Balantidium coli


  • Infection of large intestine by parasite, Balantidium coli
    • Large, ciliated protozoan
    • Simple life cycle: dormant cyst to trophozoite to cyst
  • Reservoir host is pig (asymptomatic)
  • Pig sheds feces with cysts => contaminated water and food => ingested by humans => parasite resides in large intestine
  • Parasite usually resides in lumen of intestine but can also penetrate mucosa
    • Opportunistic infection
  • Human-to-human transmission via fecal-oral route as well
  • Worldwide prevalence 0.02-1%[1] and found wherever pigs are found
  • Risk factors:
    • Close contact between human and pigs
    • Lack of appropriate waste disposal that can contaminate drinking water sources
    • Subtropical/tropical climates (warmth and humidity favor survival of cyst)
    • Compromised immune system, elderly, malnourished, alcoholics

Clinical Features

  • Range of mild to severe disease
    • Asymptomatic hosts (usually immunocompetent)
    • Chronic infection: non-bloody diarrhea, cramping, abdominal pain
    • Fulminant balantidiasis: mucoid, bloody stools
    • Rarely, colonic perforation
  • Extra-intestinal cases are rare
    • Rarely infecting lungs causing pneumonia or pulmonary hemorrhage
    • Mostly seen in elderly or immunocompromised
  • Death is rare

Differential Diagnosis


  • Stool samples over several days (excretion of parasites can be erratic)
  • Wet mount slide preparation: large 150-200um ovoid shape with cilia, swimming aimlessly in circles
  • If suspect infection of pulmonary system, perform BAL


  • Metronidazole OR
    • Adults: 500-750mg tid x 5 days
    • Peds: 35-50mg/kg/day in 3 doses x 5 days (max: 2g/day)
  • Tetracycline OR
    • Adult: 500mg QID x 10 days
    • Peds (>8yo): 40mg/kg/day in 4 doses x 10 days (max: 2g/day)
  • Iodoquinol
    • Adults: 650mg tid x 20 days
    • Peds: 30-40mg/kg/day in 3 doses x 20 days (max: 2g/day)


  • Discharge in well-hydrated patient with uncomplicated disease
  • Admit if needing fluid hydration, fulminant balantidiasis, or any complication

See Also

External Links


  1. Schuster FL and Ramirez-Avila L. Current World Status of Balantidium coli. Clin. Microbiol. 2008; 21(4):626–638.