Naegleria fowleri

Naegleria fowleri is a "brain eating" amaeba, free-living excavate form of protist typically found in warm bodies of fresh water, such as ponds, lakes, rivers, and hot springs. It is also found in soil, near warm water discharges of industrial plants, and minimally chlorinated swimming pools, (there is no evidence of this amoeba living in ocean water) in an amoeboid or temporary flagellate stage.

LIFECYCLE

Naegleria fowleri exists in nature in three forms: a flagellate, an ameboid and a cyst.

Flagellate stage: A biflagellate form occurring when trophozites are exposed to a change in ionic concentration such as placement in distilled water. The transformation of trophozoites to flagellate form occurs within a few minutes.

Trophozoite stage: The reproductive stage of the protozoan organism, which grows fastest at around 42°C and proliferates by binary fission. In their free-living state, trophozoites feed on bacteria. In tissues, trophozoites phagocytize red blood cells and white blood cells and destroy tissue.

Cyst Stage: Trophozoites encyst due to unfavorable conditions. Factors that induce cyst formation can include food deprivation, crowding, desiccation, accumulation of waste products, and cold temperatures.

DISEASE caused by N FOWLERI

In humans, N. fowleri can invade the central nervous system via the nose, more specifically the olfactory mucosa and cribriform plate of the nasal tissues. The penetration initially results in significant necrosis of and hemorrhaging in the olfactory bulbs causing primary amoebic meningoencephalitis (PAM or PAME). PAM is a syndrome affecting the central nervous system, characterized by changes in olfactory perception (taste and smell), followed by vomiting, nausea, fever, headache, and the rapid onset of coma and death in two weeks.

It is found worldwide, most commonly, in:

• Warm bodies of fresh water, such as lakes, rivers
• Geothermal water such as hot springs
• Warm water discharge from industrial plants
• Minimally chlorinated swimming pools
• Soil

Intermediate organism in Naegleria fowleri life cycle (see CDC diagram)