Balantidiasis

Balantidiasis is a protozoan infection caused by infection with Balantidium coli.

Balantidium Life Cycle

Symptoms

Usually asymptomatic in immunocompetent individuals, but the symptoms of balantidiasis include:

• Intermittent diarrhea
• Constipation
• Vomiting
• Abdominal pain
• Anorexia
• Weight loss
• Headache
• Colitis
• Marked fluid loss

The most common ones are intermittent diarrhea and constipation or inflammation of the colon combined with abdominal cramps and bloody stools.

Transmission

Balantidium coli is transmitted through the fecal-oral route. Humans can become infected by eating and drinking contaminated food and water that has come into contact with infective animal or human fecal matter. Infection can occur in several ways, including the following examples:

• eating meat, fruits, and vegetables that have been contaminated by an infected person or contaminated by fecal matter from an infected animal,
• drinking and washing food with contaminated water, or
• having poor hygiene habits.

Balantidium Coli - trophozoite.

Causal Agents

• Balantidium (=Neobalantidium) (=Balantioides) coli, a large ciliated protozoan, is the only ciliate known to be capable of infecting humans.
• It is often associated with swine, the primary reservoir host.
• Recent molecular analyses have suggested the need for taxonomic revision, and it is now sometimes referred to as Neobalantidium coli or Balantioides coli, although this nomenclature has neither been resolved nor widely adopted in the medical community.

Life Cycle

• Cysts are the stage responsible for transmission of balantidiasis.
• 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 and appendix 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, causing ulcerative pathology in the colon wall.
• Some return to the lumen and disintegrate. Mature cysts are passed with feces.

Signs and symptoms

• Most people infected with Balantidium coli experience no symptoms.
• Balantidium coli infects the large intestine in humans and produces infective microscopic cysts that are passed in the feces, potentially leading to re-infection or infection of others.
• People who are immune-compromised are the most likely to experience more severe signs and symptoms.
• These include persistent diarrhea, dysentery, abdominal pain, weight loss, nausea, and vomiting.
• If left untreated, perforation of the colon can occur.

Tests

Yes. Stool samples can be examined by a laboratory. Microscopic examination can detect Balantidium coli in the stool.

Treatment

Three medications are used most often to treat Balantidium coli: tetracycline, metronidazole, and iodoquinol. Tetracycline: adults, 500 mg orally four times daily for 10 days; children ≥ 8 years old, 40 mg/kg/day (max. 2 grams) orally in four doses for 10 days. (Tetracyclines are contraindicated in pregnancy and in children < 8 years old. Tetracycline should be taken 1 hour before or 2 hours after meals or ingestion of dairy products.)

Alternatives:

• Metronidazole: adults, 500-750 mg orally three times daily for 5 days; children, 35-50 mg/kg/day orally in three doses for 5 days.

OR

• Iodoquinol: adults, 650 mg orally three times daily for 20 days; children, 30-40 mg/kg/day (max 2 g) orally in three doses for 20 days. (Note: iodoquinol should be taken after meals.)

• Nitazoxanide: has been tried in small studies, which suggest some therapeutic benefit (adults, 500 mg orally twice daily for 3 days; children age 4-11 years old 200 mg orally twice daily for 3 days; children 1-3 years old 100 mg orally twice daily for 3 days).