Balantidiasis (also known as balantidiosis) is defined as large-intestinal infection with Balantidium coli, which is a ciliated protozoan (and the largest protozoan that infects humans). B coli is known to parasitize the colon, and pigs may be its primary reservoir.

B coli exists as a trophozoite and a cyst and usually affects the large intestine, from the caecum to the rectum. The trophozoites replicate by binary fission and conjugation, and they subsist on bacteria. Humans ingest infective cysts, which then migrate to the large intestine, cecum, and terminal ileum. The organisms primarily dwell in the lumen but can also penetrate the mucosa and cause ulcers. B coli produces hyaluronidase, potentially enhancing its ability to invade the mucosa.

Balantidiasis tends to be more common among persons who handle pigs. Most cases of balantidiasis in immunocompetent individuals are asymptomatic. Mortality rates associated with acute and fulminating types of balantidiasis were as high as 30% in untreated patients prior to the introduction of antibiotics. Pneumonia has been described in patients with cancer-related immunosuppression.


Potential symptoms of balantidiasis include the following:

  • Diarrhea (watery, bloody, mucoid)
  • Nausea
  • Vomiting
  • Abdominal pain
  • Anorexia
  • Weight loss
  • Headache
  • Mild colitis
  • Fever
  • Severe and marked fluid loss (resembling amebic dysentery)
  • Dysenteric syndrome


Risk factors for balantidiasis include contact with pigs, handling fertilizer contaminated with pig excrement, and living in areas where the water supply may be contaminated by the excrement of infected animals. Poor nutrition, achlorhydria, alcoholism, and immunosuppression may also be contributing factors.


  • LAbarator examination – On unstained specimens, the trophozoite is recognized by its large size (approximately 50-100 µm in length and 40-70 µm in width), a short ciliary covering, and its spiraling motility.
  • Colonoscopy – Perform an endoscopic examination of the colon to obtain a biopsy of ulcers, thereby aiding in diagnosis of balantidiasis. Obtain the specimens from the periphery of ulcers.
  • Computed tomography (CT) scanning may reveal pulmonary parenchymal and lymph node involvement, as well as involvement of other organ systems.

B coli can invade the mucosa and submucosa, causing ulceration and infiltration with polymorphonuclear cells, lymphocytes, and eosinophils. Trophozoites can be observed at the invading edge of ulcers or at the periphery of submucosal abscesses.


  • Intestinal perforation
  • Extraintestinal spread to liver and mesenteric lymph nodes
  • Pneumonia


Special attention should be paid to volume replacement and electrolyte repletion in patients with balantidiasis who have severe diarrhea. Balantidiasis rarely manifests as acute appendicitis, which requires appendectomy.

The goals of pharmacotherapy are to reduce morbidity and to prevent complications. Prolonged courses of therapy may be required to cure balantidiasis in patients who are infected with HIV or who are otherwise immunosuppressed. Effective antibiotics – tetracycline, metronidazole, iodoquinol.


  • A clean water supply
  • Hygienic living conditions.
  • Avoiding contact with pigs


Other information






Infectious Disease Doctor

Do you want information about infectious diseases??