will feed the female, for starters. And they will stay this way, A long, long time.

Really? Yeah. Like days? Years. Years? Yeah. Oh, my God. Years in human time?

Years to them? Just years. Years, years, years, years, years. Years, like the earth going around the sun kind of years? Yes. In fact, there have been cases where people show up at their doctors feeling awful. The doctor does some tests and says, Oh, you've got blood flukes.

Now, you had to have been in Africa to get this disease. When have you been in Africa? and the person said 40 years ago. What? 40? Yeah. 40 years ago. Yeah. And the reason that they're getting sick is that these male and female blood flutes are still together making eggs. And Carl's literally glowing when he says this.

I have to admit, I do love the thought that parasites are among the most monogamous animals on the planet. It's heaven. I mean, you're going to spend the rest of your life together. And so our story concludes, with the image of two blood flukes spooning in your veins for nearly half a century. You got a hand to him, he's good. Carl, you mean? Yeah.

And there is a species of tapeworm that's going to be named after me. No kidding. Really? Yeah. Wow. It's not quite as much of an honor as you think at first. I was talking with the parasitologist, and she was telling her,

fellow expert about how she was going to name one for me, and then they got into a conversation about, you know, that was good that you named that particular tapeworm for him because he's kind of thin, and it's kind of a thin tapeworm. You know, my aunt is she's a little round, and it's kind of a round tapeworm that I named her after, and you suddenly discover there are a lot of tapeworms to be named. How many is a lot? Tens of thousands of species of tapeworms. Wow. So they got us beat many times over. I once saw estimates that if you took all the viruses in the ocean and you stuck them in to end, how far would it go? And it was many light years, way beyond our galactic neighborhood. In other words, they're more cheats than there are

honest people, honest creatures on Earth. Oh yeah. We should go to break, don't you say? I think we should. Thanks to Lulu Miller and of course Carl Zimmer, who has written many books, including Parasite Rex, a book we shamelessly parasitized for the making of the previous segment. I also want to encourage you to go to our website where you can find pictures of the blood fluke spooning, the ant with swollen red butt, and of course the wasp with the cockroach. Nature porn, and it's all yours. At radio lab.org. I'm Chad Abramrod. I'm Robert Krollwich. Stay with us. Hi, this is Carl Zimmer. Radio Lab.

is funded in part by the Alfred B. Sloan Foundation, the Corporation for Public Broadcasting and the National Science Foundation. Hi, this is Lulu, leaving you the credits on a lamline. Radio Lab is produced by WNYC and distributed by National Public Radio. Okay, bye. End of message. Hello, I'm Chad Abumrah. And I'm Robert Crilwich.

This is Radio Lab. Our topic today... Parasites. Now, we've met them. They're nice, and we've met them when they're not so nice. I don't know that we've met any nice ones, really. Oh, we haven't? I thought that...

Oh, the blood flukes. Yeah, they were pretty nice. Yeah, they were nice. So, and now the question is, let's just talk about scale. I mean, for the most part, they're irritating and little, and they seem kind of... Invisible. Invisible and sort of off stage. Yeah.

But when you back off a little bit and consider them, you know, in the effects that they have on the world? They're actually these powerful sculptors of monumental narrative. In other words, these are little guys telling very... big stories. In fact, here's an example. Recently, I went to visit a guy named Dixon Despamier. But Columbia University, he's a

parasitologist, and, well, he does a bunch of different things. We ended up talking about... Well, he told me this crazy story. The story I love telling the most... Oh, and before we start, I just want to say one thing. The following two stories contain moments that are a little bit gross.

Just want to make sure you've been warned. The story I love telling the most is how we eradicated hookworm. The story begins in 1908. John D. Rockefeller, Sr. Really rich guy is sitting in his New York office, and he's thinking, How can I make more money selling something to the South?

Yeah, I've got all this money, got all these resources. I just need a new market. In terms of new markets, the South was pretty much untapped, if only those damn Southerners. Just get off their butts and get going. Problem was, they weren't. They weren't getting off their butts. The farms were not operational.

the economic engine was turned off. The economy was in the toilet, and so John D. Rockefeller wanted to know why. Why aren't they producing more? Yep. What's happened to their economic engine? So he thought... I know, I'll form a commission.

Yeah. So he said on a bunch of economists and sociologists and people like that on the original Rockefeller commission. They did everything a commission could possibly do to try to find out why these southern gentlemen were not rising to the occasion.

And they came back, with the following conclusion. Well, we don't exactly know what's wrong, but we think that these people are sick from something because they don't behave like we do. What does that mean? They are slow. Not mentally.

They're slow physically. They're pale. I'll give you an example. Remember the movie Deliverance? Sure. Okay. Remember that little guy that played the banjo? I remember the other scene that we all remember.

We're not going to talk about that. No, we're not. No, we're not. But if you can record. call what that little banjo player looked like. Come on, that way dear. A little wiry-looking guy, but he looked old. Sickly pale.

Yeah, sickly pale and yet an adult. Well, wait a second. That is not a description of all Southerners. No. It was a description of one teeny corner in a... No, but what the commission did say about a lot of these southern people that they encountered is that a lot of them, they just don't look right. They look weak.

They looked wan. They looked kind of, uh, wan. Wan. Wan. They were wan. Pale, lethargic. It's interesting. Wan or wan?

Juan. Huchin. So the thought was that maybe these Southerners had some kind of laziness disease. This is really what a lot of folks thought. But one member on the committee suggested to Rockefeller.

You know what? Perhaps these people are anemic. Anemic. They're anemic, do you say? Yeah, they're anemic. It sounds like a medical problem then. Maybe they're not lazy after all. Maybe they're anemic.

And maybe they're just weak. Next thing you know, Rockefeller puts together another commission, this one with doctors. And he sends them... Back down to the south to find out what the basis for the anemia was.

And not only did they find anemia, but they found a correlation of the anemia with soil types. That's bizarre. Sandy loamy soils, anemia. Hard-packed clay soils? Hmm, no amemia. Sandy-a-lomi soils, good farmland.

Hard-packed clay soils. Not such good farmland. So all the rich farmers were anemic and all the poor farmers were doing okay. And this seemed to be a clue. The incidence of anemia was linked somehow to the soil, maybe, bum-p-bum.

Something was in the soil. That's correct. So somehow they hit upon this idea of looking for hookworm. The hookworm. The hookworm. So they thought, all right, let's run some tests. When they did, big time, they discovered hookworm big time. So the anemia is due to hookworm.

Now the question became, how are these Southerners getting the hookworm and giving it to one another. And a pretty good place to start to look for an answer was their feces. Because if these hookrooms are in you, they're going to come out of you when you go to the bathroom. So they ask these Southerners, when you guys defecate, where do you do it? Most of them said something like this. And I defecate over there. See that tree over there? That's where I defecate. So I defecate over there, but I live over here. Okay, so then the investigators ask the next question. When you go to that tree and do it, do you wear any shoes? Most of them, said, no.

Barefoot, just like everybody else. Because it's comfortable. So clearly these worms are in the feces that are landing near the tree, that are somehow getting into people's feet the next time they come to use the tree. But no one intentionally steps in their own, you know, no one does that. Which meant... Oh, my goodness, it can crawl. Right, so let's find out how far it can crawl.

So what they did, these research, as they built a sandbox, and then they took some hookworm-infested stool... ...and put it right in the middle. Then every day, we'll sample from the stool sample out in the sand in all directions and find larvae and find out how far they can travel. How's that sound? So now we have larvae in the stool, and they began to crawl away from the stool, seeking a victim. On day one, they crawled an entire foot in all directions, but they weren't at two feet.

On day two, my God, they're at two feet. At day three, they're at three feet. I can't believe this. They're crawling a long way. Day four, they crawl to four feet. What about day five? I'm allowed to ask that. And what about day five?

Five feet? No. No. Four feet. That's it. So after four feet, they're what, exhausted? One would assume on day six. they were still at four feet.

And on day seven, they were dead. So how in the world could you deal with this problem when these worms can crawl four feet? It doesn't matter where you defecate. They're going to crawl away from that. And within a four-foot radius of that stool sample, you're going to get hookworm. Unless you do something radical that's never been done before.

they devised a scheme for burying the stool sample into the ground six feet deep. Because if the worms can only make it four feet, well then that's two feet past the point where they die. We call that the outhouse. So the outhouse was invented by exploring the life cycle of hookworm. And in fact, Rockefeller got his wish. The South did rise again. That sounds too easy to me, though. You're telling me that an understanding of hookworm, which created the outhouse,

removed the, quote, Southern laziness disease, and they did rise? It did. And you bring that all back to the hookworm? I do. Really? No, I bring it back to sanitation. Now, to be fair, you can find plenty of other reasons why the South rose again. Air conditioning and highways and universities and stuff like that.

So the hookworm had some help. But what is clear is that when we as a country began to distance ourselves from our own excrement, to put it bluntly, when we stop walking around in our own shi-h-h-h-h-h-h-hick. There were all of these unintended consequences. Salmonella disappeared. Yisdilitka disappeared. Shigella disappeared. Chiaria disappeared. Cryptosperidium.

Anything that's associated with parasites and feces disappeared. Every time we built outhouses and people use them, religiously. Guess what? Their kids can stay in school longer. They could learn more. They got a head faster. Dixon de Svamier is a professor of public health in environmental health sciences and microbiology at Columbia University. Can they make longer titles at that university? He literally wrote the book on parasites. The book is called parasitic diseases. You know it very well. It's soon to be a major motion picture. But now in its fourth edition.

In its fourth edition. And while we're on the subject of hookworms and the glorified, campaign to deworm America. Because this has been a very carefully crafted and intentionally fair program, you have heard the case against hookworms now. Let's turn the coin and say something nice about hookworms. And to begin that discussion, let's go to our reporter Patrick Walters. So, Pat, are you there? Yeah, I'm here, Robert.

So tell us a little bit about this fellow, what's his name exactly? His name is Jasper Lawrence. That's right, Jasper Lawrence. So where is he from? He actually grew up in England. He grew up in this little farm in the southwest corner of England. And it's important to know, I think, before hearing any part of his story, that Jasper has had allergies for pretty much his whole life.

On really bad days, my eyes would swell up so much from pollen or airborne allergens that they would feel like they were swelling shut. I could feel my eyes squeaking in my sockets. It was an enormously uncomfortable feeling. But it was nothing debilitating. They were just allergies. So, you know, he's just like most other people have allergies, just learn to deal with it. You know, you live with it.

But what changed for me in my late 20s, early 30s was my asthma. And at that time I was living in Santa Cruz. I was relatively recently married. We had three cats that had been grandfathered in with the relationship. And I started a landscaping business. I really didn't want to work for someone else. Like someone with allergies starting a landscaping business, that seems kind of unexpected. Stupid is actually the word for it.

And within six months for a year, he starts to notice this really weird barking cough. Was there anything particular that brought this on? No, it was just sitting and breathing. Cats certainly didn't help. Right. And during that period, my asthma got much worse very, very quickly. By the time it was 1996, 1997,

I was seeing specialists having skin allergen tests and cycling through emergency. inhalers, drawing Singular and all these other drugs that were coming on the market. I was being hospitalized at least a couple of times a year. I mean, I looked terrible. I had dark eyes and pale waxy skin. I had that allergic look. It was a really bad time. And he decides in the summer of 2004 to take a vacation. You made this visit to England. Yeah. I took my two daughters back to see my aunt who had raised me. Very early in the visit, I was sitting at her kitchen table. And she asked me if I'd seen a BBC documentary about parasites and their connection with things like asthma, allergies, multiple sclerosis.

And of course I hadn't. But I went upstairs and got on the internet after lunch. And I stayed on the internet until perhaps two in the morning. I didn't stop. And he's reading and reading and the work of all these researchers. Fun study after the next. Japan and epidemiological studies in Africa, animal models of multiple. the sclerosis, this enormous weight of evidence.

That in the developing world, people don't really have asthma or allergies. And what he discovers is that behind all of this to his shock is hookworms. Hookworm? Yeah, hookworms. Yeah, I learned that asthma was 50% less likely in someone who had a hookworm infection. So this sort of just like hits you. Oh, yeah. What did you think when you read that?

Oh, I immediately was determined to obtain hookworm. Immediately. I couldn't wait. So hookworms are these very tiny worms, the size of a little hair. But if you take a microscope and you zoom way in, they have this big circular mouth brimming full of pointy teeth. Very scary to look at. They have these toothy mouth.

so that they can burrow up through your feet, ride through your blood, and eventually end up down in your gut, and start chewing on the inside of your intestines. This guy wants hookworms in his intestines? Absolutely. And so you just Google it? Yeah, hookworms for sale.

I mean, you know, someone's got to be selling them. But, uh, not nothing. I contacted every laboratory supply company in the world and parasitology research centers, and they all said the same thing. no various flavors of no and so I came to the conclusion that I was going to have to go to the tropics

So fast forward a little Jasper is in Cameroon along the coast Quite literally and figuratively The armpit of Africa He's 200 miles north of the equator It's extremely hot He finds a guy to drive him around And so he and his driver

Would go to a village You get out of the car Walk up to these villagers And ask them If they could see the latrine? Just an open area of ground, usually with bushes so people can have a little bit of privacy. And I would go over to the area, remove my shoes, and start walking. The first time I did that, I almost couldn't do it. It must have been 110 degrees that day, 100% humidity. And the stench

and the noise from the insects, it was so repulsive and so disgusting. How many villages, latrines do you think you visited? Between 30 and 40. Jasper spent two weeks there walking around in village latrines, and then he flew home. I got back from Africa in early February, so I was looking at allergy season coming up,

and the day I realized, that I no longer had allergies. It was such a good day. I got into my car, and I started driving, and I had the window down. I felt the breeze blowing across my face. In the past, what that meant was that very quickly my eyes would be itching uncontrollably,

snot and phlegm was going to be pouring out of every orifice in my face, and it didn't happen. It didn't happen. I just started screaming in the car. so happy. And I haven't had an asthma attack since I went to Africa. I no longer have allergies.

The vast majority of the benefit that I've experienced has come from hookworm. What is the hookworm doing? Do you know? Well, so the immune system that we learn about in elementary school is all about, these attack cells that go after foreign invaders and destroy them. Right. And that's a big, important part of the immune system. But if the immune system were allowed to attack and destroy things unchecked, it could kill you. And there are lots of diseases where the primary symptoms are caused by the immune system attacking the body that it's really designed to protect.

Allergies and asthma are just two of these. Some of the more serious ones are like type 1 diabetes, multiple sclerosis Crohn's disease, in which the immune system actually starts attacking the inside of the intestines. They're like 80 of these diseases. 80 of them. And so what scientists have found in lots and lots of mouse studies and in some human studies to this point too

is that once the hookworms get inside the gut and the immune system actually starts attacking somehow, hookworms actually stimulate these cells which just quiet things down. and tell the attack cells to stop attacking. So these are like lullaby cells? Exactly. What lots and lots of scientists think, Joel Weinstock, Tufts Medical Center,

and dozens of others, is that over thousands and thousands of years, hookworms almost developed in tandem with the human immune system. Co-evolution. Parasites living within your body, your immune system changes. So you got to a point where the hookworms could survive safely. The worm gets a home. There's food coming down in the food pipe. And in return, the human immune system gained some kind of positive regulatory advantage.

So that if you had this glitch where your immune system started attacking your own body, the presence of the hookworms would keep things controlled. That's the gift. you do something for the worm, the worm does something for you. So then by that logic, what we in the West, in the richer countries have done stupidly is we have cleaned ourselves up too much and we don't have enough wormies in us. Yeah, this is called... They call it the hygiene hypothesis.

The hygiene hypothesis. That we're not dirty enough. Too clean. We function like rainforests. We're ecosystems and we've entirely eliminated a class of organism that co-evolved with us and our genetic predecessors for millions of years. Now, I don't want to leave the impression that hygiene is bad for you.

People can't go back to living in filth, kids playing in sewage by the riverbank, but in improving our hygiene, we are also excluding organisms that may be important for making us well. So then what does Jasper do about all this? He decides to start a business, selling hookworm to people.

What? You can call him up, and he will literally FedEx a dose of hookworms to your door. How? Sorry, breaking for a second. Pat. Hi, Chad.

Where does he get the hookworm from? This is weird. Jasper gets the hookworm from himself. Could you describe how you go about getting hookworm from your stool into one of your patients? Well, that's a very easy organism to work with it. It just gets up and it walks out of it. So it doesn't take an enormous amount of work. to separate it from the feces.

And then having done that, I repeatedly wash them in solutions of antibiotics to make sure that anything that could live on them is killed. People contact us. We'll have them complete a questionnaire, submit a recent blood test, then we'll ship them a dose and all the materials and equipment and the instructions necessary to infect themselves. To me, is this a safe thing to do? Jasper has done tons and tons of research, but he's not a doctor. The treatment is not approved by the FDA.

That's why I wonder, is there any serious sort of double-blind study trying to figure out whether some safe delivery of hookworm might make sense? Yeah, so one of the guys who was sort of a pioneer in this hookworm research is David Pritchard. I'm Professor David Pritchard. Immunologist and parasitologist. At the University of Nottingham where I study parasites and the wound healing properties of maggots. So we've now got two safety trials under our belts, but we've yet to conduct the trial. to show that therapeutic benefit results from infection with worms. So Pritchard infected himself pretty much just to make sure that it was safe.

What we did was 10 of us in the lab took worms at different doses. We were either given 10, 25, 50 or 100 worms. And then we had to report on the symptoms. And on the back of that study, we determined that 10 worms were tolerated. But Pritchard, when he did this proof of safety study, actually gave himself 50 hookworms. Oh. Which put him out of commission for a while.

Well, I felt pretty bad. I mean, pain in the gut really, you know, you could feel them because they are biting on your tissues. I mean, if you have too many hookworms, they can cause things like diarrhea and the most serious side effect and the side effect that makes them sort of a public health enemy is that they can give you anemia.

So if you have too many, you lose quite a bit of blood to these parasites? Well, you know, if you take too many hookworm, which you're not going to, if you come to worse, The worst thing you're going to get is anemia, but it's not like you wake up one morning and you're drained of blood. Very slow to develop and it's very easy to deal with it. Desper's kind of just gone for it. You know, it's a very sort of like cowboy move.

To the scientific community, I think, they believe that I'm premature. It's not FDA-approved. In offering this to the public. You don't know what it is. You don't know its purity. It's not safe. I've talked to several clients who had really severe allergies and asthma.

They say they've just achieved these great results. And Jasper also says he's seen, success with a few multiple sclerosis patients. And several Crohn's disease patients too. Like, how many people do you think that you have infected? That's about 85 right now. How is business? Business is adequate, but I honestly don't know why.

I don't wake up in the morning with my front garden, 20 deep, with people with ulcerative colitis, Crohn's disease, allergies. I just don't know why I'm not completely buried. The way he sees it. People are scared. Well, they're the people who are coming from a point of view of what they learned in kindergarten about clean drinking water and sewers. To them, worms and parasites are so repulsive that there's nothing good to be said about them. But I can make you better. It's simple, it's cheap. I mean, for God's sake, these organisms fall out my rear end every day, a half a million at a time. The raw material is human excrement, for God's sake. All people have to do is open their minds. Are you really that scared of a little worm? Thanks to reporter Pat Walters. Thanks, Pat.

And to Jasper Lawrence. Into the worms. And to the worms. Thank you, hookworms. Thank you, hookworms. More information about hookworms on our website, and that's the end of this section of Radio Lab. The address, radio lab.org. Yes.

slash hookworm. No, just dot org. Radio Lab will continue in a moment. This is Mike from El Dorado Hills, California. Radio Lab is supported in part by the National Science, Foundation and by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org. Hello, I'm Chad Abumran. I'm Robert Krollwitch. This is Radio Lab. Today's topic, parasites.

Where we have already learned that parasites can be good sometimes. Parasites can, of course, be very bad, that also parasites can affect human behavior, making some of us... Lothargic. Or solving our allergies. Yeah, here's the question to consider, though. Can they not just affect our behavior? Can they control our behavior? Yeah, different question entirely. Yeah, and, you know, we were thinking about this question, you know, in the abstract, doing some research. But then things got kind of real when our producer, Ellen Horn, called in late to work one day. Hey, Lulu, it's Ellen. I just got home from the vet. I've been waiting on chest x-rays and blood work from my cat.

She managed to scratch me with her. This is my cat, moose. Hi, Moose. Big, lovely, affectionate kitty. She's like the sweetest cat you will ever meet. I've met Moose. She's a very sweet cat. She's a darling.

But Moose has digestion problems. And this one day, I had to take her to the vet, and as I was putting her into the kitty carrier, she managed to scratch me with her back claws, and I have, like, a bloody wound on my hand. Her back claws are, like, totally poop covered. So I'm kind of worried. as I am six months pregnant.

The very first thing that they tell you when you get pregnant is stay away from cat poop. So after it happened, I called my midmice. Are you ready for me? She told me to rush right down to her office. So it bled pretty profusely? It did. Wait a second, why? What's so scary about cat poop?

Well, it turns out that cat poop can have in it this tiny parasite. It's called toxoplasma Gandhi. But what is the threat to the baby? If it gets to the baby... It can cause miscarriage. It can cause stillbirth. And it can also cause seizures, blindness. So you're freaking out at this point?

Yeah, I'm kind of freaking out at this point. Small head. My midwife said there's probably nothing to worry about. So she took my blood. This was probably the better arm. And she sent me home. The turnaround time for the test is between two and three days. Okay.

Okay, so I'm looking on the internet at home. I proceed to get myself even more freaked out. A bunch of things about toxoplasmosines. And one of the things that I found was this lecture by Robert Spolski. Now, the example I'm talking about here, he's a neuroscientist who we've had on the show a lot. It has to do with a parasite called toxoplasm. And I just decided that I was going to call him up. Hello?

And ask a few questions. Okay, so what's the deal with toxo? And he proceeded to tell me one of the most amazing feats of mind control that I'd ever heard. What did you tell you? Well, the first thing he told me is that Toxo doesn't actually want to be in me. Yes, it really has wandered off into the wrong county if it winds up in a human. It wants to be inside Moose. For totally mysterious reasons, at least to me, Toxo can only reproduce sexually in the gut of cats.

So it's there in Moose's intestines that the toxoplasma meet and pick up, then they lay eggs. Next, Moose takes a trip to the backyard where she ejects those eggs in her poop. So it's out there now in the cat feces? Step two, says Sapolsky, is that, you know, maybe a week later, a rat will come along and eat the cat poop. Now, Toxo has a problem. It's stuck inside a rat. really wants to be inside a cat. But rats totally freak out whenever they so much as even smell a cat. It's a hardwired aversion. And Toxo's evolutionary challenge now has been to figure

out how to get rodents inside cat's stomachs. Here is where the mind control comes in. And it's kind of hard to believe. But this is what Sapulski says happens. Toxo starts off in the stomach of the rodent. Takes about six weeks to migrate. its way up to the brain. And once it's in there, it finds this particular region called the amygdala, which is like command central for fear and anxiety and terror. All of that. It also finds this other region, kind of right next door, where a very different emotion lives. Sexual arousal. And what toxo seems to be able to do is to somehow cross the wires. This may be some horrifically simplified sound bite, but what I think is going on is that Toxo knows how to make cat urine smell sexy.

What? To rodents, which like totally bizarre, but Toxo makes rodents like the smell of cats. And thus they approach, and thus they're more likely to wind up in the cat's stomach. That's rough. Yeah. In all other ways, the rodent is totally normal. Normal olfaction, normal social behavior. Just hot for cats.

I start to wonder. I really likes the microphone. I love cats. Is it possible that Toxo is wonderful. Is what's been drawing me to cats? That's why we let her put her fur everywhere. I ask him.

Pure speculation, but people who think about this stuff view, it is not just purely speculative. the notion that toxo can produce some sort of attraction to cats and humans, they don't think that's all that crazy. Wait, so you're saying that like the crazy cat lady could be toxoplasma? Well, no one's really studied that yet. Testing, testing, testing. But there are scientists out there that are making the case that toxo can really change you.

Probably the most interesting established link is between toxo and schizophrenia. Are you, Dr. Tori? Nice to meet you. actually been last count, 54 studies on toxoplasma. People with schizophrenia and other psychosis. That's Dr. Fuller-Torri. He works at the Stanley Medical Research Institute that sponsors a lot of these studies. Well, I've been doing research on schizophrenia since the early 70s.

And he thinks there's a link? Yeah. Not a huge effect. A very, very small risk of schizophrenia simply because schizophrenia is very rare. But why would it cause schizophrenia to begin with? Is it trying to cause schizophrenia? You imagine if the toxa was sort of lost in the brain, it thinks it's in a rat brain. Maybe it's just trying to do what it usually does to rats, but in humans it has a very different effect.

And one of the reasons he thinks this might be true, this connection between toxoplasma and schizophrenia, is because of a historical link. The fact that what we now call schizophrenia was quite rare until the late part of the 18th century. And then during the 1800s, schizophrenia increased. very rapidly. Why? This was the first time when we started to keep cats as pets. They first were adopted by the kind of East Greenwich Village types in Paris, the artists. And it was really considered kind of weird, but it's the kind of thing that if you were

an artist or a writer or something like that, you started to do. And then it kind of spread to London, where the writers and artists kept it there. And then starting in about the 1840s, he had started to become a little bit more popular. And then in the 1860s and 70s, it was what called a cat craze. Cats were all over greeting cards. The first cat show was in London in 1970 and in Madison Square Garden in 1880. It became very fashionable to have a cat. We should say, I mean, he'll agree.

At this point, it's just a theory. Okay, but is there any evidence that, Toxo can actually control our behavior like it does with the rats. Well, there are some scientists out there who believe that toxo may affect something more common to all of us. Here's another one of those, give me a break. That's Robert Spolsky again. Science fiction branches through the story. Two different groups independently have seen people who are toxo infected have two to four times the likelihood of dying in car accidents.

Really? Yeah. And I asked him why. Insofar as Toxo makes rodents get really imprudent about cat smells. Maybe Toxo is making all sorts of mammals get imprudent about anything that they're normally skittish about, like your body hurtling through space at a high speed. So in the end, it might be possible. Might be possible that Toxo is guiding our emotions, changing who we are in some basic way.

And if you consider that toxo might just be one of thousands of tiny little parasites inside us, pulling our strings from the inside, well, that thought is pretty creepy. Even if the entire lesson with toxo is a small subset of infected people now have one-half of one percent more likelihood of want to drive really recklessly, even lurking in that one-half of one percent are some serious implications for thinking about free will. We haven't a clue the biology lurking in the background that makes free will seem a little bit suspect. By the way, whatever happened with your test?

Well, this is me with my midwife Barry. And she's giving me the news. What did we find out from the toxo test? That you have had past infection with toxoplasma. Positive. You're positive? Yeah. But my midwife says,

the baby's going to be okay. The baby looked like she's small? Oh, no. She looks like she's a nice size to a little bit on the larger size. So not a baby I'd be worried about. And I believe her. Thanks, Ellen. Sure.

You want to hear more about anything you heard in this hour? Check our website, radio lab.org. Hi there. This is Ellen Horn. I am calling with my cat, Moose, who is just recovering from surgery and doing very well. and we're calling to say that Radio Loud is produced by Lulu Miller and Jada Boomrod. Our staff includes Doran Wheeler, Michael Rayfield.

Ellen Horn and Heperman Jonathan Mitchell and Amanda O'Ronzick. With help from... Jessica Benko, Charles Choi, and Emma Jacobs. Special thanks to Elizabeth Giddens, Pat Walters, Karen Havlich, Lauren Sessions, and Charles Michelet.