January 28, 2025 • 46 mins
Daniel and Kelly talk about how public health officials turned "the most serious parasitic disease in New England" into a disease that only afflicts about 15 people per year in the whole of the United States.
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Speaker 1 (00:06):
In nineteen forty seven, doctor Norman Stole gave his presidential
address to the American Society of Parasitologists. His talk was
called This Wormy World, And if you study parasites, this
talk is a real classic. Stole wanted an estimate for
how many people in the world were carrying particular kinds
of wormy parasites. So we're talking things like nematodes, tapeworms,
(00:28):
and trematodes, not the kind of things that cause the flu,
so not bacteria or viruses. So the context here is
that World War II had recently ended, but the problems
for US soldiers who participated in the war had not.
Soldiers returning home from the war had brought back with
them the parasitic diseases that are found all over the world.
(00:49):
US interest in parasites skyrocketed as Americans were suddenly forced
to observe how horrible some of these parasitic diseases can be. So,
how many wormy infections are out there? Well, Stoll starts
by noting how bad the data for an analysis like
this are. There's just not great surveys that are comprehensive.
But he set out to do his best. What he
(01:10):
concludes is that there were two point two billion wormy
infections and a population of just under two point two
billion people at the time, so this isn't counting the
number of parasites in people. One infection would be like, okay,
you have one of a particular kind of nematode in someone,
But these infections were not evenly distributed. On average, one
(01:34):
out of every three Americans or Europeans were infected, but
in the USSR that number was up to two out
of three people. For every three people in Asia, the
Middle East, and South America there were four infections, so
that means out of three people, one of those people
is probably harboring two different wormy parasite species, and every
person in Africa on average was estimated to harbor two
(01:58):
helminth parasite species. But Stole notes a bit of optimism
and points out that six out of the seven cases
of wormy infections could have been stopped with proper sanitation,
so there's some ability to do something about this. So
how far have we come since nineteen forty seven. Well,
in some areas we've made great progress. For example, Stole
(02:21):
mentioned that a nematode called Trichinellus brellus was known as
the most serious parasitic disease in New England. At the time,
one in six Americans were infected with this parasite. Now,
triconilosis is a rare disease in the United States, with
only about fifteen confirmed cases in the entire country per year.
(02:41):
And today we're going to be talking about this public
health success story, but in future episodes, we're also going
to talk about some parasites that still plague humans worldwide,
including here in the United States. For example, according to
the World Health Organization, one and a half billion people
are infected with nematode parasite that are picked up from
the soil. All right, so let's dig in. Welcome to
(03:04):
Daniel and Kelly's extraordinarily wormy Universe.
Speaker 2 (03:21):
Hi.
Speaker 3 (03:21):
I'm Daniel, I'm a particle physicist, and I've never been
infected by a parasite to my knowledge.
Speaker 1 (03:28):
I'm Kelly Wiener Smith, and I bet Daniel has been
infected at some point. And if I had to guess,
there'd be a good chance that you would have gotten
pinworms from your kids when they were young.
Speaker 3 (03:38):
Ooh, pinworms are those the ones I'm thinking about that
make you itching a very uncomfortable place.
Speaker 1 (03:42):
That's right. I think Actually at some point we should
have a whole episode on pinworms, cause why not. But
oh nope, maybe not. Daniel is going to be a
long couple of years working with me if pinworms give
you the eb gbs.
Speaker 3 (03:57):
It's just that particular itch just really gets me, if
you know what I mean.
Speaker 1 (04:01):
No, No, I get it, I get it. Actually, the
mom nematode sneaks out at night and deposits eggs with
like a sticky substance in the spot that you're thinking of,
because scratching is how the parasite transmits, how it gets
under fingernails and then ends up in the environment and
then ends up getting eaten, so that it is very
purposefully caused by the parasites.
Speaker 3 (04:20):
I know, And I use that story as a way
to dissuade my kids from biting their fingernails. Oh good,
because I'm like, you know what you're doing, you know
where you're gonna get itchy if you keep doing that
and it works, it works.
Speaker 1 (04:32):
No, I bet yeah. People feel real gross when you
tell them about parasites. It's a good way to dissuade people.
From certain bad behaviors, no doubt.
Speaker 3 (04:39):
All right, So, since we're being personal, what is the
grossest parasite you've been infected by?
Speaker 1 (04:44):
Oh, gosh, that I've been infected by. Well, I guess
if my parasite we're including viruses and bacteria, I guess
anything that makes me puke. But I haven't been infected
by anything that gross. But now, I had an antibiotic
resistant wound near my ankle once and that was gross
because I just wouldn't go away, and that was kind
of scary, and I was super stressed, which I think
(05:05):
was like suppressing my immune system too, and so it
was bad news.
Speaker 3 (05:09):
What about you, Well, to me, being infected by a
little microbe, isn't that gross? It's like, yeah, that's invisible.
The bigger it is, the weirder it is, the more
gross it is. Like being infected by something that's like
actually a worm size to me is creepy. It's like
crawling around inside you. And so like, imagine being infected
by something larger, you know, baseball sized or like football size,
(05:30):
that would be like, oh, that's nightmare fuel for me.
But yeah, I don't know that I've ever had a
worm inside me. But apparently Kelly things that I have,
So maybe I am a wormy.
Speaker 1 (05:39):
I don't actually know that you have me. I'm sure
your hygiene is impeccable and that is probably kept you safe.
But now there's some pretty nasty like as grade worms,
which maybe we'll talk about at some point. They are
really big, and when you see surgeries where people are
like trying to remove many of them from someone's that
even grosses me out. I can't eat pasta for days exactly.
Speaker 3 (06:02):
Well, I appreciate you giving me the benefit of doubt.
Although physicists are not exactly famous for their hygiene. You know,
that's not like top ten ways you become a physicist
or things we're famous for. But you know, I appreciate it.
I do try to keep clean. Thank you very much.
Speaker 1 (06:16):
You're welcome. I was thinking about you as a human
being and not really a physicist in particular.
Speaker 4 (06:21):
You know.
Speaker 3 (06:23):
That doesn't work in my favor. Yeah, all right, but
today we are not talking about Daniel's hygiene. We're talking
about humans more generally.
Speaker 1 (06:32):
Yeah, and we're talking about them because we got a
great question from a listener named Patrick, And let's go
ahead and listen to that question.
Speaker 3 (06:38):
Now, how many parasites are living in all of us,
how common are the bad ones? And where do we
pick them up? Oh? Man, it sounds to me like
Patrick is looking for nightmares.
Speaker 1 (06:50):
Oh it sounds to me like Patrick is giving me
my Christmas present early by allowing me to talk about parasites.
And so, you know, at the intro, I talked about
how in nineteen forty seven there was this estimate that
there's two point two billion parasitic infections and a population
of under two point two billion people. So some people
are infected by more than one parasite. And I wasn't
(07:11):
actually able to find a comparable estimate for now, And
I think partly that's because the way he grouped parasites
together is not really a biologically relevant category that people
care about anymore, and so I wasn't able to find
a comparable number. But I am going to go through
some of the main parasitic infections that have plagued humans
in our recent past, but we managed to get rid of,
(07:34):
and then some that are still a problem today in
the United States and in other parts of the world.
But I figured today we would start with a success story.
Speaker 3 (07:43):
That's good because I was afraid that the message of
this episode was going to be like, there's parasites everywhere,
all up in your eyeballs and in your earballs and
in your noseballs and everything.
Speaker 1 (07:53):
Well, you know, especially if you live in the United
States and you're lucky enough to be in an area
where there's really good sanitation, you probably are pretty safe.
But you know that's not necessarily true in other parts
of the world. We're very lucky here.
Speaker 3 (08:08):
All right, Well, let's dive in, because I want to
know by the end of this episode how likely am
I to have worms living inside me? Right now?
Speaker 1 (08:15):
Well, we're only talking about one worm. And I was
interested in figuring out what people know about this worm,
because at least in the United States, infections are very
uncommon these days, About fifteen cases of infection with this
parasite are recorded per year for a disease that once
infected one out of six Americans. So we've made a
lot of progress, and so I was wondering have people
(08:36):
heard about this before? So I asked our audience, what
is trick andilosis?
Speaker 3 (08:40):
Right? And if you would like to play on this
segment of the podcast in the future, please don't be
shy we'd love to have your voice. Write to us
to questions at Danielankelly dot org. So before you hear
these answers, think to yourself, do you know what trick
andilosis is?
Speaker 1 (08:55):
Also known as trick and osis?
Speaker 3 (08:57):
Uh no idea the osis at the end.
Speaker 5 (09:01):
It sounds like it could be some kind of disease
or medical conditions.
Speaker 2 (09:05):
I'm too excited for words. This isn't about cats and
uncertainty and quantum mechanics and things I don't understand. This
is a worm. It's a parasite. It grows in pork mainly.
I grew up in India and it was a real
risk that we'd get this, So we had pork that
was like leather. You could have put it on your
feet and worn it as a shoe.
Speaker 4 (09:27):
Disease associated with a parasitic infection of a round worm
from cysts from muscle from undercooked meat, pork and other
animals as well. I believed.
Speaker 5 (09:41):
By bacteria. Worms go drinkinglysis is an infection drinking alact
could be a gear or maybe a braasite. I'm not sure.
Trichinosis is a human disease caused by a pair of
worm in pork.
Speaker 6 (10:01):
I think tricknosis is a disease that one can contract
from eating undercooked meat. I don't know if it's a parasite.
If Kelly's involved, I assume that it must be.
Speaker 3 (10:13):
Though no idea. Sounds like a bacterium. Trichinosis sounds like
the disease that happens to my third chin, and I
don't know anything more about it.
Speaker 4 (10:23):
I have no idea what trickynosis is. However, taking a
stub in the dark, I'm going to say parasite, but
only because the email asking the question came from Kelly.
If the email asking the questions coming Daniel, I would
have took a stub in the dock and said a particle.
There we go.
Speaker 3 (10:40):
Tricenosis involves a trial by a tricycle and tragedy.
Speaker 1 (10:47):
So, Daniel, it is so clear to me that our
audience has us totally figured out it is about a
parasitic worm.
Speaker 3 (10:54):
And you know, just because the email doesn't come for
me doesn't mean it wasn't particles. I mean, I assume
these parasites are made to particles. They're not like fundamental
parasites in the universe or anything. These aren't string theory parasites.
Speaker 1 (11:04):
Are they not posts quantum gravity parasites, nothing like that.
These are actual parasites. And I am always so amused
by the wonderful answers you all give when you don't
know the answer, like probably it's goblins and that was great.
Speaker 3 (11:20):
All right, So give us the context. Take us back
in history. When did we first learn about this particular worm.
Speaker 1 (11:26):
Well, the first documented case where someone figured out that
this worm was causing an infection was from eighteen thirty five,
So we're in London at Saint Bartholomew's Hospital. Back then,
the way that a bunch of the medical students learned
about infections was that an autopsy or a surgery would
be happening in the middle of essentially what looks like
(11:47):
a theater. Like imagine you're sitting down to watch a play,
but instead you're watching an autopsy.
Speaker 3 (11:51):
The first five rows may be splashed, yes, yeah.
Speaker 1 (11:55):
And this was back before there was anesthesia, so like
amputations were oh through some turns my stomach, that about it.
But it was an autopsy and it was a man
who had died of tuberculosis. And the surgeons in the
middle of the operating theater, they had their scalpels, and
they were trying to like get through the body, and
the scalpels kept dulling, and they were feeling really frustrated.
And when they finally got inside, they got to the
(12:16):
diaphragm and one of the surgeons said, I knew it
a case of sandy diaphragm.
Speaker 3 (12:22):
Sandy diaphragm, sandy diaphragm.
Speaker 1 (12:25):
And so one of the guys who was in the audience,
his name was John Paget, He was a medical student,
and he said, what causes sandy diaphragm? And this is
the thing that was dulling their scalpels. And the surgeons
were like, we don't know. Let's go to life.
Speaker 3 (12:40):
Well, what was the general state of medical knowledge? Like
was the inside of the human body a total mystery?
And we mostly figured out like the circulatory system and
the digestive system and all that. What did we sort
of know about the workings of the human body almost
two hundred years ago?
Speaker 1 (12:53):
I think that if you went to a surgeon, it
was like a fifty to fifty chance the surgeon made
things worse. We'd a medical historian, so maybe the odds
were better or worse. I don't really know. We knew
a fair bit, you know, Like we knew that if
someone had a cancerous growth, you'd try to cut it
off real fast. But we didn't have anesthesia, so sometimes
you'd get an infection and you'd die from that. It
(13:15):
was a dicey time to be someone who needed the
help of a professional.
Speaker 3 (13:20):
And this is before germ theory, right, So we didn't
understand there could be microscopic organisms infecting or was this
after germ theory.
Speaker 1 (13:28):
Luayne Hook had been able to see his little animacules,
so we knew that there were like tiny little organisms
in the world. I don't think we had germ theory,
and Lister hadn't figured out ways to establish antiseptic technique.
That is all off the top of my head. And
maybe we should have like Lindsay Fitzharris, who's this amazing
(13:51):
historian of like surgeries and stuff on the show, to
give some background there.
Speaker 3 (13:56):
Because I thought that like middle of this century, we
still have folks like going from cadavers to delivering babies
and wondering like, hey, why are so many women dying
in childbirth? What a mystery? And maybe we should wash
our hands.
Speaker 1 (14:09):
Yeah, No, that is where we were yeah. Okay, we're
still before the germ theory. Okay, yeah, yeah, And I
think that you know, if they amputated someone's limb, they'd
kind of like wipe it off with the napkin maybe,
and then amputate the next person's limb. There were lots
of microbes being shared between people at this time.
Speaker 3 (14:24):
All right, But sandy diaphragm is not due to microbes, right,
It's due to actual visible worms.
Speaker 1 (14:29):
It's due to actual visible worms. They are not easy
to see. So what Paget did was he took a
sample and he used a hand lens and he squished
it between two glass slides, and he looked at it
with the hand lens, and he thought he saw something
kind of wormy, but he wanted to get a better
look at it, so he brought it over to the
British Museum of Natural History, and he actually knocked on
the door of the guy who came up with Brownie
(14:50):
and the idea behind Brownie in Motion. So he knocked
on Brown's door, and he had a microscope. He let
Paget use it, and Paget noted that there was actually
a worm there. Some of the worms were moving and
some were not, and the ones that were not had
been calcified by the human body and that's what was
causing the sandy diaphragm. So when these worms die, the
(15:12):
immune system responds by sort of like creating like a
calcified casket to like walllet off from everything else, and
over time that creates like hard structures, and that is
what the scalpels were dulling on. So he goes and
he tells a group of medical students about his finding,
but he doesn't take the important next step of publishing
and sharing his results more widely. The same cadaver, a
(15:36):
sample of it, got sent to this other guy named
Richard Owen, and we don't need to get into too
much detail here, but he also from the same cadaver,
ended up looking and seeing these worms. He wrote it up,
he gave a public lecture. He's the one who got
the credit. But this one cadaver produced two different people
who were the first to notice that actually there were
these little, tiny worms, and so it used to be
(15:58):
called traquina. I think what which is a word for
like tiny hair and spiralis is, you know, like the
spiral shape, and so these are hair shaped worms that
curl up in a spiral inside of cells like direphram cells.
But Trickina also was a genus of flies, and so
they went with Trickinella to avoid confusion. So hair like
spirally things.
Speaker 3 (16:21):
And take us back also scientifically, like if you find
worms in a body, at that point, do you have
to assume that somehow the people have eaten them or
they've invaded the body, or are we still in a
place where like we don't understand whether life can be
generated spontaneously.
Speaker 1 (16:37):
So we and Hook and Pasture I think they had
already done their experiments at this point where you know
that there's little things and you know that those little
things aren't generated spontaneously, because Pasture and I think some
other people as well had done those experiments where they
had made those flasks that had the like bendy mouth
parts so that the air couldn't sort of get in.
(16:59):
And whenever air can't get in and you had like
a nutrient broth, nothing would grow in it. But if
air could get in, you would get growth. And so
it's not arising spontaneously. You have to have something seating
the living things. I'm sure that people had seen parasitic
worms before but I don't think we had a very
good handle on life cycles.
Speaker 3 (17:17):
All right, What exactly was new and novel about this?
What did this tell us about parasites and humans and
all that kind of stuff.
Speaker 1 (17:25):
So I don't think that this is the first parasitic
disease that was ever discovered, but I think this is
a problem that was attributed to a parasitic disease at
this point. So like this person in particular had died
of tuberculosis. I think it was a while before we
realized that this was something that could kill people as
opposed to just something that's a pain in the rear
end when you're trying to run a scalpel through a
(17:46):
dead person's body. But even today, if you get infected
by too many of these all at once, you can die.
So let's talk a little bit more about what they
actually discovered when we get back from the break. Okay,
(18:14):
So what they had discovered was trick and ellis barrellis.
This is a nematode. So they've got like a hard cuticle.
They kind of look like earthworms, but without the segments
and the ones that we're talking about, the ones that
cause trick and e loosis they're very tiny, so they're
much smaller than normal earthworms. Do you feel like you've
got that image in your head.
Speaker 3 (18:33):
I'm imagining something that looks basically like a human hair
and it's curled up. Yeah, and if you zoom in
on it, it looks sort of like a worm.
Speaker 1 (18:40):
Yeah, it comes to points at either end, but yes,
kind of like a human hair, except points at the ends.
And so what happens is if you eat meat that's
infected by this parasite and that meat's not cooked through
all the way, the parasites burst out of the cells
that they've been living in. So as your body is
digesting the food, it also digests the cells they've been
living in and that releases them.
Speaker 3 (19:00):
So they've been living inside the cells. Like I'm eating pork.
Then these worms are inside the cells the pig, not
swimming around between the cells.
Speaker 1 (19:08):
Yeah, and this is not something that's super common for
wormy parasites to do, but this is something that this
particular species does. They live inside the cells, and they
can live inside the cells for like thirty years, like
incredible amounts of time.
Speaker 3 (19:20):
So they're smaller than like a pig cell.
Speaker 1 (19:23):
And they get into the pig cell, they expand the
size of that cell. Oh well, get there. I'm so
sorry about the next few years of your life, Daniel.
And so they burst out of the cells, they find mates,
they produce live smaller worms, and the smaller worms get
into your bloodstream or the circulation for your lymph, and
then they end up all over your body. But they
(19:45):
can only move in and live into skeletal muscle cells.
And so when they end up in like your heart
or your brain, they try burrowing into those cells and
then they're like, oh, this isn't home, and they borrow
back out again.
Speaker 3 (20:01):
Because we have two different kinds of muscle cells, right,
smooth and skeletal. Is that right?
Speaker 1 (20:05):
Three types cardiac, skeletal and smooth.
Speaker 3 (20:09):
Oh all right, cool? So why can they only live
in one particular kind of muscle? Is the shape of
the cell, the size of the cell, the kind of
food they get inside or.
Speaker 1 (20:17):
I don't think we know the answer to that. But
they do end up manipulating these cells. They are born
about a week after you eat the infected meat, and
they're going on this journey. And so about a week
after you eat the infected meat, this is when you're
at the highest risk of dying because if you ate
a lot of parasites in that meat, they're all having babies,
they're all releasing babies, and those babies are like maybe
(20:39):
if they end up in your brain, destroying a bunch
of brain cells or destroying a bunch of cardiac cells.
And at this point you're often given medication to reduce inflammation,
because that's a big part of what is causing trouble here,
the inflammation as a result of the parasites moving around,
And sometimes you're given anti parasite medication. But this is
the most dangerous phase of the process.
Speaker 3 (20:59):
And in order to be a risk of like dyeing,
you must need to have lots and lots of these parasites.
Can one worm or two worms generate like an avalanche
of these things? Or do you need to eat a
lot of the meat you have like a big initial population.
Speaker 1 (21:12):
Yeah, the more that you eat initially, the worst shape
you're going to be in. So if you just happen
to eat one or two cells that have the parasite,
you're probably gonna be fine.
Speaker 3 (21:21):
You're still going to have parasites inside you. You're just
not going to die. That's what you call it fine.
Speaker 1 (21:26):
I mean, for most of our revolutionary history, that would
have been lucky, just one or two parasites in you.
But yes, it won't be a dire situation, I guess.
But so when these parasites do find the cells, they're
looking for the skeletal muscles they burrow in and now
this is when they start manipulating the cell. So they
call the cell a neur cell. They like secrete some
(21:47):
stuff that gets rid of the parts of the cell
that they don't need. They start growing and expanding. The
cell starts getting bigger, and then around the cell, I
think it doesn't recruit the kind of vessels that bring
oxygenated blood because inside the cell you end up with
an anaerobic environment. I don't know why that's necessary, But
so they start bringing the kinds of cells that take
(22:08):
deoxygenated blood away. But in this way, the nurse cell
delivers nutrients and removes waste, and so the parasites are
able to manipulate the cells to become nice homes and
to do things like remove waste and feed them. So
we don't really understand how this happens, but it does.
And Dixon de Pomier wrote this book called Parasites People
(22:28):
in Plowshares, where he argues that if we could understand
how nurse cells work, we could maybe understand like better
ways of like delivering insulin and stuff like that. And
so he's really interested in trying to like physiologically understand
what's happening here. But it's a complicated system.
Speaker 3 (22:43):
So they really have taken over the cell and refashioned
it for their own use. It's no longer doing the
original thing you had that cell for. It's not basically
just like a homestead for these worms.
Speaker 1 (22:53):
Yep, it's kind of amazing. I think that they've managed to, like,
you know, evolve to do this.
Speaker 3 (22:57):
I think it's super amazing when they manipulate their environment
respond in a certain way to take advantage of it. Obviously,
you know this is just evolutionary, right, there's no like
intentional design here. They're not like engineers where they're thinking
about what to do. But they found this strategy. Why
haven't humans responded in an evolutionary sort of way to
create new defenses, Like, obviously this is bad if it
(23:18):
kills you, or even if it doesn't kill you, it
must be bad for you because it's sapping your energy.
Do humans have defenses against this or we just like
total suckers for these worms.
Speaker 1 (23:28):
Well, so some of the worms die and the ones
that die they get calcified. And I think probably some
of them are dying because of an appropriate immune response.
Speaker 3 (23:37):
I'm glad to here's something's happening in the inside to
push back.
Speaker 1 (23:39):
Yeah, yeah, we're doing something. But y know, so for
a lot of parasites, the deal is that they, through
this evolutionary arms race, have just found ways to evade
the immune system, to just make the immune system things
it's not even there. And then other times it's more
about like and I'm going to make this sound super anthropomorphic,
and it's not like a decision that the body's making,
like it's thinking about it like a person. But this
is a process overtionary time. But so these worms that
(24:02):
are living in the nurse cells, is it worse for
the body to deliver a tiny amount of energy to
these teeny tiny little worms or to kill the worms
and calcify it. And if it's in your diaphragm, you know,
so like that sandy diaphragm. Yeah, it's a problem for
the scalpel. But probably a diaphragm that's that hard, isn't
doing a very good job of like helping you breathe.
(24:23):
And so if you end up with all of these
calcified muscles, and when a parasite dies, it usually kicks
off an inflammatory response. And so I think over evolutionary time,
the trick isn't attack all the parasites that you have
with your maximum mobility, because when you initiate an immune response,
that often causes damage to the host as well. And
so I think it's a balancing act between what do
(24:44):
I just ignore and what do I have all out
war against.
Speaker 3 (24:48):
I don't know, Kelly, I think you're just a shill
for big parasite. I mean, you're telling me I should
happily live along with these things that have like squatting
in my cells. You're like, isn't it just best for
everybody if you you just give in and give up
some of your energy. Like, I don't know, I think
we're in all out war with these things.
Speaker 1 (25:06):
There are some unpleasant people in my life, and I
think my life is better for ignoring them than for
like trying to attack back. And you know, I don't
think it's that different with the worms and you know,
we should have a whole episode one day on this
old friends or hygiene hypothesis. Are you familiar with this idea?
Speaker 3 (25:21):
Yeah.
Speaker 1 (25:22):
The idea is basically that, like, we've had these organisms
in our body through enough evolutionary time that our immune
systems have come to sort of like expect them to
be there, and now they're sort of used as cues
for how our immune systems should work and how our
immune system identifies self from not self. These things don't
always go in the direction you'd think I wouldn't want
to have any worms in my body, but you know
(25:42):
it's also positible. My body is just like it's not
worth the effort you just ignore.
Speaker 3 (25:46):
Yeah, and Katrina is big on not classifying microbes, some
of them as good or bad because they all play
different roles and it's complicated, and you know, you might
imagine you don't want to be infected, but obviously lots
of microbes are essential for your life, the fermentation that
happens in your gut, all that kind of stuff. Is
it possible that parasites like these worms are playing some
(26:07):
positive role that we're benefiting from. I mean, you call
them a parasite, which implies that we're not getting anything.
There's no commensural reaction here. But are there any benefits
to having these worms live inside of us?
Speaker 1 (26:18):
I don't think there's any documented benefit from having Trickenellis
barrellus inside of you. There are some other parasites that
people have been experimenting with where when you infect people,
like their hay fever symptoms go away, or their crone's
disease symptoms become less severe, or their MS goes into
remission or whatever the right word is for that. But
(26:40):
those studies are super complicated. Sometimes you get good results,
sometimes you don't. It seems to depend on the parasite
genome or maybe the exact person's genome and the exact
kind of problem they have. And I think science is
like really working through digging through that right now, and
right now we're at a like what is happening phase,
But we should invite an expert on one day to
(27:01):
talk about that.
Speaker 3 (27:02):
I'm just trying to get mentally prepared because you know,
I've learned now the bacteria it can be good for you,
and even leeches can be good for you. So hey,
maybe in the future we'll all be intentionally injecting worms
into our children.
Speaker 1 (27:13):
There are a community of people who are intentionally infecting
themselves with parasites right now. I think most of them
are not doing that to their children, I hope. But
in my mind, the ideal thing isn't that we all
take like five hookworms for breakfast and call it a day,
but that we figure out what cues the parasites are
giving our immune system, and then we can like take
a probiotic pill or something that like replicates those cues
(27:36):
so we don't actually have to have the parasites there.
But I agree with Katrina that I think we are
at a point where dichotomizing things as good and bad,
we're realizing sometimes it's a little bit more complicated and
it depends on context.
Speaker 3 (27:47):
And I think the point you made is really interesting
that we can learn from them how to manipulate our
own bodies. Like if they have spent millions of years
evolving strategies to pull chemical levers inside the body, we
can take advantage of that, right. If we understand the
techniques that they have stumbled into, we can maybe use
them intentionally to understand the workings of our own system.
Speaker 1 (28:08):
Yeah. Yeah, sometimes the parasites that manipulate host behavior. We
sometimes refer to them as evolutionary neuroscientists. And there's you know,
like a whole group of people like me who write
our NSF grants about how we can understand host behavior
better by trying to figure out what parasites have quote
unquote learned through natural selection. All of this across all
these years.
Speaker 3 (28:26):
So these guys set up a home in these nurse cells,
make them work for them. How long do they hang out? Like,
do they live as long as the cells live? Do
they have like generations and generations of worms inside one cell?
Or does a single worm last a long time?
Speaker 1 (28:42):
So there's no reproduction happening at this stage. But worms
can live it looks like for twenty five plus years.
Speaker 3 (28:47):
Twenty five years. Oh yeah, gosh, so they can vote
and you know, buy alcohol and stuff like this.
Speaker 1 (28:53):
Yeah, absolutely, because that's what they're doing. But no, they
live for a really long time. And I mean they've
got like a nice setup. You know, food is being
delivered to them, their wastes are being removed, so yeah,
they can live for a really long time. But they're
not reproducing. They're just like biding their time until the
muscles that they live in get eaten by something else.
Speaker 3 (29:09):
And are they squirming around a lot? Because for some
reason that makes them a lot worse. Like if you're
just quietly hanging out inside my cell and stealing some food, okay,
but if you're like squirming around, then it's Oh, I
just can't tolerate that.
Speaker 1 (29:21):
You know, I would like to exercise every day. So
I guess I hope that they're like running laps and
their little nurse cells. But I think they're generally not
moving much. And if they are, you're not feeling it.
Speaker 3 (29:30):
See, you're pro parasite. There you are again like advising
the parasites how to live their best life inside people.
Speaker 1 (29:36):
Well, you know, we all need to stay healthy. So
you know, you might be asking yourself, if you want
to avoid being a track for parasites, how do you
do that?
Speaker 3 (29:46):
Yes, tell me.
Speaker 1 (29:47):
For a long time it was difficult. So most of
us get this parasite from pork, and so pigs get infected.
It's in the pigs muscles. And if you eat pork
that hasn't been cooked through enough, that's how you get infected.
And pork, you know, in the eighteen eighties, the United
States was like a world exporter of pork. It was
a huge industry for US, and it ended up being
(30:07):
a big problem for US because Europeans decided that because
we weren't checking for trick and ella, we weren't checking
for this parasite, that we were causing a bunch of
trick and alsis outbreaks in Europe. And so for a
while they stopped importing pork from US, and this was
a big problem for our industry. Some Americans went over
there and they were like, no, and they figured out that, like, no,
(30:30):
it's not necessarily our pork that's causing the problem. Like
maybe maybe sometimes it's American pork that's the problem, but
like it's not like all of our pork is wormy.
But you know, it was a good goal to try
to reduce the worminess of our meat. And so how
did we do that?
Speaker 3 (30:44):
But wait, hold on a second, why pork? Like do
these parasites prefer pig cells to cow cells for some reason?
Do cows have the kind of muscles that they can't
get inside? Why pork?
Speaker 1 (30:54):
Okay, so part of it has to do with the
animal's diet. So pigs eat everything like a thing of
getting pigs on our farm so that all of our
food waste goes into pigs. But then I couldn't turn
them into bacon because they'd be like friends. I'd probably
name them wilburm. So pigs eat everything, including other pigs.
Speaker 3 (31:11):
Pigs are cannibals, yep.
Speaker 1 (31:12):
Pigs are cannibals. Yep. I need to be excited about that.
So when a pig dies, another pig will eat its
infected muscles, and then they'll get infected. Oh, so part
of it has to do with diet. There were also
some like rodents, who would eat dead pigs, and then
other pigs would eat the rodents, and so for a while,
rodents were part of the transmission cycle here. Cows tend
(31:32):
to not eat meat, but like horses, can get infected.
And horses don't usually eat meat, but sometimes they will,
so like a lot of animals that we think of
as non meat eaters, will eat meat every once in
a while if you give it to them and they're
in the right mood. And so there have been cases
of horses getting infected.
Speaker 3 (31:50):
We even learned on the podcast recently that bees sometimes
eat meat, right.
Speaker 1 (31:54):
That's right, yes, yes, meat, honey, m m yeah, And
so I think the reason that cows often don't get
infected is because they're just not eating meat. So trick
Andella spiralis is one trick and Ella species. There are
other trick and Ella species that seem to specialize on
other animals. There's like in the United States, bears and
moose and wild boars, some of them can get infected
(32:17):
by trick and Ella spurrells. But there's also other trick
and Ella species that are more common in nature that
they can get infected with. But then we can get
infected by those if we don't cook the meat through.
And so there is some chance that I carry some
trick and Ella in me because I ate bear once
that I don't think was cooked through.
Speaker 3 (32:36):
All the way you ate a bear? What I had
to hear that story? When did you have a bear not.
Speaker 1 (32:41):
A whole bear? I was working with some folks in
the Wisconsin Department of Natural Resources and they were nice
enough to invite us to their annual social gathering and
a bunch of people brought stuff that they had hunted,
and there was barbecue bear. And so I mean, I've
eaten bear. I'm gonna assume they cooked it through all
(33:01):
the way. But I've also eaten smoked moose heart. Oh,
but it shouldn't be in the cardiac muscles, so that
should be fine because it's in skeleton muscles.
Speaker 3 (33:10):
Yeah, there you go, it's smoked moose heart.
Speaker 1 (33:12):
Knowing is half the battle.
Speaker 4 (33:13):
You know.
Speaker 1 (33:14):
The smoked moose heart was gross, Like when it got
pulled out of the bag, it still had like fat
on top of the heart. But it was like a
collaborator of mine who was from a part of the
world where this was. Anyway I pushed.
Speaker 3 (33:26):
Through, You're going to turn me into a vegetarian killing.
Speaker 1 (33:28):
Again, right back to your vegetarian root exactly.
Speaker 3 (33:32):
Here we go.
Speaker 1 (33:33):
So let's back up. Okay, so you know you can
get it from pork, but you don't get it from
pork in the United States much anymore. So what's changed.
So in the nineteen fifties, we made it so that
people were no longer allowed to feed their farmed pigs
uncooked garbage, which is such a gross phrase to hear.
Speaker 3 (33:52):
I think you have to cook your garbage if you're
going to feed it to pigs.
Speaker 1 (33:55):
Yeah, So, like you know, nowadays, factory farms don't feed
pigs anything you would just call garbage. I mean, I
guess maybe people would want to call it garbage, but
it's not actually garbage the way these animals were being
fed garbage before. But for a while the change was
just you had to cook it through, and if you
cook it through enough, then any of the effective stages
of the parasites are dead. And so that was a
stage of improvement.
Speaker 3 (34:15):
All right, So barbecued garbage is okay, or slow roasted
garbage as.
Speaker 1 (34:19):
Long as the internal temperature in the middle of the
garbage reaches one hundred and sixty five degrees fahrenheit, yes,
you're probably fine.
Speaker 3 (34:26):
Maybe a souvied then, because that's really good temperature control.
Souvid garbage that's where they serve at pig restaurants.
Speaker 1 (34:31):
Oh so disgusting. So like, up until nineteen eighty five,
we weren't really sure how pigs were mostly getting infected.
But you know, we've talked about how cannibalism and rats
contribute to infection. That was also like, sometimes if pigs
and wildlife were interacting, I think most often the pigs
were infecting the wildlife, but sometimes the wildlife could infect
the pigs. But once we sort of figured all of
(34:53):
this stuff out, we were able to say, like, Okay,
first of all, you have to make sure your pigs
aren't able to eat the other pigs if they die.
You have to make sure you don't have any rats
in with your pigs, which I'm sure is hard.
Speaker 3 (35:06):
Yeah, that sounds hard because rats are everywhere.
Speaker 1 (35:08):
Oh my gosh. Yes, we live on a farm. Rats
are everywhere. It's hard to keep them out, but you
need to make a good effort to do it.
Speaker 3 (35:14):
Well, let me ask you, how do you feel about
the rats? Because I have this policy no rats inside
the house, but outside the house. Like, hey, you guys
were here before us. What am I going to do
kill all the rats? That's impossible?
Speaker 1 (35:25):
Well, okay, so the rats that we had in our
chicken coop were an invasive species, so they didn't really
belong there. These were like the lab rats, Norwegian rats
that had gotten out, and rats like usually I agree,
but so that we have really stupid chickens, and like
the chickens would be eating at their feeder and the
rats would be like right next to them eating and
(35:45):
they just kind of look at them and be like hey, Frank,
and they wouldn't do anything. But so then the rats
were living in the rafters above and they were just
like defecating an incredible amount.
Speaker 3 (35:55):
They do that.
Speaker 1 (35:55):
They do that, and there are some diseases you can
get from rat feces and from mouth hauntavirus. Yeah, right, exactly.
And so if it's just like, yeah, I try to
never kill wildlife, because I agree you were here first.
But when it's like, well, if my daughter goes out
to bring the chickens food and she's gonna get haunt virus,
like we've crossed the line and we have to get
rid of the rats.
Speaker 3 (36:16):
Also, wait, you live in Virginia, which is not that
far from the NIH, right, and you're talking about rats
that have escaped from labs. Are you basically living the
rats of nim That was.
Speaker 1 (36:28):
A great movie. These rats, they are the species that
we use in the lab. I don't know that they
escaped from the lab. They could have just like come
off of ships or something.
Speaker 3 (36:37):
Keep telling yourself that science has made.
Speaker 1 (36:40):
Some mistakes, no doubt about it. I'll own up to that.
Speaker 3 (36:43):
Well, we had rats as pets once, and rats are wonderful,
wonderful pets. They're smart, they're affectionate, they're really cute. They
do poop everywhere though, Yeah, that is definitely a problem.
Speaker 1 (36:53):
I also had rats as pets when I was a kid,
and I thought about getting one again the other day
because I did. Used to love just having like a
little on my shoulder and they make this cute little noises. Yeah,
I like rats a lot.
Speaker 3 (37:04):
My daughter would bike around the neighborhood with a rat
in her hood of her hood, riding along with her.
It was super cute. Yeah, anyway, you're saying, if you
have pigs and rats, try to keep the pigs from
eating the rats.
Speaker 1 (37:15):
Yes, try to keep the pigs from eating the rats.
And so once we figured this stuff out, it became
clear what you needed to do to keep the pigs
from getting infected. And once you knew what you needed
to do, you could pass laws to make sure that
people are doing these things. And by putting in the
right sort of like procedures in place and then coming
up with some better ways to test meat to see
(37:36):
if it's working, we have managed to mostly eradicate this
parasite in pork from factory farm amazing, but there's still
some ways that you can get it, which we'll talk
about after the break.
Speaker 3 (37:50):
More nightmere fuel, don't worry.
Speaker 1 (37:52):
That's right. We were just talking about how pigs from
factory farms in the United States tend to not have
(38:14):
this parasite anymore. And actually in twenty twenty four there
was a study where they sampled three million pigs and
none of those pigs from factory farms had trichinella.
Speaker 3 (38:25):
Amazing.
Speaker 1 (38:26):
Wow, that is incredible. Like if you think that we
have gone from one in six people in New England
having this parasite infection, which can kill you sometimes, to
testing three million pigs and none of them have it,
that's an incredible decline.
Speaker 3 (38:41):
That means all those people who were infected when they died,
nobody ate them and then absorbed the infection, right, including
the pigs.
Speaker 1 (38:48):
That's right. Yes, I should have known you were going
to go there. My bad, But yes, that means that
there's not a lot of human cannibalism going on. Good news.
Speaker 3 (38:56):
And of course I'm going to ask if pigs can
get from eating other pigs, that means humans could get
it from eating other humans, right yep, yeah, okay, one
more reason not to eat your children.
Speaker 1 (39:05):
Yes, yeah, well, you know, if they're young enough, maybe
they haven't been exposed and they move it on.
Speaker 3 (39:11):
When their meat is still so tender.
Speaker 1 (39:13):
Oh God, why do we do this?
Speaker 2 (39:16):
All? Right?
Speaker 1 (39:17):
So, now there's about fifteen confirmed cases in the United
States a year, which is an incredible drop, and there's
about ten thousand cases recorded throughout the world per year.
And I think a lot of those cases are in
places like China where they eat a lot of pork,
but maybe they don't have the same sort of procedures
in place to make sure that the pigs aren't eating
(39:38):
each other or being exposed to rats. And so there
are other places in the world that you can go
where if you eat pork you could get infected.
Speaker 3 (39:46):
So how's it happening in the US if there were
no examples in all of those pigs where people get
and they're just getting it from the wild again, or
they're eating weird smoked moose hearts or something.
Speaker 1 (39:57):
So I think a lot of people do get it
from animal that they hunt. So you can get it
from bears, you can get it from moods, you can
get it from wild boar. And also, you know, if
people have pigs in their backyard, they are not necessarily
following all of the rules that like the USDA mandates.
So it could be that their pigs are encountering wild
animals that they're eating or then eating each other, and
(40:20):
so you could get it from like backyard pigs. The
good news is if you cook your meat where the
inside reaches I think it's one hundred and forty five
degrees fahrenheit, then the parasite dies. The bad news is
if you freeze the meat, even for something like two months,
that doesn't necessarily kill Trick.
Speaker 3 (40:40):
And Ella w Yeah, can survive freezing.
Speaker 1 (40:43):
It's amazing. Yeah, So like there have been cases where
meat has been frozen and two months later it's come
out of the freezer and when it thaws, those worms
start moving around again. This is mostly the wild strains
or the wild species. Maybe it's not too surprising because
like bears can hibernate, they get really cold. But still,
the fact that they can freeze, that's amazing because bears
aren't freezing through when they're hibernating.
Speaker 3 (41:04):
Yeah, And I thought that most cells when they freeze,
they burst because water expands as it freezes. So how
do these guys survive it?
Speaker 1 (41:12):
I mean, I'm guessing some of them do have nurse
cells that burst and they die. But most of the
food that we plan on eating we freeze quickly because
when those cells burst, that food doesn't taste as good.
And so like you want to freeze your food quickly
so the cells don't burst, because that's a better way
to eat a hamburger or a bear steak. So I think,
(41:32):
you know, the parasites are benefiting from that and they
can survive. And then also if you prepare jerky out
of bear meat, that processes preparing the jerky doesn't always
kill the parasites. These parasites, you think about it, like
they transmit when the animal that they die in gets
eaten by something else, and that doesn't always happen immediately.
So they need to be able to like survive the
(41:53):
death of the animal for a while and persist in
the environment to increase the probability that they get eaten
by something. Yes, yeah, so most of the cases in
the United States come from wild animals that have been
killed and then not cooked through all the way. In
other parts of the world, you can get it from
pork because they don't have the like public health procedures
that we have in place here in the United States.
(42:15):
But I'm excited about this system because it's a pretty
clear example where doing the basic work to understand the
life cycle of the parasite and then putting that information
in the hands of people who can like set up
procedures was able to save I think many many lives, Yeah,
and also just be less creepy, Like maybe not a
lot of people were going to die, but it's really
(42:35):
nice to know that we don't have like parasites running
laps in our diaphragms in the United States.
Speaker 3 (42:43):
So you're a parasitologist, you know, the cutting edge of
parasite science. We've mostly told the historical story today, but like,
what are people working on right now? If you go
to trichinosis conference, what are the presentations about, what are
the questions that people are asking.
Speaker 1 (42:59):
Yeah, so one of the main topics here is trying
to figure out when an outbreak happens. So there are
still outbreaks. I was listening to someone's talk the other
day and it was somewhere in Scandinavia there was an
outbreak on farms and it showed up in a couple
different farms, and so they were collecting samples of the
parasite and then they were genotyping it. So they were
(43:20):
getting like the whole genome of the parasite, and they
were trying to use that information to find out did
the parasite jump from a wild animal, you know, where
the pig's able to go out in the field one
day and they ate a wild animal and that's how
they got infected. But by figuring out what species or strain,
then they can try to figure out like where the
procedure for keeping this parasite out of our food system,
(43:43):
like where that broke down. And so they're using genetic
information to sort of do the tracing stuff here. They're
also still trying to figure out how this nurse cell works,
you know, how does it manage to manipulate the human
body into essentially like waiting on it hand and foot
without killing it. And you know, also like wildlife ecologists
are probably interested in what trick and ella is doing
(44:04):
to like wild bear populations and stuff like that. So
I think those are the main topics we're dealing with
right now.
Speaker 3 (44:10):
So this all sounds surprisingly positive. You're saying this is
a success story. Is this typical killing or is the
wider world of parasites a darker world?
Speaker 1 (44:19):
Well, the wider world of parasites can be pretty dark.
So this was a nice case where we figured out
how the parasite was transmitted. It was pretty clear what
we needed to do, and it wasn't that hard to
implement the changes. But there's other parasites where we know
what it would take to eradicate the infection. But like
for example, bringing the appropriate sanitation measures to the people
(44:41):
who need it has just proven to be something that
we can't seem to do yet. And so the next
time we talk about this wormy world of ours, we're
gonna be talking about nematodes. And today we talked about
anematode too, but we're gonna be talking about nematodes that
you can get because they burrow through your skin when
you're walking in soil that's carrying these effective stages.
Speaker 3 (44:59):
Oh no, you don't even need to make bad eating decisions.
You can just be going.
Speaker 1 (45:03):
For a walk, or you can be gardening. They're able
to just sort of burrow through your skin. So we
will talk about soil transmitted helmets which have been stubborn
and hard to eradicate. The next time we visit this
warming world.
Speaker 3 (45:16):
There's always more nightmare fuel waiting for you in Biology.
Speaker 1 (45:20):
And Kelly's got it ready for you.
Speaker 3 (45:23):
Thanks everyone, tune in next time.
Speaker 1 (45:32):
Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We
would love to hear from you, We really would.
Speaker 3 (45:39):
We want to know what questions you have about this
Extraordinary Universe.
Speaker 1 (45:44):
We want to know your thoughts on recent shows, suggestions
for future shows. If you contact us, we will get
back to you.
Speaker 3 (45:50):
We really mean it. We answer every message. Email us
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Speaker 1 (45:56):
Dot org, or you can find us on social media.
We have accounts on Instagram, Blue Sky and on all
of those platforms. You can find us at d and
K Universe.
Speaker 3 (46:06):
O't be hye write to us
In nineteen forty seven, doctor Norman Stole gave his presidential
address to the American Society of Parasitologists. His talk was
called This Wormy World, And if you study parasites, this
talk is a real classic. Stole wanted an estimate for
how many people in the world were carrying particular kinds
of wormy parasites. So we're talking things like nematodes, tapeworms,
(00:28):
and trematodes, not the kind of things that cause the flu,
so not bacteria or viruses. So the context here is
that World War II had recently ended, but the problems
for US soldiers who participated in the war had not.
Soldiers returning home from the war had brought back with
them the parasitic diseases that are found all over the world.
(00:49):
US interest in parasites skyrocketed as Americans were suddenly forced
to observe how horrible some of these parasitic diseases can be. So,
how many wormy infections are out there? Well, Stoll starts
by noting how bad the data for an analysis like
this are. There's just not great surveys that are comprehensive.
But he set out to do his best. What he
(01:10):
concludes is that there were two point two billion wormy
infections and a population of just under two point two
billion people at the time, so this isn't counting the
number of parasites in people. One infection would be like, okay,
you have one of a particular kind of nematode in someone,
But these infections were not evenly distributed. On average, one
(01:34):
out of every three Americans or Europeans were infected, but
in the USSR that number was up to two out
of three people. For every three people in Asia, the
Middle East, and South America there were four infections, so
that means out of three people, one of those people
is probably harboring two different wormy parasite species, and every
person in Africa on average was estimated to harbor two
(01:58):
helminth parasite species. But Stole notes a bit of optimism
and points out that six out of the seven cases
of wormy infections could have been stopped with proper sanitation,
so there's some ability to do something about this. So
how far have we come since nineteen forty seven. Well,
in some areas we've made great progress. For example, Stole
(02:21):
mentioned that a nematode called Trichinellus brellus was known as
the most serious parasitic disease in New England. At the time,
one in six Americans were infected with this parasite. Now,
triconilosis is a rare disease in the United States, with
only about fifteen confirmed cases in the entire country per year.
(02:41):
And today we're going to be talking about this public
health success story, but in future episodes, we're also going
to talk about some parasites that still plague humans worldwide,
including here in the United States. For example, according to
the World Health Organization, one and a half billion people
are infected with nematode parasite that are picked up from
the soil. All right, so let's dig in. Welcome to
(03:04):
Daniel and Kelly's extraordinarily wormy Universe.
Speaker 2 (03:21):
Hi.
Speaker 3 (03:21):
I'm Daniel, I'm a particle physicist, and I've never been
infected by a parasite to my knowledge.
Speaker 1 (03:28):
I'm Kelly Wiener Smith, and I bet Daniel has been
infected at some point. And if I had to guess,
there'd be a good chance that you would have gotten
pinworms from your kids when they were young.
Speaker 3 (03:38):
Ooh, pinworms are those the ones I'm thinking about that
make you itching a very uncomfortable place.
Speaker 1 (03:42):
That's right. I think Actually at some point we should
have a whole episode on pinworms, cause why not. But
oh nope, maybe not. Daniel is going to be a
long couple of years working with me if pinworms give
you the eb gbs.
Speaker 3 (03:57):
It's just that particular itch just really gets me, if
you know what I mean.
Speaker 1 (04:01):
No, No, I get it, I get it. Actually, the
mom nematode sneaks out at night and deposits eggs with
like a sticky substance in the spot that you're thinking of,
because scratching is how the parasite transmits, how it gets
under fingernails and then ends up in the environment and
then ends up getting eaten, so that it is very
purposefully caused by the parasites.
Speaker 3 (04:20):
I know, And I use that story as a way
to dissuade my kids from biting their fingernails. Oh good,
because I'm like, you know what you're doing, you know
where you're gonna get itchy if you keep doing that
and it works, it works.
Speaker 1 (04:32):
No, I bet yeah. People feel real gross when you
tell them about parasites. It's a good way to dissuade people.
From certain bad behaviors, no doubt.
Speaker 3 (04:39):
All right, So, since we're being personal, what is the
grossest parasite you've been infected by?
Speaker 1 (04:44):
Oh, gosh, that I've been infected by. Well, I guess
if my parasite we're including viruses and bacteria, I guess
anything that makes me puke. But I haven't been infected
by anything that gross. But now, I had an antibiotic
resistant wound near my ankle once and that was gross
because I just wouldn't go away, and that was kind
of scary, and I was super stressed, which I think
(05:05):
was like suppressing my immune system too, and so it
was bad news.
Speaker 3 (05:09):
What about you, Well, to me, being infected by a
little microbe, isn't that gross? It's like, yeah, that's invisible.
The bigger it is, the weirder it is, the more
gross it is. Like being infected by something that's like
actually a worm size to me is creepy. It's like
crawling around inside you. And so like, imagine being infected
by something larger, you know, baseball sized or like football size,
(05:30):
that would be like, oh, that's nightmare fuel for me.
But yeah, I don't know that I've ever had a
worm inside me. But apparently Kelly things that I have,
So maybe I am a wormy.
Speaker 1 (05:39):
I don't actually know that you have me. I'm sure
your hygiene is impeccable and that is probably kept you safe.
But now there's some pretty nasty like as grade worms,
which maybe we'll talk about at some point. They are
really big, and when you see surgeries where people are
like trying to remove many of them from someone's that
even grosses me out. I can't eat pasta for days exactly.
Speaker 3 (06:02):
Well, I appreciate you giving me the benefit of doubt.
Although physicists are not exactly famous for their hygiene. You know,
that's not like top ten ways you become a physicist
or things we're famous for. But you know, I appreciate it.
I do try to keep clean. Thank you very much.
Speaker 1 (06:16):
You're welcome. I was thinking about you as a human
being and not really a physicist in particular.
Speaker 4 (06:21):
You know.
Speaker 3 (06:23):
That doesn't work in my favor. Yeah, all right, but
today we are not talking about Daniel's hygiene. We're talking
about humans more generally.
Speaker 1 (06:32):
Yeah, and we're talking about them because we got a
great question from a listener named Patrick, And let's go
ahead and listen to that question.
Speaker 3 (06:38):
Now, how many parasites are living in all of us,
how common are the bad ones? And where do we
pick them up? Oh? Man, it sounds to me like
Patrick is looking for nightmares.
Speaker 1 (06:50):
Oh it sounds to me like Patrick is giving me
my Christmas present early by allowing me to talk about parasites.
And so, you know, at the intro, I talked about
how in nineteen forty seven there was this estimate that
there's two point two billion parasitic infections and a population
of under two point two billion people. So some people
are infected by more than one parasite. And I wasn't
(07:11):
actually able to find a comparable estimate for now, And
I think partly that's because the way he grouped parasites
together is not really a biologically relevant category that people
care about anymore, and so I wasn't able to find
a comparable number. But I am going to go through
some of the main parasitic infections that have plagued humans
in our recent past, but we managed to get rid of,
(07:34):
and then some that are still a problem today in
the United States and in other parts of the world.
But I figured today we would start with a success story.
Speaker 3 (07:43):
That's good because I was afraid that the message of
this episode was going to be like, there's parasites everywhere,
all up in your eyeballs and in your earballs and
in your noseballs and everything.
Speaker 1 (07:53):
Well, you know, especially if you live in the United
States and you're lucky enough to be in an area
where there's really good sanitation, you probably are pretty safe.
But you know that's not necessarily true in other parts
of the world. We're very lucky here.
Speaker 3 (08:08):
All right, Well, let's dive in, because I want to
know by the end of this episode how likely am
I to have worms living inside me? Right now?
Speaker 1 (08:15):
Well, we're only talking about one worm. And I was
interested in figuring out what people know about this worm,
because at least in the United States, infections are very
uncommon these days, About fifteen cases of infection with this
parasite are recorded per year for a disease that once
infected one out of six Americans. So we've made a
lot of progress, and so I was wondering have people
(08:36):
heard about this before? So I asked our audience, what
is trick andilosis?
Speaker 3 (08:40):
Right? And if you would like to play on this
segment of the podcast in the future, please don't be
shy we'd love to have your voice. Write to us
to questions at Danielankelly dot org. So before you hear
these answers, think to yourself, do you know what trick
andilosis is?
Speaker 1 (08:55):
Also known as trick and osis?
Speaker 3 (08:57):
Uh no idea the osis at the end.
Speaker 5 (09:01):
It sounds like it could be some kind of disease
or medical conditions.
Speaker 2 (09:05):
I'm too excited for words. This isn't about cats and
uncertainty and quantum mechanics and things I don't understand. This
is a worm. It's a parasite. It grows in pork mainly.
I grew up in India and it was a real
risk that we'd get this, So we had pork that
was like leather. You could have put it on your
feet and worn it as a shoe.
Speaker 4 (09:27):
Disease associated with a parasitic infection of a round worm
from cysts from muscle from undercooked meat, pork and other
animals as well. I believed.
Speaker 5 (09:41):
By bacteria. Worms go drinkinglysis is an infection drinking alact
could be a gear or maybe a braasite. I'm not sure.
Trichinosis is a human disease caused by a pair of
worm in pork.
Speaker 6 (10:01):
I think tricknosis is a disease that one can contract
from eating undercooked meat. I don't know if it's a parasite.
If Kelly's involved, I assume that it must be.
Speaker 3 (10:13):
Though no idea. Sounds like a bacterium. Trichinosis sounds like
the disease that happens to my third chin, and I
don't know anything more about it.
Speaker 4 (10:23):
I have no idea what trickynosis is. However, taking a
stub in the dark, I'm going to say parasite, but
only because the email asking the question came from Kelly.
If the email asking the questions coming Daniel, I would
have took a stub in the dock and said a particle.
There we go.
Speaker 3 (10:40):
Tricenosis involves a trial by a tricycle and tragedy.
Speaker 1 (10:47):
So, Daniel, it is so clear to me that our
audience has us totally figured out it is about a
parasitic worm.
Speaker 3 (10:54):
And you know, just because the email doesn't come for
me doesn't mean it wasn't particles. I mean, I assume
these parasites are made to particles. They're not like fundamental
parasites in the universe or anything. These aren't string theory parasites.
Speaker 1 (11:04):
Are they not posts quantum gravity parasites, nothing like that.
These are actual parasites. And I am always so amused
by the wonderful answers you all give when you don't
know the answer, like probably it's goblins and that was great.
Speaker 3 (11:20):
All right, So give us the context. Take us back
in history. When did we first learn about this particular worm.
Speaker 1 (11:26):
Well, the first documented case where someone figured out that
this worm was causing an infection was from eighteen thirty five,
So we're in London at Saint Bartholomew's Hospital. Back then,
the way that a bunch of the medical students learned
about infections was that an autopsy or a surgery would
be happening in the middle of essentially what looks like
(11:47):
a theater. Like imagine you're sitting down to watch a play,
but instead you're watching an autopsy.
Speaker 3 (11:51):
The first five rows may be splashed, yes, yeah.
Speaker 1 (11:55):
And this was back before there was anesthesia, so like
amputations were oh through some turns my stomach, that about it.
But it was an autopsy and it was a man
who had died of tuberculosis. And the surgeons in the
middle of the operating theater, they had their scalpels, and
they were trying to like get through the body, and
the scalpels kept dulling, and they were feeling really frustrated.
And when they finally got inside, they got to the
(12:16):
diaphragm and one of the surgeons said, I knew it
a case of sandy diaphragm.
Speaker 3 (12:22):
Sandy diaphragm, sandy diaphragm.
Speaker 1 (12:25):
And so one of the guys who was in the audience,
his name was John Paget, He was a medical student,
and he said, what causes sandy diaphragm? And this is
the thing that was dulling their scalpels. And the surgeons
were like, we don't know. Let's go to life.
Speaker 3 (12:40):
Well, what was the general state of medical knowledge? Like
was the inside of the human body a total mystery?
And we mostly figured out like the circulatory system and
the digestive system and all that. What did we sort
of know about the workings of the human body almost
two hundred years ago?
Speaker 1 (12:53):
I think that if you went to a surgeon, it
was like a fifty to fifty chance the surgeon made
things worse. We'd a medical historian, so maybe the odds
were better or worse. I don't really know. We knew
a fair bit, you know, Like we knew that if
someone had a cancerous growth, you'd try to cut it
off real fast. But we didn't have anesthesia, so sometimes
you'd get an infection and you'd die from that. It
(13:15):
was a dicey time to be someone who needed the
help of a professional.
Speaker 3 (13:20):
And this is before germ theory, right, So we didn't
understand there could be microscopic organisms infecting or was this
after germ theory.
Speaker 1 (13:28):
Luayne Hook had been able to see his little animacules,
so we knew that there were like tiny little organisms
in the world. I don't think we had germ theory,
and Lister hadn't figured out ways to establish antiseptic technique.
That is all off the top of my head. And
maybe we should have like Lindsay Fitzharris, who's this amazing
(13:51):
historian of like surgeries and stuff on the show, to
give some background there.
Speaker 3 (13:56):
Because I thought that like middle of this century, we
still have folks like going from cadavers to delivering babies
and wondering like, hey, why are so many women dying
in childbirth? What a mystery? And maybe we should wash
our hands.
Speaker 1 (14:09):
Yeah, No, that is where we were yeah. Okay, we're
still before the germ theory. Okay, yeah, yeah, And I
think that you know, if they amputated someone's limb, they'd
kind of like wipe it off with the napkin maybe,
and then amputate the next person's limb. There were lots
of microbes being shared between people at this time.
Speaker 3 (14:24):
All right, But sandy diaphragm is not due to microbes, right,
It's due to actual visible worms.
Speaker 1 (14:29):
It's due to actual visible worms. They are not easy
to see. So what Paget did was he took a
sample and he used a hand lens and he squished
it between two glass slides, and he looked at it
with the hand lens, and he thought he saw something
kind of wormy, but he wanted to get a better
look at it, so he brought it over to the
British Museum of Natural History, and he actually knocked on
the door of the guy who came up with Brownie
(14:50):
and the idea behind Brownie in Motion. So he knocked
on Brown's door, and he had a microscope. He let
Paget use it, and Paget noted that there was actually
a worm there. Some of the worms were moving and
some were not, and the ones that were not had
been calcified by the human body and that's what was
causing the sandy diaphragm. So when these worms die, the
(15:12):
immune system responds by sort of like creating like a
calcified casket to like walllet off from everything else, and
over time that creates like hard structures, and that is
what the scalpels were dulling on. So he goes and
he tells a group of medical students about his finding,
but he doesn't take the important next step of publishing
and sharing his results more widely. The same cadaver, a
(15:36):
sample of it, got sent to this other guy named
Richard Owen, and we don't need to get into too
much detail here, but he also from the same cadaver,
ended up looking and seeing these worms. He wrote it up,
he gave a public lecture. He's the one who got
the credit. But this one cadaver produced two different people
who were the first to notice that actually there were
these little, tiny worms, and so it used to be
(15:58):
called traquina. I think what which is a word for
like tiny hair and spiralis is, you know, like the
spiral shape, and so these are hair shaped worms that
curl up in a spiral inside of cells like direphram cells.
But Trickina also was a genus of flies, and so
they went with Trickinella to avoid confusion. So hair like
spirally things.
Speaker 3 (16:21):
And take us back also scientifically, like if you find
worms in a body, at that point, do you have
to assume that somehow the people have eaten them or
they've invaded the body, or are we still in a
place where like we don't understand whether life can be
generated spontaneously.
Speaker 1 (16:37):
So we and Hook and Pasture I think they had
already done their experiments at this point where you know
that there's little things and you know that those little
things aren't generated spontaneously, because Pasture and I think some
other people as well had done those experiments where they
had made those flasks that had the like bendy mouth
parts so that the air couldn't sort of get in.
(16:59):
And whenever air can't get in and you had like
a nutrient broth, nothing would grow in it. But if
air could get in, you would get growth. And so
it's not arising spontaneously. You have to have something seating
the living things. I'm sure that people had seen parasitic
worms before but I don't think we had a very
good handle on life cycles.
Speaker 3 (17:17):
All right, What exactly was new and novel about this?
What did this tell us about parasites and humans and
all that kind of stuff.
Speaker 1 (17:25):
So I don't think that this is the first parasitic
disease that was ever discovered, but I think this is
a problem that was attributed to a parasitic disease at
this point. So like this person in particular had died
of tuberculosis. I think it was a while before we
realized that this was something that could kill people as
opposed to just something that's a pain in the rear
end when you're trying to run a scalpel through a
(17:46):
dead person's body. But even today, if you get infected
by too many of these all at once, you can die.
So let's talk a little bit more about what they
actually discovered when we get back from the break. Okay,
(18:14):
So what they had discovered was trick and ellis barrellis.
This is a nematode. So they've got like a hard cuticle.
They kind of look like earthworms, but without the segments
and the ones that we're talking about, the ones that
cause trick and e loosis they're very tiny, so they're
much smaller than normal earthworms. Do you feel like you've
got that image in your head.
Speaker 3 (18:33):
I'm imagining something that looks basically like a human hair
and it's curled up. Yeah, and if you zoom in
on it, it looks sort of like a worm.
Speaker 1 (18:40):
Yeah, it comes to points at either end, but yes,
kind of like a human hair, except points at the ends.
And so what happens is if you eat meat that's
infected by this parasite and that meat's not cooked through
all the way, the parasites burst out of the cells
that they've been living in. So as your body is
digesting the food, it also digests the cells they've been
living in and that releases them.
Speaker 3 (19:00):
So they've been living inside the cells. Like I'm eating pork.
Then these worms are inside the cells the pig, not
swimming around between the cells.
Speaker 1 (19:08):
Yeah, and this is not something that's super common for
wormy parasites to do, but this is something that this
particular species does. They live inside the cells, and they
can live inside the cells for like thirty years, like
incredible amounts of time.
Speaker 3 (19:20):
So they're smaller than like a pig cell.
Speaker 1 (19:23):
And they get into the pig cell, they expand the
size of that cell. Oh well, get there. I'm so
sorry about the next few years of your life, Daniel.
And so they burst out of the cells, they find mates,
they produce live smaller worms, and the smaller worms get
into your bloodstream or the circulation for your lymph, and
then they end up all over your body. But they
(19:45):
can only move in and live into skeletal muscle cells.
And so when they end up in like your heart
or your brain, they try burrowing into those cells and
then they're like, oh, this isn't home, and they borrow
back out again.
Speaker 3 (20:01):
Because we have two different kinds of muscle cells, right,
smooth and skeletal. Is that right?
Speaker 1 (20:05):
Three types cardiac, skeletal and smooth.
Speaker 3 (20:09):
Oh all right, cool? So why can they only live
in one particular kind of muscle? Is the shape of
the cell, the size of the cell, the kind of
food they get inside or.
Speaker 1 (20:17):
I don't think we know the answer to that. But
they do end up manipulating these cells. They are born
about a week after you eat the infected meat, and
they're going on this journey. And so about a week
after you eat the infected meat, this is when you're
at the highest risk of dying because if you ate
a lot of parasites in that meat, they're all having babies,
they're all releasing babies, and those babies are like maybe
(20:39):
if they end up in your brain, destroying a bunch
of brain cells or destroying a bunch of cardiac cells.
And at this point you're often given medication to reduce inflammation,
because that's a big part of what is causing trouble here,
the inflammation as a result of the parasites moving around,
And sometimes you're given anti parasite medication. But this is
the most dangerous phase of the process.
Speaker 3 (20:59):
And in order to be a risk of like dyeing,
you must need to have lots and lots of these parasites.
Can one worm or two worms generate like an avalanche
of these things? Or do you need to eat a
lot of the meat you have like a big initial population.
Speaker 1 (21:12):
Yeah, the more that you eat initially, the worst shape
you're going to be in. So if you just happen
to eat one or two cells that have the parasite,
you're probably gonna be fine.
Speaker 3 (21:21):
You're still going to have parasites inside you. You're just
not going to die. That's what you call it fine.
Speaker 1 (21:26):
I mean, for most of our revolutionary history, that would
have been lucky, just one or two parasites in you.
But yes, it won't be a dire situation, I guess.
But so when these parasites do find the cells, they're
looking for the skeletal muscles they burrow in and now
this is when they start manipulating the cell. So they
call the cell a neur cell. They like secrete some
(21:47):
stuff that gets rid of the parts of the cell
that they don't need. They start growing and expanding. The
cell starts getting bigger, and then around the cell, I
think it doesn't recruit the kind of vessels that bring
oxygenated blood because inside the cell you end up with
an anaerobic environment. I don't know why that's necessary, But
so they start bringing the kinds of cells that take
(22:08):
deoxygenated blood away. But in this way, the nurse cell
delivers nutrients and removes waste, and so the parasites are
able to manipulate the cells to become nice homes and
to do things like remove waste and feed them. So
we don't really understand how this happens, but it does.
And Dixon de Pomier wrote this book called Parasites People
(22:28):
in Plowshares, where he argues that if we could understand
how nurse cells work, we could maybe understand like better
ways of like delivering insulin and stuff like that. And
so he's really interested in trying to like physiologically understand
what's happening here. But it's a complicated system.
Speaker 3 (22:43):
So they really have taken over the cell and refashioned
it for their own use. It's no longer doing the
original thing you had that cell for. It's not basically
just like a homestead for these worms.
Speaker 1 (22:53):
Yep, it's kind of amazing. I think that they've managed to, like,
you know, evolve to do this.
Speaker 3 (22:57):
I think it's super amazing when they manipulate their environment
respond in a certain way to take advantage of it. Obviously,
you know this is just evolutionary, right, there's no like
intentional design here. They're not like engineers where they're thinking
about what to do. But they found this strategy. Why
haven't humans responded in an evolutionary sort of way to
create new defenses, Like, obviously this is bad if it
(23:18):
kills you, or even if it doesn't kill you, it
must be bad for you because it's sapping your energy.
Do humans have defenses against this or we just like
total suckers for these worms.
Speaker 1 (23:28):
Well, so some of the worms die and the ones
that die they get calcified. And I think probably some
of them are dying because of an appropriate immune response.
Speaker 3 (23:37):
I'm glad to here's something's happening in the inside to
push back.
Speaker 1 (23:39):
Yeah, yeah, we're doing something. But y know, so for
a lot of parasites, the deal is that they, through
this evolutionary arms race, have just found ways to evade
the immune system, to just make the immune system things
it's not even there. And then other times it's more
about like and I'm going to make this sound super anthropomorphic,
and it's not like a decision that the body's making,
like it's thinking about it like a person. But this
is a process overtionary time. But so these worms that
(24:02):
are living in the nurse cells, is it worse for
the body to deliver a tiny amount of energy to
these teeny tiny little worms or to kill the worms
and calcify it. And if it's in your diaphragm, you know,
so like that sandy diaphragm. Yeah, it's a problem for
the scalpel. But probably a diaphragm that's that hard, isn't
doing a very good job of like helping you breathe.
(24:23):
And so if you end up with all of these
calcified muscles, and when a parasite dies, it usually kicks
off an inflammatory response. And so I think over evolutionary time,
the trick isn't attack all the parasites that you have
with your maximum mobility, because when you initiate an immune response,
that often causes damage to the host as well. And
so I think it's a balancing act between what do
(24:44):
I just ignore and what do I have all out
war against.
Speaker 3 (24:48):
I don't know, Kelly, I think you're just a shill
for big parasite. I mean, you're telling me I should
happily live along with these things that have like squatting
in my cells. You're like, isn't it just best for
everybody if you you just give in and give up
some of your energy. Like, I don't know, I think
we're in all out war with these things.
Speaker 1 (25:06):
There are some unpleasant people in my life, and I
think my life is better for ignoring them than for
like trying to attack back. And you know, I don't
think it's that different with the worms and you know,
we should have a whole episode one day on this
old friends or hygiene hypothesis. Are you familiar with this idea?
Speaker 3 (25:21):
Yeah.
Speaker 1 (25:22):
The idea is basically that, like, we've had these organisms
in our body through enough evolutionary time that our immune
systems have come to sort of like expect them to
be there, and now they're sort of used as cues
for how our immune systems should work and how our
immune system identifies self from not self. These things don't
always go in the direction you'd think I wouldn't want
to have any worms in my body, but you know
(25:42):
it's also positible. My body is just like it's not
worth the effort you just ignore.
Speaker 3 (25:46):
Yeah, and Katrina is big on not classifying microbes, some
of them as good or bad because they all play
different roles and it's complicated, and you know, you might
imagine you don't want to be infected, but obviously lots
of microbes are essential for your life, the fermentation that
happens in your gut, all that kind of stuff. Is
it possible that parasites like these worms are playing some
(26:07):
positive role that we're benefiting from. I mean, you call
them a parasite, which implies that we're not getting anything.
There's no commensural reaction here. But are there any benefits
to having these worms live inside of us?
Speaker 1 (26:18):
I don't think there's any documented benefit from having Trickenellis
barrellus inside of you. There are some other parasites that
people have been experimenting with where when you infect people,
like their hay fever symptoms go away, or their crone's
disease symptoms become less severe, or their MS goes into
remission or whatever the right word is for that. But
(26:40):
those studies are super complicated. Sometimes you get good results,
sometimes you don't. It seems to depend on the parasite
genome or maybe the exact person's genome and the exact
kind of problem they have. And I think science is
like really working through digging through that right now, and
right now we're at a like what is happening phase,
But we should invite an expert on one day to
(27:01):
talk about that.
Speaker 3 (27:02):
I'm just trying to get mentally prepared because you know,
I've learned now the bacteria it can be good for you,
and even leeches can be good for you. So hey,
maybe in the future we'll all be intentionally injecting worms
into our children.
Speaker 1 (27:13):
There are a community of people who are intentionally infecting
themselves with parasites right now. I think most of them
are not doing that to their children, I hope. But
in my mind, the ideal thing isn't that we all
take like five hookworms for breakfast and call it a day,
but that we figure out what cues the parasites are
giving our immune system, and then we can like take
a probiotic pill or something that like replicates those cues
(27:36):
so we don't actually have to have the parasites there.
But I agree with Katrina that I think we are
at a point where dichotomizing things as good and bad,
we're realizing sometimes it's a little bit more complicated and
it depends on context.
Speaker 3 (27:47):
And I think the point you made is really interesting
that we can learn from them how to manipulate our
own bodies. Like if they have spent millions of years
evolving strategies to pull chemical levers inside the body, we
can take advantage of that, right. If we understand the
techniques that they have stumbled into, we can maybe use
them intentionally to understand the workings of our own system.
Speaker 1 (28:08):
Yeah. Yeah, sometimes the parasites that manipulate host behavior. We
sometimes refer to them as evolutionary neuroscientists. And there's you know,
like a whole group of people like me who write
our NSF grants about how we can understand host behavior
better by trying to figure out what parasites have quote
unquote learned through natural selection. All of this across all
these years.
Speaker 3 (28:26):
So these guys set up a home in these nurse cells,
make them work for them. How long do they hang out? Like,
do they live as long as the cells live? Do
they have like generations and generations of worms inside one cell?
Or does a single worm last a long time?
Speaker 1 (28:42):
So there's no reproduction happening at this stage. But worms
can live it looks like for twenty five plus years.
Speaker 3 (28:47):
Twenty five years. Oh yeah, gosh, so they can vote
and you know, buy alcohol and stuff like this.
Speaker 1 (28:53):
Yeah, absolutely, because that's what they're doing. But no, they
live for a really long time. And I mean they've
got like a nice setup. You know, food is being
delivered to them, their wastes are being removed, so yeah,
they can live for a really long time. But they're
not reproducing. They're just like biding their time until the
muscles that they live in get eaten by something else.
Speaker 3 (29:09):
And are they squirming around a lot? Because for some
reason that makes them a lot worse. Like if you're
just quietly hanging out inside my cell and stealing some food, okay,
but if you're like squirming around, then it's Oh, I
just can't tolerate that.
Speaker 1 (29:21):
You know, I would like to exercise every day. So
I guess I hope that they're like running laps and
their little nurse cells. But I think they're generally not
moving much. And if they are, you're not feeling it.
Speaker 3 (29:30):
See, you're pro parasite. There you are again like advising
the parasites how to live their best life inside people.
Speaker 1 (29:36):
Well, you know, we all need to stay healthy. So
you know, you might be asking yourself, if you want
to avoid being a track for parasites, how do you
do that?
Speaker 3 (29:46):
Yes, tell me.
Speaker 1 (29:47):
For a long time it was difficult. So most of
us get this parasite from pork, and so pigs get infected.
It's in the pigs muscles. And if you eat pork
that hasn't been cooked through enough, that's how you get infected.
And pork, you know, in the eighteen eighties, the United
States was like a world exporter of pork. It was
a huge industry for US, and it ended up being
(30:07):
a big problem for US because Europeans decided that because
we weren't checking for trick and ella, we weren't checking
for this parasite, that we were causing a bunch of
trick and alsis outbreaks in Europe. And so for a
while they stopped importing pork from US, and this was
a big problem for our industry. Some Americans went over
there and they were like, no, and they figured out that, like, no,
(30:30):
it's not necessarily our pork that's causing the problem. Like
maybe maybe sometimes it's American pork that's the problem, but
like it's not like all of our pork is wormy.
But you know, it was a good goal to try
to reduce the worminess of our meat. And so how
did we do that?
Speaker 3 (30:44):
But wait, hold on a second, why pork? Like do
these parasites prefer pig cells to cow cells for some reason?
Do cows have the kind of muscles that they can't
get inside? Why pork?
Speaker 1 (30:54):
Okay, so part of it has to do with the
animal's diet. So pigs eat everything like a thing of
getting pigs on our farm so that all of our
food waste goes into pigs. But then I couldn't turn
them into bacon because they'd be like friends. I'd probably
name them wilburm. So pigs eat everything, including other pigs.
Speaker 3 (31:11):
Pigs are cannibals, yep.
Speaker 1 (31:12):
Pigs are cannibals. Yep. I need to be excited about that.
So when a pig dies, another pig will eat its
infected muscles, and then they'll get infected. Oh, so part
of it has to do with diet. There were also
some like rodents, who would eat dead pigs, and then
other pigs would eat the rodents, and so for a while,
rodents were part of the transmission cycle here. Cows tend
(31:32):
to not eat meat, but like horses, can get infected.
And horses don't usually eat meat, but sometimes they will,
so like a lot of animals that we think of
as non meat eaters, will eat meat every once in
a while if you give it to them and they're
in the right mood. And so there have been cases
of horses getting infected.
Speaker 3 (31:50):
We even learned on the podcast recently that bees sometimes
eat meat, right.
Speaker 1 (31:54):
That's right, yes, yes, meat, honey, m m yeah, And
so I think the reason that cows often don't get
infected is because they're just not eating meat. So trick
Andella spiralis is one trick and Ella species. There are
other trick and Ella species that seem to specialize on
other animals. There's like in the United States, bears and
moose and wild boars, some of them can get infected
(32:17):
by trick and Ella spurrells. But there's also other trick
and Ella species that are more common in nature that
they can get infected with. But then we can get
infected by those if we don't cook the meat through.
And so there is some chance that I carry some
trick and Ella in me because I ate bear once
that I don't think was cooked through.
Speaker 3 (32:36):
All the way you ate a bear? What I had
to hear that story? When did you have a bear not.
Speaker 1 (32:41):
A whole bear? I was working with some folks in
the Wisconsin Department of Natural Resources and they were nice
enough to invite us to their annual social gathering and
a bunch of people brought stuff that they had hunted,
and there was barbecue bear. And so I mean, I've
eaten bear. I'm gonna assume they cooked it through all
(33:01):
the way. But I've also eaten smoked moose heart. Oh,
but it shouldn't be in the cardiac muscles, so that
should be fine because it's in skeleton muscles.
Speaker 3 (33:10):
Yeah, there you go, it's smoked moose heart.
Speaker 1 (33:12):
Knowing is half the battle.
Speaker 4 (33:13):
You know.
Speaker 1 (33:14):
The smoked moose heart was gross, Like when it got
pulled out of the bag, it still had like fat
on top of the heart. But it was like a
collaborator of mine who was from a part of the
world where this was. Anyway I pushed.
Speaker 3 (33:26):
Through, You're going to turn me into a vegetarian killing.
Speaker 1 (33:28):
Again, right back to your vegetarian root exactly.
Speaker 3 (33:32):
Here we go.
Speaker 1 (33:33):
So let's back up. Okay, so you know you can
get it from pork, but you don't get it from
pork in the United States much anymore. So what's changed.
So in the nineteen fifties, we made it so that
people were no longer allowed to feed their farmed pigs
uncooked garbage, which is such a gross phrase to hear.
Speaker 3 (33:52):
I think you have to cook your garbage if you're
going to feed it to pigs.
Speaker 1 (33:55):
Yeah, So, like you know, nowadays, factory farms don't feed
pigs anything you would just call garbage. I mean, I
guess maybe people would want to call it garbage, but
it's not actually garbage the way these animals were being
fed garbage before. But for a while the change was
just you had to cook it through, and if you
cook it through enough, then any of the effective stages
of the parasites are dead. And so that was a
stage of improvement.
Speaker 3 (34:15):
All right, So barbecued garbage is okay, or slow roasted
garbage as.
Speaker 1 (34:19):
Long as the internal temperature in the middle of the
garbage reaches one hundred and sixty five degrees fahrenheit, yes,
you're probably fine.
Speaker 3 (34:26):
Maybe a souvied then, because that's really good temperature control.
Souvid garbage that's where they serve at pig restaurants.
Speaker 1 (34:31):
Oh so disgusting. So like, up until nineteen eighty five,
we weren't really sure how pigs were mostly getting infected.
But you know, we've talked about how cannibalism and rats
contribute to infection. That was also like, sometimes if pigs
and wildlife were interacting, I think most often the pigs
were infecting the wildlife, but sometimes the wildlife could infect
the pigs. But once we sort of figured all of
(34:53):
this stuff out, we were able to say, like, Okay,
first of all, you have to make sure your pigs
aren't able to eat the other pigs if they die.
You have to make sure you don't have any rats
in with your pigs, which I'm sure is hard.
Speaker 3 (35:06):
Yeah, that sounds hard because rats are everywhere.
Speaker 1 (35:08):
Oh my gosh. Yes, we live on a farm. Rats
are everywhere. It's hard to keep them out, but you
need to make a good effort to do it.
Speaker 3 (35:14):
Well, let me ask you, how do you feel about
the rats? Because I have this policy no rats inside
the house, but outside the house. Like, hey, you guys
were here before us. What am I going to do
kill all the rats? That's impossible?
Speaker 1 (35:25):
Well, okay, so the rats that we had in our
chicken coop were an invasive species, so they didn't really
belong there. These were like the lab rats, Norwegian rats
that had gotten out, and rats like usually I agree,
but so that we have really stupid chickens, and like
the chickens would be eating at their feeder and the
rats would be like right next to them eating and
(35:45):
they just kind of look at them and be like hey, Frank,
and they wouldn't do anything. But so then the rats
were living in the rafters above and they were just
like defecating an incredible amount.
Speaker 3 (35:55):
They do that.
Speaker 1 (35:55):
They do that, and there are some diseases you can
get from rat feces and from mouth hauntavirus. Yeah, right, exactly.
And so if it's just like, yeah, I try to
never kill wildlife, because I agree you were here first.
But when it's like, well, if my daughter goes out
to bring the chickens food and she's gonna get haunt virus,
like we've crossed the line and we have to get
rid of the rats.
Speaker 3 (36:16):
Also, wait, you live in Virginia, which is not that
far from the NIH, right, and you're talking about rats
that have escaped from labs. Are you basically living the
rats of nim That was.
Speaker 1 (36:28):
A great movie. These rats, they are the species that
we use in the lab. I don't know that they
escaped from the lab. They could have just like come
off of ships or something.
Speaker 3 (36:37):
Keep telling yourself that science has made.
Speaker 1 (36:40):
Some mistakes, no doubt about it. I'll own up to that.
Speaker 3 (36:43):
Well, we had rats as pets once, and rats are wonderful,
wonderful pets. They're smart, they're affectionate, they're really cute. They
do poop everywhere though, Yeah, that is definitely a problem.
Speaker 1 (36:53):
I also had rats as pets when I was a kid,
and I thought about getting one again the other day
because I did. Used to love just having like a
little on my shoulder and they make this cute little noises. Yeah,
I like rats a lot.
Speaker 3 (37:04):
My daughter would bike around the neighborhood with a rat
in her hood of her hood, riding along with her.
It was super cute. Yeah, anyway, you're saying, if you
have pigs and rats, try to keep the pigs from
eating the rats.
Speaker 1 (37:15):
Yes, try to keep the pigs from eating the rats.
And so once we figured this stuff out, it became
clear what you needed to do to keep the pigs
from getting infected. And once you knew what you needed
to do, you could pass laws to make sure that
people are doing these things. And by putting in the
right sort of like procedures in place and then coming
up with some better ways to test meat to see
(37:36):
if it's working, we have managed to mostly eradicate this
parasite in pork from factory farm amazing, but there's still
some ways that you can get it, which we'll talk
about after the break.
Speaker 3 (37:50):
More nightmere fuel, don't worry.
Speaker 1 (37:52):
That's right. We were just talking about how pigs from
factory farms in the United States tend to not have
(38:14):
this parasite anymore. And actually in twenty twenty four there
was a study where they sampled three million pigs and
none of those pigs from factory farms had trichinella.
Speaker 3 (38:25):
Amazing.
Speaker 1 (38:26):
Wow, that is incredible. Like if you think that we
have gone from one in six people in New England
having this parasite infection, which can kill you sometimes, to
testing three million pigs and none of them have it,
that's an incredible decline.
Speaker 3 (38:41):
That means all those people who were infected when they died,
nobody ate them and then absorbed the infection, right, including
the pigs.
Speaker 1 (38:48):
That's right. Yes, I should have known you were going
to go there. My bad, But yes, that means that
there's not a lot of human cannibalism going on. Good news.
Speaker 3 (38:56):
And of course I'm going to ask if pigs can
get from eating other pigs, that means humans could get
it from eating other humans, right yep, yeah, okay, one
more reason not to eat your children.
Speaker 1 (39:05):
Yes, yeah, well, you know, if they're young enough, maybe
they haven't been exposed and they move it on.
Speaker 3 (39:11):
When their meat is still so tender.
Speaker 1 (39:13):
Oh God, why do we do this?
Speaker 2 (39:16):
All? Right?
Speaker 1 (39:17):
So, now there's about fifteen confirmed cases in the United
States a year, which is an incredible drop, and there's
about ten thousand cases recorded throughout the world per year.
And I think a lot of those cases are in
places like China where they eat a lot of pork,
but maybe they don't have the same sort of procedures
in place to make sure that the pigs aren't eating
(39:38):
each other or being exposed to rats. And so there
are other places in the world that you can go
where if you eat pork you could get infected.
Speaker 3 (39:46):
So how's it happening in the US if there were
no examples in all of those pigs where people get
and they're just getting it from the wild again, or
they're eating weird smoked moose hearts or something.
Speaker 1 (39:57):
So I think a lot of people do get it
from animal that they hunt. So you can get it
from bears, you can get it from moods, you can
get it from wild boar. And also, you know, if
people have pigs in their backyard, they are not necessarily
following all of the rules that like the USDA mandates.
So it could be that their pigs are encountering wild
animals that they're eating or then eating each other, and
(40:20):
so you could get it from like backyard pigs. The
good news is if you cook your meat where the
inside reaches I think it's one hundred and forty five
degrees fahrenheit, then the parasite dies. The bad news is
if you freeze the meat, even for something like two months,
that doesn't necessarily kill Trick.
Speaker 3 (40:40):
And Ella w Yeah, can survive freezing.
Speaker 1 (40:43):
It's amazing. Yeah, So like there have been cases where
meat has been frozen and two months later it's come
out of the freezer and when it thaws, those worms
start moving around again. This is mostly the wild strains
or the wild species. Maybe it's not too surprising because
like bears can hibernate, they get really cold. But still,
the fact that they can freeze, that's amazing because bears
aren't freezing through when they're hibernating.
Speaker 3 (41:04):
Yeah, And I thought that most cells when they freeze,
they burst because water expands as it freezes. So how
do these guys survive it?
Speaker 1 (41:12):
I mean, I'm guessing some of them do have nurse
cells that burst and they die. But most of the
food that we plan on eating we freeze quickly because
when those cells burst, that food doesn't taste as good.
And so like you want to freeze your food quickly
so the cells don't burst, because that's a better way
to eat a hamburger or a bear steak. So I think,
(41:32):
you know, the parasites are benefiting from that and they
can survive. And then also if you prepare jerky out
of bear meat, that processes preparing the jerky doesn't always
kill the parasites. These parasites, you think about it, like
they transmit when the animal that they die in gets
eaten by something else, and that doesn't always happen immediately.
So they need to be able to like survive the
(41:53):
death of the animal for a while and persist in
the environment to increase the probability that they get eaten
by something. Yes, yeah, so most of the cases in
the United States come from wild animals that have been
killed and then not cooked through all the way. In
other parts of the world, you can get it from
pork because they don't have the like public health procedures
that we have in place here in the United States.
(42:15):
But I'm excited about this system because it's a pretty
clear example where doing the basic work to understand the
life cycle of the parasite and then putting that information
in the hands of people who can like set up
procedures was able to save I think many many lives, Yeah,
and also just be less creepy, Like maybe not a
lot of people were going to die, but it's really
(42:35):
nice to know that we don't have like parasites running
laps in our diaphragms in the United States.
Speaker 3 (42:43):
So you're a parasitologist, you know, the cutting edge of
parasite science. We've mostly told the historical story today, but like,
what are people working on right now? If you go
to trichinosis conference, what are the presentations about, what are
the questions that people are asking.
Speaker 1 (42:59):
Yeah, so one of the main topics here is trying
to figure out when an outbreak happens. So there are
still outbreaks. I was listening to someone's talk the other
day and it was somewhere in Scandinavia there was an
outbreak on farms and it showed up in a couple
different farms, and so they were collecting samples of the
parasite and then they were genotyping it. So they were
(43:20):
getting like the whole genome of the parasite, and they
were trying to use that information to find out did
the parasite jump from a wild animal, you know, where
the pig's able to go out in the field one
day and they ate a wild animal and that's how
they got infected. But by figuring out what species or strain,
then they can try to figure out like where the
procedure for keeping this parasite out of our food system,
(43:43):
like where that broke down. And so they're using genetic
information to sort of do the tracing stuff here. They're
also still trying to figure out how this nurse cell works,
you know, how does it manage to manipulate the human
body into essentially like waiting on it hand and foot
without killing it. And you know, also like wildlife ecologists
are probably interested in what trick and ella is doing
(44:04):
to like wild bear populations and stuff like that. So
I think those are the main topics we're dealing with
right now.
Speaker 3 (44:10):
So this all sounds surprisingly positive. You're saying this is
a success story. Is this typical killing or is the
wider world of parasites a darker world?
Speaker 1 (44:19):
Well, the wider world of parasites can be pretty dark.
So this was a nice case where we figured out
how the parasite was transmitted. It was pretty clear what
we needed to do, and it wasn't that hard to
implement the changes. But there's other parasites where we know
what it would take to eradicate the infection. But like
for example, bringing the appropriate sanitation measures to the people
(44:41):
who need it has just proven to be something that
we can't seem to do yet. And so the next
time we talk about this wormy world of ours, we're
gonna be talking about nematodes. And today we talked about
anematode too, but we're gonna be talking about nematodes that
you can get because they burrow through your skin when
you're walking in soil that's carrying these effective stages.
Speaker 3 (44:59):
Oh no, you don't even need to make bad eating decisions.
You can just be going.
Speaker 1 (45:03):
For a walk, or you can be gardening. They're able
to just sort of burrow through your skin. So we
will talk about soil transmitted helmets which have been stubborn
and hard to eradicate. The next time we visit this
warming world.
Speaker 3 (45:16):
There's always more nightmare fuel waiting for you in Biology.
Speaker 1 (45:20):
And Kelly's got it ready for you.
Speaker 3 (45:23):
Thanks everyone, tune in next time.
Speaker 1 (45:32):
Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We
would love to hear from you, We really would.
Speaker 3 (45:39):
We want to know what questions you have about this
Extraordinary Universe.
Speaker 1 (45:44):
We want to know your thoughts on recent shows, suggestions
for future shows. If you contact us, we will get
back to you.
Speaker 3 (45:50):
We really mean it. We answer every message. Email us
at Questions at danieland Kelly.
Speaker 1 (45:56):
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Speaker 3 (46:06):
O't be hye write to us
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Daniel Whiteson
Kelly Weinersmith
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