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Left: EM image of Naegleria fowleri in its cyst stage. Center: EM image of Naegleria fowleri in its ameboid trophozoite stage. Right: EM image of Naegleria fowleri in its flagellated stage.

Naegleria fowleri (commonly referred to as the "brain-eating amoeba" or "brain-eating ameba"), is a free-living microscopic ameba*, (single-celled living organism). It can cause a rare** and devastating infection of the brain called primary amebic meningoencephalitis (PAM). The ameba is commonly found in warm freshwater (e.g. lakes, rivers, and hot springs) and soil. Naegleria fowleri usually infects people when contaminated water enters the body through the nose. Once the ameba enters the nose, it travels to the brain where it causes PAM, which is usually fatal. Infection typically occurs when people go swimming or diving in warm freshwater places, like lakes and rivers. In very rare instances, Naegleria infections may also occur when contaminated water from other sources (such as inadequately chlorinated swimming pool water or heated and contaminated tap water) enters the nose 1-4. You cannot get infected from swallowing water contaminated with Naegleria.

Left: EM image of Naegleria fowleri in its cyst stage. Center: EM image of Naegleria fowleri in its ameboid trophozoite stage. Right: EM image of Naegleria fowleri in its flagellated stage. Credit: DPDx and GS Visvesvara. See Videos and Photos of Naegleria fowleri  for further images.

 

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References
  1. Yoder JS, Eddy BA, Visvesvara GS, Capewell L, Beach MJ. The epidemiology of primary amoebic meningoencephalitis in the USA, 1962-2008. Epidemiol Infect. 2010;138(7):968-75.
  2. Visvesvara GS. Free-living amebae as opportunistic agents of human disease. [PDF - 13 pages] J Neuroparasitol. 2010;1.
  3. Marciano-Cabral F, Cabral G. The immune response to Naegleria fowleri amebae and pathogenesis of infection. FEMS Immunol Med Microbiol. 2007;51:243-59.
  4. CDC. Primary amebic meningoencephalitis associated with ritual nasal rinsing — St. Thomas, U.S. Virgin Islands, 2012. MMWR Morb Mortal Wkly Rep. 2013;62(45):903.

 
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