It is not, however, cause for widespread panic. If the virus has been caught before it has had a chance to circulate more widely, then there is a good chance it can be contained more easily to one farm or a small area, with a humane cull of birds which were close to the source of infection.
In the meantime, all poultry exports are on hold as authorities and the industry work out the best strategies for dealing with the first such outbreak in New Zealand.
About 80,000 layer-hens from the farm will be euthanised over the next couple of days, a highly distressing task for the farmer and something which is upsetting for all bird lovers.
Bird flu has been spreading across parts of the northern hemisphere for several decades. However, in recent years, the more deadly to birds H5N1 2.3.4.4b strain has quickly established itself in wild bird populations throughout Europe, Asia, the United Kingdom and the United States, raising fears its ability to jump from birds to other species and then infect humans will become easier and quicker.
According to the World Health Organisation, between January 2003 and October this year there were 904 cases of human infection with H5N1 avian influenza from 24 countries, 464 of those fatal.
The H5N1 strain has now also spread to birds in South America, and across the Antarctic peninsula and sub-Antarctic islands. Australia and New Zealand remain free of it, although birds with the H7 family of virus have been culled from farms across the Tasman this year.
Biosecurity New Zealand says testing shows the infection in birds at the Hillgrove farm is of the H7N6 subtype which, while still highly pathogenic and of serious concern, is not linked to the H5N1 strain which has caused huge apprehension overseas.
It was also unrelated to the H7 strains which had been identified in Australia, deputy director-general Stuart Anderson said.
Scientists say it is possible that hens, foraging outside at Hillgrove, were infected by wild waterfowl. The University of Otago’s Prof Jemma Geoghegan believes H7N6 may already have been here in wild birds that live in the estuary near the farm or that migrate here. The virus strain then likely spilled over to chickens and became pathogenic.
The spread of infection from one shed to another, doubling the number of birds which need to be culled, has not surprised Biosecurity NZ or Federated Farmers. The speedy response of Mainland Products and the farm operators in notifying authorities of sick and dying hens has been singled out by Mr Anderson.
All movements to and from the farm are now being investigated to ensure infection hasn’t spread elsewhere.
At this stage, it is possible another 80,000 birds in the two other sheds have not been affected. Hopefully that is the case, although the Ministry for Primary Industries’ chief veterinary officer, Mary van Andel, says it is prepared to extend the cull if necessary.
In a country so dependent on its agricultural sector, any disease outbreak on a farm is going to generate frightening reverberations of previous epidemics.
Early in 1981, New Zealand held its breath when pigs on a Temuka farm had blisters on their snouts, raising fears we had our first cases of foot-and-mouth disease. The pigs and sheep were killed, and it was then discovered the blisters were due to their food.
More recently, the eradication of Mycoplasma bovis from the outbreak which began in 2017 has cost more than $720 million.
While it is unclear what might happen next with the outbreak of H7N6 bird flu, it at least appears that the right steps have been taken at this early stage to stop its further spread.
We have to cross our fingers and hope for the best.
