Investigation of poultry illness and deaths in Victoria, in May-June 2024, and in NSW in June 2024, has detected several different high pathogenicity avian influenza (HPAI) H7 viruses - H7N3 and H7N9 in Victoria, and H7N8 in NSW.
See: agriculture.vic.gov.au/biosecurity/animal-diseases/poultry-diseases/avian-influenza-bird-flu and www.dpi.nsw.gov.au/animals-and-livestock/poultry-and-birds/health-disease/avian-influenza.
The outbreaks in Victoria and NSW are not related to each other. These strains are also different from the HPAI H5 strain (strain “2.3.4.4b”) that is currently impacting wildlife and poultry overseas, which has not yet reached Oceania, including Australia and New Zealand.
Avian influenza virus strains are described as low pathogenicity (LPAI) or high pathogenicity (HPAI) and refer to the pathogenicity of the strain in poultry. Worldwide, including in Australia, LPAI viruses are naturally carried by wild birds, usually waterfowl such as ducks, without causing or showing signs of disease.
LPAI viruses can spillover to poultry from local wild birds. The virus can then subsequently mutate from LPAI virus to HPAI virus during circulation within poultry, which is a well-documented occurrence.
The CSIRO Australian Centre for Disease Preparedness’s (ACDP) analysis of the Victorian samples has found the H7N9 and H7N3 HPAI strains are closely related to LPAI viruses recently detected in wild bird samples in Australia, identified through the National Avian Influenza Wild Bird surveillance program.
Worldwide, HPAI H7 viruses are rarely detected in wild birds. There have been no reports of mass wild bird deaths, nor any detections of HPAI in wild birds in Australia. A process for enhanced wild bird surveillance has been developed, and monitoring of wild bird populations will continue. Investigation of the source of the NSW outbreak is underway.
Before the current 2024 outbreaks, there had been eight other outbreaks due to HPAI viruses in Australian poultry since 1976, all of which were the H7 strain. The previous eight outbreaks were all successfully eradicated.
Wildlife Health Australia (WHA) provides support to the National Avian Influenza Wild Bird (NAIWB) Steering Group and manages and collates avian influenza (AI) surveillance data from wild birds sampled across Australia by jurisdictional biosecurity agencies, universities and the Australian Government Department of Agriculture, Fisheries and Forestry’s Northern Australia Quarantine Strategy. Confirmatory testing occurs at the ACDP.
Targeted surveillance efforts for AI continue to focus on sampling from waterfowl and shorebirds, specifically from locations where there is known mixing of waterfowl with shorebirds and where waterfowl are in close proximity to poultry and humans.
General surveillance across Australia is also undertaken and focuses on the exclusion of avian influenza from wild bird death and disease events.
Targeted surveillance activities continue to show presence of a wide range of LPAI virus strains in Australian wild birds. With over 140,000 of these tests having been undertaken for avian influenza, no HPAI viruses have been identified in Australian wild birds.
WHA and the NAIWB steering group prepare regular publications on wild bird avian influenza surveillance results generated via the NAIWB Surveillance Program and National Wildlife Health Surveillance System.
Detailed analysis of avian influenza viruses detected in wild birds through the NAIWB program contributes to tracking Australian virus evolution and dynamics, supports maintenance of testing programs, and contributes to a virus sequence library the enables comparison of Australian and overseas strains.
Any unusual illness or death in wild birds should be reported via the Emergency Animal Disease Hotline on 1800 675 888. Reporting will alert authorities to the event so they can evaluate the need for investigation. Further information is available at: https://wildlifehealthaustralia.com.au/Incidents/Incident-Information/category/high-pathogenicity-avian-influenza.
Photo © Michelle Wille