Amibiase : au cours de rapports sexuels,un mode de transmission sous-estimé ?

Introduction

Amoebiasis is a cosmopolitan disease and the third most deadly of parasitic diseases. Entamoeba histolytica is the only one to be pathogenic. Its transmission is not only related to the faecal peril but also sexual, with cases described among men who have sex with men. A case of unusual sexual transmission is described in this article, aiming to discuss the impact of these ways of transmitting amoebiasis on patient management.

Current drug therapy of protozoal diarrhoea

Protozoal infections of the gastrointestinal tract occur worldwide and have substantial morbidity and mortality. Prevalence is higher in the economically deprived regions of the world, especially the developing countries. Infections like amoebiasis and giardiasis have a worldwide distribution, being endemic in India. Apart from producing GI symptoms, growth and development of children is also impaired. It is seen that protozoa multiply rapidly in their hosts and as there is a lack of effective vaccines, chemotherapy has been the only practiced way to treat individuals and reduce transmission. The current treatment modalities for protozoal diarrhoea include 5-nitrosoimidazoles, iodoquinol, diloxanide furoate, paromomycin, chloroquine, and trimethoprim-sulphamethoxazole.     

Comparative study of aminosidine,etophamide and nimorazole,alone or in combination,in the treatment of intestinal amoebiasis in Kenya

Summary 417 patients suffering from intestinal amoebiasis were randomly allocated to 6 different treatment groups in a controlled study in 3 District Hospitals in Kenya. The patients received either aminosidine (A), etophamide (E), nimorazole (N), or the combinations NA, NE, EA. Treatment in all cases was given twice daily for 5 days. Before and after treatment, rectosigmoidoscopy was done in each patient, and stool examination with characterization of invasive (IF) and non invasive (NIF) forms of amoeba was done daily throughout treatment, and on Days 15, 30 and 60 of follow-up.Clinical cure was good after all the treatments, varying from 90 to 100%; parasitological cure at the end of treatment was 100% in the NA and EA treatments groups, and 98% in A group. The incidence of relapses was nil in the EA group, followed by 3% in NA and 6% in A groups. Anatomical cure (healing of ulcers) was 97.8% in the NA group, 95.5% in the N group and 88.5% in the A group. Drug tolerance was excellent or good after all the treatments, except that the EA combination produced diarrhoea in 76.5% of patients.Overall analysis of the findings, including tolerance of the various treatments, showed that aminosidine either alone or in combination with nimorazole gave the best results.Ulcers seen on rectosigmoidoscopy were more common in patients excreting invasive forms of amoebae in their stools.     

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.     

Effectiveness of latex agglutination slide test in the diagnosis of imported invasive amoebiasis in the emergency department

We compared a latex agglutination test (LAT) with enzyme-linked immunosorbent assay and indirect hemagglutination assay in the diagnosis of invasive amoebiasis. A retrospective biological records review has included 639 patients for whom these three serological tests were performed. The sensitivity of the LAT was 97.8% and the specificity was 97%.     

Fulminant amoebic colitis during chemotherapy for advanced gastric cancer

A 52-year-old man had bloody stools during chemotherapy for gastric cancer. A colonoscopy revealed necrotizing ulcer-like changes. A biopsy confirmed the presence of amoebic trophozoites. Subsequently, peritonitis with intestinal perforation developed, and emergency peritoneal lavage and colostomy were performed. After surgery, endotoxin adsorption therapy was performed and metronidazole was given. Symptoms of peritonitis and colonitis resolved. However, the patient＇s general condition worsened with the progression of gastric cancer. The patient died 50 d after surgery. Fulminant amoebic colitis is very rarely associated with chemotherapy. Amoebic colitis should be considered in the differential diagnosis of patients who have bloody stools during chemotherapy.     

Intestinal amoebiasis: 160 years of its first detection and still remains as a health problem in developing countries

Amoebiasis is a parasitic disease caused by Entamoeba histolytica (E. histolytica), an extracellular enteric protozoan. This infection mainly affects people from developing countries with limited hygiene conditions, where it is endemic. Infective cysts are transmitted by the fecal-oral route, excysting in the terminal ileum and producing invasive trophozoites (amoebae). E. histolytica mainly lives in the large intestine without causing symptoms; however, possibly as a result of so far unknown signals, the amoebae invade the mucosa and epithelium causing intestinal amoebiasis. E. histolytica possesses different mechanisms of pathogenicity for the adherence to the intestinal epithelium and for degrading extracellular matrix proteins, producing tissue lesions that progress to abscesses and a host acute inflammatory response. Much information has been obtained regarding the virulence factors, metabolism, mechanisms of pathogenicity, and the host immune response against this parasite; in addition, alternative treatments to metronidazole are continually emerging. An accesible and low-cost diagnostic method that can distinguish E. histolytica from the most nonpathogenic amoebae and an effective vaccine are necessary for protecting against amoebiasis. However, research about the disease and its prevention has been a challenge due to the relationship between E. histolytica and the host during the distinct stages of the disease is multifaceted. In this review, we analyze the interaction between the parasite, the human host, and the colon microbiota or pathogenic microorganisms, which together give rise to intestinal amoebiasis.     

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     

实验性大鼠肠阿米巴病的病理学研究——扫描电镜及免疫组织化学观察

用盲肠内接种阿米巴滋养体的方法,复制出大鼠肠阿米巴病动物模型,经组织学及扫描电镜观察发现:感染大鼠的盲肠病变与人类急慢性肠阿米巴病类似,早期为盲肠的弥漫性、非特异性炎症及溃疡形成,晚期为修复愈合与新鲜溃疡同时存在的组织学改变,病变出现高峰在接种后3～7d 间;大鼠感染率为93.6%,盲肠溃疡发生率为43.6%,可作为研究肠阿米巴病的动物模型。应用自行制备的兔抗阿米巴血清对感染的盲肠组织进行免疫组织化学(PAP)染色的结果,证实此法能清楚、准确地显示组织中的阿米巴滋养体,可用于肠阿米巴病的病理诊断及回顾性研究。     

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.