Mystery disease is killing Arctic seals
New Scientist, December 10, 2011
VETERINARIANS in Alaska are at a loss to explain a disease that has killed almost 200 Arctic ringed seals since July. The animals' hair falls out, they develop ulcers on their flippers and skin, and they have lesions in their lungs, livers, hearts and brains. The disease may have spread to other species including spotted seals, bearded seals and walruses.
"We don't know what's causing it," says Julie Speegle, speaking for the US National Oceanic and Atmospheric Administration's office in Alaska. Tests have ruled out viruses including poxvirus, papillomavirus and morbillivirus,which killed hundreds of seals in Europe in 1988. Vets continue to screen for other viruses, bacteria and fungi, and for algal toxins and others that may be responsible.
Similar seal deaths have been reported in Canada and Russia, where scientists have joined the investigation. NOAA has advised hunters not to eat any sick seals in case the agent can also infect humans.
What illness is harming Alaska's ringed seals? Veterinarians search for clues.
Scientists hoping to learn what's killing Arctic ringed seals, an affliction that's peppered the animals' skin and organs with ulcers, turned their attention Monday to a fresh seal carcass shot by a Northwest Alaska subsistence hunter.
In a cramped University of Anchorage laboratory, veterinarians and assistants in biomedical scrubs carved the big marine mammal into bits, all in the name of science.
They plucked out eyeballs, sliced off skin, and snapped open ribs with garden-pruning shears. They clipped nails, pulled whiskers and placed pieces into vials and plastic bags for shipment to several labs in the Lower 48 and Canada.
Part of an international mystery, more than 45 ringed seals have been found dead in Alaska's Arctic since late July, gathering on beaches instead of ice floes, which they prefer. The North Slope Borough's wildlife experts said dozens more were reported sick with the lesions and patchy hair loss.
Skin sores have also recently been found on ringed seals in Russia and Canada, as well as walrus in Northwest Alaska and harp seals in Greenland, giving marine mammal experts plenty to ponder.
Is the widespread sickness from the same thing? Is it caused by a virus, bacteria, toxin or fungus? Is this a new disease or an old malady never known to scientists in the little-studied Arctic? And what role could climate change play?
"The big question is is this something new?" said Kathy Burek-Huntington, a private veterinary pathologist who's spearheading the lab work.
Some Native communities are now saying they've seen these symptoms before, she said. But there's no record of ringed seals die-offs because of these problems. The search for an answer extends far and wide. Experts are headed to remote villages to learn more about traditional observations. Scientists across the Arctic are talking. And an international panel of marine-mammal experts is tracking the situation, with the National Oceanic and Atmospheric Administration and the U.S. Fish and Wildlife serving as lead agencies.
The questions have gone on more than two months, since August. Burek-Huntington has cut up some dozen seals and dissected a walrus, too. She's sent off hundreds of samples and stored maybe a thousand others in special freezers that push temperatures to minus-80 F.
Much of the work has focused on finding a virus, to no avail. They've ruled out herpesvirus, poxvirus, papillomavirus, morbillivirus and others. The search for a bacterial cause hasn't yielded answers either.
It's not a toxin, she's believes.
"We're still looking into toxins that might cause immunosuppression," she said, including radiation.
On Monday morning, she and others -- including state veterinarian Bob Gerlach and Alaska Sealife Center's Pam Tuomi - knew the dissection wouldn't bring them any closer to an answer.
But the carcass was in excellent shape for a necropsy - with no odor until they reached the intestines -- and even then a just-bearable tang. Fresh samples are hard to come by these days because seals that have hauled out to die are freezing as winter approaches.
But this one had been shot Saturday, near Shishmaref, an Inupiat coastal village on the Seward Peninsula. The hunter noticed the warning signs, contacted the Marine Advisory Program in Nome for advice and kept the seal insulated so it wouldn't freeze before the plane arrived in the village. It reached Anchorage in a body bag and cardboard box.
"It was a really effective shot," said Burek-Huntington, pointing out the bullet hole into the brain. "He died quickly."
On websites and village poster boards, organizations have warned subsistence hunters to watch out for seals with such symptoms as lesions around the rear flippers, said Gerlach. Just in case it might spread to humans, they've recommended that hunters not eat those animals but instead contact local wildlife officials to have them shipped off.
The site of this kill indicates that whatever ails ringed seals may not confined to the North Slope.
This ringed seal had the same symptoms as the others the veterinarians have seen, but it was relatively healthy, said Burek-Huntington, judging from its two-inch layer of fat and well-developed muscles. Also, the lesions ringing the bulging eyes, and the bright pink sores on the rear flippers, were fewer and smaller.
But it had bigger problems. With help from Tuomi, Burek-Huntington rolled the wobbly bag of flesh onto its back. It appeared to be in mid-molt, with a shiny, copper-colored coat covering the rings that give the animals its name. Molting should have ended much earlier, Burek-Huntington said, peeling off tufts of fur and placing them in plastic bags.
And once the animal had been sliced open -- its skin lay off to the sides like an unbuttoned parka -- the team found more clues in the innards.
The liver was more orange-colored than it should have been, and had abnormal spots. Hepatitis and swollen livers have been a common symptom in the dissected seals.
"Heavy drinker," wise-cracked Gerlach.
"Yeah, the stress of climate change is getting to them," Burek-Hungtington said, milking the joke.
The lymph nodes were also inflamed, discolored and sometimes spotted, proof the seal had an infection of some sort.
"Guys, we need a camera," said Burek-Huntingon, calling to an assistant after finding an unusually large lymph node near the rear flippers.
"Whoa," said the assistant before snapping away.
Burek-Huntington started work in Alaska about 15 years ago. She's often part-detective, and today her caseload includes work on the possible impact of climate change on marine mammals.
She's written a paper with other scientists on that very question. It notes that, among other things, new animals and bugs could bring diseases north, spreading illness to previously healthy animals. As ice floes get smaller and vanish, animals often crowd together in mobs, increasing the spread of disease. Pathogens can survive longer in warmer temperatures. And food supply could be threatened, making animals weaker and more likely to get sick.
Who knows if any of that's at work here? Burek-Huntington said. More importantly, for now, is figuring out what's killing the seals today.
Contact Alex DeMarban at alex(at)alaskadispatch.com
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