New Zealand MPI: 2nd Barn Tests Positive for HPAI H7N6

 

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Yesterday New Zealand reported their very first HPAI outbreak, when H7N6 was detected in a large free-range commercial layer farm located in East Otago. The WOAH WAHIS Notification (#IN_170686) cites 220000 susceptible birds, and provides the following epidemiological comment:

EPIDEMIOLOGICAL COMMENTS

A H7N6 highly pathogenic avian influenza (HPAI) virus has been confirmed on a free-range commercial layer chicken farm in East Otago in the South Island of New Zealand. The sequencing of the virus is similar to a low pathogenicity avian influenza strain previously identified in New Zealand wild birds. Movement controls have been implemented. A 10 km buffer zone has been established around the infected property with the intention of setting up a containment zone. Epidemiological investigation, tracing, and initiating depopulation of the affected population is underway.

Media reports yesterday had suggested there were roughly 40,000 birds in the affected barn (one of several on this farm) and there was no sign of further spread. Today, however, New Zealand's MPI (Ministry of Primary Industries) has announced a 2nd barn on the premises has tested positive. 

H7N6 in Otago – situation update 3 December 2024
Date: 03 December 2024

BiosecurityNZ_media@mpi.govt.nz
Last reviewed: 03.12.24

Biosecurity New Zealand continues to work closely with Mainland Poultry following the detection of a high pathogenic strain of avian influenza, H7N6, at one of its commercial egg farms in rural Otago.

"Testing has confirmed further cases of an H7N6 subtype of avian influenza in chickens in a second shed at the farm," Biosecurity New Zealand deputy director-general Stuart Anderson says.

"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 says the birds in both sheds, which total about 80,000 layer hens, would be humanely culled with the farmer’s cooperation and this is planned to start tomorrow (Wednesday).

"This is expected to take 2 to 3 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.

"Once the sheds have been depopulated, they will be thoroughly cleaned. It will be sometime before those sheds can be safely repopulated. We have Biosecurity New Zealand response staff on-site in Otago, and they are providing advice and guidance, including logistics and planning with depopulation and disposal of the birds."

Testing of other sheds on the property continues.

"If required, we will put more restrictions in place, however, at this stage, there have been no further reports of any avian influenza type symptoms showing in chickens in any other poultry farm.

Mr Anderson says the risk to human health remains low, and there are no concerns for food safety or wildlife.

The property, managed by Mainland Poultry, was placed under a restricted place notice on Sunday after results from testing confirmed H7N6 strain in chickens from one shed on the property. The virus has likely developed from interactions with local waterfowl and wild birds.

Mr Anderson is 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. 3 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 6 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."

Mr Anderson says next steps include continuing to collect samples for testing. The incubation period for the virus is usually 3 to 14 days, with a possibility up to 21 days, so testing will continue over the next 2 to 3 weeks.

"Biosecurity New Zealand has a comprehensive surveillance programme of all poultry properties in the area, where we are testing birds on those properties for any signs of avian influenza."

A further update will be provided at midday tomorrow.

For further information and general enquiries, call MPI on 0800 00 83 33 or email info@mpi.govt.nz

For media enquiries, contact the media team on 029 894 0328.

While H7 viruses (with the notable exception of China's H7N9) are considered to be less of a threat to human health than H5 viruses, they do have a track record of infecting humans (see here, here, and here). 

Just over 21 years ago the Netherlands suffered a record setting H7N7 outbreak which resulted in the loss of 30 million birds across 1,000 farms, and saw scores of mild human infections and the death of a veterinarian  (see 2005 Eurosurveillance Human-to-human transmission of avian influenza A/H7N7, The Netherlands, 2003).

Another analysis, performed by the RIVM (Ministry of Health) found the spread of the virus to be much greater than originally reported.

Executive summary Avian Flu Epidemic 2003: Public health consequences 

Investigation of risk factors, health, well-being, health-care needs, and preventive measures with regard to poultry farmers and persons involved in controlling the AI H7N7 epidemic in the Netherlands 

A Bosman, YM Mulder, JRJ de Leeuw1 , A Meijer, M Du Ry van Beest Holle, RA Kamst, PG van der Velden1 , MAE Conyn-van Spaendonck, MPG Koopmans, MWMM Ruijten

It is estimated that at least one thousand persons were infected with avian flu during the outbreak in the Netherlands in 2003. One-third of the poultry farmers whose holdings were cleared reported stress reactions, fatigue, and depression.

The extensive spread of the virus to humans underscores the importance of measures to prevent poultry-to-human transmission among people handling infected poultry. The possible uncertainty, stress, and anxiety associated with avian flu control demand specific health care attention. A total of 453 people reported symptoms, predominantly conjunctivitis.

Antibodies were found in 59% of family members of infected poultry workers. Of the 500 tested persons who had handled infected poultry, about 50% showed an antibody response.

While we've seen far more virulent H7 viruses emerge (i.e. H7N9 in China), this remains the largest documented example of human-to-human spread of a novel zoonotic avian flu virus we've seen. 

And a reminder why we treat HPAI H7 viruses with considerable respect.