Abstract
The parasitic protozoon Toxoplasma gondii infects about one third of the population of developed countries. The life-long presence of dormant stages of this parasite in the brain and muscular tissues of infected humans is usually considered asymptomatic from the clinical point of view.
In the past twenty years, the research performed mostly on military personnel, university students, pregnant women and blood donors has shown that this "asymptomatic" disease has a large influence on various aspects of human life. Toxoplasma-infected subjects differ from uninfected controls in the personality profile estimated with two versions of Cattell's 16PF, Cloninger's TCI and Big Five questionnaires.
Most of these differences increase with the duration of infection, suggesting that Toxoplasma influences human personality rather than that human personality influences the probability of the infection. Toxoplasma-infected and Toxoplasma-free subjects also differ in the behaviour as observed in various ethological experiments and in the strategies they use in experimental games.
Toxoplasmosis increases the reaction time of infected subjects, which can explain the increased probability of traffic accidents in infected subjects reported in three retrospective and one very large prospective case-control studies.