II. Pathophysiology
- Exposure via fresh water and moist soil
- Transmission via respiratory route or via broken skin
III. Causes
- Acanthamoeba
- Genus of motile, unicellular eukaryotic amoebae with spiny surface projections (acanthopodia)
- Free-living amoeba found in fresh water and moist soil
- Cause infections in Immunocompromised patients (e.g. AIDS)
- Other infections due to Acanthamoeba
- Cutaneous acanthamebiasis
- Amoebic Keratitis (including Contact LensKeratitis)
- Balamuthia mandrillaris
- Free-living soil amoeba causing Encephalitis in both immunocompetent and Immunocompromised patients
- Also causes Granulomatous skin lesions (which may precede Encephalitis)
- Infections are not uncommon, but typically asymptomatic
- However amoebic Encephalitis is fatal in most cases
IV. Findings
- Gradual onset of Granulomatous Encephalitis
V. Labs
- Acanthamoeba
- Trophozoites and cysts may be seen on microscopy of stained tissue samples
- Organisms are elusive on CSF samples
- Balamuthia mandrillaris
- Immunofluorescence or Immunoperoxidase staining of tissue sample
- PCR may be available
VI. Differential Diagnosis
- See Meningitis
- See Encephalitis
-
Primary Amebic Meningoencephalitis (Naegleria Fowleri)
- Acute, rapidly progressive and rapidly fatal
VII. Management: Adults
- Acanthamoeba
- Start
- Pentamidine IV AND
- Fluconazole IV AND
- Miltefosine 50 mg orally three times daily
- Additional agents may be added
- Start
- Balamuthia mandrillaris
- Start
- Albendazole AND
- Fluconazole or Itraconazole AND
- Miltefosine 50 mg orally three times daily
- Additional agents may be added
- Start
VIII. References
- Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 339-40
- Freedman (2024) Amebic Meningoencephalitis, Sanford Guide, accessed 6/25/25