Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content + Print Section ++ For further information, see CMDT Part 35-08: Infections with Pathogenic Free-Living Amoebas + Key Features Print Section ++ ++ Essentials of Diagnosis ++ A fulminating, hemorrhagic, necrotizing meningoencephalitis Occurs in healthy children and young adults and is rapidly fatal ++ General Considerations ++ Caused by free-living amoebae Naegleria fowleri (most commonly) Balamuthia mandrillaris Acanthamoeba species The incubation period varies from 2 to 15 days ++ Demographics ++ N fowleri is a thermophilic organism found in Fresh and polluted warm lake water Domestic water supplies Swimming pools Thermal water Sewers Most patients give a history of exposure to warm fresh water + Clinical Findings Print Section ++ ++ Symptoms and Signs ++ Early symptoms include headache, fever, stiff neck, and lethargy, often associated with rhinitis and pharyngitis Vomiting, disorientation, and other signs of meningoencephalitis develop within 1 or 2 days, followed by coma and then death within 7–10 days ++ Differential Diagnosis ++ No distinctive clinical features distinguish the infection from acute bacterial meningoencephalitis + Diagnosis Print Section ++ ++ Laboratory Tests ++ Cerebrospinal fluid (CSF) shows hundred to thousands of leukocytes and erythrocytes per cubic millimeter Protein is usually elevated, and glucose is normal or moderately reduced A fresh wet mount of the CSF may show motile trophozoites Staining with Giemsa or Wright stain will identify trophozoites Species identification is based on morphology and immunologic methods + Treatment Print Section ++ ++ Medications ++ Amphotericin B is drug of choice Four survivors in North America were treated with amphotericin B, rifampin, and other agents + Outcome Print Section ++ ++ Prognosis ++ Nearly always fatal ++ When to Admit ++ All patients with confirmed or suspected disease + References Print Section ++ + +Bravo FG et al. Balamuthia mandrillaris infection of the skin and central nervous system: an emerging disease of concern to many specialties in medicine. Curr Opin Infect Dis. 2011 Apr; 24(2):112–7. [PubMed: 21192259] + +Grace E et al. Naegleria fowleri: pathogenesis, diagnosis, and treatment options. Antimicrob Agents Chemother. 2015 Nov;59(11):6677–81. [PubMed: 26259797] + +Lorenzo-Morales J et al. An update on Acanthamoeba keratitis: diagnosis, pathogenesis and treatment. Parasite. 2015;22:10. [PubMed: 25687209] + +Siddiqui R et al. Primary amoebic meningoencephalitis caused by Naegleria fowleri: an old enemy presenting new challenges. PLoS Negl Trop Dis. 2014 Aug 14;8(8):e3017. [PubMed: 25121759]