Causal Agent:
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:

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  and transmission via helminth eggs (e.g., Ascaris,Enterobius spp.) has been postulated . Trophozoites of D. fragilis have characteristically one or two nuclei (, ), 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).

What are the symptoms of infection with Dientamoeba fragilis?
Many infected people do not have any symptoms. The most common symptoms are diarrhea and abdominal pain. Symptoms also can include loss of appetite, weight loss, nausea, and fatigue. The infection does not spread from the intestine to other parts of the body.
What should I do if I think I might be infected?
See your health care provider.
How is infection with Dientamoeba fragilis diagnosed?
Your health care provider will ask you to provide stool specimens for testing. Because the parasite is not always found in every specimen, you might be asked to submit stool from more than one day. You might also be tested for pinwormeggs, which sometimes are found in people who are infected with D. fragilis.
Is medication available to treat infection withDientamoeba fragilis?
Yes. Safe and effective medications are available to treat D. fragilis infection.
How do people get infected with Dientamoeba fragilis?
This question is difficult to answer because we aren't sure how D. fragilis is spread. Most likely, people get infected by accidentally swallowing the parasite; this is called fecal-oral transmission. The parasite is fragile; it probably cannot live very long in the environment (after it is passed in feces) or in stomach acid (after it is swallowed). An unproven possibility is that pinworm eggs (or the eggs of another parasite) help protect and spread D. fragilis.
Who is at greatest risk for infection?
Anyone can become infected with this parasite. However, the risk for infection might be higher for people who live in or travel to settings with poor sanitary conditions.
How can I prevent Dientamoeba fragilis infection?
Wash your hands with soap and warm water after using the toilet, after changing diapers, and before preparing or eating food.
Teach children the importance of washing hands to prevent infection.