AVIAN INFLUENZA (01): AMERICAS (USA) POLAR BEAR
A ProMED-mail post
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International Society for Infectious Diseases
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Date: Sat 30 Dec 2023
Source: Alaska Beacon [edited]
https://alaskabeacon.com/2023/12/30/avian-influenza-death-of-alaska-polar-bear-is-a-global-first-and-a-sign-of-the-virus-persistence/
A polar bear found dead on Alaska’s North Slope is the 1st of the
species known to have been killed by the highly pathogenic avian
influenza that is circulating among animal populations around the
world.
The polar bear was found dead in October [2023] near Utqiagvik, the
nation’s northernmost community, the Alaska Department of
Environmental Conservation reported.
The discovery of the virus in the animal’s body tissue, a process that
required sampling and study by the North Slope Borough Department of
Wildlife Management and other agencies, confirmed earlier this month
[December 2023] that highly pathogenic avian influenza was the cause
of death, said Dr. Bob Gerlach, Alaska’s state veterinarian.
“This is the 1st polar bear case reported, for anywhere,” Gerlach
said. As such, it was reported to the World Organisation for Animal
Health and has gotten attention in other Arctic nations that have
polar bears, he said.
This was also the 1st Endangered Species Act-listed animal in Alaska
known to fall victim to the disease. Polar bears, dependent on sea ice
that is diminishing because of climate change, were listed as
threatened in 2008.
While polar bears normally eat seals they hunt from the sea ice, it
appears likely that this bear was scavenging on dead birds and
ingested the influenza virus that way, Gerlach said. Numerous birds on
the North Slope of various species have died from this avian
influenza, according to the Department of Environmental Conservation.
However, the bear need not have directly eaten an infected bird to
have become sick, Gerlach said.
“If a bird dies of this, especially if it’s kept in a cold
environment, the virus can be maintained for a while in the
environment,” he said.
The polar bear death is a sign of the unusually persistent and lethal
hold that this strain of highly pathogenic avian influenza has on wild
animal populations 2 years after it arrived in North America,
officials said.
“What we’re dealing with now is a scenario that we haven’t dealt with
in the past. And so there’s no manual,” said Andy Ramey, a US
Geological Survey wildlife geneticist and avian influenza expert.
Highly pathogenic avian influenza is called that because it spreads
rapidly in flocks of domestic poultry, often requiring massive culls
to control the contagions. Such outbreaks have been of concern in the
past because of their economic consequences for global agriculture.
Until recently, wild birds were afterthoughts. Though they were known
to carry the viruses, ferrying them between domestic poultry
populations, they were largely unaffected.
That has changed dramatically. The prior US outbreak of highly
pathogenic avian influenza, in 2014-15, resulted in some wild bird
infections, and some influenza-caused bird die-offs occurred in Europe
shortly thereafter. But the current version is considered
unprecedented in its effect on wild birds and other wildlife.
“Across North America, and really around the world, lots of wild birds
these days — I mean, thousands of wild birds these days, tens of
thousands in some cases — are dying because of these highly
pathogenic avian influenza viruses,” Ramey said.
The deaths are of particular concern when they occur in populations
that are already vulnerable, he said. An extreme example he cited is
the highly endangered California condors, with a population of just a
few hundred. After 21 influenza deaths were documented, federal
wildlife officials launched what promises to be a challenging
vaccination program in that population.
The disease has also killed a variety of mammals around the world.
In Alaska, 3 foxes, a black bear, and a brown bear have died from this
avian influenza. Elsewhere, more bears have been found dead after
being infected by the virus, along with skunks, raccoons, mountain
lions, and large numbers of seals in eastern Canada and off the coasts
of Maine and Washington state, as well as outside of North America.
The nation’s 1st detection of the disease in a squirrel was confirmed
earlier this month [December 2023] in an animal found in Arizona.
To Gerlach, the polar bear case was not surprising, considering that
black and brown bears have died. It is possible that more polar bears
succumbed to the disease, but in remote places out of the view of
people to record the events, he said.
“You’re really dependent on the public that’s out there, or the
wildlife biologists that are doing surveillance,” he said. Documenting
cases in any wild mammal population can be difficult, he added. “How
long is a carcass going to be in the wild before it gets scavenged or
eaten by something else?”
Aside from the large and wide-ranging death toll in the wild, the
current outbreak has some other differences, particularly its
durability, as seen in its persistence away from domestic flocks.
The virus that caused the 2014-15 outbreak spread in the wild bird
populations for a while, but it “sort of fizzled out,” Ramey said,
probably because it was eventually stamped out in poultry operations.
But this one continues to be maintained in the wild, as evidenced by
monitoring in Western Alaska, a place far from any big farms raising
chickens or turkeys, he said.
Gerlach gave the same assessment. “After the 2nd year, that all of
sudden disappeared,” he said of the 2014-15 version. “It didn’t stick
around, where this virus seems like it’s sticking around.”
Rather than winding down, it is continuing to spread across the world,
he noted, even into bird populations in Antarctica, as has been
recently documented. There are signs that it is now endemic in the
wild, a fixed feature into the foreseeable future, he said. If so,
“it’s not going to go away. It’s going to be here, and we have to have
some way to deal with it,” he said.
For Alaska, “a mixing area” for global bird migrations, spread of
avian diseases is always an issue, Gerlach said. “Alaska is a catchall
area for birds from North America or the Americas, as well as from
Asia,” he said.
The highly pathogenic avian influenza of 2014 and 2015 was introduced
from Asia to North America by wild birds migrating through Alaska. The
current influenza is also crossing continents through Alaska, though
from multiple directions, Ramey’s research has found.
In a newly published study, Ramey and his research partners found what
is likely to have been 3 separate and independent introductions of
highly pathogenic avian influenza into Alaska last year [2022]. His
research, with colleagues from the USGS and other agencies, used
genetic analysis to trace one form of influenza to North America and 2
to Asia.
“To have 3 introductions in Western Alaska, 2 from East Asia and 1
from the Lower 48, I mean, we haven’t seen anything like that before,”
he said. “It really, I think, exemplifies how these viruses now are
clearly able to be maintained.”
That study examined birds harvested in the fall of 2022 by hunters in
the Izembek National Wildlife Refuge area at the southern tip of the
Alaska Peninsula. Ramey and his colleagues found only a tiny number of
hunted birds that were infected with the currently active highly
pathogenic influenza virus: out of 811 swab samples taken directly
from birds and another 199 samples from feces, the only harvested
birds identified as infected were 8 pintails, one cackling goose, and
one widgeon.
It can take months to get test results from samples, so what happened
to those harvested birds is unknown, he said. But their meat was safe
to eat as long as it was properly cooked to the recommended 165 deg F
[74 deg C], he said. “Heat is remarkably good at deactivating
viruses,” he said. Along with the cooking advice, there are other
longstanding recommendations about safely handling hunted birds, such
as regular handwashing and avoidance of obviously sick animals.
There is little evidence that the current avian influenza wave poses
an infection risk to humans. Only a few cases have been documented in
the world, and those were general among people working with poultry.
For Alaskans dependent on wild game, this highly pathogenic influenza
poses a different type of risk: possible food-security problems. If
large numbers of birds wind up dying, that might mean less food on the
table in rural Alaska, Ramey and Gerlach said.
“Obviously, less birds could equate to less availability, and also
less resiliency in the population from things like disease, or climate
change, or toxins, et cetera, that could, in fact, impact these
populations of birds,” Ramey said.
Plenty of stressors already exist in wild populations, he said, “so
adding another threat to these populations isn’t doing them any
favors.”