Parasites

Summary

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Radiolab – "Parasites" (September 7, 2009, WNYC Studios)

Episode Overview

In this enthralling episode, Radiolab dives headlong into the hidden world of parasites—those often-invisible organisms that live within and upon us, sometimes shaping our biology, our behaviors, and even the fate of civilizations. Hosts Jad Abumrad and Robert Krulwich, alongside contributor Lulu Miller, explore parasites from all angles: as villains, clever survivors, evolutionary partners, unwitting healers, and even as subtle puppet-masters influencing the minds and actions of animals and humans alike. With dynamic storytelling and signature Radiolab sound design, the episode moves skillfully from cinematic pop culture to historical public health, current immunology, and philosophical questions about free will.

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Key Discussion Points & Insights

1. Starting with Horror: The Cinematic Roots of Parasite Fear

• Opening (00:18–04:06)

  • The episode frames the universal fear of parasites with the infamous "chestburster" scene from the film Alien, using its visceral shock to prime listeners for the uncomfortable reality: real parasites aren’t far off from sci-fi monsters.

  • Quote:
    “It's not that the little creature is disgusting, which it is. It's that it was there all along.”
    – Jad Abumrad (03:24)

  • Insight: The horror is not the grossness, but the idea of something hidden inside us, a motif carried through the episode.

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2. What is a Parasite? Challenging the Notion of Degeneracy

• Defining Parasites (04:06–07:09)
  • Science writer Carl Zimmer, introduced as a lifelong “Defender of Parasites,” joins the hosts to debunk the assumption that parasites are simple degenerates or "cheaters."
  • Carl argues for their evolutionary ingenuity and blurs the lines between independence and dependence among organisms.
  • Quote:
    “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.”
    – Carl Zimmer (05:53)

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3. The Parasite Lightning Round: Nature’s Most Bizarre Manipulators

A. Parasitic Wasps – The Wasp and the Cockroach Puppet (08:03–12:37)

• The wasp Ampulex compressa locates a cockroach, stings it to paralyze, then performs precision brain surgery with a second sting, turning the cockroach into a zombie it can lead home.
• The wasp’s larva is laid onto the cockroach and slowly consumes it from the inside, keeping it alive as long as possible.
• Quote:
  “It just stands there like, ‘I’m awake.’ But it can’t run away, can’t move. It has essentially lost its will.”
  – Carl Zimmer (09:36)
• Darwin himself supposedly said God shouldn’t be blamed for having created such wasps (11:51).
• The segment invites the listener to judge whether such behavior represents "evil" or "elegance."

B. Parasitic Nematodes – The Ant with the Cherry Red Butt (12:54–14:22)

• Zimmer describes a nematode parasite that turns an ant’s abdomen bright red and alters its behavior, causing birds to eat the ant, thereby allowing the parasite to reproduce inside the bird.
• Quote:
  “That red cherry is actually parasites inside of the ant, making it look like a red cherry.”
  – Carl Zimmer (13:09) “It's amazing.”
  – Carl Zimmer (14:22)

C. Blood Flukes – Eternal Monogamy in the Veins (14:38–17:52)

• The blood fluke’s life cycle advances from snails to human veins, where male and female flukes "spoon"—mate and remain attached for decades, sometimes as long as 40 years.
• Quote:
  “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.”
  – Carl Zimmer (17:37)

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4. Parasites as World-Changers: The Hookworm and the American South (21:17–29:41)

• The Hygiene Revolution
  • Parasitologist Dixon Despommier recounts how Rockefeller's commission discovered that widespread anemia (“laziness disease”) in the rural South was caused by hookworms, contracted mostly by barefoot farmers defecating in the open.
  • Realization: Hookworms could crawl four feet from feces; solution: bury waste six feet deep—the birth of the outhouse. This sanitation revolution drastically reduced hookworm, transformed public health, and arguably contributed to the economic revitalization of the South.
  • Quote:
    “The outhouse was invented by exploring the life cycle of hookworm ... and, in fact, Rockefeller got his wish. The South did rise again.”
    – Dixon Despommier (28:04)

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5. Parasites as Saviors? Hookworms and the Hygiene Hypothesis (30:25–44:17)

Jasper Lawrence’s Story & the Theory of Beneficial Infection

• Jasper Lawrence, a lifelong allergy and asthma sufferer, discovers research suggesting hookworm infection dramatically reduces allergies and autoimmune symptoms (the “hygiene hypothesis”). Since he can’t buy hookworms, he travels to Cameroon, finds latrines, and deliberately infects himself.

• After self-infection, Jasper’s allergies and asthma vanish.

• Quote:
  “The day I realized that I no longer had allergies ... I just started screaming in the car. I was so, so happy. And I haven't had an asthma attack since ... The vast majority of the benefit that I've experienced just come from hookworm.”
  – Jasper Lawrence (35:57)

• Jasper starts selling hookworm doses via mail—though the practice is not FDA-approved and remains controversial, with serious safety and ethical concerns.

• Immunologist David Pritchard self-infects with 50 hookworms as part of a safety trial, reporting “pain in the gut” but surviving. He stresses that evidence for therapeutic benefit still requires further study.

• The hygiene hypothesis holds that lack of evolutionary “old friends” like parasites may lead to a spike in auto-immune disorders in sanitized societies.

• Quote:
  “We function like rainforests, we're ecosystems, and we've entirely eliminated a class of organism that co-evolved with us ...”
  – Jasper Lawrence (39:20)

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6. Parasites as Puppet Masters: Toxoplasma Gondii and Mind Control (46:06–55:51)

The Toxoplasma Paradox

• Producer Ellen Horn recounts her scare with potential toxoplasma infection during pregnancy, which segues into a discussion with neuroscientist Robert Sapolsky.

• Toxoplasma gondii can only reproduce in cats; it infects rodents and rewires their brains so they are attracted to (instead of afraid of) cat smells, increasing the chance they are eaten by cats.

• Quote:
  “Toxo knows how to make cat urine smell sexy—to rodents."
  – Robert Sapolsky (50:45)

• There is speculative evidence that Toxo might affect human behavior, with some studies showing a correlation with higher rates of schizophrenia and increased risk-taking (e.g., car crashes).

• Epidemiologist Dr. Fuller Torrey points out schizophrenia’s rise in the 19th century paralleled the "cat craze" in urban Europe/America, leading some to hypothesize an indirect link.

• Philosophical Note:
  “Even lurking in that 1/2 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.”
  – Robert Sapolsky (55:22)

• Ellen’s own test turns up positive for past toxoplasma infection, but her pregnancy continues healthy and happy.

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Notable Quotes & Memorable Moments (with Timestamps)

• “It's not that the little creature is disgusting, which it is. It's that it was there all along.”
  – Jad Abumrad ([03:24])
• “I think I'm a defender of all neglected and put upon species out there.”
  – Carl Zimmer ([06:11])
• “It just stands there ... it's become a zombie, basically. ... It's amazing.”
  – Carl Zimmer ([09:36] & [14:22])
• “The outhouse was invented by exploring the life cycle of hookworm ... and, in fact, Rockefeller got his wish. The South did rise again.”
  – Dixon Despommier ([28:04])
• “The day I realized that I no longer had allergies ... I just started screaming in the car. I was so, so happy.”
  – Jasper Lawrence ([35:57])
• “Toxo knows how to make cat urine smell sexy—to rodents.”
  – Robert Sapolsky ([50:45])
• “Even lurking in that 1/2 of 1% are some serious implications for thinking about free will.”
  – Robert Sapolsky ([55:22])

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Segment Timestamps

• [00:18] – Opening with Alien scene, fear of parasites
• [04:06] – Carl Zimmer and the philosophy of parasites
• [08:03] – Lightning round: parasitic wasp/roach story
• [12:54] – Lightning round: nematode/ant story
• [14:38] – Lightning round: blood fluke love story
• [21:17] – History: Hookworm, public health, outhouse
• [30:25] – Jasper Lawrence and therapeutic hookworm hypothesis
• [46:06] – Parasites and behavior: can parasites control us?
• [48:00] – Toxoplasma gondii, cats, rats, humans, mind control
• [54:08] – Toxo, schizophrenia, the “cat craze,” free will
• [55:22] – Free will and parasite influence
• [56:02] – Ellen Horn’s test, conclusion

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Tone and Storytelling Style

The hosts approach parasites with a blend of awe, disgust, humor, and scientific curiosity, using vivid analogy, dramatizations, and sound-rich scenes. Carl Zimmer’s championing of parasites as complex, remarkable creatures is set against Robert Krulwich’s skeptical humor and Jad Abumrad’s wide-eyed wonder. Personal stories, historical vignettes, and imaginative leaps invite listeners to see parasites not merely as pests, but as major evolutionary players and surprising healers—as well as sinister manipulators. The episode closes with a sly nudge toward philosophical humility: if even a microbe can alter who we are, how much of our selfhood and free will is truly ours?

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Additional Resources

• Pictures & Info: Find more about parasitic wasps, "cherry-butt" ants, blood flukes, and hookworm at radiolab.org.
• Key Books:
  • Carl Zimmer, Parasite Rex
  • Dixon Despommier, Parasitic Diseases
• Further Research: Studies on the hygiene hypothesis, Toxoplasma and mental health, and clinical trials on therapeutic helminths.

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Transcript

[Robert Krulwich]

Oh, wait, you're listening.

[Jad Abumrad]

Okay.

[Robert Krulwich]

All right. Okay. All right.

[Pat Walters]

You're listening to Radiolab Radio Lab from wny.

[Jad Abumrad]

See?

[Robert Krulwich]

Yep.

[Dixon Despommier]

And npr.

[Jad Abumrad]

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

[Robert Krulwich]

The cinematic history of parasites.

[Jad Abumrad]

Mm. Okay, so do you remember that movie? I'm not gonna tell the name of it. Starts out. In fact, I have the script right here. Setting space.

[Robert Krulwich]

Okay.

[Jad Abumrad]

Vast, empty space. Script continues. The stars shine cold and remote, like the love of God. You imagining this?

[Pat Walters]

Yes.

[Jad Abumrad]

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.

[Jasper Lawrence]

I feel dead.

[Jad Abumrad]

Here we go. They are in a ship full of astronauts who are tired and dirty.

[Unknown Narrator/Storyteller]

Anybody ever tell you, you looked at.

[Jad Abumrad]

Me and they're, you know, palling around, and you just get the feeling this is a normal day in their astronaut lives until.

[Robert Krulwich]

What?

[Jad Abumrad]

There on the computer radar, there's a disturbance. Oh, some kind of distress signal.

[Ellen Horn]

A transmission.

[Jasper Lawrence]

Out here?

[Pat Walters]

Yeah.

[Jad Abumrad]

They think, we gotta check this out, so they trace the signal, eventually get into a pod and shoo. And they find themselves at this abandoned ship. Totally abandoned. It's like a ghost ship.

[Pat Walters]

I've never seen anything like it.

[Ellen Horn]

I wonder what happened to the crew.

[Jad Abumrad]

It's empty except for these weird eggs. And the astronauts are, like, looking at the eggs and touching the egg. Okay, now fast forward. We're back into the first ship.

[Robert Krulwich]

Okay?

[Jad Abumrad]

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.

[Robert Krulwich]

Space bar.

[Jad Abumrad]

All right, describe what you're saying.

[Robert Krulwich]

You're at the table, everyone's dressed in white.

[Jasper Lawrence]

The first thing that I'm gonna do when I get back is to get some decent food.

[Robert Krulwich]

They're talking and chatting. They're all having, like, salad.

[Jad Abumrad]

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

[Robert Krulwich]

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

[Jad Abumrad]

What's he doing?

[Robert Krulwich]

Uh. Oh, now he's coughing. He's coughing. Oh, he's having trouble breathing. He's fallen back onto the table. His chest is heaving his wrist. 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.

[Unknown Narrator/Storyteller]

Oh. Oh. Oh, God.

[Robert Krulwich]

Oh, God. So there's a red thing, a red, horrible, snakey thing.

[Jad Abumrad]

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

[Unknown Narrator/Storyteller]

Why did you make me see this?

[Jad Abumrad]

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.

[Robert Krulwich]

What do you know?

[Jad Abumrad]

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

[Robert Krulwich]

Sitting there.

[Jad Abumrad]

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, 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.

[Robert Krulwich]

Today's subject on Radiolab will be flowers in meadows. Coming up after this.

[Jad Abumrad]

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.

[Robert Krulwich]

What is a parasite, precisely?

[Jad Abumrad]

A moocher. And just to sort of slide us in, get us into the mood.

[Robert Krulwich]

I'm already not in the mood.

[Jad Abumrad]

We thought we would get things started.

[Carl Zimmer]

Maybe I'll just move this.

[Jad Abumrad]

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

[Robert Krulwich]

You should introduce yourself.

[Carl Zimmer]

My name is Carl Zimmer.

[Jad Abumrad]

Carl's a science writer, and parasites have 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 to be very annoyed. And every now and then I would notice 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.

[Jad Abumrad]

And they were growing, growing inside the caterpillar.

[Carl Zimmer]

And then finally, when they were ready, they came out. And only then did their host die.

[Jad Abumrad]

And when he finally found out that that is what was happening inside those.

[Carl Zimmer]

Fuzzy white bumps, this profound situation, this.

[Jad Abumrad]

Whole universe of babies growing into adolescence.

[Carl Zimmer]

That'S when I guess I sort of got very hooked.

[Jad Abumrad]

Which is probably an understatement, because you Are sort of like capital P, parasite man. And if you look. Yeah, 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. Now, I would argue that parasites are not degenerate. They have gained the ability to live inside three, four, five, six different species.

[Robert Krulwich]

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?

[Carl Zimmer]

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

[Jad Abumrad]

Why wouldn't a parasite be what I think you mean when you say degenerate? Because it's a tiny little thing. It infects something else. It sucks, whatever.

[Robert Krulwich]

It's not independent.

[Jad Abumrad]

Right. So when you say it's not degenerate, why do you say that?

[Carl Zimmer]

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

[Robert Krulwich]

Kit Carson.

[Carl Zimmer]

If you stripped all the bacteria out of Kit Carson, Kit Carson would get very sick.

[Robert Krulwich]

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

[Carl Zimmer]

What does Daniel Boone eat?

[Robert Krulwich]

I guess Daniel Boone eats pigeon like the rest of us.

[Jad Abumrad]

What's your point, Carl Zimmerman?

[Carl Zimmer]

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

[Jad Abumrad]

Well, 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 Krulwich]

No karma. No karma. If you are a creature that lives off someone else's vitality.

[Jad Abumrad]

Cheaters would be another way of putting it.

[Carl Zimmer]

But listen, can you appreciate how.

[Jad Abumrad]

And I'm just gonna cut this short right here. Carl says, no, no, no.

[Carl Zimmer]

They're amazing.

[Jad Abumrad]

Time and time again he says, no, no, no. And the argument went on.

[Carl Zimmer]

Still waiting to hear about how you are able to photosynthesize your plants.

[Robert Krulwich]

That do it for me. But I go about it in a manful way.

[Carl Zimmer]

You can't even do it yourself.

[Jad Abumrad]

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.

[Jasper Lawrence]

Lulu.

[Robert Sapolsky]

Yeah?

[Robert Krulwich]

Come.

[Jad Abumrad]

You're gonna be the moderator. Yeah. Get that mic.

[Ellen Horn]

Test, test.

[Jad Abumrad]

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. Go ahead.

[Dixon Despommier]

Shall I do.

[Jad Abumrad]

Okay, yeah.

[Dixon Despommier]

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 Abumrad]

Big wasps, small wasps.

[Carl Zimmer]

They're generally pretty tiny, and they go.

[Dixon Despommier]

After all sorts of things.

[Carl Zimmer]

So some will lay them in Carl's.

[Dixon Despommier]

Caterpillars, spiders, or the one Carl's gonna tell us about.

[Carl Zimmer]

This particular wasp is called Ampulex compressa.

[Dixon Despommier]

Goes after a cockroach. 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.

[Dixon Despommier]

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.

[Carl Zimmer]

The cockroach and stings it right in the belly.

[Dixon Despommier]

The cockroach twitches for a second and then falls.

[Jad Abumrad]

Boom.

[Carl Zimmer]

The cockroach is paralyzed.

[Dixon Despommier]

Now, the wasp takes its time, repositions itself, puts its butt up right near.

[Carl Zimmer]

The cockroach's head, and delivers a second sting. The stinger actually sort of threads its way to a particular spot in the brain.

[Dixon Despommier]

And this does something odd.

[Carl Zimmer]

Moments later, the cockroach recovers, sort of stands up and can walk again.

[Dixon Despommier]

But something is wrong, very wrong.

[Carl Zimmer]

It just stands there like I'm awake. But it can't run away, can't move. It has essentially lost its will.

[Jad Abumrad]

What does that mean?

[Robert Krulwich]

It's a puppet?

[Carl Zimmer]

Yes, it is a puppet. It's become a zombie, basically. And so now the wasp will literally grab onto the cockroach's antenna and start pulling on it.

[Jad Abumrad]

How does it grab? With what does it grab?

[Carl Zimmer]

I believe with its mouth.

[Dixon Despommier]

Imagine a tiny wasp guiding a cockroach.

[Carl Zimmer]

Across the desert floor like a dog on a leash.

[Dixon Despommier]

And so it leads it down, down.

[Carl Zimmer]

Down, down into a little burrow it's made. And the cockroach says, okay, wherever you want to go.

[Dixon Despommier]

Then once the wasp has the roach.

[Carl Zimmer]

In the burrow, it lays its eggs on the underside of the cockroach.

[Dixon Despommier]

So now you've got this drugged roach sitting on top of some wasp eggs.

[Carl Zimmer]

And then the wasp goes out and it seals the burrow.

[Robert Krulwich]

It buries the cockroach alive.

[Carl Zimmer]

Well, it's.

[Robert Krulwich]

It just puts them in a cell.

[Carl Zimmer]

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

[Jad Abumrad]

How's it staying alive at this point?

[Carl Zimmer]

Well, parasites are very careful, you know, they won't eat vital organs that would kill it.

[Dixon Despommier]

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 Krulwich]

Bits of Wonder Bread, essence of skin.

[Carl Zimmer]

Old hair that you can just feed on, and the host stays alive.

[Robert Krulwich]

Wow.

[Jad Abumrad]

And then what happens?

[Dixon Despommier]

Eventually, the little baby wasp larva grows.

[Carl Zimmer]

Up inside the cockroach and develops into an adult.

[Dixon Despommier]

And then one day, the wasp eats.

[Carl Zimmer]

Its way up a little hole out of the cockroach's body, shakes off its wings and flies off.

[Jad Abumrad]

And then the roach dies. Then the roach dies, and only then. Yeah. 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.

[Dixon Despommier]

But if you ask Carl, he'll have you think about that moment, the moment where the wasp stings the brain.

[Carl Zimmer]

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 then turns the cockroach into its slave. I know that that wasp didn't get a PhD in neurobiology, and yet it.

[Dixon Despommier]

Has performed a kind of brain surgery.

[Carl Zimmer]

Very precisely in a very elegant way.

[Jad Abumrad]

Or evil might be the other way. Okay, go ahead.

[Carl Zimmer]

But there's a complexity there that you can't. An eye.

[Dixon Despommier]

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

[Carl Zimmer]

I mean, here's another example that I actually was looking at today.

[Jad Abumrad]

You're holding your computer up to the.

[Dixon Despommier]

Glass, and on the screen is a big black ant.

[Jad Abumrad]

It looks like it's carrying a cherry, right?

[Dixon Despommier]

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 Abumrad]

What part of the ant is that? Is that its butt?

[Carl Zimmer]

Essentially, yeah.

[Jad Abumrad]

Wait a second, is it. It looks like it's sticking its big red butt up into the air.

[Carl Zimmer]

Yeah. Their behavior has changed, so they waggle around their tail, as it were.

[Dixon Despommier]

Now, why on earth would a parasite turn an ant's butt red and then make it stick its butt up into the air?

[Carl Zimmer]

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. Bird's gonna go for that red ant.

[Jad Abumrad]

Very quickly because it thinks it's a berry.

[Carl Zimmer]

Yeah.

[Robert Krulwich]

And then what?

[Carl Zimmer]

It's going to swallow this little package full of nematode eggs.

[Robert Krulwich]

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

[Carl Zimmer]

Yes.

[Jad Abumrad]

What's the benefit of being in the air?

[Carl Zimmer]

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

[Dixon Despommier]

And how better to spread your seed far and wide than to drop from.

[Carl Zimmer]

The sky with the bird's droppings?

[Jad Abumrad]

That is brilliant.

[Carl Zimmer]

That's brilliant.

[Jad Abumrad]

I mean, look at the. It's red is up in the air.

[Robert Krulwich]

Yeah.

[Carl Zimmer]

It's amazing.

[Jad Abumrad]

It's like, how can a stupid little thing be so brilliant?

[Carl Zimmer]

Because they're not degenerates.

[Jad Abumrad]

But they're still cheating.

[Dixon Despommier]

And then, just to bring his point.

[Carl Zimmer]

Home, just to pick a common one.

[Dixon Despommier]

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.

[Pat Walters]

Water.

[Carl Zimmer]

Fresh water, in Africa, Asia, parts of South America.

[Dixon Despommier]

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 Krulwich]

So imagine a foot going into the shallow end of the palm. I see toes, I see bottom of foot, I see ankle.

[Carl Zimmer]

Well, if you're blood fluke, you don't see anything. You don't have eyes.

[Robert Krulwich]

Oh, sorry.

[Dixon Despommier]

But eventually you find a foot, secrete.

[Carl Zimmer]

A little enzyme, basically turn a little bit of skin into butter, and you slip into the vein. And now you're gonna swim. My circulatory system. You're gonna ride along in the blood. And now it's time to find a mate.

[Robert Krulwich]

A mate.

[Jad Abumrad]

So there's sex. So there's male and female is what you're saying?

[Carl Zimmer]

Sure. They're animals.

[Jad Abumrad]

They're animals. I would have never called them animals. That's interesting you say that. That's a whole nother topic, I guess. All right, so.

[Carl Zimmer]

So the female is very thin. It's 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.

[Robert Krulwich]

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.

[Carl Zimmer]

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.

[Dixon Despommier]

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, sort of fits in the trough.

[Ellen Horn]

Oh.

[Jad Abumrad]

So it's like a groove. The female goes and occupies the groove.

[Robert Krulwich]

Right.

[Carl Zimmer]

Now, this isn't just. This isn't mating. This is way beyond mating. The males will feed the female, for.

[Dixon Despommier]

Starters, and they will stay this way.

[Carl Zimmer]

For a long, long time.

[Jad Abumrad]

Really?

[Carl Zimmer]

Yeah.

[Jad Abumrad]

Like days, Years. Years.

[Carl Zimmer]

Years, yeah.

[Robert Krulwich]

Oh, my God. Years in human time. Years to them.

[Carl Zimmer]

Just years. Years, Years, Years.

[Robert Sapolsky]

Years.

[Robert Krulwich]

Like the Earth going around the sun kind of years.

[Carl Zimmer]

Yes.

[Dixon Despommier]

In fact, there have been cases where people show up at their doctors 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.

[Robert Krulwich]

What?

[Jad Abumrad]

40?

[Carl Zimmer]

Yeah.

[Jad Abumrad]

4, 0.

[Carl Zimmer]

40 years ago. Yeah. And the reason that they're getting sick is that these male and female blood flukes are still together making eggs.

[Dixon Despommier]

And Carl's literally glowing when he says this.

[Carl Zimmer]

I. 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.

[Dixon Despommier]

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

[Jad Abumrad]

I gotta hand it to him, he's good.

[Robert Krulwich]

Carl, you mean?

[Jad Abumrad]

Yeah.

[Robert Krulwich]

Yeah.

[Carl Zimmer]

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

[Jad Abumrad]

No kidding.

[Robert Krulwich]

Really? Yeah.

[Jad Abumrad]

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 expert 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, 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.

[Jad Abumrad]

How many is a lot?

[Carl Zimmer]

Tens of thousands of species of tapeworms.

[Jad Abumrad]

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 stuck them end to end, how far would it go? And it was many light years way beyond our galactic neighborhood.

[Robert Krulwich]

In other words, there are more cheats than there are honest people, honest creatures on Earth.

[Carl Zimmer]

Oh, yeah.

[Jad Abumrad]

We should. We should go to break, don't you say?

[Robert Krulwich]

I think we should.

[Jad Abumrad]

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. Also want to encourage you to go to our website where you can find pictures of the the blood fluke spooning the ant with swollen red butt, and of course, the wasp with the cockroach.

[Robert Krulwich]

Nature porn. And it's all [e-mail].

[Jad Abumrad]

I'm Jad Abumrad.

[Robert Krulwich]

I'm Robert Kurowich.

[Jad Abumrad]

Stay with us.

[Carl Zimmer]

Hi, this is Carl Zimmer.

[Pat Walters]

Radiolab is funded in part by the Alfred D. Sloan foundation, the Corporation for Public Broadcasting and the National Science Foundation.

[Ellen Horn]

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

[Carl Zimmer]

End of message.

[Jad Abumrad]

Hello, I'm Jad Abumra.

[Robert Krulwich]

And I'm Robert Krulwich.

[Jad Abumrad]

This is Radiolab. Our topic today, parasites. Parasites.

[Robert Krulwich]

Now, we've met them there and we've met them when they're not so nice.

[Jad Abumrad]

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

[Robert Krulwich]

Oh, we haven't.

[Robert Sapolsky]

I thought.

[Robert Krulwich]

I thought that. Oh, they're close flukes.

[Jad Abumrad]

They're pretty nice. Yeah, they were nice.

[Robert Krulwich]

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 invisible. Invisible and sort of off stage.

[Jad Abumrad]

Yeah.

[Robert Krulwich]

But when you back off a little bit and consider them, you know, in the effects that they have on the.

[Jad Abumrad]

World, there are actually these powerful sculptors of monumental narrative.

[Robert Krulwich]

In other words, these are little guys telling very big stories.

[Jad Abumrad]

In fact, here's an example. Recently I went to visit a guy named Dixon Despamier at 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.

[Unknown Narrator/Storyteller]

The story I love telling the most.

[Jad Abumrad]

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.

[Unknown Narrator/Storyteller]

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

[Jad Abumrad]

The story begins in 1908, John D. Rockefeller, Sr. Really Rich Guy, is sitting in his New York office and he's.

[Unknown Narrator/Storyteller]

Thinking, how can I make more money selling something to the South?

[Jad Abumrad]

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 would just.

[Unknown Narrator/Storyteller]

Get off their butts and get going.

[Jad Abumrad]

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

[Unknown Narrator/Storyteller]

The farms were not operational. The economic engine was turned off.

[Jad Abumrad]

The economy was in the toilet. And so John D. Rockefeller wanted to know why. Why aren't they producing more?

[Unknown Narrator/Storyteller]

Yep. What's happened to their economic engine? So he thought, I know, I'll form a commission.

[Jad Abumrad]

Yeah.

[Unknown Narrator/Storyteller]

So he sent out 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 Abumrad]

What does that mean?

[Unknown Narrator/Storyteller]

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

[Jad Abumrad]

Sure.

[Unknown Narrator/Storyteller]

Okay. Remember that little guy that played the banjo?

[Jad Abumrad]

I remember the other scene that we all remember. We're not gonna talk about that.

[Unknown Narrator/Storyteller]

No, we're not. No, we're not. Back in the banjo, if you can recall what that little banjo player looked like.

[Carl Zimmer]

Come on out with ya.

[Unknown Narrator/Storyteller]

Little wiry looking guy. But he looked old.

[Jad Abumrad]

Sickly pale.

[Unknown Narrator/Storyteller]

Yeah, sickly pale and yet an adult.

[Robert Krulwich]

Well, wait a second, wait a second, wait a second. That is not a description of all Southerners. No inscription of one teeny corner in a.

[Jad Abumrad]

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 looked weak, they looked wan. They looked kind of wan, Wan, wan, wan.

[Robert Krulwich]

They were wan.

[Jad Abumrad]

Pale, lethargic.

[Robert Krulwich]

It's interesting. Wan or wan?

[Jad Abumrad]

Wan.

[Unknown Narrator/Storyteller]

Huchoo.

[Jad Abumrad]

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.

[Unknown Narrator/Storyteller]

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.

[Jad Abumrad]

Next thing you know, Rockefeller puts together another commission, this one with doctors, and he sends them back down to the.

[Unknown Narrator/Storyteller]

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. No anemia. Sandy, loamy 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.

[Jad Abumrad]

And this seemed to be a clue. The incidence of anemia was linked somehow to the soil. Maybe. Bum, bum, bum. Yes. Something was in the soil.

[Unknown Narrator/Storyteller]

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

[Jad Abumrad]

The hookworm.

[Ellen Horn]

The hookworm.

[Jad Abumrad]

So they thought, all right, let's run some tests.

[Unknown Narrator/Storyteller]

And when they did big time, they discovered hookworm. Big time. So the anemia is due to hookworm.

[Jad Abumrad]

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 hookworms are in you, they're gonna come out of you when you go to the bathroom. So they asked these southerners, when you guys defecate, where do you do it? Most of them said something like this.

[Unknown Narrator/Storyteller]

And I defecate over there. You see that tree over there? That's where I defecate. So I defecate over there, but I live over here.

[Jad Abumrad]

Okay, so then the investigators ask the next question. When you go to that tree and do it, do you. Do you wear any shoes? Most of them said no, barefoot, just.

[Unknown Narrator/Storyteller]

Like everybody else, because it's comfortable.

[Jad Abumrad]

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.

[Unknown Narrator/Storyteller]

Oh, my goodness. It can crawl, right? So let's find out how far it can crawl.

[Jad Abumrad]

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

[Unknown Narrator/Storyteller]

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 begin 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 2ft on day two. My God, they're at 2ft. At day three.

[Jad Abumrad]

They'Re at 3ft.

[Unknown Narrator/Storyteller]

I can't believe they're crawling a long way. Day four, they crawled to four feet.

[Jad Abumrad]

What about day five?

[Unknown Narrator/Storyteller]

I'm allowed to ask. And what about day five?

[Jad Abumrad]

Five feet. No, no. Four feet.

[Unknown Narrator/Storyteller]

That's it.

[Jad Abumrad]

So after four feet, they're what, exhausted?

[Unknown Narrator/Storyteller]

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 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.

[Jad Abumrad]

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

[Unknown Narrator/Storyteller]

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 Abumrad]

That sounds too easy to me, though. Yeah, but you're telling me that an understanding of hookworm, which created the outhouse, removed the, quote, southern laziness disease, and they did rise.

[Unknown Narrator/Storyteller]

It did.

[Jad Abumrad]

And you bring that all back to the hookworm?

[Unknown Narrator/Storyteller]

I do.

[Ellen Horn]

Really?

[Unknown Narrator/Storyteller]

No, I bring it back to sanitation.

[Jad Abumrad]

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

[Robert Krulwich]

Air conditioning and highways and universities and stuff like that.

[Jad Abumrad]

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 shadows, there are all of these unintended consequences.

[Unknown Narrator/Storyteller]

Salmonella disappeared. Iostalytica disappeared. Shigella disappeared. Cholera disappeared. Giardia disappeared. Cryptosporidium, anything that's associated with parasites and feces disappeared. Every time we built outhouses and people used them religiously, guess what? Their kids could stay in school longer. They could learn more. They got ahead faster.

[Jad Abumrad]

Dixon Dusvamier is a professor of public health in environmental health sciences and microbiology at Columbia University.

[Robert Krulwich]

Can they make longer titles at that university?

[Jad Abumrad]

He literally wrote the book on parasites.

[Robert Krulwich]

The book is called Parasitic Diseases. You know it very well. And 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 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 hookworms. And to begin that discussion, let's go to our reporter Patrick Walters. So, Pat, are you there?

[Pat Walters]

Yeah, I'm here, Robert.

[Robert Krulwich]

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 Krulwich]

So where is 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, but.

[Pat Walters]

It was nothing debilitating.

[Jasper Lawrence]

They were just allergies.

[Pat Walters]

So, you know, he just like most other people who have allergies, just learn to deal with it, you know, you live with it.

[Jasper Lawrence]

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 anymore.

[Pat Walters]

I was thinking someone with allergies starting a landscaping business, that seems kind of unexpected.

[Jasper Lawrence]

Stupid is actually the word for it. And within six months or a year, he starts to notice 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. 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 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.

[Pat Walters]

And he decides in the summer of 2004 to take a vacation. 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 after lunch and I stayed on the Internet until perhaps two in the morning. I didn't stop.

[Pat Walters]

And he's reading and reading.

[Jasper Lawrence]

And the work of all these researchers, one study after Japan, epidemiological studies in Africa, animal models of multiple sclerosis. This enormous weight of evidence that in.

[Pat Walters]

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 Krulwich]

Hookworm?

[Pat Walters]

Yeah. Hookworms, yeah.

[Jasper Lawrence]

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.

[Jasper Lawrence]

Oh, yeah.

[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 you zoom way in, they have this big circular mouth brimming full of pointy teeth. Very scary to look at. They have these toothy mouths 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.

[Robert Krulwich]

This guy wants hookworms in his intestines?

[Pat Walters]

Absolutely. And so you just Google it.

[Jasper Lawrence]

Yeah, hookworms for sale. I mean, you know, someone's gotta be selling them. But 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.

[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 him around. So he and his driver would go.

[Jasper Lawrence]

To a village, get out of the.

[Pat Walters]

Car, walk up to these villagers and ask them if they could see the latrine.

[Jasper Lawrence]

Just an open area, 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. Must have been 110 degrees that day. 100% humidity. And the stench and the noise from the insects, it was so repulsive and so Disgust.

[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 he 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 I started driving, and I had the window down. You know, 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. 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 just come from hookworm.

[Robert Krulwich]

What is the hookworm doing? Do you know?

[Pat Walters]

Well, so the immune system that we learn about in elementary school is all about, like, these attack cells that go after foreign invaders and destroy them. 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. There are 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.

[Robert Krulwich]

So these are like lullaby cells, exactly.

[Pat Walters]

What lots and lots of scientists think. Joel Weinstock 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.

[Jad Abumrad]

Coevolution, parasites living within your body.

[Robert Krulwich]

Your immune system changes.

[Pat Walters]

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

[Robert Krulwich]

Worm gets a home.

[Pat Walters]

There's food coming down the food pipe. And in return, the human immune system gains some kind of some form 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.

[Unknown Narrator/Storyteller]

That's the gift.

[Pat Walters]

You do something for the worm, the worm does something for you.

[Robert Krulwich]

So then by that logic, what we in the west, in the richer countries have done stupidly is we have taken, cleaned ourselves up too much and we don't have enough wormies in us.

[Pat Walters]

Yeah, this is called, they call it the hygiene hypothesis.

[Robert Krulwich]

The hygiene hypothesis that we're not dirty enough.

[Pat Walters]

Too clean.

[Jasper Lawrence]

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.

[Robert Krulwich]

Now, I don't want to leave the.

[Pat Walters]

Impression that hygiene is bad for you.

[Robert Krulwich]

People can't go back to living in filth, kids playing in sewage by the riverbank. But in improving our hygiene we are.

[Carl Zimmer]

Also excluding organisms that may be important.

[Jad Abumrad]

For making us well.

[Robert Krulwich]

So then what does Jasper do about all this?

[Pat Walters]

He decides to start a business selling hookworm to people.

[Robert Krulwich]

What?

[Pat Walters]

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

[Jad Abumrad]

How sorry to break in for a second path.

[Pat Walters]

Hi Jad.

[Jad Abumrad]

Where does he get the hookworm from?

[Pat Walters]

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?

[Jasper Lawrence]

Well, it's a 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 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.

[Robert Krulwich]

Is this a safe thing to do, to suggest Jasper?

[Pat Walters]

Jasper has done tons and tons of research but he's not a doctor, the treatment is not approved by the fda.

[Robert Krulwich]

That's what 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]

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.

[Robert Krulwich]

At the University of Nottingham where I study parasites and the wound healing properties of migration. So we've now got two safety Trials under our belts. But we've yet to conduct the trials to show that therapeutic benefit. Results from infection with worms.

[Pat Walters]

So Pritchard infected himself pretty much just to make sure that it was safe.

[Robert Krulwich]

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. Determined that 10 worms were tolerated.

[Pat Walters]

But Pritchard, when he did this proof of safety study, actually gave himself 50 hookworms.

[Robert Krulwich]

Oh.

[Pat Walters]

Which put him out of commission for a while.

[Robert Krulwich]

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.

[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.

[Robert Krulwich]

So if you have too many, 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 gonna. 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's kind of just gone for it. You know, it's a very sort of.

[Jasper Lawrence]

Like, cowboy move to the scientific community. I think they believe that I am premature.

[Pat Walters]

It's not FDA approved.

[Jasper Lawrence]

In offering this to the public, you.

[Jad Abumrad]

Don'T know what it is.

[Unknown Narrator/Storyteller]

You don't know its purity.

[Robert Krulwich]

It's not safe.

[Pat Walters]

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. 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 that business?

[Jasper Lawrence]

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.

[Pat Walters]

The way he sees it, people are scared.

[Jasper Lawrence]

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?

[Robert Krulwich]

Thanks to reporter Pat Walters.

[Jad Abumrad]

Thanks, Pat.

[Robert Krulwich]

And to Jasper Lawrence.

[Jad Abumrad]

And to the worms.

[Robert Krulwich]

And to the hookworms. Thank you, hookworms.

[Jad Abumrad]

Thank you, hookworms.

[Robert Krulwich]

More information about hookworms on our website. And that's the end of this section.

[Jad Abumrad]

Oh, don't you want to see the attention? Address Radiolab.org yes, hookworm. No, just.org. Radiolab will continue in a moment.

[Carl Zimmer]

This is Mike from El Dorado Hills, California.

[Robert Krulwich]

Radiolab is supported in part by the.

[Carl Zimmer]

National Science foundation and by the Alfred P. Sloan foundation and had the advancing public understanding of science and technology in the modern world. More information about [e-mail].

[Robert Krulwich]

Saddle in the Town.

[Jad Abumrad]

Hello, I'm Jad Abumrad.

[Robert Krulwich]

I'm Robert Krulwich.

[Jad Abumrad]

This is Radiolab. Today's topic, parasites.

[Robert Krulwich]

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 us, some of us, a little lethargic or solving our allergies.

[Jad Abumrad]

Yeah. Here's a question to consider, though. Can they not just affect our behavior? Can they control our behavior?

[Robert Krulwich]

Yeah. Different question entirely. Yeah.

[Jad Abumrad]

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.

[Ellen Horn]

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.

[Jad Abumrad]

I've met Moose.

[Ellen Horn]

She's a very sweet cat.

[Jad Abumrad]

She's a darling.

[Ellen Horn]

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 had, 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 mood mice. Are you ready for me?

[Dixon Despommier]

Yeah.

[Ellen Horn]

She told me to rush right down to her office. So it bled pretty profusely. It did.

[Jad Abumrad]

Wait a second. Why? What's so scary about cat poop?

[Ellen Horn]

Well, it turns out that cat poop can have in it this tiny parasite called Toxoplasma gondii. But what is the threat to the baby? If it gets to the baby, it can cause mis. Miscarriage. It can cause stillbirth, and it can also cause seizures, blindness.

[Jad Abumrad]

So you're. You're freaking out at this point?

[Ellen Horn]

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

[Jad Abumrad]

Cranium, small head.

[Ellen Horn]

But my midwife said there's probably nothing to worry about. So she took my blood. This is probably the better arm. And she's sent me home. The turnaround time for the test is between two and three days.

[Robert Krulwich]

Okay.

[Ellen Horn]

Okay. So I'm looking on the Internet at home. I proceed to get myself even more freaked out. A bunch of things about toxoplasmosis. And one of the things that I found was this lecture by Robert Swolsky.

[Robert Sapolsky]

Now, the example I'm talking about here.

[Ellen Horn]

He'S a neuroscientist who we've had on the show a lot.

[Robert Sapolsky]

It has to do with a parasite called toxoplasm.

[Ellen Horn]

And I just decided that I was gonna call him up.

[Robert Krulwich]

Hello.

[Ellen Horn]

And ask a few questions.

[Robert Sapolsky]

Okay, so what's the deal with Toxo?

[Ellen Horn]

And he proceeded to tell me one of the most amazing feats of mind control that I'd ever heard.

[Jad Abumrad]

What'd he tell you?

[Ellen Horn]

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

[Robert Sapolsky]

Yes, it really has wandered off into the wrong count. If it winds up in a human.

[Ellen Horn]

It wants to be inside moose for.

[Robert Sapolsky]

Totally mysterious reasons, at least to me. Toxo can only reproduce sexually in the gut of cats.

[Ellen Horn]

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 poop.

[Robert Sapolsky]

So it's out there now in the cat feces.

[Ellen Horn]

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

[Robert Sapolsky]

It's a hardwired aversion And. And Toxo's evolutionary challenge now has been to figure out how to get rodents inside cats stomachs.

[Ellen Horn]

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 Horn]

And once it's in there, it finds this particular region called the amygdala, which is like command central for fear and.

[Robert Sapolsky]

Anxiety and terror, all of that.

[Ellen Horn]

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

[Robert Sapolsky]

Sexual arousal.

[Ellen Horn]

And what Toxo seems to be able to do is to somehow cross the wires.

[Robert Sapolsky]

This may be some horrifically simplified sound bite, but what I think think is going on is that Toxo knows how to make cat urine smell sexy.

[Jad Abumrad]

What?

[Robert Sapolsky]

To rodents, which.

[Jad Abumrad]

That is so evil.

[Robert Sapolsky]

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.

[Carl Zimmer]

That's rough.

[Robert Krulwich]

Yeah.

[Ellen Horn]

In all other ways, the rodent is totally normal.

[Robert Sapolsky]

Normal or faction normal Social behavior.

[Ellen Horn]

Just hot for cats.

[Jad Abumrad]

Such a good kitty.

[Ellen Horn]

I start to wonder. Moose really likes the microphone. I love cats.

[Carl Zimmer]

Yeah.

[Ellen Horn]

Is it possible that Toxo is what's been drawing me to cats? That's why we let her put her fur everywhere. I. I ask him.

[Robert Sapolsky]

Pure speculation. But people who think about this stuff view it as not just. 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.

[Jad Abumrad]

Wait, so you're saying that, like, the crazy cat lady could be toxoplasma?

[Ellen Horn]

Well, no one's really studied that yet. Testing, testing. But there are scientists out there that are making the case that Toxo can really change you.

[Robert Sapolsky]

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

[Ellen Horn]

Hey, Dr. Tory. Nice to meet you.

[Robert Krulwich]

There's actually been, last count, 54 studies.

[Jasper Lawrence]

On toxoplasm in people with schizophrenia and other psychoses.

[Ellen Horn]

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

[Robert Krulwich]

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

[Jad Abumrad]

And he thinks there's a link.

[Ellen Horn]

Yeah.

[Robert Sapolsky]

Not a huge effect, a very, very small risk of schizophrenia simply because schizophrenia is very rare.

[Jad Abumrad]

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

[Ellen Horn]

Imagine if the Toxo is 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.

[Jad Abumrad]

The fact that.

[Jasper Lawrence]

That what we now call schizophrenia was.

[Robert Krulwich]

Quite rare until the late part of the 18th century. And then during the 1800s, schizophrenia increased very rapidly.

[Ellen Horn]

Why?

[Robert Krulwich]

This was the first time when we.

[Jasper Lawrence]

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.

[Jad Abumrad]

Writer or something like that, you started to do.

[Jasper Lawrence]

And then it kind of spread to.

[Jad Abumrad]

London, where the writers and artists kept it there.

[Jasper Lawrence]

And then starting in about the 1840s.

[Robert Krulwich]

It started to become a little bit more popular.

[Jasper Lawrence]

And then in the 1860s and 70s, there was what called a cat craze.

[Robert Krulwich]

Cat were all over greeting cards. The first cat show was in London in 1870.

[Jasper Lawrence]

And in Madison Square Garden, I think, 1880, it became very fashionable to have.

[Ellen Horn]

A cat, we should say. I mean, he'll agree at this point, it's just a theory.

[Jad Abumrad]

Okay, but is there any evidence that Toxo can actually control our behavior like it does with the rats?

[Ellen Horn]

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

[Robert Sapolsky]

Here's another one of those. Gimme a break.

[Ellen Horn]

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 Abumrad]

Really?

[Ellen Horn]

Yeah. And I asked him why.

[Robert Sapolsky]

Insofar as Toxo makes rodents get really imprudent about cats 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 Horn]

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.

[Robert Sapolsky]

Even if the entire lesson with Toxo is a small subset of infected people now have 1/2 of 1% more likelihood of want to drive really recklessly. Even lurking in that 1/2 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 Abumrad]

By the way, whatever happened with your test?

[Ellen Horn]

Well, this is me with my midwife, Barry, and she's giving me the news. What did we find out from the toxo test?

[Jad Abumrad]

That you have had past infection with toxoplasma.

[Robert Krulwich]

Positive.

[Jad Abumrad]

You're positive?

[Ellen Horn]

Yeah, but my midwife says that the baby's going to be okay. Does the baby look like she's small?

[Unknown Narrator/Storyteller]

No, she looks like she's a nice.

[Ellen Horn]

Size to a little bit on the larger size.

[Jad Abumrad]

So not a baby I'd be worried about.

[Ellen Horn]

And I believe her.

[Jad Abumrad]

Thanks, helen.

[Ellen Horn]

Sure.

[Jad Abumrad]

You want to hear more about any anything you heard in this hour, Check.

[Ellen Horn]

Our website, Radiolab.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 Radiolab is produced by Lulu Miller and Jada Boomrod. Our staff includes Thorn Wheeler, Michael Rayfield.

[Jasper Lawrence]

Ellen Horn and Hepperman, Jonathan Mitchell and.

[Ellen Horn]

Amanda Oroncic, with help from Jessica Benko, Charles Choi and Emma Jacobs. Special thanks to Elizabeth Gidden, Pat Walters, Karen Havlick, Lauren Sessions and Charles Michelet.