The Parasite: Balantidium coli

The Disease: Balantidiasis


ParaSite created by Ambili Ramachandran

Human Biology 103 Parasites and Pestilence: Infectious Public Health Challenges

Dr. D. Scott Smith, MD, MSc., DTM&H

Stanford University

Spring 2003





Balantidium coli is a protozoan parasite responsible for the disease Balantidiasis. Balantidium coli is the largest protozoan and the only ciliate known to parasitize humans.


Balantidium coli most commonly infects humans, other primates, and pigs, which are reservoirs of the parasite. The protozoa are found worldwide, and incidences of infection have been noted in Bolivia, Papua New Guinea, and the Philippines, yet usually with a prevalence of less than 1%. Infection is rare, but is likely to occur in places where humans live closely with swine and where water sanitation is poor or non-existent.


Balantidium coli cysts are released in the feces of infected hosts. Consequently, Balantidium coli is transmitted by a fecal-oral route: humans are infected by ingestion of water or food contaminated by feces containing the protozoa.


Balantidium coli infection is most often asymptomatic, but the parasite can invade the large intestine leading to diarrhea, dysentery (bloody diarrhea), colitis, and abdominal pain. This collection of symptoms is Balantidiasis, which can be treated effectively with antibiotics and can be prevented with proper hand washing practices, water treatment, separation of human and swine habitats, and proper waste disposal.


This website (or ParaSite) is designed to provide basic information on Balantidium coli and balantidiasis.





The Parasite


Life Cycle


Animal Reservoirs

Clinical Presentation





Public Health Interventions


Glossary of terms

References and links



Last updated May 23, 2003

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