Amebic meningoencephalitis

CASES/YEAR
40 (US); 800 (Global)
CATEGORY
Sapronoses
AGENT TYPE
Protozoa
OTHER NAMES
Primary amebic meningoencephalitis (PAM); Acanthamoeba sp. meningoencephalitis; Balamuthia mandrillaris meningoencephalitis; Naegleria fowleri meningoencephalitis; Sappinia diploidea meningoencephalitis;
ACUITY
Acute-Severe
INCUBATION
24-48 hours; 2-14 days; 2-8 weeks; 2-24 months
INITIAL SYMPTOMS
PAM:, headache, olfactory hallucinations, nausea/vomiting, fever, nuchal rigidity, and lethargy; [CCDM]
PRECAUTIONS
No person-to-person transmission other than by organ transplant; [CCDM, p. 8]
COMMENTS
Naegleria fowleri is an ameba that lives in warm, fresh water lakes, ponds, and inadequately chlorinated pools. It causes primary amebic meningoencephalitis (PAM) by passing through the nasal mucosa and following the olfactory nerve to the brain. In the US, 121 cases of PAM were diagnosed from 1937 to 2007. Acanthamoeba species and Balamuthia mandrillaris amebae cause granulomatous amoebic encephalitis (GAE) mainly in immunocompromised or debilitated hosts. Current evidence suggests hematogenous spread of GAE to the CNS from sites of primary infection (skin, sinuses, and lungs). GAE caused by Acanthamoeba generally appears as space-occupying lesions by neuroimaging. Conjunctivitis and keratitis caused by Acanthamoeba can lead to blindness, and posterior chamber involvement is a rare complication. A case of chronic meningoencephalitis caused by Sappinia diploidea was reported in 2001 in a healthy 38 year old man. [CCDM, 6-9; PPID, p. 3059-69] Immunocompromised patients with GAE may develop skin lesions (nodules, ulcers, and pustules) and/or osteomyelitis. [Guerrant, p. 709, 1052] Naegleria fowleri causes PAM about 2-3 days after swimming in fresh water. [Cecil, p. 2047]
DIAGNOSTIC
PAM: wet prep of cerebral spinal fluid (motile trophozoites seen in 14 of 16 patients); GAE: Cysts in brain--test by IFA, IIF, and PCR; A multiplex real-time PCR assay can identify all 4 free-living ameba known to cause CNS disease. [PPID, p. 3065-6]
SCOPE
Global
SIGNS & SYMPTOMS
  • >fever
  • G nausea, vomiting
  • H leukocytosis
  • N confusion, delirium
  • N headache
  • N lethargy
  • N muscle weakness
  • N seizure
  • N stiff neck
  • O conjunctivitis, acute
  • S pustule
  • S skin or subcutaneous nodule
  • S ulcer of skin
  • *blindness
  • *brain abscess or lesion
  • *cranial neuropathy
  • *encephalitis
  • *meningitis
  • *myocarditis
  • *osteomyelitis
  • *paralysis
  • *pneumonitis
  • *stupor, coma
  • *uveitis
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
Inhalation, Swimming
SOURCE
Waterborne (Ingesting, Inhaling, or Swimming)
RESERVOIR
RISK FACTORS
  • AIDS patients
  • Cancer patients
  • Swim in contaminated water (ingestion or inhalation)
TREATMENT
See "Investigational Drug Available Directly from CDC for the Treatment of Infections with Free-Living Amebae." [CDC: August 23, 2013]
REFERENCES FOR CASES/YEAR
1. (US) 35 cases of Naegleria infection reported from 1998 to 2009; [Harrison ID, 2nd Ed, p. 1149] Calculate 35/12 = about 4 for US; Use correction factor of 10 for reported diseases;
2. (Global) 20 X US cases/yr;