The Alaskan Pinniped and Walrus Unusual Mortality Event: 2011-2012

In 2011, an ulcerative dermatitis and alopecia emerged among ice associated Arctic seals and potentially Pacific Walruses, on the Arctic Slope, Western Arctic, and Bering Strait.  The observed increased morbidity and mortality among seals and Pacific walruses led to the subsequent declaration of an unusual mortality event for these species by NOAA and the USFWS. To date, this disease of seals has been confirmed in the US Arctic, NWT (CA), Chukotka (Ru), and northern Japan. In response to the disease event a large scale trans-boundary interdisciplinary disease investigative team joining Native hunters from Alaska, Chuktoka, NWT and international scientists was assembled.  Comprehensive tier 1 and tier 2 disease investigative efforts were being pursued. Initial investigative efforts have ruled out numerous bacteria, viruses, contaminants and algae toxins known to affect marine mammals. Advanced testing techniques for unidentified infectious agents is continuing as well as further testing for potential other causes including, radiation, auto-immune, nutritional, hormonal and environmental factors. Currently no specific cause has been identified. The disease is characterized by a variety of skin associated lesions (ulcers/erosion) with body site specific distribution (eyes; snout; hind flippers; tail, trunk) for ice seals and a more generalized distribution for Pacific walrus. All age classes have been affected in ice seals. For Pacific walrus sub-adults and calves appear primarily affected. Affected ice seals displayed uncommon behaviors such as unusual approachability, lethargy, and increased tendency for hauling out on land. In some animals respiratory signs are prominent. Gross necropsy and histopathological lesions found in seals and walruses were associated with the respiratory system, the liver, the immune system, and the skin associated vascular bed.  Disease surveillance efforts in 2012 and 2013 indicate that the disease event has come to an end as no new cases similar to the initial 2011 clinical presentation were observed. Ice seals and Pacific walruses are key species within the Arctic Ecosystem and an essential marine subsistence resource for Native communities throughout the Arctic. Thus food safety and food security aspects are integral components of this emerging Arctic marine mammal disease.