I was talking to K and she pointed out that I missed the point of this whole “internet” thing. Apparently the goal of writing for the internet is not to sound like a pedantic stuff-bucket? This is something I hadn’t yet realized – I mostly use the internet to watch videos of Louis Scott Vargas playing Magic cards, since I don’t have much time to play myself these days.
So she told me, you should write this next thing as though you’re just writing an email to somebody, telling them some weird stuff about toxoplasma. And, yeah, put in references. But you’re not writing a critical essay here. Even if you were, I’m not sure you’d want to sound so stiff.
What can I say: I’m just a real formal dude? But here goes: wacky information about toxoplasma. Which I was researching as part of a general interest in mind control – the book has a fair bit about identity and how your brain works, so the idea that a parasite can exert a big influence on (mouse, documented in controlled studies, and human, possibly, suggested by observational studies comparing otherwise similar people who are and are not infected) the mammalian brain seemed pretty wild.
So, what does toxoplamsa do?
Well, fine: I guess it might be worthwhile to mention briefly what toxoplasma is. Parasite. Forms cysts in the brain. Lives part of its life cycle in a variety of mammals, including mice and humans, and part of its life cycle only in cat gut: it can’t complete the whole cycle without getting into a cat. It can also be transmitted from mothers to unborn children, and probably from males to females during sex.
In rats, toxoplasma makes its host less afraid of cat smell. If you compare the amount of time spent exploring a sandy maze dribbled with rabbit urine to a sandy maze dribbled with cat urine, a normal rat will spend most of its time in the rabbit area. A rat with a chronic toxoplasma infection will hang out in the cat section.
So that seems normal enough, right? The parasite has to get into cats, it makes rats not fear cats. Or at least stop avoiding cat smells. Which in theory should make the rat more likely to be gobbled up.
But it’s not just a change in response to cat smells. Rats infected with toxoplasma behave more recklessly in general – one test you can use is “open arm exploration,” which is less grisly than it might sound. Build a play space with a roof over some parts and no roof over others, and monitor the fraction of time that the rat spends in the open area. Theoretically being out in the open should make the rat feel scared, so it won’t do it much. A toxoplasma-infected rat will hang out in the open more. Why? Well, one possible explanation is that the parasite increases dopamine production in the brain – this is speculation, but perhaps the extra dopamine makes exploration more pleasurable, and therefore worth doing even when there are risks involved.
And here’s one last set of bonus curiosities – wacky things to consider for a parasite that seems to be sexually transmitted (which I guess I didn’t actually explain above. Sexual transmission seems to happen in humans, but hasn’t been experimentally verified because that would be evil, and definitely can occur in dogs, goats, sheep… ). Would it be reasonable to expect that the parasite would increase a male carrier’s chance of sexual coupling? Perhaps, right? But this is difficult (but not impossible, obviously) to assess – I’m no expert in rodent attractiveness. Are you?
The goofy thing is, toxoplasma can infect a wide variety of mammals. Not just rats. And mammals are pretty similar to each other. Toxoplasma presumably only evolved to control rats, because any particular toxoplasma gene requires ingestion by a cat in order to propagate. But some of the mechanisms that toxoplasma evolved in order to manipulate rats may well function in other species: it seems to have an effect on the perception of cat urine smell in humans. And infected human males are taller and reputedly better-looking than uninfected males, presumably due to higher testosterone levels. Perhaps the same mechanism makes male rats appear more alluring?
Still, toxoplasmosis is a disease. People can get sick and die from it, especially babies and AIDS patients. But other than that whole “risk of death” thing, problematic, sure, the next biggest negative consequence of toxoplasma infection is that it seems to increase your chances of being eaten by a cat. Especially if you are a rat. Slower reaction times, sunnier outlook on life with that increased dopamine, less risk aversion. Perhaps a bit more fooling around, although that’s not really related to being eaten, that might be an evolved consequence of the potential for sexual transmission of the infection.
But, weighing all of that, there is a chance that you, if you are a human male reading this, unlikely to be eaten by a cat, might want to be infected by toxoplasma. Personally I don’t – I find the whole parasitic mind control thing creepy – but it’s not as though there are zero traits that could be considered positive externalities. If you are a human female reading this, then, yes, there is a chance that the infection could be passed to a fetus if you ever happen to want biological children. But there is also observational data suggesting that toxoplasma infection increases female intelligence (it is suggested that the infection makes men less intelligent – more daring, more sexually alluring… dumber. Can’t have everything, can you?).
Anyway, that’s some information about toxoplasma. What a wacky little protist.