Wondering if there’s a difference between cat people and dog people? The answer may scare you.
Science has responded to this age old question and the results are, in a word, bizarre.
The difference all comes down to a freaky little parasite called Toxoplasma gondii. It’s carried by cats, and it exercises a unique form of mind control on those it infects. And yes, it infects humans.
If you’re anything like me, you remember The Atlantic‘s brilliant tale of this pernicious parasite—“How Your Cat Is Making You Crazy”—and you’ve been waiting with bated breath for more news. Well, here it is, and it’s as strange as ever.
The New York Times reports that this rapidly spreading parasite is among the most successful of its kind in history, infecting as much as half of the world’s population. Part of the key to its success: it can infect or be transmitted by nearly any warm-blooded animal on the planet. But cats hold a special role in its life cycle, for it can only sexually reproduce inside feline intestines.
I’ll pause for a moment so you can set down your sandwich.
Yes, cats—and not dogs, those kind-hearted canines—have the exclusive privilege of hosting this parasite. And thus cat parents may be at a greater risk of exposure. But what’s this about “mind control”?
Studies have shown that Toxoplasma gondii changes the behavior of the rodents it infects in startling ways, increasing the likelihood that they’ll be killed and consumed by cats. See, rodents have understandably evolved to fear and avoid scents associated with cats. But rats infected with Toxoplasma gondii no longer fear those scents—some are even drawn to them, offering themselves up and thus continuing the parasite’s lifecycle.
In other words, the parasite works in tandem with cats, providing them with easy prey by manipulating the minds of their food sources. This works to the advantage of the parasite, which needs cats for its reproductive success. Once it infects a new party, it must return to a cat to propagate. If it can convince a rat to happily offer himself up as feline food, then voila!
The parasite infects animals through a complex process of rerouting neural pathways in the infected party’s brain. As the New York Times explains, “Think of the genes in a host as keys on a piano. Toxoplasma, it seems, simply plays some of the keys differently to produce a new melody.” The Atlantic goes even further, writing: “The organism rewires circuits in parts of the brain that deal with such primal emotions as fear, anxiety, and sexual arousal.”
But what about humans, right? We aren’t exactly food sources for cats.
Implications for animal lovers
Are humans still vulnerable to this parasite? The Atlantic explains contemporary scientific thinking on the subject:
“Little, however, was known about how the latent infection might influence humans, because we and other large mammals were widely presumed to be accidental hosts, or, as scientists are fond of putting it, a “dead end” for the parasite. But even if we were never part of the parasite’s life cycle, […] mammals from mouse to man share the vast majority of their genes, so we might, in a case of mistaken identity, still be vulnerable to manipulations by the parasite.”
Worried about infection? You’re at a greater risk if you clean a litter box regularly, as exposure to cat feces could result in transmission of the parasite. Clean the litter box daily—the parasite isn’t infectious for the first 1-5 days, so get that kitty poo out of the house. You’ve heard that pregnant women shouldn’t clean litter boxes? Yep, this is the parasite behind that red alert. It can cause a disease, toxoplasmosis, that’s especially dangerous for pregnant women and people with weakened immune systems.
But before you panic, if you do become infected—and about one in ten Americans do—it’s unlikely you’ll notice. In healthy children and adults, it typically causes mild flu-like symptoms that quickly subside.
Still, the parasite remains—and the jury is still out on how exactly it’s impacting the behaviors of the humans it infects. Recent studies suggest that the parasite’s mind control may extend beyond the rodent family. And the results are…weird. As The Atlantic reports on one such study:
“Compared with uninfected men, males who had the parasite were more introverted, suspicious, oblivious to other people’s opinions of them, and inclined to disregard rules. Infected women, on the other hand, presented in exactly the opposite way: they were more outgoing, trusting, image-conscious, and rule-abiding than uninfected women.”
There’s further indication that the infection could increase self-harm in some women (JAMA Psychiatry), and that the parasite may impact dopamine and testosterone in humans, resulting in changes in behavior (Oxford Journals). But the truth is, any scientifically proven effects on human personalities due to this parasite are subtle. Invasion of the Body Snatchers this is not.
All “evil kitty” jokes aside, a lot of us—myself included—have room in our hearts for both dogs and cats. I’m just saying, if you’re a dog lover who’s also a cat lover (or a dog lover who loves a cat lover), keep an eye on you and your pal’s behavior. You wouldn’t want to follow in the rat’s footsteps and become easy prey…