ABSTRACT
Until 1986, members of only two genera of free-living amoebae were considered as agents of central nervous system (CNS) disease of humans: Acanthamoeba (several species) and Naegleria (Naegleria fowleri). However, there were several cases of meningoencephalitis where culture of the amoeba could not be established and amoebae that were seen in the tissues could not be speci‘cally identi‘ed by immunohistochemical tests. These unknown amoebae were considered as unidenti‘ed species of VahlkampŸa or Acanthamoeba because of the presence of cysts in the tissues (N. fowleri does not produce cysts in brain tissue) [1,2]. But in 1986 an amoeba was isolated from the brain tissue of a pregnant mandrill baboon that died in the San Diego Zoological Park after developing signs of meningoencephalitis. It was initially identi‘ed as leptomyxid amoeba (CDC:V039) [3] because of similarity of the cyst stage with that of Leptomyxa, a soil amoeba. Further studies including electron microscopy revealed that this amoeba was substantially different from the amoebae belonging to the family Leptomyxidae and
therefore, it was described as a new taxon and designated as Balamuthia mandrillaris [4]. The genus was named after the late Professor William Balamuth, an eminent protozoologist and a Professor of Zoology at the University of California, Berkeley, CA. The species designation denotes the source of the index isolate, the brain of a mandrill baboon. An antiserum to this amoeba (CDC:V039) produced in rabbits was found to be reactive only with Balamuthia and not with a number of different free-living and parasitic amoebae including Acanthamoeba, VahlkampŸa, Hartmannella, N. fowleri, Willaertia, and Entamoeba histolytica [3,4]. Subsequently, this anti-B. mandrillaris serum was used on tissue sections that were previously negative in the immuno›uorescence assay. The amoebae present in those tissue sections were found to be reactive with this new anti-serum, indicating that those cases of encephalitis were all caused by B. mandrillaris [2-7].
