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%^[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

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

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)

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