Parasites That Can Control Insect Minds

The Episiarch · Post by **The Episiarch** » 2005-09-05 10:16pm

Dennis Toy wrote:"WE Seek peace-ful co-existance" ( A cookie for anyone who gets the reference )

I perfer headcrabs myself. I never thought parasites that controlled the brains of insects existed. I knew of insects who grew inside other incests and bursted out when matured.
( This is where Ridley scott claimed the idea for Alien came from )

Never thought SD.net would be discussing what I've been doing for my postgrad research these last two years! And coincidentally I just gave my PhD proposal talk two hours ago!
Well, actually, that's the "ordinary" bit, the parasitoid wasp you are thinking of actually coerce its host into protecting it. When they start coming out of the host and form cocoons, the caterpillar stays alive for a little while longer and actually spins a protective web over the cocoons and sit on it, guarding them against predators and hyperparasitoid (yes, there are parasites that parasitised other parasites) until they hatch.

Just briefly, the worm that give those snails the funky pulsating eyestalks belongs to the Leucochloridium genus, the one that cause ants to crawl to the tip of grass blades and hang out for a rendezvous with a sheep is Dicrocoelium dendriticum, there's another fluke with the long and somewhat embarassing species name of Microphallus papillorobustus that changes the phototaxis and geotaxis behaviour of little crustaceans so they're more likely to be eaten by a bird - this parasite's next host and the list is so damn long that I don't think I'll have time to go into.

As for whether humans can be affected...there's a little unicellular parasite call Toxoplasma gondii that infect cats and rats. When it gets into a rat, it goes into the brain and cause it to be less cautious and show less inhibition about hang out in area that has been doused with cat urine. This little parasite sometimes end accidentally end up in humans...there was some in New Scientist the year before about people who have latent Toxoplasma infection having personality changes and being more likely to get into car accidents, but I don't have time to go into that right now....

As a personal plug, I'm actually doing my PhD on a parasite that accumulates in the foot of a cockle, inhibiting its ability to burrow into the sediment, causing it remain on the surface of the mudflat where it can easily be picked off by birds like oystercatchers, which are the parasite's next host.

Yep, parasites are always behind the scenes...everywhere! Not to get you paranoid or anything...

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Dennis Toy · Post by **Dennis Toy** » 2005-09-06 01:40am

Of course before we all "paranoid" here we remember that insect minds are really simple and controlling a more complex creature (like humans) is a lot more difficult.
_________________

tell that to those people who were horribly zombified by the headcrabs

spikenigma · Post by **spikenigma** » 2005-09-06 05:48am

The Episiarch wrote:As for whether humans can be affected...there's a little unicellular parasite call Toxoplasma gondii that infect cats and rats. When it gets into a rat, it goes into the brain and cause it to be less cautious and show less inhibition about hang out in area that has been doused with cat urine. This little parasite sometimes end accidentally end up in humans...there was some in New Scientist the year before about people who have latent Toxoplasma infection having personality changes and being more likely to get into car accidents, but I don't have time to go into that right now....

you can also get Toxoplasma gondii from improperly cooked meat - which is why a higher percentage of people in france have it

question - how would a human get rid of the Toxoplasma gondii parasite?

Rye · Post by **Rye** » 2005-09-06 07:30am

spikenigma wrote:question - how would a human get rid of the Toxoplasma gondii parasite?

You can't, they're tiny and live in your brain, there is no treatment. Their impact on human behaviour doesn't seem to be severe enough to warrant open head surgery or poisoning anyway.

The Episiarch · Post by **The Episiarch** » 2005-09-06 08:32am

spikenigma wrote:
The Episiarch wrote:As for whether humans can be affected...there's a little unicellular parasite call Toxoplasma gondii that infect cats and rats. When it gets into a rat, it goes into the brain and cause it to be less cautious and show less inhibition about hang out in area that has been doused with cat urine. This little parasite sometimes end accidentally end up in humans...there was some in New Scientist the year before about people who have latent Toxoplasma infection having personality changes and being more likely to get into car accidents, but I don't have time to go into that right now....
you can also get Toxoplasma gondii from improperly cooked meat - which is why a higher percentage of people in france have it

question - how would a human get rid of the Toxoplasma gondii parasite?

I'm not sure if you get it from undercooked meat (there's a lot you can get from undercooked meat, but I'm not sure if good ol' Toxoplasma is one of them). You're more likely to get it from ingesting stuff that has been contaminated by cat shit, i.e: to all the cat owners, myself included; careful when you are handling soiled kitty litter. The two host of the Toxoplasma gondii life cycle are cats and rats, the cat shits near grains or other rat food, rat picks it up by accidentally ingest it, goes a bit crazy, gets eaten by a cat, life cycle complete.

That's probably where the old wives' tale about pregnant women shouldn't be near cats comes from, if a pregnant woman gets infected with Toxo, the parasite can get passed into the fetus and causes neurological defect in the newborn.

Except in that case, Toxoplasma gondii is considered to be non-pathological in humans apart from those who have immuno-suppressed diseases, that's why no one sees it as being a big deal and worth making drugs to treat. As for the personality-change thing, it has only been found in the past ten years and more experiments need to be done just how much latent-Toxoplasma infect affects the behaviour of humans.

Either way, its maladaptive for the parasite to change the human host's behaviour, it's not going to help it end up in a cat which is where it needs to go. Just that the parasite acts as if it has found itself in its usual intermediate host (a rodent) and is "programmed" to do certain things to change the host's behaviour (e.g: muck around with the neurotransmitter chemicals)