Dientamoeba fragilis is a nonflagellate trichomonad parasite and is one of the smaller parasites that can live in the human large intestine. Unlike most other intestinal protozoa, its life cycle has no cyst stage; thus, infection between humans occurs during the trophozoite stage. The most common symptoms are diarrhea, stomach pain, and stomach cramping.
A total of 6,750 patients submitted fecal specimens between March 2002 and July 2004 in which trophozoites of Dientamoeba fragilis were detected in 60 patients by permanent staining. The average age of infected patients was 39.8 years. Of the 60 patients infected with D. fragilis, six had a history of recent overseas travel.
The therapy is eradication of the parasite Dientamoeba fragilis. The drugs used are considered investigational by the US Food and Drug Administration because of a lack of clinical trials. Response rates for a single course of therapy are 70-90% in the limited data published, with higher rates of treatment failures reported following the use of metronidazole as compared with other antimicrobials.