Toxoplasmosis: The Disease That Makes You Like Cats

What can cause schizophrenia, depression, and skin lesions, and makes you like cats? Believe it or not, a parasite carried by cats can actually turn you into a cat person!

You may be familiar with toxoplasmosis as the reason why pregnant women and HIV-positive people ar exempted from litter box scooping duty.

Toxoplasmosis is also why most cities have banned flushable clumping cat litter, because it is a serious danger to marine mammals like seals and otters. Toxoplasmosis is caused by a protozoan named Toxoplasma gondii, a microscopic parasite which has wide-ranging effects on its host body.

The symptoms of a toxoplasmosis infection are, for most of us, extremely subtle. The acute phase typically presents like a low-grade cold or flu (including fatigue and swollen glands) which lasts about a month. After that, the infection goes into the latent phase, when no normal symptoms are observed.

Up to a third of all people in the world carry the T. gondii parasite. You can get it from contact with infected raw meat, or with infected cat feces. Cats themselves usually pick it up either from their mothers, or by eating infected meat.

The list of other effects of toxoplasmosis is a long and strange list indeed. It includes:

1. Male births.

There is a strong correlation between toxoplasmosis and the probability of having a male baby. This effect is significant: mothers with toxoplasmosis give birth to 260 boys for every 100 girls. Why T. gondii should prefer boys is a complete mystery.

2. Cat love.

Mice and rats which are infected with toxoplasmosis not only lose their fear of cats - they are driven to seek out the smell of cat urine. The benefit to the parasite is obvious: if you have to move from a mouse into a cat as a new host, what better way to accomplish the move than by making the mouse a cat-lover?

But weirdly, this effect has also been observed in people. In one long-range study, people who disliked or were neutral on the topic of cats were surveyed years later. Those who had been infected with toxoplasmosis in the intervening years showed a marked increase in their love for cats, compared to those who didn't have toxoplasmosis.

3. Mental changes.

People infected with toxoplasmosis show a decrease in "novelty seeking behavior," and slower reaction times.

Even weirder? The changes are different for men versus women. Men become more jealous, and pay less heed to rules. Whereas women become more moral, conscientious, and maternal.

It makes sense that a cat would want to infect women with something that makes them more maternal (and therefore more likely to pamper a cat in the manner to which it has become accustomed). But why would cats want men to be more jealous?

4. Car accidents.

People infected with toxoplasmosis are 2.5 times more likely to have a car accident, compared to uninfected people. Could the risky behavior account for this? Perhaps as a side effect of the mechanism that makes mice less wary of cats, people become more likely to run red lights and not wear a seatbelt. It could also be due to the decreased reaction time observed in people with toxoplasmosis.

Photo credit: Flickr/buildscharacter

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Anonymous's picture


yeah, so this really creeps me out, but it makes sense - why else would anyone like cats?


Because they are soft and pretty and they purr and have whiskers and also because THEY ARE CONTROLLING MY MINDDDD!!!


Anonymous's picture


my friend sent me this so i clicked on the link...
i then saw the cat picture and started to giggle, i continued to read the text and freaked out a little bit but then i scrolled back up the page and saw the cat again... now i cant stop grinning like an idiot... i need help D:


Marius's picture


If one third of the earth's population are carriers, and they are 2,3 times as likely to have boys, why aren't there more men? There should be twice as many men as women, no?


Only half of the carriers are women (thus, 1/6th the world's population, or 1.15 billion people). Out of that 1.15 billion women, let's be sloppy with the numbers and say only 1/3rd are of childbearing age (or 383 million). 

And although male births are more common among women with toxoplasmosis, toxoplasmosis is also a huge contributing factor to stillbirths, spontaneous abortions, and infant deaths. If those 383 million women are having 2.6 male babies for every 1 female baby, a large percentage of those babies will die either in utero or shortly after birth.


Pal's picture


As babies anyway. There are more male children born, possibly due to our society preferring boys over girls they do seek out ways to make it more conducive for male sperm to beat out female sperm with methods that give it an advantage. However, as males grow they tend to die off sooner, either due to their health habits or high risk occupations so it ends up there are more females. And besides this article is only addressing the majority of men who are carriers of this disease, not the overall human population.


Patti's picture


I'd love to see a list of sources. I'd be really interested in reading the studies you've mentioned in your article.