Clinical Background
Acanthamoeba and Naegleria are the most common free-living amoeba associated with human disease. Balamuthia mandrillaris and Hartmannella species are also free-living amoeba, but less commonly cause clinically significant infections.
- Pathogenic species may cause fatal central nervous system (CNS) disease
Epidemiology
- Incidence - acanthamoeba keratitis - .3-1/100,000
- Transmission - contaminated water or soil
Organisms
- Acanthamoeba pathogenic species that infect humans:
- A. culbertsoni
- A. castellanii
- A. polyphaga
- A. astronyxis
- Naegleria pathogenic species that infect humans:
- N. fowleri is the only species that infects humans
- Balamuthia mandrillaris
- Hartmannella species
Risk Factors
- Acanthamoeba infection
- Keratitis
- Hydrogel contact lens wearers with poor hygienic practices
- Patients exposed to contaminated water
- Meningitis
- Almost exclusively in patients with HIV, cirrhosis, systemic lupus erythematosus and diabetes mellitus
- Naegleria infection
- Correlates with history of swimming in lakes or brackish water
- Aspiration of contaminated water, inhalation of contaminated dust
- Immunosuppression is a risk factor for infection from all free-living amoebas
Clinical Presentation
- Acanthamoeba
- Chronic granulomatous amoebic encephalitis
- Headache, stiff neck, cranial nerve involvement, fever, hemiparesis, ataxia
- Ocular
- Corneal ulcers, keratitis, anterior ureitis
- Chronic granulomatous skin lesions
- Balamuthia mandrillaris
- Amoebic encephalitis
- Chronic granulomatous skin lesions (papulonodular, erythematosus, possible ulceration)
- Oral cavity lesions ( palate deformity)
- Naegleria
- Primary amoebic encephalitis
- Acute onset of headache, fever, cranial nerve involvement, stiff neck, nausea, vomiting
- Almost always fatal within 4-6 days
See Also
Diagnosis
Diagnosis
- Laboratory testing
- Acanthamoeba or Balamuthia
- Histopathological diagnosis (brain or skin biopsy) using traditional stains, immunofluorescence, or molecular assays
- Culture (CSF, eye)
- Naegleria
- CSF examination for trophozoites with Wright’s or Giemsa stain
- Histopathologic diagnosis (brain biopsy) using traditional stains, immunofluorescence, or molecular assays
- Culture (CSF, eye)
Differential diagnosis
- Central nervous system disease - viral , bacterial or fungal meningitis
- Corneal disease - herpes simplex virus, adenovirus
- Skin disease - dimorphic fungal or mycobacterial infections
Tests generally appear in the order most useful for common clinical situations
| Test name: Acanthamoeba Culture
|
| ARUP #: 0060245 |
| Methodology: Culture/Microscopic Identification
|
| Use: Diagnose Acanthamoeba spp, Naegleria spp and other free-living amoeba in
- CSF
- Corneal scrapings or tissue
- Vitreous fluid specimens |
| Limitations: |
| Follow-up:
|
| Test name: Acanthamoeba Stain
|
| ARUP #: 0060250 |
| Methodology: Calcofluor White/Microscopic Exam
|
| Use: Detect Acanthamoeba spp, Naegleria spp and other free-living amoeba |
| Limitations: |
| Follow-up:
|
References
General References
Craun GF, Calderon RL, Craun MF. Outbreaks associated with recreational water in the United States. Int J Environ Health Res.
2005;
15(
4):
243-262.
Hammersmith KM. Diagnosis and management of Acanthamoeba keratitis. Curr Opin Ophthalmol.
2006;
17(
4):
327-331.
Khan NA. Acanthamoeba: biology and increasing importance in human health. FEMS Microbiol Rev.
2006;
30(
4):
564-595.
Schuster FL, Visvesvara GS. Free-living amoebae as opportunistic and non-opportunistic pathogens of humans and animals. Int J Parasitol.
2004;
34(
9):
1001-1027.
Szenasi Z, Endo T, Yagita K, Nagy E. Isolation, identification and increasing importance of 'free-living' amoebae causing human disease. J Med Microbiol.
1998;
47(
1):
5-16.
Medical Reviewers
Petti, Cathy A., M.D. Medical Director, Infectious Diseases at ARUP Laboratories; Assistant Professor, Pathology and Medicine, University of Utah
Comprehensive Review: November 2007
Last Update: November 2007
