Induction of changes in human behaviour by the parasitic protozoanToxoplasma gondii

Abstract

SUMMARYToxoplasma 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 betweenToxoplasma-infected and uninfected subjects were observed (P< 0·01). For men the factorsG(low superego strength),L(protension),O(guilt proneness), andQ2(group dependency) were positively influenced in infected subjects. For women the prevailing factors wereA(affectothymia,P< 0·01),L(alaxia),O(untroubled adequacy) andQ2(self-sufficiency). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiringToxoplasmainfection, 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 byT. gondiiinfection.