Case #504 – November, 2019
A 35-year-old female tourist who visited Vietnam presented with symptoms of headache, cough, fatigue and weight loss about ten weeks after returning from her trip. A stool specimen was collected in 10% formalin, concentrated by ethyl acetate method (FEA), and viewed under light microscopy for routine ova and parasite (O&P) examination. Figures A–C show what was observed in a wet mount of the FEA concentrate. The objects of interest measured 88-92 micrometers long by 47-48 micrometers wide.
What is your diagnosis? Based on what criteria?
This was a case of paragonimiasis caused by a lung fluke in the genus Paragonimus. Diagnostic morphologic features included:
- unembryonated eggs within the size range for Paragonimus spp
- presence of an operculum (seen in all the Figures). The egg in Figure B shows the popped operculum. It is the same egg as in Figure A after slightly tapping the wet mount coverslip.
- visible opercular ‘shoulders’ (Figure C, red arrow).
- golden-brown eggs with a thick shell and a thickened abopercular end (Figure C, blue arrow).
Paragonimus westermani is the most common of more than ten species of lung flukes in the genus Paragonimus reported to infect humans, which is widely distributed across Southeast Asia. The eggs are morphologically similar, but sizes vary and may overlap across species, thereby, egg size is a somewhat unreliable characteristic to distinguish species. Diagnosis is usually made by identifying eggs excreted in sputum, but occasionally eggs may be swallowed and passed in stool.
For more information on paragonimiasis, please visit: https://www.cdc.gov/dpdx/paragonimiasis/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.
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/.