Amoebic dysentery (or amebic dysentery) is a type of bloody diarrhea caused primarily by the amoeba Entamoeba histolytica. Amoebic dysentery is transmitted through contaminated food and water. Amoebae spread by forming infective cysts which can be found in stools, and spread if whoever touches them does not sanitize their hands. There are also free amoebae, or trophozoites, that do not form cysts, however trophozoites do not survive long outside the human gastrointestinal tract, and are a purely diagnostic observation. Trophozoites are the agent responsible for symptoms.