A great black-backed eagle that migrated from Europe to Eastern Canada last winter may be the first carrier of the deadly strain of avian influenza in North America, destroying millions of domesticated chickens and wild bird populations.
The widespread prevalence has given researchers a new opportunity to fine-tune their understanding of the disease by studying which species play a key role in the transmission, behavior and ecology of any wild bird.
Dr. Nicola Hill, an assistant professor of biology at Boston University in Massachusetts and lead author of a new paper on the subject, said, “Previous research on bird flu has included this large classification of wild and domesticated birds.”
But “wild birds are incredibly species-rich,” he said, “each of them has a unique natural history and behavior.”
Knowing which migratory species carries the pathogen, for example, can help predict when and where it may arrive based on the migration route.
Following the arrival of the migrating gall coast, the highly pathogenic avian influenza, also known as the H5N1 virus, spread across North America. More than 77 million poultry, raised in the most populous environments that fuel the spread and evolution of the virus, have been killed in dozens of countries.
For some experts, the damage caused by this H5N1 strain on wild birds – it has hit more than 100 species so far – is alarming and unprecedented in its depth and breadth. Among wild birds, the spread can be very difficult to contain, which poses a major threat of spillover to other wildlife. And some wild bird species, such as storks and some marine birds, are particularly vulnerable, especially those with low breeding rates and those already endangered.
The World Organization for Animal Health estimates that more than 383,000 wild bird deaths from October 2021 could be attributed to the virus, although the number could be a huge undervalue due to how difficult it is to track sick and dead birds.
At a much higher rate than the last outbreak in 2014-2015, the pathogen spread rapidly through different regions and species.
“This is affecting a wider host range and it doesn’t end up in the wild as before,” said Dr. Hill. “It survives among wild birds and is a frightening possibility. For many of us in this case, O God, what do we do when we are scattered among a wild animal for which there is no control?
It has long been assumed that the primary hosts of avian flu are dubbing ducks, such as mallards, teal and shovellers, which feed on the surface and just below them with their rump in the air. They are critical for spreading because they have no light or symptoms and they carry it far and wide. New research, however, has shown that other birds, such as geese, play an underestimated role due to their natural history.
“Giz is a little more tolerant in human-infested areas,” said Dr. Hill. “Imagine a commercial poultry operation or backyard operation where they scatter grain around.” It “attracts geese and other scavenging birds, such as roses and crows and magpies, so they have an interface between them,” he said.
The unique natural history of black-backed roses, for example, plays a role in infection. “Roses were a very rare host for a very rare virus,” said Dr. Hill. “When they carried it, those rare occasions, they spread it really fast. There’s nothing like roses for the rapid spread of the virus and for really long distances. They’ll catch a tail wind and cross the Atlantic in 24 hours.”
The study could help other researchers track not only the continued spread of this year’s pathogens, but also the pathways taken by other viruses that are harmful to wildlife.
Jonathan Runstadler, professor and chairman of the department, said: “Roses, geese and ducks are a major contributor to understanding how the virus is expected to spread in a more precise way or to finally model it. He is a co-author of Infectious Diseases and Global Health and research papers at Tufts University’s Cummings School of Veterinary Medicine.
“The data allows us to predict whether a virus is emerging, when that bird could enter North America, and we can look at a bird population to monitor for detection,” said Dr. Runstadler.
The origin of this year’s highly pathogenic lineage of avian flu was first found in 1996, in a domesticated goose in China. It has since been propagated around the world among wild and domesticated birds, evolving as it travels from host to host.
In 2005, a decade after the evolution, the strain caused a major outbreak of wild birds in wetlands in China.
The strain was first seen in the United States in 2014, with migratory birds traveling from Eurasia across the Pacific to Alaska and further east, causing outbreaks on U.S. poultry farms that killed 40 million turkeys and chickens.
After it reached the Midwest, however, mass killings stopped it, spreading the virus to both wild and domestic populations.
“We don’t have a vaccine,” said Dr. Hill. “All we have in our tool kit is the swap of all our chickens, which is terrible, but at least somewhat successful.”
But killing infected chickens did not work at this time, as the virus has been able to find a home in so many wild birds, giving rise to the largest outbreak of avian influenza.
In some places, officials are warning chicken breeders and even those who keep their flocks in the backyard to keep their birds indoors, while elsewhere, the threat seems to have subsided.
“This virus is very good because it frequently ping-pong between wild and domesticated animals,” said Dr. Hill. “There is no better way to spread the virus than to take a wild reservoir and domesticate a close relative. This is exactly what we did with the chickens and ducks. The most pathogenic form of the virus occurs when the virus enters farm animals. “
In the Magdalen Islands of Quebec, wildlife officials have recently discovered the bodies of thousands of white gannets that have been wiped out by the flu.
There is no way to predict whether the flu outbreak will decrease or worsen.
Some species, such as raptors, seabirds, and shorebirds, are at risk of contracting the virus because of their behavior. Dozens of bald eagles are known to have died of the flu, mainly because they prey on ducks and other birds that carry the germs.
Birds that gather in large numbers are also at risk. “There are many flocks of birds – shorebirds, terns and seabirds – that form huge, huge groups and this could be a field day for the virus,” said Dr. Hill.
The extent of extinction of different species is difficult to quantify, as there is a lack of surveillance. Better tracking on migration routes will help experts figure out ways to reduce the spread of the virus.
Large numbers of shearwater and other species of seabirds have been reported off the Atlantic coast in Massachusetts, Maine, New Hampshire and Connecticut. Avian flu is a suspicion, although tests have not confirmed it.
Andy Ramey, a wildlife geneticist at the U.S. Geological Survey of Alaska, said, “The geographical range of identification, the number of species we are getting through identification, the amount of disease we see in wild birds are all unprecedented.” Those who study avian influenza. “It’s an unknown territory and it’s hard to know what to expect.”
There are further concerns that for many species during this breeding season, parents may pass the disease on to offspring who have underdeveloped immune systems. Young wild birds are often exposed to low-pathogenic viruses, which can act as common and almost inoculation, helping to strengthen their immune systems.
An endangered species is being monitored in Bouzard’s Bay off the coast of Massachusetts. Tests are still ongoing, and no sick birds have been found yet.
“It’s going to be a rough food year for Tern,” said Caroline Mostello, a coastal bird biologist at the Massachusetts Division of Fisheries and Wildlife. “Nesting has slowed down. Hopefully we don’t have a combination of poor food resources and avian flu; which can work together to really hurt people.”
Experts say avian flu poses a very low risk to humans and so far only two people have been diagnosed with it. However, as it continues and evolves, it can acquire the potential to pose a serious threat of spillover in humans.
Dr Hill said a major obstacle to better understanding the outbreak was the lack of funding for efforts to track the spread. “Surveillance is really, really, really bad,” he said. “We’re spending very little money and time on it.”