From 2009 till the first quarter of 2012, 150 seals (133 Phoca vitulina and 17 Halichoerus grypus) stranded in the province North Holland included Texel. These seals were found dead or died/euthanized at the rehabilitation center Ecomare. Necropsy was performed conform a protocol at the University Utrecht, Faculty of Veterinary Medicine. Dept. Pathobiology. Macroscopic, microscopic, immunohistochemical, microbiological and parasitological examinations were performed, to get information about the health status of the Dutch seal population.
The respiratory and alimentary systems were most commonly affected by pathological changes. Also trauma was seen on the seal carcasses, 56 seals had signs of blunt trauma but also in lesser extent sharp trauma and fractures were seen.
The respiratory tract: Pathological changes that were most commonly seen were nematodiasis (46.7%), pneumonia (36%) chiefly a bronchopneumonia and pulmonary edema (43.3%). Other important pathological findings were: pulmonary emphysema, pulmonary hyperemia and foam and/or fluid in the airways. The causes of pneumonia were lungworms (21.3%), bacteria (1.3%), unknown causes (7.3%) or both bacteria and lungworm (6%). Bacteria that were cultured out of the lungs were: Streptococcus species, Escherichia coli, Clostridium, Gemella species and mixed cultures.
The alimentary tract: Parasites were macroscopically found in the esophagus (13.3%), stomach (42.7%), intestines (26%), and liver (1.3%). The presence of parasites in the stomach was associated with hyperemic mucosa, ulceration of the stomach wall, thickened stomach wall and mucous, hemorrhagic or pica contents.
Pathological changes were commonly found on the liver, these changes were inflammatory (9.3%) by the bacteria Streptococcus, Brucellosis, Escherichia coli and mixed cultures, hepatomegaly (8%), and liver necrosis (8%).
Trauma: Blunt trauma (37.3%) was associated with haemorrhage and/or edema in the sub-cutis, blubber or muscles. Locations of blunt trauma were the chest (18%), head (14%), shoulders (10%) and neck (8.7%). Sharp trauma located mostly on the flippers (front 2.6%, back 1.3%). Skin lesions were found in 30 seals but this would probably be more, but due to scavenging no differentiation could be made. Also bone fractures (8.6%) were seen, mostly on the skull (4.7%).
The causes of death were euthanasia ( 26%), infectious cause ( 22.7%), unknown (19.3%), emaciation (13.3%), trauma (8.7%), by catch (4%) and other causes (6%).
In total 36.6% of the seals (mostly neonates and juveniles) died because of respiratory problems. 32 of these seals (21.3%) were euthanized in Ecomare. The other seals that died without human interference, died because of inflammation of only the lungs (11.3%) or inflammation of lungs and other organs (4%).
Keywords: Phoca vitulina, Halichoerus grypus, stranding, diseases, mortality, necropsy, pathology, North Holland and Texel.||
|dc.subject.keywords||Phoca vitulina, Halichoerus grypus, stranding, diseases, mortality, necropsy, pathology, North Holland and Texel.||