Sep 7, 2009


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

Could parasites be the shadowy hands that pull the strings of life? We explore nature's moochers, with tales of lethargic farmers, zombie cockroaches, and even mind-controlled humans (kinda, maybe). And we examine claims that some parasites may actually be good for you.


For transcripts, see individual segment pages.

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JAD ABUMRAD: I thought we would begin by looking backwards at a wonderful moment in the history cinematically of parasites.

ROBERT KRULWICH: A cinematic history of parasites?

JAD: Mhm. Okay, so do you remember that movie—I’m not gonna tell you the name of it—it–starts out—in fact, I have the script right here. Setting: space. 

ROBERT: Okay. 

JAD: Vast empty space. The script continues, “The stars shine cold and remote like the love of God.” Are you imagining this? 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.” 

[MOVIE CLIP, man #1: Ugh I feel dead]

JAD: Here we are in a ship full of astronauts who are tired and dirty.

[MOVIE CLIP, man #2: Anybody ever tell you you look dead.] 

JAD: They’re just palling around and you just get the feeling this is a normal day in their astronaut life, right? Until—there on the computer radar is a disturbance. Some kind of distress signal.

[MOVIE CLIP, woman: A transmission. Out here?]

JAD: They think, ‘We gotta check this out.’ So they trace the signal, eventually, get into a pod, and WOOSH! They find themselves at this abandoned ship. Totally abandoned. It's like a ghost ship. 

[MOVIE CLIP, man #1: I've never seen anything like it.]

[MOVIE CLIP, woman: I wonder what happened to the crew.]

JAD: 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. 


JAD: 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. 

ROBERT: Okay. 

JAD: We'll push this push the spacebar, 

ROBERT: Spacebar. 

JAD: Describe what you see. 

ROBERT: They’re at the table, everyone's dressed.

[MOVIE CLIP, man #1: First thing that I'm gonna do when I get back is to get some decent food.]

ROBERT: They’re all talking—chatting. They’re all having like salad.

JAD: Yeah, they’re just eating and talking. One of the guys gets a little weird, right?

ROBERT: Oh, he's not feeling so good. One of the guys. 

JAD: What's he doing? 

ROBERT: Oh no, he's coughing, coughing, having trouble breathing. He's fallen back onto the table. His chest is heaving—his wrist. Oh my god. He's shaking his head wildly, and he's like flexing all over the table. And something he's like, right—OH! OH, GOD! So there's a red thing, a red, the horrible sneaky thing.

JAD: This is, of course, the classic scene from the original Alien movie. The scene where the little thing bursts out of the guy's chest and like hisses. 

ROBERT: Why did you make me…

JAD: 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 its effect on a lot of people and I think I know why. 

ROBERT: What do you know? 

JAD: It's not that the little creature is disgusting, which it is. It's that it was there all along…

ROBERT: Sitting there.

JAD: 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 wiggling around doing more or less what that alien was doing and I can't even see them in you. Ugh! I can't even talk about it.

ROBERT: So let’s not. Today's subject on Radiolab will be flowers in meadows coming up after this.

[Birds tweeting]

[Sudden hissing record scratch and hissing sound]

JAD: No, we're not doing that. We're doing—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.

ROBERT: What is a parasite, precisely?

JAD: A moocher. Just to sort of slide us in, get us into the mood.

ROBERT: I'm already not in the mood. 

JAD: We thought we would get things started.

CARL ZIMMER: Maybe I'll just move this.

JAD: Well, there really is no other way to start a show on parasites except with this guy. 

ROBERT: You should introduce yourself.

CARL ZIMMER: My name is Carl Zimmer.

JAD: Carl's a science writer. Yeah, and parasites had been on his radar ever since he was a little boy.

CARL ZIMMER: I grew up on a little farm and my mother would raise tomatoes, sometimes in her 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 I was eating my mother's tomatoes. And they were growing…

JAD: Growing inside the caterpillar. 

CARL ZIMMER: And then finally when they were ready, they—they came out and only then did their host die. 

JAD: And when he finally found out that that is what was happening inside those fuzzy white bumps.

CARL ZIMMER: This profound situation…

JAD: This whole universe of babies growing into adolescence.

CARL ZIMMER: That's when I guess I sort of got very hooked.

JAD: 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.

CARL ZIMMER: People have been dismissing parasites for a long time calling them degenerates. And I would argue that parasites are not degenerate. They have gained the ability to live inside 3,4,5, 6 different species.

ROBERT: 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!

CARL ZIMMER: I think I'm a defender of all neglected and put upon species out there.

JAD: 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…

ROBERT: Yeah, it's not independent. 

JAD: Right? So when you say it's not degenerate, what it—why would you say that?

CARL ZIMMER: Well, let's start with saying it's not independent. Are any of us independent?

ROBERT: Kit Carson? 

CARL ZIMMER: Have you stripped all the bacteria out of Kit Carson, Kit Carson would get very sick. 

ROBERT: Daniel Boone, on the other hand, now there's a guy independent alone in the woods.

CARL ZIMMER: What does Daniel Boone eat?

ROBERT: I guess Daniel Boone eats pigeon, like the rest of us, 

JAD: What's your point, Carl Zimmer?

CARL ZIMMER: My point is that Daniel Boone eats meat. He ate bread, which came from plants.

JAD: I guess it’s a question of degrees, though. We’re not living inside the intestinal tract of some other creature.

CARL ZIMMER: 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. 

ROBERT: No Carl. No Carl. If you are a creature that lives off someone else's vitality…

JAD: Cheaters should be another way of putting it.

CARL ZIMMER: But listen, can you appreciate that…

JAD: I'm gonna—just gonna cut this short right here. Carl says… 

CARL ZIMMER: No, no, no, they're amazing!

JAD: Time and time again. He says no…


JAD: And the argument went on. 

CARL ZIMMER: I’m still waiting to hear about how you are able to photosynthesize through it.

ROBERT: It’s true. It’s true I eat plants, but like go about it in a mental way. [crosstalk]

CARL ZIMMER: Until you can tell me. [crosstalk]

CARL ZIMMER:You can't even do it yourself!

JAD: 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 gonna do just to be fair and square about this, we’re gonna bring in an independent moderator—Lulu!

LULU: Yeah?

JAD: You're gonna be the moderator. Yeah, get that mic. You're gonna be the moderator and you listening right now, we will leave it to you your decision in this one lightning round of. 

LULU: Shall I do it? 

JAD:  Yeah.

LULU: Parasites: Are they evil or are they awesome? Starting with number one, the parasitic wasp.

CARL ZIMMER: There are probably 200,000 species of parasitic wasps out there.

JAD: Big wasp? Small wasp?

CARL ZIMMER: They're generally pretty tiny. 

LULU: And they go after all sorts of things. 

CARL ZIMMER: Some will lay…

LULU: And they go after all sorts of things. Carl’s caterpillar, spiders or the one Carl's gonna tell us about…

CARL ZIMMER: This particular wasp is called Ampulex Compressa 

LULU: Goes after…

CARL ZIMMER: Cockroach.

LULU: And for those of you who never thought you'd feel sorry for a cockroach, keep listening.

CARL ZIMMER: So what it does is it flies around, and it looks for a cockroach, and once it finds that cockroach, it lands.

LULU: And then the fight begins. They tumble back and forth around around until finally the wasp somehow manages to arch its back around the body of the cockroach…

CARL ZIMMER: and stings it.

LULU: Zzzz! Right in the belly. The cockroach twitches for a second and then falls. 

CARL ZIMMER: Boom! The cockroach is paralyzed.

LULU: Now the wasp takes its time. Repositions itself, puts its butt up right near the cockroaches head

CARL ZIMMER: And delivers a second sting. The stinger actually threads its way to a particular spot in the brain.

LULU: And this does something odd. Moments later…

CARL ZIMMER: the cockroach recovers, sort of stands up and can walk again…

LULU: But something is wrong. Very wrong. 

CARL ZIMMER: It just stands there. 

LULU: Like, “I’m awake but…”

CARL ZIMMER: It can't run away. 

LULU: “I can’t move.” 

CARL ZIMMER: It has essentially lost its will

JAD: What does that mean? 

ROBERT: It's a puppet.

[carnival music in]

CARL ZIMMER: 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. 

JAD: But how does it grab—with what does it grab?

CARL ZIMMER: I believe with its mouth?

LULU: Imagine a tiny wasp guiding a cockroach across the desert floor…

CARL ZIMMER: Like a dog on a leash.

LULU: And so it leads it down, down, down.

CARL ZIMMER: Down into a little burrow it made and the cockroach says, “Okay, where do you want to go?”

[carnival music out]

LULU: Then, once the wasp has the roach in the burrow.

CARL ZIMMER: It lays its eggs on the underside of the cockroach.

LULU: So now you've got this drugged roach sitting on top of some wasp eggs, and then the wasp goes…

CARL ZIMMER: Out and it seals the burrow.

ROBERT: It buries the cockroach alive? Or it just puts him in a little cell?

CARL ZIMMER: It's in a little chamber. It doesn't want to kill the cockroach because this cockroach is gonna feed, it's you know, it's young. Yeah. So then the eggs hatch. [egg cracking sound] And then they drill inside. [drill sound] The cockroach are still just sitting there.

JAD: How's it staying alive at this point?

CARL ZIMMER: Well, parasites are very careful. You know, they won't eat vital organs that will kill it.

LULU: Instead, Carl says they just feast on the extra stuff.

CARL ZIMMER: There's a lot of stuff inside of a cockroach, a lot of fluid just floating around.

ROBERT: Bits of Wonder Bread, essence of skin, old hair…

CARL ZIMMER: That you can just feed on any the host stays alive. 

JAD:  Wow. And then what happens?

LULU: Eventually the little baby wasp larva grows up…

CARL ZIMMER: Inside the cockroach and develops into an adult…

LULU: And then one day…

CARL ZIMMER: The wasp eats its way up a hole out of the out of cockroaches body shakes off its wings and flies off.

JAD: And then the roach dies

CARL ZIMMER: Then the roach dies. 

JAD: But only then.


JAD: That to me sounds like the purest description in nature of evil that I can imagine. Wouldn't you agree?

CARL ZIMMER: Well, Darwin certainly said that God should not be personally blamed for having created parasitic wasps.

LULU: But if you ask Carl, he’ll have you think about that moment—the moment where the wasp stings the brain.

CARL ZIMMER: A parasitic wasp can attack a cockroach can insert its stinger into one specific part of the cockroaches brain and inject a precise little cocktail of drugs. That then turns the cockroach into its slave. I know that that wasp didn't get a PhD in neurobiology…

LULU: And yet it has performed a kind of brain surgery.

CARL ZIMMER: Very precisely in a very elegant way.

JAD: Or evil might be the other way—but can go ahead.

CARL ZIMMER: But there's a complexity there that you can't deny.

LULU: Or can you? We leave it to you. Bringing us to example number two: parasitic nematode.

CARL ZIMMER: I mean, here’s—here's another example that I actually was looking at today.

JAD: You’re holding your computer up to the glass.

LULU: And on the screen is a big black ant. 

JAD: It looks like it's carrying a cherry right? 

LULU: A cherry that's about twice the size of the ant.

CARL ZIMMER: That red cherry is actually parasites inside of the ant making it look like a red cherry.

JAD: What part of the ant is that is that—it's butt? 

CARL ZIMMER: Essentially, yeah. 

JAD: Wait a second, is it—it looks like it's sticking it's big, red butt up into the air.

CARL ZIMMER: Yeah, their behavior has changed so they they waggle around their—their—their tail as it were.

LULU: Now why on earth would a parasite turn on ants but red and then make it stick its butt up into the air? Well, CAWWWW!

CARL ZIMMER: Let's say you put an ant down that has this bright red rear end and an ordinary ant in front of a bird. The birds gonna go for that red ant very quickly.

JAD: Because it thinks it's a berry.

CARL ZIMMER: Yeah and then it's going to swallow this little package full of nematode eggs.

ROBERT: So that's the way the nematode eggs get into the sky. They buy their airplane tickets by advertising themselves as berries.

JAD: Yes. What's the benefit of being in the air?

CARL ZIMMER: Well, the the only place that this parasite can reproduce is inside the bird.

LULU: And how better to spread your seed far and wide than to drop from the sky? [whistles]

CARL ZIMMER: With the bird droppings.

JAD: That’s f*cking brilliant. That’s f*cking brilliant. I mean look at the it's red a** is up in the air. 

CARL ZIMMER: Yeah. It's amazing. 

JAD: It's like how can a stupid little thing be so brilliant.

CARL ZIMMER: Because they're not degenerates.

[group laughs]

JAD: But they’re still cheating!

LULU: And then just to bring his point home…

CARL ZIMMER: Just pick a common one.

LULU: Carl offered up his third and final example number three: blood-flukes.

CARL ZIMMER: Blood-flukes are related to flatworms, tapeworms. SO their eggs start out in the water—fresh water in Africa, Asia, parts of South America.

LULU: In the first part of their life they go into a snail and they come back out into the water and

CARL ZIMMER: They're swimming around and they start looking for a human.

ROBERT: So imagine a foot, going into the shallow end of the pond, I see toes. I see bottom a foot. I see ankle/

CARL ZIMMER: Well, if you’re a blood-fluke, you don't see anything, you don't have eyes.

LULU: But eventually you find a foot, secrete a little enzyme…

CARL ZIMMER: 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.

ROBERT: A mate? 

JAD: So there's sex. So there's a male and female? So you're saying… 

CARL ZIMMER: Sure, they're animals. 

JAD: They're animals? I would have never called them animals, it’s interesting you say that. That's a whole other topic, I guess. 

CARL ZIMMER: Alright, so the a female is very thin. It's sort of a standard issue worm kind of thing. But the male is very strange. It's it's kind of like a like a canoe. It's got a trough down the middle, and at one end, it's got a giant sucker.

ROBERT: Should we urge some of our listeners to tune away at this point because but what’s about to happen may not be acceptable in family hour?

CARL ZIMMER: Actually, blood-flukes are fairly monogamous and loyal. So you know, if you're looking for—for animals to reinforce your family values, blood-flukes are pretty good. 

LULU: And eventually, two blood-flukes find their way toward each other. And the male does a sort of courtship.

CARL ZIMMER: For whatever reason, the female says, “Yes, I accept your courtship.” The female joins the male—fits in the trough. 

JAD: Oh, so it's like a groove, the female goes in and occupies the groove.

CARL ZIMMER: Right now this isn’t just—this isn't mating. This is way beyond mating. The males will feed the female for starters. And they will

LULU: Stay this way for a…

CARL ZIMMER: Long, long time.

JAD: Really? 


JAD: Like days? 


JAD and ROBERT: Years!? 


ROBERT: Oh my god! Years in human or years to them? 

CARL ZIMMER: Just years, years, years, years. 

ROBERT: Years, like the earth going around the sun kind of years. 


LULU: In fact, there have been cases where people show up at their doctor’s feeling awful. The doctor does some tests and says…

CARL ZIMMER: 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.”

JAD: What? 40? Four, zero? 

CARL ZIMMER: 40 years ago. Yeah, and the reason that they're getting sick is that these male and female blood fluids are still together, making eggs.

LULU: And Carl's literally glowing when he says this.

CARL ZIMMER: 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 their life together.

LULU: And so our story concludes the image of two blood-flukes spooning in your veins for nearly half a century.

JAD: Gotta hand it to him. He's good.

ROBERT: Carl, you mean? 

JAD: Yeah.


CARL ZIMMER: And there is a species of tapeworm that's gonna be named after me.

JAD: No kidding? 

ROBERT: Really? Wow.

CARL ZIMMER: It's not quite as much of an honor as you think at first. I was talking with a parasitologist, and she was telling her fellow experts about how she was gonna 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—she's a little round and it's a kind of a round tapeworm that I named her after” and you suddenly discover there are a lot of tapeworms to be named. 

JAD: How many is a lot?

CARL ZIMMER: Tens of thousands of species of tapeworms.

JAD: Wow. So they got us beat many times over.

CARL ZIMMER: I once saw estimates that if you took all the viruses in the ocean and you stick them end to end, how far would it go? And it was many light years way beyond our galactic neighborhood.

ROBERT: In other words, there are more cheats than there are honest people—honest creatures on earth. 


[music in]

JAD: Should we—should go to break?

ROBERT: 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-flukes spooning, the ant with the swollen, red butt and of course the wasp with the cockroach.

ROBERT: Nature porn and it's all yours.


[Music swells. Music out.]

JAD: I'm Jad Abumrad.

ROBERT: I’m Robert Krulwich.

JAD: Stay with us.

[phone beep]

CARL ZIMMER: Hi, this is Carl Zimmer. Radiolab is funded in part by the Alfred P. Sloan Foundation, the Corporation for Public Broadcasting and the National Science Foundation.

LULU: Hi, this is Lulu, leaving you the credits on a landline. Radiolab is produced by WNYC and distributed by National Public Radio. Okay. Bye!

[Automated voice: End of message]

JAD: Hello, I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich,

JAD: This is Radiolab. Our topic today…

ROBERT: Parasites 

JAD: Parasites.

ROBERT: Now we've met some that are nice. And we've met some that are not so nice.

JAD: I don't know that we've met any nice ones, really.

ROBERT: We haven’t? I thought—I thought that…

JAD: Oh the blood-flukes!

ROBERT: Yeah! 

JAD: Oh! Yeah, they were pretty nice. They were nice.

ROBERT: So 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…

JAD: Invisible.

ROBERT: Invisible and sort of off stage. But when you back off a little bit and consider them, you know, and the effects that they have on the world.

JAD: They are actually these powerful sculptors of monumental narrative.

ROBERT: Well, there was these little guys telling very big stories.

JAD: In fact, here's an example: Recently, I went to visit a guy named Dickson Despommier up at Columbia University. 

[A person walks up steps and knocks on a door. The door opens.]

JAD: He's a parasitologist. Well, he does a bunch of different things we ended up talking about. Well, he told me this crazy story.

DICKSON DESPOMMIER: The story I love telling the most. 

JAD: 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.

DICKSON DESPOMMIER: The story I love telling the most is how we eradicated hookworm.

JAD: The story begins in 1908, 

DICKSON DESPOMMIER: John D. Rockefeller, 

JAD: A really really rich guy is sitting in his New York office. And he's thinking…

DICKSON DESPOMMIER: How can I make more money selling something to the South?

JAD: 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…

DICKSON DESPOMMIER: Would just get off their butts and get going. 

JAD: Problem was, they weren't. They weren't getting off their butts.

DICKSON DESPOMMIER: The farms were not operational. The economic engine was turned off. 

JAD: The economy was in the toilet. 

JAD: And so John D. Rockefeller wanted to know why. Why aren't they producing more? 

DICKSON DESPOMMIER: Yep. What's happened to their economic engine? 

JAD: So he thought…

DICKSON DESPOMMIER: I know I'll form a commission. 

JAD: Yeah. 

DICKSON DESPOMMIER: So he said, 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, we don't exactly know what's wrong. But we think that these people are sick from something because they don't, they don't behave like we do.”

JAD: What does that mean? They are slow.

DICKSON DESPOMMIER: Not mentally. They're slow, physically. They're pale. I'll give you an example. You remember the movie Deliverance? 

JAD: Sure. 

[crickets and banjo plucking]

DICKSON DESPOMMIER: Okay. Remember that little guy that played the banjo?

JAD: I remember the other scene that we all remember that we’re not gonna talk about. 

DICKSON DESPOMMIER: We're not. No, we're not. But if you can recall what that little banjo player looked like. Little, wiry looking guy, but he looked old. 

JAD: Sickly pale? 

DICKSON DESPOMMIER: Yes. sickly pale and yet an adult. 

ROBERT: Wait a second. Wait a second. That wasn’t—that is not a description of all Southerners, it’s a description of one teeny corner.

JAD: No! No, but what the commission did say about a lot of the Southern people that they encountered is that a lot of them, they just don't look right. They look weak. They look wane. They look kind of—wane? Wan? 

ROBERT: Wane. 

JAD: Wane? 

ROBERT: They were wane. 

JAD: Pale, lethargic.

ROBERT: It's interesting wane or wan? 

JAD: Wane. 

ROBERT: You choose.

JAD: So the thought was maybe these Southern has had some kind of laziness disease. This is really what a lot of folks thought. Then one member on the committee suggested to Rockefeller, “You know what, perhaps these people are anemic.”

DICKSON DESPOMMIER: “Anemic? They're—they're anemic, you say? Yeah, they're anemic. Sounds like a medical problem then. Maybe they're not lazy, after all. Maybe they're anemic and maybe they're just weak.”

JAD: Next thing, you know, Rockefeller puts together another commission, this one with doctors and he sends them…

DICKSON DESPOMMIER: 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. Hardpack clay soils: no anemia. Sandy loamy soils: good farmland. Hardpack clay soils: not such good farmland. So all the rich farmers were anemic and all the poor farmers were doing okay.

JAD: And this seemed to be a clue. The incidence of anemia was linked somehow to the soil, maybe—Bum! Bum! Bum!—


JAD: Something was in the soil. 

DICKSON DESPOMMIER: That's correct. So somehow they hit upon this idea of looking for hookworm.

[banjo music]

JAD: The hookworm!


JAD: So they thought, “Alright let's run some tests.”

DICKSON DESPOMMIER: When they did, big time they discovered hookworm big time. So the anemia is due to hookworm.

JAD: Now the question became how are the 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 the silkworms are in you, they're gonna come out of you when you go to the bathroom. So they asked the Southerners, “When you guys defecate, where do you do it?” Most of them said something like this…

DICKSON DESPOMMIER: “I defecate over there. See that tree over there, that's where I defecate. So I defecate over there, but I live over here.

JAD: Okay, so then the investigators asked the next question, “When you go to that tree and do it, do you? Do you wear any shoes?” Most of them said, No.

DICKSON DESPOMMIER: Barefoot just like everybody else, because it's comfortable.


JAD: So clearly, these worms are in the feces that are landing near the tree and 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…

DICKSON DESPOMMIER: Oh, my goodness! Oh, my goodness, it can crawl. Right. So let's find out how far it can crawl.

JAD: So what they did these researchers is they built a sandbox, and then they took some hookworm infested stool.

DICKSON DESPOMMIER: And put it right in the middle. Then every day, we will 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 crawl 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 were three feet. “I can’t believe it! They're crawling a long way!” Day four, they crawl to four feet.

JAD: And on day five?

DICKSON DESPOMMIER: I am allowed to ask. And what about day five?

JAD: Five feet? 


JAD: No? Four feet?


JAD: So after four feet there was exhausted?

DICKSON DESPOMMIER: 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? They can crawl four feet, it doesn't matter where you defecate, they're gonna crawl away from that, and within a four foot radius of that stool sample, you're gonna 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.

JAD: Because if the worms can only make it four feet, well then that's two feet past the point where they die.

DICKSON DESPOMMIER: 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.

JAD: That sounds too easy to me, though. You're telling me that that an understanding of hookworm, which created the outhouse removed the quote, Southern laziness, disease and they did rise? And you bring that all back to the hookworm?


JAD: Really? 

DICKSON DESPOMMIER: No, I bring it back to sanitation.

JAD: Now to be fair, you can find plenty of other reasons why the South rose again.

ROBERT: Air conditioning and highways and university. 

JAD: Right.

ROBERT: And stuff like that. 

JAD: 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 stopped walking around in our own sh*t there were all of these unintended consequences.

DICKSON DESPOMMIER: Salmonella disappeared. Histolytica disappeared. Shigella disappeared. Cholera disappeared. Giardia disappeared Cryptosporidium. Anything that's associated with parasites and feces disappeared. Every time we build outhouses [toilet flushes] and people use them religiously, guess what? Their kids can stay in school longer. They could learn more. They got ahead faster.

[music in: banjo music mixed with toilet flushing sounds]

JAD: Dickson Despommier is a Professor of Public Health and Environmental Health Sciences in Microbiology at Columbia University.

ROBERT: Can they make longer titles at that university?

JAD: He literally wrote the book on parasites.

[banjo music out]

ROBERT: The book is called “Parasitic Diseases.” You know it very well. It's soon to be a major motion picture and it’s now in its fourth edition.

JAD: In its fourth edition. 

ROBERT: And while we're on the subject of hookworms and the glorious 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 hookworm. And to begin that discussion, let's go to our reporter Patrick Walters. So, Pat, are you are you there?

PAT WALTERS: Yeah, I'm here, Robert.

ROBERT: So tell us a little bit about this fellow. What's his name? Exactly.

PAT WALTERS: His name is Jasper Lawrence.

JASPER LAWRENCE: That’s right, Jasper Lawrence.

ROBERT: So where's he from?

PAT WALTERS: He actually grew up in England, he grew up in this little farm in the southwest corner of England. 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.

JASPER LAWRENCE: 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.

PAT WALTERS: But it was nothing debilitating. 

JASPER LAWRENCE: They were just allergies. 

PAT WALTERS: And so you know, he just like like most other people have allergies just learned to deal with it. 

JASPER LAWRENCE: You know, you live with it. 


JASPER LAWRENCE: What changed for me in my late 20s, early 30s was my asthma. 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.

PAT WALTERS: I think someone with allergies, starting a landscaping business that seems kind of unexpected.

JASPER LAWRENCE: And stupid is actually the word for it. And within six months or a year…

PAT WALTERS: He starts to notice…

JASPER LAWRENCE: This really weird barking cough.

PAT WALTERS: Was there anything particular that brought this on? 

JASPER LAWRENCE: No, it was just sitting and breathing. Cats certainly didn't help. 


JASPER LAWRENCE: 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 trying Singulair and all these other drugs that were coming on the market. I was being hospitalized 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.

PAT WALTERS: And he decides in the summer of 2004 to take a vacation.

PAT WALTERS: You made this visit to England. 

JASPER LAWRENCE: 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 and allergies, multiple sclerosis. And of course I hadn't, but I went upstairs and got on the internet [keyboard clicks] after lunch, I've stayed on the internet until perhaps two in the morning.

[music in]

JASPER LAWRENCE: I didn’t stop.

PAT WALTERS: And he's reading and reading. 

JASPER LAWRENCE: And the work of all these research.

PAT WALTERS: One study after the next.

JASPER LAWRENCE: In Japan. Epidemiological studies in Africa. Animal models in multiple sclerosis. This enormous weight of evidence…

PAT WALTERS: 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.

ROBERT: Hookworm?

PAT WALTERS: Yeah, hookworm. 

JASPER LAWRENCE: Yeah, I learned that asthma was 50%, less likely in someone who had a hookworm infection. 

PAT WALTERS: So this sort of just like hits you?


PAT WALTERS: What did you think when you when you read that?

JASPER LAWRENCE: Oh, I immediately was determined to obtain hookworm, immediately. I couldn't wait.

PAT WALTERS: So hookworms are these very tiny worms the size of a little hair, but if you take a microscope and use zoom way in, have this big circular mouth brimming full of pointy teeth. Very scary to look at. They have these toothy mounds so that they can burrow up through your feet, right through your blood and eventually end up down in your gut and start chewing on the inside of your intestines.

ROBERT: This guy wants hookworms in his intestines?

PAT WALTERS: Absolutely. 

PAT WALTERS: And so you just Google it?

JASPER LAWRENCE: Yeah, hook hook worms for sale. I mean, you know, someone's got to be selling them, but no—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.

PAT WALTERS: So fast forward, a little Jasper is in Cameroon, along the coast.

JASPER LAWRENCE: Quite literally, and figuratively the armpit of Africa.

PAT WALTERS: He's 200 miles north of the equator. It's extremely hot. He finds a guy to drive them around. And so he and his driver would go to a village…

JASPER LAWRENCE: Get out of the car…

PAT WALTERS: Walk up to these villagers and ask them if they could see the latrine.

JASPER LAWRENCE: Just an open area of ground, usually with bushes so people can have a little bit privacy. And I would go over to the area, remove my shoes and start walking. The first time I did that, I—I almost couldn't do it. It was—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.

[sound of footsteps through wet ground]

PAT WALTERS: How many villages latrines do you think you visited?

JASPER LAWRENCE: Between 30 and 40.

PAT WALTERS: Jasper spent two weeks there, walking around in village latrines, and then flew home.

JASPER LAWRENCE: 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 that was such a good day. I got into my car. And then I started driving. And I had the window down, and 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. I was so so happy. 

[music in: repetitive beat with the word “hookworm” repeated]

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.

[music out]

ROBERT: What is the hookworm doing? Do you know?

PAT WALTERS: Well, so the immune system that we learned about in elementary school is all about like these attacks 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 this diseases. 

ROBERT: Eighty!

PAT WALTERS: 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. 

[music in: lullaby music]

PAT WALTERS: Somehow, hookworms actually stimulate these cells, which just quiet things down and tell the attack cells to stop attacking.

ROBERT: So these are like lullaby cells?

[music out]

PAT WALTERS: Exactly. What lots and lots of scientists think, Joel Weinstock—

JOEL WEINSTOCK: Joel Weinstock, Tufts Medical Center.

PAT WALTERS: And dozens of others, is that over…

JOEL WEINSTOCK: 1000s and 1000s of years…

PAT WALTERS: Hookworms almost developed in tandem with the human immune system.

JOEL WEINSTOCK: Coevolution. Parasites living within your body, your immune system changes…

PAT WALTERS: So you got to a point where the hookworms could survive safely.

JOEL WEINSTOCK: The worm gets a home, there's food coming down the food pipe and in return…

PAT WALTERS: The human immune system, gains some kind of 

JOEL WEINSTOCK: Some form of… 

PAT WALTERS: Positive regulatory… 

JOEL WEINSTOCK: advantage. 

PAT WALTERS: So that if you had this glitch where your immune systems started attacking your own body, the presence of worms will keep things…

JOEL WEINSTOCK: Controlled. And that's the gift you do something for the worm, the worm does something for you.

ROBERT: So by that logic, what we in the West—in the richer countries have done stupidly as we have cleaned ourselves up too much and we don't have enough wormies in us… 

PAT WALTERS: Yeah, this is called…

JOEL WEINSTOCK: They call it the hygiene hypothesis. 

ROBERT: The hygiene hypothesis that we're not dirty enough. 

PAT WALTERS: Too clean.

JASPER LAWRENCE: We function like rain forests. We’re ecosystems and we've entirely eliminated a class of organism that coevolved with us and our genetic predecessors for millions of years.

JOEL WEINSTOCK: Now, I don't want to leave the impression that hygiene is bad for you. People can't go back to living and filth kids playing and sewage by the riverbank, but in improving our hygiene, we are also excluding organisms that may be important for making us well.

ROBERT: So then what does Jasper do about all this?

PAT WALTERS: He decides to start a business, selling hookworm to people. 

ROBERT: How!? 

PAT WALTERS: You can call him up and he will literally FedEx a dose of hookworms to your door. 

JAD: Sorry, if I can just break in for a second. Pat…


JAD: Where does he get the hookwork from?

PAT WALTERS: This is weird. Jasper gets the hookworm from himself. 

PAT WALTERS: Could you describe how you go about getting hookworm from your stool into one of your patients?

JASPER LAWRENCE: Well, it's very easy organism to work with it. It just—it 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 I having done that, I’ve repeatedly washed 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 and 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.

ROBERT: Wait is this a safe thing to do?

PAT WALTERS: Jasper—Jasper has done tons and tons of research, but he's not a doctor. The treatment is not approved by the FDA.

ROBERT: I wonder is there any serious sort of double blind study, trying to figure out whether some safe delivery of hookworm might make sense?

PAT WALTERS: Yes. And so one of one of the guys who was sort of pioneer in this hookworm research is David Pritchard.

DAVID PRITCHARD: I’m Professor David Pritchard.

PAT WALTERS: An immunologist and  parasitologist…

DAVID PRITCHARD: 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 trials to show the therapeutic benefit results from infection with worms.

PAT WALTERS: So Pritchard infected himself pretty much just to make sure that we're safe.

DAVID PRITCHARD: 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. Along the back of that study, we determined the 10 worms were tolerated.

PAT WALTERS: But Pritchard when he did this proof of safety study actually gave himself 50 hookworms, which put him out of commission for awhile.

DAVID PRITCHARD: Well, I felt pretty bad. I mean, pain in the gut, really, you know, you can feel them, because they are biting on your tissues.

PAT WALTERS: 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.

[banjo music]

DAVID PRITCHARD: So if you have too many, you—you lose quite a bit of blood to these parasites.

JASPER LAWRENCE: Well, you know, if you take too many hookworm—which you're not going to—if you come to us, the worst thing you're gonna 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.

PAT WALTERS: Jasper is kind of just gone for it. You know, it's a very sort of like cowboy move.

JASPER LAWRENCE: To the scientific community, I think they believe that I'm premature…

JOEL WEINSTOCK: It's not FDA approved. 

JASPER LAWRENCE: In offering this to the public. 

JOEL WEINSTOCK: You don't know what it is you don't know its purity. It's not safe.

PAT WALTERS: But I've talked to several clients who had really severe allergies and asthma. They say they've just achieved these great results. And desperate also says he seen success with with a few multiple sclerosis patients and several Crohn's disease patients too. 

PAT WALTERS: Like how many people do you think that you have infected?

JASPER LAWRENCE: It's about 85 right now.

PAT WALTERS: How is business? Is it everything…?

JASPER LAWRENCE: Businesses 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.

PAT WALTERS: The way he sees it. People are scared. 

JASPER LAWRENCE: Well, they're the people who are coming from the 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 sakes, 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?

[slurping sound]

ROBERT: Thanks to reporter Pat Walters… 

JAD: Thanks, Pat. 

ROBERT: And to Jasper Lawrence and to the worms 

JAD: And to the worms! 

ROBERT: Thank you, hookworm. 

JAD: Thank you hookworms. 

ROBERT: For more information about hookworms on our website and that's the end of this section of our…

JAD: Well don’t you want to see the address. 


JAD: Slash hookworm. No just .org. Radiolab will continue in a moment. 

MIKE: This is Mike from El Dorado Hills, California. Radiolab 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


JAD: Hello, I'm Had Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: This is radio lab. Today's topic, parasites.

ROBERT: Where we have already learned that parasites can be good, sometimes. Parasites can, of course, be very bad. But also parasites can affect human behavior making us—some of us a little…

JAD: Lethargic 

ROBERT: Or solving our allergies.

JAD: And here's another question to consider though: Can they not just affect our behavior, can they control our behavior? 

ROBERT: A different question entirely. 

JAD: Yeah, and you know, we were 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 Horne called in late to work one day.

ELLEN HORNE: [over the phone] Hey, Lulu, it's Ellen. I'm just got home from the vet. I've been waiting on chest X rays. blood work from my cat. [Meow!] She managed to scratch me…

ELLEN: This is my cat moose. [Cat purrs loudly] Big lovely affectionate kitty. She's like the sweetest cat you will ever meet.

JAD: I've met Moose. 

ELLEN: She’s a very sweet cat. 

JAD: A darling. 

ELLEN: [Cat purrs] But Moose has digestion problems. [cat meows] And this one day, I had to take her to the vet. And as I was putting her into the kitty carrier…

ELLEN: [over the phone] 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 pooped covered, so I'm kind of worried. I have—I am six months pregnant. 

ELLEN: 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 midwife.

[sounds of bags shuffling]

ELLEN: Are you  ready for me?

ELLEN: She told me to rush right down to her office. 

MIDWIFE: So it bled pretty profusely? 

ELLEN: It did

[record scratch]

JAD: Wait a second, why? What's so scary about cat poop?

ELLEN: Well, it turns out that cat poop can have in it this tiny parasite. It’s called Toxoplasma gondii. 

ELLEN: So what is the threat to the baby? 

ELLEN: If it gets to the baby… 

MIDWIFE: It can cause miscarriage. It can cause stillbirth. [phone rings] And it can also cause seizures, blindness.

JAD: So you're freaking out at this point?

ELLEN: Yeah, I'm kind of freaking out at this point.

MIDWIFE: Small cranium, small head.

ELLEN: But my midwife said there's probably nothing to worry about. So she took my blood


ELLEN: That's probably the better arm. 

ELLEN: And she sent me home.

MIDWIFE: The turnaround time for the test is between two or three days.

ELLEN: Okay, so I'm looking on the internet…

ELLEN: At home, I proceed to get myself even more freaked out 

ELLEN: A bunch of things about Toxoplasmosis. 

ELLEN: And one of the things that I found was this lecture by Robert Sapolsky 

[CLIP, Lecture, Robert Sapolsky: Now the example I'm talking about here….] 

ELLEN: He's a neuroscientist who we've had on the show a lot.

[CLIP, Lecture, Robert Sapolsky: It has to do with a parasite called Toxoplasma.]

ELLEN: And I just decided that I was gonna call him up and ask…

[phone rings]


ELLEN: A few questions. 

ROBERT SAPOLSKY:  Okay, so what's the deal with Toxo?

ELLEN: When he proceeded to tell me one of the most amazing feats of mind control I'd ever heard.


JAD: What did he tell you?

ELLEN: Well, the first thing he told me is that Toxo doesn't actually want to be in me.

ROBERT SAPOLSKY: Yes, t 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.

[cat meows]

ELLEN: So it's there in Moose’s intestines that the Toxoplasma meet and hook up. Then they lay eggs. Next Moose takes a trip to the backyard, where she ejects those eggs in her poo.

ROBERT SAPOLSKY: So it’s out there now it the cat feces. 

ELLEN: 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 but it really wants to be inside a cat. But rats totally freak out whenever they so much as even smell cat.

ROBERT SAPOLSKY: It’s—it's a hardwired aversion. Toxo’s evolutionary challenge now has been to figure out how to get rodents inside cat stomach’s.

ELLEN: Here is where the mind control comes in. And it's kind of hard to believe. But this is what Sapolsky says happens…

ROBERT SAPOLSKY: Toxo starts off in the stomach of the rodent takes about six weeks to migrate its way up to the brain.

ELLEN: And once it's in there, it finds this particular region 

ROBERT SAPOLSKY: Called the amygdala… 

ELLEN: Which is like command central for fear 

ROBERT SAPOLSKY: and anxiety…

ELLEN: and terror…

ROBERT SAPOLSKY: All of that….

ELLEN: It also finds this other region kind of right next door, where a very different emotion lives.

ROBERT SAPOLSKY: Sexual arousal.

ELLEN: And what Taxo seems to be able to do is somehow cross the wires.

ROBERT SAPOLSKY: This may be some horrifically simplified soundbite, but what I think is going on is that Taxo knows how to make cat urine smell sexy… 

JAD: What? 


JAD: That is so evil.

ROBERT SAPOLSKY: Which like totally bizarre, but Toxo makes rodents like the smell of cats, and thus they approach [rat squeaking] and thus they're [cat hissing and growling] more likely to wind up in the cat's stomach. 

JAD: That's rough.

ELLEN: Yeah. In all other ways the rodent is totally normal.

ROBERT SAPOLSKY: Normal olfaction. Normal social behavior. 

ELLEN: Just hot for cats.

[cat purrs]

ELLEN: Hi good kitty. 

ELLEN: And I start to wonder…

ELLEN: Moose really likes the microphone. 

ELLEN: I love cats. Is it possible that Taxo…

ELLEN: Moose is wonderful.

ELLEN: Is what's been drawing me to cats. 

ELLEN: It’s why we let her put her fur everywhere.

ELLEN: I ask him.

ROBERT SAPOLSKY: Pure speculation, but people who think about this stuff, view it as not just purely speculative. The notion that Taxo can produce some sort of attraction to cats in humans. They don't think that's all that crazy.

JAD: Wait so you're saying that like the crazy cat lady could be Toxoplasma?

ELLEN: Well, no one's really studied that yet. 

ELLEN: Testing, testing. 

ELLEN: But there are scientists out there that are making the case that Taxo can really change you. 

ROBERT SAPOLSKY: Probably the most interesting established link is between Toxo and schizophrenia.

ELLEN: Are you Dr. Torre?


ELLEN: Nice to meet you. How are you? 

FULLER TORRE: There's actually been at last count 54 studies on Toxoplasma in people with schizophrenia and other psychoses.

ELLEN: That's Dr. Fuller Torre. He works at the Stanley Medical Research Institute that sponsors a lot of these studies. 

FULLER TORRE: Well, I've been doing research on schizophrenia since the early ‘70s. 

JAD: And he thinks there's a link?


FULLER TORRE: Not a huge effect. Very, very small risk of schizophrenia, simply because schizophrenia is very rare. 

JAD: But why would it cause schizophrenia to begin with? Is it trying to cause schizophrenia.

ELLEN: You imagine if the talks I 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. 

JAD: I see.  

ELLEN: And one of the reasons he thinks this might be true, this connection between Toxoplasma and schizophrenia, is because of a historical link. 

FULLER TORRE: 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. 

ELLEN: Why? 

[music in: mysterious violin music]

FULLER TORRE: 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. [Cat meows] The artists. [Cat meows] And it was really considered kind of weird, but it's the kind of thing that if you were an artist, or writer or something like that you started to do [Cat meows] and then to kind of spread to London, [Cat meows] where the writers and artists kept it there. And then starting in about the 1840s, it started to become a little bit more popular. [Cat meows] And then in the 1860s, and 70s, there was what called a cat craze, cats were all over greeting cards. [Cat meows] The first cat show was in London in 1870, and in Madison Square Garden, I think 1880. It became very fashionable to have a cat.

[music out]

ELLEN: We should say—I mean, he'll agree—at this point, it’s just a theory.

JAD: Okay, but is there any evidence that Taxo can actually control our behavior? Like it does with rats?

ELLEN: Well, there are some scientists out there who believe that Taxo may affect something more common to all of us.

ROBERT SAPOLSKY: Here's another one of those Give me a break…

ELLEN: That's Robert Sapolsky again. 

ROBERT SAPOLSKY: Science fiction branches to 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. 

JAD: Really? 

ELLEN: Yeah. And I asked him why. 

ROBERT SAPOLSKY: 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.

ELLEN: 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 1000s of tiny little parasites inside us, pulling our strings from the inside, well that thought is pretty creepy.

ROBERT SAPOLSKY: Even if the entire lesson with Toxo is a small subset of infected people now have one half of 1% more likelihood of one a drive really recklessly. Even lurking in that one half of 1% 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.

JAD: Either way, whatever happened with your test?

ELLEN: Well, this is me with my midwife Berry. So she's giving me the news. 

ELLEN: What did you find out from the Toxo test?

MIDWIFE: That you have had past infection with Toxoplasma. Positive. 

JAD: You're positive?

ELLEN: Yeah. But my midwife says that the baby's going to be okay. 

ELLEN: Does the baby look like she's small.

MIDWIFE: You know, 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 

ELLEN: And I believe her.

JAD: Thanks, Ellen. 


JAD: You want to hear more about anything you're in this hour, check our website

[phone beep]

ELLEN: [over the phone] Hi, there. This is Ellen Horne. I am calling with my cat Moose, who is just recovering from surgery and doing very well. And we're calling to say that Radiolab is produced by Lulu Miller and Jad Abumrad. Our staff includes Soren Wheeler, Michael Raphael…

[phone beep]

UNKNOWN: Ellen Horne, Ann Heppermann, Jonathan Mitchell and Amanda Aronczyk. With help from…

[phone beep]

UNKNOWN: Jessica Benko, Charles Choi and Emma Jacobs. Special thanks to Elizabeth Givens, Pat Walters, Karen Havlick, Lauren Sessions… 

[phone beep]

UNKNOWN: and Charles Michelet.


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