Thursday, July 5, 2012

The Cat Factor: Toxoplasma Infection Changing our Smell Perception

How does brain chemistry affect our sense of smell? Does your fluffy pussycat have anything to do with it? And what about infections by parasites making our sense of smell and our overall behavior different? 

"In a recent study, Czech scientists gave men and women towels scented with the urine of various animals—horses, lions, hyenas, cats, dogs—which they rated for “pleasantness.” Turns out, men who tested positive for Toxo [i.e.Toxoplasma gondii parasite] found the smell of cat urine more pleasant than men without Toxo[...] French chemists discovered something unexpected in a 1995 sauvignon blanc from Bordeaux: 3-mercapto-3-methylbutan-1-ol, a grape breakdown product that doubles as a fragrant pheromone in cat pee.[...]
Maybe, like with the rats, Toxo is changing something about the way the brain processes cat smells, making the men with Toxo find it more pleasant. Could it be that Toxo is the perfumer par excellance [sic], with privileged access to the very seat of smell itself? Is it a coincidence that “le monstre” of the perfume industry [i.e. Chanel No.5] and the Bordeaux sauvignon blanc both come from France, a country with one of the highest rates of Toxo in the world? "

Thus theorizes a most interesting article on writen by Patrick House. One can take issue with the fact that "musk" is used indiscriminately throughout the article for all animalic scents as per perfumery jargon, though we know different; that civet doesn't smell of cat urine per se (rather blackcurrant buds absolute does, as highlighted in our own article the other day); and that Chanel No.5 is really musky but not cat-urinous like, even if "catty" in its attitude. Still, it makes a most interesting case for the way brain chemistry and circuiting is playing a major role in our perception of smells and our reaction to them through minute details we don't take into account day in day out! 

There is also linking to other interesting previously published articles, stating that about 40% of the general population carries the parasite (once you have it, usually asymptomatically, you develop antibodies to it and carry it on for life) and I quote from one of them:

"Infected men [with Toxoplasma gondii] have lower IQs, achieve a lower level of education and have shorter attention spans. They are also more likely to break rules and take risks, be more independent, more anti-social, suspicious, jealous and morose, and are deemed less attractive to women."
"On the other hand, infected women tend to bemore outgoing, friendly, more promiscuous, and are considered more attractive to men compared with non-infected controls.
"In short, it can make men behave like alley cats and women behave like sex kittens".
"Another study showed people who were infected but not showing symptoms were 2.7 times more likely than uninfected people to be involved in a car accident as a driver or pedestrian, while other research has linked the parasite to higher incidences of schizophrenia." [from same source]

Interesting, don't you think? 

Now, I happen to know I have been infected with this particular parasite in the past (probably from eating rare meat, a habit that French people also take to with a vengeance making them one of the people with the highest rates of Toxo in the world) and I can attest these things:
I have always liked cats, though never owning one, and always found their urine sharply ammoniac and very intense (i.e. not exactly pleasant). I have not  developed a more outgoing nature compared to previously. Nor have I noticed a sharper interest in male attention that is irresponsive to other accouterments of my appearance. Can't say I have ever being involved in a car accident, which is rather miraculous for living where I live (where car accidents are frequent and driving is aggressive) and my risk-taking is just about level to what it used to be. 
I may have become a little bit more aloof though, being crankier compared to my puppy fat years, i.e. cattier. 

What do you think? 

pic via


  1. Now I need to know if I'm infected or not. I had read something similar, and wondered. No particular preference for cats, can take musks, dislike marine. Who knows...

    I also read that the infection rate is much lower in sanitized US. Which might explain a few things...


  2. M,

    there's a really simple blood work test for toxo. It's routine check for women when trying to conceive (because toxo can be dangerous in pregnancy), but you can ask for it specifically. It's simple and foolproof. If they find antibodies, you have it. If not, you don't. It's interesting to know for sure!

    Usually it's carried in cat feces (and not urine) and through rats (though I think that's unusual for a way to be transmitted to a human unless in undeveloped countries) and of course through meat that has been undercooked and was at some point coming into contact with the parasite (through hands that carried it). Meat is the reason why the French have it. I don't know whether Americans tend to cook their meat thoroughly though, I had it both ways when in the US (was asking for it, when given the option, nevertheless)

  3. I'm a weird American - I love nearly raw meat - the bloodier the better. I had steak tartar the one and only time I was in Paris.

    I wonder if I have that parasite? Not sure if I was tested for it when I was pregnant w/my son 24 years ago. I cannot stand the smell of cat pee, and in fact some junipers? smell like cat pee to me..yuck.

    Thought-provoking post E! Thank you!

  4. C,

    you're welcome. It made an impression on me too.

    Ah, but I attribute those qualities to your European ancestry. (Though Greeks are fans of charcoaled meat). Love steak tartare myself.

    You might, though now with a son being 24 years old it's not a concern. (wow, you look too young for that!)
    Junipers, eh? Hadn't made the connection but it's worth investigating. Thanks!!

  5. Perfumeshrine:

    Americans tend to eat their steak rarer than in Europe. Indeed, ordering well done steak here is a social offense. Anything more than medium rare is frowned upon, and I suspect one could be asked to leave a restaurant if such a request were done. But quality beef here is much better and smoother, and well done would indeed be inappropriate.

    But I think hygienic measures are much more strict here than in Europe when it comes to food, so contamination is more difficult.


  6. M,

    that's interesting to confirm thanks.
    I had rare steak when there many times, but then I asked for it specifically. It was delicious each and every one of them. (More than I can say about other things)
    Here the meat selection isn't the greatest (we're not a great meat producing country) and therefore well-done is condoned for hygiene purposes. When offered a choice cut from some butcher whom they know well, many people however opt for a medium.

    So, the stricter measures might account for the lower toxo occurrence? Or less cats per capita overall as opposed to France?

  7. P:

    who knows. There are plenty of cats, but they are usually indoor ones. Few cats are allowed to go outside.

    In general, I think it's just that Americans love sanitized environments, and hygiene standards are much higher. Perhaps too much.


  8. M,

    no strays and no "talking a walk by the neighbor's yard" thing, eh? Makes sense.

    Yeah, makes sense what you say overall.

  9. Miss Heliotrope03:09

    In so many things, Australia is halfway between Europe & US: ie cleanliness rules vs food. Steak - we just order whatever: if you're into it have it rarer, if not o well, although the status of having it rare is both more "foodie" & more often done by men. I've had rare Australian wagu steak that just melted...

    We have a cat but no idea about Toxo - he's a half in half out cat (we have a cat curfew in our region - to help the native animals not get eaten - or the cat not get beaten up by possums) & prefers to use his litter for urine only (& balances on the edge of the box, so we've had to weight it so it doesnt tip over).

  10. annemariec05:14

    In a general sense I tend to believe that much of our scent perception happens in our brains rather than on our skins. I've never really accepted the whole skin 'chemistry' thing. Even accepting differences in dryness/oiliness, age, diet, etc - are our skins different enough to account for the radically different reactions we ofen have to scents? Our brains are, I belive, but not our skins.

  11. C,

    I think you're right in your assessment. This was my impression as well. Aussies do keep a lot of British traditions and sprinkle them with their own marvelous sense of humor and outgoing mentality. {*love*}

    I suppose since cats bury their feces there is no great risk of contamination, unless you actually have a vegetable bed and the cat defecates there, but I'm sure you would have known had that been the case.

    Possums chasing wandering cats, now that would never have crossed my mind here. But you're right for where you are! Such a diverse wild life.

  12. AnnemarieC,

    I am entirely of your way of thinking!!

    I believe the "skin chemistry" card has been played to death to first imbue fragrance with some individuality marketing-wise (making every woman believe her fragrance, though mass produced, is hers alone) and second to politely dismiss something we don't like without offending the individual ("oh must be my skin chemistry, it doesn't suit me").
    It's been a line so much beaten to death it's become a Pavlovian reflex among pop conversation, like how lavender supposedly creates relaxation and is therefore a soporific (not in my and others' experience, when it's pure, it's not).

    There's a whole body of literature, some of it bordering on the outrageously racist, I assure you, about how some skins smell different to others or react different to other skins to the same ingredients. It almost sounds as if different people belong to different species!

    Brain perception/neurotransmitting on the other hand accounts for a much wider differentiation of olfactory effects based on perceptible and often recalled stimuli, such as associations and memories of past exposure (thus creating understandable differences) or actual circuiting differences that can be measured scientifically.
    But the average perfume buyer isn't too much into science and "skin chemistry" seems an easier, more gullible explanation, exactly because it's actually arcane.

  13. annemariec23:57

    Wonderful! And you express it so much better than I could. Many thanks. Once again a few weeks ago I had a perfume SA say to me 'let it settle on your skin for a while: we all make our own perfume'. Sigh.

    One experiment I'd love to try would be to spray the same perfume on two or three different people and have several OTHER people declare how it smells to them on each of the test wearers.

  14. Veronique15:55

    This idea about changes in character evoked from the contamination with catty infections - well, I suppose same could be said about things happening with dog holders. Just maybe the set of infections could be a litle different.

    I have a cat. A very homely one. We do not travel outdoors. Though you may never be sure about the sanitary cleanliness for obvious reasons... I am a strange blend of adventurousness and home sitting both cherished. Something like that, if this can be a proof...:)))

    My suggestion is that a character change, apart from obivous intellectual inclination to this kind of animal attractiveness or another, may stem from a battle that you immune sustem works out to fight an inflammatory stage of this thing. Constant immune tention is consisttently supported by a more intense extraction of hormones (which are actually of androgenic range), hence promote a more stress-seeking disposition and a love for overcoming difficulties than others. It's just like this, I believe...(whisper: a moderate smelliness may also be present to a bouquet...)))

    Whether it's catty, or puppyish, or whatever (gee, I cannot even imagine what if you keep an iguana, from the tropics))) - it's all about the way you build up you personal symbiotic world around animals and humans.

  15. Universe is being the usual dorky thing.

    I injured my right hand so I can't do any crafts or more serious gardening (and gods know it needs to be done) so I'm going through my backlog of books and blogs and stuff. Two days ago, I brought a textbook on evo bio from Prague, written by the same guy who does the toxo research. He's smart like hell and immensely funny, too, even though evolutionary biology is not known for humor... or is that? and now I bump into this bit about the toxo research... it's holidays but I'll find the source and I can go and ask about cat piss and musk in detail when school starts again. The natural scientists are usually friendly to curious people:D

  16. AMC,

    that's a great idea for an experiment: this is how it should be done. The sprayee doing the sniffing just doesn't cut it.

  17. veronique,

    sorry for the late reply.

    You bring an interesting thought into this! Yes, there might be something to be said about cross-"contamination" between species. Certainly biology hasn't yet answered all questions arising from such situations. Since dogs themselves possess such a keen odor it would be very interesting to see whether there would be any interaction between dogs and dog owners re: brain perception of smells when affected with some puppy "germ" or other. Someone should do this research!

  18. L,

    so glad you found the post and had the time to reply to it! It would be very interesting to find out more! Please let me know when you do.

    And happy holidays!! :-D

  19. Not my holidays. The university is closed and prof. Flegr is taking time off, playing with cats (he indeed has some) and their parasites:D
    Meantime, one of my books is going to print tomorrow, I'm working on another but whatever is sent off means that I can slow down at least a little bit.


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