Which of the following statements best describes the intestinal amebae?
Of the intestinal amebae, Entamoeba hamanni, E. coli, E. polecki, and E. nana are considered nonpathogenic. E. histolytica is distinctively characterized by its pathogenic potential for humans, although infection with this protozoan is commonly asymptomatic (causing "healthy carriers"). Symptomatic amebiasis and dysentery occur when the trophozoites invade the intestinal wall and produce ulceration and diarrhoea. Peritonitis can occur, with the liver the most common site of extraintestinal disease. The life cycle of the amebae is simple. There is encystment of the trophozoites, followed by excystation in the ileocecal region. The trophozoites multiply and become established in the cecum, where encystation takes place and results in abundant amebae, cysts, and trophozoites. Infection is spread by the cysts, which can remain for weeks or months in appropriately moist surroundings.
They are usually nonpathogenic
They are usually transmitted as trophozoites
They can cause peritonitis and liver abscesses
They occur most abundantly in the duodenum
Parasitology Pa 1 (Protozoology)