Parasitology Training Manual

Dientamoeba fragilis

• Abbreviation: Df
• Size of trophozoite: 5 - 15 microns
• Considered a non-invasive pathogen, occupying the mucosal crypts of the large intestine.
• It has been suggested that 91% of children between six months and 19 years have antibodies against D. fragilis. Very few of these cases are symptomatic and if they are the symptoms range from minor abdominal pain, fatigue and bloating to diarrhea.(23)
• Some investigators suggest that D. fragilis be considered pathogenic in those people including adults and children where symptoms occur.(24)
• This parasite is considered a flagellate with no cyst form. Its life cycle is not established, but the ova of Enterobius vermicularis has been implicated by many.(25)
• Identification requires the examination of fecal stained smears, although, an experienced investigator may recognize this organism in a wet mount without the permanent stain, in most cases it will be missed entirely.
• The trophozoites typically contain 2 nuclei however a great percentage may contain only one. The cytoplasm is relatively clear but may contain a vacuole in immature cells.
• The rosette shaped nuclei contain 3 - 5 granules and at times may resemble that of E. nana or even E. hartmanni.
• Typically the cell may stretch so much that it appears thread like between two cell masses.

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David M. Raymondo
MLT, CLS(m)
Professional Affiliation: Gamma-Dynacare Medical Laboratories, Ottawa, Ontario, Canada
Gamma-Dynacare is a Division of the Dynacare Health Group