Speaker 1: Hey, you welcome to Stuff to Blow your Mind. My
Speaker 1: name is Robert Lamb and I'm Joe McCormick, and it's Saturday.
Speaker 1: Time to go into the vault for an older episode
Speaker 1: of the show. This one originally aired on February eighth,
Speaker 1: twenty twenty two. It's part three of our series about thirst.
Speaker 1: Let's jump right in. Welcome to Stuff to Blow Your Mind,
Speaker 1: a production of iHeartRadio. Hey, welcome to Stuff to Blow
Speaker 1: your Mind. My name is Robert Lamb and I'm Joe McCormick,
Speaker 1: and we're back with part three of our series on
Speaker 1: the question of thirst. Now, if you remember, in the
Speaker 1: last episode, Rob we talked about the biology of thirst,
Speaker 1: anticipation of anticipation of the quenching of thirst. Because there's
Speaker 1: this interesting thing where after you drink a glass of
Speaker 1: water when you've been dehydrated, it takes some number of minutes,
Speaker 1: maybe on the order of tens of minutes before that
Speaker 1: water actually gets absorbed through the digestive system and ends
Speaker 1: up in the blood and makes a difference systemically throughout
Speaker 1: the body. And yet you still feel that that thirst
Speaker 1: quinchiness after you have just the first glass of water.
Speaker 1: You're not continuously chugging for ten to twenty minutes at
Speaker 1: least hopefully not. But to start off today, I wanted
Speaker 1: to come back to the question of how it is
Speaker 1: that the body detects, the anticipates the coming changes in
Speaker 1: your blood and your blood osmolality, which again is the
Speaker 1: concentration of dissolved substances like mineral salts in your body's
Speaker 1: water content, and how it anticipates those changes to provide
Speaker 1: you that delicious feeling of having your thirst quenched by
Speaker 1: a glass of water. Now, in the previous episodes, we
Speaker 1: already talked about a few ways that the mouth in
Speaker 1: the throat might detect the introduction of water into the
Speaker 1: body and sort of sin signals to the brain saying hey, okay,
Speaker 1: you can put the thirst on hold for now, there
Speaker 1: are soon coming changes to the body's hydration levels. And
Speaker 1: one of the ideas we talked about was the possibility
Speaker 1: that temperature plays a role, because maybe there's some evidence
Speaker 1: that the power of water to cool the mouth and
Speaker 1: throat sends quinching signals to the brain. And also there
Speaker 1: was some evidence that rodents were using sour taste receptors
Speaker 1: in the mouth to detect the presence of water. But
Speaker 1: Rob maybeing set me straight on this one. I don't
Speaker 1: think it was clear that triggering the sour taste receptors
Speaker 1: actually led to the quinching of thirst. Rather, it seemed
Speaker 1: to encourage more drinking behavior when the mouse was thirsty.
Speaker 1: Is that right? Yes, that's my understanding of these findings.
Speaker 1: But I was actually reading about a few more studies
Speaker 1: on exactly this question of how thirst quinching happens. What
Speaker 1: is the mechanism that leads to these changes in the
Speaker 1: brain that tell you, aha, thou art now quinched. So
Speaker 1: the first thing I wanted to talk about was a
Speaker 1: study that I was reading about a New York Times
Speaker 1: article from twenty eighteen by Verny Greenwood called you get
Speaker 1: thirsty and drink? How does your brain signal you've had enough?
Speaker 1: And this is referring to a paper that I think
Speaker 1: came up in passing in the previous episode, but it
Speaker 1: was by Vinnie Augustine at all in Nature in twenty
Speaker 1: eighteen called Hierarchical neural architecture underlying thirst regulation. And this
Speaker 1: research has been looking at exactly this question we just
Speaker 1: brought up, and they confirmed that, of course there is
Speaker 1: a complex of neurons in the brain that appear to
Speaker 1: cease activity after a thirsty mouse drinks water. So there
Speaker 1: are some neurons that are apparently signaling that generating that
Speaker 1: thirst motivation state. But then when a rodent takes some
Speaker 1: water in through the mouth, those rons shut up, they
Speaker 1: go quiet. So this would be the neural mechanism to
Speaker 1: register quenching. But the question is what is the direct
Speaker 1: mechanism that leads to the changes in those neurons. Now,
Speaker 1: this New York Times article summarizes the findings as explained
Speaker 1: by the first author on that paper, Vanite Augustine quote, Intriguingly,
Speaker 1: what these cells are responding to is not the presence
Speaker 1: of water itself, mister Augustine said. The researchers discovered that
Speaker 1: letting a mouse take big gulps of water would spur
Speaker 1: the neurons into action, but giving it water in gel form,
Speaker 1: which had to be chewed before it could be swallowed,
Speaker 1: did not. Neither did providing water in tiny two second
Speaker 1: long SIPs, even when the animals consumed the same total
Speaker 1: amount of water. In fact, giving the mice oil to
Speaker 1: drink had just the same effect on the neurons as
Speaker 1: gulping water. So that last part is a little gross,
Speaker 1: but based on this fine name, uh, it would kind
Speaker 1: of imply that a major mechanism leading these thirst neurons
Speaker 1: to to say, okay, thirst has been quenched would have
Speaker 1: something to do with like muscular movements in the throat,
Speaker 1: the kind of gulping that you do when you're guzzling
Speaker 1: down a bunch of water really fast. But technically maybe
Speaker 1: it doesn't even have to be water, it's just any
Speaker 1: fluid that you're gulping. I mean, as humans, we don't
Speaker 1: I guess, drink a lot of just straight oil, but
Speaker 1: we do drink a lot of things that are that
Speaker 1: are to varying degrees removed from from from you know,
Speaker 1: from from just a neutral water. So this would make sense, right,
Speaker 1: But if you if you hydrate yourself in some other ways,
Speaker 1: so like the examples that you say, consuming water in
Speaker 1: gel form where you can't like gulp it down really
Speaker 1: that still hydrates you, but that apparently does not lead
Speaker 1: to this immediate quinching signal in the brain. Similarly, with
Speaker 1: drinking water in very small isolated SIPs, I guess in
Speaker 1: those cases you would eventually hydrate your self and your
Speaker 1: thirst will eventually go away, but it will be more
Speaker 1: likely that your body has to just become systemically hydrated
Speaker 1: before the thirst goes away. It's not that sudden quinching
Speaker 1: reward feeling. Now, there was an interesting detail offered here
Speaker 1: about reasons that the body might need to have this
Speaker 1: reaction where we turn off thirst very quickly after getting
Speaker 1: a drink, like why not just wait for your blood
Speaker 1: osmolality to reach the ideal level. Well, in previous episodes,
Speaker 1: we talked about one reason for this, which is that
Speaker 1: you know, if you actually did have to wait for
Speaker 1: your body's water content to get all leveled out right
Speaker 1: before your thirst went away, you might you might like
Speaker 1: kill yourself drinking gallons and gallons of water because you
Speaker 1: know over the course of the tens of minutes that
Speaker 1: it takes for this change to take hold. But there's
Speaker 1: another reason, one of the authors of this paper brings up.
Speaker 1: That's in this Greenwood article in the Times quote. Aside
Speaker 1: from the specter of water intoxication, there are good reasons
Speaker 1: to drink only the minimum amount necessary when an animal
Speaker 1: lowers its head to drink, doctor Oka speculated, and that's
Speaker 1: doctor Yukioka. It's in quite a vulnerable position. Quote, if
Speaker 1: you double the time of ingestion, that should double the
Speaker 1: risk of being prey, he said, And I thought that
Speaker 1: was interesting too. I mean, I think it is true
Speaker 1: that in the natural environment, as we brought up in
Speaker 1: the previous episode, going for water is often putting yourself
Speaker 1: in a vulnerable position, you know, maybe exposing yourself from
Speaker 1: hiding or shelter and sort of turning your attention away
Speaker 1: from scanning your surroundings. Yeah. I mean in many cases too,
Speaker 1: they the access point of the water might not provide
Speaker 1: much in the way of cover for smaller animals, and
Speaker 1: then for larger animals there may be you know, bodily
Speaker 1: positions they have to get into to drink that put
Speaker 1: them in a greater state of vulnerability. Like I'm thinking
Speaker 1: of a draft for instance. Though draft, of course is
Speaker 1: already formidable animal U but but still there's a certain
Speaker 1: awkwardness present when it actually has to drink water. Sorry,
Speaker 1: I just started thinking about game or fuel. Um, yeah,
Speaker 1: this is this, says. I have no research to back
Speaker 1: this up. They're just observational material for me. But I
Speaker 1: think everyone knows that I enjoy watching the squirrels, and
Speaker 1: we have a bird bath outside near our feeders, and
Speaker 1: the bird bath is positioned right up against the fence,
Speaker 1: and the squirrels drink from that all the time. But
Speaker 1: I wonder how much I wonder how much of that
Speaker 1: is that they're able to drink from the bird bath
Speaker 1: while essentially remaining in a vertical position attached to the
Speaker 1: to the fence, like they don't have to, you know,
Speaker 1: go across a clearing. They have, I guess, pretty good
Speaker 1: cover for a squirrel. Those squirrels are bold in other
Speaker 1: ways that, you know, make you think that they're they're
Speaker 1: less concerned, or they're or they're in control of the
Speaker 1: situation as far as potential predators go. So if you
Speaker 1: happen to have sitter squirrels and rover squirrels, your bird
Speaker 1: bath is positioned in such a way that even the
Speaker 1: sitter squirrels could could get to it. I guess so.
Speaker 1: But then, yeah, I don't know. I'd be interested to
Speaker 1: hear what anyone else out there has observed with their
Speaker 1: squirrels and drinking water from bird baths and other water sources.
Speaker 1: They seem to like one thing versus the other. I
Speaker 1: don't know. They certainly drink more water than my cat.
Speaker 1: I'll give them that well. Anyway, there was another article
Speaker 1: from the very next year, also in the New York Times,
Speaker 1: also by Greenwood, covering follow up research from some of
Speaker 1: the same scientists. So this was published May thirty first,
Speaker 1: twenty nineteen, just called the Neurobiology of Thirst, and this
Speaker 1: is summarizing a study published in twenty nineteen in the
Speaker 1: journal Neuron where the authors oh again the first author
Speaker 1: on this one was Vanite Augustine and it was called
Speaker 1: Temporally and spatially distinct thirst satiation Sig and the authors
Speaker 1: here found that the pleasure we get from drinking when
Speaker 1: thirsty is once again not directly related to hydration. It
Speaker 1: is a reward pathway separated by both time and space
Speaker 1: from the body's hydration and osmolality monitoring mechanisms. And one
Speaker 1: of the major findings in this paper is that though
Speaker 1: drinking water is associated with a dopamine release, this is
Speaker 1: a typical signal that the brain is expecting a reward. Right.
Speaker 1: You know, things that you want, you want to get
Speaker 1: and feel good when you get them. That's often that
Speaker 1: involves a dopamine release. But the feeling of reward in
Speaker 1: the brain here is apparently not tied to becoming hydrated
Speaker 1: after being dehydrated, but specifically to the act of drinking
Speaker 1: water through the mouth. So if you're dehydrated and then
Speaker 1: you suddenly receive water through an iv or even via
Speaker 1: a direct injection into the stomach, your thirst will eventually
Speaker 1: go away after your body adjusts to the new fluid levels,
Speaker 1: but you won't get that feeling of reward satisfaction or
Speaker 1: the corresponding dopamine release. Those come specifically from the activity
Speaker 1: of drinking, the gulping of water through the mouth. And
Speaker 1: picking up on this, I was actually looking at one
Speaker 1: more paper that had an interesting finding. I wouldn't have
Speaker 1: mentioned this. Other one was a little earlier. This was
Speaker 1: from twenty sixteen published in Nature called thirst neurons anticipate
Speaker 1: the homeostatic consequences of eating and drinking, And this is
Speaker 1: by Zimmerman at All And this study found, among other things,
Speaker 1: a dual track monitoring system for thirst management. So along
Speaker 1: the lines we've already been talking about. It found that
Speaker 1: if you take mice and you give them some salt
Speaker 1: and make them thirsty, drinking water rapidly inhibits neurons in
Speaker 1: a region of the brain called the subfornical organ or SFO,
Speaker 1: and that leads to thirst quenching. And of course this
Speaker 1: is before there's any notable change in blood osmolality. But
Speaker 1: it also found that if you take these thirsty mice
Speaker 1: and you give them very salty water and the opportunity
Speaker 1: to drink it, they will drink it, and initially they
Speaker 1: will gulp it down and it will inhibit the SFO
Speaker 1: neurons and apparently quench thirst just like the freshwater. But
Speaker 1: the quenching doesn't last for very long, and they write quote,
Speaker 1: this initial decline was reversed after approximately one minute. This
Speaker 1: indicates that the rapid anticipatory response to drinking has at
Speaker 1: least two components, an immediate signal that tracks fluid ingestion
Speaker 1: and a delayed signal that reports on fluid tonicity, possibly
Speaker 1: generated by an esophageal or gastric osmo sensor. So if
Speaker 1: you put all of this together, it seems like you've
Speaker 1: got at least three different time dependent levels of sort
Speaker 1: of the body's quinch watch. So you put them all together,
Speaker 1: and you've got one system that's like, are you gulping fluid?
Speaker 1: If you are, oh, that's very good, very good thou
Speaker 1: art quinched, But then there's a second system on a
Speaker 1: slight delay from that one, roughly one minute of delay
Speaker 1: in mice. It's like, wait a second, what exactly was
Speaker 1: that you were just gulping? Was that oil or was
Speaker 1: that super salty water? You know, what are you trying
Speaker 1: to pull? And if it well, if it was not
Speaker 1: good fresh water, then it will cancel, cancel the quinch
Speaker 1: and return the thirst. And then finally I guess there's
Speaker 1: just the direct blood volume in osmolality monitoring, which is
Speaker 1: on a much greater delay than the other two. So,
Speaker 1: first of all, reminder, if anyone else, if anyone's interested
Speaker 1: in the whole drinking saltwater thing, we did a whole
Speaker 1: episode on drinking saltwater a while back. You should be
Speaker 1: able to find that in the archives. Not a good
Speaker 1: idea was it was one of the main findings there.
Speaker 1: But the other thing, I think, and we've kind of
Speaker 1: we've kind of touched on this a little bit already,
Speaker 1: but you know, it would be in a steak to
Speaker 1: think of like, Okay, it's just you know, what's drinking water,
Speaker 1: water in water out, you know, even if you you
Speaker 1: then acknowledge, okay, well, you know, the levels have to
Speaker 1: be just right. But it's it's more than that. It's
Speaker 1: not like organisms just one day we're like, hey, there's
Speaker 1: water we can drink that we should use this to
Speaker 1: our advantage. Now, like we are of water. So it's
Speaker 1: like water in am water evolved out of things in water, etc.
Speaker 1: So it's it makes sense that there would be a
Speaker 1: more complex relationship with multiple triggers that you know that
Speaker 1: we're still trying to understand. Yeah, I mean, as we
Speaker 1: said at the very beginning, you you are the direct
Speaker 1: descendant of creatures that long ago lived in the ocean
Speaker 1: and all of your ancestors, just like you brought the
Speaker 1: ocean with you onto land. The ocean is now inside
Speaker 1: your skin. Yes. Oh, and before I wrap up, this
Speaker 1: last study I mentioned also documents interesting evidence for the
Speaker 1: the oral cooling mechanism of thirst quenching that I brought
Speaker 1: up in previous episode. So the authors here say that quote.
Speaker 1: We found that a playing cold but not room temperature
Speaker 1: metal to the oral cavity of a wake thirsty mice
Speaker 1: was sufficient to rapidly inhibit SFO neurons. Thus, temperature dependent
Speaker 1: modulation of SFO neurons may explain the enigmatic connection between
Speaker 1: oral cooling and thirst, including why thirsty rodents will avidly
Speaker 1: lick cold metal, and humans report that sucking on ice
Speaker 1: chips rapidly relieves thirst. That's interesting. I hadn't really thought
Speaker 1: about that with sucking on ice chips though, though obviously,
Speaker 1: I mean that's I think that's something we all do
Speaker 1: if we have access to iced drinks. Of course, the
Speaker 1: thing with ice, of course, is that ice melts in
Speaker 1: your mouth as well and actually serves to hydrate you, right,
Speaker 1: but that the cooling effect of having the ice in
Speaker 1: the mouth may provide a level of thirst quenching sensation
Speaker 1: that goes beyond the actual amount of water you're taking
Speaker 1: in from that ice. This gives me a great idea, so,
Speaker 1: showrunners and so forth, of the Witcher, if you're listening,
Speaker 1: I would love to see a scene where Henry Cavill's
Speaker 1: Witcher character share some wisdom and he's like, sometimes when
Speaker 1: when I'm thirsty, I just have a good lick of
Speaker 1: my sword takes care of you know. That'd be great,
Speaker 1: And you haven't seen there was just kind of licking
Speaker 1: is the blade of his sword. I'd never heard this
Speaker 1: before that apparently thirsty, thirsty rodents will lick cold metal.
Speaker 1: But yeah, I had not seen it. Yeah, but it's
Speaker 1: good enough for mice, it's good enough for the witcher.
Speaker 1: I think all Garrold's just gonna that's that's how you
Speaker 1: cut your tongue, buddy, That's how you cut your tongue.
Speaker 1: Oh you know. It reminds me of brom Stoker's Dracula.
Speaker 1: We have that wonderful scene where Gary Oldman's elderly Dracula
Speaker 1: licks the blood from the straight razor. See, he was
Speaker 1: thirsty and he quenched the thirst. But also hopefully the
Speaker 1: blade was cold enough that that also had an fact.
Speaker 1: I well, I guess after all these studies we looked
Speaker 1: at on the quenching mechanism, I'm wondering, so the two
Speaker 1: main different ones have emerged. One is the oral cooling
Speaker 1: mechanism and the other is the gulping mechanism. You know,
Speaker 1: the muscular movements in the throat is you're swallowing large
Speaker 1: amounts of water. And I guess I'm not sure if
Speaker 1: these two different explanations are competing or if they're complementary.
Speaker 1: Maybe they both play a role in regulating these thirst neurons.
Speaker 1: In the SFO. I'm not sure. Now, given all the
Speaker 1: things we've discussed about the complexity of thirst, sensations, and
Speaker 1: water acquisition by various organisms, I thought it might be
Speaker 1: interesting to look at a couple of examples that, in
Speaker 1: different ways seem to hijack mechanisms of related to thirst
Speaker 1: and our relationship with water, not only ours, but also
Speaker 1: some other organisms for the benefit of a life form.
Speaker 1: Not the life form that is that is potentially thirsty,
Speaker 1: but a life form that is that is hijacking that organism,
Speaker 1: such as a parasite or a virus. Oh. Interesting. So
Speaker 1: the first one I want to mention here is is
Speaker 1: one that definitely affects humans, and that is rabies. Now,
Speaker 1: I imagine I think everyone has heard of rabies. If not,
Speaker 1: buckle in because I'm gonna share a little bit. Though.
Speaker 1: This is obviously a topic that you know, we could
Speaker 1: really bust out if we wanted to and give a
Speaker 1: full episode treatment. But even if you're just vaguely familiar
Speaker 1: with rabies, uh, you know, you might not grasp the
Speaker 1: full danger and horror of this particular zoonotic viral disease.
Speaker 1: I think a while back, I've read at least somebody
Speaker 1: making the case that rabies is a contender for like
Speaker 1: the worst disease known. Yeah, it is pretty horrifying and
Speaker 1: for a lot of people in um in the world,
Speaker 1: particularly and let's let's say United States, you're lucky enough
Speaker 1: to live largely removed from it. I think that the
Speaker 1: US is sometimes class of classified as being free of
Speaker 1: canine rabies. Now, there are still cases of canine rabies
Speaker 1: that pop up, and there are deaths that occur, but
Speaker 1: not at the same rate as other parts of the
Speaker 1: world where the problem has not been contained as well.
Speaker 1: So it's rabies is caused by the virus Lisa virus,
Speaker 1: which essentially means rage poison. It's named for the Greek
Speaker 1: goddess Lissa, the goddess of rage, fury and rabies, the
Speaker 1: daughter of Nicks, sprung from the blood of Lauranus, and
Speaker 1: she pops up in different tales, like for instance, at
Speaker 1: the urging of Hera, she inflicts madness on Heracles, and
Speaker 1: in some tellings she's also involved in the punishment of
Speaker 1: the hunter Acteon, who's torn apart by his own mad
Speaker 1: hunting dogs, and in memory Serves. There are some interesting
Speaker 1: treatments of the this latter tale in art. Yeah, I
Speaker 1: think he looked at a god or something to that effect.
Speaker 1: You know, you don't have to do much to get
Speaker 1: to torn apart by dogs when you're dealing with the
Speaker 1: Greek pantheon. Yeah. I don't remember all the details, but
Speaker 1: I think he makes Artemis angry for some reason, and
Speaker 1: then he's a hunter. But then he's transformed into the quarry,
Speaker 1: like he's transformed into a stag or something, and then
Speaker 1: his own hunting dogs hunt atch. Right, there's some transformation
Speaker 1: involved there as well. So humans have been exposed to
Speaker 1: rabies for a very long time. It's um. It's thought
Speaker 1: that it probably originated in old world bats and especially
Speaker 1: flourished during the heyday of of dog domestication. So it is,
Speaker 1: you know, it is. It is definitely tied to the
Speaker 1: canine world. According to the History of Rabies in the
Speaker 1: Western Hemisphere by Velasco Villa at All, published in Anti
Speaker 1: Viral Research, the earliest record of a disease affecting humans
Speaker 1: that's consistent with rabies and associated with dogs is found
Speaker 1: in the Eshnuna cuneiform law tablets in ancient Mesopotamia dating
Speaker 1: back to the eighteenth through nineteenth centuries BC. Wow, Yeah,
Speaker 1: and I believe memories served it. It concerns like laws
Speaker 1: concerning dogs biting people, like if you you have a
Speaker 1: dog and it bites somebody. And of course we have
Speaker 1: other references to either cases that seem like they could
Speaker 1: be rabies, or we feel pretty strongly are referring to rabies.
Speaker 1: Aristotle wrote seemed to have wrote of it in three
Speaker 1: thirty BC. Quote dogs suffer from the madness. This causes
Speaker 1: them to become very irritable, and all animals they bite
Speaker 1: become diseased. Democratus and Hippocrates also wrote of it as well,
Speaker 1: and there are comparisons to raging dogs in the Iliad
Speaker 1: that it seems like maybe you're less certain that this
Speaker 1: is referring, because of course a dog can rage. I
Speaker 1: guess it doesn't have to be rabid. But there are
Speaker 1: also mentions of the dog star Ryan exerting a malignant
Speaker 1: influence on human health, and rabies is just a terrible disease,
Speaker 1: especially when you really get into what it can do
Speaker 1: to an organism and what it can do to a
Speaker 1: human being. Today, it's vaccine preventable, and the vaccines keep improving,
Speaker 1: but once clinical symptoms appear, it is one fatal According
Speaker 1: to the World Health Organization, in ninety nine percent of cases,
Speaker 1: domestic dogs are responsible for spreading it to humans. Again,
Speaker 1: in the United States, it is effectively we're effectively canine
Speaker 1: rabies free, though you will still find cases that occur
Speaker 1: and deaths that occur, so it's it's still possible, but
Speaker 1: it is largely under control. In other parts of the
Speaker 1: world it's not the case. And so you know, this
Speaker 1: is all great reminder why it is important to get
Speaker 1: your dog a rabies vaccine and to also get yourself
Speaker 1: immunized if you come into contact with the disease, right,
Speaker 1: and that time is very important there, right, Yeah, so
Speaker 1: that the incubation period for rabies is typically two to
Speaker 1: three months, but may vary from one week to a year.
Speaker 1: And I think it depends on like the viral load
Speaker 1: and you know, being introduced into your body and some
Speaker 1: other factors. And then there are two forms of the
Speaker 1: disease that are possible in humans. So once you know
Speaker 1: this virus is in your system, one version is paralytic rabies.
Speaker 1: This only occurs in about twenty percent of cases, and
Speaker 1: it consists of gradual muscle paralyzation, coma, and death. It's
Speaker 1: often misdiagnosed, but again, like twenty percent of cases, this
Speaker 1: is what occurs. The other, however, is the the the
Speaker 1: incarnation of rabies that certainly brings to mind these ideas
Speaker 1: of strange curses from the gods, you know, the really
Speaker 1: horrible stuff, and that's furious rabies. Symptoms here include hyperactivity,
Speaker 1: excitable behavior, hydrophobia, the fear of water, and sometimes aerophobia
Speaker 1: as well, fear of drafts of fresh air or you know,
Speaker 1: blasts of air, that sort of thing. And death occurs
Speaker 1: in these cases within a few days due to cardiac arrest. Now,
Speaker 1: I gotta admit I've always heard rabies described as or
Speaker 1: associated with this idea of hydrophobia, which obviously, yeah, that
Speaker 1: means fear of water, but I never knew exactly what
Speaker 1: to make of that, Like what does that mean in practice? Yeah,
Speaker 1: because it's you know, when you start thinking about like
Speaker 1: the things that a viral infection does, like you know,
Speaker 1: to what extent is it about prolonging that virus or
Speaker 1: or or you know, achieving something, and it's um you know,
Speaker 1: in its cycle, and as you look into it, it's
Speaker 1: it's really quite interesting. So again, this is the really
Speaker 1: horrible fate the furious rabies. If one comes down with
Speaker 1: this person's behavior and mood is drastically altered, anxiety, hallucinations, confusion, paranoia, terror,
Speaker 1: and they tend to experience both a profound thirst and
Speaker 1: a severe inability to quench that thirst. So what does
Speaker 1: all this mean? Well, keep in mind that saliva is
Speaker 1: central to rabies transmission. You know, if you think of
Speaker 1: you just hear the words rabid dog, the image that
Speaker 1: probably comes to mind is that of a dog frothing
Speaker 1: at the mouth, right, with frothing saliva right, And it's
Speaker 1: generally understood that I guess the saliva is what transmits
Speaker 1: the disease. Like if you are bitten by a dog
Speaker 1: that has rabies or by an animal that has rabies,
Speaker 1: the saliva will transmit it to your blood. Is that
Speaker 1: a real route of transmission? Yes, that is the primary
Speaker 1: route of transmission. Bites and scratches are are the most
Speaker 1: common ways that it is just transmitted. There are other ways,
Speaker 1: you know, basically any infected fluid could do it, but
Speaker 1: those are uncommon compared to bites and scratches, especially when
Speaker 1: you're you know, think of a dog, think of think
Speaker 1: of even you know, a bat or any other organism
Speaker 1: that would carry rabies. The bite is the thing, and
Speaker 1: it's steered in these cases by you know, enhanced aggression
Speaker 1: and altered behavior. And seemingly, you know, the mouth is
Speaker 1: primed to transmit the virus by excess infectious frothing saliva. Okay,
Speaker 1: so much in the same way that respiratory viruses that
Speaker 1: are spread by aerosols or droplets might tend to cause
Speaker 1: the infected person to cough or sneeze in order to
Speaker 1: further spread themselves to other people. Uh, this disease that
Speaker 1: is spread often by saliva into blood through bites, Uh,
Speaker 1: it would tend to cause the infected animal to froth
Speaker 1: in the mouth with a lot of infectious saliva and
Speaker 1: to be irritable or or aggressive in ways that would
Speaker 1: lead to biting. Right, And that brings us back to
Speaker 1: this question of hydrophobia. Like, then then for what reason,
Speaker 1: you know, seemingly, like what role does does the fear
Speaker 1: and does this carror at the idea of water have
Speaker 1: to do with anything? So in humans this peers to
Speaker 1: manifest as a kind of panic that sets in when
Speaker 1: presented with water and difficulty in or inability to drink,
Speaker 1: like attempts to drink may result in spasms. There is
Speaker 1: some clinical footage you can find online of individuals that
Speaker 1: have been diagnosed with rabies attempting to drink water, and
Speaker 1: I do not, I do not very disturbing footage, so
Speaker 1: I don't recommend seeking it out. But if you find
Speaker 1: yourself in need of of of the visuals for this, uh,
Speaker 1: there there is some documentation online. I believe a case
Speaker 1: in Vietnam is typically typically cited here. Now, does the
Speaker 1: difficulty with drinking water when someone is infected with rabies
Speaker 1: usually have something to do with difficulty in muscle control,
Speaker 1: for like swallowing through neurological routes. Yes, yes, definitely so.
Speaker 1: And the insidious nature of all this, though, is that
Speaker 1: since the individual is prohibited from drinking water by the infection,
Speaker 1: or at least the drinking water becomes excruciatingly difficult, saliva
Speaker 1: production increases. You have hypersalivation, and they can't swallow the
Speaker 1: excess saliva, and that's and they can't wash away this
Speaker 1: excess frau thing saliva. So, in other words, it primes
Speaker 1: the victim's mouth to be this potent transmitter of the virus,
Speaker 1: especially through a bite. So it's um. Yeah, it has
Speaker 1: a real insidious quality to it. But as as horrible
Speaker 1: as rabies is. Again, fortunately there are vaccines that exist, right, yes,
Speaker 1: So again all a great reminder get your pet vaccinated
Speaker 1: for rabies. And if you come into contact with a
Speaker 1: with an animal that has rabies or may have had rabies,
Speaker 1: you definitely need to go to a doctor. They can
Speaker 1: take care of it. You don't want this, this, this
Speaker 1: is not an illness you want running its course. Yeah,
Speaker 1: thank now. I wanted to share another example though that
Speaker 1: seems to go or potentially goes in the opposite direction. Uh.
Speaker 1: Rabies inhibits thirst and and and alters thirst in that direction.
Speaker 1: But if we look to to to the world of
Speaker 1: the horsehair worm, we see something that that may possibly
Speaker 1: be involved in generating excessive thirst in the host. So uh,
Speaker 1: this would have to do with parasitoid worms from the
Speaker 1: phylum Nematomorphah. They're known as horsehair worms because they're threadlike
Speaker 1: round worms that resemble the hair of a horse's tail
Speaker 1: or maine. Now, some people may have seen these before.
Speaker 1: These are creatures that you'll sometimes fine living free in
Speaker 1: a puddle or stream. I think I saw one once
Speaker 1: like this while while walking on my mom's property. But
Speaker 1: you can also see them occasionally burst out of the
Speaker 1: body of a cricket, mantis, beetle, or other host organism,
Speaker 1: very much like a xenomorph. Oh, now, maybe I was
Speaker 1: seeing something else, but I know I've seen video of
Speaker 1: something that was like a long, thin worm that was
Speaker 1: just gradually spooling out of a cricket sexoskeleton to just
Speaker 1: and it just kept spooling and spooling and spooling, almost
Speaker 1: like the clown car where you know, fifty clowns get
Speaker 1: out of a Volkswagen. But it's a worm that seems
Speaker 1: bigger than the cricket it was inside, yes, and it's
Speaker 1: it's crazy to watch. I have a very vivid memory
Speaker 1: of being in a junior high band environment and there
Speaker 1: was a cricket on the floor and somebody in a
Speaker 1: neighboring section was grossed out by the presence of the cricket,
Speaker 1: and so they stopped it. And then once they had
Speaker 1: stomped the cricket, this horsehair worm began emerging from the cricket,
Speaker 1: which of course only further grows out the individual who'd
Speaker 1: stopped the cricket. So there's kind of there's some sort
Speaker 1: of weird, horrific justice in that. Like if you think
Speaker 1: the crickets grows, will just wait till you see what
Speaker 1: the encore is. Surely it helped that in band practice
Speaker 1: that day you were playing Carmena barana. Yeah, if only so.
Speaker 1: The interesting thing here is that the adults of this species,
Speaker 1: in these these organisms, they are free living in the water,
Speaker 1: but the larva are parasitic and grow to adulthood inside
Speaker 1: the body of an insect. So I think you can
Speaker 1: all imagine how this probably goes down. A male and
Speaker 1: male horsehair worms mate and damp soil and fresh water,
Speaker 1: and then the female lays millions of the eggs. These
Speaker 1: eggs hatch and the tiny larvae insist on vegetation near
Speaker 1: the water's edge. And then what happens while a cricket
Speaker 1: or some other suitable host drops by, it ends up
Speaker 1: eating that larva one way or another, either either the
Speaker 1: you know, like a cricket is eating the grass, or
Speaker 1: like a mantis is going to eat the larva itself.
Speaker 1: And so what happens then is a like a cricket
Speaker 1: comes along and it eats the grass that has this
Speaker 1: larva on it, or if it's a carnivorous mantis, well
Speaker 1: then it eats a cricket that has already been infected
Speaker 1: by the larva. In either case, the larva winds up
Speaker 1: inside of another organism, the cyst dissolves, and then the
Speaker 1: juvenile worm escapes, bores through the gut wall, and starts
Speaker 1: absorbing nutrients from the host organism. This worm has a
Speaker 1: move fast and things philosophy. It is a It is
Speaker 1: a disruptor of the internal organs of its host. Right,
Speaker 1: And at this point, it's kind of it's kind of
Speaker 1: like you can imagine it like a stowaway in the
Speaker 1: hold of a ship. You know, it's it's rummaging around,
Speaker 1: it's eating some of the stored food supplies, maybe eating
Speaker 1: the occasional crew member on that ship and minute and
Speaker 1: otherwise also damaging the ship. But it doesn't need If
Speaker 1: you're a stowaway human stow and a ship, what do
Speaker 1: you want to do? You want to get to a
Speaker 1: port somewhere, right and uh, And likewise, with this worm,
Speaker 1: it needs to get to water or damp soil in
Speaker 1: order to continue its life cycle. Now, if if something
Speaker 1: happens to the cricket. If it's gets stomped in on
Speaker 1: the floor of a middle school band room, it's going
Speaker 1: to escape. It's going to you know, abandoned ship, but
Speaker 1: it needs to get to damp soil or fresh water.
Speaker 1: So it may be moving fast and breaking things, but
Speaker 1: it's going to try to do so in such a
Speaker 1: way that it ends up at a certain place when
Speaker 1: when the whole thing goes to put right, it needs
Speaker 1: to steer the host in the right direction. And so
Speaker 1: this is where we get that bit of parasitic hijacking
Speaker 1: in action um or at least that's that's one hypothesis
Speaker 1: of exactly what's going on. That the worm instills a
Speaker 1: crazed thirst in the host so that it seeks out water.
Speaker 1: That's sometimes referred to as the thirst hypothesis. An alternate
Speaker 1: hypothesis states of the worm simply waits till the host
Speaker 1: finds water on its own, and then it jumps out.
Speaker 1: And it's my understanding that we're really not one hundred
Speaker 1: percent sure what happens. That there's some some interesting evidence
Speaker 1: for both both hypotheses. Ed Young and a twenty fourteen
Speaker 1: Ted talk um mentioned that there's research that indicates that
Speaker 1: this may occur because the organism releases proteins that alter
Speaker 1: the crickets brain functionality. So and there does seem to
Speaker 1: be some sort of of It seems like there is
Speaker 1: a strong case to be made some sort of hijacking
Speaker 1: is taking place, and if that's occurring, it may be
Speaker 1: pushing the animal towards water via thirst. Okay, so I
Speaker 1: guess that would mean you might be able to notice
Speaker 1: this if you had a place where a bunch of
Speaker 1: insects were getting infected by this parasite, they would be
Speaker 1: showing a lot of drinking behavior, a lot of water
Speaker 1: drinking behavior, right. But then again, yeah, there's also the
Speaker 1: other argument. Well, it's just it's waiting until the water
Speaker 1: is until it's drinking. Even even that, that would be
Speaker 1: pretty impressive because it's that like, how does the how
Speaker 1: does the worm know what's going on inside the darkness
Speaker 1: of the cricket or the darkness of the mantis that
Speaker 1: enables the stowaway to know that there is water or
Speaker 1: damp soil close at hand. But I was looking at
Speaker 1: some of the papers that discussed this, there was a
Speaker 1: this is of course, this is a much older paper
Speaker 1: now but there was a two thousand and one study
Speaker 1: published in the German journal zoo Logisha and Zeiger that
Speaker 1: says that the thirst hypothesis has been supported by observation
Speaker 1: of quote unquote suicidal behavior by infected mantis is in
Speaker 1: southern France that would seemingly jump into the water and
Speaker 1: then immediately outcomes the worm. So that would be a
Speaker 1: case where yeah, like the mantis is not just going
Speaker 1: to the water, it is to drink and then it
Speaker 1: bursts out. It's actually jumping in. It's it's it's giving
Speaker 1: up the ghost. So but I guess with that you
Speaker 1: still would have to ask your question, at what point
Speaker 1: is there some hijacking of behavior. Was it the seeking
Speaker 1: the water to begin with or was it something that
Speaker 1: kicked in when the creature was close to water. So
Speaker 1: we're not sure exactly you know which way way to
Speaker 1: go on this as far as I understand based on
Speaker 1: the research I was looking at. But it seems like
Speaker 1: either way you're getting into these interesting Um you're getting
Speaker 1: into the relationship between the host organism and water. You
Speaker 1: know something about its uh it's bodily awareness of water
Speaker 1: or the thirst or desire to be in close proximity
Speaker 1: to water, and of course that is ultimately what the
Speaker 1: parasite wants as well. Right, So the parasite either needs
Speaker 1: a mechanism of making the host to go drink water
Speaker 1: or knowing when the host is drinking water. Right. Oh,
Speaker 1: in case anybody's worried, it's my understanding that occasionally humans
Speaker 1: end up ingesting these things, But I don't think there's
Speaker 1: ever been any evidence or anything to support the idea
Speaker 1: that they're capable of hijacking human behavior. Again, if that
Speaker 1: is indeed what's happening in the case of crickets and mantises, well,
Speaker 1: what happens when humans do ingest them. It's just kind
Speaker 1: of gross. They could like bombit them up. I was looking.
Speaker 1: There were two Japanese cases reported in twenty twelve due
Speaker 1: to the accidental ingestation of infected insects. I think in
Speaker 1: these cases that this has occurred via the consumption of
Speaker 1: vegetables that had those insisted larvae on them. You're in
Speaker 1: it a Some vegetables seem like they'd be a lot
Speaker 1: better at hiding a little stowaways than others. Oh yeah,
Speaker 1: I have this consistent problem with broccoli. I love broccoli.
Speaker 1: I love cooking with it. But I a number of
Speaker 1: times I've been like giving it a rinse before I
Speaker 1: cook it or something, and then I'm like, oh, there's
Speaker 1: just a bug up in the up in the tree
Speaker 1: limbs there. It's hiding out in a little fork in
Speaker 1: the in the florets. That's true. I mean, I guess
Speaker 1: the it's kind of a this kind of the thing
Speaker 1: about broccoli, right, is that the thing that makes it
Speaker 1: so delicious, that's it's so great to cook because you
Speaker 1: get you know, all the oil or the seasoning, it
Speaker 1: ends up just getting embedded there in all the little
Speaker 1: mooks and crannies. It also means they are all these
Speaker 1: additional places that I guess something could potentially hide, or
Speaker 1: you could just end up with some dirt or grid
Speaker 1: in there. Maybe I'm just getting my broccoli from really
Speaker 1: buggy sources. I don't know. Sometimes I get like CSA broccoli,
Speaker 1: that's it's it's really nice, good stuff, but there's just
Speaker 1: like a there's just a big old bug in there,
Speaker 1: just just like tarantulas crawling out of it through your
Speaker 1: kitchen and stuff. Almost. I mean, it's all just a
Speaker 1: good reminder, you know, wash your vegetables everybody, even if
Speaker 1: you're not sure they need it. You know, you give
Speaker 1: them a once over? Why not? Right, you'll feel better
Speaker 1: about it, especially if you're if you're listening to this
Speaker 1: episode whilst cooking. All right, we're gonna go ahead and
Speaker 1: close out Thirst Part three. What do you think, Joe?
Speaker 1: Do you think we'll be back with Thirst four colon
Speaker 1: Thirst for Knowledge the Return of Jack Thirst. Yes, yes, yes,
Speaker 1: we will be back. I'm sure of it. Yeah, like
Speaker 1: this Thursday back this Thirst today back, Yes Thursday, this Thursday,
Speaker 1: Thirst Part four, Thirst for More Knowledge, the final chapter
Speaker 1: on the final chapter only on Stuff to Blow Your
Speaker 1: Mind or some other topic. I don't know. We'll see
Speaker 1: I guess all right. In the meantime, if you would
Speaker 1: like to check out other episodes of Stuff to Blow
Speaker 1: your Mind, you know where to find them. They're in
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Speaker 1: Oh yeah. Tuesday and Thursday Corps episodes, Wednesday's Artifact, Monday's
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