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

Background Amebiasis, which is caused by Entamoeba histolytica, is a
re-emerging public health issue owing to sexually transmitted infection
(STI) in Japan. However, epidemiological data are quite limited. Methods
To reveal the relative prevalence of sexually transmitted E. histolytica
infection to other STIs, we conducted a cross-sectional study at a
voluntary counselling and testing (VCT) centre in Tokyo. Seroprevalence of
E. histolytica was assessed according to positivity with an enzyme-linked
immunosorbent assay for E. histolytica-specific IgG in serum samples
collected from anonymous VCT clients. Results Among 2,083 samples,
seropositive rate for E. histolytica 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 Chlamydia
trachomatis in urine by transcription-mediated amplification (TMA) was
4.59%. Seropositivity for E. histolytica 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 E. histolytica and RPR were high among male clients. The seropositive
rate for anti-E. histolytica antibody was positively correlated with age.
TMA positivity for urine C. trachomatis 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
E. histolytica seropositivity. Conclusions Seroprevalence of E.
histolytica 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- 65 emerging pathogen.