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Case #509 - February, 2020

A 3-year-old boy was seen by a pediatrician for gastrointestinal pain and watery diarrhea. His parents conveyed that he has a propensity for putting insects in his mouth and sometimes eating them. A stool specimen was collected and processed for ova and parasites (O&P). A formalin-ethyl acetate (FEA) concentration was performed and a wet mount smear was prepared from the sediment and examined. Figures A and B show one parasite-like object at different focal planes at 200x magnification; another object from the sample is shown in Figures C and D, also at different focal planes, at 200x magnification. What is your diagnosis? Based on what criteria?

Figure A

Figure A

Figure B

Figure B

Figure C

Figure C

Figure A

Figure D

This was a case of acanthocephaliasis based on the presence of eggs of both Macracanthorynchus sp, and Moniliformis moniliformis. Although acanthocephalan eggs are not always produced in human infections, they are identifiable by several features. Morphologic features shown in the Figures included:

  • Eggs with a thick, dark brown textured shell (Figures A and B) and size consistent with Macracanthorynchus sp. (80—100 x 50 µm).
  • Eggs with a textured, thick, clear shell (Figures C and D) and size consistent with Moniliformis moniliformis (90—125 x 65 µm).

More on acanthocephaliasis

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

Page last reviewed: March 25, 2020