Case #342 – March, 2013
A 24-year-old man sought medical attention from his health care provider for intermittent abdominal cramping and mild diarrhea. A stool specimen was collected in 10% formalin for laboratory testing. A formalin-ethyl acetate concentration was performed and a wet mount of the sediment was examined for ova and parasites (O&P). The objects shown in Figures A–D were observed in moderate numbers and measured 44-48 micrometers long on average. What is your diagnosis? Based on what criteria?
This was a case of hymenolepiasis caused by Hymenolepis nana (the dwarf tapeworm). Morphologic features shown included:
- oval eggs within the size range for H. nana (30-50 micrometers).
- presence of an oncosphere with hooklets (best seen in Figures A, C, and D).
- polar filaments between the inner and outer membranes.
More on: Hymenolepiasis
This case and images were kindly provided by the Washington State Public Health Laboratory.
Images presented in the DPDx 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/.