Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home

Epidemiology & Risk Factors

Image of Balamuthia mandrillaris

Balamuthia mandrillaris Photo credit: CDC.

Image of a scraped knee with a bandaid being applied.

An open wound, such as a cut or scrape, may be a potential entry point for Balamuthia.

Balamuthia infection is very rare but often causes fatal disease[1]. Since Balamuthia was first discovered in 1986, about 200 cases of infection have been reported worldwide[2,3,4]. This number includes at least 70 confirmed cases in the United States. Because disease caused by Balamuthia is so uncommon, it is possible that there have been additional cases that were misdiagnosed [2,4].

Balamuthia amebas (single-celled living organisms) are thought to enter the body when soil containing Balamuthia comes in contact with skin wounds and cuts, or when dust containing Balamuthia is breathed in or gets in the mouth[1]. Once inside the body, the amebas can then travel to the brain and cause Granulomatous Amebic Encephalitis (GAE)[1]. GAE is a severe disease of the brain that is fatal in over 95% of cases[2]. It can take weeks to months to develop the first symptoms of Balamuthia GAE after initial exposure to the amebas[2,3].

Balamuthia amebas live freely in soil around the world[1-13]. Gardening, playing with dirt, or breathing in soil carried by the wind might increase the risk for infection[1,2,5]. Balamuthia might also be present in fresh water[1]. There have been reports of Balamuthia GAE infection in dogs that swam in ponds. However, there have been no reported human cases where the only potential exposure was swimming.

The Balamuthia ameba is able to infect anyone, including healthy people[1-6]. Those at increased risk for infection[1-4,6,10] include:

  • People with HIV/AIDS, cancer, liver disease, or diabetes mellitus
  • People taking immune system inhibiting drugs
  • Alcoholics
  • Young children or the elderly
  • Pregnant women

In the United States, Balamuthia infection might be more common among Hispanic Americans[6,13]. However, the cause of this trend is unknown and might be due to differences in exposure, biology, data collection, or other reasons[1,13-17]. More research is needed to understand what factors might be associated with increased reporting among persons of Hispanic ethnicity.

There have been no reports of a Balamuthia infection spreading from one person to another except through organ donation/transplantation.

This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.

  1. Visvesvara GS, Moura H, Schuster FL. Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp. , Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea. FEMS Immunol Med Microbiol. Jun 2007;50(1):1-26.
  2. Siddiqui R, Khan NA. Balamuthia amoebic encephalitis: an emerging disease with fatal consequences. Microb Pathog. Feb 2008;44(2):89-97.
  3. Perez MT, Bush LM. Balamuthia mandrillaris amebic encephalitis. Curr Infect Dis Rep. Jul 2007;9(4):323-328.
  4. Perez MT, Bush LM. Fatal amebic encephalitis caused by Balamuthia mandrillaris in an immunocompetent host: a clinicopathological review of pathogenic free-living amebae in human hosts. Ann Diagn Pathol. Dec 2007;11(6):440-447.
  5. Huang ZH, Ferrante A, Carter RF. Serum antibodies to Balamuthia mandrillaris, a free-living amoeba recently demonstrated to cause granulomatous amoebic encephalitis. J Infect Dis. May 1999;179(5):1305-1308.
  6. Maciver SK. The threat from Balamuthia mandrillaris. J Med Microbiol. Jan 2007;56(Pt 1):1-3.
  7. Balamuthia amebic encephalitis--California, 1999-2007. MMWR Morb Mortal Wkly Rep. Jul 18 2008;57(28):768-771.
  8. Schuster FL, Visvesvara GS. Free-living amoebae as opportunistic and non-opportunistic pathogens of humans and animals. Int J Parasitol. Aug 2004;34(9):1001-1027.
  9. Schuster FL, Visvesvara GS. Opportunistic amoebae: challenges in prophylaxis and treatment. Drug Resist Updat. Feb 2004;7(1):41-51.
  10. Martinez AJ, Visvesvara GS. Free-living, amphizoic and opportunistic amebas. Brain Pathol. Jan 1997;7(1):583-598.
  11. Bravo F, Sanchez MR. New and re-emerging cutaneous infectious diseases in Latin America and other geographic areas. Dermatol Clin. Oct 2003;21(4):655-668, viii.
  12. Dunnebacke TH, Schuster FL, Yagi S, Booton GC. Isolation of Balamuthia amebas from the environment. J Eukaryot Microbiol. 2003;50 Suppl:510-511.
  13. Schuster FL, Glaser C, Honarmand S, Maguire JH, Visvesvara GS. Balamuthia amebic encephalitis risk, Hispanic Americans. Emerg Infect Dis. Aug 2004;10(8):1510-1512.
  14. Schuster FL, Yagi S, Gavali S, et al. Under the Radar: Balamuthia Amebic Encephalitis. Clin Infect Dis. Apr 1 2009;48(7):879-887.
  15. Schuster FL, Visvesvara GS. Balamuthia mandrillaris. In: Khan N, ed. Emerging Protozoan Pathogens. London: Taylor & Francis; 2008.
  16. Schuster FL, Honarmand S, Visvesvara GS, Glaser CA. Detection of antibodies against free-living amoebae Balamuthia mandrillaris and Acanthamoeba species in a population of patients with encephalitis. Clin Infect Dis. May 1 2006;42(9):1260-1265.
  17. Schuster FL, Yagi S, Wilkins PP, Gavali S, Visvesvara GS, Glaser CA. Balamuthia mandrillaris, agent of amebic encephalitis: detection of serum antibodies and antigenic similarity of isolates by enzyme immunoassay. J Eukaryot Microbiol. Jul-Aug 2008;55(4):313-320.
Contact Us:
  • Centers for Disease Control and Prevention
    1600 Clifton Rd
    Atlanta, GA 30333
  • 1-800-CDC-INFO
    TTY: (888) 232-6348
    New Hours of Operation
    8am-8pm EST/Monday-Friday
    Closed Holidays
  • Page last reviewed: March 8, 2011
  • Page last updated: March 8, 2011 The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC-INFO