It belongs to the phylum Percolozoa and is classified as an amoeboflagellate excavate,[1] an organism capable of behaving as both an amoeba and a flagellate.

This free-living microorganism primarily feeds on bacteria but can become pathogenic in humans, causing an extremely rare, sudden, severe, and almost always fatal brain infection known as naegleriasis or primary amoebic meningoencephalitis (PAM).

[12] The organism was named after Malcolm Fowler, an Australian pathologist at Adelaide Children's Hospital, who was the first author of the original series of case reports (British Medical Journal, starting 1965) of PAM.

To endure harsh environmental conditions, trophozoites transform into microbial cysts,[17] spherical, single-layered structures about 7–15 μm in diameter, enclosing a single cell nucleus.

Factors triggering cyst formation include food scarcity, overcrowding, desiccation, waste accumulation, and cold temperatures.

[18] As trophozoites, Naegleria fowleri may develop approximately 1 to 12 structures on their membrane known as amoebastomes, also referred to as "suckers" or "food cups," which they use for feeding via a trogocytosis-like mechanism.

The "flagellate-empty" hypothesis suggests that Naegleria's success may stem from decreased competition when thermosensitive protozoal fauna do not survive temperature changes.

This hypothesis implies that human disturbances, such as thermal pollution, increase the abundance of N. fowleri by eliminating its resource competitors.

Infections most often occur when water containing N. fowleri is inhaled through the nose (aspirated), where it then enters the nasal and olfactory nerve tissue, travelling to the brain through the cribriform plate.

The reason why N. fowleri passes across the cribriform plate is not known, but the neurotransmitter acetylcholine has been suggested as a stimulus precipitating the action, as a structural homolog of animal CHRM1 is present in Naegleria and Acanthamoeba.

[23][31] The true number of cases is likely to be higher than those reported due to problems relating to diagnosis, access to diagnostic testing and a lack of surveillance.

Experimentally, mice, guinea pigs, and sheep have been infected, and there have been reports of South American tapirs and cattle contracting PAM.

[30][36] Miltefosine, an antiparasitic drug that inhibits the pathogen via disrupting its cell survival signal pathway PI3K/Akt/mTOR,[34] has been used in a few cases with mixed results.

Therapeutic hypothermia reduces the body's temperature to a hypothermic state[39] to prevent further brain injury resulting from hyper inflammation and increased intracranial pressure.

Amoeba cultures and real-time polymerase chain reaction (PCR) studies for N. fowleri are diagnostic of PAM, but they are not readily available at most institutions and would have to be carried out at a reference laboratory.

[30] The clinical signs of PAM are similar to bacterial and viral meningitis, including fever, neck stiffness, and severe headaches.

It is critical that medical technologists consistently provide timely CSF evaluation, explore the diagnosis of PAM, and look for amoebae in the setting of meningitis, especially in summer.

[42][43] When irrigating sinuses or taking part in ritual cleansing of the nasal cavity, it is advised to use boiled or distilled water.

[23] A study was conducted on five separate hot springs found in Grand Teton National Park in search of the presence of Naegleria fowleri from July 2016 to March 2017.