Black swans in ‘significant peril’ from bird flu
By Mike Foley
A deadly strain of bird flu could wipe out local populations of the iconic black swan, with the rapid spread of the virus in cattle and marine mammals ringing alarm bells for Australian experts.
Australia is battling an outbreak of the H7 strain of bird flu, which has promoted the mass culling of chickens in at least three states, leading to an egg shortage.
Native black swans are highly susceptible to H5N1 bird flu.Credit: Peter Rae.
But a more virulent strain, H5N1, is likely to be spread to Australia by migrating birds from Asia, experts warn, potentially as soon as this spring.
While H5N1 has been around for years, the virus has not yet spread to Australia. But it has now spread to every other continent, killing millions of wild birds, including even Antarctica, where it has killed thousands of Adelie penguins and skuas.
There is no evidence that H5N1 is likely to start a human pandemic, but the virus has started killing mammals in South America and has even spread among dairy herds in the US.
A study released last year in the journal Genome Biology last year sequenced the black swan genome and found “the black swan is extremely sensitive to highly pathogenic avian influenza”. The study said an outbreak in Australia would put black swans in “significant peril”.
One of the study’s authors, University of Queensland Professor Kirsty Short, said black swans were “incredibly susceptible” to the H5N1 virus.
“An outbreak would run the risk of making a lot of animals very, very vulnerable including species that are already on the vulnerable or endangered list,” Short said.
“What they’re seeing [in South America] is massive loss of wild bird populations, but also of marine mammals.
“Whether or not it would lead to an extinction, I don’t know. It would depend on where an outbreak was and how widespread it was.”
Short said Australia should be preparing for a wildlife outbreak.
“New Zealand has actually started vaccinating some of their rare species to try and protect them from H5N1 and the US did the same thing with some of their eagle populations.”
Invasive Species Council policy analyst Carol Booth said the evidence indicated black swans could be wiped out in certain areas.
“Recent research on black swans shows that they’re highly susceptible to bird flu, and we are potentially at risk of local extinctions when they are infected,” Booth said.
Federation University researcher Meagan Dewar said changes in the virus in 2021 made it more adaptable to wild birds, especially seabirds, which caused it to “take off”.
“That’s where we started to get this global pandemic in wildlife starting in the UK and Europe spreading down through South Africa and then also North America, South America, and then, unfortunately to Antarctica,” Dewar said.
“We don’t see high mortality rates in all species but definitely those that are getting infected have high mortality rates – birds like terns and gannets are highly susceptible around the world and faced massive mortality.”
Since late 2022, H5N1 has wiped out 30,000 South American sea lions, 17,000 southern elephant seal pups and unknown numbers of porpoises, dolphins and otters.
The mortality rate of elephant seal pups in Argentina’s Peninsula Valdes reached 95 per cent in 2023 compared with only 1 per cent in 2022.
Dewar said the science was not yet settled on how H5N1 was affecting mammal populations - with the possibility the seals were contracting the virus from birds, or eating dead birds.
Government experts suspect that bird flu is killing sea lions along Argentina’s entire Atlantic coastline, causing authorities to close many beaches in order to prevent the virus from spreading further.Credit: AP
Whatever the cause, the potential impact on Australia’s endangered sea lion populations is concerning, with only about 12,000 remaining.
Agriculture Minister Murray Watt, who is responsible for national biosecurity, announced a $7 million initiative to prepare for an H5N1 incursion, largely drawn from existing funds.
Watt said on Wednesday that a local outbreak was not inevitable, but “the chances of it coming to Australia are, of course, increased”.
The first outbreak of H5N1 virus in dairy cows in the US was reported in late March and has spread to 12 states so far. Experts think the virus may be spreading through consumption of raw milk. Twenty-six cats have been confirmed infected, with high mortality rates.
H5N1 hasn’t yet gained the ability to spread directly between people and just three people, all working with dairy cows, have been confirmed with H5N1 and symptoms have been mild, causing eye redness and a cough. The US Department of Health says pasteurisation kills most viruses in milk.
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