The causative agent of amoebiasis is a pathogenic protozoa (amoeba) called Entamoeba histolytica. E. histolytica is now recognized as a separate species from the closely related non-pathogenic Entamoeba dispar.
Distribution is worldwide with a higher prevalence in tropical and subtropical regions. The annual number of patients is approximately 40–50 million, with associated mortality around 0.1–0.2%.