Case #166 – October, 2005

A 13-year-old boy was seen by his pediatrician for watery diarrhea, abdominal cramping, and low-grade fever that had persisted for 3 days. His symptoms began approximately 5 days after returning from a summer camp trip to a petting zoo. The physician ordered an ova and parasites (O & P) exam. The lab personnel followed their typical O & P procedure by performing an FEA concentration from formalin preserved stool and making wet mounts, and using PVA preserved stool to make trichrome stained smears. Figures A and B show objects seen in low numbers on a wet mount (A) and the trichrome stained smear (B). The round objects measured an average of 5 micrometers in diameter. The laboratory reported a presumed diagnosis of parasitic protozoa. What organism do you suspect? Based on what criteria? What, if anything, else needs to be done?

Figure A

Figure B

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.

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