Photomicrographs from a Trumpeter Swan (Cygnus buccinator) found dead in Indiana

Photomicrographs from a Trumpeter Swan (Cygnus buccinator) found dead in Indiana, U.S.A. (A) Within the small intestine is an area of transmural necrosis (arrow) with abundant luminal necrotic debris and hemorrhage containing few trematode eggs (arrowhead), and an adjacent trematode (*).  H&E stain.  (B) Detail of A. The ulcer contains abundant necrotic debris (arrow). An adult trematode is adjacent to the ulcer (arrowhead). H&E stain.  (C) Detail of B. The trematode has a smooth tegument (arrow) with prominent ventral acetabulum (*). H&E stain.  (D) Detail of A. Luminal trematode eggs exhibit a characteristic yellow refractile shell (arrows) H&E stain.