Amebic liver abscess in HIV-infected patients, Republic of Korea

Amebiasis as a sexually transmitted infection: A re-emerging health problem in developed countries

Amebiasis, which is caused by Entamoeba histolytica (E. histolytica), is the second leading cause of parasite-related death worldwide. It manifests from asymptomatic carriers to severe clinical conditions, like colitis and liver abscesses. Amebiasis is commonly seen in developing countries, where water and food are easily contaminated by feces because of the poor sanitation. However, a recently challenge in many developed countries is the increase in domestic cases of invasive amebiasis as a sexually transmitted infection (STI amebiasis). In contrast to food-/ waterborne transmission of E. histolytica in developing countries, transmission of STI amebiasis occurs directly through human-to-human sexual contact (e.g., men who have sex with men and people who engage in oral-anal sex); in this setting, asymptomatic infected individuals are the main reservoir of E. histolytica. The Development of screening methods for the early diagnosis of asymptomatic E. histolytica infection is the key to epidemiologic control. Moreover, delay in diagnosis of severe cases (e.g., fulminant amebiasis) leads to death even in developed countries. It is also important to increase clinical awareness of domestically transmitted STI amebiasis in the clinical settings. This review considers the changing epidemiology and clinical manifestations of STI amebiasis, and finally discusses the future strategies for the better practice.

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 ELISA for E. histolytica-specific IgG in serum samples collected from anonymous VCT clients.

RESULTS

Among 2083 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/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-emerging pathogen.

History of Acquired Immune Deficiency Syndrome in Korea

The first human immunodeficiency virus (HIV) infection was reported in Korea in 1985. The number of HIV-infected persons domestically increased in the 1990s showing epidemic indigenousization. Since then, the number of new infections gradually increased every year, and recently more than 1,000 newly infected cases were reported per year. A total of 12,522 infected individuals have been reported up to 2015, of which 2,020 died. The male to female ratio was 15.4:1, and 34.2% of them were under 30 years old. The infection route was homosexual and bisexual contact in 60.1% of cases and heterosexual contact in 34.6% of cases. Candidiasis, Pneumocystis pneumonia, tuberculosis were common as a AIDS (acquired immune deficiency syndrome)-defining illness. But with the introduction of antiretroviral therapy in the late 1990s, non-AIDS defining illnesses such as metabolic complications, cardiovascular diseases, bone diseases, and neuropsychiatric disorders such as neurocognitive dysfunction, depression, and anxiety are emerging as new health problems. The management policy switched its focus from regulating and monitoring of HIV-infected persons to ensuring access to treatment and promotion of voluntary HIV testing in high-risk groups. Also as the age of the infected persons increases, a need for various supports such as social rehabilitation, life counseling, and welfare has emerged.

Recent epidemiology of sexually transmissible enteric infections in men who have sex with men

PURPOSE OF REVIEW

Sexual transmission of enteric pathogens in men who have sex with men (MSM) has been described since the 1970s. Recently, an increasing number of enteric infection outbreaks have been reported in MSM. This article summarizes recent outbreaks and discusses the key issues for prevention and control.

RECENT FINDINGS

Sexually transmissible enteric infections (STEIs) can spread rapidly and internationally within highly connected MSM populations and are often associated with antimicrobial resistance (AMR). The infections often cluster in high-risk groups of HIV-positive MSM who are more likely to engage in diverse sexual practices and chemsex, and to have multiple other sexually transmitted infections (STIs).

SUMMARY

The roles of asymptomatic and/or persistent infection and other contextual factors in STEI transmission are not well described. STEI-associated AMR is increasing and has potential to spread rapidly in MSM, warranting further public health attention. A better understanding of the factors associated with sexual transmission will enable the development of more effective control measures. A holistic approach that promotes health and wellbeing as well as infection prevention and management is needed.

Antiamoebic drugs for treating amoebic colitis

BACKGROUND

Infection with the protozoan Entamoeba histolytica is common in low- and middle-income countries, and up to 100,000 people with severe disease die every year. Adequate therapy for amoebic colitis is necessary to reduce illness, prevent development of complicated disease and extraintestinal spread, and decrease transmission.

OBJECTIVES

To evaluate antiamoebic drugs for treating amoebic colitis.

SEARCH METHODS

We searched the available literature up to 22 March 2018. We searched the Cochrane Infectious Diseases Group Specialised Register, CENTRAL, MEDLINE, Embase, LILACS, mRCT, and conference proceedings. We contacted individual researchers, organizations, and pharmaceutical companies, and we checked reference lists.

SELECTION CRITERIA

Randomized controlled trials of antiamoebic drugs given alone or in combination, compared with placebo or another antiamoebic drug, for treating adults and children with a diagnosis of amoebic colitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility and methodological quality of trials and extracted and analysed the data. We calculated clinical and parasitological failure rates and rates of relapse and adverse events as risk ratios (RRs) with 95% confidence intervals (CIs), using a random-effects model. We determined statistical heterogeneity and explored possible sources of heterogeneity using subgroup analyses. We carried out sensitivity analysis by using trial quality to assess the robustness of reported results.

MAIN RESULTS

In total, 41 trials (4999 participants) met the inclusion criteria of this review. In this update, we added four trials to the 37 trials included in the first published review version. Thirty trials were published over 20 years ago. Only one trial used adequate methods of randomization and allocation concealment, was blinded, and analysed all randomized participants. Only one trial used an E histolytica stool antigen test, and two trials used amoebic culture.Tinidazole may be more effective than metronidazole for reducing clinical failure (RR 0.28, 95% CI 0.15 to 0.51; 477 participants, eight trials; low-certainty evidence) and is probably associated with fewer adverse events (RR 0.65, 95% CI 0.46 to 0.92; 477 participants, 8 trials; moderate-certainty evidence). Compared with metronidazole, combination therapy may result in fewer parasitological failures (RR 0.36, 95% CI 0.15 to 0.86; 720 participants, 3 trials; low-certainty evidence), but we are uncertain which combination is more effective than another. Evidence is insufficient to allow conclusions regarding the efficacy of other antiamoebic drugs.

AUTHORS' CONCLUSIONS

Compared with metronidazole, tinidazole may be more effective in reducing clinical failure and may be associated with fewer adverse events. Combination drug therapy may be more effective for reducing parasitological failure compared with metronidazole alone. However, these results are based mostly on small trials conducted over 20 years ago with a variety of poorly defined outcomes. Tests that detect E histolytica more accurately are needed, particularly in countries where concomitant infection with other bacteria and parasites is common.

Amoebic Liver Abscess and Indigenous Alcoholic Beverages in the Tropics

Amoebic liver abscess (ALA) seen commonly in the tropics is predominantly confined to adult males, especially those who consume locally brewed alcohol, although intestinal amoebiasis occurs in all age groups and in both genders. Whether the role of alcohol in the development of ALA is incidental and casual or whether alcohol is causally implicated has been debated. It has been argued that socioeconomic factors and poor sanitary conditions are the primary culprits that casually link alcohol to ALA. However, there has emerged an abundance of data that implicates alcohol in a more causal role in facilitating the extraintestinal invasion of the infective protozoan and the subsequent development of ALA. These factors include the role of alcohol in host immunity, parasitic proliferation, and invasion and in creating a conducive hepatic microenvironment. The contributory role of alcohol-induced increase in hepatic iron stores and lipid content is discussed. Late-stage liver disease with fibrosis seems to be protective for the development of ALA. Further research is necessary to elucidate the many possible mechanisms that predispose to hepatic amoebiasis, so that appropriate individual and population-based preventive measures can be implemented.

Amoeboma in a Saudi resident: a case report

Introduction:

Amoebiasis is the third most frequent cause of mortality after malaria and schistosomiasis. In developed countries, amebiasis is also seen in migrants who have travelled to endemic areas. The factors responsible for its progression from intestinal amebiasis to an amebic liver abscess are not fully understood.

Case presentation:

A 54-year-old man presented with abdominal pain, fever and diarrhoea. Laparotomy confirmed an inflammatory mass involving the right colon, and he underwent a right hemicolectomy. He later developed abdominal distenstion due to an amoebic liver abscess and died from secondary nosocomial bacterial infection and surgical complications.

Conclusion:

Amoeboma is an uncommon manifestation of amoebiasis, and can mimic both carcinoma and inflammatory bowel disease; so, distinguishing between these two conditions is the key to providing appropriate therapy. Hepatic amoebiasis is the most common extraintestinal disease of invasive amoebiasis. This clinical report presents a case of an uncommon parasitic disease in Saudi Arabia and discusses the difficulties encountered while attempting to establish the correct diagnosis. Hence, a high index of suspicion is crucial for diagnosing Entamoeba histolytica to avoid unnecessary surgery and further complications.

Underestimated Amoebic Appendicitis among HIV-1-Infected Individuals in Japan

Entamoeba histolytica is not a common causative agent of acute appendicitis. However, amoebic appendicitis can sometimes be severe and life threatening, mainly due to a lack of awareness. Also, its frequency, clinical features, and pathogenesis remain unclear. The study subjects were HIV-1-infected individuals who presented with acute appendicitis and later underwent appendectomy at our hospital between 1996 and 2014. Formalin-fixed paraffin-embedded preserved appendix specimens were reexamined by periodic acid-Schiff (PAS) staining and PCR to identify undiagnosed amoebic appendicitis. Appendectomies were performed in 57 patients with acute appendicitis. The seroprevalence of E. histolytica was 33% (14/43) from the available stored sera. Based on the medical records, only 3 cases were clinically diagnosed as amoebic appendicitis, including 2 diagnosed at the time of appendectomy and 1 case diagnosed by rereview of the appendix after the development of postoperative complications. Retrospective analyses using PAS staining and PCR identified 3 and 3 more cases, respectively. Thus, E. histolytica infection was confirmed in 9 cases (15.8%) in the present study. Apart from a significantly higher leukocyte count in E. histolytica-positive patients than in negative patients (median, 13,760 versus 10,385 cells/μl, respectively, P = 0.02), there were no other differences in the clinical features of the PCR-positive and -negative groups. In conclusion, E. histolytica infection was confirmed in 9 (15.8%) of the appendicitis cases. However, only 3, including one diagnosed after intestinal perforation, were diagnosed before the present analyses. These results strongly suggest there is frequently a failure to detect trophozoites in routine examination, resulting in an underestimation of the incidence of amoebic appendicitis.

Recent advances in Entamoeba biology: RNA interference, drug discovery, and gut microbiome

In recent years, substantial progress has been made in understanding the molecular and cell biology of the human parasite Entamoeba histolytica, an important pathogen with significant global impact. This review outlines some recent advances in the Entamoeba field in the last five years, focusing on areas that have not recently been discussed in detail: (i) molecular mechanisms regulating parasite gene expression, (ii) new efforts at drug discovery using high-throughput drug screens, and (iii) the effect of gut microbiota on amoebiasis.

Recent progress on the discovery of antiamoebic agents

A large number of protozoans infect humans but Entamoeba histolytica is the only organism responsible for causing amoebiasis, a deadly disease after malaria. Numerous heterocycle-based antiamoebic agents have been previously synthesized as E. histolytica inhibitors and while some of these agents have shown moderate activity, the search for a novel and ideal antiamoebic compound is still ongoing. In this digest Letter, we present the latest data on antiamoebic agents from 2011 to 2016 based on the different classes of heterocyclic agents.

Parasites

Parasites are an important cause of human disease worldwide. The clinical severity and outcome of parasitic disease is often dependent on the immune status of the host. Specific parasitic diseases discussed in this chapter are amebiasis, giardiasis, cryptosporidiosis, cyclosporiasis, cystoisosporiasis, microsporidosis, granulomatous amebic encephalitis, toxoplasmosis, leishmaniasis, Chagas disease, malaria, babesiosis, strongyloidiasis, and scabies.

Molecular biology research to benefit patients with Entamoeba histolytica infection

The development of molecular microbiology has made it possible for us to deepen our understanding of the pathogenesis of amebiasis. Research using the trophozoite form of Entamoeba histolytica has clearly shown us the importance of the interface between the parasite and host cells in vitro. Immuno-pathogenesis after excystation was similarly well advanced by the use of a novel murine model of amebic colitis. However, it is still challenging to apply these findings to clinical and epidemiological settings. This is mainly because of the lack of a complete infection animal model of amebiasis by oral-fecal infection. Moreover, in vitro experiments have predominantly been performed using the same axenic cultured strain HM-1: IMSS isolated about 50 years ago, whereas highly diverse strains are prevalent all over the world. Translational research informed by clinical observations has the greatest potential for the development of effective interventions. Here, we highlight discoveries of the experiments designed from cohort observation and discuss remaining problems to be solved.

Multiple Amoebic Liver Abscess As Initial Manifestation in Hiv Sero-Positive Male

Amoebic liver abscess is the most frequent extra-intestinal manifestation of Entamoeba histolytica infection. Immunosuppression is known to predispose to amoebic liver abscess. Although amoebic liver abscess is seen more commonly in patients of Human-Immunodeficiency virus (HIV), first presentation of HIV sero-positive patient as multiple liver abscess is quite uncommon.The author reports an unusual case of multiple liver abscesses in an HIV seropositive patient. This middle aged male with history of multiple unprotected sexual encounters presented with spasmodic abdominal pain, fever, diarrhoea and weight loss along with generalised ill-health and painful liver enlargement. HIV-1 serology was found to be reactive. Imaging revealed an enlarged liver with multiple, irregular, hypoechoic foci characteristic of abscesses. Amoebic aetiology was later confirmed by percutaneous aspiration and microscopy. Administration of appropriate chemotherapeutics along with institution of antiretroviral therapy led to both clinical resolution as well as disappearance of lesions.

Prevalent and incident HIV diagnoses among Entamoeba histolytica-infected adult males: a changing epidemiology associated with sexual transmission--Taiwan, 2006-2013

Background

Sexually transmitted Entamoeba histolytica infection (EHI) has been increasingly recognized among men who have sex with men (MSM). We used the National Disease Surveillance Systems (NDSS) to identify prevalent and incident HIV diagnoses among adults with EHI and to determine the associated factors.

Methodology

The NDSS collect demographic, clinical, and behavioral characteristics of case patients through physician reports and public health interviews. EHI was confirmed by polymerase-chain-reaction assays, histopathology, or serology with documented liver abscess. We linked NDSS databases to identify prevalent and incident HIV diagnoses among noninstitutionalized Taiwanese adults with confirmed EHI during 2006–2013. Cox proportional-hazards analysis was used to determine associated factors.

Principal findings

Of noninstitutionalized adults with EHI, we identified prevalent HIV diagnosis in 210 (40%) of 524 males and one (1.7%) of 59 females, and incident HIV diagnosis in 71 (23%) of 314 males. MSM accounted for 183 (87%) and 64 (90%) of prevalent and incident HIV diagnoses in males, respectively. From 2006–2009 to 2010–2013, the prevalence of HIV diagnosis increased from 32% to 45% (P = 0.001) while the incidence of HIV diagnosis increased from 5.4 to 11.3 per 100 person-years (P = 0.001) among males with EHI. Incident HIV diagnosis was independently associated with a younger age, residing in metropolitan areas, hospitalization, previous syphilis, and engagement in oral, anal, or oral–anal sex before illness onset.

Conclusions/significance

Prevalent and incident HIV diagnoses were increasingly identified among adult males in Taiwan, preferentially affecting younger urban MSM. Surveillance and risk-reduction interventions are recommended against the interplay of HIV epidemic and sexually transmitted EHI.

Although sexually transmitted Entamoeba histolytica infection has been increasingly recognized among men who have sex with men (MSM) in Australia, Japan, Korea, and Taiwan, particularly those with HIV infection, no studies have examined E. histolytica infection in relation to HIV and attribution of sexual transmission at a national level. We analyzed the national surveillance data in Taiwan and demonstrated that the prevalent and incident HIV diagnoses increased among E. histolytica-infected adult males from 2006–2009 to 2010–2013, which were associated with previous syphilis and engagement of oral, anal, oral–anal sex. The findings indicate sexual transmission might have replaced traditional risk factors as the major route of E. histolytica transmission among adult males in Taiwan. E. histolytica infection associated with prevalent and incident HIV diagnoses preferentially affects younger urban MSM, suggesting new targets of surveillance and public health interventions for this sexually transmissible protozoan infection.

Asymptomatic intestinal amebiasis in Japanese HIV-1-infected individuals

Seventy-one asymptomatic human immunodeficiency virus-1 (HIV-1) -infected individuals who underwent colonoscopy for detection of diseases other than amebiasis were included in this study. Ulcerative lesions caused by Entamoeba histolytica were identified by colonoscopy and biopsy in 11.3% (8 of 71) of individuals. Stool microscopic examination hardly identified Entamoeba, whereas serum antibody against E. histolytica was often elevated in patients with subclinical intestinal amebiasis. Human leukocyte antigen (HLA) class II allele against E. histolytica infection (DQB1*06:01) was frequently identified in these patients. This study emphasizes the endemic nature of E. histolytica infection in our cohort and the difficulties in epidemiological control.

Seroprevalence of Entamoeba histolytica infection among Chinese men who have sex with men

Background

Men who have sex with men (MSM) were found to be one of the high-risk populations for Entamoeba histolytica (E. histolytica) infection. Accompanied by the prevalence of human immunodeficiency virus (HIV) among MSM, invasive amebiasis caused by E. histolytica has been paid attention to as an opportunistic parasitic infection. However, the status of E. histolytica infection among MSM has been barely studied in mainland China.

Methods

Seroprevalance of E. histolytica was determined using an enzyme-linked immunosorbent assay based on a cross-sectional study conducted in Beijing and Tianjin, China. Factors potentially associated with E. histolytica infection were identified by logistic regression analysis.

Results

A total of 602 MSM were included in the study and the laboratory data on serostatus of E. histolytica were available for 599 of them (99.5%). 246 (41.1%) and 51 (8.5%) of the study participants were E. histolytica seropositive and HIV seropositive, respectively. Univariate analyses suggested preferred anal sex behaviors were associated with E. histolytica seropositivity. In multivariate logistic regression analysis, “only has receptive anal sex” (OR: 2.03; 95% CI: 1.22 3.37), “majority receptive anal sex” (OR: 1.83; 95% CI: 1.13, 2.95), and “sadomasochistic behavior (SM)” (OR: 2.30; 95% CI: 1.04, 5.13) were found to be significantly associated with E. histolytica infection.

Conclusions

High seroprevalence of E. histolytica infection was observed among MSM from Beijing and Tianjin, China. Receptive anal sex behavior and SM were identified as potential predictors. Therefore, E. histolytica and HIV co-infection needs to be concerned among MSM due to their sharing the common risk behaviors.

Entamoeba histolytica (E. histolytica) is a very common human gastrointestinal parasitic disease which affects 50 million people worldwide. Men who have sex with men (MSM) have already been found to be one of the high-risk populations with E. histolytica infection. Previous studies have reported an increased risk for E. histolytica infection and invasive amebiasis in HIV seropositive MSM. This pilot study aimed to investigate the serology of E. histolytica among MSM from mainland China. High prevalence of E. histolytica infection (41.1%, 246/599) was observed among the study population, receptive anal sex behavior and sadomasochistic behavior were found to be associated with the E. histolytica serostatus. Although HIV infection was not found to be associated with E. histolytica infection in this pilot study, studies from other countries had reported increased risks for E. histolytica infection and invasive amebiasis among HIV-positive MSM. Our findings suggest E. histolytica infection control needs to be concerned with respect to the increasing HIV prevalence among Chinese MSM population.

Risk factors for intestinal invasive amebiasis in Japan, 2003-2009

We determined yearly change in prevalence and risk factors for amebic colitis caused by intestinal invasive amebiasis among persons who underwent endoscopy and assessed differences between HIV-positive and HIV-negative persons in Japan. A total of 10,930 patients were selected for analysis, of whom 54 had amebic colitis. Prevalence was in 2009 (0.88%, 12/1360) compared with 2003 (0.16%, 3/1904). Male sex (odds ratio [OR] 8.39, 95% CI 1.99-35.40), age <50 years (OR 4.73, 95% CI 2.43-9.20), history of syphilis (OR 2.90, 95% CI 1.40-5.99), and HIV infection (OR 15.85, 95% CI 7.93-31.70) were independent risk factors. No differences in risk factors were identified between HIV-positive and HIV-negative patients. Contact with commercial sex workers was a new risk factor among HIV-negative patients. Homosexual intercourse, rather than immunosuppressed status, appears to be a risk factor among HIV-positive patients.

Risk factors for intestinal invasive amebiasis in Japan, 2003-2009

Amebic colitis is increasing among younger men who have syphilis or HIV.

Metronidazole treatment for acute phase amoebic liver abscess in patients co-infected with HIV

Metronidazole is the drug of choice for invasive amoebiasis; however, it is not known whether its dose or duration require modification in HIV infection when treating invasive amoebiasis. Seven HIV-positive patients with acute phase amoebic liver abscess were treated with daily oral administration of 1500 mg of metronidazole for 10 days. None of the patients required abscess drainage, and metronidazole was effective in all patients without serious side-effects. The CD4 cell count or HIV viral load did not appear to influence the efficacy of metronidazole therapy.

Amebiasis in HIV-1-infected Japanese men: clinical features and response to therapy

Invasive amebic diseases caused by Entamoeba histolytica are increasing among men who have sex with men and co-infection of ameba and HIV-1 is an emerging problem in developed East Asian countries. To characterize the clinical and epidemiological features of invasive amebiasis in HIV-1 patients, the medical records of 170 co-infected cases were analyzed retrospectively, and E. histolytica genotype was assayed in 14 cases. In this series of HIV-1-infected patients, clinical presentation of invasive amebiasis was similar to that described in the normal host. High fever, leukocytosis and high CRP were associated with extraluminal amebic diseases. Two cases died from amebic colitis (resulting in intestinal perforation in one and gastrointestinal bleeding in one), and three cases died from causes unrelated to amebiasis. Treatment with metronidazole or tinidazole was successful in the other 165 cases. Luminal treatment was provided to 83 patients following metronidazole or tinidazole treatment. However, amebiasis recurred in 6 of these, a frequency similar to that seen in patients who did not receive luminal treatment. Recurrence was more frequent in HCV-antibody positive individuals and those who acquired syphilis during the follow-up period. Various genotypes of E. histolytica were identified in 14 patients but there was no correlation between genotype and clinical features. The outcome of metronidazole and tinidazole treatment of uncomplicated amebiasis was excellent even in HIV-1-infected individuals. Luminal treatment following metronidazole or tinidazole treatment does not reduce recurrence of amebiasis in high risk populations probably due to amebic re-infection.

Amebiasis is usually transmitted by ingestion of contaminated food or water in developing countries. Recently, however, increased risk for amebiasis among men who have sex with men (MSM) due to oral-anal sexual contact was reported in developed countries, resulting in growing concern on amebiasis in HIV-1-infected MSM. The recommended treatment of amebiasis is metronidazole or tinidazole, followed by a luminal agent to eliminate intestinal cyst colonization. However, the efficacy of luminal treatment in preventing recurrence has not been assessed yet. In this study, we analyzed the medical records of 170 patients with amebiasis and HIV-1 co-infection. Treatment with metronidazole or tinidazole was excellent whereas luminal treatment did not reduce the frequency of recurrence of amebiasis. Recurrence was more frequent in those MSM with signs of sexual activity such as syphilis infection. Luminal treatment following metronidazole or tinidazole treatment does not reduce recurrence of amebiasis in high risk populations.

Invasion mechanisms among emerging food-borne protozoan parasites

Food-borne parasitic diseases, many known to be more prevalent in poor countries with deficient sanitary conditions, are becoming common worldwide. Among the emerging protozoan parasites, the most prominent is Trypanosoma cruzi, rarely reported in the past to be transmitted by the oral route but currently responsible for frequent outbreaks of acute cases of Chagas disease contracted orally and characterized by high mortality. Several other food-borne protozoans considered emerging include the apicomplexans Toxoplasma gondii and Cryptosporidium, as well as Giardia and Entamoeba histolytica. Here, the interactions of these protozoans with the mucosal epithelia of the host are discussed.

Amebiasis among persons who sought voluntary counseling and testing for human immunodeficiency virus infection: a case-control study

This case-control study aimed to characterize the factors associated with amebiasis, defined as presence of anti-Entamoeba histolytica antibody titers of ≧ 128 by indirect hemagglutination assay, among persons seeking voluntary counseling and testing (VCT) for human immunodeficiency virus (HIV) infection. Between April 2006 and September 2009, 57 of 4,802 persons (1.2%) seeking VCT services were seropositive for E. histolytica infection. Compared with 228 seronegative controls, case subjects were older (odds ratio [OR] for per 1-year increase, 1.098; 95% confidence interval [CI], 1.036, 1.165), less likely to hold bachelor degree or higher (OR, 0.359; 95% CI, 0.152, 0.846), and were more likely to be men who have sex with men (MSM) (OR, 8.382; 95% CI, 2.050, 34.266) and have oral-anal sex (OR, 4.016; 95% CI, 1.711, 9.427) in multiple logistic regression analysis. The MSM, fecal-oral contamination, lower educational achievement, and older age were associated with increased risk for amebiasis among persons seeking VCT for HIV infection.

Fulminant amebic colitis in an HIV-infected homosexual man

We present a case of fulminant amebic colitis in a human immunodeficiency virus (HIV)-infected homosexual man. The patient developed colonic perforation over a short time despite empirical therapy with metronidazole, and underwent right hemicolectomy. Amebic colitis was pathologically diagnosed by identifying invasive trophozoites of Entamoeba in a surgical specimen. Amebic colitis is one of the important differential diagnoses of acute abdomen in HIV-infected patients and/or homosexual men, especially in East Asia. Although fulminant amebic colitis is a rare manifestation of amebiasis, early diagnosis and treatment are thought to be important to improve the outcome of this highly fatal complication.

Seroprevalence of Entamoeba histolytica infection among men who have sex with men in Sydney, Australia

A retrospective analysis was undertaken to determine the seroprevalence of Entamoeba histolytica infection in Sydney, Australia. Using an enzyme-linked immunosorbent assay, 429 high risk human immunodeficiency virus (HIV)-infected men who have sex with men (MSM), 446 low risk HIV-uninfected MSM, and 456 HIV-uninfected controls were assessed. Seroprevalence rates were 5.13% for the high risk HIV-infected MSM group, 0.22% for the low risk HIV-uninfected MSM group, and 0.44% for the control group. We found that high risk HIV-infected MSM have a significantly greater seroprevalence of E. histolytica with a relative risk of 22.87, when compared with low risk HIV-uninfected MSM and 11.69 when compared with controls. These findings show that in Sydney, sexually active HIV-infected MSM are at greater risk of developing amoebic disease caused by E. histolytica than HIV-uninfected MSM and the general population.

Advances in sexually transmitted infections of the gastrointestinal tract

The gastrointestinal mucosa is a target of many sexually transmitted infections, and major advances have increased our understanding of the consequences of such infections within the gastrointestinal system. HIV-1 is associated with a marked loss of mucosal CD4(+) T cells that express CC-chemokine receptor 5. This process seems to be more rapid and more severe in mucosa-associated lymphoid tissue than in the peripheral blood. Mechanistic insights into the underlying cause of acute and chronic gastrointestinal damage with HIV infection-microbial translocation, defects in intestinal epithelial barrier function and activation of a systemic immune response-have also been achieved. Increased understanding of the pathogenesis of mucosal HIV-1 infection may identify therapeutic targets to restore immunological function and the integrity of the intestinal mucosal epithelial barrier. The increasing prevalence of lymphogranuloma venereum in Europe, mostly in HIV-positive men who have sex with men, suggests a change in the epidemiology of what was previously considered to be a 'tropical' disease. The increasing incidence of acute HCV infection transmitted via sexual contact has also been fueled by high-risk sexual behaviors among men who have sex with men, many of whom are also HIV-positive. The first part of this Review discusses the pathogenesis and gastrointestinal complications of HIV infection, and the second part summarizes advances in our understanding of other sexually transmitted infections of the gastrointestinal system.

Reassessment of the epidemiology of amebiasis: state of the art

The epidemiology of amebiasis has dramatically changed since the separation of Entamoeba histolytica and Entamoeba dispar species, and the worldwide prevalence of these species has not been estimated until recently. The most cited data regarding prevalence, morbidity, or mortality due to amebiasis is the 1986 Walsh report, in which 100,000 deaths are reported to occur worldwide each year due to medical complications of invasive amebiasis. However, the prevalence values of Entamoeba histolytica infection could be completely erroneous since the estimations were performed prior to the molecular characterization of E. histolytica and E. dispar species. Moreover, Entamoeba moshkovskii, another morphologically indistinguishable human parasitic Entamoeba, was not mentioned or considered as a contributor to the prevalence figures in endemic areas. However, recent available prevalence and morbidity data obtained through molecular techniques allow the construction of a more reliable map of endemic regions of amebiasis all over the world [the Asian subcontinent (India, Bangladesh), Africa, Asian Pacific Countries (Thailand, Japan), South and Central America (Mexico, Colombia)]. The epidemiology of infectious diseases focuses on identification of factors that determine disease distribution in time and space, transmission factors responsible for the disease, clinical manifestations, and progression in the host, with the goal being the design of realistic intervention and prevention strategies in a reasonable period of time. In the present review, we will describe how molecular tools have made actual knowledge regarding the epidemiology of amebiasis possible. We will also analyze the most relevant available data on prevalence, morbidity, geographic distribution, patterns of transmission, exposure, and risk factors for infection in the human host. Our intention is to emphasize the recent molecular typing methods applied in genotyping Entamoeba species and strains, and to assess their value and limitations. Finally, we will discuss those areas of the host-parasite relationship that are still not fully understood, and the scientific challenges to approach this important public health problem in the future.

New insights into Entamoeba histolytica pathogenesis

PURPOSE OF REVIEW

Entamoeba histolytica is an important global pathogen and a leading cause of parasitic death worldwide. This article summarizes significant research findings over the last year.

RECENT FINDINGS

Efforts have focused primarily on identification of novel virulence determinants in E. histolytica, transcriptional profiling during tissue invasion and stage conversion, and characterization of basic cell biological processes. Additionally, new techniques for gene silencing have been identified.

SUMMARY

A comprehensive examination of the parasite lifestyle on a whole genome level has been undertaken, allowing identification of new virulence genes and signaling pathways and processes relevant to amebic biology.

Invasive amebiasis in men who have sex with men, Australia

Entamoeba histolytica is a pathogenic ameba that has recently been recognized as an emerging pathogen in men who have sex with men (MSM) in Asia-Pacific countries where it is not endemic, i.e., Japan, Taiwan, and Republic of Korea. We report locally acquired invasive amebiasis in Sydney, Australia, exclusively in MSM.

Cost-effectiveness of detection of intestinal amebiasis by using serology and specific-amebic-antigen assays among persons with or without human immunodeficiency virus infection

Among 345 persons who underwent indirect hemagglutination (IHA) serological assays and assays of specific amebic antigens in their stool samples, 24 of 36 (66.7%) who were seropositive for Entamoeba histolytica had intestinal amebiasis as determined by antigen assays compared with 2 of 309 (0.2%) who were seronegative (odds ratio, 307; 95% confidence interval, 64.9 to 1,451). The estimated cost to detect a case of intestinal amebiasis by serology followed by antigen assays ($52) could be reduced by 74.3% and 69.9%, respectively, compared with the costs of the concurrent use of both assays ($202) and the antigen assays alone ($173). Our finding suggests that IHA assays followed by specific-amebic-antigen assays can be cost-effective in the diagnosis of intestinal amebiasis among persons with or without human immunodeficiency virus infection who are at risk for E. histolytica infection.

Molecular epidemiology of amebiasis

Entamoeba histolytica, the causative agent of human amebiasis, remains a significant cause of morbidity and mortality in developing countries and is responsible for up to 100,000 deaths worldwide each year. Entamoeba dispar, morphologically indistinguishable from E. histolytica, is more common in humans in many parts of the world. Similarly Entamoeba moshkovskii, which was long considered to be a free-living ameba, is also morphologically identical to E. histolytica and E. dispar, and is highly prevalent in some E. histolytica endemic countries. However, the only species to cause disease in humans is E. histolytica. Most old epidemiological data on E. histolytica are unusable as the techniques employed do not differentiate between the above three Entamoeba species. Molecular tools are now available not only to diagnose these species accurately but also to study intra-species genetic diversity. Recent studies suggest that only a minority of all E. histolytica infections progress to the development of clinical symptoms in the host and there exist population level differences between the E. histolytica strains isolated from the asymptomatic and symptomatic individuals. Nevertheless the underlying factors responsible for variable clinical outcome of infection by E. histolytica remain largely unknown. We anticipate that the recently completed E. histolytica genome sequence and new molecular techniques will rapidly advance our understanding of the epidemiology and pathogenicity of amebiasis.

Increased risk for Entamoeba histolytica infection and invasive amebiasis in HIV seropositive men who have sex with men in Taiwan

Background

Incidence 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 Findings

At 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/Significance

HIV-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.

Entamoeba histolytica, morphologically identical to but genetically different from E. dispar and E. moshkovskii, is the causative agent of amebiasis. Recently there have been reports of increased risk for amebiasis among men who have sex with men (MSM) due to oral-anal sexual contact in several developed countries. In this longitudinal follow-up study, the incidence of amebiasis was determined among HIV-infected patients using serological and specific amebic antigen assays. DNA extracted from stool samples containing E. histolytica were analyzed by PCR, sequenced, and compared. Clinical manifestations and treatment response of invasive amebiasis in HIV-infected patients were reviewed. The results demonstrated that HIV-infected MSM were at significantly higher risk of amebiasis than patients from other risk groups. Clustering of E. histolytica isolates by sequencing analyses from geographically unrelated patients suggested person-to-person transmission. Despite immunosuppression, amebic liver abscesses and colitis responded favorably to metronidazole therapy. It is important to investigate in areas of high incidence of both amebiasis and HIV (sub-Saharan Africa) how generalizable these findings are.