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Entamoeba histolytica

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Entamoeba histolytica Scientific classification : Eukaryota Phylum: Class: Genus: Entamoeba Species: E. histolytica

For the infection and disease caused by this parasite, refer to .

Entamoeba histolytica is an anaerobic parasitic protozoan, part of the genus Entamoeba. It infects predominantly humans and other primates. It is estimated that about 50 million people are infected with the parasite worldwide. Diverse mammals such as dogs and cats can become infected but are not http://en.wikipedia.org/wiki/Entamoeba_histolytica (1 of 5)13/11/2550 13:08:05 Entamoeba histolytica - Wikipedia, the free encyclopedia thought to contribute significantly to transmission. The active (trophozoite) stage exists only in the host and in fresh loose ; survive outside the host in water, soils and on , especially under moist conditions on the latter. When cysts are swallowed they cause infections by excysting (releasing the trophozoite stage) in the digestive tract.

E. histolytica, as its name suggests (histo–lytic = tissue destroying), causes disease; infection can lead to amoebic or amoebic abscess. Symptoms can include fulminating dysentery, , , fatigue, , and amebomas. The can actually 'bore' into the intestinal wall, causing lesions and intestinal symptoms, and it may reach the stream. From there, it can reach different vital organs of the human body, usually the liver, but sometimes the lungs, brain, spleen, etc. A common outcome of this invasion of tissues is a , which can be fatal if untreated. Ingested red blood cells are sometimes seen in the amoeba cell cytoplasm.

It can be diagnosed by stool samples but it is important to note that certain other species are impossible to distinguish by microscopy alone. Trophozoites may be seen in a fresh fecal smear and cysts in an ordinary stool sample. ELISA or RIA can also be used.

Genus and Species Entamoeba histolytica

Amoebiasis; Amoebic dysentery; Extraintestinal Amoebiasis, usually Etiologic Agent of: = “anchovy sauce”); Amoeba Cutis; Amoebic Lung Abscess (“liver-colored sputum”)

Infective stage Cyst

Definitive Host Human

Portal of Entry Mouth

Mode of Transmission Ingestion of mature cyst through contaminated or water

Habitat Colon and Cecum

Pathogenic Stage Trophozoite

Locomotive apparatus Pseudopodia (“False Foot”)

Motility Active, Progressive and Directional

Nucleus 'Ring and dot' appearance: peripheral chromatin and central karyosome

Mode of Reproduction Binary Fission

http://en.wikipedia.org/wiki/Entamoeba_histolytica (2 of 5)13/11/2550 13:08:05 Entamoeba histolytica - Wikipedia, the free encyclopedia Lytic (it looks like “flask-shaped” holes in Gastrointestinal Pathogenesis tract sections (GIT)

Type of Encystment Protective and Reproductive

Most common is Direct Fecal Smear (DFS) and staining (but does not allow identification to species level); Enzymeimmunoassay (EIA); Lab Diagnosis Indirect Hemagglutination (IHA); Antigen detection – monoclonal ; Polymerase Chain Reaction PCR for species identification. Culture: From faecal samples - Robinson's medium, Jones' medium

Metronidazole for the invasive trophozoites PLUS a lumenal Treatment amoebicide for those still in the intestine ( is the most widely used)

Trophozoite Stage

Pathognomonic/Diagnostic Ingested RBC; distinctive nucleus Feature

Cyst Stage

Chromatoidal Body 'Cigar' shaped bodies (made up of crystalline ribosomes)

Number of Nuclei 1 in early stages, 4 when mature

Pathognomonic/Diagnostic 'Ring and dot' nucleus and chromatoid bodies Feature

[edit] External links

● CDC DPDx Diagnostic Web Site

● LSHTM Entamoeba Homepage

● Public domain Entamoeba histolytica article from the Bad Bug Book, from which the original version of this article was adapted.

Retrieved from "http://en.wikipedia.org/wiki/Entamoeba_histolytica"

Categories: Amoebozoa | Parasites http://en.wikipedia.org/wiki/Entamoeba_histolytica (3 of 5)13/11/2550 13:08:05 Entamoeba histolytica - Wikipedia, the free encyclopedia Views

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