The most commonly affected age group is 5–14-year olds (those who play in water). The number of cases of infection could increase due to climate change, which was posited as the reason for three cases in Minnesota in 2010, 2012, and 2015.As of 2013, the numbers of reported cases were expected to increase simply because of better-informed diagnoses being made both in ongoing cases and in autopsy findings. History
In 1899, Franz Schardinger first discovered and documented an amoeba he called Amoeba gruberi that could transform into a flagellate. The genus Naegleria was established by Alexis Alexeieff in 1912, who grouped the flagellate amoeba. He coined the term Naegleria after Kurt Nägler, who researched amoebae. It was not until 1965 that doctors Malcolm Fowler and Rodney F. Carter in Adelaide, Australia, reported the first four human cases of amoebic meningoencephalitis. These cases involved four Australian children, one in 1961 and the rest in 1965, all of whom had succumbed to the illness. Their work on amebo-flagellates has provided an example of how a protozoan can effectively live both freely in the environment, and in a human host.In 1966, Fowler termed the infection resulting from N. fowleri primary amoebic meningoencephalitis (PAM) to distinguish this central nervous system (CNS) invasion from other secondary invasions made by other amoebae such as Entamoeba histolytica. A retrospective study determined the first documented case of PAM possibly occurred in Britain in 1909. In 1966, four cases were reported in the US.
Diagnosis
N. fowleri can be grown in several kinds of liquid axenic media or on non-nutrient agar plates coated with bacteria. Escherichia coli can be used to overlay the non-nutrient agar plate and a drop of cerebrospinal fluid sediment is added to it. Plates are then incubated at 37 °C and checked daily for clearing of the agar in thin tracks, which indicate the trophozoites have fed on the bacteria.Detection in water is performed by centrifuging a water sample with E. coli added, then applying the pellet to a non-nutrient agar plate. After several days, the plate is microscopically inspected and Naegleria cysts are identified by their morphology. Final confirmation of the species identity can be performed by various molecular or biochemical methods.Confirmation of Naegleria presence can be done by a so-called flagellation test, where the organism is exposed to a hypotonic environment (distilled water). Naegleria, in contrast to other amoebae, differentiates within two hours into the flagellate state. Pathogenicity can be further confirmed by exposure to high temperature (42 °C): Naegleria fowleri is able to grow at this temperature, but the nonpathogenic Naegleria gruberi is not.