Toxoplasma (cat-poo parasite) hypnotizes rats by making them horny for cat pee


Tobias has a creepy-fun blog post up today about Toxoplasma gondii, a parasite that causes rats to become attracted to cats, which can adversely affect the development of a baby within a pregnant women's body. The post digs into Stanford scientist Dr. Robert Sopalsky's research around how "toxo" changes human behavior, but this snippet about how it "hijacks the sexual reward pathway" in rats' minds is pure gold.

Once in the rat, Toxo's goal is to then be eaten by a cat so it can be fruitful and multiply, but as I mentioned, this can only take place in the cat's gut. Toxo's goal is to get the rat eaten by a cat. Toxo could get the desired effect through a whole sort of seemingly obvious ways; e.g., Make the rat hard to run so it is easier for a cat to catch it. Instead it takes a far more interesting approach: Toxo generates cysts in the brain of the rat. These cysts take over the fear center of the brain, but specifically the fear of predators. Common fear sources for rodents (e.g., bright lights, open spaces, etc.) still operate perfectly well in an infected rat, but now they are no longer afraid of cat piss. That alone would be cool enough, but Toxo takes it one step further. When Toxo is going about futzing with the fear center of the brain it also goes into the sexual excitement part of the brain. It hijacks the incoming Fear of Cat Piss™ and instead diverts the signal to the Barry White™ center of the brain.

"Somehow, this damn parasite knows how to make cat urine smell sexually arousing to rodents, and they go and check it out. Totally amazing." - Dr. Sapolsky

The rat is now sexually attracted to cat piss! (This is a fetish that gets you eaten by your predator and rats clearly do not have any safe words with cats.)

Now, this part blew my non-rat mind: Sapolsky says motorcyclists have a high probability of being infected with Toxo. Read the post to unpack that part.

Guided by Parasites: Toxoplasma Modified Humans

More about Sapolsky's research on


  1. I still think that brain-altering parasites might play some role in “crazy cat lady” syndrome.

    1. I agree. Some who make fun of them have noted that they tend to be unmarried (or widowed, or divorced) middle-aged ladies who do not have a sexual partner. I don’t mean to be cruel or to stereotype them, but I seriously wonder if the parasite’s impact on female mammals might have something to do with that noted generalization.

  2. For everyone who digs this I’d recommend the Radiolab podcast very highly. Just tremendously interesting stories related to scientific ideas.

  3. there are a lot of parasites that affect host behavior. many humans have liver flukes, and if you read about what they cause it is frightening.

    i love reading studies in this field, so many fascinating examples.

  4. Daniel Kahn & The Painted Bird did a song called ‘Parasites’ on toxoplasma gondii and other parasitic organisms.

  5. Interesting study of Dr. Sapolsky, Neuroinfection by toxoplasma in humans keeps latent in form of cysts after acute infection (with neurologic symptoms)unless immunosuppresion happens (immunodeficiencies such as AIDS or malignancies), rupture of cysts results in disease reactivation, including encephalitis or disseminated toxoplasmosis.

    I hope nobody starts treating post-traumatic syndrome with toxoplasma gondii going directly to amygdala ==> JOKE

  6. Sapolsky says motorcyclists have a high probability of being infected with Toxo.

    @Xeni – Maybe my understanding of what he was saying was different then yours, but my understanding was that people that died in motorcycle accidents were more likely to be infected by toxo, not that people that chose motorcycles are more likely to be infected. He says this right after he talks about two independent studies that show that toxo infected people are more likely to speed and get into accidents in cars.

    In other words toxo infected people are more likely to speed and be unsafe in their vehicle of choice and get into accidents, not necessarily that people who choose motorcycles are more likely to be infected. Toxo infected motorcyclists are more likely to be in fatal accidents then non-toxo infected motorcyclists.

    Granted there may or may not be a correlation between choosing a less safe vehicle, but I don’t think that is what he was stating/implying, imho.

  7. this post needed a “not safe for hypochondriacs” (nsfh) warning
    i wish i could afford a brain scan
    something is obviously wrong with it
    and i need a liver scan for flukes

    1. Get in line, lewis. Not to mention a comment thread on a recent BB post caused me to go and read “The Hot Zone”. Can’t sleep, ebola will eat me.

      1. There are so many topics Boing Boing covers that stress me out. Crazy cat parasites, tongue x-rays, crazy chemicals in soy burgers, terrifying diseases, etc.

        Luckily, my disgustingly short attention span means that I can often get on with my life after I’ve forgotten. Whew!

  8. Motorcycles are inherently greater risks and tend to attract a certain type of personality. Maybe people who are infected and so seek greater risks would be drawn to motorcycles in the first place. Obviously they only tested people who died in accidents. They’d also have to have living riders to test to confirm this.

  9. This is a good caution against flushable cat litter. This parasite is scary hard to kill and it does not die even in our normal water treatment processes.
    Please don’t flush your cat litter down the toilet.

  10. I read a Cracked article (scientific reasons zombies could actually happen) that mentioned this before. One points was along the lines of the virus mutating, passing to us humans, and resulting in a rage virus a la 28 days later.

  11. I’ve seen a few of Dr Sapolsky’s lectures and they’re always great.
    Someone’s cellphone was buzzing in the beginning, I thought it was mine for ages.

    By the way, you spelled Sapolsky wrong. I’m a stickler.

  12. The Stuff You Should Know podcast on how stuff works, did a great episode on this. Parasites are scary cool.

  13. This study showed people involved in traffic accidents (driving or being hit) were twice as likely to have latent Toxoplasma infections than the general population. The effect was highest at acute infection and then slowly decreased.

    I can’t find the reference, but owning a cat is actually only a minor risk factor for being infected – most risk is from eating undercooked meat (sushi, rare steak).

    Anyway, sure you’re more likely to die, but some would say taking more risks is a good thing.

  14. Another reason not to flush your cat litter–the Toxoplasma being washed into the oceans on the Pacific Coast is infecting and killing sea otters.

  15. The hurt locker bomb tech Jeremy Renner’s character ! he didn’t know why he did the shit he did ! omg, everything makes sense now!!

    1. Dude, he was married to Kate from LOST! His decision was the only rational one.

      Re:Toxo; a disease that makes you like cats seems somewhat benign save for very specific circumstances.

      Perhaps children guilty of committing acts of animal cruelty could be forcibly infected with this. It may prevent them from becoming serial killers.

      Well, one way or another…

  16. It’s a long, long chain of deductions from the gut of a cat to the status of “free will” – a vague concept like “god” or “terrorist” that never gets defined – so that everyone can carry around a different idea of it, and everyone can convince themselves that *they* have got it.

    This ‘revelation’ isn’t new. If, chopping wood in the forest, an axe slips and cuts off your arm, you have no “free will” to do anything that requires using that arm. We are far, far from distinguishing “how much” “free will” we have compared to cockroaches. Interjecting this ‘revelation’, therefore, is sophomoric.

  17. Very interesting. I personally had an infection of Entamoeba Histolytica after visiting South America. For roughly a year afterward I experienced mood swings, heightened aggression and geophagia impulses.

  18. Sapolsky’s statement about motorcyclists comes from the fact that T. gondii has been implicated to change the behavior of humans which includes making them get into more traffic accidents (based on a study of 8000 soldiers who were in traffic accidents) by testing them for antibodies to T. gondii. It makes women more flirtatious as well. You may want to do a search on Google Scholar for “taxoplasma gondii” before making statements that you cannot back up and trying to label someone a fool just because they are involved with research that you have not read yet. By the way, Toxoplasma has been known for over 100 years and they have only started looking into it when AIDS patients started dieing from it in the 80s.

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