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Dientamoeba fragilis Infection

[Dientamoeba fragilis]

 Binucleate forms of trophozoites of D. fragilis, stained with trichrome.

Binucleate form of a trophozoite of Dientamoeba fragilis, stained with trichrome.

Uninucleate forms of trophozoites of D. fragilis, stained with trichrome.

Uninucleate form of a trophozoite of D. fragilis, stained with trichrome.

Causal Agents

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.

Life Cycle

Life cycle of Dientamoeba

The complete life cycle of Dientamoeba fragilis has not yet been determined, and assumptions were made based on clinical data. Historically, this species was known only from the trophozoite stage in stools of infected individualsThe Number 1. In 2014, cyst and precyst stages were described for the first time in clinical human specimens. These data are still considered preliminary and further testing should be done to validate the existence of this stage in the human host.
D. fragilis is probably transmitted by fecal-oral routeThe Number 2 and transmission via helminth eggs (e.g., Ascaris, Enterobius spp.) has been postulatedThe Number 3. Trophozoites of D. fragilis have characteristically one or two nuclei (The Number 1, The Number 4), 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).

Reference: Stark D, Garcia LS, Barratt JLN, Phillips O, Roberts T, Marriot D, Harkness J, Ellis JT. Description of Dientamoeba fragilis cyst and precystic forms from human samples. Journ Clin Micro. 2014; 52: 2680-2683.

Geographic Distribution


Clinical Presentation

Symptoms that have been associated with infection include diarrhea, abdominal pain, anorexia, nausea, vomiting, fatigue, and weight loss.

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  • Page last reviewed March 18, 2015
  • Page last updated March 18, 2015
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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