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Although latent infection with Toxoplasma gondii is among the most prevalent of human infections, it has been generally assumed that, except for congenital transmission, it is asymptomatic. The demonstration that latent Toxoplasma infections can alter behavior in rodents has led to a reconsideration of this assumption. When infected human adults were compared with uninfected adults on personality questionnaires or on a panel of behavioral tests, several differences were found. Other studies have demonstrated reduced psychomotor performance in affected individuals. Possible mechanisms by which T. gondii may affect human behavior include its effect on dopamine and on testosterone. Since 1992, a series of studies have been carried out in the Czech Republic comparing the personality characteristics of individuals who have anamnestic antibodies to T. gondii, and are thus assumed to have a latent infection, and those without such antibodies. The personality questionnaires used in these studies have been Cattell's 16-personality factor (16PF) questionnaire2–6 and Cloninger's Temperament and Character Inventory (TCI) personality test.7,8The subjects tested with Cattell's 16PF have included students and faculty in the Department of Biology at Charles University (n = 243, 200, 107, and 255 in various studies), military conscripts (n = 475), blood donors (n = 55, 268, 190), individuals known to have had symptomatic toxoplasmosis in the past (n = 190 and 230), and women tested for toxoplasmosis during pregnancy (n = 191). 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. more.....http://schizophreniabulletin.oxfordjournals.org/content/33/3/757.full
Toxoplasma gondii is not an alien; it is a relative of that down-to-earth pathogen Plasmodium, the beast that causes malaria. It is common: in some parts of the world as much as 60% of the population is infected with it. And it can harm fetuses and people with AIDS, because in each case their immune systems cannot cope with it. For other people, though, the symptoms are usually no worse than a mild dose of flu. Not much for them to worry about, then. Except that there is a growing body of evidence that some of those people have their behaviour permanently changed.One reason to suspect this is that a country’s level of Toxoplasma infection seems to be related to the level of neuroticism displayed by its population. Another is that those infected seem to have poor reaction times and are more likely to be involved in road accidents. A third is that they have short attention spans and little interest in seeking out novelty. A fourth, possibly the most worrying, is that those who suffer from schizophrenia are more likely than those who do not to have been exposed to Toxoplasma.Nor is any of this truly surprising. For, besides humans, Toxoplasma has two normal hosts: rodents and cats. And what it does to rodents is very odd indeedmore....http://www.economist.com/node/16271339
