2. Human Parasites Parasitic diseases in humans are caused by protozoans and helminthes. The cysts and trophozoite forms of protozoans are most often found in feces but are also found in other tissues or excreta. The helminthes are most often detected by the presence of their eggs in feces; but these, too, can be found in tissues or other excreta. http://www.dmacc.cc.ia.us/instructors/human.htm[New Window]