The degree of symptoms may vary from asymptomatic to severe,[2] and can include weight loss, vomiting, fever, and involvement of other digestive organs.
Additional symptoms reported have included:[3] As many individuals are asymptomatic carriers of D. fragilis, pathogenic and nonpathogenic variants are proposed to exist.
However, the exact manner in which it is transmitted is not yet known, as the organism is unable to survive outside its human host for more than a few hours after excretion, and no cyst stage has been found.
[6] The high rate (40%) of concomitant infection with other protozoa reported by at St. Vincent's Hospital, Sydney, Australia, supports the oral-fecal route of transmission.
DNA fragment analysis provides excellent sensitivity and specificity when compared to microscopy for the detection of D. fragilis and both methods should be employed in laboratories with PCR capability.
[citation needed] Rates of infection increase in conditions of crowding and poor sanitation, and are higher in military personnel and mental institutions.
An Australian study identified a large number of patients, considered to have irritable bowel syndrome, who were actually infected with Dientamoeba fragilis.
Their report, published in 1918, concluded the organism was not pathogenic because it consumed bacteria in culture, but did not appear to engulf red blood cells, as was seen in the best-known disease-causing amoeba of the time, Entamoeba histolytica.