Dientamoeba fragilis (Pathogen)
This organism belongs to the flagellates, is a true pathogen, and causes symptoms. There is both a trophozoite stage (usual size, 9-12 µm) and a cyst stage (usual size somewhat smaller than the trophozoite).
|Trophozoites with single nucleus
Beginning to fragment (left), fragmented (right)
Trophozoites with two fragmented nuclei
Intestine, organisms passed in feces; trophozoites thought to be transmitted inside of helminth eggs (Ascaris lumbricoides, Enterobius vermicularis).
Fecal-oral transmission via trophozoite form; contaminated food and water
Worldwide, primarily human-to-human transmission
Intestinal: Intermittent diarrhea, abdominal pain, nausea, anorexia, malaise, fatigue, poor weight gain, unexplained eosinophilia. The most common symptoms in patients infected with this parasite appear to be intermittent diarrhea and fatigue. In some patients, both the organism and the symptoms persist or reappear until appropriate treatment is initiated. Clinicians should include infection with D. fragilis in their differential diagnosis in patients presenting with abdominal pain, diarrhea, unexplained flatulence, nausea, and vomiting.
Intestinal: Ova and Parasite examination (concentration, permanent stained smear); permanent stained smear mandatory for identification. It is particularly important that permanently stained smears of stool material be examined with an oil immersion objective (100´). These organisms have been recovered in formed stool; therefore a permanent stained smear must be prepared for every stool sample submitted for a parasite examination.
Trophozoite: Round, 1 (20-40%) nucleus or 2 nuclei (60-80%); nuclei tend to fragment into 3-5 granules. Cytoplasm often filled with ingested debris; size range of trophozoites is tremendous, even on a single slide.
Dientamoeba fragilis (indicate trophozoites)
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
This organism can mimic other protozoa such as Endolimax nana. In many parts of the United States, this organism is found more often than Giardia. Although often seen in pediatric patients, the infection is not limited to this population; all age groups can become infected.