Research Article: Increased Risk for Entamoeba histolytica Infection and Invasive Amebiasis in HIV Seropositive Men Who Have Sex with Men in Taiwan

Date Published: February 27, 2008

Publisher: Public Library of Science

Author(s): Chien-Ching Hung, Dar-Der Ji, Hsin-Yun Sun, Ya-Tien Lee, Shui-Yuan Hsu, Sui-Yuan Chang, Cheng-Hsin Wu, Yun-Hsien Chan, Chin-Fu Hsiao, Wen-Chun Liu, Robert Colebunders, Alok Bhattacharya

Abstract: BackgroundIncidence of Entamoeba histolytica infection and clinical manifestations and treatment response of invasive amebiasis (IA) in HIV-infected patients have rarely been investigated before.Methodology/Principal FindingsAt the National Taiwan University Hospital, medical records of HIV-infected patients who received a diagnosis of IA between 1994 and 2005 were reviewed. The incidence of amebiasis was investigated in serial blood and stool samples from 670 and 264 HIV-infected patients, respectively, using serological and specific amebic antigen assays. DNA extracted from stool samples containing E. histolytica were analyzed by PCR, sequenced, and compared. Sixty-four (5.8%) of 1,109 HIV-infected patients had 67 episodes of IA, and 89.1% of them were men having sex with men (MSM). The CD4 count at diagnosis of IA was significantly higher than that of the whole cohort (215 cells/µL vs. 96 cells/µL). Forty episodes (59.7%) were liver abscesses, 52 (77.6%) colitis, and 25 (37.3%) both liver abscesses and colitis. Fever resolved after 3.5 days of metronidazole therapy (range, 1–11 days). None of the patients died. The incidence of E. histolytica infection in MSM was higher than that in other risk groups assessed by serological assays (1.99 per 100 person-years [PY] vs. 0 per 100 PY; p<0.0001) and amebic antigen assays (3.16 per 100 PY vs. 0.68 per 100 PY; p = 0.12). In multiple logistic regression analysis, only MSM was significantly associated with acquisition of E. histolytica infection (adjusted odds ratio, 14.809; p = 0.01). Clustering of E. histolytica isolates by sequencing analyses from geographically-unrelated patients suggested person-to-person transmission.Conclusions/SignificanceHIV-infected MSM were at significantly higher risk of amebiasis than patients from other risk groups. Despite immunosuppression, amebic liver abscesses and colitis responded favorably to treatment.

Partial Text: Invasive amebiasis (IA) is the second most common cause of mortality due to parasite infections worldwide, accounting for 40,000 to 100,000 deaths annually. High risk populations for developing IA include infants, pregnant women, and patients who are taking immunosuppressives [1],[2]. Interestingly, IA has not been considered to occur at a higher frequency in HIV-infected patients [3],[4]. In industrialized countries, the rare occurrence of IA in HIV-infected patients or persons at risk for HIV infection is probably attributed to the rare intestinal carriage of E. histolytica[4]–[9]. This is in contrast with the relatively frequent carriage of the non-pathogenic E. dispar among men who have sex with men (MSM) who attend sexually transmitted diseases clinics [10]–[13]. In a retrospective review of medical records of more than 34,000 HIV-infected patients in the US [9], 111 (0.3%) patients were diagnosed as having E. histoytica or E. dispar infection, and only 2 had extra-intestinal amebiasis. Amebiasis was significantly more prevalent among MSM and patients from E. histolytica endemic areas. However, the interpretation of the results of this study is limited by the retrospective study design and failure to differentiate between E. histolytica and E. dispar[14].

This is the first longitudinal follow-up study to investigate the incidence of E histolytica infection in HIV-infected patients by examining the incidence rate of intestinal E. histolytica infection and seroconversion of anti-E. histolytica antibodies. We found that HIV-infected MSM were at significantly higher risk for acquisition of E. histolytica infection [31],[34]. Despite immunosuppression from HIV infection and the complicated disease course of IA, clinical responses to metronidazole therapy were favorable in terms of rapid defervescence and a low attributable mortality rate.



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