Bird flu has spread to another shed on an egg Otago farm, the Ministry for Primary Industries has confirmed.
As many as 80,000 chickens will be killed after the avian influenza outbreak was detected at a Moeraki egg farm, the first such case to be reported in New Zealand.
MPI's chief veterinary office, Mary van Andel, said 80,000 chickens would now need to be culled at Mainland Poultry's Hillgrove Egg Farm, doubling from 40,000.
Biosecurity New Zealand has placed strict movement controls on the rural Otago commercial egg farm at Hillgrove near Moeraki, after testing confirmed a highly pathogenic strain of avian influenza in chickens that has likely developed from interactions with local waterfowl and wild birds.
There have been no reports of ill or dead birds on other poultry farms, but six other poultry farms are considered to be at risk.
In the meantime, all poultry exports are on hold.
A Mainland Poultry spokeswoman confirmed testing was under way at its other farms.
It operates three other sites in Otago, including its Waikouaiti site, which is one of the largest poultry farms in the country.
All four farms sit within a 25km radius.
Biosecurity Minister Andrew Hoggard said the shed where the virus was first detected held about 40,000 chickens, which would be "depopulated".
It has since spread to another nearby shed at the same farm.
"We're preparing to take measures across all of those sheds if it is required," van Andel said.
Otago Federated Farmers' Luke Kane told RNZ he wasn't surprised by the spread as it appeared the sheds were in close proximity to each other.
All appeared quiet at the farm in question this morning and no chickens could be seen outside their sheds.
Staff at the affected farm were noticing issues with poultry late last week, and tests were taken over the weekend, Mr Hoggard said.
Massey University distinguished professor Nigel French told the ODT the particular strain detected was not an "epidemic" strain, but was still "highly concerning" and it was likely the poultry industry would be on tenterhooks.
"If you detect anything like this on the farm, you need to contact Ministry for Primary Industries [MPI] straight away.
"I know the industry has been very, very keen to make sure that poultry farmers are aware of what to see and what to look out for."
Biosecurity New Zealand deputy director-general Stuart Anderson said in a statement tests from the Mainland Poultry-managed farm had identified a highly pathogenic H7N6 subtype of avian influenza after illness was noted among the chickens last week.
"While it is not the H5N1 type circulating among wildlife around the world that has caused concern, we are taking the find seriously.
"Our testing shows it is unrelated to an H7 strain that was identified in Australia earlier this year and we believe this case may have happened as part of a spillover event, where laying hens who were foraging outside of the shed were exposed to a low-pathogenic virus from wild waterfowl," Mr Anderson said.
But he acknowledged this event was "kind of taking us by surprise in a way because we were really looking out for the strain that’s spreading around the world".
"That was the one that we were worried was going to come into New Zealand in migratory wild birds or in wild mammals."
The MPI and Mainland Poultry would be doing their absolute best to get on top of the event, he said.
"Hopefully, it will just disappear, but we can’t guarantee that."
Mr Anderson said low-pathogenic viruses were present in wild birds here, especially waterfowl such as ducks, geese and swans, and the virus could mutate on interaction with chickens.
The strain found on the affected farm was not a wildlife-adapted strain such as H5N1, he said.
Mr Anderson said quick action had been taken in co-operation with Mainland Poultry and a restricted-place notice issued.
"We will move quickly, with Mainland Poultry, to depopulate birds on the remote property and we’ve placed a 10km buffer zone around it alongside the restrictions preventing movement of animals, equipment and feed."
Mainland Poultry chief executive John McKay said in a statement the company was committed to taking quick action.
"We have been preparing for an event like this for some time, knowing that low-pathogenic avian influenza is already present in New Zealand wild birds.
"Fortunately, this is not the H5N1 type that has caused concern for wildlife in other parts of the world."
Biosecurity New Zealand was working with industry partners to ensure the find was dealt with quickly and any possible impacts to trade limited, he said.
"Importantly, the farm has strong biosecurity standards and Mainland is helping with ongoing investigation and tracing of animal movements."
— Matthew Littlewood and Staff Reporters
