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?
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: https://www.cdc.gov/dpdx/dientamoeba/index.html
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.
DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.