Professor Stephen Walkden-Brown, Interim Director of the UNE-based Poultry Hub Australia believes Australia is well positioned to manage the threat.
“If it were to take hold in commercial flocks and native bird populations, the virus would undoubtedly have a devastating impact,” he said. “It would be difficult to control and the cost to the poultry industry and government would be very high. However, a robust response plan to prevent that happening has swung into action and we should have confidence in Australia’s emergency animal disease measures.”
The H5N1 strain of bird flu that has caused mass deaths of poultry, wild birds and marine mammals globally has been confirmed in eight dead migratory seabirds found along Australia’s coastline. They represent the first detections on our continent.
And while there are fears the virus could erupt like wildfire in our natural environment and spread to commercial poultry operations, Professor Walkden-Brown said the successful containment of other strains of highly pathogenic avian influenza in Australia in recent years give cause for some optimism.
“Experience tells us that outbreaks of avian flu in poultry start with the first or index case detected on a particular farm. While it’s awful for that individual producer and potentially their neighbours, local eradication of hosts (chickens), coupled with containment lines, quarantine and movement restrictions, are often enough to keep the outbreak geographically contained. During outbreaks of related highly pathogenic avian influenza viruses over the past 10-15 years, mostly in Victoria and New South Wales, the consequences have been able to be localised with ultimate eradication of the virus from chickens.
“We have a good disease surveillance and biosecurity track record, and I think a reasonable scenario is that we will be able to snuff out this virus early if it gets into a poultry farm”.
A key aspect in this scenario is early detection and identification of infection to enable rapid detection of the index case before widespread undetected transmission occurs. Professor Walkden-Brown said the poultry industry is aware of this and is working closely with regulatory authorities to facilitate early detection.
Although the H5N1 virus is highly pathogenic (capable of causing severe disease or death) and can infect a wide range of hosts, it cannot multiply outside of host animals, which are the main reservoir of infection. When the virus is detected in a poultry flock, this means that host animals must be euthanised and the site decontaminated.
So far, migratory seabirds infected with the virus have been found on coastal areas relatively distant from significant commercial poultry flocks. However, the wide host range of the current H5N1 strain means there is a risk of the virus spreading to wildlife species that reside permanently, or for long periods in Australia. The main threat to the poultry industry would likely arise from such transmission to Australian host species, particularly birds, which could then transmit it to poultry, putting the free-range sector at particular risk.
“The industry already works hard to limit contact between wild birds and poultry, and these efforts would be increased should the virus be detected in Australian wildlife,” Professor Walkden-Brown said. “Obviously detection and control of the disease in wildlife populations poses a far greater challenge than the situation in poultry that are contained and under human control.”
Australia faces three key scenarios:
- The H5N1 strain never establishes in Australian wildlife and remains a threat based on infection in migratory species only.
- The virus spreads to wildlife but improved biosecurity keeps it at bay from the poultry industry.
- The virus spreads to the poultry industry, testing the systems developed to control highly pathogenic bird flu viruses in the past. In this scenario, mass vaccination is unlikely unless the virus spreads more widely within the industry.
“It’s important for us all to be alert but not alarmist,” said Professor Walkden-Brown. “Concerns about the impact on domestic and export markets and so on are speculative at this stage, and are dependent on which way the outbreak develops.”
It remains critically important for members of the public to immediately report sightings of sick or dead poultry, wild birds or wildlife to the Emergency Animal Disease Hotline (or 1800 675 888). High-risk native bird species include birds of prey like hawks, owls and eagles that can feed on infected animals. Penguins or pelicans, black swans, and seals, sea lions and dolphins are also considered at risk.
“Every dead animal that is found, reported and tested serves two purposes,” Professor Walkden-Brown said. “Its safe recovery and disposal removes a potential source of the virus and, secondly, its location adds to the epidemiological picture of what is happening around the country.”
