Feb 22 2013 11:00am

Your Cat is Literally Making You Crazy

Cats crazy Toxoplasma gondii publishing

See that guy up there? That’s my guy! He’s probably thinking about how much he loves me and wants to destroy me. And according to a scientist based in the Czech Republic, he’s also probably infected me with parasites that have re-routed neural responses in my brain.

He’s literally making me crazy.

An article in the March 2012 issue of Atlantic Magazine profiled the research of Jaroslav Flegr, a Czech Republic scientist who has been researching the effect that the parasitic protozoa Toxoplasma gondii has, or doesn’t have, on adults infected by the microbe.

For those who have cats and pregnant friends, T. gondii is a familiar term as the parasite commonly occurs in feline waste and has a deleterious effect on a growing fetus, with the disease caused by the parasite in some cases resulting in severe brain damage or death.

The parasite reproduces in cats but commonly hosts itself in mice, rats, humans, and birds. Although T. gondii can cause behavioral changes in smaller mammals (rats actually become oddly cat friendly), it has never seemed to cause a demonstrative effect in human behavior, and was assumed to be dormant while inside the body.

Causing behavioral changes in their hosts is a favorite pasttime for certain parasites. Flatworms hijack ant brains and turn them into easy prey so the flatworm can be ingested by larger animals. The orb spider is commonly set upon by the Polysphincta gutfreundi wasp, which infects the spider and forces it to care for the wasp’s young. Other wasps are set upon by X. vesparum, which force the wasp to withdraw from the hive and mate only with other wasps infected by the same parasite. If you’re an insect, parasites are the worst.

toxoplasma gondii cats crazy

The more developed and complex the brain, the harder the foothold for a parasite, but it isn’t unheard of for humans to succumb to microbes of that nature. The entire reason rabies causes frothing of the mouth is because the parasite that causes the disease travels in saliva.

Flegr’s reasons for looking more intently at T. gondii were personal and subjective in nature—his youth was characterized by reckless behavior and a lack of understanding as to why it was reckless, and he saw a parallel in smaller mammals and their behavior while infected with T. gondii. Such correlations aren’t science, though, so Flegr began to devise tests for his theory.

T. gondii can live anywhere but needs to return to a cat in order to reproduce, so it manipulates its host into behaviors that will lead to an encounter. In small mammals, this results in a more hyperactive manner (cats are attracted to things that move suddenly and quickly), and a self-destructive lack of fear of predators and environments that cats are found in. Flegr tested infected and non-infected humans in scenarios that demonstrated these qualities, and found these behaviors manifesting in infected humans. Further:

Flegr was especially surprised to learn, though, that the protozoan appeared to cause many sex-specific changes in personality. 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.

The findings were so bizarre that Flegr initially assumed his data must be flawed. So he tested other groups—civilian and military populations. Again, the same results.

Although Flegr had a good starting point, the idea was still a bit too touchy to present in full. (I’d like to think that this is because cats are awesome, but I am clearly biased.) Flegr didn’t have to wait long, though.

Two studies in 2011 replicated Flegr’s research and found a link between T. gondii-infected humans and traffic accidents. The hyperactivity led to a loss of focus and slower reaction times. (Read the Atlantic article for a more detailed rundown of his research and other findings.)

Another study from Michigan State University in the summer of 2012 linked T. gondii with depression and suicide attempts. The study found that people suffering from depression were seven times more likely to commit suicide if they were infected by the parasite. The lack of fear caused by the parasite seemed to be manifesting as a diminishing sense of self-preservation in humans.

While the presence of Toxoplasma gondii in the human brain doesn’t lead to the exact same effects that it does in animals (rats actually become attracted to cat urine and I can provide AMPLE anecdotal data that cat urine is repellent and obnoxious as hell) there is one conclusion that I find inescapable:

My cat has infected me with a parasite that rebuilt my brain so I will love it more.

And I do.

And I am happy here.

Chris Lough is the production manager of and is, in fact, a cat lover and does, in fact, love to run and, sadly, can’t hug every cat.

Photo by Elizabeth Kies used with permission.

Liz Bourke
1. hawkwing-lb
That's a gorgeous kitten.

Also, I think it is important to mention Scott Westerfeld's novels in connection with this post. I seem to remember T. gondii and vampirism...
Steven Halter
2. stevenhalter
It is all just part of the overall Cat Domination Plan. I welcome our cat overlords and their biological weaponry. (How could I do anything else.)
Chris Lough
3. TorChris
Thanks, Liz! His full name is Iorek Kittenson and he is enormous now, like his namesake.

Which Westerfeld novels? I've only read his Midnighters trilogy and the first Uglies book.
Liz Bourke
4. hawkwing-lb
TorChris @3:

Parasite Positive (US Peeps), I think. The parasite of the title acts like T. gondii - but it's been a while since I read it, so I could be misremembering.

(Iorek Kittenson! What a great name.)
5. oliveramy
stevenhalter @2:
I KNEW there was some other motives to their behavior!

I'm not surprised. My cat DID drive me CRAZY! She was the worst kind of mischevious. She knew how to push her limits and what punishments she could endure. (Even without the parasites she probably would have driven me bonkers.) I loved her, but she was a chore to take care of.
I'll stick to my poop-eating, foul-breathed, odorous dogs from now on :)
6. Ryan McEachern
I recall reading a few articles on this in certain animals (it was quickly followed by people saying this is a possibility for a zombie apocalypse) a while back and I find it interesting that it can affect humans as well (and regret the number of zombie apocalypse theories this will rejuvenate but oh well ...).

I definitely feel that this has a fair degree of merit to it from my point of view, I've had cats my entire life and I am quite introverted, I "lack a sense of self-preservation" (my bosses words, not my own), am suspicious to the point of paranoia, tend to ignore what other people think of me (don't really give a damn) and I tend to have a disregard for rules unless they somehow benefit me.
Cain Latrani
7. CainS.Latrani

I love my cats because they are wonderful creatures.

Yes. Wonderful creatures. That I adore. With my very soul.
Brian R
8. Mayhem
Yep, I remember reading the original Atlantic article on this last year.
It is one of those wonderful scientific discoveries I love to learn about, where the science is so completely bizarre it almost defies belief.
The parasite manipulates brain chemistry so that the host is more likely to be eaten by a cat, which puts it back into a cat gut where it can reproduce again. Yet the parasite is an incredibly small and relatively simplistic organism. Clearly it works on the older, more primitive parts of the brain, as functionality would be common across mammalian hosts.

I've definitely mentioned it a few times as a likely example of how zombies could work in reality, I know the subject has risen on Charles Stross's blog a few times too.
9. oliveramy
stevenhalter @2:
I KNEW there was some other motives to their behavior!

I'm not surprised. My cat DID drive me CRAZY! She was the worst kind of mischevious. She knew how to push her limits and what punishments she could endure. (Even without the parasites she probably would have driven me bonkers.) I loved her, but she was a chore to take care of.
I'll stick to my poop-eating, foul-breathed, odorous dogs from now on :)
10. oliveramy
Sorry, double posting. Wacky internet.
Alan Brown
11. AlanBrown
This kind of news makes me happy that I am a dog person...
Glen V
12. Ways
AlanBrown @11
Stay tuned, someday someone will discover something equally weird about dogs.

They're both pretty cool companions in my book, they just have vastly different social interactions with people.

I'm not especially worried about my cat eating me some night. :-)
13. Gerry__Quinn
"brains... need... brains... to... feed... my... kitty..."
Kim B
14. Amaranthine
This is really interesting and disturbing. Oh well... I think I'll go cuddle my kitty now.
15. Megaera
Oddly enough, I am female, have had cats most of my life, and I exhibit the traits T. gondii is supposed to manifest in men. Twilight Zone theme]
16. Dannyboy1111111
My exposure to cat urine seems to have made me passive towards other people. I seem not to care when they cut into line in front of me and I seem to be less inclined to argue with them. Its wierd. I think it has something to do with this parasite. People take advantage of me now whereas in the past I was pretty assertive, now I dont seem to care. I have several cats and even though I keep the areas fairly clean I have had my share of enhaling a fair amount of cat urine.

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