Deaths of Ringed Seals in Alaska an Unusual Mortality Event
JUNEAU, Alaska, December 20, 2011 (ENS) – The National Oceanic and Atmospheric Administration today declared the recent deaths of ringed seals in the Arctic and Bering Strait regions of Alaska an unusual mortality event, triggering a focused, expert investigation into the cause of these deaths.
Since mid-July, more than 60 dead and 75 diseased seals, most of them ringed seals, have been reported in Alaska, with reports continuing to come in.
During their fall survey, scientists with the U.S. Fish and Wildlife Service also identified diseased and dead walruses at the annual mass haul-out at Point Lay.
A decision by the Service on making an an unusual mortality declaration for Pacific walrus in Alaska is pending.
Ringed seal with patchy hair loss and lesions on its face (Photo courtesy NOAA)
Seals and walruses suffering from this disease have skin sores, usually on the hind flippers or face, and patchy hair loss. Some of the diseased animals have exhibited labored breathing and appear lethargic and do not flee from humans as they usually do.
Scientists have not yet identified a single cause for this disease, though tests indicate a virus is not the cause.
Dr. Stephen Raverty, veterinary pathologist with the Provincial Veterinary Diagnostic Lab in British Columbia, told reporters on a conference call today that the lesions on these animals are much more severe than the patchy hair loss usually seen.
“These appear to be ulcerated lesions with secondary infections,” he said. “Opportunistic yeast and fungi and bacteria have invaded.”
But Dr. Raverty said scientists still have not determined the cause or causes of these deaths. “Our analysis is not completed,” he said. “It could be an environmental factor or more than one disease.”
“We have forwarded the sampled tissues to labs – bacteria, mycology, virology,” he said. “We are screening for 18 recognized pathogens, but all the lab results have come back negative.”
“We think defects in the skin are allowing pathogens to migrate into the animals,” Dr. Raverty said. “Bacteria are becoming blood borne and localizing to the liver, causing white spots on the liver, hepatitis and fluid in the lungs.”
Necropsies have found abnormal growths in the brain. Some seals and walruses have undersized lymph nodes, which may indicate compromised immune systems.
Testing continues for a wide range of possible factors that may be responsible for the animals’ condition, including immune system-related diseases, fungi, man-made and bio-toxins, radiation exposure, contaminants, and stressors related to sea ice change.
Hunters continue to see numerous healthy animals, and despite considerable contact with seals by hunters and field research personnel throughout this event, no similar illnesses in humans have been reported.
Still, it is not known whether the disease can be transmitted to humans, pets, or other animals.
Polar bears are one of the main predators on ringed seals, but scientists have not observed any health issues in polar bears, said Dr. Raphaela Stimmelmayr, a wildlife veterinarian and research biologist with the North Slope Borough Department of Wildlife Management in Alaska.
Walruses and ringed seals in Russia, and ringed seals in Canada, have reportedly suffered similar symptoms. While it is not clear if the disease events are related, the timing and location of the disease suggests the possibility of transmission between the populations, or shared exposure to an environmental cause.
Since early November, federal agencies and partners have been consulting with the Working Group on Marine Mammal Unusual Mortality Events, a group of experts from scientific and academic institutions, conservation organizations, and state and federal agencies, to consider if the seal and walrus deaths met the criteria for an unusual mortality event. Late last week, the Working Group recommended NOAA and the Fish and Wildlife Service declare an unusual mortality event.
The collaborative investigation into these deaths has and will continue to involve the North Slope Borough, numerous organizations, local communities, tribal entities, and members of the Alaska Marine Mammal Stranding Network, including the Alaska SeaLife Center, Alaska Sea Grant Marine Advisory Program, and Alaska Department of Fish and Game. These investigations may require months or even years of data collection and analysis, said NOAA.
Native subsistence hunters are advised to use traditional and customary safe handling practices, and the Alaska Division of Public Health recommends fully cooking all meat and thoroughly washing hands and equipment with a water-bleach solution.
Anyone who encounters a seal or walrus that looks sick or behaves unusually should avoid approaching or making contact with the animal.
Sick or dead marine mammals should be reported to the following agencies, based on where the animal is seen:
* North Slope area: North Slope Borough Department of Wildlife Management: 907-852-0350 * Bering Strait region: Alaska Sea Grant Marine Advisory Program: 1-800-478-2202 or 907-443-2397 * Elsewhere in Alaska: NOAA Fisheries Alaska marine mammal stranding hotline: 1-877-925-7773
NOAA’s Alaska regional fisheries website has more in-depth information about this disease outbreak in ringed seals and walruses. The agency says any findings of public health significance will be immediately released.
NOAA will work with local native organizations, including the Ice Seal Committee and the Eskimo Walrus Commission, to ensure that information is distributed to affected communities.