Naegleria fowleri

Naegleria fowleri (also known as the brain eating amoeba) is a ubiquitous, free living amoeba typically grows contaminated, warm (25–35 °C / 77–95 °F), fresh water (e.g. lakes or hot springs). It belongs to a group called the Percolozoa or Heterolobosea. N. fowleri is transmitted to the humans through the nose when individuals swim/dive in lakes. Drinking contaminated water, however, does not result in transmission. N. fowleri causes primary amebic meningoencephalitis (PAM), a rare disease whereby N. fowleri invades the human central nervous system through the cibriform plate and causes fulminant fatal meningoencephalitis in the majority of cases.^[1][2]

• Phylum = Percolozoa
• Class = Heterolobosea
• Order = Schizopyrenida
• Family = Vahlkampfiidae
• Genus = Naegleria
• Species = N. fowleri
• Binomial = Naegleria fowleri

Shown below is an the life cycle of N. fowleri:

• N. fowleri grows ideally at 42 °C (108 °F), but it can tolerate temperatures as high as 45 °C (113 °F).^[3]
• There are 3 morphological stages in the life cycle of Naegleria fowleri:^[3]

• Trophozoite: 10-30 mu – Infective stage characterized by the presence of contractile vacuoles. It reproduces by binary fission. It uses pseudopods structure to ingest other organisms, red blood cells, and white blood cells.
• Flagellate: A temporary stage when the organism is exposed to changes in pH (e.g. from culture to distilled water).
• Cyst: 7-14 μm – A resistant stage whereby the organism is protected by a dense cell wall that can tolerate harsh environments, such as cold weather or states of low nutrition. Cysts may be transmitted to the human host and transformed into trophozoites.

• N. fowleri is a facultatively aerobic, heterotrophic organism.^[4]
• In its trophozoite form, it may appear either ameboid or flagellated.
• It contains the following structures for survival and growth:

• Mitochondria
• Pseudopods
• Flagella
• Contractile vacuoles

• N. fowleri invades the central nervous system (highly oxygenated environment) and causes meningoencephalitis.^[3]
• N. fowleri is transmitted to humans via the nasal cavity into the cribriform plate.
• It invades the subarachnoid spaces by migrating along the mesaxonal of unmyelinated olfactory nerves.
• When it reaches the subarachnoid space, it may then disseminate to other tissues of the central nervous system.
• It migrates along the mesaxonal spaces of unmyelinated

• The natural reservoir of N. fowleri are typically fresh water lakes and hot springs.
• N. fowleri has also been isolated from:^[4]

• Soil
• Swimming pools
• Home showers
• Sewers
• Cooling towers

• Naegleria Infection fact sheet from the website of the Centers for Disease Control and Prevention