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Avian flu feared in Canadian polar bears after disease kills bear in Alaska

The virus first showed up in Yukon more than a year ago in a red fox
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A polar bear mother and her two cubs walk along the shore of Hudson Bay near Churchill, Man. in this Wednesday, Nov. 7, 2007 photo Scientists fear Canadian polar bears may be threatened by the spread of avian flu after officials confirmed the disease killed a bear in Alaska. THE CANADIAN PRESS/Jonathan Hayward

Scientists fear Canadian polar bears may be threatened by the spread of avian flu after officials confirmed the disease killed a bear in Alaska.

鈥淭here鈥檚 a very high likelihood that it is (in Canadian bears),鈥 said Andrew Derocher, a leading polar bear biologist at the University of Alberta.

鈥淚t鈥檚 there. We just aren鈥檛 looking for it.鈥

Last month, officials with the U.S. Department of Agriculture confirmed the H5N1 strain of avian flu killed a polar bear, found in October near the Alaskan town of Utqiagvik about 500 kilometres from the Yukon border. Polar bears range hundreds of kilometres and the dead bear was part of a population shared by both countries.

The virus first showed up in Yukon more than a year ago in a red fox, said territorial veterinarian Jane Harms.

鈥淭his strain of avian flu seems to have the ability to infect and cause disease in mammals of a variety of types,鈥 she said. 鈥淭he fact this virus can cause disease and death in polar bears, as well as other species, is of concern.鈥

It鈥檚 not clear yet how far the virus has spread among Arctic mammals. Alaska has found it in red foxes, a black bear and a Kodiak bear.

Harms said it seems so far it is being spread when mammals eat infected birds.

鈥淚n most cases, wild mammals are being infected by scavenging tissues of infected birds. It does not seem to be transmitted mammal to mammal.鈥

But Derocher said climate change is likely increasing the bears鈥 exposure, as diminishing sea ice keeps them on shore longer and forces them to subsist on prey such as dead birds. Those extended shorebound periods of relative scarcity also weaken the bears.

鈥淚mmune system function goes down. With weakened immune systems, they鈥檙e more likely to succumb.鈥

As well, polar bears are more vulnerable to viruses than other bears, said John Whiteman, chief researcher at Polar Bears International and professor at Old Dominion University in Virginia. While evolving for the Arctic, they lost much of their genetic 鈥渓ibrary鈥 of possible pathogens and how to resist them.

鈥淚f you can recognize a lot of pathogens, you鈥檙e in better shape to fight them off,鈥 said Whiteman. 鈥淧olar bears don鈥檛 recognize a lot of pathogens.鈥

Climate change has stirred the pot on viruses around the world, he said.

鈥淲e know that pathogens are changing their distribution and some of them that may not have been able to survive the north slope of Alaska are gaining a foothold.鈥

Avian flu is now found on every continent except Australia.

Both Whiteman and Derocher called for better monitoring of wildlife diseases.

Harms said Yukon regularly performs necropsies on dead wildlife, but more needs to be done. Confirming avian flu requires extra testing, she said.

鈥淭he reality is we probably would have more avian flu virus infection in mammals if we had the ability to look for it.鈥

The Southern Beaufort population of which the dead bear was a member is estimated to be about 900 strong, although it鈥檚 hard to be sure with polar bears. That population is considered to have declined by about 50 per cent since the 1980s, said Derocher.

The virus has hit other mammals hard. Scientists have linked it to the deaths of nearly 500 seals in Maine over the last two years.

But both Derocher and Whiteman say one bear death isn鈥檛 enough to push the virus panic button.

鈥淚 would put it in the category of a little alarming,鈥 said Whiteman. 鈥淭his threat still has so much unknown to it. But there is a potential for mortality.

鈥淏y far, the biggest threat to this species is the loss of sea ice.鈥

Bob Weber, The Canadian Press

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91原创

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