It's clearly a commensal symbiote: for cats, it assists them in catching prey.
In rats and humans, its changing prevalance helps adjust the relative expression of different behavioral strategies, faster than inheritance alone could.
For example, the risk-taking and increased libido in rats shifts the infected slightly along the K-strategy/r-strategy reproductive spectrum. In some environments that's a win, others a loss, but the T.gondii increases rat behavior diversity, and thus the species' adaptability.
Similarly, its modulating effects on human suspicion, gregariousness, investment in fitness-signalling (clothing), and obedience/trust sometimes help and sometimes hurt, depending on an ever-changing environment.
What if we 'cured' this and found the resulting human populations were less resilient against war, ecological stresses, and rapid technological/cultural change?
(I'm only half joking. And a meta-parasite is making me write apologetics for other parasites. And this entire comment is just a long way of saying "I, for one, welcome our new Toxoplasmosis gondii overlords" without getting immediately downvoted.)
The T. gondii, as viewed from the cat's perspective might be a symbiote, but from the rat's perspective, is certainly a parasite, isn't it? The T. gondii is benefiting at the expense of the rat. Do biologists classify things as both simbiotes and parasites?
Given all the nasty science swirling around this parasite, is
it time for cat lovers to switch their allegiance to other
animals?
Even Flegr would advise against that. Indoor cats pose no
threat, he says, because they don’t carry the parasite. As
for outdoor cats, they shed the parasite for only three
weeks of their life, typically when they’re young and have
just begun hunting.
> 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.
This reminds me of a lot of cat-people I know. But that might just be selective recall.
We have six cats at the house here, hence the username 'nekojima', Japanese for 'cat island'.
I have long suspected a parasitic role (either us or them for attention rather than brain damaging) or an element of craziness in our having so many cats. So far our own scientific analysis has been interrupted by near constant feline requests for attention, food or having to clean a little more than 'normal'.
Sigh - I spent over 2 hours talking with this reporter trying to help her understand the limitations of this guy's studies, but she doesn't seem to have taken on board anything I said... Of course, he could be right and it could also be that the X-rays emanating from a TV really do protect you from malaria. Or it could be that you watch TV indoors and so don't get as many mosquito bites. So, yes, it could be that Toxo causes increased risk-taking ... OR it could be that risk-takers drive their cars more crazily and do things that cause them to be slightly more likely to get infected! There can also be a strong socio-economic bias to infection rates and it could be that people from Czech farms are more likely to be infected from eating vegetables from their cat-feces-infested gardens and more likely to be in a car crash driving home wasted after a Polka 10 miles away in the nearest town in a Lada held together with superglue while their affluent city friends take the bus or drive a BMW and eat vegetables from a mass-production farm in the Ukraine. Etc., etc.
On the other hand, the animal data are real (good, controlled experiments) and so it is TEMPTING to believe but the human data are really not good experiments. WAY too many "confounding variables" and no controls. There is one study with US military recruits that found a very slight increase in the likelihood that if you entered the army Toxo-negative and became Toxo-positive while in the army you were ever so slightly to be discharged with a diagnosis of schizophrenia than someone who stayed Toxo-negative. But the difference was not statistically significant, in my opinion (predict 13 patients would be discharged with schizophrenia in the Toxo-positive group and saw 15 were - NOT a significant difference).
Bottom line, it's crap science and of course he could be right but so could the guy who says the world will end this November...
If one of the main risk factors for the parasite is exposure to cats, how exactly is that increased by "risk-taking behavior"? Are cats considered risky?
You wrote a lot but none of it was persuasive. Other than random exaggerated "possibilities," what reason do you have to say it's crap science?
This dude knows nothing about cats and crazy. Cats make you crazy by pawing your face all night for attention and sleeping all day because they're tired from being awake until dawn.
"Cats make you crazy by pawing your face all night for attention"
For a while one of our cats was waking me up by climbing to the top of a wardrobe and then launching itself onto my stomach as I slept from this considerable height - which appears to be the cat equivalent of BASE jumping.
The fact that I endured this behaviour a few times with relative good humour probably indicates that I probably have this mind control parasite!
hahaha, word. What makes you crazy is that cat wants attention when you are busy or sleepy and wants you away when you want to pet it, screams and breaks stuff when it's hungry and scratches your furniture.
But you still keep the cat, huh? That must be the parasite at work. Actually, now I have a whole new perspective on cat owners in general, and why they put up with their pets..
I can't believe I read through the whole thing - it started off kind of crazy. Still, just as Flegr himself says, the change in behavior is minimal - chances are high that the average individual's life wouldn't be much different whether he/she had the parasite or not.
Still, it's amazing how such a primitive organism can change your brain's function - makes you wonder if there's a parasite that's making people stupid/smart/lazy/etc.
For dopamine, which according to the cat article is elevated in Toxo-infected humans, the associated personality type is "risk-taking, curious, creative, impulsive, optimistic and energetic". Plus the associated decrease in fear response in rats: who does that sound like?
i.e. I wonder what percentage of entrepreneurs are Toxo infected?
Here's the question, though: are the risk-taking humans risk-taking because they're infected, or are they infected because they're risk taking. Correlation, unfortunately, doesn't imply causation.
The "fatal attraction to cat urine" studies are somewhat imperfect [1]. I'm friends with a student who's doing similar studies with mice but with better spatial discrimination . The consensus seems to be that while the fear response goes down, the idea that it's attractive to the rodents is more difficult to replicate.
"We evaluated 148 case patients with recent T. gondii infection and 413 control patients. In multivariate analysis, an elevated risk of recent T. gondii infection was associated with the following factors: eating raw ground beef (adjusted odds ratio [aOR], 6.67; 95% confidence limits [CLs], 2.09, 21.24; attributable risk [AR], 7%); eating rare lamb (aOR, 8.39; 95% CLs, 3.68, 19.16; AR, 20%); eating locally produced cured, dried, or smoked meat (aOR, 1.97; 95% CLs, 1.18, 3.28; AR, 22%); working with meat (aOR, 3.15; 95% CLs, 1.09, 9.10; AR, 5%); drinking unpasteurized goat’s milk (aOR, 5.09; 95% CLs, 1.45, 17.80; AR, 4%); and having 3 or more kittens (aOR, 27.89; 95% CLs, 5.72, 135.86; AR, 10%). Eating raw oysters, clams, or mussels (aOR, 2.22; 95% CLs, 1.07, 4.61; AR, 16%) was significant in a separate model among persons asked this question. Subgroup results are also provided for women and for pregnant women.
Conclusions. In the United States, exposure to certain raw or undercooked foods and exposure to kittens are risk factors for T. gondii infection. Knowledge of these risk factors will help to target prevention efforts." http://cid.oxfordjournals.org/content/49/6/878.full
After reading this article (which was very enjoyable by the way), I am now curious to find out if I myself may be the puppet of some parasite. Is there any way to find this out easily?
Radiolab delved into this a bit in their show "Parasites" from a while back. You can listen to the relevant segment under "The Scratch", although I recommend the whole thing, of course:
When and if this research is sufficiently established, people will most likely have an averse (and perhaps unwarrantedly so) attitude to having cats as pets.
Or maybe we will start vaccinating the kitties when they are young enough to start hunting.
Other links on the 'net that I've found are reporting (without any citations) that the parasite can be detected with a blood test (according to wikipedia, not true) and that it cannot be treated (again, according to wikipedia, also not true).
I've seen articles about this parasite pop up over at least the last 5 years. If it was a truly serious problem I'm sure there'd be more information about it. It smells a bit like FUD though.
A search for Toxoplasmosis on G-scholar reveals that this parasite is in fact a problem for immune compromised patients and infants. Although I do not think WebMD is a reliable source, another comment here cites them to indicate that infections are usually cleared up by our immune system. This appears to be plausible, but because the parasite enters cells, and can hide in a latent phase, your immune system may be unable to clear the infection permanently. Because the parasite can halt the cell cycle, it may be able to hide indefinitely. I would not be concerned about a latent parasite, but its re-emergence may become a problem if your immune system becomes compromised.
A correction to your statement that, according to wikipedia, the disease cannot be tested by blood sample. Wikipedia, in fact, stats that it can be tested by blood or other tissue, but only if the parasite is active (non-latent).
Regarding its effect on behavior, the parasite seems to increase dopamine levels and possibly inhibit fear response. Since the increased dopamine is caused by an enzyme made by the parasite, this probably only occurs during a full scale infection. The inhibition of fear may occur while the parasite is inactive, if the parasite is able to enter cells in your amygdala. I do not see this inhibition of fear as long-lasting, except perhaps in extreme cases.
One disclaimer, I grew up with a few cats, so I may have been, or am currently, infected. I cannot rule out that this parasite is manipulating me to write this comment. Now I'm off to find some cat pee. Can't get enough of that smell, mmmmmmmm.....
WebMd [1] and some other places [2] talk about it like it's a bacteria that your immune system fights off then you are safe from for the rest of your life. They don't seem to talk about any long term effects, and focus on just the risk the acute symptoms can have.
Five years isn't all that much time as far as bio-med research is concerned. I would expect to start seeing definite results in maybe a few years.
As for detection and treatment, the subject being discussed in the Wiki article is the effect of initial infection. The parasite sticks around in a latent form after being "fought off" and is being hypothesized to have additional long-term effects.
The article is very interesting but seems to inflate the fact that if you have a cat you're most likely going to contract T. gondii.
If indoor cats don't carry T. gondii and outdoor cats only carry the parasite for three weeks of their life, isn't the risk of getting this parasite very low since there is only a three week window? Perhaps I'm misinterpreting this. Please correct me if I'm wrong.
I think T.gondi is the reason kitten videos are so popular on YouTube - CDC should look into this - it might be a global pandemic ;)
I want to do an experiment: A/B testing landing page with and without cute kitten photos. I'm sure the one with cats photos will have much higher conversion rate.
I also believe baby humans pass on a parasite that influences the parent to take and share voluminous photos and to regard every ounce of vomit from the child as a work of genius. This merits further study.
Hold on, my cat is trying to type sometjfkd a;dsjkf jdfmfddddddsa
I'm glad he was smart/sane enough to even think about going to the lab. When something is messing with your mind, can you even think of such logical reasonable things?
[+] [-] gojomo|14 years ago|reply
It's clearly a commensal symbiote: for cats, it assists them in catching prey.
In rats and humans, its changing prevalance helps adjust the relative expression of different behavioral strategies, faster than inheritance alone could.
For example, the risk-taking and increased libido in rats shifts the infected slightly along the K-strategy/r-strategy reproductive spectrum. In some environments that's a win, others a loss, but the T.gondii increases rat behavior diversity, and thus the species' adaptability.
Similarly, its modulating effects on human suspicion, gregariousness, investment in fitness-signalling (clothing), and obedience/trust sometimes help and sometimes hurt, depending on an ever-changing environment.
What if we 'cured' this and found the resulting human populations were less resilient against war, ecological stresses, and rapid technological/cultural change?
(I'm only half joking. And a meta-parasite is making me write apologetics for other parasites. And this entire comment is just a long way of saying "I, for one, welcome our new Toxoplasmosis gondii overlords" without getting immediately downvoted.)
[+] [-] liber8|14 years ago|reply
The T. gondii, as viewed from the cat's perspective might be a symbiote, but from the rat's perspective, is certainly a parasite, isn't it? The T. gondii is benefiting at the expense of the rat. Do biologists classify things as both simbiotes and parasites?
[+] [-] unknown|14 years ago|reply
[deleted]
[+] [-] unknown|14 years ago|reply
[deleted]
[+] [-] kqr2|14 years ago|reply
[+] [-] draggnar|14 years ago|reply
[+] [-] wisty|14 years ago|reply
This reminds me of a lot of cat-people I know. But that might just be selective recall.
[+] [-] nekojima|14 years ago|reply
I have long suspected a parasitic role (either us or them for attention rather than brain damaging) or an element of craziness in our having so many cats. So far our own scientific analysis has been interrupted by near constant feline requests for attention, food or having to clean a little more than 'normal'.
[+] [-] iopuy|14 years ago|reply
Off topic but interesting. Guess "Iwo Jima" follows suit. I learn something new here every day.
[+] [-] white_devil|14 years ago|reply
It's actually 'shima' for island. Not sure if 'jima' works too, but shima is definitely more common.
[+] [-] clutchski|14 years ago|reply
http://www.edge.org/3rd_culture/sapolsky09/sapolsky09_index....
[+] [-] mb22|14 years ago|reply
Bottom line, it's crap science and of course he could be right but so could the guy who says the world will end this November...
[+] [-] MSexton|14 years ago|reply
[+] [-] ahoyhere|14 years ago|reply
You wrote a lot but none of it was persuasive. Other than random exaggerated "possibilities," what reason do you have to say it's crap science?
[+] [-] sakura_k|14 years ago|reply
[+] [-] arethuza|14 years ago|reply
For a while one of our cats was waking me up by climbing to the top of a wardrobe and then launching itself onto my stomach as I slept from this considerable height - which appears to be the cat equivalent of BASE jumping.
The fact that I endured this behaviour a few times with relative good humour probably indicates that I probably have this mind control parasite!
[+] [-] zalew|14 years ago|reply
and this http://www.doggiestylish.com/store/images/wordpress/uploads/...
Cats are awesome!
[+] [-] saturn|14 years ago|reply
[+] [-] jakeonthemove|14 years ago|reply
Still, it's amazing how such a primitive organism can change your brain's function - makes you wonder if there's a parasite that's making people stupid/smart/lazy/etc.
[+] [-] marshray|14 years ago|reply
[+] [-] jlees|14 years ago|reply
For dopamine, which according to the cat article is elevated in Toxo-infected humans, the associated personality type is "risk-taking, curious, creative, impulsive, optimistic and energetic". Plus the associated decrease in fear response in rats: who does that sound like?
i.e. I wonder what percentage of entrepreneurs are Toxo infected?
[+] [-] rflrob|14 years ago|reply
The "fatal attraction to cat urine" studies are somewhat imperfect [1]. I'm friends with a student who's doing similar studies with mice but with better spatial discrimination . The consensus seems to be that while the fear response goes down, the idea that it's attractive to the rodents is more difficult to replicate.
[1] Free at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1690701/?tool=pu...
[+] [-] abecedarius|14 years ago|reply
[+] [-] mazsa|14 years ago|reply
Conclusions. In the United States, exposure to certain raw or undercooked foods and exposure to kittens are risk factors for T. gondii infection. Knowledge of these risk factors will help to target prevention efforts." http://cid.oxfordjournals.org/content/49/6/878.full
[+] [-] micheljansen|14 years ago|reply
[+] [-] spacemanaki|14 years ago|reply
http://www.radiolab.org/2009/sep/07/
[+] [-] nodemaker|14 years ago|reply
Or maybe we will start vaccinating the kitties when they are young enough to start hunting.
[+] [-] maxerickson|14 years ago|reply
Pregnant women already routinely get advice not to clean litter boxes and such, which, anecdotally, sometimes translates into getting rid of the cat.
[+] [-] ryan-allen|14 years ago|reply
Other links on the 'net that I've found are reporting (without any citations) that the parasite can be detected with a blood test (according to wikipedia, not true) and that it cannot be treated (again, according to wikipedia, also not true).
I've seen articles about this parasite pop up over at least the last 5 years. If it was a truly serious problem I'm sure there'd be more information about it. It smells a bit like FUD though.
Can anyone else elaborate on this further?
[+] [-] Alex3917|14 years ago|reply
That's not really how science/epistemology work.
[+] [-] Read_the_Genes|14 years ago|reply
A correction to your statement that, according to wikipedia, the disease cannot be tested by blood sample. Wikipedia, in fact, stats that it can be tested by blood or other tissue, but only if the parasite is active (non-latent).
Regarding its effect on behavior, the parasite seems to increase dopamine levels and possibly inhibit fear response. Since the increased dopamine is caused by an enzyme made by the parasite, this probably only occurs during a full scale infection. The inhibition of fear may occur while the parasite is inactive, if the parasite is able to enter cells in your amygdala. I do not see this inhibition of fear as long-lasting, except perhaps in extreme cases.
One disclaimer, I grew up with a few cats, so I may have been, or am currently, infected. I cannot rule out that this parasite is manipulating me to write this comment. Now I'm off to find some cat pee. Can't get enough of that smell, mmmmmmmm.....
More technical wiki article: https://en.wikipedia.org/wiki/Toxoplasma_gondii
[+] [-] Game_Ender|14 years ago|reply
[1] http://www.webmd.com/food-recipes/food-poisoning/toxoplasmos... [2] http://www.pamf.org/serology/clinicianguide.html
[+] [-] yew|14 years ago|reply
As for detection and treatment, the subject being discussed in the Wiki article is the effect of initial infection. The parasite sticks around in a latent form after being "fought off" and is being hypothesized to have additional long-term effects.
[+] [-] genbattle|14 years ago|reply
(It was probably posted previously before that)
[+] [-] evoltix|14 years ago|reply
If indoor cats don't carry T. gondii and outdoor cats only carry the parasite for three weeks of their life, isn't the risk of getting this parasite very low since there is only a three week window? Perhaps I'm misinterpreting this. Please correct me if I'm wrong.
[+] [-] nivertech|14 years ago|reply
I want to do an experiment: A/B testing landing page with and without cute kitten photos. I'm sure the one with cats photos will have much higher conversion rate.
[+] [-] droctopu5|14 years ago|reply
Hold on, my cat is trying to type sometjfkd a;dsjkf jdfmfddddddsa
fidddddddddddddddx fj
[+] [-] danso|14 years ago|reply
[+] [-] marshray|14 years ago|reply
[+] [-] winter_blue|14 years ago|reply
[+] [-] marshray|14 years ago|reply
I'm surprised, it's a total cultural meme.
Probably dates back to Newton and those other alchemists who were really fascinated by the, um, transformative properties of mercury.