Highly pathogenic avian influenza - HPAI
Five outbreaks of HPAI occurred in Australia between 1976 and 1997. HPAI viruses caused clinical disease in commercial poultry in Victoria in 1976 (H7N7), 1985 (H7N7) and 1992 (H7N3), in Queensland in 1994 (H7N3), and in New South Wales in 1997 (H7N4). Each time, there was severe disease in affected chicken flocks. All had obvious or circumstantial evidence of contact with wild waterfowl or surface water contaminated by wild waterfowl, or an association with free-range farmed ducks. There is some evidence that, initially, low pathogenic avian influenza (LPAI) may have been involved in the outbreaks in 1976,1992 (Victorian Department of Agriculture, pers comm) and 1997 (Selleck et al 2003).
In November 2012, an HPAI H7N7 virus was detected in a New South Wales free-range chicken layer flock of 50,000 in the Hunter Valley. The property had a range of dams that attracted wild ducks.
In October 2013, an HPAI H7N2 virus was detected in a free-range and cage bird layer flock of 400,000 near Young.
Low pathogenic avian influenza (LPAI) (H5/H7)
Only three detections of LPAI H5 and H7 virus strains have been recorded in Australian domestic poultry:
- LPAI (H7N7) was isolated on a duck farm during investigation of an HPAI (H7N7) outbreak in chickens in Victoria in 1976. The ducks showed no signs of clinical disease.
- Antibodies to H5, H7 and other subtypes of AI viruses were detected in commercial domestic ducks during investigation of an HPAI (H7N3) outbreak in chickens in Victoria in 1992.
- LPAI (H5) antibodies were detected on a Tasmanian noncommercial, multispecies smallholding in 2006
- An LPNAI (H5N3) virus was detected in a free-range duck flock in Victoria during routine surveillance in 2012. The source of the virus could not be determined, but it is speculated that the primary source may have been wild birds, which were freely able to access the range area.
Low pathogenic avian influenza (LPAI) (not H5/H7)
The following LPAI (not H5/H7) detections have been made:
- Antibodies to LPAI H1, H4, H5, H7 and H9 subtypes were detected in ducks on a farm in Victoria in 1992.
- LPAI (H4N8) was detected on a multi-age, commercial duck farm in Victoria in 1994.
- LPAI (H6N4) was isolated from a single duck on a property in Queensland in 2006.
- Chickens in several sheds from a property in New South Wales tested seropositive to LPAI (H6N4) in 2006.
- LPAI H10N7 was detected in 2010 in a chicken farm in New South Wales, where transmission to abattoir workers during the processing of the poultry was documented.
- An LPNAI H5N3 virus was detected in a free-range duck flock in Victoria during routine surveillance in 2012. The source of the virus could not been determined, but it is speculated that the primary source may have been wild birds, since wild birds were freely able to access the range area.
- In April 2012, LPAI H9N2 was confirmed on a turkey farm housing about 26,500 turkeys in three sheds near the Hunter Valley in New South Wales; the source of the infection is unknown.
- In 2012, LPAI H4N6 virus was found in ducks of several age groups on a multi-age farm of 2,400 ducks located on the north coast of New South Wales.
- In 2012, an LPAI H10N7 virus was detected in a Queensland poultry flock; the source of the infection is unknown, but it is likely that the primary source may have been wild birds.
Avian influenza is potentially a serious human disease. Human illness and deaths have been confirmed in other countries in people who had close contact with the H5N1 infected chickens or their environment. There is no evidence of human-to-human spread. To date all human infections appear to have been transmitted from infected birds.