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The Return of the Puppet Masters
In a post from a few years ago titled, Do you love cats?, I wrote this:
Toxoplasma gondii is a favorite parasite of evolutionary biologists because it has an incredible property. The parasite lives in the guts of cats where it sheds eggs in cat feces that are often eaten by rats. Now how to get back from the rat to the cat? Amazingly, Toxoplasma gondii infects the brains of rats making them change their behavior in a subtle way that increases the genetic fitness of the parasite. Toxoplasma makes the infected rats less scared of cats and so more likely to be eaten!
Now here is the kicker. Toxoplasma gondii also infects a lot of humans.
Now here is the latest research finding;
Toxoplasma gondii infects 20–60% of the population in most countries...We confirmed, using for the first time a prospective cohort study design, increased risk of traffic accidents in Toxoplasma-infected subjects...Our results show that ...subjects with high titers of anti-Toxoplasma antibodies had a probability of a traffic accident of about 16.7%, i.e. a more than six times higher rate than Toxoplasma-free... subjects.
People with RhD blood factor have some protection - see the article for more. No word yet on whether this increases the probability of being eaten by cats although I suppose it would have to.
Posted by Alex Tabarrok on July 18, 2009 at 07:20 AM | Permalink
Comments
I wonder what percentage of soldiers who volunteer for combat have this infection? Same with cops, firemen and others in dangerous professions? I also wonder if it would be desirable to intentionally infect such people in order to improve their performance by reducing their fear? Would such people self-infect if they thought if would make them better at their jobs?
Posted by: Bruce Bartlett at Jul 18, 2009 7:53:34 AM
> No word yet on whether this increases the probability of being eaten by cats although I suppose it would have to.
I suspect the available statistics on people getting eaten by cats is insufficient to obtain a significant result. LOL
Posted by: Grammar nazi at Jul 18, 2009 8:29:25 AM
Some time ago, I read a report that indicated that European residents were two to three times more likely than American residents to be carriers of this parasite. I wonder why that is so.
Posted by: RW Rogers at Jul 18, 2009 8:37:28 AM
The scent of a cat in the enclosure didn't make them anxious, and they went about their business as if nothing was bothering them. […] In some cases, they even took a special interest in the spot and came back to it over and over again.
That explains irrational love for cats (perfectly useless animals) in humans. Judging by my indifference to cats and accident-free driving record, I have none of this Toxoplasma thingy.
Posted by: Ozornik at Jul 18, 2009 8:40:38 AM
Cats eat vermin, very useful.
Posted by: Joshua Holmes at Jul 18, 2009 11:01:12 AM
awesome catch!
Posted by: razib at Jul 18, 2009 11:14:57 AM
How does this correlate with our increasingly large cult of safety?
Posted by: Yancey Ward at Jul 18, 2009 11:32:07 AM
The world is a much weirder place than I had imagined.
Posted by: honeyoak at Jul 18, 2009 11:50:52 AM
And perhaps the parasite contributes to the domestication of Cats if it similarly reduces fear in cats.
Posted by: Shane M at Jul 18, 2009 12:21:39 PM
Cats have been said to be able to detect those that aren't cat people and then tormenting them. I wonder if they have a way of noting the absence of the virus. Perhaps it produces a small change in scent.
Posted by: Greg Sanders at Jul 18, 2009 12:27:41 PM
Some time ago, I read a report that indicated that European residents were two to three times more likely than American residents to be carriers of this parasite. I wonder why that is so.
More cats in European cities?
Posted by: Francesco at Jul 18, 2009 12:29:46 PM
Uhm, doesn't this have scary military applications?
Posted by: Brian Moore at Jul 18, 2009 12:44:56 PM
"The world is a much weirder place than I had imagined." Perhaps it's a much wierder place than we can imagine?
Posted by: dearieme at Jul 18, 2009 4:17:36 PM
"I also wonder if it would be desirable to intentionally infect such people in order to improve their performance by reducing their fear?"
We have always been at war with Catasia.
Posted by: Vernunft at Jul 18, 2009 4:27:28 PM
I was once hit by a cat lady who ran a red light trying to get her cat to the vet hospital.
Posted by: db at Jul 18, 2009 4:56:42 PM
The most interesting part of it is that the Toxoplasma parasite seems to be the evolutionary cause of some humans having Rh-positive blood and some having Rh-negative, in much the same way that the parasite that causes malaria has resulted in the prevalence of sickle-cell anemia in malaria-infested regions of the world.
In other words, there would likely be some unspecified evolutionary advantage for everyone to be Rh-negative if we lived in a Toxoplasma-free world.
The universal presence of cats in close proximity to humans probably only dates from the dawn of agriculture, when cats made themselves useful as killers of the vermin teeming around granaries and crops. Indeed the propensity of domestic cats to toy with and kill small animals that they do not even bother to feed on might be a result of recent selection pressure for cats to make themselves as useful as possible by human standards. Still, there must have been some interaction with cats and their feces even in hunter-gatherer times (drinking from a polluted water hole during a drought, for instance).
Posted by: anonymous at Jul 18, 2009 4:57:15 PM
The effects are far, far beyond just liking cats.
The infection
1) Significantly increases risk for schizophrenia
2) Makes women more slutty
3) Makes men behave in ways that women find less attractive
4) Is the number 1 killer of many types of marine mammals
Posted by: Doc Merlin at Jul 18, 2009 6:18:02 PM
So was the guy who totaled my car eating cat sh
Posted by: anon2 at Jul 18, 2009 8:37:35 PM
Alex needs to post more.
Posted by: anon at Jul 18, 2009 9:20:05 PM
Tyler needs to cite Less Wrong more.
Posted by: SUR at Jul 19, 2009 12:04:11 AM
Cult of Safety driven by fear of being held responsible.
Cats are phat.
Posted by: Basho at Jul 19, 2009 1:40:40 AM
"2) Makes women more slutty"
How can i infect more women with that.
Posted by: anonymous at Jul 19, 2009 4:56:52 AM
Thank you for the warning!
Since I value traffic safety, I shall stop eating cat feces immediately.
Posted by: Safety First at Jul 19, 2009 4:25:14 PM
@Safety
You can also get it from undercooked meats.
from:
http://www.fsis.usda.gov/factsheets/parasites_and_foodborne_illness/index.asp#5
"By consuming foods (such as raw or undercooked meats, especially pork, lamb, or wild game) or drinking untreated water (from rivers or ponds) that may contain the parasite."
Also, it doesn't just transmit on surfaces it is in the body of the meat so you need to
"Cook all meats thoroughly to 160 °F."
Posted by: Doc Merlin at Jul 20, 2009 2:33:45 AM
The cat sleeps outside tonight.
Posted by: rmark at Jul 20, 2009 5:00:34 PM
