Dientamoeba fragilis infection is a medical condition caused by infection with Dientamoeba fragilis, a single-cell parasite that infects the lower gastrointestinal tract of humans. Many people infected with dientamoeba fragilis do not have any symptoms. The most common symptoms are diarrhea, stomach pain, and stomach cramping. Loss of appetite and weight, nausea, and fatigue also are common. The infection does not spread from the intestines to other parts of the body. D fragilis infests the large intestine and, while its presence can be observed in the intestinal crypts on biopsy, it does not actively invade the gastrointestinal tract.
D fragilis is believed to be transmitted between human hosts inside helminth eggs or larvae, particularly those of Enterobius vermicularis. When this parasite is detected, a search for co-infection with E vermicularis should also be completed, in view of the frequent association between the two parasites. Diagnosis is by microscopic examination of fresh stool or stool that has been preserved specifically for parasitic examination. The organism can be difficult to detect and three or more samples may be necessary in order to establish the diagnosis of infection.
Estimated prevalence in the general population 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.
In Mexico, Sanchez-Aguillon and colleagues have documented a very nice study on parasitic infections in a Mexican HIV/AIDS cohort. Quite a few of the patients had Cryptosporidium, Cyclospora or Cystoisospora, the presence of which was not surprisingly associated with diarrhoea. Blastocystis was found in about 30%; of note, only ST1 and ST3 were found, adding further support to the hypothesis that ST1 and ST3 are common in most parts of the world, while especially ST4 exhibits vast differences in geographic 'affinity'.
According to Enrique Chacon-Cruz, MD Chief, Pediatric Infectious Diseases Department, Head Professor of Pediatrics, General Hospital, Tijuana, Mexico, Prevalence of intestinal protozoal disease is not associated with racial background. One study performed in Mexico demonstrated an increased frequency of HLA-DR3 and complotype SCO1 in mestizo children with amebic liver abscess.
Iodoquinol is the drug of choice to treat Dientamoeba fragilis infection. Other alternate therapies include treatment with appropriate doses of Tetracycline, Doxycycline, Paromomycin, Metronidazole. Tetracycline and doxycycline should not be administered to children under age eight years. Paromomycin, an aminoglycoside, is not well absorbed from the gastrointestinal tract. Its use can result in overgrowth of resistant bacteria and has been associated with nausea, abdominal cramping and bloating, vertigo, headaches and rashes. While metronidazole may relieve symptoms, it does not necessarily eliminate the parasite.