Induction of changes in human behaviour by the parasitic protozoanToxoplasma gondii

Abstract

Toxoplasma gondii, the coccidian parasite, is known to induce changes in the behaviour of its intermediate hosts. The high prevalence of this parasite in the human population (20-80%) offers the opportunity of studying the influence of the parasite on human behaviour by screening of a normal population. A total of 224 men and 170 women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma-infected and uninfected subjects were observed (P < 0.01). For men the factors G (low superego strength), L (protension), O (guilt proneness), and Q2 (group dependency) were positively influenced in infected subjects. For women the prevailing factors were A (affectothymia, P < 0.01), L (alaxia), O (untroubled adequacy) and Q2 (self-sufficiency). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (P < 0.02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.

Effects of Toxoplasma gondii infection on anxiety, depression and ghrelin level in male rats

“…In male LongEvans rats, Latent Toxoplasma infection resulted to reduced the normal aversion to cat odor and converted it into a mild attraction (Vyas et al 2007). Flegr et al (1996) reported personality profiles such as, superego strength (the willingness to accept group moral standards) were significantly different between Toxoplasma-infected and uninfected subjects. In a populationbased study, association of Toxoplasma-specific immunoglobulin G results with mood disorder outcomes in 7,440 respondents was assessed.…”

Influence of latent "asymptomatic" toxoplasmosis on body weight of pregnant women

“…Results showed that differences probably exist in the weight of Toxoplasma-negative and Toxoplasma-positive women (see the first row of Table 2). The effect of latent toxoplasmosis can be expected to increase with the length of Toxoplasma infection (Flegr et al 1996. The moment of Toxoplasma infection is usually not known for most subjects with latent toxoplasmosis.…”

“…However, despite an extremely high prevalence of this form of toxoplasmosis in many countries, only minimal attention is paid to the study of its potential impact on human health (Holliman 1997). Certain studies demonstrate possible correlation of latent toxoplasmosis with some types of brain tumours (Ryan et al 1993) or with specific changes in personality profiles of infected subjects (Flegr et al 1996, 2003, Flegr and Havlíček 1999. Our results, namely, decreased body weight of Toxoplasma-positive pregnant women (and possibly also decreased growth rate of the foetus), suggest that latent toxoplasmosis might in some way negatively affect the health of infected subjects.…”

“…Recently, latent-toxoplasmosis-associated changes in human personality were observed and interpreted as the result of manipulation activity of the parasite (Flegr et al 1996, 2003, Flegr and Havlíček 1999. This widely documented (Hutchison et al 1980a, b, Arnott et al 1990, Webster 1994, Berdoy et al 1995, Hrdá et al 2000) activity of Toxoplasma is seemingly aimed at inducing behavioural changes in the intermediate host (under natural conditions, a rodent) that can increase the probability of being killed and eaten by a definitive host (cat).…”

Schizophrénie et toxoplasmose

“…Les résultats des modèles murins d'infection latente ont encouragé la recherche de corrélats comportementaux à l'infection latente chez l'homme. Ainsi des études cliniques ont trouvé des profils de personnalité différents entre les sujets présentant une infection latente et les sujets sains [30]. D'autres études ont aussi montré un quotient intellectuel plus faible chez les sujets infectés [31], ou encore des performances psychomotrices altérées [32].…”