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Case #456 - November, 2017

A four-year-old child from Ethiopia had a stool examination as part of a standard refugee screening. A fecal specimen was collected in zinc polyvinyl alcohol (Zn-PVA) fixative and in 10% formalin. A formalin-ethyl acetate (FEA) concentration was performed on the formalin-fixed specimen and a wet mount smear examined for helminths where no ova or larvae were observed but a suspected protozoa was detected. A smear was prepared from the PVA specimen, stained with trichrome stain, and examined. Figures A D show what was observed in moderate numbers on the trichrome stained smear. The objects measured 8-11 micrometers on average. What is your diagnosis? Based on what criteria?

parasitic image

Figure A

parasitic image

Figure B

parasitic image

Figure C

parasitic image

Figure D

Case Answer

This was a case of Dientamoeba fragilis infection. Diagnostic morphologic features shown included:

  • trophozoites with one or two nuclei with fragmented karyosomal chromatin and no discernable peripheral pigment.
  • trophozoites within the size range for D. fragilis ((5-15 micrometers).

More on Dientamoeba fragilis:

Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.

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  • Page last reviewed: January 18, 2018
  • Page last updated: January 18, 2018
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