Despite its name,
Dientamoeba fragilis is not an ameba but a flagellate. This
protozoan parasite produces trophozoites; cysts have not been
identified. Infection may be either symptomatic or asymptomatic.
The complete life
cycle of this parasite has not yet been determined, but assumptions were
made based on clinical data. To date, the cyst stage has not been
identified in D. fragilis life cycle, and the trophozoite is the
only stage found in stools of infected individuals
D. fragilis is probably transmitted by fecal-oral route
transmission via helminth eggs (e.g., Ascaris, Enterobius
spp.) has been postulated
Trophozoites of D. fragilis have characteristically one or two
and it is found in children complaining of intestinal (e.g.,
intermittent diarrhea, abdominal pain) and other symptoms (e.g., nausea,
anorexia, fatigue, malaise, poor weight gain).
Symptoms that have
been associated with infection include diarrhea, abdominal pain,
anorexia, nausea, vomiting, fatigue, and weight loss.
diagnosed through detection of trophozoites in permanently stained fecal
smears (e.g., trichrome). This parasite is not detectable by stool
concentration methods. Dientamoeba fragilis trophozoites can be
easily overlooked because they are pale-staining and their nuclei may
resemble those of Endolimax nana or Entamoeba hartmanni.
comparison with other intestinal parasites
Safe and effective
drugs are available. The drug of choice is iodoquinol. Paromomycin*,
tetracycline*, (contraindicated in children under age 8, pregnant and
lactating women) or metronidazole can also be used.
* This drug is
approved by the FDA, but considered investigational for this purpose.