Deadly bird flu found to spread between mammals, raising risk to Australian sea lions, seals and dolphins

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The Invasive Species Council, the Australian Marine Conservation Society and the Biodiversity Council are calling on Australia’s governments to urgently and collaboratively ramp up preparations for bird flu in wildlife, as new research provides the first strong evidence of mammal-to-mammal transmission of the deadly H5N1 strain.

The research finds evidence of a newly evolved bird flu strain causing ‘unprecedented’ mass deaths of elephant seals and sea lions since it reached South America and spread from north to south within six months.

Dr Carol Booth, Invasive Species Council Principal Policy Analyst, said:

‘The rapid adaptation of this virus to mammals means the consequences for Australian wildlife could be even more catastrophic than predicted if H5N1 arrives in Australia.

‘Since arriving in South America in late 2022, bird flu has killed more than 30,000 South American sea lions, 17,000 southern elephant seal pups and unknown numbers of porpoises, dolphins and otters, as well as at least 650,000 native birds.

‘The mortality rate of elephant seal pups in Argentina’s Península Valdés reached 95% in 2023 compared to only 1% in 2022.

‘If high pathogenicity bird flu turns up in Australia, the government-commssioned risk assessment predicts ‘catastrophic’ impacts on our native birds.

‘That risk assessment predicted only minor impacts on marine mammals, but the latest research implies the risk to Australian mammals is now much higher.’

Alexia Wellbelove, Australian Marine Conservation Society Campaign Manager – Fisheries & Threatened Species said:

‘The potential consequences of bird flu for Australia’s marine mammals are frightening.

‘Australia’s endemic sea lions are already endangered, with only about 12,000 remaining – far fewer than the 30,000 sea lions killed in South America.

‘This killer disease has also been wiping out millions of birds around the world, including penguins in Antarctica. Our native birds will face a similar fate if the disease reaches Australia.

‘As the last continent free of this deadly virus, Australia has the opportunity to prepare so as to be able to quickly detect and respond to outbreaks in wildlife.’

Biodiversity Councillor Professor of wildlife conservation John Woinarski (Charles Darwin University) said:

‘This new research further documents the rapid and extensive spread of H5N1 bird flu globally and also provides compelling evidence that mammal-to-mammal transmission is occurring.

‘The consequences of this aggressive bird flu strain are alarming with extraordinarily high rates of mortality causing crashes in the populations of many different species.

‘Australia has been lucky to date, but we can’t presume this will continue. I fear the impact on many of our native animal species. Some species may not survive such rapid and dramatic losses.’

Dr Carol Booth added:

‘Although much work has been done by Wildlife Health Australia to prepare resources for decision-makers and wildlife managers, with mitigation toolboxes outlining response options, an effective response needs much more.

‘This should include a national taskforce to drive implementation and collaboration between governments and with key non-government response partners like threatened species recovery teams, wildlife disease and conservation experts, zoos, aviaries and wildlife carers.

‘Implementation thus far has been patchy, particularly on the critical recommendation by Wildlife Health Australia to develop site-specific and population-specific risk mitigation plans.

‘To inform preparations, we recommend the federal government update the July 2023 assessment of risk, taking into account the new evidence of mammal-to-mammal transmission and the outbreaks in Antarctica.

‘The public should report any unusual bird deaths immediately by calling the Emergency Animal Disease Hotline on 1800 675 888.’


Key points from new scientific paper – Massive outbreak of Influenza A H5N1 in elephant seals at Península Valdés, Argentina: increased evidence for mammal-to-mammal transmission

  • The paper shows strong evidence that a new clade of H5N1 avian influenza has evolved to spread between mammals, not just from birds to mammals.
  • This has led to massive deaths of seals and sea lions in South America.
  • This is the first strong evidence (genetic and epidemiological) of bird flu virus transmission between mammals.
  • It appears that H5N1 jumped at least 3 times from wild birds to marine mammals on the Pacific coast of South America, and then evolved to spread between elephant seals. It may have then jumped back to birds.
  • There are growing concerns that H5N1 viruses adapted to mammalian transmission could facilitate host-jumps to other species, including humans. So far, the risks to humans are regarded as low.
  • An H5N1 strain from a human case in Chile (of the marine mammal clade) was shown to be transmissible between co-housed ferrets
  • Details of loss of marine mammals in South America: >17,000 elephant seal pups (plus unknown number of adults) at just one Argentinian site. >30,000 sea lions in Peru and Chile plus dolphins, otters and over 650,000 seabirds.

Additional recommendations

  • The Invasive Species Council has developed a comprehensive set of recommendations to the Australian Government to prepare for the arrival of high pathogenicity avian influenza H5N1 in wildlife populations. Recommendations include:
    • establishment of a national taskforce
    • development of a national wildlife response plan
    • increased surveillance in wild bird populations, including collaboration with indigenous rangers, birdwatchers, land managers and researchers, particularly in remote locations.
    • provision of resources to assist in the preparation of local response plans for managers of sites with high concentrations of shorebirds, waterbirds or seabirds.
  • Longer term, Australia needs more effective national arrangements for responding to  national wildlife emergencies. Under Australia’s national environmental law (the EPBC Act) we have a threat abatement system and national plans for addressing major chronic threats such as feral cats and pigs but we don’t have a national system for addressing rapidly emerging new threats (except if they can be eradicated – e.g. fire ants). This is one of many reforms needed for our national environmental laws to become fit for purpose.
  • Research shows removing and disposing of dead birds can help stop the spread

Australian H5N1 bird flu risk assessment

  • The Australian Government commissioned a risk assessment of High Pathogenicity Avian Influenza (HPAI) which was released in July 2023.
  • The assessment found that the risk of ‘HPAI virus exposure and establishment in resident wild birds’ is ‘moderate/high’ and that the impact of this would be ‘catastrophic’, leading to an overall risk of ‘high’.
  • Some key findings from this assessment include:
    • Extrapolating from global outbreaks of HPAI H5N1 clade, there are likely to be significant consequences associated with incursion and establishment of HPAI in Australia via wild birds given a moderate likelihood of incursions.
    • The frequency of HPAI incursions into Australia via wild birds may be significantly lower compared with other continents and as a result, containment of outbreaks may be more achievable in the Australian context if they are identified early.
    • Consequences to wild birds are assessed as CATASTROPHIC with moderate uncertainty, consequences to poultry are assessed as HIGH with moderate uncertainty and consequences to wild mammals are assessed as MINOR with moderate uncertainty.
    • In multiple outbreaks the scale of mortality has been extremely high, often involving deaths of 100s, 1,000s or 10,000s of individuals with significant proportions of birds, resulting in mortality globally estimated to be in the millions.
    • The Australian black swan has recently been determined to be highly susceptible.

Impacts overseas

  • From Oct 2021-April 2023, more than 335 species of wild birds were impacted in 8,403 reported wild bird outbreaks globally.
  • Since arriving in South America in late 2022, bird flu has killed more than 30,000 South American sea lions, 17,000 southern elephant seal pups and unknown numbers of porpoises, dolphins and otters, as well as at least 650,000 native birds.
  • The mortality rate of elephant seal pups in Argentina’s Península Valdés reached 95% in 2023 compared to only 1% in 2022.
  • Mass mortality events have been observed in penguins and skuas since bird flu arrived in Antarctica in early 2024. The virus arrived at the end of the breeding season for birds and mammals, so even greater impact is expected in the warmer months.
  • In the UK, H5N1 has wiped out about 30% of the country’s breeding population of roseate terns, great skua and gannets.
  • Since 2020, there have been outbreaks in Asia, Europe, the Middle East, Africa, North America, South America and Antarctica – Australia remains the only continent free of high pathogenicity avian influenza.
  • Humans and other mammals can become infected through contact with live or dead infected animals, or contaminated environments. Current strains of avian influenza do not appear to transmit between humans.

What to look out for

  • The public should report any unusual bird deaths immediately by calling the Emergency Animal Disease Hotline on 1800 675 888.
  • Wildlife Health Australia have produced detailed advice for people who encounter sick or dead wild birds.
  • Look for:
    • Small groups or clusters (5 or more) of sick or dead wild birds of any species.
    • Individual or less than 5 sick or dead wild seabirds, waterbirds, shorebirds or birds of prey (e.g. eagles, hawks)
  • Infected live birds may show a wide range of signs if they are sick, including:
    • lack of coordination, tremors, swimming in circles
    • twisted necks or other unusual posture
    • inability to stand or fly
    • diarrhoea
    • difficulty breathing, coughing or sneezing
    • swelling around the head, neck and eyes
    • cloudiness or change in colour of the eyes.

About the Invasive Species Council

The Invasive Species Council campaigns for stronger laws, policies and programs to protect Australia’s native plants and animals from environmental weeds, feral animals and other invaders.

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