Dientamoeba fragilis detection methods and prevalence: a survey of state public health laboratories

Dientamoeba fragilis is a pathogenic protozoan parasite that has no cyst stage. Because of the lack of a cyst stage, the laboratory detection of D. fragilis in stool specimens is dependent on the stool processing and examination methods employed. Failure to use recommended stool fixation and permanent staining techniques almost precludes identification of D. fragilis, which is associated with gastrointestinal illness in humans. In this survey, questionnaires were mailed to all State and territorial public health laboratories requesting information on the number of ova and parasite examinations, methods of processing and examining stools, and the number of D. fragilis positive stools for 1985. Forty-three of 54 (80 percent) laboratories responded. Results showed that those laboratories which reported D. fragilis detection examined more stools using recommended stool fixation methods and were more likely to stain permanently all stools examined. Permanent staining of all stools, as compared to loose and watery stools only, resulted in a fivefold greater detection of D. fragilis. More State and territorial public health laboratories reported finding D. fragilis infections in 1985 than in a 1978 survey performed by the Centers for Disease Control. However, in 1985 only six laboratories reported 82 percent of all D. fragilis detections. To increase the probability of detecting D. fragilis in stool specimens, the findings suggest that all stools should be submitted fixed in polyvinyl alcohol fixative, sodium acetate-acetic acid-formalin fixative, or Schaudinn's fixative. Further, all specimens, regardless of consistency, should be permanently stained prior to microscopic examination.