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Balantidiasis is an infectious disease produced by a single-celled microorganism (protozoan) called Balantidium coli that infects the digestive tract. It is primarily a disease of the tropics, although it is also found in cooler, temperate climates. Most persons with balantidiasis do not exhibit any noticeable symptoms (asymptomatic), but a few individuals will develop diarrhea with blood and mucus and an inflamed colon (colitis).


Balantidiasis is caused by Balantidium coli, a parasitic protozoan that infects the large intestine. B. coli is the largest and only protozoan, having cilia or hair-like structures, that is capable of causing disease in humans. Balantidiasis occurs most commonly in areas with poor sanitation and in settings where humans live in close contact with pigs, sheep, or goats.

Causes and symptoms

Balantidiasis is transmitted primarily by eating food or drinking water that has been contaminated by human or animal feces containing B. coli cysts. During its life cycle, this organism exists in two very different forms: the infective cyst or capsuled form, which cannot move but can survive outside the human body because of its thick, protective covering; and the disease-producing form, the trophozoite, which although capable of moving, cannot survive once excreted in the feces and, therefore, cannot infect others. In the digestive tract, the cysts are transported to the intestine where the walls of the cysts are broken open by digestive secretions, releasing the mobile trophozoites. Once released within the intestine, the trophozoites multiply by feeding on intestinal bacteria or by invading the lining of the large intestine. Within the lining of the large intestine, the trophozoites secrete a substance that destroys intestinal tissue and creates sores (ulcers) or abscesses. Trophozoites eventually form new cysts that are carried through the digestive tract and excreted in the feces. Under favorable temperature and humidity conditions, the cysts can survive in soil or water for weeks to months, ready to begin the cycle again.
Most individuals with balantidiasis have no noticeable symptoms. Even though these individuals may not feel ill, they are still capable of infecting others by person-to-person contact or by contaminating food or water with cysts that others may ingest, for example, by preparing food with unwashed hands.
The most common symptoms of balantidiasis are chronic diarrhea or severe colitis with abdominal cramps, pain, and bloody stools. Complications may include intestinal perforation in which the intestinal wall becomes torn, but the organisms do not spread to other parts of the body in the blood stream.


Diagnosis of balantidiasis, as with other similar diseases, can be complicated, partly because symptoms may or may not be present. A diagnosis of balantidiasis may be considered when a patient has diarrhea combined with a possible history of recent exposure to amebiasis through travel, contact with infected persons, or anal intercourse.
Specifically, a diagnosis of balantidiasis is made by finding B. coli cysts or trophozoites in the patient's stools or by finding trophozoites in tissue samples (biopsy) taken from the large bowel. A diagnostic blood test has not yet been developed.

Stool examination

This test involves microscopically examining a stool sample for the presence of cysts and/or trophozoites of B. coli.


To take a tissue sample from the large intestine, a procedure called a sigmoidoscopy is performed. During a sigmoidoscopy, a thin, flexible instrument is used to visually examine the intestinal lining and obtain small tissue specimens.


Patients with balantidiasis are treated with prescription medication, typically consisting of a ten day course of either tetracycline or metronidazole. Alternative drugs that have proven effective in treating balantidiasis include iodoquinol or paromomycin.

Key terms

Asymptomatic — Persons who carry a disease and are usually capable of transmitting the disease but who do not exhibit symptoms of the disease are said to be asymptomatic.
Biopsy — The removal of a tissue sample for diagnostic purposes.
Ciliated — Covered with short, hair-like protrusions, like B. coli and certain other protozoa. The cilia or hairs help the organism to move.
Colitis — An inflammation of the large intestine that occurs in some cases of balantidiasis. It is marked by cramping pain and the passing of bloody mucus.
Protozoan — A single-celled, usually microscopic organism, such as B. coli, that is eukaryotic and, therefore, different from bacteria (prokaryotic).
Sigmoidoscopy — A procedure in which a thin, flexible, lighted instrument, called a sigmoidoscope, is used to visually examine the lower part of the large intestine.


Although somewhat dependent on the patient's overall health, in general, the prognosis for most patients with balantidiasis is good. Severely infected patients occasionally die as a result of a tear in the intestinal wall (intestinal perforation) and consequent loss of blood.


There are no immunization procedures or medications that can be taken prior to potential exposure to prevent balantidiasis. Moreover, people who have had the disease can become reinfected. Prevention requires effective personal and community hygiene. Specific safeguards include the following:
  • Purification of drinking water. Water can be purified by filtering, boiling, or treatment with iodine.
  • Proper food handling. Measures include protecting food from contamination by flies, cooking food properly, washing one's hands after using the bathroom and before cooking or eating, and avoiding foods that cannot be cooked or peeled when traveling in countries with high rates of balantidiasis.
  • Careful disposal of human feces.
  • Monitoring the contacts of balantidiasis patients. The stools of family members and sexual partners of infected persons should be tested for the presence of cysts or trophozoites.



Goldsmith, Robert S. "Infectious Diseases: Protozoal & Helminthic." In Current Medical Diagnosis and Treatment, 1998, edited by Stephen McPhee, et al., 37th ed. Stamford: Appleton & Lange, 1997.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


infection by protozoa of the genus Balantidium; in man, B. coli may cause diarrhea and dysentery, with ulceration of the colon mucosa.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


A disease caused by the presence of Balantidium coli in the large intestine; characterized by diarrhea, dysentery, and occasionally ulceration.
Farlex Partner Medical Dictionary © Farlex 2012


Infection with the intestinal ciliate Balantidium coli.
Human infection—balantidiosis—is linked to pig farming and slaughtering.
Clinical findings
Generally asymptomatic; heavy trophozoite loads result in bloody dysentery, severe dehydration or death; some patients have intestinal ulcers or mesenteric lymphadenitis, with extension to the liver, lung, etc.

Tetracycline, metronidazole.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


Parasitology Infection with the intestinal ciliate, Balantidium coli Epidemiology Human infection–balantidiosis–is linked to pig farming and slaughtering Clinical Generally asymptomatic; heavy trophozoite loads results in bloody dysentery, severe dehydration or death; some Pts have intestinal ulcers, mesenteric lymphadenitis with extension to the liver, lung etc Management Tetracycline, metronidazole
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


A disease caused by the presence of Balantidium coli in the large intestine; characterized by diarrhea, vomiting, weight loss, dysentery, and occasionally ulceration.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A kind of DYSENTERY caused by infection with the ciliated protozoon Balantidium coli , an organism that is often present in the bowels of people with no symptoms. This is the largest protozoan parasite of humans. The condition resembles AMOEBIC DYSENTERY and large ulcers form in the lining of the colon. Severe attacks are commoner in poorly nourished people. The condition is treated with TETRACYCLINE or METRONIDAZOLE.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Angles et al., "Balantidiasis in Aymara children from the northern Bolivian Altiplano," American Journal of Tropical Medicine and Hygiene, vol.
Prevalence, hematology, and treatment of balantidiasis among donkeys in and around Lahore, Pakistan.
coli infection in a public health due to the fact that some of NHPs were symptomless carriers, and they could transfer the parasite without any clinical signs of balantidiasis (Walker, 1913; Cockburn, 1948).
In addition, the role of baboons as potential reservoirs and possible source for zoonotic transmission should not be underestimated, because of the importance of balantidiasis in public health.
Balantidiasis: report of a fatal case with appendicular and pulmonary involvement.
He however said that the baseline for the number of transmittable diseases was 250, which include Anthrax, Babesiosis, Balantidiasis, Brucellosis, Cholera, Cowpox, Dengue fever, Congo and others.
Pigs may be the primary reservoir; consequently, balantidiasis is a greater risk among pig or pig manure handlers.
(4,5) Immunocompromised individuals appear to be less resistant to balantidiasis. (2) Pulmonary involvement has been reported in a leukaemic patient and a patient with anal cancer.