Digestive lesions in three species of cetaceans stranded in the Canary islands

Abstract

Since 1992, several cetacean strandings have ocurred on the shores of these islands, involving both single and multiple strandings of adults as well juvenile cetaceans. In the study of the causes of death in stranded cetaceans, a variety of gastrointestinal lesions were found. In this work, gastrointestinal lesions observed in 6 common dolphins (Delphinus delphis), 11 striped dolphins (Stenella coeruleoalba) and 6 spotted dolphins (Stenella frontalis) found stranded along the coasts of the Canary Islands were analyzed. Postmortem examinations were undertaken and tissue samples of forestomach, fundic stomach, pyloric stomach and small and large intestine were collected. Selected sections were stained with haematoxylin and eosin for hitological examination. Chronic parasitic gastritis produced by Pholeter gastrophilus was the main lesion observed in most of the animals. The macroscopic evidence was the presence of large numbers of granulomas containing parasites or parasite remains in the wall of the two last gastric compartments. Histological analysis revealed multiple foci in the submucosa, contained parasites and parasitic ova surrounded by inflammatory cells, predominantly eosinophils, lymphocytes, macrophages and neutrophils. Surrounding these foci there were abundant fibrosis, which was accompanied with parasite ova and parasite remains, and mixed inflammatory infiltrate composed of multinucleated giant cells, numerous lymphocytes, and plasma cells. Ulceration of the cardiac portion of the stomach, in association with Anisakis simplex infection was observed in two animals. These lesions were present in the ventral mucosal walls of the organ and most were about 0.5 cm in diameter. They were deep, with a punched-out appearance. Histological examination revealed cast cuticles of nematodes surrounded by an intense inflammatory reaction composed of mononuclear cells, polymorph and multinucleated giant cells. There was fibrosis associated with the lesion replacing the muscular layers. Enteritis of unknown aetiology was found in some of the animals that was characterised by an lymphoplasmacytic infiltrate in the lamina propria. One common dolphin had a severe fibrinous peritonitis with abundant presence of fibrin surrounded by a marked infiltrate of neutrophils, lymphocytes and plasma cells that in some areas were spreading into the muscular layer.