Entamoeba species associated with chronic diarrhoea in Pakistan

We determined the prevalence of Entamoeba (E.) histolytica, E. dispar and E. moshkovskii in patients with chronic diarrhoea associated with abdominal pain or discomfort mimicking irritable bowel syndrome. Stool samples were collected from 161 patients with chronic diarrhoea and from 157 healthy controls. Stool microscopy with modified trichrome stain, culture and polymerase chain reaction (PCR) for Entamoeba spp. differentiation was performed. Microscopy demonstrated Entamoeba cysts in 44% (57/129) of patients with diarrhoea compared to 29% (44/151) of controls (P=0·009). In patients with diarrhoea, PCR for E. histolytica was positive in 9% (11/129) (P=0·008), E. dispar in 19% (24/129) (P=0·117) and E. moshkovskii in 19% (24/129) (P<0·001). E. histolytica and E. moshkovskii were significantly associated with diarrhoea while E. dispar was found equally in both groups.     

Entamoeba moshkovskii and Entamoeba dispar-associated infections in pondicherry, India

The prevalence of Laredo strain--Entamoeba moshkovskii--and non-pathogenic E. dispar in patients attending the Jawaharlal Institute of Postgraduate Medical Education and Research hospital, Pondicherry, India, is reported here. E. moshkovskii is reported for the first time in India. The species are morphologically indistinguishable from pathogenic E. histolytica. Of 746 stool samples screened, 68 showing cyst or trophozoite stage of E. histolytica, E. dispar, or E. moshkovskii were subjected to small subunit (SSU) rRNA gene-based polymerase chain reaction, which revealed a higher prevalence of E. dispar (8.8%) and E. moshkovskii (2.2%) compared to E. histolytica (1.7%) in patients. Only 19% of the 68 stool samples, resembling E. histolytica by microscopy, were actually E. histolytica, implying that 81% of suspected infections were misdiagnosed and would have been treated unnecessarily with anti-amoebic drugs.     

Intestinal amoebiasis, giardiasis and geohelminthiases: their association with other intestinal parasites and reported intestinal symptoms.

In order to determine reported signs and symptoms that may predict an intestinal parasitic infection, 241 schoolchildren in western C?te d'Ivoire were interviewed with a simple questionnaire and their stool specimens were examined over several consecutive days. Special emphasis was placed on (i) assessing infections by Entamoeba histolytica/E. dispar, Giardia duodenalis and by intestinal worms, (ii) looking for associations between these parasites, and (iii) looking for associations between these parasites and commonly perceived intestinal signs and symptoms. Complete questionnaire results, intestinal helminth infections derived from 4 Kato-Katz thick smears, and intestinal protozoa infections assessed on a single day by a formalin-ether concentration procedure were obtained from 209 children (87%). A logistic regression modelling approach showed that an infection with E. histolytica/E. dispar was significantly associated with an Entamoeba coli infection. However, for G. duodenalis, hookworm and Ascaris lumbricoides, no association was found between any of these parasites and other intestinal parasites. In a multivariate analysis reported diarrhoea was the only symptom positively associated with an E. histolytica/E. dispar infection (P = 0.028). Its diagnostic performance showed a low sensitivity (28%), a high specificity (85%) and moderate positive and negative predictive values (52% and 67%, respectively). Surprisingly, reported 'turning stomach' was less often reported by children infected with G. duodenalis (borderline significance, P = 0.057). It is concluded that reported diarrhoea could be a symptom worth exploring further for the rapid identification of schoolchildren infected with E. histolytica/E. dispar.     

Entamoeba histolytica and Entamoeba dispar: comparison of two PCR assays for diagnosis in a non-endemic setting

Detection of Entamoeba histolytica, the causative agent of amoebiasis, is an important goal of the clinical parasitology laboratory. The identification of Entamoeba dispar as a morphologically identical but non-pathogenic species has highlighted the need for non-microscopic detection methods able to differentiate between the two organisms. In this study we evaluated the utility of conventional PCR and real-time PCR as methods for identification and differentiation of E. histolytica and E. dispar. The second aim of this study was to determine the relative proportions of infections caused by E. histolytica and the non-pathogenic E. dispar, allowing a picture of the epidemiological situation in a non-endemic setting to be obtained. One hundred and sixty-six clinical samples (faecal and liver abscess samples and one intestinal biopsy) belonging to 108 patients were analysed. More patients with E. dispar infection (8.3%) than patients with E. histolytica infection (5.6%) were found by both PCR assays. It is concluded that routine diagnosis of invasive amoebiasis performed by a combination of microscopy, culture and serology should be complemented with a PCR assay such as real-time PCR that offers a practical and clinically acceptable alternative for rapid and accurate diagnosis of amoebic infection in patients presenting with symptoms indicative of this disease.     

Species-specific field testing of Entamoeba spp. in an area of high endemicity

Entamoeba histolytica has been separated in recent years into 2 morphologically identical species: the apathogenic E. dispar and the pathogenic E. histolytica, only the latter being pathogenic. Although various laboratory techniques allow discrimination between the 2 species there is a lack of field data about the suitability of available diagnostic tests for use in epidemiological studies and few epidemiological studies using species-specific diagnosis have been performed at community level in endemic areas, especially in sub-Saharan Africa. We conducted a repeated cross-sectional study of 967 schoolchildren in central C?te d'Ivoire to compare and evaluate light microscopy, 2 different antigen detection assays, and one polymerase chain reaction (PCR) assay. Microscopy and a non-specific antigen capture Entamoeba enzyme-linked immunosorbent assay (ELISA) were used for the primary screening of all children (time t0). The prevalence of the E. histolytica/E. dispar species complex at t0 was 18.8% by single microscopical examination and 31.4% using the non-specific ELISA. Approximately 2 months after the initial screening, fresh stool specimens were collected on 2 consecutive days (t1 and t2) from (i) all the children who were positive by microscopy at t0 (n = 182) and (ii) 155 randomly selected children who were negative at the primary screening. These samples were tested with a second antigen detection ELISA specific for E. histolytica (n = 238) and with a species-specific PCR assay (n = 193). The second and third examinations (t1 and t2) revealed an additional 43 infections with the species complex E. histolytica/E. dispar, so that the cumulative microscopical prevalence for t1 and t2 was 27.7%. The overall prevalence of E. histolytica by species-specific ELISA antigen detection was low (0.83%), while the prevalence of E. dispar was 15%. When analysing only microscopically positive samples by PCR (n = 129), the ratio E. histolytica: E. dispar was very low (1:46), suggesting that the vast majority of Entamoeba infections in this area were apathogenic. Both species-specific tests performed well but the ELISA was easier to use for large-scale field screening.     

Overdiagnosis of amoebiasis in the absence of Entamoeba histolytica among patients presenting with diarrhoea in Wonji and Akaki, Ethiopia

To confirm the high reported incidence of intestinal amoebiasis among study participants at 2 cohort sites in Ethiopia where an HIV/AIDS study is taking place, stool samples of 232 patients with complaints of diarrhoea were examined for the presence of Entamoeba histolytica and E. dispar DNA between April and December 2001. By microscopy, 91 (39%) of the study participants were reported to harbour Entamoeba trophozoites and/or four-nucleated cysts. Using specific E. histolytica and E. dispar DNA amplification and detection, none of the study participants were found to be infected with E. histolytica and only 21 (9%) with E. dispar. The consequences of the overdiagnosis of E. histolytica are briefly discussed.     

Amoebiasis among institutionalized psychiatric patients in Taiwan.

Although information on amoebiasis among institutionalized psychiatric patients is available, reports on the relationship between behaviour and this infection are not abundant. From July 1995 to June 1996, stool and blood samples were collected from 565 patients in three psychiatric hospitals of North Taiwan. Stool samples were examined using the direct smear and formalin-ethyl acetate sedimentation techniques as well as ProSpecT Entamoeba histolytica Microplate Assay kit. Blood samples were examined by the Amebiasis Serology Microwell ELISA kit. Among these patients, 14 (2.5%) harboured one or two species of intestinal parasites. There were 6 (1.1%) E. histolytica/E. dispar cyst passers: 5 positive in stool ELISA test and 2 with antibodies against E. histolytica. Among demographic factors, type of psychiatric disorder and disability, only a significant sexual difference in seropositivity of E. histolytica was observed. These findings indicate that the infected patients acquired the infections before they entered the hospitals.     

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.     

Determination of Entamoeba histolytica infection in patients from Greater Metropolitan Belém, Para, Brazil, by enzyme-linked immunosorbent assay (ELISA) for antigen detection

The epidemiological status of amebiasis has been reevaluated since Entamoeba histolytica (pathogenic) was considered a distinct species from Entamoeba dispar (non-pathogenic). We investigated E. histolytica antigens in stool samples from residents of Belém, Para State, Brazil, with commercially available enzyme-linked immunosorbent assay (E. histolytica Test, TechLab Inc., Blacksburg, USA). A total of 845 samples were analyzed, of which 248 were positive (29.35%). E. histolytica infection was more frequent in the over-14-year age group (30.36%) than in the 0-14-year group (28.28%), but the difference was not statistically significant (p < 0.05). Of all the samples, 334 were also submitted to parasitological methods (direct, Hoffman, and Faust et al.). There were discordant results between ELISA and parasitological methods in 83 samples (24.85%), with more positive results using ELISA. Our results thus suggest that intestinal amebiasis is an important public health problem in Greater Metropolitan Belém.     

Royal Society of Tropical Medicine and Hygiene Meeting at Manson House, London, 19 February 1998. Amoebic disease. Entamoeba histolytica and E. dispar: comparison of molecules considered important for host tissue destruction.

Entamoeba histolytica and E. dispar are genetically distinct but closely related protozoan species. Both colonize the human gut but only E. histolytica is able to invade tissues and cause disease. Comparison of the 2 species may help to elucidate the specific mechanisms involved in the pathogenicity of E. histolytica. During the last few years, various amoeba molecules considered to be important for pathogenic tissue invasion have been identified and characterized, such as a galactose-inhibitable surface lectin, pore-forming peptides and cysteine proteinases. This review summarizes present knowledge about the structure and function of these molecules, with emphasis on the differences between E. histolytica and E. dispar.     

Risk factors for infection by the Entamoeba histolytica/E. dispar complex: an epidemiological study conducted in outpatient clinics in the city of Manaus, Amazon Region, Brazil

An epidemiological study was conducted on a population attending outpatient clinics in Manaus, Amazon, Brazil to determine the prevalences of infection by the Entamoeba histolytica/E. dispar complex and by E. histolytica alone, as well as to identify the risk factors involved in transmission. The study was conducted in two phases: survey and case-control. Face-to-face interviews were carried out and faecal samples collected from 1578 individuals. Faeces were examined by optical microscopy and tested for the pathogenic E. histolytica specific antigen. Positivity to E. histolytica/E. dispar was 21.5% (340 cases). Cases were compared with 340 control samples, negative for the E. histolytica/E. dispar complex based on examination by optical microscopy. The analysis was conducted by logistic regression. The risk factors identified were: place of residence, age, ingestion of raw vegetables, quality of water consumed, number of rooms and bedrooms per house, and having other protozoan infections. Specific antigen detection tests identified 22 participants infected by E. histolytica (6.8%) among those positive for E. histolytica/E. dispar. There was a higher proportion of males among participants infected by E. histolytica than among those with E. dispar infections. The study population was asymptomatic or presented non-specific symptoms that could be attributed to amoebiasis.     

Prevalence and risk factors for protozoan and nematode infections among children in an Ecuadorian highland community

In order to create a parasite prevention program for Santa Ana, Ecuador, we worked with local physicians to identify the prevalence and risk factors for intestinal parasitic infection among children. Two hundred households were randomly selected and asked to submit three stool samples from a selected child. Information from direct observation and questionnaires was used to determine environmental and behavioral risk factors for parasitic infection. Prevalence of any parasitic infection was 65.6% of the 189 children who submitted fecal samples. Parasitic infections included Entamoeba histolytica/E. dispar (46.6%), Giardia lamblia (18.5%) and Ascaris lumbricoides (20.1%). In a multivariate logistic model, risk factors (P<0.05) for E. histolytica/E. dispar included >1 month since antiparasitic treatment, not adding chlorine to drinking water, children not washing their hands before eating, and having a fewer number of electrical appliances in the home. The risk factor identified for G. lamblia was children not washing their hands before eating. Risk factors for A. lumbricoides included >6 months since antiparasitic treatment and having a fewer number of electrical appliances in the home. This study may have implications for other communities throughout the developing world.     

Confirmation by PCR of the existence in Tunisia of Entamoeba histolytica and Entamoeba dispar

AIM: Amibias are illness in Tunisia diagnosed until now on the sole basis of the morphological aspects of the parasite. Our aim is to report the first Tunisian results concerning the molecular identification of E. histolytica/E. dispar, METHODS: 25 stools presenting cysts and/or vegetative shapes of E. histolytica/E. dispar were gathered at the "Laboratoire de Parasitologie H?pital La Rabta Tunis" between 2001and 2004 for PCR. The stools came from 24 subjects, one of them having two samples: 9 Tunisian patients, 5 adressed to the hospital services for abdominal pains or diarrheas and 4 adressed for a systemic tracking (food manipulation), and 15 foreign students for which a tracking is done each fall. RESULTS: The identification showed thus for the Tunisian patients the presence of : E. histolytica alone for a patient (food manipulator) 11%. E. histolytica associated to E. dispar for two patients 22%. E. dispar alone for six patients 67%. Nearly similar results has been obtained for foreign student's samples: E. histolytica alone in one case (7%), E. histolytica associated to E. dispar in four cases (26%) and E. dispar alone in 10 cases (67%). CONCLUSION: These results show therefore the existence in Tunisia the two species E. histolytica and E. dispar for symptomatic or non symptomatic patients. The distinction between the two species is very important on the therapeutic level as well as the epidemiologic and public health level.     

多聚酶链反应在阿米巴病流行病学研究中的应用

用两对引物扩增（ＰＣＲ）溶组织内阿米巴带囊者粪便中的ＤＮＡ，以鉴别感染虫株的致病性，致病和非致病性ＰＣＲ均为阳性者１人（３．１％），仅一项阳性者分别为６人（１８．８％）和２５人（７８．１％）。７例致病性ＰＣＲ阳性者中，６人有腹泻症状（ＯＲ＝３１．５）。各种对照标本均呈ＰＣＲ阴性反应。以ＰＣＲ法对一小样本人群进行阿米巴病调查，致病和非致病虫株的感染率均为１０％。结果表明，在阿米巴病流行病学调查中，可     

Outbreak of amoebiasis in a Dutch family; tropics unexpectedly nearby

An amoebic liver abscess, amoebic dysentery and asymptomatic cyst passage were diagnosed in a father, a mother and one of their three children, respectively. One of the other children had been in the tropics, but only after the father's symptoms had begun. All three family members were infected with the same strain of Entamoeba histolytica as determined by polymerase chain reaction (PCR)-based DNA typing. The source of infection was most probably in Southern Italy where the family regularly spent their summer holidays. All three infected patients recovered after drug treatment. In a patient with a liver abscess or colitis, amoebiasis should be considered even in the absence of a history of a stay in the tropics. Stool samples should be examined for amoebic cysts and trophozoites. PCR analysis of parasite DNA extracted directly from stool samples makes differentiation between the morphologically identical cysts of E. histolytica and the non-pathogenic Entamoeba dispar possible. In addition, serum antibodies to E. histolytica are almost always present in symptomatic patients. Invasive infections with E. histolytica require treatment with a tissue amoebicidal drug, followed by a contact amoebicide to prevent recurrence. Currently, paromomycin is considered to be the first-line luminal amoebicide because of its efficacy and safety.     

A Dutchman from Mali with a perianal ulcer caused by cutaneous amoebiasis

A 66-year-old Dutchman, living in Mali, presented with an extensive progressive perianal ulcer despite local and antibiotic treatment. Microscopic examination of the stool revealed Entamoeba histolytica/dispar cysts and phagocytosing trophozoites were seen in fresh scrapings of the ulcer, a diagnostic feature of infection with E. histolytica. The diagnosis was cutaneous amoebiasis and the patient was effectively treated with metronidazole and local debridements. Primary cutaneous amoebiasis is a rare disease. Diagnosis and treatment are relatively simple but lack of familiarity with the disease may lead to misdiagnosis or diagnosis at a late stage ofthe infection.     

Diagnosis of intestinal amebiasis using coproscopic and immunological methods in a population sample in greater metropolitan Belém, Pará, Brazil

We compare diagnostic methods for Entamoeba histolytica in fecal samples from the city of Belém, Pará, Brazil. We analyze stool samples from children and adults (Group I); stool and serum samples from adults (Group II); and stool samples from children (Group III). In groups I and III, we used direct examination with lugol (DM), Faust et al (FM), and ELISA (detection of E. histolytica anti-GIAP coproantigen) and in group II, DM, iron hematoxylin staining (IHS), FM, ELISA, and the indirect immunofluorescence test (IFAT) for detection of IgG antibodies. Positivity was 10.50% by DM plus FM and 28.99% by ELISA. There was no correlation between positivity and age group. In Group II (n = 87), the positive rate was 4.59% by DM plus FM, 8.04% by IHS, 4.59% by IFAT, and 21.83% by ELISA. The ELISA test was the most sensitive for all groups. IFAT alone is still not a useful tool for diagnosis of E. histolytica infection. The ELISA test is simple, performed in one-third of cases used for IHS and IFAT, and greatly improves quality of diagnosis. We recommend this as the method of choice for diagnosis of suspected E. histolytica infection.     

Microsporidial infections due to Encephalitozoon intestinalis in non-HIV-infected patients with chronic diarrhoea

We determined the prevalence of microsporidia Enterocytozoon (Ent.) bieneusi and Encephalitozoon (E.) intestinalis infection in patients with chronic diarrhoea and hepatocellular carcinoma (HCC). A total of 330 stool samples were examined from 171 (52%) patients with chronic diarrhoea, 18 (5%) with HCC while 141 (43%) were controls. Stool microscopy, polymerase chain reaction (PCR) with species-specific primers for Ent. bieneusi and E. intestinalis and sequencing were carried out. Microsporidia were found by trichrome staining in 11/330 (3%) and E. intestinalis by PCR in 13/330 (4%) while Ent. bieneusi was not detected. PCR for E. intestinalis was positive in 8/171 (5%) stool samples from patients with chronic diarrhoea, 2/141 (1·4%) samples from healthy controls and in 3/18 (17%) samples from patients with HCC. In the chronic diarrhoea group, E. intestinalis was positive in 4/171 (2·3%) (P=0·69) stool samples compared to 2/18 (11%) (P=0·06) in the HCC group and 2/141 (1·4%) from healthy controls. E. intestinalis infection was significantly associated with chronic diarrhoea and HCC in these patients who were negative for HIV. Stool examination with trichrome or species-specific PCR for microsporidia may help establish the cause of chronic diarrhoea.     

Endemic amebiasis in an Arkansas community.

Parasitologic, serologic, and epidemiologic studies were done during 1967 in Calion, Arkansas (population 544). Infection with Entamoeba histolytica was found to be endemic but was segregated along racial lines. Twenty-two (9.9%) black compared with only one (0.6%) white had E. histolytica demonstrated in one stool examination; only two blacks had symptoms suggestive of amebiasis. No positive amebiasis indirect hemaggulination titers were found in 135 white residents. In contrast, 41 (17.9%) blacks had positive titers. Age, sex, and geographic location were not associated with stool or seropositivity. Within the black population, clustering of stool and seropositivity occurred. Significantly higher rates of stool and seropositivity were seen in households with crowding and poor sanitation as evidenced by lack of indoor toilet facilities. The presence of contaminated water supplies did not correlate with stool or seropositivity. The probable importance of person-to-person transmission is suggested by the observed clustering of infection within households with crowding and unsanitary conditions. The absence of evidence for transmission by food or water further supports this hypothesis.     

A comparative study of Entamoeba histolytica (NIH :200, HK9, etc.), "E. histolytica-like" and other morphologically identical amoebae using isoenzyme electrophoresis

Cultures of old, well documented strains of Entamoeba histolytica (NIH:200, HK9 etc.) have been compared with "E. histolytica-like" strains and, in turn, with E. moshkovskii, E. invadens and E. chattoni. They have been grouped according to their isoenzyme patterns. The "E. histolytica-like" organisms give patterns similar to E. moshkovskii and both of these are different from E. histolytica Groups I to IV. E. invadens and E. chattoni have easily distinguished characteristic isoenzyme bands. "E. polecki" is indistinguishable from E. histolytica.