How to Cite This Chapter: Stefaniak J, Kłudkowska M. Balantidiasis. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed July 20, 2024.
Last Updated: December 20, 2021
Last Reviewed: December 20, 2021
Chapter Information


1. Etiologic agent: Balantidium coli, the largest protozoan and the only ciliate parasite invading humans. The parasite has a trophozoite stage and a cyst stage. The infective forms for humans are cysts.

2. Pathogenesis: Trophozoites produce strong proteolytic enzymes, which they use to digest the colonic mucosa. This facilitates the parasite’s penetration through the intestinal wall and leads to the formation of numerous disseminated ulcers and necrotic foci.

3. Reservoir and transmission: The primary reservoir of B coli is pigs. Transmission occurs via the fecal-oral route, typically through ingestion of water or foods contaminated with human or porcine feces.


B coli is a cosmopolitan parasite, but invasions are most common in the tropical and subtropical zones. The areas endemic for balantidiasis are countries of Latin America and Middle East, Papua New Guinea, and the Philippines.


B coli infection may be asymptomatic (carriers).

Types of symptomatic disease:

1) Mild balantidiasis: The most common type; manifests with diarrhea (without blood in stool) alternating with constipation.

2) Acute balantidiasis: Dysentery with mucus, painful urge to defecate, abdominal pain, nausea, vomiting, headache; the course may be fulminant.

3) Chronic balantidiasis: Untreated mild disease may progress to chronic disease, with loss of appetite, periods of diarrhea, headache, iron deficiency anemia, and weight loss.

4) Extraintestinal balantidiasis: Very rare; manifests with appendicitis, genitourinary tract infections, or pneumonia.


Diagnostic Tests

Identification of the etiologic agent: Microscopic identification of B coli cysts, trophozoites, or both, in direct stool examination. Perform repeat stool samplings several days apart, as the parasite is excreted with shifted temporal patterns and in varying amounts. Rectoscopy or colonoscopy with colorectal swab or collection of a specimen from the colorectal mucosa may be indicated for parasitologic testing.

Differential Diagnosis

Amebiasis and other gastrointestinal parasitic diseases, infectious diarrhea, ulcerative colitis.


Antiprotozoal Treatment

1. First-line treatment: Oral tetracycline 500 mg qid for 10 days or oral metronidazole 750 mg tid for 5 days.

2. Alternative treatment: Oral iodoquinol 650 mg tid for 20 days or nitazoxanide, ampicillin, or paromomycin.

Symptomatic Treatment

As in infectious diarrhea.


Possible complications in the very rare cases of fulminant infection include perforation of the large intestine, peritonitis, and hemorrhage.


In general the prognosis is good. Sporadically the infection may be fulminant, which may lead to death.


Specific Prevention


Nonspecific Prevention

1. Avoiding consumption of contaminated water or food (particularly in tropical areas).

2. Maintaining high standards of personal and work hygiene by pig breeders.

We use cookies to ensure you get the best browsing experience on our website. Refer to our Cookies Information and Privacy Policy for more details.