Hello, friends, We're talking about parasites again today. These parasites can have some pretty nasty impacts on human bodies, and I just wanted to give you all a heads up in case you or your kiddos are a bit squeamish about such things. I study parasites for a living, so I am a long past having a reasonable handle on what a decent person would consider disgusting. Sorry about that, Okay,
on with the show. In eighteen ninety eight, a German parasitologist named Arthur Loss was trying to figure out exactly how this particular kind of parasite infects people, as was fairly common at the time. The method he was using to try to figure out this parasite's complicated life cycle was by trying to infect himself in various ways. During this self experimentation, he discovered something surprising. He was already infected by a different parasite species. How did you make
this discovery? Well, it's kind of a gross story. You see. He knew that the parasite he was initially studying lives in our guts and produces eggs that get out of the body by traveling out in our bowel movements. So when he was checking his turns for parasite eggs, he
found the eggs from this other species. The kind of parasite he discovered he was infected with is commonly called a hookworm, and this was another species of parasite for which back in eighteen ninety eight we had figured out how it manages to infect people in the first place. So Low starts thinking back on behaviors he had engaged in recently to get a good guess for how he
got infected with this parasite. His best guess was that maybe it accidentally happened during an experiment that he was doing on hookworms and guinea pigs where he accidentally spilled some of the hookworms on his hand. He remembered afterwards that he started scratching like crazy and that it was uncomfortable, and he thought, well, maybe the parasites get through your skin.
No stranger to self experimentation. Los subsequently dropped some more juvenile hookworms on his hand and his skin started to burn and get red. Then he tried to like scrape his skin a little bit to see if he could get the worms off there, and he noticed that there were far fewer worms on that scrape than he had initially put on his hand, so he suspected, Okay, they're actually disappearing into my skin. So he's feeling pretty good about his hypothesis now that the parasites get in by
burrowing through your skin. But how could he know for sure? Well, Los finds himself a volunteer, a young man who was in need of a leg amputation, graciously agreed to help out with science. In the process, Los put some of the juvenile hookworms on the leg of the patient prior to the procedure. Following the imputation, Los was able to recover the parasites that had indeed burrowed through the skin
and were working their way through the leg. So now he knew that hookworms infect people by getting their eggs into the environment with our poop, and then the juvenile worms hatch out and go off in search of things like bare feet. Knowing how a parasite affects you gives you some tools to help combat the parasites. Flash forward about ten years and John D. Rockefeller is using his oil money to create a commission to do battle with
this parasite in the American South. Today, we're making some progress, but we still have a long way to go. Improved sanitation systems have made this parasite rare in the United States, but globally this parasite and a few other species that will also talk about in this episode. Improve sanitation systems have made this parasite rare in the United States, but hookworms and some other parasites that you find in the soil are still a problem in other parts of the world.
This parasite infects about one and a half billion people worldwide, or about twenty five percent of the global population, though the infections are mainly happening in Asia and Africa. Today, we'll talk more about these parasites and how public health officials are currently trying to do battle with this ancient scourge of humanity. To Daniel and Kelly's extraordinarily warmy universe.
Hi, I'm Daniel. I'm a particle physicist, and I contain multitudes.
Hi. I'm Kelly Wiener Smith. I study parasites for a living, and I agree Daniel does contain multitudes. I do too. We all do. You're never alone.
There's a side of me that's fascinated by biology, and then the side that thinks it's totally griss.
You know, I let both of those sides coexist inside myself. It's okay to be grossed out by something but still think it's fascinating.
You're a quantum superposition of biological fascination.
I don't think they have to be diametrically opposed, like the cat's alive the cat is dead. I think it can be both awesome and disgusting. They're not mutually exclusive states.
You never have that moment where you're like looking at something, You're like, Wow, this is fascinating, and then all of a sudden you get the ick, like, WHOA, I can't touch this thing anymore. I have to put it down.
No, but there was a moment in a talk. It was an anthropology talk that grossed me out. There was a table of monkey brains. It was that a food market, and even though I had just spent like literally the last couple months looking at fish brains and thought that I was like totally immune to brain related disgustingness, the room started to spin and I had to put my head down because looking at the monkey brains was making me sick, and I was so embarrassed. I was like,
I should be okay, but what about you. What was the moment where disgust just sort of overwhelmed you. I imagine that being married to Katrina, there's gotta be a lot of like hope related moments.
Well, you know, there are times when I expected to be grossed out, Like, for example, when my daughter was born by sea section, and they told me you have to sit behind the curtain, you can't watch, and I was like, oh no, I'm looking at this. And I stood up and I peeked over the curtain and I was totally fine, like, ow, that's my wife and they're cutting her open, and that's my daughter, and it's pretty goofy. But it was just so amazing. Yeah, I didn't fainter,
cost trouble or anything. Missed that moment, and then you know, much more simply, there's the time when I like, open the freezer in our house, I'm like, what's in this paper bag? Uh? Oh no, that's not what I expected.
It's a sample that's pretty gross. You know. It's funny I didn't get a C section, but my husband couldn't even look on the other side of the curtain over the legs because he was just like, no, no, this is all too gross. And they went to lift the umbilical cord up, like do you want to cut the And before they even got it up over the blanket, he was like, no, no, just hand me the dry clean baby, please. I don't need to know any of
this stuff. And he did a good job providing support from the safe side of the blanket.
Well. Biology is messy and squishy, but that's how life works, right, reproduction, propagation, all of that stuff. And something that I've had to come to terms with, especially being married to Katrina and learning more about microbes, is that inside all of us, it is a whole ecosystem. It's not just human cells that make you work. You are filled with all sorts of bacteria and other stuff, some of which are vital to the operation of your guts and some of which
are doing you harm. And the line between them can be a little bit fuzzy, isn't that right?
Yeah, it really can. So the parasites that we're going to be talking about today, there's some evidence that when you have just a few of them, they help suppress inflammation, or the presence of these parasites suppresses inflammation, and maybe even having some of these parasites reduces your risk of allergies or some autoimmune diseases. So yeah, that's not necessarily yes or no dichotomy sort of here. It sometimes it's a gradient. It's complicated.
Yeah, it's not something we can understand from first principles because the body is a huge complex Rube Goldberg machine, right, and you can't look at it and say, if I pulled this one thing out, everything would be better or worse, Like it would be different, and it's not always clear whether it's better or worse. So is it even clear what a parasite? I mean, if we're going to talk about parasites in humans that date back thousands of years, you know, maybe they're just part of how we evolved.
Yeah, so parasites definitely are part of how our species evolved, that they've been with us, you know, from the beginning. But then the question is do they do more harm than good? And I think the answer really depends on context and even can depend on the person how their immune system responds to these parasites. And so I think it's never a yes or no. Although with the parasites we're gonna talk about today, when you have a lot
of them, that is always bad. There is zero debate about whether or not it's bad to have a lot of these parasites. It is, and unlike tricinella, which we talked about last week, where there's been a lot of progress made around the world, but particularly in places like the United States, for controlling the transmission of this parasite and making sure pretty much no one gets it. These soil transmitted nematodes. And I think Daniel's gonna tell me
that's too much jargon. So we're gonna call them dirt worms.
Oh I love it, dirt worms, thank you.
Yes, these nematodes, which are these like long, thin, cylindrical parasites, we're gonna call them dirt worms because they're a wormy shape. These are still a problem in some parts of the United States, in particular areas that are poor and don't have good sanitation, and they are a problem in Africa and Asia. It's thought that about twenty five percent of the world's population is infected with at least one of these worms, and a lot of people are infected with a lot more than that.
I guess some of the questions we'll be asking today is how long we've been doing battle or evolutionarily dancing with these dirt worms, whether they hurt or help us, and what we can do about them in the future.
Right, Yeah, So let's just jump right in. So you know, you asked, like, how long have we been doing battle with these parasites and the answer is a really long time. So there's some evidence from the ancient Nile Valley. So like when the ancient Egyptians were, you know, ruling the world or whatever, they were infected by some of these worms. And the way that we figure it out is again
creepy but wonderful, like both those things together. So we study what are called coprolites, which is essentially like poop fossils.
Poop fossils, oop fossils.
Yes, I have such a big grin on my face, and so they are like parasite eggs that you can still like dig out of these poop fossils. In some cases you can extract a little bit of DNA from them to confirm. But the eggs from the different kinds of dirt worms that we're gonna be talking about today are pretty distinctive.
Let's go back to what these things are. Are these things we find like in the guts of mummies or in ancient toilets, or where are we finding these poof fossils? How do we know that they're poof fossils and not just lumps of dirt?
Well, all of the above. So sometimes we'll find like a latrine, and so like it's kind of clear from what's happening around the samples the specimens that it was like a latrine, and so there'll be a bunch of poop in one place. Sometimes you'll find a mummy, and if you dig around in the mummies intestines, some of the parasite eggs that we're passing through the body of
that mummy are still there. You can look there, or if you've got like a body that's sort of decomposed, you can dig around in the dirt around where they're like belly and their bells were, and sometimes you can still find parasite eggs that have been preserved in that area.
Preserved how like if you put them in water, they would like swiggle back into worms like tartar grades, or they're like fossils of these eggs. Because fossilization is some process we are replacing it with minerals, right, So what it actually is preserved here.
Yeah, it's mineralization, so they're definitely not coming back to life. Mineralized parasites sometimes with a little bit of DNA still present, but like you really have to worry about contamination. It's hard to do the DNA stuff, but we can be pretty sure.
You know, some of these ancient kings really wanted to be remembered in the future, and I wonder how they would feel about, you know, this is what they've passed down to later generations.
If you managed to get in one of those pyramids and you really didn't want anyone to disturb you, you're probably not super happy if this is happening. But yeah, that's the uncomfortable history of science.
Speaking of the history of science, we know a lot about ancient Egyptian culture, and we have their hieroglyphics. Is there any evidence in their writing that they understood what was going on in their guts? Like, were there ancient Egyptian parasitologists.
I don't think there were ancient Egyptian parasitologists. There are some writings, I think in Chinese texts where it's interpreted that they were talking about some of these worms, but we don't know for sure, so you know, the description would just be like there was a wormy thing, and you're like, well, that could be a lot of things, because we're infected by a lot of wormy things, especially
a long time ago. There's some guesses that like ancient Chinese texts were talking about roundworms, so these very long, like pencil sized worms. But I'm not an expert in this topic, and I'm under the impression that the best we can do is, oh, that's probably right ascharis for example, But we don't know for sure.
So then how far back do these fossils go, Like how long have we been living with these worms?
The review paper that I was reading talked about copper lightes so fossilized poop that had evidence of parasites from Krueger Cave in South Africa that was twelve thousand years before present, so twelve thousand years ago.
Wow.
And that mummy Utzi, how do you say, do you know the name of that mummy? The one that was found in the Alps near Italy and Australia, and I think it had like a arrowhead.
Let's see the iceman.
Yeah, yeah, the iceman. The iceman had whipworm and is intestine. Oh wow, this has been a problem for a lot of people for a long time.
Do you think it's possible that we had worms before we were humans, Like, had they evolved with us from our ancestors or was there a time when we were first infected and before that our ancestors were a worm free somehow? What do you think is more likely?
Yeah, I think our ancestors had these worms, and the worms probably speciated with us. I can't say that I've actually looked up the phylogeny of the nematodes and the ascarids and the parasites we're talking about today, but folks have done this kind of work, and there are a lot of parasites that our ancestors had, and the parasites speciated along with our ancestors and us, and so you ended up with like two sort of human e species and two you know, parasites to infect both of them.
Wow. I think that goes a long way to making the argument that it's part of being human is to have worms, because we've always had them, right, Like, literally the first humans had worms. So it's maybe what it means to be human is to be a little bit wormy.
I think what it is to be alive is to be a little bit wormy or to be a little bit infected. I think you know just about any wild animal that you go pick up in nature, if you dissect it, it's got probably a nematod, maybe a treematod. It's probably got some lice. Parasites are ubiquitous.
So what fraction of our listeners hearing this right now do you think have worms inside them?
Really depends on where they're listening from. I think you and I probably don't have worms. I might have toxoplasmosis because I have barncats and I regularly interact with their feces while I'm cleaning stuff up. But I think you know, if you cook your food well and you live in a pretty sanitary environment, you can escape a lot of this stuff.
All right, So we've been living with worms forever. It's part of being human, part of being alive, part of existing in this wonderful, squishy world. Tell us about how these things live, like, did they just hang out in your guts? Is there some whole process where they go in and out of you? Do they move from person to person? What's the whole life cycle of these crazy worms.
Yeah, so for this set of worms and for a bunch of other parasites also, they live in our guts and they produce eggs that pass with our feces into
the environment, so they're not multiplying inside of us. Each parasite that we have in us we accidentally independently, like consumed from the environment, and then their eggs go with our feces out into the environment, where if we don't take good care of our feces and we don't have good sanitary procedures, then they can go off and infect other people.
Oh so, if you have worms, you can get rid of them by just stop eating worms.
Well, I mean the worms that you have in you can survive for a while.
Oh I see.
I think the three that we're talking about today have an average lifespan of about a year, but some of them can live much longer than that. So if you stop accidentally ingesting parasites and you can go a year without reinfecting yourself, then you can get rid of these parasites.
But a problem is that there's lots of places in the world where sanitation is not very good, and so you know, humans will defecate out into the environment, and then the feces will sort of dry, and the parasites, you know, by getting on people's feet who are walking around in the like latrine area, they'll spread out into
the environment. The way the dirt worms work, and there's something like four different species of these dirt worms, is that the eggs get in the environment, and then the eggs after like waiting a short period of time, if they get into you because you like maybe you were gardening in an area where there was night soil, so like, those feces may have actually been placed on top of your plants as a way to fertilize them, and so if you don't wash them well enough or wash your hands,
you could accidentally ingest the eggs and get infected that way.
Did you just use night soil as a euphemism for poop?
Uh? No, that's a great question. No. Night soil is the like technical term for the use of human and livestock waste as fertilizer. This is actually pretty common in China, which is one of the reasons why China has problems with some of these parasites. Oh, you can treat the night soil and kill the parasites in it before you use it, but that doesn't always happen, and so that spreads the parasite like crazy.
And how big are these eggs? Like they must be very small, otherwise you would notice them and avoid eating them. Right, we're not talking chicken eggs here obviously, Like we're talking microscopic.
Yeah, microscopic. You can't see them with the naked eye. You got to put them under a microscope to see them.
Oh wow. So they're like under your fingernails and stuff.
Yeap, like pinworms. So the dirt worms are round worms, which are you know, round, and they get pretty big, like I dissected one in class, Like they're big enough that you can dissect them. They're like pencils, like they can be about a foot long, and they're thick. And after you see them, you are like, I'm not eating spaghetti for a really long time, Like I.
Just put see you got the ick?
I did get the ick? Yeah? No, asparants give me the egg. Roundworms are super inchy. And then there's whipworms and they're called that because like they have tails that kind of look like whips, but they're much much smaller. You know, a big one is like fifty millimeters and then there's hookworms. And so hookworms they get into you
in a totally different way. So they get to pop it into the environment, and then their eggs hatch and they release these tiny little juvenile stages, and the juvenile stages they go up on the grass and stuff, and as you walk past, they get on your skin and then they burrow into you. Yeah, and it often itches and is uncomfortable.
Get big timech over here, I know.
I'm sorry, I'm sorry. But they take the wildest journey to get to your gut. And I'm gonna tell you all about it when we get back from the break. So hookworm goes on this crazy journey once it gets into your body. All right, So it burrows in like you know, you're walking around, it's a beautiful morning, there's dew on the grass. But accidentally you encounter a hookworm and it burrows in, you know, between your toes or something, and it ends up in your circulatory system.
Can it dig in anywhere? Does it have to find some soft spot between your toes?
It can dig in anywhere? Oh wow, yeah nasty. And so it goes into your circulatory system and it rides it till it gets to your lungs, and then it goes out of the circulatory system into your lungs into your lungs. Well, it gets worse, I think it gets worse. And so then it crawls up your lungs and it crawls up and it gets into like sput them. And so when you like kind of cough, you cough up the parasites. And then when you swallow that again it goes into your stomach.
You cough up the worms into your mouth, so now you like have warmy mouth.
I know this is really rise.
We are tilting far from curiosity towards icky again.
I feel like those things are connected. But I've got a friend named Jimmy Burnout who got purposefully infected for a vaccine trial, and you know, like I wanted to, you know, like when you spit up, can you feel the worms in your mouth? And he's like, no, no, like they're really small. I think it was on his mind every time. He was like, eh, you know, he probably thought to himself like, oh, those are worms, but he said it wasn't like obvious. So anyway you swallow them,
they get into your gut. But hookworms cause trouble because they eat your blood. So they have these like hooky mouths, and they use those hooks to like cut into the sides of your intestine and they suck blood out that way, and then they'll move on to a different site. And so often you will end up with like a lot of blood in stool, blood in poop if you have too many of these, because they've just opened up a bunch of wounds in order to get at your blood.
So why did they go into your intestine to eat your blood If they started out in your circulatory system, why aren't they just like happy floating in blood.
So I think that it has to do with the ease of getting your eggs back out into the environment. You make eggs and you just release them into the intestine, your body will just you know, with the rest of your food and with the rest of your bowel movement, just move it back out into the environment, and that way their eggs can get back out inside of the world. The real question to me is there's this other parasite called roundworm's ask Chris. These are the ones that are
like pencil shaped. You eat them accidentally.
With a nice tomato sauce.
Maybe who knows, if you didn't wash your hands before preparing the tomato sauce. Maybe, but then they go like into your digestive tract. But then they burrow out of your stomach and into your bloodstream and do the same lung spit up, get back to your gut thing. And so I wrote an expert who works on hookworm vaccines and who studies this stuff, and his name's John Hawden, and I was like, John, why does Askris go on that long journey when it had already gotten to where
it wanted to be? And he pretty much was like, we don't know. One of the hypotheses is that it evolved from an ancestor that already made that journey and so just sort of like evolution left that step in. Whether that makes sense or not, there's another argument that they need some extra time to develop, and going through this journey gives them a little bit more development time. It's not clear to me why they can't just stay in
the gut and finish their development there. But maybe, like you know, you get intestinal cells slough off, you got some risk of being pooped out accidentally, And so the answer is, we don't really know, but it could be like a relic of what some ancestor used to do that kind of stuck with this parasite.
Maybe it's the friends they make along the way, you know.
That's right, that's right. They wanted to hang out with the other lungworms for a while, and you'd hate to lose your buddies.
How long have we known this kind of stuff? Like we know that people have been having worms forever, When did we first start to understand this stuff? When is the science of worminess really kick off?
Well, so for hookworms, which I know the most about, around eighteen forty there was a doctor Debinni who was doing dissection of a cadaver like a post mortem examination, and he found hookworms and wrote about it. So he was one of the first ones to be like, oh, like this might be something we should look into more. And then in eighteen fifty four, Wilheim Greysinger, sorry about the mispronunciations everyday, did a post mortem on a soldier
and this guy had a lot of worms. And this was the first time that somebody was like, you know what, this worm could be bad enough that maybe this is part of why the soldier died. Because the soldier had like really awful diarrhea. So that was the first instance that we know of where somebody was like, not only are these worms in there, but they could be the cause of a problem.
And do you think the earlier discovery of worms in the body was a surprise or is this something people were sort of genuinely aware of, like, yeah, people have worms in them, or it was like, oh my god, there are worms in people's bodies.
I think we knew about it before then. I think the ancient Greeks knew about some of these worms. I don't actually know how well substantiated this is, And at some point I'd love to have a whole episode on guinea worms. But you know how doctors have that staff with like the two snakes that sort of wrap around it,
and that's like this ancient symbol. There's some evidence that that was the guinea worm parasite, because the way you eradicate that parasite is you wrap it around a stick and you sort of slowly extract it from people because it sticks its head out of your ankle. Oh that nasty, But actually that's another success story. We're like close to eradicating that one. That one's pretty interesting. They're all pretty interesting.
Really, and we want to eradicate them because some of them obviously cause harm or you have too many of them. I mean, somebody like a train it might say like, hey, why are we calling these things pathogens? They're just part of the human life cycle.
Hmm. The personal line in the sand that I use is if it happened to my daughter, how would I feel about it? Or mysef if it happened to my children. If you told me, hey, your kids each have a hookworm in their gut, I'd be like, all right, that's fine.
Oh.
I wouldn't be like you need to put in anti helmethics. Anti helmethics being the drugs that you use to kill these parasites. But if somebody was like, your kids have two hundred hookworms in their guts, I'd be like, all right, right now, we got to do something about it.
Well, where's the line there? Between one and two hundred fifty hookworms? Is okay? Five is okay?
So first of all, the way that you figure out how many they have, you can't like call up and be like, hey, gut, how many hookworms are in there? And what you usually do is you look to see how many eggs are in one gram of feces and that's how you do the county at the roundworms literally make two hundred thousand eggs a day. Just incredible numbers of eggs a day. Both hookworm and whipworm can make up to like ten thousand eggs a day. So I
would trust a doctor. If a doctor said, like, your kids are almost certainly not going to get infected by any more of these because you've confirmed that, like you know, the latrine that was broken in your community has been fixed and they have very light infections, I'd be like, well, maybe that's fine. But if they were like there's blood in your kid's stool. You've got so many hookworms that they're like losing blood, then yeah, we should do something about it.
And you think there are cultural differences around the world, like in some countries they're like, no big deal hookworms. In other countries they're like, you must kill every worm inside the body. Or do you think medical practices are pretty constant around the world.
I don't know, But what I can say is that the World Health Organization, their goal isn't to get rid of the parasite entirely. They're focused particularly on trying to make sure that people with heavy infections they get treated. I mean, they would love for the parasite to be eradicated entirely. And we're going to get to this, but part of the difficulty there is that you have to completely upgrade the sanitation system to get rid of these
parasites more or less entirely. But having low intensity infections, so just a couple of worms is not a problem. And again maybe there's some evidence that it reduces inflammation. But if you have a lot of askris, they're like pretty big parasites, and so sometimes they end up in like the same part of your gut and they literally cause it compaction and nothing else can get through, and so in that case you have to get a surgery to get them removed.
Wow.
Sometimes the photos of these things end up in your parasitology textbooks and I'm like, that's the ick that I didn't need to see. But it's important. Hookworm causes a lot.
Of blood loss because they're drinking your blood.
Because they're drinking your blood, and then they also leave gaping wounds when they move to another spot and you keep bleeding.
That's not very considerate. You know, there are a lot of animals that sip our blood. But mosquitos at the very least don't leave you like dripping blood.
Mm hmm. They're totally jerks. I agree whipworm. If you have really high infections, they get kind of pushed to areas that they'd rather not be, which is like farther down in the bowel, and they cause troubles with some kids who end up just constantly feeling like they need to have a bowel movement because they've got all these parasites in there. And sometimes that causes prolapsed anus, which is really I just can't imagine if one of that happened to one of my kids. It would be so upsetting.
So then you need a surgery again to kind of like put everything back in. But another problem that's less gross to talk about is if you have a lot of these parasites, there's concerns that they cause declines in physical growth and cognitive development. And partly that's because you're just you don't have the energy. The parasites are sucking your blood. Some of them like maybe take particular vitamins out.
So a big reason that we want to treat for these parasites is because having heavy infections when you're young can have implications for the rest of your life. And kids tend to get these infections more than adults, which is surprising. It's amazing to me that we ever teach kids to wash their hands regularly, because it's so hard to get kids to wash their hands. But that's why a lot of kids get infected.
Well, I just heard from Katrina Real Time Consulting that there are some things that infect us in the US, and in the US, if they find it in you, they will prescribe medicines to try to remove it, whereas in other countries, like in Ecuador, they're like, yeah, no big deal. So, for example, blastocystis some you carry it which infects the body, and in some countries they're like, yeah, no big deal. But in the US we're like, yeah, I gotta get rid of it. And it's not clear
whether it like does more harm than good. It's like on this fuzzy edge.
Oh interesting, did you just answer an email. I'm so glad we have Katrina as a consultant for the show. So we know that these parasites at high intensities are bad, and so you don't want your kids infected with them, and so should we talk a little bit about the history of trying to do battle with these worms. Yeah, as you remember from the intro, around nineteen hundred is when that German parasitologist was self infecting himself and the patient at the hospital and figuring out the life cycle
for hookworm. About ten years after that, John D. Rockefeller, this you know, super rich guy with all of the oil money. He decides that he wants his foundation to try to eradicate hookworm from the American South. So this was a big problem in the American South because it's warm, it's moist, these are great conditions for the eggs to last for a really long time in the environment. So
he creates the Rocket Feller Sanitary Commission. And even though they said they were going to eradicate hookworm, their goal right from the beginning was to just control it and make it a little bit less bad. But part of how they advertised why this was important was they were essentially blaming hookworm for this myth of Southern laziness. So the parasite like makes you lethargic, it makes you sort of not want to move, not want to eat, like
you just feel miserable. If you've got a bunch of worms in your gut, and so they referred to hookworm as the germ of laziness. And so through this system of like education and treat and they tried to get a handle on it. So they made a bunch of videos about the hookworm life cycle, and I spent way
too many hours watching these videos the other day. And then they had some treatments at the time, but the treatments were like also a little bit toxic, and so there were some people who died when they took the treatment,
which is clearly less than ideal. Yeah, but the plan at the time was to get people to go to like doctors get their stool checked to see if they had eggs, and if so, you'd get a treatment followed with drinking a bunch of like epsom salts and water, which would sort of clear out your bowels, let's say, and the parasites would sort of pass out and you'd see them pretty gross. But the problem is that without actually upgrading the sanitation system, people just kept getting infected again.
And so there were some studies that tried to find an effect of this sanitary commission, and the results are kind of mixed. When some people analyzed the data, they'd say, like, you know, people were getting more time in school because like sometimes you feel so I mean, you don't go to school, And so they were like, you know, saying
the prevalence was lower. But then there's other studies that looked at improvements in the South over time and found things like how many days you went to school each year had been improving over time already, and so maybe it had nothing to do with huckworm eradication. It could have just been that the South was getting better at sanitation over time and this commission did nothing beneficial.
And do you know the scientific context, like this is a whim of a zillionaire essentially deciding we're going to do this medical program. Is that what the medical establishment or the scientific community would have wanted anyway, Like if they've just given them the money, is it sort of like best practices or was it just sort of like off in the weeds.
Yes, we are essentially having some of the same debates today. So it was like a reasonable first effort, and that the debates are, you know, is it worth trading without
improving sanitation? Like what kind of improvements can you make if you're not actually solving the root problem, which is that you need to tackle these sanitation problems and so so there are a bunch of organizations that were sort of inspired by these early Rockefeller efforts, and a parasitologist named u Styles was one of the first ones who was like really beating the drum for we need to tackle hookworm in the South, and he ended up working
with them on a bunch of this stuff. Yes, I think that there were probably engaging in practices that were fairly scientifically sound at the time, but there is some debate about whether or not they were balancing the risks of the medication against the benefits well enough for the people who died, and they ended up extending their reach into some other countries. And there's also debates about the relative impacts of like what their medication did in terms
of killing people versus helping people. So it's not all rosy, which is perhaps exactly what you'd expect about this time in American history. Let's take a break now, So at this point we understand the life cycle of these parasites. There have been some efforts to try to eradicate these parasites, but they've been met with sort of limited success. Where are we now? What have we tried in the one hundred plus year since the Rockefeller Sanitary Commission. You'll get your answer after the break.
All right, we are back and we are battling the ick today on the podcast we are learning all about the worms in you, the worms in me, the worms that are in all of us and make us who we are. So tell us, Kelly, how far have we come in battling these worms or have we just given up and accepted that it's a wormy world?
We will not give up. The Rockefeller Sanitary Commission, you know, met with mixed success, but eventually they ended up backing out because they were like, look, we can't improve sanitation. If you can't improve sanitation, you really can't solve the
root problem. But around the nineteen fifties nineteen sixties, sanitation in the South improved on its own, and the percent of the population that's infected by this parasite went way down, and as medical care got better and various parts of the country got lifted out of poverty, things got way better.
We do still have the parasite though in some areas of like rural Alabama, where sanitation has broken down and people are getting infected by these parasites again, but in general, in most parts of the United States, just simply the act of like going through development and improving sanitation eventually saved a bunch of people from these parasites.
And do we get flare ups when there's a natural disaster, you know, floods and hurricanes and stuff that interfere with sanitation.
I think in the United States that's pretty rare. But around the world I can imagine that those kinds of problems would make this stuff much worse. But this has remained a serious problem in Asia and Africa. In Asia, night soil sort of makes it difficult, but in Africa you have, you know, sanitation issues, and so the World Health Organization has become interested in trying to reduce the prevalence of this parasite, like the percent of the population
that's infected. But you know, even more importantly, you want to reduce the incidents of people who have lots of these parasites, because those are the people who are the most likely to like, really experience some problems. In the nineteen seventies, some drugs that were developed for livestock turned out they could be used for parasites to treat these infections, and that's albendazol and me bendazol. They're way less toxic
than prior medications, and so like that's good news. But for a while, we like had those medications, but we weren't really doing anything with them. But then in the
twenty tens, the ball really got rolling. The World Health Organization started up a program and amazingly, so, like I usually love to hate pharmaceutical companies because medications are so expensive, but they've donated like literally billions of doses of these medications to help the World Health Organization do battle with these dirt worms.
Just out of the goodness of their pharmaceutical hearts.
I mean, I'm sure it was a pr move too. So one of the problems with treating people in areas where there's not a lot of money is that, you know, pharmaceutical companies can't really make a profit by giving them medications, and so surprisingly often there are pharmaceutical companies who are willing to donate in cases like this, and so here you get these huge donations. Maybe I'm being two nice. I don't know if it happens often, but in this
case it happened. So now you've got all of these doses of drugs and you've got to try to figure out what to do. And it turns out that, you know, the Rockefeller Sanitary Commission, they would test people before giving them medications, which involved like taking a sample of feces, putting it under a microscope looking for the signs of
the eggs. But that takes a long time, and time is money because you need to hire people to do that, you need to get the microscopes in, and so it was decided that actually it would be prohibitively expensive to
treat based on already having an infection. So instead, what they decided to do was bring these drugs into countries that had a pretty high percent of the population that was carrying the worm, and then they would go to schools, and because kids usually have the heaviest infections, they would
dole out the medication at the school. So there'd be a day where like the teacher would pass these pills out to the students and they would take the medication, and in that way they were trying to treat the entire population. I think there was also some efforts to give it to moms when they would come in for like maternal care checks, so if they were pregnant or lactating, because both of these are stages where you need your energy and if you don't have it, it could cause long term impacts.
And was there any resistance to this? You know, there's like classic resistance to vaccination in some portions of society, where people against this somehow, or everybody happily accepting these drugs.
It can't be the case that everyone happily accepted the drug. That's a great question. I didn't come across stories like that when I was doing the research for this episode. Doctor Henderson wrote a great book about the eradication of smallpox.
He was in charge of the World Health Organization's effort to eradicate smallpox, if I remember correctly, And there was a lot of that, a lot of like people who didn't want to get the vaccine, and so then there was a lot of engaging with community members to convince the community members that this would be better for the community overall. And so a lot of like trust that needed to be built between medical practitioners and the communities
that they were working with. And again that totally makes sense, right. The Rockefeller Sanitary Commission that we were talking about. Some kids died from the medications, and so like asking questions was reasonable. But I think in general this program is thought to have been pretty successful in terms of like getting medications into kiddos that probably needed it.
And is it analogous to vaccines where it's helpful to the whole population for an individual to take it, because then you're just reducing the number of worms that are like in the whole ecosystem the same way that like taking a vaccine reduces the prevalence of the disease, so that folks who for whom the vaccine doesn't work, you're also protecting them.
Yeah, so that was a big part of the hope was that you know, by targeting the people who have the most parasites, those would also be the people who would be producing the most eggs and putting those eggs back into the environment. So by reducing their wormburden, you
should read reduce the risk for everybody else. But a problem is that it's really expensive and difficult to do the follow up monitoring to make sure that that kind of stuff is happening, and so often these drugs will get passed out, but then the subsequent monitoring won't happen. And the studies that have been done to look for like do you get improvements in growth and you know, cognitive abilities in communities where you give out these medications.
You know, again often that's not done. Are those assays, those tests that data collection is not happening, And then in the areas where it is happening, some studies find in effect and others don't. And that's not too surprising because you know, as we've said, having a few worms is not a big deal, but having a lot of worms is. So you might expect that the people who are getting the benefit would be the small subset of the population who had a heavy worm burden that got
significantly knocked down by this medication. So if you're looking at a whole population, it might be hard to target and see those improvements.
Well, it's always fascinating and difficult to balance the individual choices with the public health recommendations, right, And the folks who work on this have such a difficult job. I really have a lot of respect for that.
Oh my gosh, yeah, no me also and their job, like it's difficult because so you go out there once and first of all these medications don't always kill all the parasites. I was reading a review paper that said that often like it knocks down ninety percent of the parasites, but some of the parasites still live, and so you need to keep going out there and giving the medication
to people over and over again. So it kills some of the worms that they have, but it doesn't at all stop them from getting infected by worms again in the future. Oh yeah, So are you going to go out there every year for the rest of eternity and give medication to these communities. That doesn't seem like a
feasible long term solution. So these programs are often also pushing like better sanitation and other ways to kind of try to break the cycle of these diseases, and there has been pretty good success, Like, for example, Kenya was really serious about giving out the medications and doing monitoring and they're thought to have had a lot of success with the program. Hand in South Korea also gave out the drugs at school, but they also screened everybody, provided
education about how you get the parasites. They started treating their night soil, so treating the human and livestock waste before it got put on plants so the parasites would be killed first. That even started like putting legislation into place to try to make some of these like improvements permanent. And they've been really successful at controlling the parasites. Okay,
so what do we do next? So there's some areas where it's mostly been controlled, but there's other areas where I think you're just not really going to be able to control the problem until we have better sanitation. And so as countries develop and their sanitation systems improve, probably a lot of these problems will go away, sort of like we saw in the American South. There's also some effort to work on vaccines for some of these parasites.
We're going to do a whole episode on why vaccine development and parasites is difficult, And I'm not going to get into it much now because frankly, I don't know the answer and I'll need to research that. But there are some vaccines that are being trialed right now, and even if those vaccines aren't completely successful, some combination of vaccines plus medication might like put a break in transmission and allow communities to sort of eradicate the parasite. We hope.
How do vaccines work for a worm? I mean, I get the general picture for like a microbe, but does your immune system learn to combat these particular worms or what?
Yeah, that's the hope. But so one of the difficulties is that humans, when you get a hookworm infection and then you clear the infection, if our immune system remembered it, you'd expect us to be, you know, kind of immune to the parasite the next time around. But our immune systems, for whatever reason, don't seem to remember it, and so we don't have a memory in our immune system for something like hookworms the same way we do for like the flu virus or the bacteria that cause a cold.
I don't totally understand why that's the case, but it probably complicates the creation of a vaccine. But if you could get your immune system to remember, maybe by regularly giving people vaccines, like very regular reminders, and you couple that with medication to killed a few parasites, you do get maybe that's a viable solution going forward. But I think in general, sanitation is just like having a public sanitation system. That's sort of like getting a handle on
all of this is the clearest way. There's some other proposals, like there's a containment system called biogas, and you put your livestock waste and your human waste into this container and it releases like methane and some other gases that can then be piped into the house for like cooking and heating, like propane. And I wrote somebody who works on this and said, does it smell like human feces, because I wouldn't want that piped into my house, and
he said, no, it doesn't stink. It's methane. And then additionally, you get this anaerobic environment inside of the thing with all of the waste anaerobic meaning meaning no oxygen, and that kills the parasites and so then you can subsequently use that human waste as night soil and it's safe.
But there's something beautiful about cooking your food with farts.
Basically, yeah, I mean, you know, if I lived in an area where I couldn't afford heat and you could heat up farts to keep warm and it didn't stay, I would do it because I like being warm anyway. So there's a number of different proposals for how to do it, you know, keeping people from encountering these parasites in the first place is a clear way to do it. But it's just hard to get sanitation systems running in a bunch of different places. So what is the big
take home here? The big take home is that once we understood how these life cycles worked, that did give us a clear path forward for tackling these infections. But it's not actually always easy to implement the strategies that you know would kill these parasites because there's just lots of stuff going on and life is complicated. So this is another parasite that is still with us and infecting about twenty five percent of our population. But hopefully one day we'll be able to get a handle on it.
We've had some success so far. Hopefully we'll be able to reduce human suffering in the near future.
Well, so, my last question for you is we've come a lot long way in understanding what's going on inside the body and discovering these critters living inside of us. Do you think there are still big discoveries left to be made in terms of like what's living inside humans or we mostly understand it because we've like sequenced our poop and sequenced our saliva, and we know sort of what critters are in there.
I've been going through old issues of the Journal of Parasitology. I'm going to answer your question eventually, I promise. And they used to have at the end of each issue a list of the new parasites of humans that had been identified, and there were a lot. There used to be a lot on those pages, but at some point they dropped that offering entirely, like new issues don't have that, and I don't know if that's because it's just not worth keeping a list anymore because you can just find
lists online so easily. We do still find parasites occasionally infecting people. Usually they're sort of rare infections, but you know, we get a lot of zonotic infections, so which means they are parasites and pathogens that jump from wild populations to human populations as we sort of encroach upon the habitats of wild animals. So it wouldn't surprise me if more parasites and pathogens will be jumping into people the
more we encroach into the habitats of wild animals. I'm sure there's more that we'll have to learn.
And when aliens come, maybe some of their parasites will take up home in our bodies. You know, I had to bring it back to aliens eventually.
We can hope. Oh wait, yeah, how do we We haven't touched on cannibalism yet today, but anyway, missed opportunities. But yes, the alien parasites. I would love to study some alien parasit.
Well, I'm just so amazed at how much we still have left to learn about the workings of our own body and the balances between these things, and how much these things are helping and hurting and our ancient history with these crazy ichy worms.
Yeah, but crazy, icky, fascinating words. Yes, they're very interesting. But yes, I would like to see no humans suffering from heavy infections ever.
Again. Well, I hope it hasn't been too much suffering for you to hear about this crazy biological mystery and you haven't had too much I while you're driving work or eating your lunch, we appreciate you coming along for the ride.
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