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Case #371 - May 2014

Stool specimens were collected from a 14-year-old refugee from Myanmar as part of a routine screening program. The stool was collected in 10% formalin and zinc PVA (Zn-PVA) and sent to the state health laboratory for ova-and-parasite (O&P) examination. Images of suspect parasites were captured and sent via email to the DPDx Team for diagnostic assistance. Figures A and B show two objects of interest that were observed by the attending microbiologist on a trichrome-stained slide prepared from Zn-PVA preserved stool. The measurements shown were included in the original telediagnosis submission. What is your diagnosis? Based on what criteria?

	Case371_A

Figure A

	Case371_B

Figure B

Case Answer

This case showed trophozoites of the nonpathogenic intestinal amoeba, Entamoeba hartmanni. Diagnostic morphologic features included:

  • trophozoites within the size range (5.0-15.0 μm, with an average range of 8.0-10.0 μm) of E. hartmanni.
  • nuclei with a discrete central karyosome and evenly-distributed peripheral chromatin.

While not considered pathogenic, E. hartmanni and other nonpathogenic amoebae should be reported in all O&P examinations, as their presence may be indicative of fecal contamination of a food or water source and does not preclude the presence of other intestinal pathogens.

More on: intestinal amebae

This case and images were kindly provided by the Kansas Health and Environment Laboratory, Topeka, KS.

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 education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.

  • Page last reviewed: August 24, 2016
  • Page last updated: August 24, 2016
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