Naegleria fowleri, commonly called “brain-eating amoeba”, is a species of the genus Naegleria, belonging to the phylum Percolozoa, which is technically not classified as a true amiable, but a shapeshifting amoeboflagellate excavation. It is a living, bacterial-eating microorganism which can be pathogenic, causing an unexpected, serious, and usually fatal, extremely rare brain infection called naegleriasis or primary amoebic meningoencephalitis (MAP). This microorganism is usually found in hot freshwater bodies, such as oceans, lakes, rivers, hot springs, hot water discharges from industrial or power plants, geothermal well water, poorly maintained or low chlorinated pools (less than 0.5 mg/m3 of tailings), water heater, ground, and pipes connected to tap water. It may be seen in an amoeboid step or temporary flagellate.
N. fowleri may cause an often deadly infection of the brain called naegleriasis (also known as primary amoebic meningoencephalitis, amoebic encephalitis/ meningitis, or simply Naegleria infection). Infections usually occur when water containing N.fowleri is inhaled by the nose, where it then penetrates the nasal and olfactory nervous tissue, moving towards the brain via the cribriform plaque.N.fowleri cannot cause infection through ingestion of contaminated water. Infections generally occur after swimming in warm fresh climate water, although there have been instances in colder climates such as Minnesota. In rare instances, the infection was caused by nasal flushing or sinuses with polluted water in a nasal flushing device such as a neti jar.
N. fowleri normally eats bacteria, but during human infections, the trophozoites consume astrocytes and neurons. The reason why N.fowleri prefers to pass through the cribriform plate has remained unknown, but the neurotransmitter acetylcholine has been suggested to act as a stimulus, as a structural homologous of the animal CHRM1 was shown to be present in Naegleria and Acanthamoeba. It takes one to nine days (an average of five) for symptoms to manifest following nasal exposure to N.fowleri flagellates.
Symptoms may include headache, fever, nausea, vomiting, loss of appetite, impaired mental status, coma, drooping eyelid, blurred vision, and loss of sense of taste. Later symptoms may include neck stiffness, confusion, carelessness, loss of balance, seizures, and hallucinations. When symptoms start to emerge, death usually takes place within two weeks. A person infected with N.fowleri is unable to transmit the infection to another person. Between 2009 and 2017, 34 infections were reported in the U.S.Although rarely observed, infection by Naegleria fowleri can occur in animals. Experimentally, mice, guinea pigs, and sheep were infected, with reports of South American tapirs and cattle on WFP. Animal infection is likely negligible.
Basic antimicrobial therapy consists of the antifungal amphotericin B, which inhibits the pathogen by binding to its membranous sterols, causing cell membrane disturbance and pathogen death; however, even with this treatment, the mortality rate is more than 95%.
New cures are needed. Miltefosine, a pest control drug that inhibits the pathogen by disrupting its PI3K/Akt/mTOR cellular survival signal pathway, has been utilized in some cases with mixed results.