• kaliqt 7 days ago |
    Checkmate parasites.

    But seriously, I worry about this level of parasite infecting humans one day.

    • someothherguyy 6 days ago |
    • alexey-salmin 6 days ago |
      Well the Guinea worm does force humans to get into water to complete the parasitic cycle. But it's also on track to be fully eradicated.

      I think a parasite affecting human behavior in a substantial way is risking detection and elimination. So unlike with mantises this decreases the chance of survival, unless you paint a zombie-apocalypse kind of scenario.

      A successful human parasite has to alter the host behavior in a very subtle way. This could be happening even now and we wouldn't know. There's some evidence this is the case with toxoplasma increasing affection towards cats.

      • rstuart4133 6 days ago |
        > Well the Guinea worm does force humans to get into water to complete the parasitic cycle.

        How they do this [0]:

        - Humans typically get infected when they unintentionally ingest copepods while drinking water.

        - During digestion the copepods die, releasing the D. medinensis larvae. The larvae exit the digestive tract by penetrating the stomach and intestine

        - About a year after the initial infection, the female migrates to the skin, forms an ulcer, and emerges.

        - Upon reaching its destination, the worm forms a fluid-filled blister under the skin.[5] Over 1–3 days, the blister grows larger, begins to cause severe burning pain

        - When the wound touches fresh water, the female spews a milky-white substance containing hundreds of thousands of larvae into the water.

        - The larvae are eaten by copepods, and after two to three weeks of development, they are infectious to humans again.

        [0] All of the above was copy & pasted from: https://en.wikipedia.org/wiki/Dracunculiasis

        • praptak 6 days ago |
          Part of the eradication effort was hacking this mechanism by convincing humans to use a closed container of water when this happens. The contaminated water can then be safely disposed thus breaking the cycle.
      • dotancohen 6 days ago |
        Star Trek actually did an episode which addresses such a parasite. The episode was one of several episodes banned in a few places, I think for showing how the uninfected humans had to eradicate the infected humans violently.
        • nilamo 6 days ago |
          Star Trek did a whole Wrath of Khan that addresses such a parasite :p
      • ithkuil 6 days ago |
        Humans routinely have very weird behaviours and while often we classify them as illness who knows how many of those we just call "a political view".
        • HKH2 6 days ago |
          SSRIs, birth pills and other 'harmless' drugs modify behaviour too.
          • ithkuil 6 days ago |
            Fwiw food and lack thereof modifies behaviour too.
            • galleywest200 6 days ago |
              If I fail to eat regularly for about 3 days I sink into a deep funk which takes a few days of regular eating to come out of.

              I used to/have a problem where I just don't have the energy to eat due to being hungry and its a viscious cycle.

              • HKH2 6 days ago |
                What happens when you fast?
                • lostlogin 6 days ago |
                  Isn’t that failing to eat regularly?
                  • HKH2 5 days ago |
                    No, because it's done intentionally.
        • unfitted2545 6 days ago |
          This idea has grown on me a lot after watching Sam Harris’ 2013 Ted Talk, on deconstructing religion, logic and morality:

          https://youtu.be/qn3ITqtGzQ8

        • lostlogin 6 days ago |
          As you say, there are a lot of these connections, another is increased religiosity with neurological disorders like epilepsy and schizophrenia.

          https://pmc.ncbi.nlm.nih.gov/articles/PMC4073495/ https://www.researchgate.net/publication/384855860_Religiosi...

      • zbyforgotp 6 days ago |
        Or maybe it could alter the behaviour in a positve way: https://en.m.wikipedia.org/wiki/Parasites_Lost
      • DonHopkins 6 days ago |
        >But it's also on track to be fully eradicated.

        Thanks to Jimmy Carter! (And also a guy named Donald Hopkins, who's not me.)

        https://www.cartercenter.org/about/experts/donald_hopkins.ht...

    • carlosjobim 6 days ago |
      They do and are what people in the past would call "demons".
    • TheAceOfHearts 6 days ago |
      An STD that increased human promiscuity seems like it could be really successful at spreading. I wonder if any existing STDs have evolved to do anything close to this.
      • devmor 6 days ago |
        The social stigma around being seen as "dirty" for having an STI is known to drive the infected into more risky sexual behaviors and less hygienic partners. This is why normalizing testing and treatment as everyday things are part of the public health effort.
      • phatskat 5 days ago |
        Doesn’t seem like it from the ones we know about, and I think that’s why we know about them. STI symptoms are typically unpleasant, painful, and when untreated potentially deadly. HSV for example is most contagious when a person is having an outbreak of sores, which certainly wouldn’t put most people in the mood.
    • ajuc 6 days ago |
      The parasites you should be worried about are memes (in the biological meaning - an idea that forces host to reproduce and spread it - not "a funny image" meaning).

      We already have such ideas that change human behaviour on massive scale and cause millions of deaths.

  • nik282000 6 days ago |
    I've know about horsehair worms for years and noticed a load of mantises on the road this fall but never made the connection >_<

    I wonder how much this lowers the rate of infection in the long term.

  • slaucon 6 days ago |
    In a similar vein, I always found it interesting (although frightening) that rabies cause hydrophobia. The theory is that drinking water can wash away the virus from your saliva, inhibiting its ability to spread through bites.

    It makes sense that a virus passed through saliva would evolve like this, but I just find it particularly unsettling when a pathogen can effect higher-level behaviors like drinking water (or jumping into water for mantises).

    • thaumasiotes 6 days ago |
      > I always found it interesting (although frightening) that rabies cause hydrophobia.

      Well, there are two potential senses of "hydrophobia".

      In its primary use, it means "rabies", and it's not really interesting that rabies would cause that.

      In rare cases, it could mean "fear of water", which rabies doesn't cause. Rabies causes pain when swallowing. The pain causes fear through conventional mechanisms.

      • sebtron 6 days ago |
        I have not checked the sources, but according to Wikipedia [1]:

        Rabies has also occasionally been referred to as hydrophobia ("fear of water") throughout its history. It refers to a set of symptoms in the later stages of an infection in which the person has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench their thirst. Saliva production is greatly increased, and attempts to drink, or even the intention or suggestion of drinking, may cause excruciatingly painful spasms of the muscles in the throat and larynx. Since the infected individual cannot swallow saliva and water, the virus has a much higher chance of being transmitted, because it multiplies and accumulates in the salivary glands and is transmitted through biting.

        It seems more than just "pain when swallowing".

        [1] https://en.wikipedia.org/wiki/Rabies

        • dotancohen 6 days ago |
          It does seem like your comment for the most part supports the GP comment, other than the disagreement about the definition of pain.

          For what it's worth, I see the word pain as he used it to be a better fit than the word fear, as in phobia.

          • withinboredom 6 days ago |
            Pain doesn’t cause panic.
            • kruffalon 6 days ago |
              Sure, I don't know how it works physiologically...

              But anecdata at least suggests that being in enough pain can cause panic, but it might do so indirectly so that the fear is created around the inability to think the pain will ever end or at least lessen at least a bit.

              • withinboredom 6 days ago |
                My leg has been fucked for 15 years. Sometimes it hurts so bad, I’d need narcotics to make it go away. I don’t panic when walking, I just deal with it because I need to get to my destination. If you are thirsty, you will drink through the pain. Panic is something else.
                • kruffalon 6 days ago |
                  I'm sorry that you have that pain in the first place but I'm glad that you are able to process being in pain without getting into a panic.
                • imchillyb 6 days ago |
                  Panic is a learned behavior.

                  Exposure to a stimulus is often both cause and trigger.

                  How is it that you’re an adult and still don’t know this.

                  Toddlers know this.

                  • withinboredom 6 days ago |
                    I think you've gotten fear confused with panic. Fear is indeed a learned behavior, panic is not. Panic is beyond rational thinking, it is what gets people who save drowning people dead. Panic is what gets normal humans dead when in bad situations. Panic is not learned, it saves your ass at all costs -- or gets you killed.
                    • JumpCrisscross 6 days ago |
                      > think you've gotten fear confused with panic

                      They’re just wrong. Neither panic nor fear is learned behaviour. What one panics about or fears is in part learned. But there is still a lot of instinct at play.

            • pockmarked19 6 days ago |
              It does.

              If I come into the room and stab you with a steak knife every time you drink, and sometimes even if you only think about drinking, you will definitely panic when drinking is brought up in the future, after some time.

              Not sure what's wrong with you that you cannot empathize.

              • ImPostingOnHN 6 days ago |
                Not sure that's comparable to a situation where a virus like Rabies causes someone to inherently fear water, regardless of pain.
              • withinboredom 6 days ago |
                As someone who has most definitely been in more shit than most humans on this planet, I can empathize just fine.

                As I mentioned in a sibling comment, I think you've confused fear with panic. Fear can be conditioned, panic cannot. You can panic from fear, but it is not a guaranteed thing, and often, that panic is long after the fear is gone (aka PTSD).

                Panic is an autonomic response to saving yourself at all costs. It is not something you "learn" or have "conditioned" into you, and if so, definitely not over the course of a few weeks that you have a virus; otherwise we'd all be dead from Covid and go into a panic every time we cough.

                Panic is what causes you to drown a person saving you, so that you can breathe. Panic is what causes you to over-correct and steer into a tree. Panic is what causes you to run out of your house, in the middle of winter in pajamas, because there was a spider. Panic has a cause, but it is mindless with the only goal of saving oneself. The action itself is often quite stupid-looking, in hindsight and lack of context.

                Most people have never seen a person panic, first-hand. Most people have never panicked. Today's world is largely safe, so it is easy to confuse fear with panic.

              • gosub100 6 days ago |
                Deep water doesn't cause pain, yet a significant portion of people would panic upon being dropped into it.
          • wongarsu 6 days ago |
            I feel like calling "shows panic when presented with liquids to drink" a fear of water is a perfectly fine shorthand. Even if it might not be a literal fear of all forms of water, only water you are supposed to drink
        • GuB-42 6 days ago |
          It is probably a bit of both.

          From the same Wikipedia article

          > symptoms can include slight or partial paralysis, anxiety, insomnia, confusion, agitation, abnormal behavior, paranoia, terror, and hallucinations

          There is more than just pain here. The virus changes the host behavior, making it more aggressive, so it is very possible that it also promotes a panic reaction to pain.

    • amelius 6 days ago |
      On the other hand, without saliva the virus cannot spread, and you need water to have saliva.
      • llamaimperative 6 days ago |
        Evolution has already done the math on this

        (Or more precisely, it’s already doing the math, and the current answer is that hydrophobia is the better solution [for rabies’ purposes])

        • DontchaKnowit 6 days ago |
          Really that is not how evolution works
        • amelius 6 days ago |
          The particular math used might get stuck in a local optimum ...
          • llamaimperative 6 days ago |
            Possible but unlikely in this case
        • serf 5 days ago |
          without a big genetic assay isn't it virtually impossible to know whether or not the trait (hydrophobia) persisted due to the symptom itself rather than just a correlated advantageous mutation that brought along hydrophobia as a happy coincidence?

          if we need to continue the flawed math analogy; evolution has always done pretty imprecise cocktail-napkin math, even if it has been wildly successful at it.

    • brookst 6 days ago |
      The frightening part is that it’s a cognitive effect. That’s crazy. And it opens the whole “how much of our personality is real versus controlled by microbes” question.
      • wizardforhire 6 days ago |
        Ship of Theseus now with your own mind.
      • gosub100 6 days ago |
        Imagine there was a virus or parasite that just made you feel pleasure, all the time, with no tolerance effects?

        I wonder what progress has been made in addiction medicine for meds that simply prevent the development of tolerance? If possible, it would fall under the category of harm reduction. Failing the patient to get sober, they could at least continue getting high on the same amount which might prevent their failure to function.

        • emptiestplace 6 days ago |
          I appreciate harm reduction but I think any such 'perfect' drug would lead to dehydration / starvation deaths, or at least a lot more people living on the streets.
          • brookst 5 days ago |
            See also: Infinite Jest
        • username135 6 days ago |
          Youd have to figure out how to continuously produce dopamine and serotonin, or replicate their effects from the perspective of pleasure. Pretty tall order since they have multiple purposes inside you. Trillion dollar idea though.
          • gosub100 6 days ago |
            I was more suggesting that if the receptors could be targeted (I have no idea how, just spit-balling) by another agent, then tolerance would perhaps not occur. The addict/user would still need the original drug.
            • SturgeonsLaw 6 days ago |
              Receptor downregulation plays a key role in maintaining homeostasis within normal brain function, so attempting to intefere with that process is playing a dangerous game, however it is in theory possible, since the effects of receptor activation are separate from the downregulation process, though they are linked.

              When a neuron's receptors get strongly activated, that neuron can withdraw receptors from its surface into the interior of the cell (a process call internalisation), and from there either digest the receptors (downregulation) or move the receptors back to the surface of the cell where they resume their typical function (resensitisation). Those processes are potential targets for a tolerance-mitigating drug.

              The tricky part is that they are very fundamental processes across all neurons and it would be very hard to target, say, dopaminergic receptors in the nucleus accumbens to ventral tegmental area (the "reward circuit") without also affecting neurons across the entire brain.

              The best cure for tolerance is taking a break :) easier said than done, I know.

    • DontchaKnowit 6 days ago |
      That is extremely far fetched
  • leonim 6 days ago |
    If you are interested in this subject, Carl Zimmer wrote a great book that has all sorts of examples of parasites that control their host: "Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures"

    https://www.amazon.com/Parasite-Rex-Bizarre-Dangerous-Creatu...

    • sampo 6 days ago |
      The seminal work is the 1982 book "The Extended Phenotype" by Richard Dawkins.
  • andsoitis 6 days ago |
    > infected mantises were attracted to sources with stronger horizontally polarized light.

    I wish the article provided and explanation for the mechanism.

    • toenail 6 days ago |
      They would probably have to guess, but start here https://en.wikipedia.org/wiki/Polarization_(waves)

      > Many animals are capable of perceiving some of the components of the polarization of light, e.g., linear horizontally polarized light. This is generally used for navigational purposes, since the linear polarization of sky light is always perpendicular to the direction of the sun.

      • andsoitis 6 days ago |
        I’m aware of that, thanks. What I meant is how does the worm change the mantis to have this perception when they previously didn’t.
    • undersuit 6 days ago |
      You can wear polarized sun glasses to help block the light reflected off of roads and water like when driving or boating. Seeking stronger horizontally polarized light would historically lead you to a water source. Adult horsehair worms complete their life cycle in water.
  • tonis2 6 days ago |
    Just my fantasy scenario, imagine if some kind of yeast/virus affects humans to eat so much sugar, we never need so much sugar, but there's some-kind of yeast inside us that controls us, to create and consume sugar for it.
    • rgrieselhuber 6 days ago |
      I’ve always assumed that this was sort of a known thing.
      • marcosdumay 6 days ago |
        AFAIK, it's not anything close to "known". But it's an open possibility that is being actively researched and has some supporting evidence.
        • rgrieselhuber 6 days ago |
          Depends on your epistemology, I guess.
    • lambertsimnel 6 days ago |
      > imagine if some kind of yeast/virus affects humans to eat so much sugar

      I think the gut microbiome can indeed do this.

      The episode called "Swap Out Sugar" of the BBC podcast Just One Thing explains more - the relevant section is from after 7 minutes to before 12 minutes into the episode:

      https://www.bbc.co.uk/programmes/p09by3yy/episodes/downloads...

    • devmor 6 days ago |
      As far as I am aware this is a legitimate theory and angle of study around the guy microbiome, not just a fantasy.
  • dataviz1000 6 days ago |
    > Sea turtle hatchlings have an inborn tendency to move in the brightest direction. On a natural beach, the brightest direction is most often the open view of the night sky over, and reflected by, the ocean. [0]

    Man made artificial lighting greatly affect sea turtle hatchlings also. There are several groups of volunteers who watch the eggs for hatching and will help the sea turtles make their way towards the sea.

    The volunteers use apps to coordinate watching the eggs and there is tons of data collected. Using AI / ML to help determine when the eggs will hatch or creating autonomous drones to watch the eggs and perhaps assist in corralling the hatchlings to the sea would make great PhD dissertation subjects.

    [0] https://myfwc.com/research/wildlife/sea-turtles/threats/arti...

    • Culonavirus 6 days ago |
      > Using AI

      ...

      Do people enjoy this crap being put into every fkin discussion on this site? Because I sure as hell have my tank full.

      • The28thDuck 6 days ago |
        This is an irate response to a perfectly fine comment. What about AI on HN is ruffling your feathers?
        • rad_gruchalski 5 days ago |
          That things do not require “AI”. An expert system will do just fine.
        • Culonavirus 4 days ago |
          It is an irate response. I guess when you read a 1000th "perfectly fine comment" it gets to you. I remember this site being full of interesting stuff, like really vibrant CS things, math for programmers, all kinds of new languages and frameworks and patterns and algorithms, but nowadays all of that diversity is eaten and shitted out as AI AI AI AI AI ... It's nauseating. I'm sorry I know this is a rant but damn, what the fuck happened :(
  • TrackerFF 6 days ago |
    IIRC, there's some parasite that makes the host (some species of insects) climb up plants, as high as possible, so that it can be eaten by birds and other animals.

    So that the parasite can reproduce inside the new host, and spread further.

    • doubleg72 6 days ago |
      Yes, you recall correctly.
    • dingnuts 6 days ago |
      Yes, the game and TV show The Last of Us made cordyceps a fairly well known genus
      • TeaBrain 6 days ago |
        Cordyceps are also a major plot device in the novel Cold Storage, which is being developed into a film.
      • griffzhowl 6 days ago |
        Cordyceps is a bit different in that it makes the host insect clamp down on a branch or twig until death so that when the fruiting body grows out of the host, its spores are spread through the air, where it can infect similar insects.

        What OP is talking about sounds more like the lancet liver fluke, which has a stage of its lifecycle inside an ant and a stage inside a grazing animal, so it makes an infected ant climb to the top of a grass stalk. Amazingly, the ants only do this from dusk till dawn, resuming their normal activities if they haven't been eaten by dawn. The rationale seems to be that being exposed to the hot sun during the day could quickly kill the ant along with its passenger flukes

      • gaoryrt 4 days ago |
        - Cordyceps has long been used in traditional Chinese medicine in the belief it can be used to treat diseases [0]

        I think every Chinese person has heard of it since they were kids.

        [0] https://en.wikipedia.org/wiki/Cordyceps

  • FrustratedMonky 6 days ago |
    Look at all the examples of manipulation in this thread. I have to wonder just how manipulated humans are everyday and we don't even realize it. It has become 'human nature'.