Balantidium coli /bal′əntid″ē·əm/ [Gk, balantidion, little bag, kolon, colon] , the largest and the only ciliated protozoan species that is pathogenic to humans, causing balantidiasis. It is a normal inhabitant of the domestic hog and is transmitted to humans by the ingestion of cysts excreted in hog feces, occurring either during direct contact with pigs, handling of fertilizer that contains pig excrement, or contact with a water supply contaminated with excrement.
