Four species of Entamoeba are morphologically indistinguishable, but molecular techniques show that they are different species: E histolytica (pathogenic) E dispar (harmless colonizer, more common) E moshkovskii (less common, uncertain pathogenicity) E bangladeshi (less common, uncertain pathogenicity) Amebiasis is caused by E histolytica and tends to occur in regions with poor socioeconomic conditions and poor sanitation.