Balantidium coli

Background

• 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% . 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

• Entamoeba histolytica
• Shigella
• Salmonella
• Campylobacter
• E.coli
• IBD

Workup

• 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