Case #226 – April, 2008

A 32-year-old Latin American man sought medical attention for persistent fever and cough. A sputum specimen was collected for testing. Smears were prepared and stained with Giemsa. The images in Figures A and B show forms that were observed in very low numbers on the smears. Figures A and B were captured at 200x and 1000x oil magnification, respectively. The object measured approximately 490 micrometers in length. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of strongyloidiasis caused by Strongyloides stercoralis. The larva shown in the images was a filariform (infective third-stage form) larva. Diagnostic features included:

the length of the larva being within the size range for the species.
the esophagus to intestine ratio, which was roughly 1:1 (Figure A).
the characteristic notched tail of filariform larvae of S. stercoralis (Figure B).

Figure A