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Key Features

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


  • 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

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


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



  • Amphotericin B is drug of choice

  • Four survivors in North America were treated with amphotericin B, rifampin, and other agents



  • Nearly always fatal

When to Admit

  • All patients with confirmed or suspected disease


Jahangeer  M  et al. Naegleria fowleri: sources of infection, pathophysiology, diagnosis, and management; a review. Clin Exp Pharmacol Physiol. 2020;47:199.
[PubMed: 31612525]  

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