Could these cute cuddly things really be infecting half the human population of earth? Of course!
2 to 3 billion people, about half the world's population, have a brain parasite called Toxoplasma gondii, which causes a disease called toxoplasmosis. A vaccine is being developed and is showing great potential thus far.
The parasite's main host are cats, but infects many warm blooded animals. Cats get it from ingestion of infected meat, contamination of food infected with (or direct ingestion of) cat feces, or passed down from mother to unborn offspring. Humans in contact with cats often get infected via slip ups in sanitation at home, or even a cat's unclean claws scratching its owner.
There are some interesting behavior changes that are caused by the disease. Infected rats are less afraid of cats. They also, when infected, are attracted to cat urine. Correlations between infected humans and their changed behavior are (taken from wikipedia)
*Decreased novelty seeking behaviour
* Slower reactions
* Lower rule-consciousness and greater jealousy (in men)
* Promiscuity and greater conscientiousness (in women)
What's interesting here is that the promiscuity in women and jealousy in men actually assists the spread of the parasite through it's effects on our social behavior.
To quote "Effects of Toxoplasma on Human Behavior"
"Consistent and significant differences in Cattell's personality factors were found between Toxoplasma-infected and -uninfected subjects in 9 of 11 studies, and these differences were not the same for men and women. After using the Bonferroni correction for multiple tests, the personality of infected men showed lower superego strength (rule consciousness) and higher vigilance (factors G and L on Cattell's 16PF). Thus, the men were more likely to disregard rules and were more expedient, suspicious, jealous, and dogmatic. The personality of infected women, by contrast, showed higher warmth and higher superego strength (factors A and G on Cattell's 16PF), suggesting that they were more warm hearted, outgoing, conscientious, persistent, and moralistic. Both men and women had significantly higher apprehension (factor O) compared with the uninfected controls."
Flegr J (2007). Effects of toxoplasma on human behavior. Schizophrenia bulletin, 33 (3), 757-60 PMID: 17218612
Next time you see someone with these symptoms (or notice them in your own behavior), take a second to wonder if it might just be the result of a parasite that has infected half the human race.
Article on University of Chicago Medical Center, this is the breaking news about the vaccine
Article on Wikipedia
Older, Entertaining Article on ABC News
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