| Summary: | Master Dissertation presented at the University of Trás-os-Montes e Alto Douro to obtain the title of Master in Veterinary Medicine Cetaceans’ strandings have been increasing worldwide and the Portuguese coast is no exception to this phenomenon. Necropsy of stranded animals provides important data regarding their biology and health status. The aim of the present study was to assess and characterize the occurrence of gastric ulcerative lesions in stranded cetaceans along the north and central coast of mainland Portugal during the period 2015 to 2020. The species under study included Delphinus delphis (common dolphin), Phocoena phocoena (harbour porpoise) and Stenella coeruleoalba (striped dolphin). In this study, data from a total of 698 stranded small cetaceans, with reported gastric ulcerative lesions at necropsy, were collected and analysed. A macroscopic and histopathological evaluation of the lesions was carried out. A morphological evaluation of the parasites found within the animals’ stomach was also performed. The majority of stranded animals were sexually immature and with good body condition. Both sexes were equally stranded. The highest gastric ulcers occurrence was observed in young animals (p < 0.001), and in animals with good body condition (p = 0.023). The majority of ulcerative lesions showed to be in an active stage, presented small dimension, as well as a multifocal distribution within the forestomach. The presence of multifocal gastric lesions was more common in animals with good body condition (p = 0.0038). Gastric ulcers were associated to chronic gastritis with granulomatous features. Nematode parasites, its remains or eggs were frequently observed within the lesions. The parasites’ morphological features were compatible with Anisakis spp., with site of infection more often observed in the forestomach. An association was noticed between higher parasite loads and the occurrence of multifocal ulcerative lesions (p = 0.001). According to the present study, strandings and ulcerative ...
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