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Balantidium coli (Pathogen)

This organism belongs to the ciliates, is a true pathogen, and causes balantidiasis.  Both the trophozoite (usual size, 50-100 µm long and 40-70 µm wide) and cyst forms (usual size, 5-70 µm in diameter) can be found in clinical specimens.

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Trophozoite Cyst Trophozoites in tissue

Life Cycle:
Large bowel, trophozoites and cysts passed in stool AND/OR
Large bowel, tissue invasion (mucosal ulcers, abscess formation)

Fecal-oral transmission via cyst form; contaminated food and water

Worldwide, primarily human-to-human transmission, also pig-to-human transmission.  Particularly susceptible to infection are persons working as pig farmers or in slaughterhouses (28% infection in New Guinea). Human infection is fairly rare in temperate areas, although once the infection is established, it can develop into an epidemic, particularly where poor environmental sanitation and personal hygiene are found. This situation has been seen in mental hospitals in the United States.

Clinical Features:
Intestinal: Some individuals with B. coli infections are totally asymptomatic, whereas others have symptoms of severe dysentery similar to those seen in patients with amebiasis. Symptoms usually include diarrhea or dysentery, tenesmus, nausea, vomiting, anorexia, and headache. Insomnia, muscular weakness, and weight loss have also been reported. The diarrhea may persist for weeks to months prior to the development of dysentery. There may be tremendous fluid loss, with a type of diarrhea similar to that seen in cholera or in some coccidial or microsporidial infections.

ExtraintestinalB. coli have the potential to invade tissue. On contact with the mucosa, B. coli may penetrate the mucosa with cellular infiltration in the area of the developing ulcer. Some of the abscess formations may extend to the muscular layer. The ulcers may vary in shape, and the ulcer bed may be full of pus and necrotic debris. Although the number of cases is small, extraintestinal disease has been reported (peritonitis, urinary tract, inflammatory vaginitis).

Clinical Specimen:
Intestinal:  Stool, examination of mucosal ulcers (scrapings, biopsy)
Extraintestinal:  Fluids

Laboratory Diagnosis:
Intestinal:  Ova and Parasite examination (concentration, permanent stained smear); organisms are so large, they may be missed on permanent stain (resemble helminth eggs or debris); the concentration sediment is the most appropriate way to visualize the organisms.
Extraintestinal:  Trichrome, PAS stains, routine histology (H&E stain)

Organism Description:
Trophozoite:  Large, oval shaped; two nuclei (bean-shaped macronucleus easily visible, very small micronucleus often not seen); cilia easily seen around the periphery of the trophozoite.
Cyst:  Round, will contain the same 2 nuclei as seen in the trophozoite; cilia more difficult to see within the cyst wall.

Laboratory Report:
Balantidium coli (indicate trophozoites and/or cysts)

Garcia, L.S. 2007.  Diagnostic Medical Parasitology, 5th ed., ASM Press, Washington, D.C.

Improved hygiene, adequate disposal of fecal waste, adequate washing of contaminated fruits and vegetables; prevention of human-pig contact, hygienic rearing of pigs.

This organism is not that common within the United States, but is periodically sent as a proficiency testing specimen or image.  It is often associated with pigs, so could be seen in a human infection in these types of situations.