Constitutional Health Network:
How a Common Pet-Borne Parasite Could Be Affecting Your Brain

It’s a running joke that cats are really aliens bent on taking over the world and it turns out, the idea may not be so far off the mark. We’ve long known that cats play host to a parasite which can infect humans - his is why pregnant women are exempt from emptying the litter box. But while scientists thought that the parasite goes dormant once it infects humans, recent research shows that this isn’t the case at all. Not only does the beast not go dormant, it lives in your brain and exerts a sort of mind control.

Mind-control gone wrong

Toxoplasmosis gondii is a parasite that normally infects cats. It’s famous among scientists for its novel method of spreading itself from one cat to another - it hijacks rats and changes their behavior so that they’re more likely to get eaten.

That’s pretty creepy.

Toxo leaves the host cat via cat poo. A rat comes in contact with it through contaminated dirt, food, or whatever, and gets infected.  This is where it gets really spooky. Once Toxo infects the rat it makes its way to the brain, where it sets up a tiny chemical factory producing neurotransmitters. These chemicals radically change the rat’s behavior.

The rat becomes fearless. It don’t avoid places where it’s likely to get eaten. Instead, it seeks them out. It also becomes more active, which makes it more likely to be noticed by predators. But most spookily of all, it loses its fear of cats and becomes attracted to the smell of cat pee. This ensures it will go places where there are cats. In short, the parasite changes the rat from a sneaky, quiet shadow-dweller who avoids cats like the plague into a tap-dancing performer who looks for places that smell like cats and screams, “EAT ME!”

Ok, that IS creepy, but I’m not a rat

That’s ok. Toxoplasmosis also infects humans. We usually come into contact with it through litter boxes, contaminated water, or undercooked meat. Unless you’re pregnant, it doesn’t usually cause any obvious problems. For pregnant women,though, it's dangerous. It can cause miscarriages, and if the unborn baby gets infected it can cause brain damage. It can also cause dementia in people with weakened immune systems, like those with end-stage AIDS. But till recently, scientists thought everyone else was safe.

Then along came Jaroslav Flegr.

Flegr is an evolutionary biologist at the University of Prague in Czechoslovakia. For years, he’s suspected that Toxo might have more of an effect on humans than we give credit for. He believes it’s a factor in a lot of self-destructive behaviors. According to Flegr, it contributes to car crashes, suicides, and even schizophrenia. And now he has the science to back that up.

His research, and now that of several others, shows that Toxo has many of the same effects on us that it does on rats. It makes us fearless in situations where we should be afraid. It slows our reaction times down, so we’re less able to respond to threats. We're also slower to notice the car in front of us slamming on their brakes. In fact, Flegr found that infected people were two-and-a-half times more likely to be in car accidents that those who without the parasite. The infected are also more likely to be clumsy and uncoordinated.

Toxo affects our personalities. Infected people are more likely to be plagued by guilt. They’re less likely to seek out new experiences. Infected men tend to be more introverted, suspicious, and indifferent to other people’s opinions. They’re more likely to break rules. For unknown reasons, they’re inclined to dress like slobs, in crumpled old clothes.

They are also, interestingly, less put off by the odor of cat pee than uninfected men.

Infected women, on the other hand, display just the opposite set of behaviors. They’re more likely to be outgoing, trusting, and rule-abiding than uninfected women. They also find infected men more attractive than uninfected men, and are extremely offended by the smell of cat pee.

All these findings are bizarre, but not very useful. Nor are they the most shocking.

Your cat may be driving you crazy - literally

Some of the most disturbing findings of the current research are psychiatric. Toxo infection is associated with higher rates of suicide, and it actually makes us experience some situations which should be frightening as sexually arousing instead. For rats, this means that the smell of cat pee goes from being frightening to being sexy. Humans are more complex than rats, and our fears are more complex, but the effect is much the same.

Research also very strongly suggests that Toxo can trigger schizophrenia in susceptible people. Shrinkage in the cerebral cortex area of the brain is common in schizophrenics, and Flegr’s research shows that patients with this shrinkage invariably test positive for Toxo.  In fact, adding a common antipsychotic medicine for schizophrenia to a petri dish full of Toxo stops it from growing. The link becomes even more likely when you consider that schizophrenia basically didn’t exist till the end of the 18th century - when people started keeping cats as pets.

So…does that mean I should get rid of my cat?

No. Indoor cats don’t carry the parasite. And outdoor cats only shed it for three weeks out of their entire lives. This happens when they’re very young, usually when they’ve just begun hunting. If you have an adult outdoor cat, you may very well already be infected.  Since there’s no cure, there’s not a lot you can do if you are.

The best defense, rather than avoiding cats, is to simply practice good kitchen hygiene. Make sure your counters and tables are wiped clean often. Scrub your vegetables, cook your meat well, and avoid unpurified water. If you’re not a fan of well-done meat, freezing it before cooking will also kill Toxo.

The most important thing is the same as it always has been - if you’re pregnant, stay away from the cat box, and wash your hands well after changing it even if you’re not.

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