Pathogenic and Opportunistic Free-Living Ameba Infections

Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri are pathogenic and opportunistic free-living amebae (FLA) that primarily cause central nervous system (CNS) infections in humans and other animals. Acanthamoeba spp. cause chronic but fatal granulomatous amebic encephalitis (GAE) and disseminated infections of the skin and other organs in immunocompromised people; they can also cause Acanthamoeba keratitis, most frequently in association with contact lenses. B. mandrillaris causes a chronic but fatal GAE in both immunocompromised and immunocompetent people. N. fowleri causes an acute and fulminating primary amebic meningoencephalitis (PAM) in children and young adults with a history of recent nasal freshwater exposure and leads to death within 10 days. Diagnosis is based on identification of amebae in cerebrospinal fluid or tissue. There is no established treatment for FLA infections, and mortality is >90% for CNS infections.