AMEBIASIS AND COMPARISON OF MICROSCOPY

21 Dec
2009

amebiasis

INTRODUCTION

In human amebiasis, the differentiation of the invasive parasite Entamoeba histolytica from the commensal organism Entamoeba dispar is of great concern to the medical community. Amebiasis is transmitted by fecal contamination of drinking water and foods, direct contact with dirty hands or objects, anal sexual contact, and poor sanitation and hygiene. For many years E. histolytica and E. dispar have been known to be two distinct species. The description of E. dispar by Brumpt was dismissed as a synonym of E. histolytica. However, later evidence mounted in support of Brumpt’s description of E. dispar as a separate species. E. 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 leading to massive and sometimes lethal pathological alterations, such as ulcerative colitis or abscesses of various organs—most commonly, the liver.

Infections of E. histolytica and E. dispar are often diagnosed by demonstrating cysts or trophozoites in a stool sample. A great number of methods for distinguishing E. histolytica from E. dispar have now been described in the literature.
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Sargeaunt looked at a database of several thousand isolates from all over the world and grouped all E. histolytica into one of two groups: i) pathogenic E. histolytica and ii) nonpathogenic E. histolytica. This division was further supported by antigenic differences and differences in the DNA. By 1993, a lot of evidence was available to distinguish E. histolytica from E. dispar and was formally redescribed. The World Health Organization expert committee endorsed the redescription of the two species. Since then, an ELISA specific for E. histolytica has been developed for fecal-antigen detection. This technique detected all cases of amoebic dysentery. Also, there is a fecal-antigen detection test, which is based on a monoclonal antibody against galactose-inhibitable lectin on the surface of E. histolytica. An ELISA-based technique in which PCR products are detected with dioxigenin-labeled primers has been developed to differentiate between E. histolytica and E. dispar. The tests, based on nucleic acid detection to differentiate the two species, are being used in a routine reference diagnostic service for cyst carriers.

E. histolytica or E. dispar infect half a billion people annually, with 90% being asymptomatic and the remaining 10% accounting for the third most common cause of death from parasitic disease in the world. Additional health effects of ame­biasis are delayed treatment of other related diarrheal diseases due to misdiagnosis of E. histolytica when conventional microscopic methods are employed. The immunological diagnostic tests can specifically differentiate between these two related species. canadian antibiotics

The present study was carried out to examine the prevalence and etiological agent of amebiasis in Kilimanjaro, Tanzania. The main aim of this study was to demonstrate the importance of correctly identifying E. histolytica in order to avoid unnecessary treatment costs and delayed treatment of actual infection.

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