''Balantidium'' is a ciliate protozoan found as a commensal in the lumen of the [[Large Intestine - Anatomy & Physiology|large intestine]]. It infects pigs and other animals, including humans. It is the only ciliate known to be pathogenic. | ''Balantidium'' is a ciliate protozoan found as a commensal in the lumen of the [[Large Intestine - Anatomy & Physiology|large intestine]]. It infects pigs and other animals, including humans. It is the only ciliate known to be pathogenic. |