Microscopy

A	B

A: Eggs of Angiostrongylus costaricensis.
B: Larva of A. costaricensis.

In humans, eggs and larvae are not normally excreted, but remain sequestered in tissues.  Both eggs and larvae (occasionally adult worms) of A. costaricensis can be identified in biopsy or surgical specimens of intestinal tissue.  The larvae need to be distinguished from larvae of Strongyloides stercoralis; however, the presence of granulomas containing thin shelled eggs and/or larvae serve to distinguish A. costaricensis infections.