Seroprevalence of Entamoeba histolytica at a voluntary counselling and testing centre in Tokyo: a cross-sectional study

<p><strong>Background</strong> Amebiasis, which is caused by <em>Entamoeba histolytica</em>, is a re-emerging public health issue owing to sexually transmitted infection (STI) in Japan. However, epidemiological data are quite limited.<br> <strong>Methods</strong> To reveal the relative prevalence of sexually transmitted <em>E. histolytica</em> infection to other STIs, we conducted a cross-sectional study at a voluntary counselling and testing (VCT) centre in Tokyo. Seroprevalence of <em>E. histolytica</em> was assessed according to positivity with an enzyme-linked immunosorbent assay for <em>E. histolytica</em>-specific IgG in serum samples collected from anonymous VCT clients.<br> <strong>Results</strong> Among 2,083 samples, seropositive rate for <em>E. histolytica</em> was 2.64%, which was higher than that for HIV-1 (0.34%, p &lt; 0.001) and comparable to that for syphilis (rapid plasma reagin (RPR) 2.11%, p = 0.31). Positivity for <em>Chlamydia trachomatis</em> in urine by transcription-mediated amplification (TMA) was 4.59%. Seropositivity for <em>E. histolytica</em> was high among RPR- or Treponema pallidum hemagglutination (TPHA)-positive individuals and it was not different between clients with and without other STIs. Both seropositivity of <em>E. histolytica</em> and RPR were high among male clients. The seropositive rate for anti-<em>E. histolytica</em> antibody was positively correlated with age. TMA positivity for urine <em>C. trachomatis</em> was high among female clients and negatively correlated with age. Regression analysis identified that male sex, older age, and TPHA-positive results are independent risk factors of <em>E. histolytica</em> seropositivity.<br> <strong>Conclusions</strong> Seroprevalence of <em>E. histolytica</em> was 7.9 times higher than that of HIV-1 at a VCT centre in Tokyo, with a tendency to be higher among people at risk for syphilis infection. There is a need for education and specific interventions against this parasite, as a potentially re-<br> 65 emerging pathogen.</p>