Balantidium coli

Balantidium coli

Description, Causes and Risk Factors:

ICD-10: A07.0

Alternative Name: Balantidiasis, balantidosis, and balantidial dysentery.

Balantidium coli is a unicellular protozoan parasite with a length up to 200 mm, making it the largest of the human intestinal protozoa. The trophozoites are oval in shape and covered with cilia for motility. The cysts are 60-70 mm in length and resistant to unfavorable environmental conditions, such as pH (provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution where 7 is neutral and greater than 7 is more basic and less than 7 is more acidic) and temperature extremes. Balantidium coli belong to the largest protozoan group, the ciliates, with about 7200 species, of which only B. coli is known to infect humans.

Balantidium coli

Balantidium infection in humans is rare in the US. However, Balantidium is more common among pigs in warmer climates and in monkeys in the tropics.

Worldwide prevalence 1.2%-1%. Places include south & central America, Philippines, Iran, Central Asia, New Guinea (28%) & Pacific islands.

Balantidium coli is transmitted through the fecal-oral route. The host most often acquires the cyst through ingestion of contaminated food or water. 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, during which conjugation may 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 with feces.

Different species affecting different animals:

    Balantidium coli- humans.

  • Balantidium suis-pig.

  • Balantidium caviae-guinea pig.

  • Balantidium blatarum-cockroaches.

  • Balantidium jocularum- fish.


    Is able to survive both in aerobic as well as anaerobic conditions.

  • Carbohydrates are the main source of energy.

  • Has different enzymes which acts as virulence factors.

  • Peroxisomes-protects from oxidising agents.

  • Glucose phosphatase/alkaline phosphatase - glucose metabolism.

  • Hyaluronidase-helps in the invasion of the parasite. No toxins are secreted.

Humans can become infected by eating and drinking contaminated food and water that has come into contact with infective animal or human fecal matter.

Factors contributing to the disease:

    Persons who handle pigs like farmers, zookeepers, veterinarians, etc.

  • Infection in women is twice common as in men.

  • Immunosuppressive conditions.

  • Nutritional status.

  • Intestinal flora.

  • Parasitic load.

  • Achlorhydria.

Balantidium coli infection can be prevented when traveling to endemic tropical countries by following good hygiene practices. Wash your hands with soap and warm water after using the toilet, changing diapers, and before handling food. Teach children the importance of washing hands to prevent infection. Wash all fruits and vegetables with clean water when preparing or eating them, even if they have a removable skin.


Most infected individuals show no symptoms. Othersdevelop diarrhea, nausea, vomiting, anorexia andheadache. Recurrent diarrhea may persist for weeks tomonths.

Balantidium rarely invades the intestine. When it does, itproduces ulceration of the colon. Some of the ulcers mayextend to the muscular layer of the intestine. Although thenumber of these cases is small, extra-intestinal disease canoccur.


Differential Diagnosis: Mimics the dysenteryof E. histolytica (Entamoeba histolytica).

Diagnosis is based on detection of trophozoites in stool specimens or in tissue collected during endoscopy. Cysts are less frequently encountered. Balantidium coli is passed intermittently and once outside the colon is rapidly destroyed. Thus stool specimens should be collected repeatedly, and immediately examined or preserved to enhance detection of the parasite.

Diagnostic findings:

    Microscopy: Microscopic examination can detect Balantidium coli in the stool.

  • Morphologic comparison with other intestinal parasites.

Using anti-Balantidium rabbit serum the ciliates were immobilized within minutes.


The three medications often used to treat Balantidium coli are tetracycline, metronidazole, and iodoquinol. Carriers need to be treated. Till now no relapse and resistant is reported. See your health care provider for treatment care.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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