A bird flu panzootic is sweeping the globe, impacting wild birds, poultry, and even some mammals on every continent except Australia. This devastating outbreak is driven by the H5N1 clade 2.3.4.4b strain of highly pathogenic avian influenza (HPAI). While Australia remains unaffected by this particular strain, the country is not entirely unscathed, with three separate strains of bird flu—H7N3, H7N9, and H7N8—detected across its poultry farms.
Australia’s national reference laboratory, the CSIRO’s Australian Centre for Disease Preparedness (ACDP), is at the forefront of testing and monitoring these strains. Dr Frank Wong, a senior research scientist at ACDP and a World Organisation for Animal Health (WOAH) Reference Laboratory expert in avian influenza, provided insights into the situation.
Bird flu viruses are classified as either low pathogenic avian influenza (LPAI) or high pathogenic avian influenza (HPAI). LPAI infections may cause mild illness or no disease at all in birds, while HPAI infections can result in severe disease and high mortality rates among poultry. Some H7 and H5 strains, though initially low pathogenic, can mutate and become highly pathogenic in infected chicken flocks.
The risk posed by HPAI viruses to humans is relatively low. According to Dr Wong, bird flu primarily affects birds, with occasional spillovers to other animal species. Human infections are rare and usually occur through direct contact with infected poultry. Transmission between humans or mammals is uncommon, maintaining a low risk to people at this time.
Australia has previously experienced outbreaks of HPAI in poultry in 2012, 2013, and 2020. Each outbreak was quickly contained and eradicated. These outbreaks involved H7 bird flu strains, and Australia has never faced an outbreak of H5N1, the strain causing global concern.
Currently, three H7 strains are responsible for bird flu outbreaks in Australia. Victoria has seen H7N3 and H7N9 strains affecting egg farms in Meredith and Terang regions, respectively. The H7N8 strain is impacting farmed chickens in the Hawkesbury region of NSW and the ACT.
Globally, the H5N1 clade 2.3.4.4b strain emerged in 2020 and has since spread to every continent except Australia. This strain affects millions of wild birds and domestic poultry, even reaching marine mammals in Antarctica. H5N1 has evolved to infect a broader variety of bird species and has mixed with local bird flu strains, allowing it to adapt to new environments and infect new bird species. It has also spilled over into mammals, including foxes, sea lions, elephant seals, and, on rare occasions, cats and dogs. In Europe, it has been detected in farmed minks and fur farms, and earlier this year, it was found in dairy cows in the USA.
Despite the global spread, the risk of H5N1 reaching Australia remains low. Migratory ducks and geese are the primary carriers of bird flu over long distances, and Australia is not in their migratory paths. However, H5N1’s ability to infect additional wild bird species slightly increases the risk of introduction through regional or bridging species.
To prepare for a potential incursion of H5N1, ACDP assists with Australia’s surveillance efforts and conducts research to characterise the virus. They track bird flu strains in poultry and wild birds in Australia, the region, and globally. State and territory laboratories rely on ACDP for testing bird samples to confirm avian influenza presence. Genetic sequencing of the virus helps identify the exact strain and understand its mutations. This information is crucial for determining whether a virus is local or introduced from overseas, and it informs authorities and animal health working groups for outbreak response.
Dr Wong’s role as a WOAH reference expert involves collaborating with other avian influenza experts worldwide. They share information about circulating strains and new spillover events, such as the H5N1 infections in dairy cattle in the US. This international cooperation enhances diagnostic capabilities and response strategies.
As the world grapples with this bird flu panzootic, Australia’s vigilance and preparedness efforts continue to safeguard its poultry industry and prevent the introduction of highly pathogenic strains like H5N1.
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A global bird flu panzootic, driven by H5N1, impacts all continents except Australia, which faces H7 strains. Australia's @CSIRO monitors & prepares for potential outbreaks to safeguard its poultry industry. 🦆🦠🇦🇺🔬🐔 #TheIndianSunhttps://t.co/uPlMi3WQRX
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