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©2013 UpToDate ® Print Email Acanthamoeba life cycle Acanthamoeba spp have been found in soil; fresh, brackish, and sea water; sewage; swimming pools; contact lens equipment; medicinal pools; dental treatment units; dialysis machines; heating, ventilating, and air conditioning systems; mammalian cell cultures; vegetables; human nostrils and throats; and human and animal brain, skin, and lung tissues. Unlike N. fowleri , Acanthamoeba has only two stages, cysts (1) and trophozoites (2) , in its life cycle. No flagellated stage exists as part of the life cycle. The trophozoites replicate by mitosis (nuclear membrane does not remain intact) (3) . The trophozoites are the infective forms, although both cysts and trophozoites gain entry into the body (4) through various means. Entry can occur through the eye (5) , the nasal passages to the lower respiratory tract (6) , or ulcerated or broken skin (7) . When Acanthamoeba spp enters the eye, it can cause severe keratitis in otherwise healthy individuals, particularly contact lens users (8) . When it enters the respiratory system or through the skin, it can invade the central nervous system by hematogenous dissemination, causing granulomatous amebic encephalitis (GAE) (9) or disseminated disease (10) , or skin lesions (11) in individuals with compromised immune systems. Acanthamoeba spp cysts and trophozoites are found in tissue. * Results in severe keratitis of the eye (8) . • Results in granulomatous amebic encephalitis (9) (GAE) and/or disseminated disease (10) in individuals with compromised immune systems. Δ Results in granulomatous amebic encephalitis (9) (GAE), disseminated disease (10) , or skin lesions (11) in individuals with compromised immune systems. Reproduced from: Centers for Disease Control and Prevention. Parasites: Acanthamoeba. Available at: file://www.cdc.gov/parasites/acanthamoeba/biology.html .