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Balantidium coli infection

Peter F Weller, MD, MACP
Karin Leder, MBBS, FRACP, PhD, MPH, DTMH
Section Editor
Edward T Ryan, MD, DTMH
Deputy Editor
Elinor L Baron, MD, DTMH


Balantidium coli is the largest protozoan and the only ciliate parasite that infects humans [1,2].


Human balantidiasis occurs worldwide; it is most prevalent in tropical and subtropical regions and developing countries. B. coli generally occurs among domestic and wild mammals, especially among pigs in warmer climates and monkeys in the tropics. Infection in humans is therefore also more common in those areas, especially in settings where hygiene is poor. Porcine fecal contamination of water or food consumed by humans is the principal means for acquisition of infection by humans [3,4]. Transmission between humans can occur via the fecal-oral route.

Transmission of balantidiasis occurs via ingestion of cysts (figure 1). 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; conjugation may also 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 in the stool.


Three forms of B. coli infection can occur: asymptomatic cyst excretion, acute colitis, and chronic infection [5-8]. Most cases are asymptomatic; patients with debilitating conditions (particularly immunosuppression) or other infections are at increased risk for developing symptomatic infection [9-11].

In sporadic cases with acute clinical manifestations, symptoms include nausea, vomiting, diarrhea, weight loss, and abdominal pain. Stools may be either watery or dysenteric [7]. Fulminant disease is rare and is most frequently associated with fulminating dysentery with or without multiple intestinal perforations. When present, the colonic ulcers and clinical presentation are similar to those found in amebic dysentery with deep invasion of the submucosa with organisms. Microperforations with resulting sepsis can be a potentially fatal complication.

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Literature review current through: Nov 2017. | This topic last updated: Sep 28, 2016.
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