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Dientamoeba Fragilis Infection

  • Author: David R Mack, MD, FRCPC; Chief Editor: Russell W Steele, MD  more...
 
Updated: Aug 18, 2015
 

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

Frequency

International

Estimated prevalence in the general population in the United States and in other developed countries is most commonly 2-5%. 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, and, in adults, asymptomatic colonization was once thought to be present in 75-85% of individuals infected by the parasite. More recently, it is not believed that asymptomatic carriage is as prevalent as once thought and in children symptomatic disease develops in as many as 90% of those colonized. In 2014, new research was presented at the 24th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) that questioned the pathogenicity of the parasite.[4]

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 and abdominal pain. 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.

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Contributor Information and Disclosures
Author

David R Mack, MD, FRCPC Professor, Department of Pediatrics, 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: Canadian Paediatric Society, Canadian Association of Gastroenterology, American Gastroenterological Association, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

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: Academic Pediatric Association, American Academy of Pediatrics, Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Chief Editor

Russell W Steele, MD Clinical Professor, Tulane University School of Medicine; Staff Physician, Ochsner Clinic Foundation

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, Southern Medical Association

Disclosure: Nothing to disclose.

Additional Contributors

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

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

Disclosure: Nothing to disclose.

References
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  2. Clark CG, Röser D, Stensvold CR. Transmission of Dientamoeba fragilis: pinworm or cysts?. Trends Parasitol. 2014 Mar. 30(3):136-40. [Medline].

  3. Cacciò SM, Sannella AR, Manuali E, Tosini F, Sensi M, Crotti D, et al. Pigs as natural hosts of Dientamoeba fragilis genotypes found in humans. Emerg Infect Dis. 2012 May. 18(5):838-41. [Medline]. [Full Text].

  4. New Research Questions Pathogenicity of Parasite D fragilis. Medscape. Available at http://www.medscape.com/viewarticle/825137. Accessed: 9/9/14.

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