University of Otago evolutionary virologist Prof Jemma Geoghegan said testing to date indicated the outbreak of the highly pathogenic H7N6 strain of bird flu recently confirmed at Mainland Poultry’s Hillgrove farm, near Moeraki, had been contained.
However, the Ministry for Primary Industries’ (MPI) newly established regional control centre, in Dunedin, would be required for ongoing testing, Prof Geoghegan said.
"To stamp this out, they’ll need to do a lot more testing of chicken farms around the area.
"And it’ll be really reassuring for the industry, at least."
MPI said yesterday tests on a second, smaller egg-producing poultry farm near Dunedin had come back negative.
In a statement, Biosecurity New Zealand deputy director-general Stuart Anderson said multiple samples had been taken from the farm and if the highly pathogenic H7N6 strain were present it would have been found in most of them — "but we haven’t found any".
Mr Anderson said the precautionary restrictions, placed on the smaller property on Tuesday, would stay in place while further testing was carried out to determine why birds there were getting sick.
But it was believed to be due to an existing disease among the birds.
The culling of 80,000 chickens continued at Mainland Poultry’s Hillgrove farm, which also remained under strict controls.
But there had been no signs of production loss or sick birds at Mainland Poultry’s five other properties in the area, he said.
Prof Geoghegan said the "H7 subtypes" of bird flu had been found in New Zealand’s mallard ducks, for example, through surveillance over the last 20 years or so.
"So that’s not the worrying part. The concerning part is when this virus spills over to poultry.
"When it gets to chickens, it has to adapt to spread between chickens, which are different from wild birds, and the way it does that is it mutates genetically.
"And when it does that and it achieves the ability to spread between chickens, it’s the genetic mutations that the virus acquires to do that that allows the virus to spread into lots of different cell types in the chicken.
"So it basically can infect loads of different organs and tissue types and so on.
"It becomes really pathogenic, which means that it causes really, really severe disease."
Outbreaks such as the one at Moeraki happened around the world and in many cases 100% of the infected chickens died, she said.
However, a more sinister strain of bird flu had been a global concern since 2021, she said.
What happened there was that the strain H5N1 was low pathogenic in wild birds but it too spilled over to poultry, and became highly pathogenic.
"Then it spilled back into wildlife," Prof Geoghegan said.
That strain of bird flu then killed a range of animals around the world, and spread into cattle and humans.
And there was "always the possibility" it could happen again.
"The problem is that it’s more likely to happen if it’s not really contained."
Despite that being a "very worrying possibility", it was also unlikely in this situation, she said.
However, the Department of Conservation (Doc) this week asked the public to report groups of three or more sick or dead birds, marine mammals or other wildlife to the exotic pest and disease hotline.
Doc biosecurity manager Clare Stringer said the department was working with MPI, the Ministry of Health and Te Whatu Ora Health New Zealand to prepare for the possible arrival of the H5N1 bird flu.
Doc was developing plans to mitigate risks to threatened species in case H5N1 bird flu arrived "including actions to enhance detection, reduce spread and protect threatened species".
"This includes identifying at-risk species and high-risk sites to ensure support is provided to these areas if the disease arrives in the country.
"It also includes ensuring enhanced biosecurity measures are in place for important sites for threatened species and Doc captive breeding facilities.
"If bird flu arrives in New Zealand and spreads in the wild bird population, we won’t be able to eradicate it from wild birds and management options will be limited."
