Brain-Eating Amoeba 
Naegleria fowleri

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Brain-eating amoeba, also known as Naegleria fowleri, is a species of the genus Naegleria. It acts as both an amoeba and a flagellate, which is why this is classified as an ameboflagellate excavate. It is pathogenic to human beings. This amoeba causes fatal brain infection in humans known as amoebic meningoencephalitis (PAM).

Habitat

Naegleria fowleri is mostly found in 

• warm freshwater
• hot springs
• rivers &lakes
• geothermal well water
• discharge from an industrial power plant
• water heaters
• minimal chlorinated swimming pools(with residual chlorine levels under 0.5 g/m³)

Life Cycle of Naegleria fowleri

Naegleria fowleri is a thermophilic and free-living amoeba. This amoeba basically exists in three forms.

1. cyst stage
2. trophozoite stage
3. biflagellate stage 

1. Cyst stage

In the cyst stage, Naegleria fowleri protects itself from the harsh environmental conditions it enclosing a single cell under a single-layered structure about 7–15 micrometers in diameter. This single-layered structure protects the amoeba cell from food scarcity, cold temperature, overcrowding, water accumulation, and desiccation.

2. Trophozoite stage 

The trophozoite stage is also known as the infective phase. At this stage, Naegleria fowleri can actively feed and replicate by binary fission. During that phase, amoeba develop amoebastomes (one to 12 structures), that is known as suckers and food cups that they use for feeding by a mechanism known as trogocytosis. 

3. Flagellate stage 

At this stage, the amoeba is pear-shaped. During this phase, it can be inhaled into the nasal cavity while swimming or diving, and its flagellated form transforms into a trophozoite, which takes a few hours to change its stage.

Primary amoebic meningoencephalitis (PAM)

Naegleria fowleri causes a fatal brain infection known as Primary Amoebic Meningoencephalitis (PAM). This disease is also referred to as amoebic encephalitis or simply Naegleria infection. When Naegleria fowleri enters the body through the nose, it can travel to the brain via the cribriform plate, which is a part of the ethmoid bone that contains perforated olfactory nerves that convey smell from the nasal cavity to the brain. The symptoms of PAM can be similar to those of bacterial meningitis. Causes fatal infection of the brain called Primary amoebic meningoencephalitis (PAM). The other names of this fatal infection disease is known as amoebic encephalitis and simply known as simply Naegleria infection. Naegleria fowleri, when it enters the nasal cavity and further travels to the brain via the cribriform plate(i.e, known as part of the ethmoid bone that is perforated by olfactory nerves to the roof of the nasal cavity to convey smell to the brain). Symptoms may appear similar to bacterial meningitis.

How to prevent human infection?

Focus on precautions to be taken when swimming in warmer conditions to prevent water from entering the nose. While diving, wear a nose clip that helps prevent water from entering the nasal cavity.