Sara Pascoe

A Bug that Makes Men Jerks and Women Nicer? Earthdate 2017.77

I know, I know – sounds like I’m making this up. But I’m not. There’s this microscopic bug called Toxoplasma Gondii, a single celled parasite that lives in a third (!) of all humanity, where it’s mostly harmless. But if it wakes up it, it can do some pretty weird stuff, like eat out our brains. Yum.

But before I get to explaining how it messes with us humans, and how to avoid it, you’ve got to hear this wild ride Toxoplasma gondii (T. gondii) takes between cats and mice.

You see, in order to reproduce, T. gondii must get into a cat’s stomach. It can live in other stages of its little one-celled life in most if not all warm-blooded animals including whales. But to reproduce, the biological imperative of us all, it absolutely must get into a cat’s stomach. And one way to do that it so be part of a rodent treat. Double yum.

Now here’s the strange part, once it gets into mice or rats, which it does when the little critter has ingested it from contaminated plants, water or soil, it changes the rodent’s behavior forever. It makes the rat or mouse not only bolder in general, it makes them like the smell of cat pee. Yes, eau du chat has become their favorite scent. And the rats can also show sexual arousal to the smell of cat pee—not normal. It does this by altering certain parts of their brains, including their amygdalae which regulates fear and rage in all of us.

‘Eau du chat has become their favorite scent.’

T. gondii also makes chimps attracted to the smell of leopards (their urine in particular) whereas they are usually, and understandably repelled by these natural predators who regularly snack on chimp. And this effect is strangely specific. The infected chimps were not attracted to lion or tiger pee, and they are not natural predators.

Enough about everyone else, you say, what does this have to do with us? Well, first of all, you can reduce your chances of infection by avoiding undercooked meat, unwashed produce, contaminated water, and cat poo.

This is why pregnant women are warned against cleaning the litter box, and certainly not without gloves. They should also where gloves while gardening and wash their hands thoroughly after any of these activities. T. gondii can spread from the mother to the infant where it can cause miscarriage, or long-term and serious birth defects, as well as more subtle problems for the kid later in life. All good things to avoid.

For the most part, if your immune system is on the job, and not compromised by chemotherapy or HIV for example, then you wouldn’t even know you’re harboring this creepy one-celled critter. But it can show up with flu-like symptoms, and for those with reduced immune functioning it can come alive from its dormant state and infest your brain and muscles. There are treatments including antibiotics and anti-malarial drugs.

Now here’s the really interesting part for me. There are a number of studies showing that the mostly dormant infection does change people. It looks like it makes men more likely to break rules, more suspicious, dogmatic, and more likely to act very quickly. Some studies link more right-leaning politics to T. gondii infection. Other studies have linked it to constant rage and aggression, increased rate of car accidents. Some research shows infected men to have an increased interest in aggressive or violent sexual acts, from bondage to rape. Yet women carrying the bug have been found to be warmer and caring, outgoing, conscientious, persistent and moralistic.

So, maybe these behaviors that we tend to think of as coming from a combination of our history, our experiences and our personality come down to a parasite. A measly one-celled invader. Or at least it’s a factor. Who knows what links science will reveal in the future between the rest of nature, and us.