The first of Alaska's sick seals began to appear in summer 2011. Mostly ringed seals, covered in lesions, were being discovered hauled out on Arctic shorelines. The ones still living were lethargic, and in some cases already dead. Two years later, fewer and fewer cases are being documented, and at least one Alaska researcher believes the fatal illness may have run its course. But scientists are still unsure what caused the unusual mortality event among Arctic pinnipeds.
"They've done all the viral tests, all the bacterial, they've looked into radioactivity, and they've come up with a garden variety of things that are typically found in animals that are sick, but nothing that was a smoking gun," said Cheryl Rosa, a doctor of veterinary medicine and deputy director of the U.S. Arctic Research Commmission's Alaska office, at a public event in Anchorage hosted by Institute of the North last week. "And that's like the most unsatisfying thing for the public to hear, and especially for the subsistence public to hear."
The mortality event in 2011 caused puzzlement among the scientific community, as what appeared to be a particularly devastating disease that caused lesions externally and organ damage internally, arrived suddenly and killed a number of Alaska's marine mammals. Though ringed seals remained the primary affected group, the mystery illness also affected other ice seals and walrus.
In 2012, there were far fewer cases reported, and many animals reportedly spotted with lesions were suspected to be possible survivors of the previous year's outbreak, since the affliction didn't appear to be as severe.
And the improvement has apparently continued. An updated on the event issued by the National Oceanic and Atmospheric Administration in early 2013 said that no new cases had been reported for the year, and NOAA spokeswoman Julie Speegle updated that Friday, saying that the agency had documented "no new confirmed cases in 2013 to date."
According to Dr. Raphaela Stimmelmayr, a research biologist and veterinarian with North Slope Borough Wildlife Management, the seals that are being reported in the last two years with skin abnormalities are much different from the (2011 seals), which were lethargic, often malnourished and allowed humans to approach them.
"What we are seeing now are seals with what seems to be forms of delayed molt, and some of them with shallow sores," Stimmelmayr said. "But these animals are very alert, fat, and in good condition." She said that they believe that these seals could be survivors from the 2011 event.
In Stimmelmayr's estimation, the unusual mortality event has "concluded."
Last week, Dr. Rosa with USARC asserted a similar decline in cases, but warned that since researchers still don't know what caused the outbreak in the first place, it could make another appearance.
"Epidemiologically it seems like this has run its course, but often there can be a kind of rebound set of cases that can occur after," Rosa said, adding later that "there is a possibility that we might see an upswing in this again."
NOAA reports that veterinarians have evaluated various possible causes of the illness, including algal toxins, bacteria and hormones. Members of the public have expressed concern that radiation resulting from the March 2011 earthquake in Japan and subsequent meltdown of the Fukushima-Daiichi nuclear power plant. But researchers looked at that possibility as well, and determined that the radiation levels in seals killed in the 2011 event were similar to radiation levels in samples taken from seals in the mid 1990s.
So though the problem appears to have abated for the time being, it's still frustrating for veterinarians and scientists to have failed to pick out a single cause behind the mysterious mass affliction, Rosa said.
"It's been kind of a highly unsatisfying process," she said.
Contact Ben Anderson at ben(at)alaskadispatch.com