Abstract

Marine mammal subsistence hunting has sustained the North Slope Iñupiat Eskimos for thousands of years. The ringed seal (Phoca hispida), bearded seal (Erignathus barbatus) and walrus (Odobenus rosmarus divergens) are important subsistence resources. Diminishing sea ice, increased ship traffic and expanding oil and gas development in the Chukchi and Beaufort Seas have the potential to devastate habitat critical to the survival of the animals that feed and clothe subsistence hunters and their families. Scientists with the North Slope Borough Department of Wildlife Management in Barrow, Alaska are working closely with community members from the North Slope Borough villages to monitor the health of subsistence resources with the intent of generating baseline data sets from areas not yet impacted by industrial development. Tissues were collected from 86 bearded seals, 20 ringed seals, and 16 walruses during the 2008 and 2009 subsistence harvests. Routine formalin-fixed tissues were prepared and examined at the Colorado State University Medicine Center. Approximately 800 H & E stained slides were examined for disease surveillance and histological changes associated with contaminants. Mild exertional rhabdomyolysis with loss of sarcoplasmic detail, fragmentation, myositis, repair and healing was consistently observed. Sarcocysts were identified in the skeletal muscles of seals, but not walruses. Endoarteritis in ringed seals with moderate to severe fibromuscular- intimal proliferation, fragmentation of the internal elastic membrane, and thrombi formation indicative of Acanthocheilonema spirocauda infection was repeatedly observed. Parafilaroides spp. were positively identified in sections of lung from ringed seals and were implicated in the presence of verminous pneumonia in bearded seals. A consistent finding among all sections of liver examined from seals and walruses was focal areas of hypertrophied Kupffer cells, occasional neutrophils and lymphoplasmacytic infiltration suggestive of parasitic migration through the liver parenchyma. Positive identification of eggs and flukes consistent with Orthosplanchnus spp. infection along with moderate to severe chronic active cholangitis, cholangiohepatitis and hepatocellular necrosis caused by fluke presence was a common finding. The same flukes were responsible for inflammation and fibrosis of the pancreatic ducts and periportal fibrosis. There was no histopathological evidence of renal colonization with Leptospira spp. Histological evidence of immunosuppression or endocrine disruption associated with environmental contaminant exposure was not observed. One seal had pyogranulomatous panniculitis, likely due to a bite wound. The seals and walruses sampled were in good overall health and excellent body condition. Continued surveillance of the health of these important subsistence resources is warranted. Future studies are also directed at using IHC and PCR techniques to determine if the sarcocyst repeatedly observed in the ringed and bearded seal skeletal muscle is different from those previously described in existing marine mammal literature. Immunohistochemistry for immunoreactivity to Brucella antibodies in Parafilaroides positive lung sections is planned.

Acknowledgements

The principal investigator wishes to acknowledge the overwhelming kindness and generosity extended to her by members of the North Slope villages, allowing her to examine and collect tissues from their seals and walruses and inviting her into their homes and lives to share in the fruits of their harvests. The contributions these people have made to the investigator's veterinary pathology training and the marine mammal scientific community exemplify the cooperation and collaboration between subsistence hunters, traditional knowledge and the scientific community. Special thanks to UAF doctoral student Jill Seymour for her assistance with tissue collection. Quyanaqpak!