Photomicrographs of the small intestine from a Western gull (Larus occidentalis) from California, USA

Photomicrographs of the small intestine from a Western gull (Larus occidentalis) from California, USA. H & E stain. (A) Expanding the small intestinal lumen and distorting intestinal villi are multiple adult metazoan parasites (arrow); similar parasites are within cavitations in the intestinal wall or serosa (arrowhead). (B) Worms are unsegmented with a smooth tegument (arrow), a thick hypodermal layer with lacunar channels (arrowhead), and lemnisci with lemnisci compressor muscles at the periphery (asterisks). (C) The anterior portion of the parasite contains a proboscis lined with spines (arrows). (D) Parasites within the intestinal wall or serosa are occasionally surrounded multifocally by low numbers of multinucleated giant cells, epithelioid macrophages, and hypereosinophilic debris (arrows).