The Amoeboid Protozoans Entamoeba histolytica Entamoeba histolytica (P) is the only medically significant amoeba (a-mē-ba). It causes amoebic dysentery (dis-in-ter-ē) and can cause ulcers in the large intestine. (Dysentery -frequent and painful diarrhea, often w/ blood and mucus.) It may be possible to find motile Entamoeba histolytica in a stool specimen, but cysts are more likely. Cysts form when fecal material is not favorable for trophozoites (trō-fah-zō-īt), such as too solid or too dry. Trophozoites are the active form, cysts are in stasis till conditions become favorable. Infection occurs when cysts are ingested by fecal contaminated food, water, hands, or other contaminants. Cysts (but not the trophozoites) can withstand hostile environments such as the acids of the stomach. Good personal hygiene, not using human manure as fertilizer, and water treatment are effective at preventing disease. Three results of infection by amoeba (amoebiasis, am-ih-bī-eh-sis), depends on health of the host & strain virulence: - asymptomatic w/ the trophozoites staying in the intestinal lumen doing little damage. As with many of the parasites well study, asymptomatic carriers are common and they may be passing millions of cysts per day. - invasive amebic dysentary characterized by diarrhea, colitis (colon inflammation), bloody stools and pain. Trophozoites invade the intestine which may result in death especially w/o adequate care. - extraintestinal amoebiasis (am-ih-bī-eh-sis): trophozoites invade the bloodstream and are carried elsewhere in the body, most often the liver. Liver abscesses may occur, more rarely abscesses occur elsewhere. The liver gets hit twice, as it is damaged by invading trophozoites and as it reacts to the bacteria, debris, toxins and other noxious materials resulting from intestinal ulceration.
Posted on: Sun, 02 Feb 2014 07:49:36 +0000
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