Dientamoeba Fragilis Infection

Author: David R Mack, MD, FRCPC; Chief Editor: Russell W Steele, MD more...

Updated: May 28, 2010

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Background
Pathophysiology
Epidemiology
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Background

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. 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. The mode of transmission is believed to be through direct fecal-oral spread and, possibly, through coinfection of eggs of Enterobius vermicularis (ie, pinworm).

Pathophysiology

Organisms infect mucosal crypts of the large intestine that are located close to the mucosal epithelium, from the cecum to the rectum; however, the cecum and proximal colon are usually affected. This parasite is not known to be invasive and does not cause cellular damage. It may invoke an eosinophilic inflammatory response in the colonic mucosa; thus, symptoms are related to the superficial colonic mucosal irritation. Similar to some other parasites (eg, Cyclospora cayetanensis, Giardia lamblia, Cryptosporidium parvum), the parasite D fragilis has been demonstrated to cause disease in humans regardless of their immune status.

The life cycle of D fragilis is shown in the image below.

This is an illustration of the assumed life cycle of Dientamoeba fragilis, the cause of a protozoan parasitic infection.

Frequency

International

Estimated prevalence in the general population in the United States and in other developed countries is most commonly 2-4%. However, much higher prevalence rates (19-69%) have been reported in specific populations, such as individuals living in crowded conditions (eg, institutions, communal living), individuals living in conditions with poor hygiene, and those traveling to developing countries.

Mortality/Morbidity

Colonization may occur without development of disease. In adults, asymptomatic colonization is present in 75-85% of individuals affected by the parasite. In children, the opposite is true; disease develops in as many as 90% of those colonized.

No specific mortality is associated with this enteropathogen. Morbidity related to acute infection occurs in the first 1-2 weeks of the disease, with symptomatology predominated by diarrhea. Chronic infection occurs after 1-2 months of illness and is manifested by abdominal pain.

Age

Infection may occur at any age. The most common age at which infection has been reported in children is 5-10 years. Interestingly, E vermicularis (pinworm) infection can also occur in the same age group.

Proceed to Clinical Presentation

Contributor Information and Disclosures

Author

David R Mack, MD, FRCPC Professor, Departments of Pediatrics and Biochemistry, Microbiology, and Immunology, University of Ottawa Faculty of Medicine; Head, Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Children's Hospital of Eastern Ontario, Canada

David R Mack, MD, FRCPC is a member of the following medical societies: American Gastroenterological Association, Canadian Association of Gastroenterology, and North American Society for Pediatric Gastroenterology and Nutrition

Disclosure: Axcan Honorarium to CHEO Foundation Review panel membership; Novartis Honorarium to CHEO Foundation Consulting; AstraZeneca Honorarium to CHEO Foundation Speaking and teaching; Merck Frosst Honorarium to CHEO Foundation Speaking and teaching; Schering Plough Honorarium to CHEO Foundation Review panel membership; Schering Plough Honorarium to CHEO Foundation Speaking and teaching; Abbott Speaking and teaching; Ross Nutritionals Honorarium to CHEO Foundation Review panel membership; Nestle Honorarium to CHEO Foundation Review panel membership; Nestle Honorarium to CHEO Foundation Speaking and teaching

Specialty Editor Board

Michael D Nissen, MBBS, FRACP, FRCPA Associate Professor in Biomolecular, Biomedical Science & Health, Griffith University; Director of Infectious Diesases and Unit Head of Queensland Paediatric Infectious Laboratory, Sir Albert Sakzewski Viral Research Centre, Royal Children's Hospital

Michael D Nissen, MBBS, FRACP, FRCPA is a member of the following medical societies: American Academy of Pediatrics, American Society for Microbiology, Pediatric Infectious Diseases Society, Royal Australasian College of Physicians, and Royal College of Pathologists of Australasia

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine

Disclosure: Nothing to disclose.

Martin Weisse, MD Program Director, Associate Professor, Department of Pediatrics, West Virginia University

Martin Weisse, MD is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Robert W Tolan Jr, MD Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine

Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility

Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine

Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association

Disclosure: None None None

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