Microscopy

Humans serve only as paratenic hosts for Gnathostoma spp. Identification of gnathostomiasis is achieved by serology or microscopic observation of the larval worms in tissue sections. Diagnostic characters for Gnathostoma include the presence of large lateral chords, multinucleate intestinal cells (some species), presence of pigmented granular material in the intestinal cells, and the presence of spines on the cuticle, especially near the anterior end of the worm.

A	B

A: Hematoxylin and eosin (H&E) stained cross-section of Gnathostoma sp., taken from a subcutaneous nodule above the right breast of a patient, showing the esophagus. Note the presence of cuticular spines (arrow). Image courtesy of Diagnostix Pathology Laboratories LTD, Canossa Hospital, Hong Kong, China.
B: Another H&E-stained cross-section of Gnathostoma sp., taken of the same specimen in Figure A, showing the intestinal cells and characteristic large lateral chords (LC). Note the multinucleate intestinal cells and the presence of pigmented granular material in the intestinal cells.