Seroprevalence of <i>Entamoeba histolytica</i> at a voluntary counselling and testing centre in Tokyo: a cross-sectional study.

Abstract

Amebiasis, which is caused by <i>Entamoeba histolytica</i>, is a re-emerging public health issue owing to sexually transmitted infection (STI) in Japan. However, epidemiological data are quite limited. To reveal the relative prevalence of sexually transmitted <i>E. histolytica</i> infection to other STIs, we conducted a cross-sectional study at a voluntary counselling and testing (VCT) centre in Tokyo. Seroprevalence of <i>E. histolytica</i> was assessed according to positivity with an ELISA for <i>E. histolytica</i>-specific IgG in serum samples collected from anonymous VCT clients. Among 2083 samples, seropositive rate for <i>E. histolytica</i> was 2.64%, which was higher than that for HIV-1 (0.34%, p<0.001) and comparable to that for syphilis (rapid plasma reagin (RPR) 2.11%, p=0.31). Positivity for <i>Chlamydia trachomatis</i> in urine by transcription-mediated amplification (TMA) was 4.59%. Seropositivity for <i>E. histolytica</i> was high among RPR/<i>Treponema pallidum</i> hemagglutination (TPHA)-positive individuals and it was not different between clients with and without other STIs. Both seropositivity of <i>E. histolytica</i> and RPR were high among male clients. The seropositive rate for anti-<i>E. histolytica</i> antibody was positively correlated with age. TMA positivity for urine <i>C. trachomatis</i> 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 <i>E. histolytica</i> seropositivity. Seroprevalence of <i>E. histolytica</i> 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-emerging pathogen.