Speaker 1: I contracted toxoplasmosis in my first trimester. I will never
Speaker 1: know how the doctor did not educate me or test
Speaker 1: me for it. I was not given the opportunity to
Speaker 1: prevent the devastation this disease would have on my baby.
Speaker 1: It had a lot of time to go unchecked and
Speaker 1: do a lot of damage. My daughter, Dana, was born
Speaker 1: six weeks premature with severe damage to her brain and
Speaker 1: her eyes. She is now twenty two years old. She
Speaker 1: has very little cortex to her brain, She has cerebral palsy,
Speaker 1: She is blind. She has severe developmental delays. Dana requires
Speaker 1: our full care. She cannot sit unassisted, walk, talk, feed herself,
Speaker 1: dress herself, or toilet herself. My husband and I still
Speaker 1: change her diapers day and night. The toll on her
Speaker 1: body has been tremendous. She has had ten surgeries, two
Speaker 1: of which were so traumatic we almost lost her. She
Speaker 1: has a tube that drains excess fluid from her brain.
Speaker 1: She has a metal rod in her back to help
Speaker 1: straighten severe curvature of her spine so her organs and
Speaker 1: lungs can continue to function. She has a pump surgically
Speaker 1: inserted to give her constant doses of a medicine to
Speaker 1: help her relax her muscles from further contorting her body, which,
Speaker 1: by the way, is only minimally successful. One hip was reconstructed,
Speaker 1: the other is currently dislocated. I hate what toxoplasmosis has
Speaker 1: done to my daughter. It has stolen the dreams I
Speaker 1: once had for her and from me. Our whole family
Speaker 1: has experienced emotional and financial strain. Yet through this all
Speaker 1: we have loved this young lady. She is remarkably determined
Speaker 1: to endure. She laughs. She enjoys being a part of
Speaker 1: an active family life. Dana has a younger sister, Rebecca,
Speaker 1: who is in college right now. She is one of
Speaker 1: the smartest, wittiest, kindest people I know. Life has been
Speaker 1: difficult for her too. Watching Rebecca, I can't help but
Speaker 1: think of what Dana's life would have been like if
Speaker 1: her infection were caught early on. What would her future
Speaker 1: have held? Oh my god. Yeah. That was an account
Speaker 1: by Janet Morel, who testified before the Illinois State Senate
Speaker 1: in support of Senate Bill three six sixty seven, which
Speaker 1: was the proposed Prenatal and Neonatal Congenital Toxic Plasmosis Prevention
Speaker 1: and Treatment Act Act. This bill would provide that healthcare
Speaker 1: professionals shall provide counseling for toxic plasmosis and testing for
Speaker 1: toxoplasma gandhiaye when providing care to a pregnant woman during
Speaker 1: her pregnancy. So that was part of her testimony.
Speaker 2: Wow, h my god.
Speaker 1: Yeah, it's a really it's really sad. It's very rough.
Speaker 3: Rough.
Speaker 1: Well, I'm Aaron.
Speaker 2: Welsh and I'm Aaron Olman Updyke and.
Speaker 1: This is this podcast will Kill You. This week we
Speaker 1: are covering toxoplasma gandhi I. Yeah, we are, which has
Speaker 1: been a pretty heavily requested episode. I think has it, Yeah,
Speaker 1: I think it has Yeah, And it's going to be
Speaker 1: a heavy one. It's going to be an interesting one.
Speaker 1: It's going to be all the things that you've come
Speaker 1: to expect from this podcast. Yeah, speaking of things to expect.
Speaker 2: It's quarantine ey time.
Speaker 3: It is erin.
Speaker 1: What are we drinking this week?
Speaker 3: This week we're drinking what the cat dragged in? What
Speaker 3: is in what the cat dragged in? Well, of course
Speaker 3: it's not a dead mouse, but that would be appropriate
Speaker 3: as well. It's vodka, some sparkling wine, a little Creme
Speaker 3: de violette and lemon juice.
Speaker 1: Yeah, it's tasty. It's the big crucial thing. Crucial is
Speaker 1: that you rim the glass with pop rocks.
Speaker 2: Of course, because they look just like kitty litter.
Speaker 1: There you go.
Speaker 2: We'll post the.
Speaker 3: Full recipe for this quarantini as well as our non
Speaker 3: alcoholic plusy Burta on our website This podcast will Kill
Speaker 3: You dot Com and all of our social media channels,
Speaker 3: so follow us there for the full recipe.
Speaker 1: And I think I want to cover a couple pieces
Speaker 1: of business which I just don't think that we have
Speaker 1: done it all pertains to live shows or live ish shows.
Speaker 3: They weren't live ish like we were there.
Speaker 1: Yeah, that's true. It wasn't like a full live show.
Speaker 1: We're not going on tour or anything like that. But
Speaker 1: we were lucky enough to go to both the University
Speaker 1: of Florida thanks to Nick Kaiser, and also to the
Speaker 1: University of Michigan thanks to Laura Haynes. Yeah, we met
Speaker 1: so many amazing people during both trips. It was really,
Speaker 1: really fun.
Speaker 3: We had the most fun at both of those trips.
Speaker 3: It was super excellent. So thank you for inviting us,
Speaker 3: and thanks to everyone who came and watched.
Speaker 2: It was so fun.
Speaker 1: It was great. And also I recently, Aaron Welsh, I
Speaker 1: was recently a guest on a live show of a
Speaker 1: podcast called The Road to Now. Yeah. Yeah, it was
Speaker 1: super fun. So this is a really great history podcast
Speaker 1: and they came to Chicago recently and I got to
Speaker 1: be a guest along with Obama's White House photographer Pete Susa.
Speaker 1: So it's so great, mind blowing, so cool, surreal. But anyway,
Speaker 1: you can hear that episode of the live show on
Speaker 1: the Road to Now, So just look them up wherever
Speaker 1: you get your podcasts. And we're also going to post
Speaker 1: a link if we haven't already by the time this
Speaker 1: comes out on our social media.
Speaker 2: Yes, any other business.
Speaker 3: We have a new merch including water bottle.
Speaker 1: Yes, they're gorgeous.
Speaker 3: They're very very cool, and they're the nice like insulated
Speaker 3: kind metal water bottles and fancy smelling soap new smells.
Speaker 1: Of soap new smells.
Speaker 2: So check that out.
Speaker 3: Just go to our website This podcast will kill You
Speaker 3: dot com and click on merch to find that.
Speaker 1: Any other business, Nope, let's just dive right in. Okay, Aaron,
Speaker 1: tell me about the biology of toxic plasmosis. I just
Speaker 1: can't wait to do that we'll take a little break,
Speaker 1: all right. Toxo Plasma gandhii toxic plasmosis. I've been looking
Speaker 1: for to doing this episode ever since I was a
Speaker 1: guest on.
Speaker 2: The per Cast. Oh yeah, yep.
Speaker 3: We talked a little bit about TOSO on that episode.
Speaker 3: If you haven't heard it, it's really fun. But I
Speaker 3: didn't do any research on TOCSO before I went on
Speaker 3: the Percast, so I felt really silly because I didn't
Speaker 3: know the answers to a lot of questions. So I'm
Speaker 3: excited to finally, you know, have done some research on this, like,
Speaker 3: actually know what I'm talking about a little bit. It's
Speaker 3: still not an expert, okay, so polished amateur exactly.
Speaker 2: That's a good description for like my life, I think.
Speaker 3: Okay, So, Toxoplasma gandhii is a protozoan parasite, so like
Speaker 3: malaria or giardiam.
Speaker 2: Oh you did a great job, thank you?
Speaker 1: Is that condescending it up just a little?
Speaker 2: So?
Speaker 3: This is a single celled organism that's not a bacteria
Speaker 3: or a virus. Okay, yeph And this, when I learned
Speaker 3: this fact, blew my mind so hard that even though
Speaker 3: this is technically EPI I'm gonna say.
Speaker 2: This up top.
Speaker 3: Toxo infects up to one third of the entire world's population.
Speaker 3: Uh huh, one third of the globe of humans.
Speaker 1: Uh huh. I know, I know.
Speaker 3: That is just mind wild, it's so wild, Oh my gracious. Okay, So,
Speaker 3: because this is a parasite, we have to talk about
Speaker 3: its life cycle because it's more complicated than some other organisms. Okay, So,
Speaker 3: the main host of Toxoplasma gandhi is of course cats.
Speaker 3: Cats are the definitive host of Toxoplasma GANDHII, and when
Speaker 3: they get infected with this parasite, they poop out thousands
Speaker 3: and thousands of something called oocysts. That's the life stage
Speaker 3: that the cats poop out.
Speaker 2: Okay, yep.
Speaker 3: And after one to five days in the environment the
Speaker 3: environment being cat poop, so cat box or your sandbox
Speaker 3: where your kids are playing, or your backyard or pretty
Speaker 3: much anywhere in the environment.
Speaker 2: These oocysts spoulate.
Speaker 3: So then they kind of become infectious at that point.
Speaker 3: Once they spoulate, they can persist alive and infectious in
Speaker 3: the environment for years, really years, well at least a year, okay,
Speaker 3: for year, yeah, for months and year, depending on the environment,
Speaker 3: so they can get into the soil, they can get
Speaker 3: into the water, they can get on your vegetables, et cetera.
Speaker 1: What's the ideal environment.
Speaker 3: The ideal environment would be kind of subtropical, so not
Speaker 3: too hot, not too cold, although they can survive freezing,
Speaker 3: you know, no big deal. Yeah, but they do. They
Speaker 3: like we'll see in the episection burdens tend to be
Speaker 3: highest in warmer climates because they do persist better in
Speaker 3: warmer climates. Okay, So they get all up in the
Speaker 3: environment and then they're picked up by small animals, birds, mice, rats,
Speaker 3: generally things that cats.
Speaker 2: Might like to feed on.
Speaker 3: Once they get into these small animals, they are now
Speaker 3: called taki zo whites. So that's the life stage that
Speaker 3: infects small animals.
Speaker 1: Okay, I want to make some sort of joke about
Speaker 1: taki but I tried.
Speaker 2: I tried too. There's no good one.
Speaker 3: So inside of a mouse, generally, the way that a
Speaker 3: small animal gets infected is by coming into contact with
Speaker 3: their mouth. So they eat some soil, they drink some water,
Speaker 3: they eat a piece of lettuce, whatever it is that
Speaker 3: has these tachisoites on them, and they get infected. Then
Speaker 3: these tachizoites burst out of the intestine of these mice
Speaker 3: or these rats, and they infect tons of different cells.
Speaker 3: So this is a parasite that is actually it has
Speaker 3: to be intracellular, so it invades cells inside of everything
Speaker 3: that it infects. And these this life stage replicates asexually,
Speaker 3: so it just divides, and it does so really really
Speaker 3: rapidly and really profusely. So in the mouse, you've now
Speaker 3: got this parasite dividing and replicating and swarming through the tissues.
Speaker 3: Then they'll find their way into two specific tissues that
Speaker 3: they like to invade, muscle and brain.
Speaker 1: Why do they like those two types of tissues?
Speaker 2: Well, let's talk about it.
Speaker 1: I like, how now you like you know me so
Speaker 1: well that you know what I'm going to ask pretty soon.
Speaker 3: Most of the time doesn't mean I always know the answers, though,
Speaker 3: but here we can talk about it. So they find
Speaker 3: their way into neural tissue and muscle tissue. Once they're there,
Speaker 3: I'm going to first say what they do once they're there,
Speaker 3: Then we'll talk about why these are the tissues they invade.
Speaker 3: Once they're there, they insist, so they actually transform into
Speaker 3: yet another life stage.
Speaker 2: The Brady zoite.
Speaker 3: The brady zoite forms a cyst inside of the muscle
Speaker 3: tissue or the brain tissue. The cyst is surrounded by
Speaker 3: the animal's tissue muscle or brain, but then full of
Speaker 3: hundreds of these brady zoites. These continue to divide, but
Speaker 3: they do so much more slowly. Okay, okay, But then
Speaker 3: to complete the life side, these brady zo whites have
Speaker 3: to find their.
Speaker 2: Way into a cat.
Speaker 3: Right, so the cat is going to eat the mouse
Speaker 3: or the rat or the bird. What part of the
Speaker 3: mouse or the rat or the bird. Do cats definitely
Speaker 3: eat muscle tissue?
Speaker 1: That makes sense?
Speaker 3: Okay, So that's why they insist in the muscle tissue.
Speaker 3: Why might they insist in the brain?
Speaker 1: Oh? I think I know the answer to this.
Speaker 2: Oh yeah.
Speaker 3: It turns out that Toxoplasmagondhia is a parasite that can
Speaker 3: exhibit behavior modification. So that means that it can actually
Speaker 3: change the behavior of the animals that it infects, which
Speaker 3: is it's really cool.
Speaker 2: It is very cool.
Speaker 1: It's kind of like blows the lid off of the
Speaker 1: whole parasite host dynamic in a way that is so
Speaker 1: sci fi. But also I think it's just a tip
Speaker 1: of the iceberg. Okay, I'm jumping the gun to it.
Speaker 3: It is so sci fi, but it's something that's actually
Speaker 3: not that uncommon in parasites that are transmitted what we
Speaker 3: call trophic lely, so from one what we call trophic
Speaker 3: level to another. So if you think of like the
Speaker 3: pyramid of life with like carnivores on the top, carnivores
Speaker 3: are gonna eat herbivores, and herbivores are gonna eat lettuce.
Speaker 1: Or whatever, right, primary produce, secondary producers, primary producers.
Speaker 3: Exactly right, right, yea lettuce, and so in in parasites
Speaker 3: that are transmitted like through the food chain like that,
Speaker 3: it's actually not that uncommon for parasites to manipulate the
Speaker 3: behavior of that intermediate host like the mouse, so that
Speaker 3: they're more likely to be eaten by the definitive host,
Speaker 3: i e.
Speaker 2: The cat.
Speaker 3: In the case of mice and rats that get infected,
Speaker 3: what they do is not only do they seek out
Speaker 3: more rapidly novel environments, and they're less fearful and more
Speaker 3: likely to be in open areas where normally mice and
Speaker 3: rats are kind of like they stay hidden because they
Speaker 3: don't want to be eaten, for example, So infected mice
Speaker 3: and rats will seek out novel areas and explore more readidly.
Speaker 3: And they have done studies that show that they're not
Speaker 3: only less afraid of cat smells like cat urine, they're
Speaker 3: actually attracted to smells like cat urine.
Speaker 1: Yeah, isn't that Oh, it's really Yeah, it's it's almost unbelievable, Like.
Speaker 3: When you think about that the parasite has evolved to
Speaker 3: be transmitted this way, and this is how, and so
Speaker 3: here's the reason why this happens, or a reason why
Speaker 3: this happens, is that only in cats can Toxoplasma GANDHII
Speaker 3: complete its life cycle because once a cat eats those
Speaker 3: brady zoites that are in the brain or muscle tissue
Speaker 3: inside the cat, they actually undergo sexual replication. And only
Speaker 3: in cats do does Toxoplasma gandhi actually sexually reproduce, and
Speaker 3: then it produces those oocytes that the cat poops out,
Speaker 3: and then the cycle can start all over again.
Speaker 1: Right, the parasite has to find its way back to
Speaker 1: the cat.
Speaker 3: Yes, Yeah, so there's a huge amount of incentive on
Speaker 3: the part of the parasite to make sure that they
Speaker 3: make it into the cat.
Speaker 1: Yeah, it's a. It's gorgeous, it's beautiful.
Speaker 3: It is that being said, what about humans? Yeah, so
Speaker 3: that's the life cycle like in the wild or in whatever.
Speaker 3: That's how Toxoplasma gandhi evolved to exist. So what are humans?
Speaker 3: Are we the cat or are we the mouse? The
Speaker 3: mouse or the mouse. So it turns out that we
Speaker 3: can get infected with almost any life stage of the parasite.
Speaker 3: So we can get infected directly from those spoulated oociss
Speaker 3: that cats poop out. So that means if we get
Speaker 3: in contact with cat poop directly, or with contaminated soil
Speaker 3: or contaminated water, or maybe contaminated vegetables that haven't been
Speaker 3: washed or cooked, then we can get infected with that
Speaker 3: first stage, those tachizoites. Okay, those are the stage that's
Speaker 3: gonna invade tissues locally, that's gonna replicate really rapidly. But
Speaker 3: we can also get infected with those tissue cyst stages
Speaker 3: that would normally want to be eaten by a cat,
Speaker 3: the brady zoites inside tissue cysts, gotcha, So if you
Speaker 3: eat contaminated meat, for example, then you can get infected
Speaker 3: with that life stage. However, since we're not cats, the
Speaker 3: parasite can't complete its life cycle inside of humans.
Speaker 1: We're a dead end host, just like in lime disease.
Speaker 2: Just like in lime disease.
Speaker 1: We're not contributing to the parasite life cycle. And like
Speaker 1: the prevalence.
Speaker 3: Unless a cat ad us which does happen, could happen, Yeah, could.
Speaker 1: Happen, and it definitely happened prehistorically for sure. Apparently cats
Speaker 1: are like a major, major predator of humans, which may
Speaker 1: are like of the ancestors of humans, which makes total senating.
Speaker 3: Yeah yeah, okay, So in humans, then the main way
Speaker 3: that this parasite causes disease is in two main ways.
Speaker 3: First by invading cells and tissues, so it can cause
Speaker 3: direct damage in those tissues that it invades, and by
Speaker 3: forming tissue cysts in really important places in our body
Speaker 3: where you shouldn't have cysts full of parasites. Cool cool, cool,
Speaker 3: but yeah, okay, got it all right, So let's talk
Speaker 3: about the symptoms that we see in toxicplasma infection. The
Speaker 3: good news is that the vast majority of people who
Speaker 3: get infected, something like eighty to ninety percent of people
Speaker 3: will be entirely asymptomatic.
Speaker 2: That's it.
Speaker 1: I for some reason, I expected it to be higher asymptomatic.
Speaker 1: You said eighty to ninety are asymptomatic.
Speaker 2: Yeah, yeah, okay, yeah.
Speaker 3: But okay, So even of those ten percent of people
Speaker 3: who maybe do show symptoms, the vast majority of those
Speaker 3: people will have a very non specific, self limited illness,
Speaker 3: so they'll feel a little sick, kind of cruddy. And
Speaker 3: the most classic sign of an initial toxoplasmosis infection is lymphatinopathy.
Speaker 3: So your lymph nodes get swollen, Okay, and that's pretty
Speaker 3: much it. Those lymph nodes usually aren't very tender, and
Speaker 3: they can stay enlarged for like a month or so
Speaker 3: the vast majority of the time, So that's even if
Speaker 3: you have symptoms, the vast majority of time, that'll be
Speaker 3: kind of your only symptoms, So not that big of
Speaker 3: a deal in that case. However, in some cases, a
Speaker 3: primary infection can invade specific organs and then cause illness
Speaker 3: in those organs. So if those tachisoites swim through and find,
Speaker 3: say your heart tissue, your heart is a giant muscle,
Speaker 3: so it wouldn't be surprising for them to try and
Speaker 3: find and insist in your heart muscle, then then you
Speaker 3: could get something called myocarditis, which just means inflammation of
Speaker 3: your heart muscle. If those tachisoites invade your lungs, you
Speaker 3: might get anumanitis. If they invade your liver, a hepatitis. Okay,
Speaker 3: all of these are theoretically possible, they have happened, but
Speaker 3: they don't happen very commonly.
Speaker 1: Is there anything so, I know, like immunocompromise is one
Speaker 1: big aspect of where this might happen more than others.
Speaker 1: But is there anything else that is like makes you
Speaker 1: more susceptible to organ invasion?
Speaker 3: That's a really good question. So the only other thing
Speaker 3: besides immunal compromise, which I'll talk in more detail about
Speaker 3: in just a second, is potentially strain differences.
Speaker 2: So there are a number of.
Speaker 3: Different genotypes and strains of Toxopasma GANDHII, and there is
Speaker 3: some difference in virulence between those strains. How big of
Speaker 3: a role that plays is not entirely clear. Okay, but
Speaker 3: so yeah, for most people who are healthy, they will
Speaker 3: never have any signs of infection. But in people who
Speaker 3: are immuno compromised, especially in people living with HIV, toxopasma
Speaker 3: can be an extremely serious infection. The most common form
Speaker 3: of toxoplasma infection of toxoplasmosis in people living with HIV
Speaker 3: or people who are otherwise immunocompromised is encephalitis. So that's
Speaker 3: inflammation of the brain. So here's the thing about toxoplasma.
Speaker 3: If you get infected, even if you're asymptomatic, it doesn't
Speaker 3: necessarily mean that you don't have cysts inside of you
Speaker 3: right now. But most of the time, your immune system
Speaker 3: is going to be able to keep those cysts kind
Speaker 3: of in check. They're never going to do anything, they're
Speaker 3: never going to cause harm. But if you become immunocompromised,
Speaker 3: those cysts can reactivate essentially, and then you can get
Speaker 3: the encephalitis later on.
Speaker 1: Okay, yeah, that's bad.
Speaker 3: So you can, like if you have an immuno compromise,
Speaker 3: you could get sick with toxoposmosis from a primary infection
Speaker 3: like this is the first time you got infected, or
Speaker 3: it could be that you've had cysts in your tissues
Speaker 3: and now they're re activating because your immune system is low.
Speaker 3: It's really really serious. It's considered an AIDS defining illness.
Speaker 3: Toxoplasma encephalitis got it in a person living with HIV.
Speaker 3: And then, of course, the other way that you can
Speaker 3: get infected besides eating contaminated meat, which by the way,
Speaker 3: is the most common way that people get infected.
Speaker 1: But I do have to point out there was a
Speaker 1: study that looked at the rate or the prevalence of
Speaker 1: toxoplasmosis in people who were vegetarians and people who were
Speaker 1: not vegetarians and found equal rates.
Speaker 2: Fascinating.
Speaker 1: So, yeah, so it's very very clear that there are
Speaker 1: many different roots for exposure. Absolutely much much beyond cats
Speaker 1: is what much beyond owning a cat I should say is.
Speaker 3: Yeah, owning a cat is generally not even alone, owning
Speaker 3: a single cat is not even considered a risk factor.
Speaker 1: Then we'll talk more about the ecology of that and
Speaker 1: why that is.
Speaker 3: Yeah, But the other way that you can become infected
Speaker 3: is congenital toxoplasmosis, which is what we heard about in
Speaker 3: the first hand account.
Speaker 2: It is horrible.
Speaker 3: So toxoplasma can cross the placenta and then infect the fetus.
Speaker 3: It turns out that this is most common if a
Speaker 3: pregnant person gets infected for the first time while they're pregnant.
Speaker 3: And what's interesting is that the risk of infection of
Speaker 3: the fetus actually increases with gestational age, So the later
Speaker 3: in a pregnancy that a person gets infected, the more
Speaker 3: likely it is that the fetus will be infected, but
Speaker 3: the severity of that infection is opposite, so it decreases.
Speaker 3: So the earlier a fetus gets infected, the more severe
Speaker 3: the outcomes.
Speaker 1: But the less likely they are to become infected.
Speaker 3: Exactly right, so overall, without any treatment for a primary infection,
Speaker 3: So a pregnant person who gets infected while they're pregnant,
Speaker 3: the risk of congenital syphalis is between twenty to fifty percent,
Speaker 3: depending on when during their pregnancy they get infected, what
Speaker 3: strain they're infected with, likely, and how much they're exposed
Speaker 3: to probably as well. Severe infections can result in fetal loss,
Speaker 3: so it can result in stillbirth or miscarriage. But other
Speaker 3: characteristic findings are things called choreo retinitis, which is inflammation
Speaker 3: of the retina and the choroid, which is basically like
Speaker 3: your blood vessels in your brain in your eye, sorry,
Speaker 3: not your brain, which can lead to blindness, hydrocephalus, which
Speaker 3: is the build up of fluid.
Speaker 2: In the brain.
Speaker 3: And intracranial calcification, which is calcium deposits essentially inside of
Speaker 3: your brain and then seizures in a baby. So yeah,
Speaker 3: it's really bad congenital toxoplasma.
Speaker 1: Is it routine anywhere to screen?
Speaker 3: It's not routine in most places to screen unless there
Speaker 3: is a risk for infection, so it's not universal.
Speaker 1: And is it something where you could determine whether it's
Speaker 1: an active infection or a like something that you have
Speaker 1: been infected with the sister just there, Yes.
Speaker 3: You can so in general, and I will say that
Speaker 3: pregnancy is a form of immunal compromise, so it is
Speaker 3: possible to have reactivation of cysts, but it's much less
Speaker 3: likely that that will result in congenital toxoplasmosis.
Speaker 1: Okay, so it's.
Speaker 3: Really that primary infection, like if you get infected for
Speaker 3: the first time while you're pregnant, that's when it's the
Speaker 3: highest risk for.
Speaker 1: So it's like the tachizoites exactly right.
Speaker 3: Yeah, but also even if you like ate pork that infected,
Speaker 3: so then you're getting infected with brady zoites, but it's
Speaker 3: just not from within your body reactivating, which is primary infection. Yeah,
Speaker 3: but yeah, we usually use zeral prevalence, so looking for antibodies,
Speaker 3: but you can tell based on the type of antibody
Speaker 3: and the amounts of antibody whether or not it's a
Speaker 3: primary infection or you were infected, say ten years ago
Speaker 3: or something like that. Okay, And the good news is
Speaker 3: that there is treatment. The treatment is mostly aimed at
Speaker 3: that tachyzoite stage, that rapidly dividing stage, so it doesn't
Speaker 3: affect the tissue cysts directly mm hm. So that's kind
Speaker 3: of the catch twenty two is that we can treat it,
Speaker 3: but we can't really affect those tissue cysts.
Speaker 1: But if there's an act like let's say for pregnant people,
Speaker 1: if there's an active infection, that's really the thing that
Speaker 1: needs to be targeted anyway it appears.
Speaker 3: Yeah, and so for pregnant people, there's two different ways
Speaker 3: that we can treat it, depending on if we think
Speaker 3: the feeted is already infected or if we're trying to
Speaker 3: prevent the fetus from getting infected. So one you can
Speaker 3: treat just to prevent those tachizoites from kind of crossing
Speaker 3: the placenta and infecting the fetus, or if you think
Speaker 3: the fetus is already infected, you can give different drugs
Speaker 3: that actually help treat it within the fetus itself, and
Speaker 3: all of those are affecting the.
Speaker 2: Tachisoite stage as well.
Speaker 3: Okay, so yeah, I mean that's basically the biology of toxoplasmosis.
Speaker 1: Oh okay, Yeah, it's a bad one. I mean I
Speaker 1: knew that it was bad, but yeah.
Speaker 3: Yeah, So Aaron, how did we get here? Where did
Speaker 3: this thing come from? And why does everyone get infected?
Speaker 3: One third of all people?
Speaker 1: I'll tell you after this quick break. So the actual
Speaker 1: written history of toxoplasma gandhi is just over one hundred
Speaker 1: years old.
Speaker 2: That's it.
Speaker 1: Yeah, like the written history of there's this disease that
Speaker 1: does this, there's this parasite that does this.
Speaker 2: Wow.
Speaker 1: Yeah, So this is going to be a really short section.
Speaker 1: Just kidding. It means, yeah, it's me. It'll never be
Speaker 1: a very short section. It just means I'm going to
Speaker 1: talk more about evolutionary history and other things that I'm
Speaker 1: just going to sprinkle throughout. Fabulous Okay, but let's get
Speaker 1: to the written history part of it first. In nineteen
Speaker 1: oh eight, the parasite was described for the first time.
Speaker 1: There were these two researchers working at the Pasture Institute
Speaker 1: in Tunis. They were studying leshmaniasis, which is a disease
Speaker 1: caused by a different protosome parasite. They're trying to figure
Speaker 1: out what the reservoir host was and learn more about leshmanias,
Speaker 1: the lashmania transmission cycle, all of these things. And for
Speaker 1: their research they were using an animal called a common gundy,
Speaker 1: which I had no idea. I looked it up and
Speaker 1: it's like kind of weirdly cute. It's definitely not like
Speaker 1: that cute. I mean, that's horrible. We'll post a picture, yes,
Speaker 1: of course. And so this is it's about the size
Speaker 1: of a guinea pig maybe, and it's a type of
Speaker 1: rodent that's native to northern Africa. Oh, it's super good
Speaker 1: at living in rocky deserts okay. And so they were
Speaker 1: looking at this the tissues of a Gundhi gandhi for
Speaker 1: parasites leshmania, and they found a partizan that they thought
Speaker 1: was lash mania, but they looked a little bit closer
Speaker 1: and realized based on morphology, this is a completely different parasite. Awesome,
Speaker 1: So they named it Toxoplasma gandhi eye toso for the
Speaker 1: Latin word for arc plasma for former life gandhi I
Speaker 1: was a misspelling of the host the common Yeah, no way,
Speaker 1: gundi is how you spell the animal g o n
Speaker 1: d ii is how you spell the specific epithet of
Speaker 1: Toxoplasma gadie.
Speaker 2: That is so funny.
Speaker 3: Yeah, I love it when things get named for silly
Speaker 3: reasons like that.
Speaker 1: I mean, it's one letter, but it's just kind of like,
Speaker 1: I never thought about gandhi I. I mean I just
Speaker 1: thought probably it was gonna be someone's name.
Speaker 2: But yeah, wow, that is so interesting.
Speaker 1: Anyway. Okay, So at the same time that these two researchers,
Speaker 1: who by the way, their names were Charles Nicole and
Speaker 1: Louis Manso. At the same time that these researchers were
Speaker 1: finding and describing Toxoplasma GANDHII in the common gundi, on
Speaker 1: the opposite side of the world, in Brazil, another researcher,
Speaker 1: same year, another researcher named Alfonso Splendor, was doing the
Speaker 1: same exact thing, like he found Talksopoasma gandhi eye, but
Speaker 1: he found it in a rabbit what instead. Same time.
Speaker 1: So yeah, keep that fact in your head.
Speaker 2: Ooh, is there going to be drama?
Speaker 1: No, I mean not really. I will say that by
Speaker 1: and large Nicole and Manseaux are the two that get
Speaker 1: the credit for the discovery, and in large part because
Speaker 1: their finding was written in English and Alfonso splendor was
Speaker 1: His was written in Portuguese and not translated into English
Speaker 1: until two thousand and nine. And so this goes into
Speaker 1: the whole English as a dominant as the only scientific
Speaker 1: language and blah blah blah all the issues surrounding that.
Speaker 1: So wow, it's kind of interesting. He also didn't name
Speaker 1: the parasite. He just said I found this parasite, okay,
Speaker 1: so that could have something to do with it too.
Speaker 1: But another thirty years would pass before people realized that
Speaker 1: this parasite could be harmful to humans. Who was In
Speaker 1: nineteen thirty eight there was a three day old newborn
Speaker 1: I was born at Baby's Hospital in New York City.
Speaker 1: She started having seizures and the doctors looked her all
Speaker 1: over and all they could see that was out of
Speaker 1: the ordinary were these lesions in her eyes. Sadly, a
Speaker 1: month later she died, and so during the autopsy, doctors
Speaker 1: saw the same lesions all over her brain, and they
Speaker 1: wrote a case study up about this and this case
Speaker 1: study would end up being probably the first recognized case
Speaker 1: of congenital human toxoplasmosis because they found the parasites in
Speaker 1: her brain and then they injected it into animal models
Speaker 1: and then they developed encephalitis and so yeow, and so
Speaker 1: at this point, Toxoplasma gandhia is a recognized pathogen, but
Speaker 1: there were still many mysteries surrounding the parasite, including the
Speaker 1: extent to which people were infected, like the prevalence, how
Speaker 1: they became infected, and many characteristics of the parasite itself,
Speaker 1: like its life cycle and its hosts. So researchers had
Speaker 1: detected the parasite and many different mammal species, but they
Speaker 1: were unsure of which animal was the definitive host. So
Speaker 1: which yeah, And at first they suspected it had something
Speaker 1: to do with eating undercooked meat, which, as you said,
Speaker 1: it definitely does. And so in the nineteen sixties they
Speaker 1: these group of scientists designed an experiment in which they
Speaker 1: fed essentially raw lamb, like just barely cooked lamb chops
Speaker 1: to people with tuberculosis living at a sanatorium to see
Speaker 1: if they could transmit Toxicpasma gandhia.
Speaker 3: I'm sorry, yeah, it is every episode this season is
Speaker 3: going to have some horrible experiment that we've done on humans.
Speaker 1: Yeah. Well, in the experiment was successful, of course, because
Speaker 1: people they didn't kill people, but these people did become infected.
Speaker 1: But that didn't quite answer the question of what the
Speaker 1: definitive host was. It was just like, can you get
Speaker 1: it from uncooked meat. So a few years after this experiment,
Speaker 1: a parasitologist decided kind of on a whim to check
Speaker 1: out whether his cats had the parasite bingo. They did,
Speaker 1: and it didn't take long for other labs to confirm
Speaker 1: these findings. And then this is like in the early
Speaker 1: nineteen seventies, and the backlash was there was like a
Speaker 1: strong backlash against cats. Apparently, according to one of the
Speaker 1: articles I read, there was like a lot of people
Speaker 1: and I don't know where exactly or how many killed
Speaker 1: cats out of fear thinking these cats are killing my children,
Speaker 1: these cats are killing you know, through this parasite. But
Speaker 1: I think for the most part, that was not the
Speaker 1: common response. I think it did happen, but I don't
Speaker 1: think it was the common response because cat ownership has
Speaker 1: only continued to increase since that study was released. So
Speaker 1: after finding that felines are the definitive host for toxo.
Speaker 1: A lot more of the pieces began to fall into place,
Speaker 1: so the complex life cycle of the parasite was figured out,
Speaker 1: and people started to get an idea of how it
Speaker 1: causes these behavioral changes in rodents that influence the parasite's transmission.
Speaker 1: So cool, it's so cool. And it's these early studies
Speaker 1: on the influence on the behavioral influence of rodents that
Speaker 1: really opened up this huge field of research about behavioral
Speaker 1: manipulation of parasites and what that might mean for humans
Speaker 1: and our micros. So I'll get to that in a bit.
Speaker 1: But that's basically the written history of toxo.
Speaker 2: Wow, so short.
Speaker 1: It didn't cause any massive pandemics or overtly changed the
Speaker 1: course of history in some dramatic fashion, and it isn't
Speaker 1: even old enough to have any like bizarre cures associated
Speaker 1: with it. It just basically consists of a series of
Speaker 1: scientific developments and findings. But there is more to talk
Speaker 1: so than that.
Speaker 3: Yeah, like where did it come from?
Speaker 1: Exactly? So remember how the parasite was discovered simultaneously at
Speaker 1: two different points on opposite sides of the world. Yeah,
Speaker 1: so there's a certain amount of coincidence that goes into that,
Speaker 1: but really what it tells us is just how incredibly
Speaker 1: widespread this parasite already was.
Speaker 3: Yeah, like that wasn't new at that time.
Speaker 1: That wasn't new. So the question is how did it
Speaker 1: get to be like that? And the answer is domestic cats.
Speaker 1: That truly is the answer. So I mean, yeah, let's
Speaker 1: go back in time. Let's go back to around eleven
Speaker 1: thousand years ago. So it's around then when we see
Speaker 1: the very first evidence of agricultural societies, so people actually settling,
Speaker 1: keeping livestock, growing grains and plants at home, and we
Speaker 1: see this happen in different places all around the world
Speaker 1: over the next several thousand years, So in the Fertile
Speaker 1: Crescent is where it began, then in China, then Mexico,
Speaker 1: in Western Africa, and so on. So around like eleven
Speaker 1: thousand years to go to four thousand years ago is
Speaker 1: when like the biggest you know, movement or shifts started
Speaker 1: to happen. And I've talked on this podcast before about
Speaker 1: how the formation of agricultural societies and farming, how that
Speaker 1: would have impacted disease transmission and what types of diseases
Speaker 1: were transmitted and what they would look like. So you know,
Speaker 1: just a refresher. Larger human settlements means more transmission between humans,
Speaker 1: So you get these crowd diseases like tuberculosis and influenza,
Speaker 1: and then you also get zonotic diseases transmitted between humans
Speaker 1: and their livestock or humans and domestic animals. Yeah, and
Speaker 1: the human animal contact increases not just because of people
Speaker 1: choosing to own cattle or whatever other livestock, but also
Speaker 1: because of keeping large stores of grain and other food.
Speaker 1: And then you get other little animals finding you.
Speaker 2: Like mice and rats, et cetera.
Speaker 1: Exactly. For example, how mouse. So there's archaeological evidence of
Speaker 1: the increase of the house mouse as human settlement increased,
Speaker 1: human agricultural settlement increases. So, twelve thousand years ago, the
Speaker 1: proportion of house mice bones found among small mammals near
Speaker 1: hunter gatherer communities was about five percent. But within a
Speaker 1: thousand years, which is like a long time but also
Speaker 1: a very short time, that number jumped up to eighty percent.
Speaker 3: So like, of all the animals that they found near,
Speaker 3: like eighty percent of them were house mouse.
Speaker 2: House Yeah, house mouses way to go wild.
Speaker 3: Yeah, that's a huge change in one thousand years.
Speaker 1: That's a mauge change. Yeah, so it's probably a good thing,
Speaker 1: or at least no surprise that cats were domesticated in
Speaker 1: the Fertile Crescent around the same time that agricultural societies
Speaker 1: began to there eleven thousand ish years ago, because.
Speaker 2: There's so many mice for them to eat.
Speaker 1: Yeah, it's probably not coincidental. Yeah no, But anyway, so
Speaker 1: there was a little cat named the near Eastern wild cat, who,
Speaker 1: even like the wild populations today, seemed to be very
Speaker 1: bold and not very aggressive towards humans. Are fearful, which
Speaker 1: is kind of interesting and makes sense. So these these
Speaker 1: types of cats came up to human dwellings and they
Speaker 1: made themselves at home, and probably in a way that's
Speaker 1: familiar to a lot of cat owners today.
Speaker 3: It's like, Hi, I'm here, now, I will live here.
Speaker 1: And so this caused a major shift in the dominant
Speaker 1: transmission pattern of Toxoplasma gandia. The sylvatic cycle, which is
Speaker 1: the natural cycle in the forests basically or in the
Speaker 1: wild wildcats, is exactly this is the one that still
Speaker 1: seems to be quite active in many places today. So
Speaker 1: this involves the wild felids and wild rodents, while the
Speaker 1: domestic cycle is the one that we are more familiar
Speaker 1: with and it's the one that has led to the
Speaker 1: huge prevalence of toxo around the world today. This is
Speaker 1: one that involves our housecats and house mice, and scientists
Speaker 1: have looked at the genetic diversity of toxo around the
Speaker 1: world and have found that in urban areas where the
Speaker 1: domestic cycle dominates, there's less diversity because there's more mixing
Speaker 1: of the parasite populations, and that's in contrast with the
Speaker 1: higher diversity seen in places where the sylvatic cycle is
Speaker 1: more common, such as the forests of Central and South America.
Speaker 1: But overall, the domestic cycle is the more common one,
Speaker 1: and the simple answer for that is housecats. So felines
Speaker 1: are the only animals that can serve as a definitive host,
Speaker 1: as you said, and wild felines have never really been
Speaker 1: at high enough population densities around the world to be
Speaker 1: able to result in the widespread and extremely high prevalence
Speaker 1: of toxo in humans. In humans, yes, in humans, yeah,
Speaker 1: but also in places where wild cats do not occur,
Speaker 1: we still see a ton of toso yeah in wildlife.
Speaker 3: Right, Yeah, I'm not surprised about that.
Speaker 1: And that is largely due to house cats as well.
Speaker 1: Why were cats domesticated in the first.
Speaker 2: Place to eat them mice?
Speaker 1: So that's probably part of it. So I read this
Speaker 1: book that's called The Lion in Your Living Room and
Speaker 1: it talks all about like it's all about the history
Speaker 1: of the cat. It's very fun and she is a
Speaker 1: huge lover of cats, and she's like, you know, it
Speaker 1: just doesn't really make a lot of sense. Like, dogs
Speaker 1: have tons of different roles, they have tons of jobs
Speaker 1: they can do. They're protective, they can work their useful.
Speaker 1: Cats you know, they can kill rodents, but for the
Speaker 1: most part, cats soaken dogs. Yeah, and dogs are actually
Speaker 1: more effective at actually lowering populations of rodents because because
Speaker 1: there can be task oriented, whereas cats aren't as task oriented.
Speaker 1: So they've shown like studies that cats don't often actually
Speaker 1: effectively reduce rodent populations unless food, other food is extremely scarce.
Speaker 2: Interesting because they'll.
Speaker 1: Go for the low hanging fruit. That just makes more sense.
Speaker 2: Lazy kitties.
Speaker 1: This is like, this is famously captured in a video
Speaker 1: of cats scavenging for trash right next to rats, because
Speaker 1: they're like, I don't want to waste my energy killing
Speaker 1: and eating a rat when I can just eat trash.
Speaker 1: I mean, it makes sense you can blame them, and
Speaker 1: certainly now they do little to affect urban rodent populations,
Speaker 1: right so she did, though. So the author of this book, though,
Speaker 1: did started a file apparently called uses for cats when
Speaker 1: she was researching this book. And I just want to
Speaker 1: list a few of these because they crack me up.
Speaker 2: Please.
Speaker 1: So, first of all, there was to encourage rain, people
Speaker 1: in Indonesia would parade cats around their fields.
Speaker 2: Parade cats. I love it.
Speaker 1: I wonder if parading cats is easier than hurtings that.
Speaker 2: I mean, it's probably equivalent.
Speaker 1: People use cat skin for musical instruments a lot. Oh.
Speaker 1: Apparently people in China used to use the cats dilating
Speaker 1: pupils to estimate the time of day, and they were
Speaker 1: also a critical part of many types of European tortures.
Speaker 2: Ooh wow, So.
Speaker 1: I'm quoting directly from her book. Medieval murderers were sometimes
Speaker 1: burned in a sack with twelve cats to maximize suffering,
Speaker 1: and during a punishment called cat hauling, a cat was
Speaker 1: dragged by its tail down the length of an offender's body.
Speaker 3: Oh.
Speaker 2: My god. Yeah, I feel so bad for the cats.
Speaker 1: I know. Okay, So then there's some more modern things.
Speaker 1: So cat hair has been used in DNA evidence for
Speaker 1: murder trials, okay, which is pretty cool. Yeah. So anyway,
Speaker 1: those were a few of the things on the uses
Speaker 1: for cats list. But I mean, regardless of of their
Speaker 1: questionable skills as rodent controllers or any of these other powers,
Speaker 1: humans kept them around. And that's maybe putting it mildly.
Speaker 1: There's archaeological evidence of the love that humans have for cats.
Speaker 1: There's a ninety five hundred year old gray for a
Speaker 1: kitten on the island of Cyprus. Baby m h. There's
Speaker 1: of course ancient Egyptian artwork, yeah, showing house cats. Worship
Speaker 1: of cats didn't.
Speaker 3: Weren't cats to ward off evil spirits and stuff? They're
Speaker 3: like protectors of they were.
Speaker 1: And then on the flip side of that, things weren't
Speaker 1: always so good between cats and humans. So I talked
Speaker 1: a little bit about it during the plague, but also
Speaker 1: cats in general in a lot of during sometimes in
Speaker 1: a lot of places were thought to be demons or
Speaker 1: agents of Satan. And some historians think that this might
Speaker 1: be due to the fact that allergies to cats are
Speaker 1: fairly high. So like if a cat jumps on you
Speaker 1: and goes around your face and stuff, and then you
Speaker 1: all of a sudden your throat itches and you can't breathe,
Speaker 1: I mean, I would probably think, yes, this cat is
Speaker 1: like an agent of Satan. Anyway, wherever humans went, they
Speaker 1: brought cats with them, maybe as mouse or rat killers,
Speaker 1: or maybe just as a good luck charm. And cats,
Speaker 1: of course, were especially valued on ships, and sometimes sailors
Speaker 1: would refuse to get on a ship if it was
Speaker 1: missing its resident cat. But when humans and cats traveled
Speaker 1: the globe together, there was this other hitchhiker that tagged
Speaker 1: along Toxoplasma GANDHII. And the proof of how far cats
Speaker 1: have traveled is in the global distribution of toxo. Toxoplasma
Speaker 1: gandhia is now found all over the globe, even above
Speaker 1: the Arctic Circle. Whoa, yeah, and in there it's not
Speaker 1: its way into beluga whales and other Arctic dwellers, and
Speaker 1: it's like, OK, quite a problem. Yeah, And it's not
Speaker 1: just that where you find cats, you can find toxo.
Speaker 1: Thanks to water, Toxo can travel incredibly far and over
Speaker 1: the past one hundred years or even fifty years, cats
Speaker 1: have grown incredibly in popularity. People have moved into apartments
Speaker 1: in cities, cat litter was invented, and globally now there
Speaker 1: are around six hundred million domestic cats.
Speaker 3: That's not as many as I expected.
Speaker 1: Well, there are around anywhere from six hundred million to
Speaker 1: one billion cats worldwide. Okay, okay, And these aren't just pets.
Speaker 1: These are also feral cats, right right. And every day
Speaker 1: in the US more cats are born than there are
Speaker 1: lions in the wild.
Speaker 2: Whoa, Yeah, that is a shocking statistic.
Speaker 1: Yeah, and these cats aren't always pets. In Australia, for
Speaker 1: every one pet cat that has a home, there are
Speaker 1: six feral ones.
Speaker 2: That's bad.
Speaker 1: It's really really, really really bad.
Speaker 2: Yeah.
Speaker 1: And in the US only about sixty percent of the
Speaker 1: American pet cat population are kept indoors.
Speaker 2: Ooh, that's bad.
Speaker 1: Yes, that's really bad.
Speaker 3: We touched on this in the Kittrid episode, but I
Speaker 3: assume we're going to talk a bit more about how
Speaker 3: important it is to keep cats indoors.
Speaker 1: Yeah, so it's not I mean, it's not just that
Speaker 1: cats have single handedly wiped out entire species, many different species,
Speaker 1: but even Researchers have shown that even just their presence
Speaker 1: alone causes many problems, such as increased stress, making it
Speaker 1: difficult for some prese species to breed or parent properly.
Speaker 1: And they also spread disease feline leukemia, toxoplasmosis. And for
Speaker 1: the most part, these problems can be greatly diminished or
Speaker 1: completely fixed by keeping cats indoors. Cats have a huge
Speaker 1: cascading effect on the ecosystem. And then when you throw
Speaker 1: in talcso it's a pretty big conservation and public health
Speaker 1: problem outdoor cats. And this is not easy to talk about,
Speaker 1: no at all, because people love their cats, and they
Speaker 1: love cats in general, and they can feel defensive about this.
Speaker 1: And by and large, if you have a cat and
Speaker 1: keep it indoors, you're not part of the problem. Your
Speaker 1: cat's not part of the problem. Strays and feral cats
Speaker 1: are much more problematic, and finding a solution that works
Speaker 1: has not been easy. Yeah, And in this book, the
Speaker 1: line in the Living Room, she goes into this in
Speaker 1: a lot more detail. But there's this. You know, a
Speaker 1: lot of cities practice TNR, which is trap now to
Speaker 1: release programs, and people who are opposed to that point
Speaker 1: out that these cats are still outside, they're still releasing
Speaker 1: toso and they're still killing birds and endangered reptiles and mammals.
Speaker 3: It's interesting because I hadn't I mean, I knew how
Speaker 3: big of a problem cats were for wildlife and things,
Speaker 3: and trap neudle release for cats that, like you know,
Speaker 3: are not going to get a home if you try
Speaker 3: and adopt them out.
Speaker 2: Because they're they're feral cats.
Speaker 3: Like they're not going to tolerate or or no one
Speaker 3: would want to adopt them. It's like, oh yeah, trap
Speaker 3: neudle release, at least they're not going to be making
Speaker 3: more cats. But then when you think about when I
Speaker 3: started reading about toxo and just how much of an
Speaker 3: impact a single cat can have, like, oh man, it's
Speaker 3: it's rough.
Speaker 1: It's really rough. And you know, trap noodle release is
Speaker 1: meant to reduce the population of feral cats. It does
Speaker 1: not work because you would have to like if if
Speaker 1: your goal was simply to reduce population of feral and
Speaker 1: stray cats, trap noodle release doesn't work, Like there are
Speaker 1: just it's too effortful for the number of cats that
Speaker 1: you actually can capture.
Speaker 3: There's too many cats out there that aren't being captured.
Speaker 1: Yes, so but you know, euthanasia doesn't work either. Estimates
Speaker 1: suggest that if you that only if ninety seven percent
Speaker 1: of all feral cats in an area are euthanized, will
Speaker 1: population numbers actually go down permanently. WHOA, cats are very
Speaker 1: effective at the breeding like rabbits. I guess wow. And
Speaker 1: so this debate continues to go on over which practice
Speaker 1: is better or which practice is more humane. But the
Speaker 1: conversation is starting to shift a little bit because people
Speaker 1: are realizing maybe it's not this versus this cats. We
Speaker 1: just have to accept that cats are part of the environment.
Speaker 1: So what do we do about it? That's maybe the
Speaker 1: more pressing issue, And that's not something that I'm going
Speaker 1: to attempt to answer. I just simply kind of wanted
Speaker 1: to bring this up because I think it's a really
Speaker 1: important bit of information about the problem of outdoor cats,
Speaker 1: and I think it's an interesting example of how conservation,
Speaker 1: public health, and animal rights can all be at odds
Speaker 1: with one another. Yeah, there's no easy answer. There's no
Speaker 1: easy solution here.
Speaker 3: Well, at least you can keep your own cat indoors.
Speaker 2: That's an easy solution.
Speaker 1: Yes, yeah, Okay, So you talked about some of the
Speaker 1: negative effects of toxow in humans, but toxo also can
Speaker 1: really devastate other animals, sometimes leading to or often leading
Speaker 1: to fatal infections. So this is the case, for example,
Speaker 1: with kangaroos. Kangaroos, Oh yeah, it's a big problem with kangaroos.
Speaker 1: It's also the case for sea otters, which I know
Speaker 1: is your favorite animal.
Speaker 3: I know, it's toxoin. Seaotters is so sad.
Speaker 1: It's so sad. And the fatal outcome in sea otters
Speaker 1: isn't necessarily just the direct effects of the parasite, but
Speaker 1: also the behavior alteration. So we know that toxic can
Speaker 1: affect the behavior of rodents infected with the parasite, and
Speaker 1: we've hinted at the subtle behavioral effects on humans. But
Speaker 1: it turns out that sea otters that are infected with
Speaker 1: toxo are three times more likely than their uninfected counterparts
Speaker 1: to be killed by a great white shark.
Speaker 2: WHOA.
Speaker 3: That is really fascinating because I was also reading that
Speaker 3: it's probably an underestimate how many otters die from toxo too,
Speaker 3: just because we only see the ones that wash up
Speaker 3: on shore, and not all of them obviously wash up
Speaker 3: on shore, and things.
Speaker 1: And the prevalence is like something like thirty six to
Speaker 1: forty something percent some populations. Yeah, which brings me to
Speaker 1: the possible effects of toxo on humans.
Speaker 2: Yeah, let's talk about it.
Speaker 1: Oh, toxo on humans is very interesting and sort of
Speaker 1: it's both a budding field and controversial. Yes, there have
Speaker 1: been many different studies that that have tried to associate
Speaker 1: toxoplasmosis infection with increased risk of car accidents, suicidal tendencies,
Speaker 1: just overall attitude of personality changes, and the results are like,
Speaker 1: there are some compelling results, but a lot of them
Speaker 1: seem a bit difficult to disentangle, like not everything has
Speaker 1: been controlled, and it's like a very it just hinting
Speaker 1: that there might be something going on there, not enough
Speaker 1: to I think say this is conclusively showing an effect.
Speaker 2: Definitely, don't have any solid right, But.
Speaker 1: The big one that has made the rounds is the
Speaker 1: association with schizophrenia. So basically, what proponents of this hypothesis
Speaker 1: believe or suggest that infection with toxoplasmosis leads to an
Speaker 1: increased risk of being diagnosed with schizophrenia. So let's go
Speaker 1: through some of the evidence and support of this one
Speaker 1: thing that a lot of people say, or that a
Speaker 1: lot of people point to, is that there don't seem
Speaker 1: to be descriptions of schizophrenia prior to the eighteen hundreds,
Speaker 1: and that's sort of when cat ownership really came into fashion.
Speaker 1: There's also the seasonality of schizophrenia, so people diagnosed with
Speaker 1: schizophrenia tend to be born in winter and early spring,
Speaker 1: which means that during the time their mom was pregnant,
Speaker 1: an outdoor cat might be spending more time indoors. But
Speaker 1: I also don't know if they looked at people from
Speaker 1: both hemispheres, yeah, if they controlled for that, and then
Speaker 1: whether it's like latitude alone, yeah, okay. Another piece of
Speaker 1: compelling evidence is that people with toxo and this is
Speaker 1: sort of like the bottom line evidence. People with toxo
Speaker 1: are three times more likely than uninfected people to be
Speaker 1: diagnosed with schizophrenia.
Speaker 2: Okay, But at the.
Speaker 1: Same time, the vast, vast majority of people with toxoplasmosis
Speaker 1: have not been diagnosed with schizophrenia, and there are people
Speaker 1: who have schizophrenia who have been diagnosed with schizophrenia and
Speaker 1: do not have toxo, so so so then they suggest
Speaker 1: maybe it's more of a predisposition or susceptibility thing. Yeah,
Speaker 1: and also compellingly, the some antipsychotic medicines that are used
Speaker 1: for people who have been diagnosed with schizophrenia do seem
Speaker 1: to be effective in stopping the progress of at least
Speaker 1: one stage of the parasite.
Speaker 3: I think that that is very very interesting, yes, but
Speaker 3: does not mean that toxo causes no.
Speaker 1: Yeah, let's look at the other side of the evidence,
Speaker 1: because this has gotten a lot of popular science press,
Speaker 1: and I think it just is like weighing the evidence
Speaker 1: is important. Yes, Okay, So there are huge geographic differences
Speaker 1: in toxoplasmosis prevalence, and some countries have prevalence rates of
Speaker 1: ninety percent and other are others are much lower, like
Speaker 1: ten percent, twenty percent, which is still really high. But anyway,
Speaker 1: but the corresponding rates of skins it's to ania diagnoses
Speaker 1: don't match with these.
Speaker 2: Okay.
Speaker 1: So the place is where you find the most toxo.
Speaker 1: You don't necessarily find higher rates of schizophrenia diagnoses, and
Speaker 1: even looking within a country, you don't see a drop
Speaker 1: in schizophrenia diagnoses following a drop in toxo due to
Speaker 1: increased food hygiene standards or something. And the other thing
Speaker 1: is that these are all correlation studies. Yeah, so we
Speaker 1: don't know what came first? Was it toxo or schizophrenia?
Speaker 1: Could it be that someone who has been diagnosed with
Speaker 1: schizophrenia is more likely to get toxo than someone who
Speaker 1: is not. Like, you know, these are correlation studies, and
Speaker 1: so some researchers have criticized these tenetive links between toxo
Speaker 1: and schizophrenia as building false hope. Once the public, though,
Speaker 1: got wind of the possibility that infection with this parasite
Speaker 1: could alter human behavior, the headlines have gotten just a
Speaker 1: bit more bizarre, and some of them pretty cringe or
Speaker 1: eye rolling. Yeah, there's an opinion piece suggested that the
Speaker 1: Brazilian soccer team was so good because high rates of
Speaker 1: infection led to increased risk taking and aggression.
Speaker 2: Oh my gracious.
Speaker 1: Yeah so or maybe toxo did shape civilization itself. Who knows,
Speaker 1: you know. I wanted to talk a little bit about
Speaker 1: these studies, but mostly to say grain of salt this
Speaker 1: so I think I'm ready to get back onto some
Speaker 1: solid ground with real numbers. Can we please, Aaron, tell
Speaker 1: me where we stand with toxic today?
Speaker 2: Oh?
Speaker 1: You want me to do that, I do.
Speaker 3: Okay, we'll take one more quick break, all right, So
Speaker 3: toxoplasmosis today, Like we said already, but it bears repeating.
Speaker 3: The estimated prevalence in humans of Toxoplasma GANDHII infection is
Speaker 3: between twenty five and thirty percent of all humans.
Speaker 1: Twenty five and thirty percent of.
Speaker 3: All of humanity. But like you mentioned, this isn't equitably
Speaker 3: divided in some places, where, for example, consumption of raw
Speaker 3: meat is more common, or in tropical areas that are
Speaker 3: very favorable for that oocyst persistence in the environment. In
Speaker 3: those areas, seripovolence can be as high as fifty seventy
Speaker 3: five or even ninety percent in some areas, and in
Speaker 3: other areas.
Speaker 2: It's a lot lower.
Speaker 3: In the US, it's estimated around twenty two percent, okay,
Speaker 3: and zero prevalence tends to increase with age, which makes
Speaker 3: sense because it's kind of just like you're living your
Speaker 3: life and at some point you'll be exposed. So the
Speaker 3: older people are, the more time they've had to be exposed.
Speaker 3: But these infections really do have pretty serious consequences. In
Speaker 3: the US, it's estimated that the annual cost I know
Speaker 3: you don't like looking at the numbers, but I mean
Speaker 3: the dollar numbers.
Speaker 1: Oh No, I mean I think it's important. I think
Speaker 1: it's just important to keep in mind also that the
Speaker 1: US cost is going to be very different than other
Speaker 1: places that have better health services for their population.
Speaker 3: For sure. But in the US it's estimated that the
Speaker 3: cost of illness is three billion dollars and eleven thousand
Speaker 3: quality adjusted life years lost.
Speaker 1: Wow.
Speaker 3: Also, did you know that over two thousand people develop
Speaker 3: eye disease from toxoplasma in the US every year? But
Speaker 3: and here is something I absolutely did not realize. Toxoplasma
Speaker 3: GANDHII is one of the three Salmonella, Listeria and tea GANDII.
Speaker 3: These three pathogens account for over seventy five percent of
Speaker 3: all deaths due to food born illness in.
Speaker 1: The whoa yeah, whoa right.
Speaker 3: It's estimated that toxoplasma in two thousand and eleven, I believe,
Speaker 3: caused eight percent of hospitalizations and twenty four percent of
Speaker 3: deaths from food born illness.
Speaker 2: So why don't we hear about this more?
Speaker 1: Why don't we hear about this?
Speaker 2: We hear about this?
Speaker 3: You know, bananas tenuous at best. Links with schizophrenia, and
Speaker 3: we don't hear about people dying from toxoplasma infected meat.
Speaker 1: Or cold food. Are these associated with particular Is this
Speaker 1: like an outbreak or are these.
Speaker 3: Individual cases individual cases, so we don't really probably.
Speaker 1: Explains why they're not as headline worthy for sure. For sure,
Speaker 1: for sure.
Speaker 2: Yeah.
Speaker 3: Now that's in humans. It's not only in humans, it's
Speaker 3: not only in mice and rats, and it's not only
Speaker 3: in cats. Over three hundred species of animal can be
Speaker 3: infected that we know of with Tea gondii. Hugely important
Speaker 3: is the fact that because these oss persist in the environment,
Speaker 3: they can get into the soils and the water and
Speaker 3: end up like you mentioned in our oceans. Did you
Speaker 3: know that in Moro Bay alone is in northern California
Speaker 3: by the way, Yeah, okay, in Morbay alone, domestic cats
Speaker 3: deposited seventy seven tons of poop. That's not including free
Speaker 3: roaming cats, which deposited another thirty tons of poop. That
Speaker 3: means forty five hundred little parasites osis per square meter.
Speaker 1: It's really hard to even fathom.
Speaker 3: Yep, because these cats, so infection in cats is generally asymptomatic.
Speaker 3: Cats are the definitive host for the parasite. The parasite
Speaker 3: doesn't cause illness in cats very often at all, but
Speaker 3: cats shed this parasite for up to three weeks at
Speaker 3: a time when they get infected, and they're shedding thousands
Speaker 3: and thousands of these parasites every time they poop. It
Speaker 3: really does have a huge impact on wildlife and other
Speaker 3: animal populations across the globe.
Speaker 1: It's a pretty big conservation and public health problem.
Speaker 3: Yeah, So one of the things that's really interesting is
Speaker 3: that there's a big push to look at toxoplasmosis from
Speaker 3: a one health perspective, which we've talked very briefly about
Speaker 3: one health on this podcast before, but essentially one health
Speaker 3: is just this idea that animal health, wildlife, domestic animal
Speaker 3: and environmental health all play into each other. So looking
Speaker 3: at disease from all of these different aspects and trying
Speaker 3: to get a handle on understanding the risks of disease
Speaker 3: from an interdisciplinary perspective is really important for control, not
Speaker 3: just for humans, but for the entirety of wildlife, domestic animals,
Speaker 3: and the environment. So for toxoplasmosis, that means trying to
Speaker 3: get a better handle on the risks from the environmental perspective,
Speaker 3: so soil studies land use effects also a better understanding
Speaker 3: of the potential effects on human behavior tenuous though.
Speaker 1: They may be.
Speaker 3: Understanding the extent of congenital transmission. It's estimated that there
Speaker 3: are anywhere from four hundred to four thousand cases of
Speaker 3: congenital toxoplasmosis in the US alone every year.
Speaker 1: Wow. And that's it. And we have a relatively low
Speaker 1: prevalence rate. Yeah we did other countries.
Speaker 2: Yeah, we really do.
Speaker 1: And is this is not a reportable illness? Is congenital
Speaker 1: toxo reportable?
Speaker 3: It is not a nationally reportable disease? Wow, which means
Speaker 3: we don't really have a good handle. That's why the
Speaker 3: estimates are anywhere from four hundred to four thousand cases.
Speaker 1: Makes sense? Yeah, yess.
Speaker 2: But then also understanding.
Speaker 3: The wildlife and domestic animal cycles.
Speaker 2: Food safety is.
Speaker 3: Really important in talking about toxin plasmosis. And then like
Speaker 3: you mentioned, outdoor cat monitoring and control efforts and of
Speaker 3: course vaccine development. There is actually a vaccine for sheep
Speaker 3: that's licensed in some countries. Yeah, but there isn't even
Speaker 3: a vaccine for cats, which is kind of bonkers to me.
Speaker 3: There was one that was made at some point, but
Speaker 3: it was very expensive to produce, it was difficult to keep,
Speaker 3: it had a very short shelf life, and cat owners
Speaker 3: didn't care about it, probably because it doesn't generally affect
Speaker 3: cats negatively, so it was discontinued by the manufacturers.
Speaker 1: Huh.
Speaker 2: Yeah, interesting, So that sucks.
Speaker 3: Yeah, it does seem that sort of The biggest ways
Speaker 3: that you're likely to be infected are from contaminated meat sources,
Speaker 3: so cooking your meat properly is important. But also the
Speaker 3: osis can persist in the environment, so contaminated water is.
Speaker 2: A huge issue.
Speaker 3: The osis actually are viable. They're not killed by chemical
Speaker 3: and physical treatments that we use for water treatment, including
Speaker 3: chlorination and ozone treatment.
Speaker 2: Yeah, and they can.
Speaker 3: Survive freezing and pretty high water temperatures, so cool cool. Yeah,
Speaker 3: so toxic is pretty much everywhere. Again, the vast majority
Speaker 3: of humans who get infected will never ever know that
Speaker 3: they were infected, but for people who are imm compromised
Speaker 3: or for pregnant people who get infected the first time,
Speaker 3: the effects can be very devastating.
Speaker 1: Yeah, it kind of remains this vague threat that, Yeah,
Speaker 1: it does.
Speaker 3: And then for wildlife species it can be really damaging
Speaker 3: as well, So it's a really happy ending toxic is
Speaker 3: pretty fish.
Speaker 2: Yeah, Aaron, tell us about your sources.
Speaker 1: I read a couple of books. One I already mentioned
Speaker 1: called The Line in the living Room by Abigail Tucker.
Speaker 1: This is a very fun read. I recommend it. And
Speaker 1: then another book by Catherine McAuliffe called This Is Your
Speaker 1: Brain on parasites and that's another fundread as well. And
Speaker 1: then I read a bunch of different articles, mostly by
Speaker 1: JP Dubey. Oh he's like I read. I think I
Speaker 1: saw some of Yeah, tons and tons of he runs
Speaker 1: troll research.
Speaker 2: Yeah.
Speaker 1: Yeah. And one of the books, yeah, And where I
Speaker 1: got all the information or a lot of the information
Speaker 1: about sort of the human evolution and agricultural settlements was
Speaker 1: from a paper by schwab at All from twenty eighteen.
Speaker 2: It was great, awesome.
Speaker 3: We'll post all of our sources for this episode and
Speaker 3: all of our episodes on our website, this podcast will
Speaker 3: Kill You dot Com under the episode's tab.
Speaker 1: Thank you to Bloodmobile for providing the music for this
Speaker 1: episode in all of our episodes.
Speaker 3: Thank you all for listening and for keeping your cats
Speaker 3: indoors safely with you and with that wash your hands,
Speaker 3: you filthy animals,