Case #496 – July, 2019

A 29-year-old female working at a zoo as a primate intern developed gastrointestinal symptoms including diarrhea and cramping. She sought medical attention from her health care provider which included a stool examination for ova and parasites (O & P). Figures A–C show what was observed in a wet-mount preparation from a formalin-ethyl acetate concentration procedure. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

This was a case of balantidiasis caused by the ciliated protozoan, Balantidium coli. Swine are the primary hosts; humans, nonhuman primates, and rodents can also serve as reservoir hosts.

Diagnostic morphologic features shown in the images were:

large trophozoites with cilia within the size range for B. coli (40-200 micrometers)
presence of a cytostome (located at the tapered end)

More on balantidiasis: https://www.cdc.gov/dpdx/balantidiasis/index.html

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.