Influence of Toxoplasma gondii Infection on Male Fertility: A Pilot Study on Immunocompetent Human Volunteers

Background: This study was conducted to investigate the influence of Toxoplasma gondii infection on spermatic and hormonal parameters in a pilot sample of immunocompetent human male subjects. Methods: This cross sectional, observational pilot study on 60 immunocompetent human male subjects aged between 18 and 60 yr old was conducted between 2012 -2013. Blind evaluation of serological markers of past T. gondii infection (TOX-IgG, TOX-IgM) was performed, along with individual spermiograms and determinations of follicle-stimulating hormone (FSH) and testosterone serum levels. Results: The overall prevalence of past T. gondii infection in the investigated immunocompetent male subjects was 25%. No statistically significant influence of T. gondii infection on sperm characteristics (ejaculate quantity, sperm count, motility, morphology) and serum levels of FSH or testosterone were found. Among possible predictors of a modified spermiogram studied by multiple logistic regression along with the T. gondii infection (age, smoking, alcohol consumption, fertility influencing malformations, infections, trauma or medication), only the presence of varicocele in the medical history of the studied subjects was found to significantly participate in the prediction of a modified spermiogram (P=0.0154). A necessary sample size of 994 subjects was computed in order to achieve a test power of 0.8 (80%) to discriminate an effect size of 8.89% estimated by our pilot study. Conclusions: Although our investigation did not demonstrate an influence of latent T. gondii infection on spermatic and hormonal parameters of immunocompetent male humans, the absence of such an influence cannot be affirmed, due to the limited sample size of our pilot study.