Dientamoeba fragilis: The unflagellated human flagellate

Jeffrey J. Windsor*, Eugene H. Johnson

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

51 Citations (Scopus)


Dientamoeba fragilis is a pathogenic protozoan parasite with a worldwide distribution. Although originally described as an amoeboid organism, it has been reclassified as a flagellate, on the basis of a number of electron microscopic and immunological findings. Except for its lack of a flagellum, D. fragilis closely resembles Histomonas and Trichomonas. Interestingly, a resistant cyst stage has not been demonstrated and it is unlikely that its trophozoites can survive successfully outside the human host. As a consequence of its higher than anticipated coincidence of infection with Enterobius vermicularis, transmission may occur via ova of this pinworm. D. fragilis infection may be acute or chronic, and has been reported in both children and adults. The most common clinical symptoms include abdominal pain, persistent diarrhoea, loss of appetite, weight loss and flatulence. Occasionally, eosinophilia, urticaria and pruritis have been described. Demonstration of the characteristic nuclear structure of D. fragilis, needed for a definitive diagnosis, cannot be achieved in unstained faecal material; therefore, permanently stained smears are essential. Treatment is recommended in symptomatic cases, and iodoquinol, tetracycline and metronidazole have been used successfully.

Original languageEnglish
Pages (from-to)293-306
Number of pages14
JournalBritish Journal of Biomedical Science
Issue number4
Publication statusPublished - 1999


  • Abdominal pain
  • Dientamoeba fragilis
  • Flagellate
  • Trophozoites

ASJC Scopus subject areas

  • Microbiology
  • Immunology and Allergy
  • Immunology
  • Clinical Biochemistry
  • Biochemistry, medical
  • Microbiology (medical)
  • Infectious Diseases


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