Pathological study of a mass stranding of spinner dolphins (Stenella longirostris) in the Canary islands

Abstract

A mass stranding of spinner dolphins (Stenella longirostris) took place in Tarajalillo (San Bartolome de Tirajana), located in the southeast coast of Gran Canaria (Canary Islands), the 27th of August, 2004. A total of five spinner dolphins beached, and two of them were returned alive to deeper water. Two of the remaining three animals were a juvenile and a subadult dolphins, which died after a short period of time; the third one, an adult male, was transported to the Marine Wildlife Rescue Centre where it was euthanized a few hours later due to its bad health condition. This record should be considered like extralimital and it was associated to the highest SST (Sea Surface Temperature) values known for the Canarian Archipelago. A pathological study was carried out at the Veterinary School of the University of Las Palmas de Gran Canaria where all three animals were examined post-mortem following a systematic necropsy procedure. Macroscopically, the most relevant findings in the young dolphins were a strong parasitation by nematodes in the lungs and a moderate infestation by trematodes (Nasitrema sp.) in the pterygoid sinuses. The adult one presented a severe generalized chronic dermatitis associated with a marked poor body condition microscopically characterized as an interstitial exudative dermatitis with a hyperplasic epidermis. Other histopathological lesions in this animal were a broncho-interstitial pneumonia and a chronic reactive hepatitis. Social cohesion is suspected to be the cause implicated in this mass stranding event of spinner dolphins, as one of the animals (the adult one) was clearly sick comparing with the rest of the dolphins (the subadult and the juvenile), but a final diagnosis is lacking.