Toxoplasma gondii in a human cell.
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Feeling sociable or reckless? You might have toxoplasmosis, an infection caused by the microscopic parasite Toxoplasma gondii, which the CDC estimates has infected about 22.5 percent of Americans older than 12 years old. Researchers tested participants for T. gondii infection and had them complete a personality questionnaire. They found that both men and women infected with T. gondii were more extroverted and less conscientious than the infection-free participants. These changes are thought to result from the parasite's influence on brain chemicals, the scientists write in the May/June issue of the European Journal of Personality.
“Toxoplasma manipulates the behavior of its animal host by increasing the concentration of dopamine and by changing levels of certain hormones,” says study author Jaroslav Flegr of Charles University in Prague, Czech Republic.
Although humans can carry the parasite, its life cycle must play out in cats and rodents. Infected mice and rats lose their fear of cats, increasing the chance they will be eaten, so that the parasite can then reproduce in a cat's body and spread through its feces [see “Protozoa Could Be Controlling Your Brain,” by Christof Koch, Consciousness Redux; Scientific American Mind, May/June 2011].
In humans, T. gondii's effects are more subtle; the infected population has a slightly higher rate of traffic accidents, studies have shown, and people with schizophrenia have higher rates of infection—but until recent years, the parasite was not thought to affect most people's daily lives.
In the new study, a pattern appeared in infected men: the longer they had been infected, the less conscientious they were. This correlation supports the researchers' hypothe-sis that the personality changes are a result of the parasite, rather than personality influencing the risk of infection. Past studies that used outdated personality surveys also found that toxoplasmosis-related personality changes increased with the length of infection.
T. gondii is most commonly contracted through exposure to undercooked contaminated meat (the rates of infection in France are much higher than in the U.S.), unwashed fruits or vegetables from contaminated soil, and tainted cat litter. The parasite is the reason pregnant women are advised not to clean litter boxes: T. gondii can do much more damage to the fetal brain than the personality tweak it inflicts on adults.
This article was originally published with the title Common Parasite Linked to Personality Changes.
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27 Comments
Add CommentSo it would be prudent to remove cat from the menu?
Reply | Report Abuse | Link to thisnot if it is property cooked.
Reply | Report Abuse | Link to thisSo, the rise of civilization in ancient Egypt was due to cats taming the Egyptians by infecting them. I guess that was why they also worshiped a cat god.
Reply | Report Abuse | Link to this"In the new study, a pattern appeared in infected men: the longer they had been infected, the less conscientious they were. This correlation supports the researchers' hypothe-sis that the personality changes are a result of the parasite, rather than personality influencing the risk of infection" ------------------------- I am not really sure how the researchers can conclude that the converse cannot be true - People with a shaky conscience may have reduced immunity rates and hence the parasite tends to live longer. The more shakier the conscience, the lesser the immunity and hence the longer the life of the parasites.
Reply | Report Abuse | Link to thisSo . . . is there a way to get rid of this parasite? And if it is eradicated does personality revert to the earlier form???
Reply | Report Abuse | Link to thisPlease answer greenshadow22's comment. Whom do we ask? where can we go? alan b. (Inland Empire, Southern California)
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to thisCat is always cooked properly- you need to to remove the skin properly; although I have heard there is more than one way to do this.
Visit the Centers for Disease Control: cdc.gov/parasites/toxoplasmosis/prevent
Reply | Report Abuse | Link to thisThis would be fairly easy to study, but it would be most interesting to see whether long-term exposure is associated with the tendency to acquire more and more cats in the household. Surely I'm not the only one to observe that "cat-lovers" behave with a certain aggressive irrationality regarding their pets?
Well ......... from what this article says .... why would we want to get rid of it ? the side effects seem quite good.
Reply | Report Abuse | Link to thisThe worm in my brain is saying "nothing to see here... move along". It sounds, a lot like Obi-Wan Kenobi voice!? GK
Reply | Report Abuse | Link to this"Loss of conscientiousness..." is a good side-effect? Is it reasonable to assume that any parasite which takes up residence in your brain (emitting chemicals that alter your behavior) can be harmless?
Reply | Report Abuse | Link to thisThis article inexplicably downplays the negative effects.
Recently, toxoplasmosis has been associated with schizophrenia, Alzheimers, and Parkinsons. In addition, it's associated with a higher rate of car accidents and violent suicide in women. Even people with healthy immune systems can experience damage to the brain, and especially the eyes. For people with compromised immunity and for infants, the infection can be severely debilitating or life-threatening.
You can do your own research on this.
Sorry--
Reply | Report Abuse | Link to this"less conscientiousness..." NOT "loss of conscientionsness..."
This could explain the cat lady syndrome. The cat parasite invades the cat owner's brain, making them less conscientious about limiting the number of cats they can reasonably clean up after, or afford to feed. This might even be an evolutionary dynamic in preserving the cat to human synergy over the centuries.
Reply | Report Abuse | Link to thisAs of today there is no way to eliminate the parasite. Once infected it stays with you for life - although usually in a dormant state unless the imune system is weak for whatever reason. People with weakened immune systems will need special treatment to keep symptoms at bay.
Reply | Report Abuse | Link to thisFirst you have to explain how the conscience possibly, or at least plausibly, could impact the immune system.
Reply | Report Abuse | Link to thisOtherwise we could just as easily attribute the whole thing to the presence of catnip and scratching posts.
The authors sampled 181 Toxo negative females, 95 toxo neg males and 30 toxo positive females and 17 toxo positive males (all undergrad students). They found significantly higher scores of extraversion and lower scores of conscientiousness on a common personality personality questionnaire. To give some context, this means students in the toxo group scored 4 to 8 points higher on extraversion or 4-10 points lower on conscientiousness when mean scores were ~100 points. In both cases, effect sizes were small (eta-squared <=.017).
Reply | Report Abuse | Link to thisThis study looks like another example of data fishing. When we account for the number of comparisons these guys probably didn't report and the extent of publication bias inherent in psychology, a tiny effect associated with an organism which has rarely been shown to affect human behaviour (but which sounds really cool) is probably nothing more than junk science.
Good point. At a minimum, the results certainly don't preclude the possibility that the effects are not actually increased extroversion and reduced 'conscientiousness', but the subject's personal assessments of those personality characteristics (however they might have been indicated and determined by the questionnaire).
Reply | Report Abuse | Link to thisThe point is that there was no independent evaluation of the subjects' personalities... Perhaps the actual effect of infection is to make the subject feel guilty about irresponsible behavior, or something, if there is any effect...
Maybe, but because we haven't discovered the negatie influences on human beings, this parasite is still risky for men are always afraid of mystery.
Reply | Report Abuse | Link to thisThis microbe's ability to literally do brain surgery in the amygdala astounds some of the researchers.
Reply | Report Abuse | Link to thishttp://powertoxins.blogspot.com/2012/07/hypothesis-microbes-generate-toxins-of.html
Now I understand why I'm a bad bad boy who lives during the night and sleeps during the day...it's related to that parasite...;-))
Reply | Report Abuse | Link to thisThis was one weird article. Who ever tests for this parasite? Do we care to? Are there others? Pretty strange story.
Reply | Report Abuse | Link to thisToxoplasmosis has been linked to neurological damage and seizures in babies before and after birth,
Reply | Report Abuse | Link to thisand also in folks with AIDS and immune compromise.
The extroversion noted in the study clearly doesn't compensate for this type of harm.
See the Mayo Clinic's comments:
http://www.mayoclinic.com/health/toxoplasmosis/DS00510/DSECTION=symptoms
Lots of work was done in University of Salford. Lots of support for the idea; after all it survives in the rat/cat population probably by altering the behaviour of the rat (they expose themselves to danger more readily).
Reply | Report Abuse | Link to thisThere was a study in France some years ago which looked for antibodies to T.gondii in drivers involved in RTAs and compared the infection rates to those in the average population. The RTA drivers had a much higher likelihood of being infected than the average citizen.
BTW The postgraduate (female) researchers got told off for suggesting that a boy's "chances" were much higher with a girl who'd been infected with T. gondii!
Pirated from Wikipedia:
Reply | Report Abuse | Link to thisMedications that are prescribed for acute toxoplasmosis are:
Pyrimethamine — an antimalarial medication
Sulfadiazine — an antibiotic used in combination with pyrimethamine to treat toxoplasmosis
Combination therapy is usually given with folinic acid supplements to reduce incidence of thrombocytopaenia. Combination therapy is most useful in the setting of HIV.
Clindamycin
Spiramycin — an antibiotic used most often for pregnant women to prevent the infection of their children
(Other antibiotics such as minocycline have seen some use as a salvage therapy.)
Latent
In people with latent toxoplasmosis, the cysts are immune to these treatments, as the antibiotics do not reach the bradyzoites in sufficient concentration.
Medications that are prescribed for latent toxoplasmosis are:
Atovaquone — a medication that has been used to kill Toxoplasma cysts inside AIDS patients[26]
Clindamycin — an antibiotic which, in combination with atovaquone, seemed to optimally kill cysts in mice[27]
Sounds like a symbioses between cat and parasite: the parasite gets transmitted and the cat gets a meal.
Reply | Report Abuse | Link to this"Toxoplasma manipulates the behavior of its animal host by increasing the concentration of dopamine and by changing levels of certain hormones"” says study author Jaroslav Flegr
Reply | Report Abuse | Link to thisDid they actually measure dopamine and "certain" hormones?
Would this parasite make those who are infected more likely to infect other brains? If it does then the parasite would have succeeded in turning infected individual into zombies. I can see this happening in the following way;
Reply | Report Abuse | Link to thisHappy infected people are more willing to invite other people into their homes and meet their cats and/or cook them a raw stake to eat. In another words, the parasite makes people invite other people into their homes in order to infect them.