Case #521 - August, 2020
As part of a refugee screening program, a young child had a fecal ova and parasite (O & P) examination which included a formalin-ethyl acetate (FEA) fecal concentration. Objects shown in Figures A–C were detected in low numbers on a wet mount preparation and measured about 75 micrometers on average. What is your diagnosis? Based on what morphologic features?
This was a case of hymenolepiasis caused by Hymenolepis diminuta. Diagnostic morphologic features shown in the images included:
- eggs within the size range for H. diminuta.
- presence of an inner oncosphere without polar filaments in the space between the oncosphere and the outer shell/membrane (which would be present in the smaller eggs of H. nana).
- presence of hooks in the oncosphere (best seen in Figures B and C).
- an outer membrane/shell with striations.
More on hymenolepiasis
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 educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.