The Toxoplasma gondii parasite is carried by an estimated 30 percent of all humans but is considered a relatively harmless infection. New research published in the journal Evolutionary Psychology, however, suggests that toxoplasmosis can make people more interested in nonconventional sexual practices like bondage.

In the study, Czech researchers compared 212 Toxoplasma-infected men and 529 Toxoplasma-infected women with 2,470 Toxoplasma-free men and 2,617 Toxoplasma-free women. They found that Toxoplasma-infected individuals expressed higher attraction to nonconventional sexual practices. But Toxoplasma-infected individuals also reported performing these activities less often than the Toxoplasma-free individuals.

In particular, Toxoplasma-infected individuals were more aroused by bondage, violence, zoophilia, and fetishism than Toxoplasma-free individuals.

While the difference between Toxoplasma-infected and Toxoplasma-free individuals was statistically significant, the researchers noted that the overall difference between the two groups was not large.

PsyPost interviewed Jaroslav Flegr of Charles University in Prague. Read his explanation of the research below:

PsyPost: Why were you interested in this topic?

Jaroslav: Toxoplasma gondii, the parasite that needs to get from infected mice to a cat by predation, is able to induce so called fatal attraction phenomenon in infected rodents. Normally, mice and rats try to avoid places where they smell cat urine. Infected rodents, however, are attracted to these places. Recent results of a study performed in Singapore showed that Toxoplasma induces this behaviour by demethylation of regulation sequences of certain genes in amygdala. After this, the stimuli that normally activate fear-related circuits start to activate also sex-related circuits. Based on these results, we tested the hypothesis that Toxoplasma-infected subjects will be sexually aroused by BDSM stimuli more often than Toxoplasma-free subjects.

What should the average person take away from your study?

Toxoplasma-infected men are more sexually aroused by masochistic stimuli including bondage than Toxoplasma-free men. However, both the infected men and women are less sexually active and practice more conventional sexual activities than Toxoplasma-free subjects.

Are there any major caveats? What questions still need to be addressed?

The subjects self-reported their sexual preferences and sexual activity. It will be necessary to confirm our result using more objective methods, such as plethysmography and fNMR.

Is there anything else you would like to add?

Toxoplasma probably changes sexual behaviour of its human host. Some changes, such as increased affinity to BDSM observed in the infected men, are related to manipulative activity of the parasite that needs to get from its intermediate host to the stomach of a definitive host. Most of the observed behavioural changes (including the decrease of sexual activities of men and women) are, however, rather side-effects of an impaired health status of the infected subjects. Therefore, lifelong “asymptomatic” latent toxoplasmosis probably represents a serious and underrated public health problem.

The study, “The Relation of Toxoplasma Infection and Sexual Attraction to Fear, Danger, Pain, and Submissiveness,” was also co-authored by Radim Kuba.