Amebiasis is a disease caused by Entamoeba histolytica, which is a pseudopod-forming, non-flagellated protozoal parasite that causes proteolysis and tissue lysis. The genus Entamoeba contains many species, some of which can reside in human interstitial lumen, and considered non-pathogenic. E.histolytica is, thus far, the only species definitely associated with disease. The parasite exists in two forms, a cyst stage which is the infective form, and a trophozoite stage which is the form that causes invasive disease. Symptoms of amebiasis include diarrhea, stomach pain and cramping. It may also cause colitis, acute dysentery, or long-term diarrhea. The infection may spread through the blood to the liver and, rarely, to the lungs, brain or other organs.