Not just for birds: bird flu also kills wild mammals
As a new version of bird flu spread across North America this spring, scientists began finding the virus in foxes bobcats, bobcats and other mammals.
Something was wrong with the foxes. That's what callers from the Dane County Humane Society in Wisconsin kept saying in April, when they reported fox kits, or young foxes, behaving strangely: shaking, grabbing or struggling to stand. The kits, which were often lethargic and wandering alone, also seemed unusually easy to approach, showing little fear of humans.
"We kept getting calls “said Erin Lemley, a wildlife veterinary technician at the Humane Society Wildlife Center. "And the foxes started coming."
Some of the kits admitted for treatment were quiet and withdrawn, she said. Others stumbled or convulsed, their heads twitching, their eyes blinking rhythmically. After staff ruled out rabies, hypoglycemia, and other potential causes, lab tests revealed a surprising culprit: a highly virulent strain of bird flu.
"It wasn't a fun surprise," said Dr. Shawna Hawkins, zoo and wildlife veterinarian at the University of Wisconsin-Madison.
The virus, a type of bird flu known as Eurasian H5N1, spread rapidly across the United States this spring, infecting domestic poultry flocks in 36 states and causing mass cullings of birds domestic.
But this version of the virus seems to wreak much more havoc on wild birds than previous lines, ending up in ducks, geese, gulls and terns, among many others. This, in turn, means the virus poses an increased danger to mammals that prey on these birds, including wild red foxes.
At least seven states Americans detected the virus in red fox cubs, for which the pathogen seemed to be particularly deadly. Two bobcats in Wisconsin, a coyote pup in Michigan and skunks in Canada have also tested positive for the virus, as have foxes, otters, a lynx, a polecat and a badger in Europe. (Two human cases, one in the US and one in Britain, have also been reported, both in people who had close contact with birds.)
There is no evidence that mammals play a significant role in spreading the virus, and the risk to humans remains low, experts said. "It's still an avian virus," said Richard Webby, an influenza virologist at St. Jude Children's Research Hospital in Memphis.
But the Evolution is a numbers game, he said, and the more mammals the virus infects, the more opportunities it has to detect new mutations that could help it spread among foxes, bobcats or even humans.
“What it will take for this virus to grow from a duck or chicken virus to a mammalian virus is a higher chance of replicate in these mammalian hosts,” Dr. Webby said. "That's why when we see these mammals infected with this virus, we notice it."
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As a new version of bird flu spread across North America this spring, scientists began finding the virus in foxes bobcats, bobcats and other mammals.
Something was wrong with the foxes. That's what callers from the Dane County Humane Society in Wisconsin kept saying in April, when they reported fox kits, or young foxes, behaving strangely: shaking, grabbing or struggling to stand. The kits, which were often lethargic and wandering alone, also seemed unusually easy to approach, showing little fear of humans.
"We kept getting calls “said Erin Lemley, a wildlife veterinary technician at the Humane Society Wildlife Center. "And the foxes started coming."
Some of the kits admitted for treatment were quiet and withdrawn, she said. Others stumbled or convulsed, their heads twitching, their eyes blinking rhythmically. After staff ruled out rabies, hypoglycemia, and other potential causes, lab tests revealed a surprising culprit: a highly virulent strain of bird flu.
"It wasn't a fun surprise," said Dr. Shawna Hawkins, zoo and wildlife veterinarian at the University of Wisconsin-Madison.
The virus, a type of bird flu known as Eurasian H5N1, spread rapidly across the United States this spring, infecting domestic poultry flocks in 36 states and causing mass cullings of birds domestic.
But this version of the virus seems to wreak much more havoc on wild birds than previous lines, ending up in ducks, geese, gulls and terns, among many others. This, in turn, means the virus poses an increased danger to mammals that prey on these birds, including wild red foxes.
At least seven states Americans detected the virus in red fox cubs, for which the pathogen seemed to be particularly deadly. Two bobcats in Wisconsin, a coyote pup in Michigan and skunks in Canada have also tested positive for the virus, as have foxes, otters, a lynx, a polecat and a badger in Europe. (Two human cases, one in the US and one in Britain, have also been reported, both in people who had close contact with birds.)
There is no evidence that mammals play a significant role in spreading the virus, and the risk to humans remains low, experts said. "It's still an avian virus," said Richard Webby, an influenza virologist at St. Jude Children's Research Hospital in Memphis.
But the Evolution is a numbers game, he said, and the more mammals the virus infects, the more opportunities it has to detect new mutations that could help it spread among foxes, bobcats or even humans.
“What it will take for this virus to grow from a duck or chicken virus to a mammalian virus is a higher chance of replicate in these mammalian hosts,” Dr. Webby said. "That's why when we see these mammals infected with this virus, we notice it."
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