Balantidiasis is a rare large-intestinal infection caused by a parasite called Balantidium coli. It is a ciliated protozoan (single-celled parasite) that is often associated with pigs since pigs are the primary reservoir hosts of this parasite. Balantidium coli is also known as the largest and the only known protozoan that can occasionally infect humans which mainly parasitizes the colon. Other potential hosts of this parasite include rodents and non-human primates.
Balantidium coli can be transmitted through contact with pig feces through a fecal-oral route by ingesting contaminated food and water. It exists in the developmental stages of either cyst or trophozoite. The cyst is the infectious stage acquired by ingesting contaminated food and water. It is the stage responsible for the transmission of the infection. When these contaminated food and water are digested, the trophozoite, the growing and feeding stage in the parasite’s life cycle, colonizes the large intestine by residing in the lumen of the large intestine and the appendix. During the colonization of the trophozoite, it replicates itself in a process called binary fission, which is the conjugation or the process of transferring genetic material between cells. The trophozoites then undergo encystation to produce cysts that will cause infection while some of the trophozoites invade the colon and multiply which causes ulcerative pathology.
Balantidiasis occurs worldwide, typically in tropical regions, and since pigs are the primary reservoir, human infections commonly occur in areas that raise pigs specially on poorly sanitized areas.
