Parasite
Balantidium coli
Only ciliated protozoan that infects humans
bal-an-TID-ee-um KOH-lie
High-yield clue
A large, cilia-covered trophozoite with a kidney-bean-shaped macronucleus is the unmistakable study clue.
Overview
The only ciliated protozoan known to cause human disease, a large intestinal parasite associated with pigs as the reservoir. It matters as the classic ciliate contrast to amebic colon pathogens.
Classification
- Protozoa
- Ciliate
- Trophozoite + cyst stages
- Largest protozoan pathogen of humans
Lab & identification clues
- Cilia-covered motile trophozoite
- Kidney-bean macronucleus vocabulary
- Cytostome (mouth-pore) feature
- Stool ova-and-parasite exam concept
Associations
- Pigs as primary reservoir host
- Fecal-oral / contaminated-water transmission
- Colon-invasion / dysentery vocabulary
- Zoonotic epidemiology framing
Commonly confused with
- Entamoeba histolytica
- Cryptosporidium
Frequently asked questions
What is Balantidium coli?
The only ciliated protozoan known to cause human disease, a large intestinal parasite associated with pigs as the reservoir. It matters as the classic ciliate contrast to amebic colon pathogens.
What are the lab clues for Balantidium coli?
Lab clues for Balantidium coli include Cilia-covered motile trophozoite, Kidney-bean macronucleus vocabulary, Cytostome (mouth-pore) feature, and Stool ova-and-parasite exam concept.
What is Balantidium coli commonly confused with?
Balantidium coli is commonly confused with Entamoeba histolytica and Cryptosporidium.
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.