Light micrograph of an Entamoeba histolytica trophozoite (centre, purple). A trophozoite is the active feeding stage of a protozoan's (single-celled organism) life cycle. Entamoeba histolytica is a parasitic organism that can cause amoebiasis. Amoebiasis infects the intestines causing ulceration, and symptoms including diarrhoea, cramps, fever and weight loss. If untreated, the amoeba can move to the liver and other organs, and the infection can prove fatal.