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Presence of Toxoplasma gondii tissue cysts in human semen: Toxoplasmosis as a potential sexually transmissible infection

  • Wen Han Tong
    Affiliations
    School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
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  • Jana Hlaváčová
    Affiliations
    Department of Philosophy and History of Science, Faculty of Science, Charles University, Viničná 7, CZ – 128 44 Prague, Czechia
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  • Author Footnotes
    1 Current Affiliation: Department of Neurology and Weill Institute for Neurosciences, University of California, San Francisco, CA 94158, USA.
    Samira Abdulai-Saiku
    Footnotes
    1 Current Affiliation: Department of Neurology and Weill Institute for Neurosciences, University of California, San Francisco, CA 94158, USA.
    Affiliations
    School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
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  • Šárka Kaňková
    Affiliations
    Department of Philosophy and History of Science, Faculty of Science, Charles University, Viničná 7, CZ – 128 44 Prague, Czechia
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  • Jaroslav Flegr
    Affiliations
    Department of Philosophy and History of Science, Faculty of Science, Charles University, Viničná 7, CZ – 128 44 Prague, Czechia
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  • Ajai Vyas
    Correspondence
    Corresponding author at: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
    Affiliations
    School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
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  • Author Footnotes
    1 Current Affiliation: Department of Neurology and Weill Institute for Neurosciences, University of California, San Francisco, CA 94158, USA.
Published:November 05, 2022DOI:https://doi.org/10.1016/j.jinf.2022.10.034

      Highlights

      • Toxoplasma gondii is a widely prevalent infection in humans.
      • Toxoplasma gondii cysts are found in ejaculates of immune-competent human volunteers.
      • Toxoplasma gondii is potentially sexually transmissible, a possibility that requires further epidemiological testing.

      Summary

      Objectives

      Toxoplasma gondii is a widely prevalent protozoan parasite in human populations. This parasite is thought to be primarily transmitted through undercooked meat and contamination by cat feces. Here, we seek to determine if Toxoplasma gondii cysts can be found within human semen.

      Methods

      We used a mixture of histological and immunofluorescence stains to visualize Toxoplasma gondii cysts in thin smears of human semen. Further, we probed for presence of bradyzoite-specific mRNA transcription using in-situ hybridization.

      Results

      We visualized Toxoplasma gondii cysts in ejaculates of immune-competent and latently infected human volunteers. We confirmed the encystment by probing transcription of a bradyzoite-specific gene in these structures. These observations extend previous observations of the parasite in semen of several non-human host species, including rats, dogs, and sheep.

      Conclusions

      Toxoplasma gondii infection is a clinically significant infection, in view of its high prevalence, its purported role in neuropsychiatric disorders such as schizophrenia, as well as in the more serious form of congenital toxoplasmosis. Our demonstration of intact Toxoplasma gondii cysts in the ejaculate supports the possibility of sexual transmission of the parasite and provides an impetus for further investigations.

      Keywords

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