‘We’ve never encountered a virus like this’: Could wet ducks be the link in the spread of avian influenza?

Hundreds of seabirds found dead on the coast of Africa. Discover the remains of endangered condors in California. Dozens of dead Canada geese removed from Markham Park.

Worldwide, the highly pathogenic H5N1 avian influenza strain is killing wild birds in numbers never before seen.

“This strain is unfortunately severely affecting wild birds, and many, many species are getting very sick and dying from this virus,” said Brian Stephens, a wildlife disease specialist with the Ontario and Nunavut chapter of the Canadian Wildlife Health Association, a science group. Experts who monitor the health of wildlife.

“It is very different from most other avian influenza viruses that we have come across.”

The current outbreak of bird flu, which began in Europe in 2020 and reached North America a year later, is said to be one of the largest in history.

It is estimated that 200 million birds have died worldwide.

In Canada, the virus has killed an estimated 46,000 wild birds since monitoring began here in December 2021, though many of the deaths likely went undetected, said Christopher Sharp, a population management biologist with the Canadian Wildlife Service, who is Branch of Environment and Climate Change Canada. .

Color electron micrographs of transduction of avian influenza A H5N1 viruses (shown in gold) cultured in MDCK cells (shown in green) as shown in this published undated image.

Wild birds pick up the virus from other birds when they migrate in large numbers, but they don’t usually die from it.

“The main difference from previous outbreaks is that HPAI spreads widely in wild birds,” Sharp said in an email. “In addition, the current virus has resulted in a much greater mortality rate in wild birds than was the case previously.”

He said the impact of the virus could be reduced somewhat this year, as it has now been circulating for a year, which could give wild birds some immunity. It’s possible that there could be infection in young birds that haven’t encountered the virus before, or in older birds whose immunity has wane over time, Sharp said.

Canada has had outbreaks of HPAI before.

But in the past, the virus was more dangerous to poultry, spreading through contact with wild birds or indirectly through feces, contaminated water, soil and feed, according to the Canadian Food Inspection Agency, which monitors the virus on farms.

The agency said it “could have serious consequences”. “Millions of chickens were culled on farms in Canada last year to stop the spread of the virus, which attacks the intestinal and respiratory tract of animals and spreads rapidly among chickens and turkeys and is much more deadly.”

A photo taken from November 24, 2022 of a pelican, which is suspected to have died from infection with the H5N1 avian influenza virus, on a beach in Lima, Peru.

Nearly 7.5 million chickens have been affected in the current outbreak, according to the Canadian Food Inspection Agency, although the number of affected poultry this year is down by more than a third compared to the same time period last year.

However, the federal agency notes that Canada is still in the middle of its spring migration period, which lasts into June.

“This means that there is still a possibility that the number of affected birds will increase in the coming months,” the agency said. “It is important to note that the sustained response is unique in the number of detections, the geographic distribution of the outbreak, and its long duration, which extended beyond typical migration periods.”

Avian influenza viruses, like the human influenza virus, mutate and change, Stephens said.

“It is assumed that this virus will change at some point and that will reduce virulence,” Stevens said. “And it will be taken over by another strain of the virus which will then pass into the population and hopefully not a severe stressor.

But like I said, we haven’t come across a virus like this,” he said, which sticks around in wild populations for as long as it’s around.

“So I don’t know when that will happen or how long we’ll be around. But it should lessen sometime in the future and we won’t have to worry about it as much.”

Scientists do not know the rate at which the virus kills wild birds because they do not know how many are infected.

For example, more Canadian geese died in the GTA this year than last year, including hundreds of dead geese removed from Markham Park this spring. The city hired a contractor to collect birds that were brought to the landfill and incinerated.

“Canadian geese seem to be more susceptible,” Stephens said. “We have people call us and say a bunch of Canada geese died from this. But there seem to be 50 others in the pond that are fine.

“So we don’t know exactly how allergic Canada geese are,” Stevens said. “But because they are in gardens where people see them, they are more reported to us than many other species.”

There is no evidence that geese are pregnant. Instead, scientists believe that wet ducks such as mallard ducks are the carrier, as they do not appear to be symptomatic or die from infection.

“This makes them more likely to be a key species group for moving the virus around in the ground,” Sharp said.

But the strain did kill other species including snow geese, tundra swans and trumpeter swans. Scavenger birds that feed on the remains have also fallen prey to the virus, Stevens said, including bald eagles, red-tailed hawks, great horned owls, turkey vultures and crows.

In May, the Canadian Wildlife Health Association diagnosed the death of Ontario’s first mammal, the red fox population.

Across the country, the virus has been found in 110 mammals across 10 species, including scavenging species such as red fox, striped skunk and mink, as well as in opportunistic marine mammals such as harbor seals and Atlantic white dolphins, accordingly. for mustache.

Mammals infected with HPAI have been found in all provinces and territories, except for New Brunswick, the Northwest Territories and Nunavut, he said.

It is very rare for the virus to infect humans or pets for that matter, although a local dog in Canada was confirmed to have died in April of this year from the virus.

Pet owners are advised to keep cats indoors and dogs on a leash to limit contact with wild birds or potentially infected carcasses, and to reduce exposure to outdoor environments such as ponds where birds congregate. Pets should not be given any raw meat from fowl or poultry. People should not feed or handle any wild bird by hand.

The Canadian Food Inspection Agency said dead, injured or sick birds should be reported immediately to the relevant provincial or territorial authorities, the Wilderness Canada Health Collaborative Information Line at 1-800-567-2033 or using its online reporting tool.

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    (tags to translation) Avian Influenza 

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