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Section 3. Summaries of Infectious Diseases
Amebic Meningoencephalitis and Keratitis
(Naegleria fowleri, Acanthamoeba species, and Balamuthia mandrillaris)
Clinical ManifestationsEtiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures
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CLINICAL MANIFESTATIONS
Naegleria fowleri can cause a rapidly progressive, almost always fatal, primary amebic meningoencephalitis. Early symptoms include fever, headache, vomiting, and sometimes, disturbances of smell and taste. The illness progresses rapidly to signs of meningoencephalitis, including nuchal rigidity, lethargy, confusion, and altered level of consciousness. Seizures are common. Death occurs within a week of onset of symptoms. No distinct clinical features differentiate this disease from fulminant bacterial meningitis.
Granulomatous amebic encephalitis caused by Acanthamoeba species and Balamuthia mandrillaris has a more insidious onset and progression of manifestations occurring weeks to months after exposure. Signs and symptoms may include personality changes, seizures, headaches, nuchal rigidity, ataxia, cranial nerve palsies, hemiparesis, and other focal deficits. Fever often is low grade and intermittent. The course may resemble that of a bacterial brain abscess or a brain tumor. Chronic granulomatous skin lesions (pustules, nodules, ulcers) may be present without central nervous system involvement, particularly in patients with acquired immunodeficiency syndrome, and lesions may present on the midface for months before brain involvement in immunocompetent hosts.
Amebic keratitis, usually attributable to Acanthamoeba species, occurs primarily in people who wear soft contact lenses. The most common symptoms are pain (often out of proportion to clinical signs), photophobia, tearing, and foreign body sensation. Characteristic clinical findings include radial keratoneuritis and stromal ring infiltrate. Amebic keratitis generally follows an indolent course and initially may resemble herpes simplex or bacterial keratitis; delay in diagnosis is associated with worse outcomes.
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ETIOLOGY
N fowleri, Acanthamoeba species, and B mandrillaris are free-living amebae that exist as motile, infectious trophozoites and environmentally hardy cysts.
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EPIDEMIOLOGY
N fowleri is found
Related Article
Red Book 2009 2009: 783-816.