PURPOSE: Toxoplasma gondii is one of the most widespread parasites in the human population globally. Several modes of its transmission have been proposed: some are well-researched and confirmed, others remain unconfirmed. One unconfirmed hypothesis pertains to potential transmission of Toxoplasma gondii via oral sex (fellatio) in humans. A recent study found tissue cysts in the semen of men with latent toxoplasmosis. Therefore, we aimed to test the hypothesis of Toxoplasma gondii transmission through oral sex experimentally. METHODS: Eighty-two laboratory mice were orally administered semen samples from 41 men with latent toxoplasmosis. These semen samples were examined for the presence of Toxoplasma gondii DNA using PCR. RESULTS: We detected Toxoplasma gondii DNA in three of the 41 semen samples from men with latent toxoplasmosis. Oral administration of semen samples to laboratory mice did not result in parasite transmission. CONCLUSION: We have not demonstrated the transmission of Toxoplasma to mice by oral exposure to semen from infected men. While this does not conclusively rule out the possibility of such transmission in humans, the results suggest that, if it does occur, this mode of transmission is likely infrequent.

Centre for Assisted Reproduction Department of Gynaecology Obstetrics and Neonatology 1st Faculty of Medicine Charles University and General University Hospital Prague Prague Czech Republic

Department of Philosophy and History of Science Faculty of Science Charles University Prague Czech Republic

National Reference Laboratory for Toxoplasmosis National Institute of Public Health Prague Czech Republic

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Beyond Latency: Chronic Toxoplasma Infection and Its Unveiled Behavioral and Clinical Manifestations-A 30-Year Research Perspective

Special Issue: Re-assessing host manipulation in Toxoplasma: the underexplored role of sexual transmission - evidence, mechanisms, implications