Avian influenza viruses (AIVs) are found worldwide in domestic and wild birds, sometimes causing disease in gallinaceous poultry and other species. Surveillance of wild bird reservoirs provides an opportunity to better understand the epidemiology of AIVs. Given Australia’s isolation both geographically and ecologically, the epidemiology of AIV is expected to be different from other geographic regions.
In 2006, Australia established the National Avian Influenza Wild Bird Surveillance Program as a collaborative project involving a range of government and non-government organisations. The program allows national coordination of surveillance activities and collation of data to further the understanding of AIV epidemiology in Australia. Surveillance is conducted Australia-wide, and includes i) pathogen-specific, risk-based surveillance via convenience sampling of apparently healthy, live and hunter-killed wild birds, and ii) enhanced passive surveillance via investigation of significant, unexplained morbidity and mortality events in wild birds.
Between July 2005 and June 2014, over 80,000 samples were collected from healthy live or hunter-killed wild birds and over 1700 wild bird morbidity and mortality events were reported.
No highly pathogenic avian influenzas (HPAI) were identified, but a wide range of low pathogenic avian influenza (LPAI) subtypes were found in Australian wild birds, including H5 and H7 subtypes. LPAI H5 subtypes were found to be more common and widespread than H7 subtypes, despite all previous HPAI outbreaks in Australia poultry being caused by HPAI H7 subtypes. Phylogenetic analysis has shown Australian AIVs typically form separate sub-clades of the Eurasian avian influenza lineage, with infrequent introductions of North America lineages. The dynamics of Australian wild bird AIVs are complicated and associated more with large scale rainfall patterns than simple seasonal patterns.
The NAIWB surveillance program continues to maintain AIV sampling and diagnostic capability and capacity in Australia and inform risk assessment and decision making that may benefit the Australia poultry industry.