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Balantidium coli
Largest protozoan to infect humans.
Epidemiology:
1) acquired by ingestion of infective cysts via contaminated food or water
2) organisms migrate to the colon where the develop into trophozoites
3) trophozoites comsume bacteria & replicate by binary fission & conjugation
4) human infection is rare in USA & generally acquired from hogs
5) hogs are commonly infected
Pathology:
- trophozoites reside primarily in lumen of colon, but may penetrate the intestinal mucosa & cause ulcers, colitis
Clinical manifestations:
- most cases asymptomatic
- bloody diarrhea &/or mucoid diarrhea
- nausea/vomiting, dehydration
- abdominal pain
- anorexia, weight loss
- fever
Laboratory:
1) diagnosis is made by recovery of trophozoites or cysts in feces (wet mount)
2) trophozoites
a) measure 40-200 um (generally 50-100 um)
b) uniformly covered with cilia
c) large macronucleus (easily seen with stains) & smaller micronucleus (generally not visualized)
d) numerous vacuoles in cytoplasm
3) cysts
a) rounded, measuring 50-70 um
b) cilia may be seen with younger cysts
c) nuclei similar to trophozoites
4) stool specimens contaminated with stagnant water may contain free-living ciliates distinguishable from B coli by differences in ciliary patterns
* image [3]
Management:
- electrolyte replacement
- tetracycline 500 mg PO QID is effective
- metronidazole or iodoquinol are alternatives [3]
Related
trophozoite
General
Balantidium
Properties
KINGDOM: animal
PHYLUM: protozoa
References
- Clinical Diagnosis & Management by Laboratory Methods,
19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia,
PA. 1996, pg 1278
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1204
- Grimm L
What's Eating You: 12 Common Intestinal Parasites.
Medscape. November 25, 2019
https://reference.medscape.com/slideshow/intestinal-parasites-6010996