Infectious colitis


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PubMed Search: Balantidiasis [title] colon

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Balantidiasis. website. Accessed October 2nd, 2023.
Definition / general
  • Disease caused by the ciliate protozoan Balantidium coli
  • B. coli is found worldwide, but disease occurs most commonly in parts of the developing world including Latin America, Southeast Asia, Papua New Guinea and parts of the Middle East
  • Estimated prevalence is 1% in Aymara children in northern Bolivia (Am J Trop Med Hyg 1998;59:922);and 0.4% in rural northeast Thailand (Korean J Parasitol 2013;51:727)
  • Very low prevalence in industrialized countries
  • Humans are usually resistant to infection; disease generally occurs in debilitated or poorly nourished patients
  • Pigs are the primary reservoir for human infection and most cases occur in people in close proximity to pigs, although rats and other mammals may also transmit disease
  • Human to human transmission is also described
  • Infection by ingesting fecally contaminated food or water or from ingesting cysts due to other direct contact with pig or rat excrement
  • Excystation occurs in the small intestine and trophozoites migrate to the colon
  • Invasion into the intestinal wall occurs, where they multiply and cyst formation occurs
Diagrams / tables

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Life cycle

Clinical features
  • Most infections are asymptomatic
  • Symptomatic patients generally suffer disease similar to amebiasis, with diarrhea, dysentery, abdominal pain and weight loss
  • Chronic disease is most common, although fulminant colitis may occur, including perforation leading to peritonitis
  • Disease in the lung, urinary bladder and bone has been described (see case reports)
  • Similarly to E. histolytica, B. coli causes flask shaped ulcers in the large intestine, most commonly in the cecum and rectosigmoid
  • Neobalantidium coli is the largest protozoan parasite and only pathogenic ciliate to infect humans (Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 532 [Accessed 23 August 2019])
  • Diagnosis is usually made by identification of mobile trophozoites in fresh stool or scraped from an ulcer seen during endoscopy
  • Rarely the diagnosis is made by examination of urine or bronchioalveolar lavage fluid, or by identification in biopsy or resection specimens
Case reports
  • Tetracycline is the drug of choice
  • Alternative treatments include metronidazole, ampicillin, iodoquinol and nitazoxanide
  • Longer treatment is necessary if immunosuppressed
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Bobbi Pritt, M.D., Richard Bradbury, Ph.D. and Sarah Sapp, Ph.D.

Cyst and trophozoite of Neobalantidium coli (also known as Balantidioides) obtained from West African baboon

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Various images

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Trophic stage (EM)

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Intestinal lumen

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Encysted ciliate

Electron microscopy description
  • Flattened oval organism covered with cilia with gullet at anterior end
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