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Do Brain Parasites Make Me Love My Cat?

by Alison Hudson

August 25, 2014

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Donate I am the happy roommate of a precocious cat named Olivia. I protect her from harm, I feed her decent cat chow, and I let her sleep next to me at night if she wants to. I am, in other words, a responsible cat owner, and Olivia is a friendly and well-adjusted animal. I would like to think that my care and affection for her is a refletion of my better nature as a human being.

So why is it that people want to tell me that I'm infected with a brain parasite?

Here's a typical example, from the article "12 Reasons Cats Actually Suck -- Scientifically." [The other 11 are equally awful, but I'll deal with them some other time.] From the article:
Your brain is home to millions of protozoa, but one in particular, called Toxoplasma gondii, manipulates your behavior to force you to like cats.

This parasite, which lives in 30 to 50 percent of the world’s human brains, can only reproduce in the digestive tracts of cats. And, like many living things, it wants to continue surviving, so it has to continue reproducing. But if it lives in human brains, how can it reproduce? Enter cats.

Scientists studied the behavior of T. gondii in the brain of a rodent, an animal normally petrified by cats, and uncovered extraordinary results.

T. gondii manipulated a rodent’s brain to remove the rodent’s fear of cats, slow the rodent’s reaction time, and made the rodent attracted to the smell of cat piss. Now, the newly-brave, manipulated rat thinks it can befriend its mortal enemy, and it can’t. The rat still gets eaten.
With the claim "Scientifically" in the title, I figure author Alexia La Fana's evidence should stand up to a little scrutiny, right? Well, considering her stated motivation for writing the article is that "People who love cats and display their love for said cats on social media are really, really annoying," my hopes aren't high. But I shall soldier on regardless.

La Fana is right about one thing: According to the CDC "the only known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives)." So yes, infection originates with cats. It doesn't stop there, however, and cat-to-human infection is uncommon; instead, most human infections happen through the ingesting of contaminated meat. While T. gondii begins in cats, it is very good at spreading to other host animals, including livestock.

The claim about brain parasites making me love my cat is rooted in studies that looked at how T. gondii affects the behavior of rats. And it was believed for a long time that infection made rats more docile or less fearful of cats. But in 2007, a more specific study found that what the parasite actually does is reduce the rat's fear of cat urine odors and possibly even make the rat seek the odor out. In other words, it stops them from running away when they smell a cat nearby. Note that nothing aboutT. gondii "forces" the rat to "like cats" or "slow[ed] the rat's reaction time"; infected rats displayed normal fear responses in non-cat-urine situations. It basically suppresses their desire to flee when the cat gets near.

Now the last time I cleaned my cat's litter box, I can tell you I was anything but attracted to the smell. In fact, the smell of cat urine is one of the worst parts of owning a cat. That's why my cat's litterbox is in the basement! So I'm not showing the one effect that we know T. gondii has -- attraction to cat urine -- and I'm guilty of a thing -- affection for my cat -- that isn't actually something that the parasite is known to cause. My experience, in other words, lines up with the evidence of science and contradicts the popular claim.

This also belies a larger claim, that T. gondii is responsible for so-called "crazy cat lady syndrome." Nevermind for a moment that the "crazy cat lady" is nothing more than an offensive stereotype of older unmarried women; just consider, again, what T. gondii actually does. And what it doesn't do is cause an obsession with collecting cats.

And besides, if I were infected with T. gondii, cat urine attraction would be the least of my worries. According to the CDC, T. gondii is "considered to be a leading cause of death attributed to foodborne illness in the United States." Once the T. gondii gets out of the cat it spreads into other animals that come on contact with it -- mice and birds, for example, which may then come into contact with, say, cow feed (yes, that means they poop on the feed). Humans, especially in North America, are far more likely to pick up T. gondii from an undercooked steak, even if they do live in a house without cats.

But there's a larger point here as well, beyond the science: why does a brain parasite need to be invoked to explain a fondness for cats? Humans have an affinity for lots of animals. We invite all manner of furry domesticated creatures into our homes -- dogs, cats, hamsters, guinnea pigs, even ferrets -- not to mention all the non-furry ones -- fish, birds, lizards, snakes, and even spiders. You're telling me I need a brain parasite to love my cat, but that the guy down the street who likes to nuzzle with the pedipalps of his tarantula is parasite-free? That feels a lot like special pleading to me.

I have no problem agreeing with La Fana that the Internet's cat fixation can sometimes get annoying; but it's no more annoying than any other stupid thing the Internet gets fixated on. To single out cats as being different from the norm of pet ownership, just because they annoy her, suggests that cats are somehow unworthy of the same affection one might give to a chihuahua or canary. And that just doesn't make sense, logically or emotionally.

I think I will be posting at least one new picture of my little parasite host every day this week over at my Twitter feed, just to annoy Alexia La Fana and anyone else out there who thinks I'm being controlled by a brain parasite. If you want to see them, you can follow me @Ariamythe.

by Alison Hudson

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