Life cycle of Dientamoeba fragilis (including some speculation)
The complete life cycle of Dientamoeba fragilis has not yet been determined, so this diagram includes some assumptions based on clinical data. To date, no cyst stage has been identified in the life cycle of D. fragilis and the trophozoite stage is the only stage found in stool of infected individuals (1). Dientamoeba fragilis is probably transmitted by the fecal-oral route (2) and transmission via helminth eggs (e.g., Ascaris, Enterobius) has been postulated (3). Trophozoites of D. fragilis characteristically have one or two nuclei (1,4). These parasites are found in children complaining of intestinal (e.g., intermittent diarrhea, abdominal pain) and other symptoms (e.g., nausea, anorexia, fatigue, malaise, and poor weight gain).
From Centers for Disease Control Parasites and Health website.