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