Dientamoeba fragilis is a species of single-celled excavates found in the gastrointestinal tract of some humans, pigs and gorillas.

Dientamoeba fragilis cells are able to survive and move in fresh feces but are sensitive to aerobic environments.

[5] Infection with D. fragilis, called dientamoebiasis, is associated variously with symptoms of abdominal pain, diarrhea, weight loss, nausea, fatigue and fever.

[5] D. fragilis does not penetrate the host tissue directly; therefore, some of these symptoms may be caused from irritation which then leads to colonic motility.

[5] Iodoquinol is the primary drug treatment for dientamoebiasis, unfortunately there are side effects such as abdominal cramping, nausea, and rash.

Unlike majority of parasitic infections, D. fragilis is more prevalent in well-developed countries as opposed to disadvantaged and resource poor nations.

[9] The parasite is also endemic in crowded communities (i.e institutions), populations with unsatisfactory sanitation conditions, and individuals who travel to underprivileged countries.

[3] Globally, the prevalence of D. fragilis ranges from 0.3% to 90%, occurring in multiple countries including many urbanized cities such as Los Angeles, California and Sydney, Australia.

Prior to the report of this cyst stage in the lifecycle of Dientamoeba, transmission was postulated to occur by helminth eggs (e.g., Ascaris, Enterobius spp.).

The rationale for this suggestion was that D. fragilis is closely related to the turkey parasite Histomonas, which is known to be transmitted by the eggs of the helminth Heterakis.