What is Dientamoeba fragilis and how is it transmitted?

Updated: Jul 31, 2018
  • Author: Maria A Garcia Fernandez, MD; Chief Editor: Russell W Steele, MD  more...
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Dientamoeba fragilis is a nonflagellate trichomonad parasite 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. Organisms move most actively in fresh feces but quickly round up when left standing, are sensitive to an aerobic environment, and die and dissociate when placed in saline, tap water, or distilled water. D fragilis has been detected in untreated sewage. [1]

The mode of transmission is not well understood, and conflicting evidence has been published. [2]  Surveys of various mammals and birds have only identified nonhuman primates as natural hosts and never in domestic pets; however, recently a high prevalence of infection has been reported in pigs. [3]  Thus, there is a possible zoonotic transmission of this parasite, although most infections are believed to be through direct fecal-oral spread and, possibly, through co-infection of eggs of Enterobius vermicularis (ie, pinworm).

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