DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/balantidium.
Balantidium coli, a large ciliated protozoan parasite.
Cysts are the parasite stage responsible for transmission of balantidiasis . The host most often acquires the cyst through ingestion of contaminated food or water . Following ingestion, excystation occurs in the small intestine, and the trophozoites colonize the large intestine . The trophozoites reside in the lumen of the large intestine of humans and animals, where they replicate by binary fission, during which conjugation may occur . Trophozoites undergo encystation to produce infective cysts . Some trophozoites invade the wall of the colon and multiply. Some return to the lumen and disintegrate. Mature cysts are passed with feces.
Worldwide. Because pigs are an animal reservoir, human infections occur more frequently in areas where pigs are raised. Other potential animal reservoirs include rodents and nonhuman primates.
Most cases are asymptomatic. Clinical manifestations, when present, include persistent diarrhea, occasionally dysentery, abdominal pain, and weight loss. Symptoms can be severe in debilitated persons.