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Amebiasis is an infection by the protozoan parasite, Entamoeba histolytica. The infection is acquired by ingestion of cysts in fecally contaminated food or water; excystation and infection occur in the large intestine.
After excystation, trophozoites attach to the intestinal wall and liberate extracellular enzymes that enable invasion of the mucosa and spread to other organs, especially the liver and lung where abscesses develop.
Amebiasis (or amebic dysentery) can cause bloody diarrhea accompanied by fever and prostration. Leukocytes, WBCs, and RBCs are found in the stools. Liver abscess can develop several weeks to months later producing hepatomegaly and fever.
Pathogenic (Entamoeba histolytica) and nonpathogenic (Entamoeba dispar) species of Entamoeba occur. Additionally, some of those infected with pathogenic strains are asymptomatic cyst carriers.
Intestinal amebiasis should be diagnosed by detected Entamoeba histolytica in stool specimens.
As an adjunct in the diagnosis of extraintestinal amebiasis, especially liver abscess
Serology may be particularly useful in supporting the diagnosis of amebic liver abscess in patients without a definite history of intestinal amebiasis and who have not spent substantial periods of time in endemic areas
A positive result suggests current or previous infection with Entamoeba histolytica.
Since pathogenic and nonpathogenic species of Entamoeba cannot be differentiated microscopically, some authorities believe a positive serology indicates the presence of the pathogenic species (ie, Entamoeba histolytica).
Previous episodes of intestinal amebiasis may produce a positive serology.
Serologic results should be used as an aid in diagnosis and should not be interpreted as diagnostic by themselves.
Direct detection of Entamoeba histolytica in stool specimens is recommended to diagnose intestinal amebiasis.
Expected values: negative
Bruckner DA: Amebiasis. Clin Microbiol Rev 1992;5:356-369