Flegr J. Effects of toxoplasma on human behavior. Schizophrenia Bulletin, 2007, 33, 3, 757-760.
“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.”
Kanková S, Sulc J, Nouzová K, Fajfrlík K, Frynta D, Flegr J. Women infected with parasite Toxoplasma have more sons. Naturwissenschaften, 2007, 2, 122-127.
“The results of our retrospective cohort study suggest that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii, can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72, C.I.95 = (0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of anti-Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be responsible for the enhanced survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis on the human population might be considerable.”
Kanková S, Kodym P, Frynta D, Vavrinová R, Kubena A, Flegr J. Influence of latent toxoplasmosis on the secondary sex ratio in mice. Parasitology, 2007, 134, 12, 1709-1717.
“Here we studied the sex ratio of experimentally infected laboratory mice, expressed here as the proportion of males in the litter. In accordance with our hypothesis and results of previous retrospective cohort studies on human subjects, mice with toxoplasmosis produced a higher sex ratio than controls, in the early phase of latent infection. In the later phase of infection, mice with congenital toxoplasmosis had a lower sex ratio than controls”
Flegr J. Influence of latent Toxoplasma infection on human personality, physiology and morphology: pros and cons of the Toxoplasma-human model in studying the manipulation hypothesis. Journal of Experimental Biology, 2013, 216, 1, 127-133.
“In the past 20 years, 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 length of time since the onset of infection, suggesting that Toxoplasma influences human personality rather than human personality influencing the probability of infection. 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 study. Latent toxoplasmosis is associated with immunosuppression, which might explain the increased probability of giving birth to a boy in Toxoplasma-infected women and also the extremely high prevalence of toxoplasmosis in mothers of children with Down syndrome. Toxoplasma-infected male students are about 3 cm taller than Toxoplasma-free subjects and their faces are rated by women as more masculine and dominant. These differences may be caused by an increased concentration of testosterone. Toxoplasma also appears to be involved in the initiation of more severe forms of schizophrenia.”
Rodriguez T. Common Parasite Linked to Personality Changes: Eating a raw steak or owning a cat can make you more outgoing. Scientific American Mind. September 1, 2012.
“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.”
Stock AK, Dajkic D, Köhling HL, von Heinegg EH, Fiedler M, Beste C. Humans with latent toxoplasmosis display altered reward modulation of cognitive control. Scientific Reports, 2017, 7, 1, 10170.
“Latent infection with Toxoplasma gondii has repeatedly been shown to be associated with behavioral changes that are commonly attributed to a presumed increase in dopaminergic signaling … Taken together, individuals with latent toxoplasmosis show superior behavioral performance in challenging cognitive control situations but may at the same time have a reduced sensitivity towards motivational effects of rewards, which might be explained by the presumed increase in dopamine.”
Stepanova EV, Kondrashin AV, Sergiev VP, Morozova LF, Turbabina NA, Maksimova MS, et al. Significance of chronic toxoplasmosis in epidemiology of road traffic accidents in Russian Federation. PLoS ONE, 201712, 9, e0184930.
“Our findings also demonstrated a statistically significant relationship between the rate of traffic accidents and the seroprevalence of chronic toxoplasmosis in drivers who were held responsible for accidents. The latter was 2.37 times higher in drivers who were involved in road accidents compared with control groups. These results suggest that the consequences of chronic toxoplasmosis (particularly a slower reaction time and decreased concentration) might contribute to the peculiarities of the epidemiology of road traffic accidents in the Russian Federation …”
Lu J. How a parasitic fungus turns ants into ‘zombies.’ National Geographic Hostile Planet. April 18, 2019.
“The Ophiocordyceps unilateralis fungus has just one goal: self-propagation and dispersal. Researchers think the fungus, found in tropical forests, infects a foraging ant through spores that attach and penetrate the exoskeleton and slowly takes over its behavior. As the infection advances, the enthralled ant is compelled to leave its nest for a more humid microclimate that’s favorable to the fungus’s growth. The ant is compelled to descend to a vantage point about 10 inches off the ground, sink its jaws into a leaf vein on the north side of a plant, and wait for death. Meanwhile, the fungus feeds on its victim’s innards until it’s ready for the final stage. Several days after the ant has died, the fungus sends a fruiting body out through the base of the ant’s head, turning its shriveled corpse into a launchpad from which it can jettison its spores and infect new ants.”