Last year more than 100 seals in Alaska showed symptoms of a mysterious and often fatal disease. Last fall, 162 seals were found dead along the New England coast. Scientists say there is no connection.
A study published Tuesday by the American Society of Microbiology blamed the Atlantic die-off on a new strain of avian flu that jumped into the seal population. But experts with the National Oceanic and Atmospheric Administration said they are confident that whatever killed the Alaska seals it wasn't bird flu.
A statement from NOAA's National Marine Fisheries Service Alaska Region issued Wednesday stressed that avian flu "is not a factor in the Alaska unusual mortality event that has been affecting Alaskan marine mammals for the past year. ... (When) sick seals first appeared last year, pathologists immediately tested for bird flu since Alaska is a major flyway for birds and therefore a possible location for introduction of bird flu."
The Alaska marine mammals tested negative for the flu, the statement said, and tissue taken from the skin and lungs of the animals was different from that taken from the New England seals.
A summary of the investigation of Alaska deaths released by NOAA and the U.S. Fish and Wildlife Service on June 25 noted that seals here showed hair loss, skin sores or other symptoms. Forty percent were found dead. So far this year, subsistence hunters have documented more than 40 diseased seals. Some walruses have also been affected though the herds checked recently generally look healthy.
A similar hair loss in polar bears along the Arctic Ocean coast was noted in 2011. But NOAA says that all bears taken by hunters from Gambell this spring have been "normal and healthy."
Necropsies have been performed on 30 Alaska animals, and skin samples collected from living ones allowed scientists to rule out bird flu. Results of advanced testing procedures and testing for heavy metals or radiation poisoning are pending.
NOAA investigators state "no environmental factor or disease can be ruled out" and suggest that "the underlying cause of this disease is most likely complex, involving a variety of factors."
There is no evidence that people can contract the disease exhibited by the sick Alaska animals by handling or consuming them, the report said.
There is also no indication that humans are capable of contracting the flu virus strain found in the New England seals, a new strain of the influenza A virus, called H3N8. But given that it's proved capable of jumping from birds to marine mammals, scientists plan further study.
"Any time we find a new virus, there's a concern that it's going to have a larger impact than on the population in which we originally find it," said W. Ian Lipkin, an author of the report on Atlantic seal deaths and a professor of epidemiology at the Mailman School of Public Health at Columbia University.
Other strains of H3N8 have been found in dogs and horses, but this strain had many new mutations that make it different, Lipkin said. The report said the emergence of the strain "must be considered a significant threat to both wildlife and public health."
The report on the Atlantic seal deaths was compiled by scientists at the Center for Infection and Immunity at Columbia University's Mailman School of Public Health; NOAA; New England Aquarium; U.S. Geological Survey National Wildlife Health Center; SeaWorld; and EcoHealth Alliance.
The report notes that other influenza strains have been the cause of seal deaths over the years.
This story was reported by the Associated Press and Daily News reporter Mike Dunham.