balantidiasis

Balantidiasis is an intestinal infection caused by Balantidium coli, a large ciliated protozoan parasite that can infect humans and pigs. Most infections are asymptomatic, but disease may occur when the parasite invades the large intestine.

The principal reservoir is pigs; humans acquire infection via ingestion of cysts in contaminated water or food. Risk factors include poor sanitation, rural or farming settings, and close contact with pigs. Immunocompromised individuals may experience more severe illness.

Balantidium coli has a two-stage life cycle. Ingested cysts release trophozoites in the colon, which multiply and can ulcerate mucosa. Cysts are shed in stool and may survive in the environment, enabling transmission.

Clinical features range from mild diarrhea to dysentery with abdominal pain, tenesmus, and mucus- or blood-streaked stools. Severe colitis can cause dehydration, perforation, or peritonitis, especially in malnourished or immunocompromised patients.

Diagnosis is by stool examination showing large ciliated trophozoites and cysts. Microscopy reveals a macronucleus and micronucleus, characteristic of Balantidium coli.

Treatment includes metronidazole (for example, 750 mg three times daily for 7–10 days) or tetracycline (500 mg four times daily for 10 days). Alternatives include iodoquinol or paromomycin; therapy choice depends on severity and pregnancy status. Supportive care for dehydration may be needed.

Prevention focuses on safe water and food, good hand hygiene, and proper sanitation, along with limiting pig contact or housing pigs away from living areas.