The Veterinary Record, September 23, 2006 THERE have been few postmortem investigations of the dis- eases and causes of death of free-living dolphins and whales found stranded on the coast of the Canary Islands. Since 1992, there have been several strandings of one or more adult and juvenile cetaceans, and information obtained from these animals has been collected by the Histology and Pathology Unit of Las Palmas of Gran Canaria University. In contrast with domestic mammals, much basic informa- tion about the natural history, immunity and other important characteristics of marine mammals is lacking, and as a result it is sometimes difficult to interpret the pathological findings. In addition, knowledge about the occurrence and nature of many of their diseases is far from complete, although it has greatly advanced in the past two decades (García Hartmann 1997). In the study of the causes of death of stranded cetaceans, gastrointestinal disease has been investigated extensively (Baker 1992, Di Guardo and others 1995, Kirkwood and oth- ers 1997). Gastric ulcers due to infections by the nematode Anisakis simplex, and a small focus of fibrotic gastritis at the site of attachment of the trematode Pholeter gastrophilus to the gastric mucosa, have been commonly observed in these animals (Johnston and Woodard 1969, Woodard and others 1969, Migaki and others 1971, Baker 1992, Baker and Martin 1992, Di Guardo and others 1995, Kirkwood and others 1997, Wunschmann and others 2001). However, the nature of the inflammatory infiltrates associated with these gastrointestinal lesions has not been studied. Several commercially available antibodies to CD3, immunoglobulin (Ig) G, IgM, IgA, S-100 protein, major histocompatibility complex (MHC) class II and lysozyme have shown cross-reactivity with paraffin-embed- ded cetacean tissue samples (Jaber and others 2003a), and they have been used to study hepatic inflammatory lesions (Jaber and others 2003b). These antibodies should make it possible to characterise the inflammatory infiltrates associated with gastrointestinal parasitic lesions, and help to understand the pathogenesis of the lesions, such as granulomatous gastritis, and to investigate possible dysfunctions of the local immune response and its relationship with severe parasitism. This paper describes the results of a study of the gross, histopathological and immunohistochemical characteristics of the parasitic lesions observed in the gastrointestinal tracts of 23 dolphins stranded in the Canary Islands. MATERIALS AND METHODS Animals The 23 carcases were of both sexes and included pups, juve- niles and adults, as determined by their body length in rela- tion to the known range of lengths of the different species, and the maturity of their sexual organs (Table 1). They had been stranded alive and died on the coast; six of them were common dolphins (Delphinus delphis), six were Atlantic spot- ted dolphins (Stenella frontalis) and 11 were striped dolphins (Stenella coeruleoalba). They were selected because they were well preserved specimens among the dolphins necropsied by the Histology and Pathology Unit. Pathological and parasitological studies The carcases were examined according to the standard pro- tocol for cetaceans described by Kuiken and Baker (1994). All the major internal tissues and organs were examined carefully, both superficially and on a cut surface. Samples of the forestomach, fundic and pyloric glandular stom- ach, small and large intestine and associated lymph nodes were taken, fixed in 10 per cent neutral buffered formalin, dehydrated through graded alcohols and embedded in par- affin wax. Sections 4 μm thick were cut and stained with haematoxylin and eosin and Giemsa stain for histological examination. Any worms found were fixed overnight and then stored in 70 per cent ethanol before being identified. The presence of cuticular spines and yellow eggs with a single operculum and the absence of a body cavity were the criteria used to identify P gastrophilus (Johnston and Woodard 1969, Woodard and others 1969, Migaki and oth- ers 1971). Parasitism by A simplex (Anisakidae) was also observed in the forestomach of the striped and common dolphins. The Y-shaped lateral cords of the nematodes sug- gested that they belonged to the genus Anisakis (Johnston and Woodard 1969, Woodard and others 1969, Migaki and others 1971). Similar criteria were used to identify a cestode Pathological and immunohistochemical study of gastrointestinal lesions in dolphins stranded in the Canary Islands J. R. Jaber, J. Pérez, M. Arbelo, R. Zafra, A. Fernández This paper describes the gross, histopathological and immunohistochemical characteristics of gastrointestinal lesions and regional lymph nodes of six common dolphins (Delphinus delphis), 11 striped dolphins (Stenella coeruleoalba) and six Atlantic spotted dolphins (Stenella frontalis) found stranded along the coasts of the Canary Islands. The most common lesion was chronic granulomatous gastritis of the glandular stomach, associated with the parasite Pholeter gastrophilus, and characterised by the parasites, their eggs, or parasite debris in the mucosa, submucosa or tunica muscularis, surrounded by numerous lysozyme-positive macrophages and neutrophils, and more peripherally by abundant fibrous tissue containing variable numbers of immunoglobulin (Ig) G + plasma cells, and small numbers of CD3 + T lymphocytes and IgM + and IgA + plasma cells. Anisakis simplex nematodes were found in two dolphins that were also parasitised by P gastrophilus and had parasitic granulomatous gastritis and multiple small chronic gastric ulcers. Lymphoplasmacytic enteritis was found in eight cases, three of them parasitised by Diphyllobothrium species; the lesion was characterised by moderate to severe infiltrations of CD3 + T lymphocytes and IgG + plasma cells, with small numbers of IgM + and IgA + plasma cells in the lamina propria and submucosa, mainly of the small intestine. One dolphin had severe fibrinopurulent peritonitis, which may have been secondary to gastric perforation caused by the large mural granulomatous gastritis associated with P gastrophilus parasitism. Veterinary Record (2006) 159, 410-414 J. R. Jaber, DVM, PhD, M. Arbelo, DVM, A. Fernández, DVM, PhD, Instituto de Sanidad Animal, Facultad de Veterinaria, Universidad de Las Palmas de Gran Canaria, Trasmontaña sn, 35416 Arucas, Las Palmas de Gran Canaria, Spain J. Pérez, DVM, PhD, R. Zafra, DVM, Departamento de Anatomía y Anatomía Patológica Comparadas, Facultad de Veterinaria, Universidad de Córdoba, Edificio Sanidad Animal, Campus de Rabanales, Ctra. Madrid-Cádiz km 396, 14014 Córdoba, Spain Correspondence to Dr Fernández Papers & Articles