Amebiasis and "nonpathogenic" intestinal protozoa.

Infection with single or multiple species of intestinal protozoa is common in humans and can result in either asymptomatic colonization or symptoms of intestinal disease. Entamoeba histolytica serves as a paradigm for invasive colonic protozoal infection. The key to diagnosis and treatment of amebiasis is knowledge of the epidemiologic risk factors and clinical manifestations, a rational approach to diagnosis, and an understanding of the sites of action and uses of anti-amebic drugs. This knowledge of treatment provides a context for consideration of intestinal infection with less common protozoan pathogens such as Dientamoeba fragilis and Balantidium coli and 'nonpathogenic' protozoa such as Blastocystis hominis and Entamoeba coli.