Although the majority of individuals infected with e. Presence of trophozoites containing red blood cells is indicative of tissue invasion by virulent escherichia histolytica parasites. The potent cytotoxic activity of the parasite appears to underlie disease path. Entamoeba histolytica an overview sciencedirect topics. Entamoeba histolytica global water pathogen project. Nov 29, 20 the nonpathogenic entamoeba dispar, however, is morphologically identical to e. The cysts are secreted by individuals that harbor the parasite along. Anyone can get amebiasis, but it occurs more often in people arriving from tropical countries that have poor sanitary conditions, in individuals in institutions for the developmentally disabled, and in men who have sex with men. Morphology, life cycle, pathogenesis, clinical manifestation, lab diagnosis and treatment entamoeba histolytica is a common protozoan parasite found in the large intestine of human. The biology of the parasite and the pathogenic mechanisms. Amebiasis entamoeba histolytica infection definition. The quadrinucleate cyst is resistant to the gastric environment and passes unaltered through the stomach. Entamoeba histolytica, a protozoan parasite, is the etiologic agent of amoebiasis in humans. Amebiasis is the infection of the human gastrointestinal tract by entamoeba histolytica, a protozoan parasite that is capable of invading the intestinal mucosa and may spread to other organs, mainly the liver.
Entamoeba histolytica and another ameba, entamoeba dispar, which is about 10 times more common, look the same when seen under a microscope. We developed a realtimepcr assay utilizing a molecularbeacon probe for the detection of entamoeba histolytica and compared its sensitivity to stool antigen detection and traditional pcr. Simulated mcqs of medical entrance examinations like neet, jipmer, pgi, aiims, dnb and cet has been made. Jun 01, 2001 few organisms are more aptly named than entamoeba histolytica, an intestinal protozoan parasite that can lyse and destroy human tissue. Entamoeba dispar, an ameba morphologically similar to e. Antigen detection enzyme linked immunosorbent assay, polymerase chain reaction solution hybridisation enzyme linked immunoassay pcrshela, and a commercial lightcycler pcr were compared using 101 stool and pus samples. To maximize recovery of cysts, stool samples in formalin, or other fixatives, should be concentrated prior to microscopic examination e.
To assess different laboratory methods for the identification of entamoeba histolytica in clinical samples. Usually the hosts repair of the epithelial cells can keep pace with the damage. Pathology of amebiasis entamoeba histolytica infection dr. Entamoeba histolytica, entamoeba dispar, entamoeba moshkovskii, entamoeba polecki, entamoeba coli and entamoeba hartmanni reside in the human intestinal lumen. In spite of a wealth of knowledge on the biochemistry and cellular and molecular biology of entamoeba histolytica, little has been done to apply these advances to our understanding of the lesions observed in patients with intestinal amebiasis. Entamoeba histolytica ab,igg labsd00030 is more sensitive than any stool examination. Entamoeba histolytica is an anaerobic parasitic protozoan that infects the digestive tract of predominantly humans and other primates. It exists in two formsthe trophozoite which is the acti. Of these entamoeba histolytica is the only species found to be associated with intestinal disease. The genome of entamoeba histolytica was sequenced and assembled in 2005 and provided many insights into the. Pathology of amebiasis entamoeba histolytica infection dr sampurna roy md. Laboratory diagnostic techniques for entamoeba species.
They undergo encystment but before encystment, the parasites round up, eliminate food vacuoles and accumulate considerable amount of food materials in the form of glycogen and black rodlike chromatoid granules. Visit systemic pathology cases giardia lamblia is a pear or sickle shaped, binucleate protozoa. Amebiasis is an intestinal illness caused by a microscopic parasite called entamoeba histolytica. Entamoeba histolytica is an enteric protozoan parasite with worldwide distribution.
For suspected amoebic liver abscess, entamoeba histolytica ab,igg labsd00030 is more sensitive than any stool examination. Some of them show ingested rbc arrow in the cytoplasm. Giardia exists as infectious cysts in contaminated food and water which spread by fecaloral route and as trophozoites which multiply in the intestinal lumen and cause disease. Updates in clinical manifestation, pathogenesis, and vaccine development. Asymptomatic infections are responsible for the spread of the parasite with numerous cysts being passed in normal stools. Pathogenesis of infection by entamoeba histolytica citeseerx. The annual number of entamoeba histolytica infections throughout the world is. Fecaloral route, either by eating or drinking fecally contaminated food or water or persontoperson contact such as by diaper changing or sexual activity. Differentiation is possible, but not always easy, based on morphologic characteristics of the. Tissue destruction and invasion by entamoeba histolytica. It is the third leading parasite cause of death in the developing countries.
The quadrinucleate cyst is resistant to the gastric environment and passes unaltered through. It is estimated that there are fifty million cases of amebic diarrhea on a worldwide basis annually with 100,000 deaths. Intestinal amoebiasis the amoebae cause disease only when they invade the intestinal tissues. Amoebiasis is one of the major public health problems in developing countries. Entamoeba histolytica modes of transmission human being is the principle host source of infection. In this article we will discuss about entamoeba histolytica. It is a parasite that infects an estimated 50 million people around the world and is a significant cause of morbidity and mortality in developing countries.
It exists in two formsthe trophozoite which is the active, dividing form. May activate apoptosis in target cells trends parasitol 2011. Predominantly infecting humans and other primates causing amoebiasis, e. Round to oval trophozoites containing pink cytoplasm with foamy, granular or vacuolated appearance. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. An organisms genome provides vital information about its biology and evolution. Entamoeba coli is a nonpathogenic species of entamoeba that frequently exists as a commensal parasite in the human gastrointestinal tract.
Dientamoeba fragilis which is a flagellate not an ameba. Amebiasis is due to invasion of the colonic mucosa by the enteric protozoan entamoeba histolytica. Jun 10, 2018 simulated mcqs of medical entrance examinations like neet, jipmer, pgi, aiims, dnb and cet has been made. Please answer and put the answers in the comments box below. In the liver a similar pathological sequence ensues, leading to amebic liver. Technologists must be able to differentiate this organism from e. Recent studies have revealed opportunities to produce an effective vaccine against the entamoeba histolytica infection. The protozoan parasite entamoeba histolytica, possibly other entamoeba spp transmission. Other sources state that many, if not most, individuals believed to carry e. Multiple stool samples at least 3 should be tested before a negative result is reported. House flies and cockroaches mechanical transmission.
Ed sc reg no i56ce9242009 a thesis submitted in partial fulfillment of the requirements for the award of. In spite of the availability of an effective drug and absence of overt drug resistance, the disease is still prevalent among large population and spread over a number of countries. Realtimepcr assay for diagnosis of entamoeba histolytica. Entamoeba histolytica is an anaerobic parasitic amoebozoan, part of the genus entamoeba. The findings of this study suggest that trophozoites of e. Entamoeba histolytica is the responsible parasite of amoebiasis and remains one of the top three parasitic causes of mortality worldwide. Pathogenesis of infection by entamoeba histolytica springerlink. The human intestinal protozoan parasite entamoeba histolytica produces a number of virulence factors such as a galspecific adhesin, cysteine proteinases and a family of small 77 a. The cause of amebiasis is infection by the protozoan parasite entamoeba histolytica. Pathology of amebiasis entamoeba histolytica infection. Jan 23, 2016 pathogenesis and clinical features entamoeba histolytica causes intestinal and extraintestinal amoebiasis. It is responsible for amoebic dysentery bloody diarrhea and invasive extraintestinal amebiasis such as liver abscess, peritonitis, pleuropulmonary abscess. Colonization with the morphologically identical parasite e.
Entamoeba histolytica and entamoeba dispar basic guidelines a. Confusing history 1875 losch correlated dysentery with amebic trophozoites 1925 brumpt proposed two species. Pathogenesis and clinical features entamoeba histolytica causes intestinal and extraintestinal amoebiasis. Although many people harbour this organism world wide, only about 10% develop clinically.
As more is learned about its pathogenesis and the hosts immune response, the potential for developing a vaccine holds promise. In the precystic forms, entamoeba remains only in the intestinal lumen. Organisms are also demonstrated by immunoperoxidase stains. Pathogenesis of disease caused by entamoeba histolytica oxford. Comparison of pcr and antigen detection methods for. Tissue destruction and invasion by entamoeba histolytica katherine s. Amebas friend and foe facultative pathogenicity of entamoeba histolytica. Entamoeba histolytica is an invasive, pathogenic protozoan, causing amoebiasis, and an important cause of diarrhea in developing countries. Amebiasis, also be spelled amoebiasis, is an infectious disease, caused by the protozoan entamoeba histolytica. Diarrheic stools primarily contain trophozoites which cannot persist in the environment. Infection by entamoeba histolytica occurs by ingestion of mature quadrinucleate cysts in fecally contaminated food, water, or hands.
The parasite is responsible for amoebiasis and liver absceses. Amebiasis is caused by the protozoan parasite entamoeba histolytica. With increased travel and emigration to developed countries, infection is becoming more common in nonendemic areas. Entamoeba histolytica is the responsible parasite of amoebiasis and. Molecular methods are also useful in distinguishing between e. However, when the host is stressed, immunocompromised, has too much. Molecular basis of pathogenesis in amoebiasis springerlink. A total of 205 stool and liver abscess pus specimens from patients and controls were used for this purpose, 101 49% of which were positive by the techlab e. Entamoeba histolytica is a protozoan parasite that causes amoebiasis. The most important feature of the pathology of human amebiasis is the greatly destructive nature of the anatomical lesions produced by the protozoan entamoeba histolytica.
Mar 22, 2020 entamoeba histolytica is a protozoan parasite that causes amoebiasis. It is caused by the protist parasite entamoeba histolytica that essentially infects humans, though other species that infect a few. It begins when a person drinks contaminated water or eats foods contaminated with the cystic form infective stage, comes in contact with contaminated colonic irrigation devices or the fecally contaminated hands of food handlers, or by oralanal sexual practices the cystic form changes into trophozoites. The structure and life cycle of entamoeba with diagram. Entamoeba histolytica is an amoeba with worldwide distribution, transmitted through the fecaloral route sakakibara et al. Entamoeba histolytica university of nebraskalincoln. Formerly called the small race of entamoeba histolytica. It is estimated that there are fifty million cases of amebic diarrhea on. Ingestion of contaminated food or water with amoebae cyst infective stage. Entamoeba histolytica introduction there is a large number of species of amoebae which parasitise the human intestinal tract. Amoeba invade colonic crypts, burrow into lamina propria, create flask shaped ulcer with broad base. Entamoeba histolytica must be differentiated from other intestinal protozoa including. In most infected individuals the trophozoites exist as commensals.
Pathogenesis and immune response toward entamoeba histolytica. Our understanding of its epidemiology has dramatically changed since this amoeba was distinguished from another morphologically similar one, entamoeba dispar, a non pathogenic and commensal parasite. Entamoeba histolytica is a common protozoan parasite found in the large intestine of human. It exists in two formsthe trophozoite which is the active, dividing form, and the cyst which is dormant and can survive for prolonged periods outside the host. Recent advances on the knowledge of biochemistry, immunology, cellular and molecular biology, and genetics of this parasite.