Case #419 - May 2016
A 23-year-old female presented to her primary care provider with abdominal pain, cramps, flatulence, and diarrhea five days after returning from a white water rafting trip in the Grand Canyon, Arizona. Stool specimens were collected in 10% formalin and zinc polyvinyl alcohol (Zn-PVA) and sent to a reference lab for routine ova-and-parasite (O&P) testing. Figures A-D show what was observed on a trichrome-stain slide of stool preserved in the Zn-PVA. Images were captured at 1000x magnification with oil. What is your diagnosis? Based on what criteria?
This case demonstrated a mixed infection of Giardia duodenalis and Blastocystis hominis. Diagnostic morphologic features included:
- ellipsoidal cysts of within the size-range (8-19 μm) for G. duodenalis (Figures A, C, D) that contained multiple nuclei, fibrils, and axonemes.
- pyriform trophozoite within the size range (10-20 μm) for G. duodenalis (Figure B) that contained fibrils,median bodies, two nuclei, and sucking disks.
- cyst-like forms of B. hominis (Figures A-D) containing a large central body surrounded by a narrow rim of cytoplasm containing nuclei and inclusion bodies.
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/.