Figure 1 The traditional classiﬁcation scheme of (A) protozoan pathogens, and (B) free-living amoebae, based largely on morphological characteristics.
organisms have a common amoeboid motion, that is a crawling-like movement, they have been classiﬁed into several different groups. These include potent parasitic organisms such as Entamoeba spp. that were discovered in 1873 from a patient suffering from bloody dysentery and named E. histolytica in 1903. Among free-living amoebae, Naegleria was ﬁrst discovered by Schardinger in 1899, who named it Amoeba gruberi. In 1912, Alexeieff suggested its genus name Naegleria, and much later, in 1970, Carter identiﬁed Naegleria fowleri as the causative agent of fatal human infections (reviewed in De Jonckheere, 2002). In 1913, Puschkarew isolated an amoeba from dust, and later in 1931, the genus Acanthamoeba was created (Castellani, 1930; Douglas, 1930; Volkonsky, 1931). Balamuthia mandrillaris has only been discovered relatively recently in 1986 from the brain of a baboon that died of meningoencephalitis and was described as a new genus, Balamuthia (Visvesvara et al., 1990, 1993). Over the years, these free-living amoebae have gained increasing attention from the scientiﬁc community due to their diverse roles, in particular, in causing serious and sometimes fatal human infections (Figure 3).