Search
Dientamoeba fragilis
An ameboid pathogen that infects the colon.
Epidemiology:
1) occurs especially in young children
2) human to human fecal-oral spread
3) may spread by ingestion of D. fragilis-infected Enterobius vermicularis (pinworm) eggs
Pathology:
1) no cyst stage has been described
2) generally not associated with other intestinal protozoa
3) trophozoites infect mucosal crypt cells of intestines
- eosinophilic inflammatory response
4) infection with D. fragilis is associated with a 10-20 fold increased incidence of enterobiasis
Clinical manifestations:
1) 25% of infected individuals have symptoms
2) nonbloody diarrhea & abdominal distension
3) nausea/vomiting
4) anorexia, weight loss, flatulence
5) headache, fever, malaise,fatigue
Laboratory:
1) diagnosis is made by recovery of trophozoites in feces
- trichrome stain [3]
2) multiple specimens may need to be examined because of intermittent shedding
3) trophozoites
a) found in greatest numbers in the last portion of the stool
b) measure 5-15 um in size, generally 9-12 um
c) motile on wet mounts with angular pseudopods
d) 65-90% of contain 2 nuclei
e) trophozoites with a single nucleus may be confused with trophozoites Endolimax nana or Iodamoeba butschii
f) cytoplasm is finely granular & often contains ingested bacteria
g) delicate & may be easily overlooked on stained slides
4) immunofluorescence method described, but not yet commercially available
5) Dientamoeba fragilis DNA in stool
* image [3]
Management:
1) iodoquinol 650 mg PO TID for 20 days
2) paromomycin 25-30 mg/kg/day divided TID for 7 days
3) tetracycline 500 mg QID for 10 days
Related
Enterobius vermicularis (pinworm)
General
Dientamoeba
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 1273, 1274-77
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1204-05
- Grimm L
What's Eating You: 12 Common Intestinal Parasites.
Medscape. November 25, 2019
https://reference.medscape.com/slideshow/intestinal-parasites-6010996