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Naegleria fowleri Infection
(Brain-Eating Amoeba Infection) (cont.)

What is Naegleria fowleri?

Naegleria fowleri is an amoeba that lives in freshwater and soil. The organism goes through three stages in its life cycle: cysts, flagellates, and trophozoites. Cysts are highly stable in the environment and can withstand near-freezing temperatures. The flagellate form is an intermediate stage that does not consume nutrients or reproduce. The trophozoite form causes human disease. Naegleria are "thermophilic," meaning that they prefer warmer water. Thus, Naegleria infection is found both in tropical and temperate climates. The organism is commonly identified in freshwater, including rivers, lakes, and ponds, or in soil near these sources. Where the water temperature is cool, Naegleria may be found in the sediment at the bottom of lakes or in localized areas where warmer water is discharged into lakes. Naegleria fowleri does not exist in saltwater and is not found in the ocean.

Although there are many species of Naegleria, only Naegleria fowleri causes human infection. There are other free-living amoebas that cause human disease, including Acanthamoeba.