Deputy director-general Stuart Anderson said in a statement today that testing had confirmed further cases of an H7N6 subtype of avian influenza in chickens in a second shed at the farm.
"The remote farm remains under strict biosecurity controls to restrict the movement of birds, poultry products, feed, and equipment on or off the property. The detection of further positive cases on the farm is not unexpected given the nature of the virus."
Mr Anderson said the birds in both sheds, which total about 80,000-layer hens, would be humanely culled with the farmer’s co-operation and this is planned to start tomorrow.
"This is expected to take two to three days, using existing industry standard practice of CO2 containerised gas, which farms regularly use to euthanise chickens. At present, there will be no major impact on egg supplies as New Zealand has about 3.9-million-layer hens a year."
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.
Mr Anderson was on site at the Otago farm today to observe operations.
“We acknowledge this is an extremely difficult time for the farm’s operator, but we commend their actions,” Mr Anderson says.
“Mainland Poultry took the right steps by notifying us of sick and dying birds. The farm has strong biosecurity standards. Three specialist veterinarians from the Ministry for Primary Industries (MPI) are on site.
“They have been carrying out further investigations and taking samples from birds in other sheds on the farm and conducting tracing work to six other poultry farms in the area that are linked to the affected property.
“We are also tracing all movements to and from the farm over the past week. We will place biosecurity controls on any property if we need to manage any biosecurity risk.”
The farm has four sheds with about 160,000 birds in total.
"We're preparing to take measures across all of those sheds if it is required," MPI's chief veterinary office, Mary 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 a security guard was posted outside the entrance gate.
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, Biosecurity Minister Andrew 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.
Mr 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."
— By Matthew Littlewood and Staff Reporters
