Colon nontumor
Infectious colitis (specific microorganisms)

Topic Completed: 1 June 2015

Revised: 8 January 2019, last major update June 2015

Copyright: (c) 2003-2017,, Inc.

PubMed Search: Balantidiasis [title] colon

Elliot Weisenberg, M.D.
Page views in 2018: 941
Page views in 2019 to date: 790
Cite this page: Weisenberg E. Balantidiasis. website. Accessed July 23rd, 2019.
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
  • 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
  • The trophozoite is oval and large, sometimes large enough to be seen without magnification (generally 30-150 μm in length x 20-120 μm in width, rarely up to 200 μm in length), contains circumferential cilia (B. coli is the only ciliated parasite that infects humans)
  • It is rapidly mobile
  • In tissue sections, the trophozoites are large with kidney-bean shaped nuclei and visible cilia
Microscopic (histologic) 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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