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[Acanthamoeba spp.] [Balamuthia mandrillaris] [Naegleria fowleri] [Sappinia spp.]

Naegleria fowleri has three stages in its life cycle: cysts , trophozoites , and flagellated forms .  The trophozoites replicate by promitosis (nuclear membrane remains intact) .  N. fowleri is found in fresh water, soil, thermal discharges of power plants, geothermal wells, and poorly-chlorinated swimming pools.  Trophozoites can turn into temporary non-feeding flagellated forms which usually revert back to the trophozoite stage.  Trophozoites infect humans or animals by penetrating the nasal mucosa and migrating to the brain via the olfactory nerves causing primary amebic meningoencephalitis (PAM).  N. fowleri trophozoites are found in cerebrospinal fluid (CSF) and tissue, while flagellated forms are occasionally found in CSF.  Cysts are not seen in brain tissue.