Retrospective study of foreign body-associated pathology in stranded cetaceans, Canary Islands (2000-2015).

Marine pollution, overrepresented by plastic, is a growing concern worldwide. However, there is little knowledge on occurrence and detrimental impacts of marine debris in cetaceans. To partially fill in this gap of knowledge, we aimed to investigate the occurrence and pathologies associated with foreign bodies (FBs) in a large cohort of cetaceans (n = 465) stranded in the Canary Islands. The Canary Islands shelter the greatest cetacean biodiversity in Europe, with up to 30 different species, of which nine are regularly present year around. We found at least one ingested FB in 36 out of 465 (7.74%) studied cetaceans, involving 15 different species, including eight out of the nine (80%) cetacean species present year-round in the Canary Islands. Risso's dolphin was the species most affected, followed by sperm whale, beaked whale and mysticetes. Plastic FB were the most common item found (80.56%). FB was directly associated with death in 13/36 (36.11%) animals. Poor body condition and deep diving behavior were found to be risk factors for FB ingestion, whereas the adult age was a protective factor. To the authors knowledge this is the first study that use statistical analysis to investigate risk and protective factors for FB ingestion. This study also provides insights of the potential impact caused by ingested FBs on the animal's health and mortality. This knowledge is critical to better understand and assess the impact of FB in cetaceans setting the scientific basis for prospective impact monitoring and future conservation policies.

Deadly acute Decompression Sickness in Risso's dolphins.

Diving air-breathing vertebrates have long been considered protected against decompression sickness (DCS) through anatomical, physiological, and behavioural adaptations. However, an acute systemic gas and fat embolic syndrome similar to DCS in human divers was described in beaked whales that stranded in temporal and spatial association with military exercises involving high-powered sonar. More recently, DCS has been diagnosed in bycaught sea turtles. Both cases were linked to human activities. Two Risso's dolphin (Grampus griseus) out of 493 necropsied cetaceans stranded in the Canary Islands in a 16-year period (2000-2015), had a severe acute decompression sickness supported by pathological findings and gas analysis. Deadly systemic, inflammatory, infectious, or neoplastic diseases, ship collision, military sonar, fisheries interaction or other type of lethal inducing associated trauma were ruled out. Struggling with a squid during hunting is discussed as the most likely cause of DCS.

Uterine Leiomyoma and Prolapse in a Live-stranded Atlantic Spotted Dolphin (Stenella frontalis).

A uterine prolapse associated with a leiomyoma (fibroid) was observed in a live-stranded Atlantic spotted dolphin (Stenella frontalis). A 7 cm segment of the reproductive tract including the cervix, uterine neck and caudal uterine body had intussuscepted and prolapsed into the cranial vaginal vault. In the leading edge of the intussuscepted/prolapsed uterine wall was a 6 × 3 × 3.5 cm leiomyoma expanding the myometrium. The leiomyoma and prolapse were associated with necrotizing exposure endometritis. This is the first report of a uterine prolapse associated with a leiomyoma in a cetacean. This lesion was believed to be the underlying cause of the live stranding.

High-grade astrocytoma (Glioblastoma Multiforme) in an Atlantic spotted dolphin (Stenella frontalis).

This report describes the gross, microscopical and immunohistochemical features of a high-grade astrocytoma (glioblastoma multiforme) in an adult male Atlantic spotted dolphin (Stenella frontalis). On necropsy examination, a 5 × 2.5 × 2 cm, poorly demarcated, red, friable and locally expansile mass effaced the thalamus and the left periventricular region and extended to the left lateral ventricle of the brain. Microscopically, the mass consisted of haphazardly arranged bundles and rows of interweaving polygonal to spindle-shaped cells. These often palisaded along serpentine foci of necrosis and were surrounded by prominent vessels. Immunohistochemically, the neoplastic cells expressed glial fibrillary acidic protein, but not vimentin, S100 protein, neuron-specific enolase or neurofilament protein. A diagnosis of high-grade astrocytoma was made and this represents the first description of a glioma in a cetacean species.

Capture myopathy in live-stranded cetaceans.

A group of 51 cetaceans that had been stranded alive on the coasts of the Canary Islands, experienced human capture/rescue interactions and then died, were necropsied over a 12-year period. Of these cetaceans, 25 had haemodynamic lesions indicative of multiorganic vascular shock, degenerative muscle lesions affecting both skeletal and cardiac muscles and myoglobinuric nephrosis typical of capture myopathy (CM). Because macroscopic lesions in muscles and kidneys were not always obvious, a standard protocol was developed where the longissimus dorsi muscle was examined histologically for segmental hypercontraction, contraction band necrosis and segmental muscular degeneration and cardiomyocytes studied for hypereosinophilic wavy fibres, sarcolemmal and perinuclear vacuolation and contraction band necrosis. Light microscopic skeletal and cardiac muscle lesions in all CM animals were confirmed as ante mortem by immunohistochemical assay for myoglobin loss from and fibrinogen entry into affected myofibres. All animals had tubular nephrosis with casts and tubular myoglobin. The oxidative stress-related marker HSP70 was demonstrated immunohistochemically in tubular epithelium. Although the syndrome related to death of live-stranded cetaceans is multifactorial, this study documents that a clinicopathological syndrome comparable to CM of terrestrial wildlife has a role in stranding outcomes.