Overview of Free-Living Amebas

Free-living amebas are protozoa that live independently in soil or water and do not require a human or animal host. They rarely cause disease, in contrast to the parasitic ameba Entamoeba histolytica, which is a common cause of intestinal infection (amebiasis). Pathogenic free-living amebas are of the genera Acanthamoeba, Balamuthia, Naegleria, and Sappinia.

Three major syndromes occur:

• Amebic keratitis

• Granulomatous amebic encephalitis

• Primary amebic meningoencephalitis

Acanthamoeba and Balamuthia can also cause skin lesions or disseminated disease in immunocompromised people.