Entamoeba histolytica

Entamoeba Histolytica

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Entamoeba histolytica

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

Entamebiasis is an term for the infection more commonly known as amoebiasis.It became the preferred term in MeSH in 1991, but the term amoebiasis is used by the World Health Organization and by those working in the field of amoebiasis research....
.

Entamoeba histolytica is an anaerobic

Anaerobic organism

An anaerobic organism is any organism that does not require oxygen for growth and may even die in its presence....
parasitic protozoa

Protozoa

Protozoan are microorganisms classified as unicellular eukaryotes. While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate....
n, part of the genus

Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
Entamoeba
Entamoeba

Entamoeba is a genus of Amoebozoa found as internal parasitisms or commensalisms of animals.In 1875, Fedor L?sch described the first proven case of amoebic dysentery in St Petersburg, Russia....
. Predominantly infecting humans and other primates, E. histolytica is estimated to infect about 50 million people worldwide. Many older textbooks state that 10% of the world population is infected, but these figures predate the recognition that at least 90% of these infections were due to a second species, E.

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How are cysts adapted for survival outside the host

Which two of the following organisms are most closely related to Entamoeba histolytica - is it Esch...

Encyclopedia

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

Entamebiasis is an term for the infection more commonly known as amoebiasis.It became the preferred term in MeSH in 1991, but the term amoebiasis is used by the World Health Organization and by those working in the field of amoebiasis research....
.

Entamoeba histolytica is an anaerobic
Anaerobic organism

An anaerobic organism is any organism that does not require oxygen for growth and may even die in its presence....
parasitic protozoa
Protozoa

Protozoan are microorganisms classified as unicellular eukaryotes. While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate....
n, part of the genus
Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
Entamoeba
Entamoeba

Entamoeba is a genus of Amoebozoa found as internal parasitisms or commensalisms of animals.In 1875, Fedor L?sch described the first proven case of amoebic dysentery in St Petersburg, Russia....
. Predominantly infecting humans and other primates, E. histolytica is estimated to infect about 50 million people worldwide. Many older textbooks state that 10% of the world population is infected, but these figures predate the recognition that at least 90% of these infections were due to a second species, E. dispar. Mammals such as dogs and cats can become infected transiently, but are not thought to contribute significantly to transmission.

Transmission

The active (trophozoite
Trophozoite

A trophozoite is the activated, feeding stage in the life cycle of protozoan parasites such as the malaria-causing Plasmodium falciparum ....
) stage exists only in the host and in fresh loose feces; cyst
Cyst

A cyst is a closed sac having a distinct biological membrane and cell division on the nearby Biological tissue. It may contain air, fluids, or semi-solid material....
s survive outside the host in water, soils and on foods, especially under moist conditions on the latter. The cysts are readily killed by heat and by freezing temperatures, and survive for only a few months outside of the host. When cysts are swallowed they cause infections by excysting (releasing the trophozoite stage) in the digestive tract. The trophozoite stage is readily killed in the environment and cannot survive passage through the acidic stomach to cause infection.

Pathogenesis

E. histolytica, as its name suggests (histo–lytic = tissue destroying), is pathogenic
Pathogenesis

The term pathogenesis means step by step development of a disease and the chain of events leading to that disease due to a series of changes in the structure and /or function of a cell/tissue/organ being caused by a microbial , chemical or physical agent....
; infection can lead to amoebic dysentery
Dysentery

Dysentery is a disorder of the digestive system that results in severe diarrhea containing mucus and/or blood in the feces. If untreated, Dysentery can be fatal....
or amoebic liver abscess
Liver abscess

A liver abscess is a pus-filled mass inside or attached to the liver. Common causes are an abdominal infection such as appendicitis or diverticulitis....
. Symptoms can include fulminating dysentery, bloody diarrhea, weight loss, fatigue, abdominal pain, and amoeboma
Ameboma

An ameboma, also known as an amebic granuloma, is a rare complication of entamoeba histolytica, where in response to the infecting ameba there is formation of annular colonic granulation, which results in a large local lesion of the bowel....
. The amoeba can actually 'bore' into the intestinal wall, causing lesion
Lesion

A lesion is any abnormal tissue found on or in an organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury....
s and intestinal symptoms, and it may reach the blood 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 liver abscess, which can be fatal if untreated. Ingested red blood cell
Red blood cell

Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen to the body tissues via the blood....
s are sometimes seen in the amoeba cell cytoplasm.

Diagnosis

It can be diagnosed by stool
Feces

Feces, faeces, or f?ces is a waste product from an animal's gastrointestinal tract expelled through the anus during defecation....
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
ELISA

Enzyme-Linked ImmunoSorbent Assay, also called ELISA, Enzyme ImmunoAssay or EIA, is a biochemistry technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample....
or RIA
Radioimmunoassay

Radioimmunoassay is a scientific method used to test antigens without the need to use a bioassay. It was developed by Rosalyn Yalow and Solomon Berson in the 1950s....
can also be used.

|- | width="200pt" align="center"| Genus and Species | width="400pt" align="center"| Entamoeba histolytica |- | width="200pt" align="center"| Etiologic Agent of: | width="400pt" align="center"| Amoebiasis
Amoebiasis

Entamebiasis is an term for the infection more commonly known as amoebiasis.It became the preferred term in MeSH in 1991, but the term amoebiasis is used by the World Health Organization and by those working in the field of amoebiasis research....
; Amoebic dysentery
Amoebic dysentery

Amoebic dysentery is a type of dysentery caused primarily by the amoeba Entamoeba histolytica.Amoebic dysentery is transmitted through contaminated food and water....
; Extraintestinal Amoebiasis, usually Amoebic Liver Abscess = “anchovy sauce”); Amoeba Cutis; Amoebic Lung Abscess (“liver-colored sputum”) |- | width="200pt" align="center"| Infective stage | width="400pt" align="center"| Quadrinucleated cyst (having 4 nuclei) |- | width="200pt" align="center"| Definitive Host | width="400pt" align="center"| Human |- | width="200pt" align="center"| Portal of Entry | width="400pt" align="center"| Mouth |- | width="200pt" align="center"| Mode of Transmission | width="400pt" align="center"| Ingestion of mature cyst through contaminated food or water |- | width="200pt" align="center"| Habitat | width="400pt" align="center"| Colon and Cecum |- | width="200pt" align="center"| Pathogenic Stage | width="400pt" align="center"| Trophozoite
Trophozoite

A trophozoite is the activated, feeding stage in the life cycle of protozoan parasites such as the malaria-causing Plasmodium falciparum ....
|- | width="200pt" align="center"| Locomotive apparatus | width="400pt" align="center"| Pseudopodia (“False Foot”) |- | width="200pt" align="center"| Motility | width="400pt" align="center"| Active, Progressive and Directional |- | width="200pt" align="center"| Nucleus | width="400pt" align="center"| 'Ring and dot' appearance: peripheral chromatin and central karyosome |- | width="200pt" align="center"| Mode of Reproduction | width="400pt" align="center"| Binary Fission |- | width="200pt" align="center"| Pathogenesis | width="400pt" align="center"| Lytic necrosis (it looks like “flask-shaped” holes in Gastrointestinal tract sections (GIT) |- | width="200pt" align="center"| Type of Encystment | width="400pt" align="center"| Protective and Reproductive |- | width="200pt" align="center"| Lab Diagnosis | width="400pt" align="center"| Most common is Direct Fecal Smear (DFS) and staining (but does not allow identification to species level); Enzyme immunoassay (EIA); Indirect Hemagglutination (IHA); Antigen detection – monoclonal antibody; PCR
Polymerase chain reaction

The polymerase chain reaction is a technique widely used in molecular biology. It derives its name from one of its key components, a DNA polymerase used to amplify a piece of DNA by in vitro enzyme DNA replication....
for species identification. Sometimes only the use of a fixative (formalin) is effective in detecting cysts. Culture: From faecal samples - Robinson's medium, Jones' medium |- | width="200pt" align="center"| Treatment | width="400pt" align="center"| Metronidazole
Metronidazole

Metronidazole is a nitroimidazole antibiotic medication used mainly in the treatment of infections caused by susceptible organisms, particularly anaerobe bacterium and protozoa....
for the invasive trophozoites PLUS a lumenal amoebicide for those still in the intestine. Paromomycin (Humatin) is the lumenal drug of choice, since Diloxanide furoate
Diloxanide furoate

Diloxanide furoate is an anti-protozoal drug used in the treatment of Entamoeba histolytica and some other protozoal infections....
(Furamide) is not commercially available in the USA or Canada (only being available from the Centers for Disease Control and Prevention). A direct comparison of efficacy showed that Paromomycin had a higher cure rate . Recommended dosage: Metronidazole 750mg tid orally, for 5 to 10 days FOLLOWED BY Paromomycin 30mg/kg/day orally in 3 equal doses for 5 to 10 days or Diloxanide furoate 500mg tid orally for 10 days, to eradicate lumenal amoebae and prevent relapse . |-

Additional images

See also

List of parasites (human)
List of parasites (human)

EndoparasitesProtozoan organismsHelminths organisms Other organismsEctoparasites...

External links

CDC
Centers for Disease Control and Prevention

The Centers for Disease Control and Prevention is an agency of the United States United States Department of Health and Human Services based in Atlanta, Georgia, United States adjacent to the campus of Emory University and northeast of downtown Atlanta....

LSHTM

Public domain from the Bad Bug Book
Bad Bug Book

The Bad Bug Book is a public domain online publication about foodborne illnesses.It was prepared in 1992 by the Center for Food Safety and Applied Nutrition, a division of the U.S. Food and Drug Administration....
, from which the original version of this article was adapted.