Balantidium coli

• Largest protozoan

Background

Microbiology

• Largest protozoan
• Only ciliated protozoan that infects humans

Epidemiology

• Worldwide distribution but most common in Latin America, Southeast Asia, Papua New Guinea, and the Middle East
• Found in contaminated food and water
• Domestic and wild pigs are the main reservoir, but has been found in other mammals

Life Cycle

• Ingestion of cysts
• In the small bowel, the cysts release trophozoites
• Trophozoites migrate to the large bowel, where they form cysts in the bowel wall and reproduce

Clinical Presentation

• Mostly asymptomatic
• Can cause a chronic intermittent diarrhea with abdominal pain and weight loss
• Rarely presents with bloody stools and fulminant colitis
  • May be complicated by intestinal perforation
• Case reports of pulmonary and urinary tract infections

Diagnosis

• Stool O&P for rapidly motile trophozoites
  • Cysts are rarely seen

Management

• First-line: tetracycline 500 mg po qid for 10 days
• Alternatives:
  • metronidazole 750 mg po tid for 5 days
  • iodoquinol 650 mg po tid for 20 days