Abstract

Starting in July 2011, higher than normal numbers of ringed seals stranded along the North Slope of Alaska. Some seals had skin lesions around the nose, eyes, neck and hind flippers as well as patchy hair loss and abnormal molt. Some were lethargic, had labored breathing, abnormal bleeding and some mortality occurred. Live captured animals were found with similar lesions. Starting in October, spotted, ringed and bearded seals were reported by hunters in the Bering Strait area with primarily abnormal molt and alopecia as well as smaller numbers of animals with ulcerative dermatitis, systemic signs and mortalities. Walrus hauled out in large numbers (approximately 20,000) in Pt. Lay, AK also had a "new" ulcerative skin disease of unknown mortality rate. It was unclear whether the diseases in the two species were due to the same process.

Significant histopathologic lesions were present in skin, respiratory, hepatic, lymphoid, and cardiovascular systems. Skin lesions appeared to be due to vasculitis and later lesions were heavily colonized by a variety of bacteria and fungi. Lungs were primarily congested with some animals demonstrating bronchopneumonia and mucous gland hyperplasia associated with Otostrongylus circumlitus infection.⁴ Liver lesions varied from multifocal random lymphoplasmacytic or suppurative hepatitis with individual cell to lobular necrosis. Young animals had severe thymic atrophy. Lymph nodes early on were hyperplastic progressing to marked lymphoid depletion. Erythrophagocytosis and drainage of hemorrhage were common findings. Some animals had mild myocardial necrosis or lymphocytic myocarditis. Rare animals had pigmentary nephrosis due to hemolysis. In animals in which clinical chemistries were performed, all had elevations in total bilirubin, and some had elevated ALT compared to published values for ringed seals.⁵

Skin and liver were inoculated into multiple cell lines for virus isolation with no definitive isolates as of this date. Electron microscopy has not demonstrated virus, and polymerase chain reaction (PCR) has been negative for an extensive panel of viral agents including known epidemic marine mammal disease agents. Microbiology yielded various bacterial isolates from skin lesions and internal organs including streptococcal organisms and Gemella haemolysans. The skin lesions and senescent hair were often colonized by fungi. These bacterial and fungal agents were of low pathogenicity and were considered to be secondary opportunists. Preliminary molecular analyses for retrovirus, Bartonella and Mycoplasma have yielded some positive results. Ongoing efforts to define a potential pathogen using 4-5-4 high through-put analysis are ongoing.

This disease event most likely has a multifactorial cause. In both ice seals and the walrus, there appears to be abnormalities in molt involved in this event and for this reason has some similarities to Elephant seal skin disease described by Beckmen.² Molt is a complex process described in both ice seals and walrus as well as other marine mammals requiring sequential changes in various hormones and linked to environmental conditions and nutritional factors.^1-3 Therefore the role of factors such as contaminants, biotoxins, nutrition, variations in endocrine function and environmental changes are being investigated.

Acknowledgements

The authors would like to thank the North Slope and Bering Strait region native communities for their contributions to these cases, both carcasses and historical perspectives; H. Brower Jr., Mike Pederson, John Goodman of the Ice Seal Committee, V. Metcalf of the Walrus Commission, Willard Neakok of the Native Village of Pt Lay, Jason Herreman, Cyd Hanns, Craig George, Robert Suydam of the North slope Borough Department of Wildlife Management; Dr. C. Romero at the University of Florida, Dr. K. Beckmen at the Alaska Department of Fish and Game; Drs Carrie Goertz and Pam Tuomi of the Alaska SeaLife Center; B. Mahoney, A. Jensen, K. Savage, T. Rowles of NOAA; Katie Royer of Alaska Veterinary Pathology Services. Funding was provided by a Prescott grants, Alaska Department of Fish and Game, National Marine Fisheries Service contracts to AVPS, and Columbia University.

References

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3.  Fay FH. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens Illiger. North Am Fauna. 1982;74:1–279.

4.  Onderka DK. Prevalence and pathology of nematode infections in the lungs of ringed seals (Phoca hispida) of the western arctic of Canada. J Wildlife Dis. 1989;25(2):218–224.

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