Description
Entamoeba histolytica is an anaerobe parasite forming cysts which have four small nuclei and measure 10- 15 µm in diameter. The cysts are sturdy and resist adverse environmental conditions. After ingestion by a susceptible host (invertebrates and vertebrates including humans), its wall is disrupted by the formation of a small opening through which an amoeba emerges. The amoeba divides serially through three cycles giving rise to eight uninucleate trophozoites from one cyst which are motile and measure 20-30 µm in diameter. Some of the trophozoites then invade the tissues of the large intestine and may erode them so extensively that they gain entrance into the bloodstream. Thus, amoebae can reach all parts of the body. Infection with Entamoeba histolytica has worldwide distribution. It is the causative agent of amoebiasis and amoebic dysentery and inhabits the lumen and mucosa of the large intestine, predominantly the transverse colon and cecum. Extra intestinal amoebiasis can afflict any organ or tissue. The majority of infected individuals are free of symptoms; this high incidence of asymptomatic carriers complicates matters. Those who are symptomatic experience a wide range of manifestations. Members of all age groups and both sexes are infected. The risk of infection increases with inadequate sanitary conditions. An increased prevalence of amoebiasis is found among people, who have an increased risk of exposure in the agricultural occupations and in male homosexuals.
Infection or presence of pathogen may be identified by:
Microscopy
PCR
Serology: e.g. ELISA