Entamoeba dispar

In 1925 Emile Brumpt demonstrated, on the basis of epidemiological, clinical and in vivo experimental studies, the existence of two species that were biologically distinct but morphologically identical. One, Entamoeba histolytica, is pathogenic, while the other, Entamoeba dispar, is a simple commensal. The existence of two distinct species caused a dispute among scientists for decades until, in 1980, Brumptís findings were confirmed by the work of P.G. Sargeaunt by analyzing zymodemes from isolated culture strains. Later, in 1993, L.S. Diamond and C.G. Clark used molecular biology to prove the existence of two distinct species. Conversion in culture of non-pathogenic zymodemes (Entamoeba dispar) into pathogenic zymodemes (Entamoeba histolytica) is impossible due to genetic differences between the two species.  Any results that seem to contradict this statement are due to a contamination of cultures of a non-pathogenic strain with standard pathogenic strains.

For a description of the morphology of Entamoeba dispar cysts and trophozoites, see the section on Entamoeba histolytica. Co-infection with  Entamoeba histolytica is rather unusual.  Once again, remember that Entamoeba histolytica can be hematophagous.