Clinical Features:
Most cases are asymptomatic.  Clinical manifestations, when present, include persistent diarrhea, occasionally dysentery, abdominal pain, and weight loss.  Symptoms can be severe in debilitated persons.

Laboratory Diagnosis:
Diagnosis is based on detection of trophozoites in stool specimens or in tissue collected during endoscopy.  Cysts are less frequently encountered.  Balantidium coli is passed intermittently and once outside the colon is rapidly destroyed.  Thus stool specimens should be collected repeatedly, and immediately examined or preserved to enhance detection of the parasite.

Diagnostic findings

• Microscopy
• Morphologic comparison with other intestinal parasites

Treatment:
The drug of choice is tetracycline*, with metronidazole* and  iodoquinol* as alternatives.  Tetracycline is contraindicated in pregnancy and in children less than 8 years old.  For additional information, see the recommendations in The Medical Letter (Drugs for Parasitic Infections).

* This drug is approved by the FDA, but considered investigational for this purpose.