Information for vets about HPAI (bird flu)

High pathogenicity avian influenza (HPAI) H5N1

HPAI H5N1 clade 2.3.4.4b strain of high pathogenicity avian influenza (HPAI) has caused high numbers of deaths in poultry and wild birds overseas.

Avian influenza is a notifiable disease. Strains of avian influenza are categorised as either low pathogenicity (LPAI) or high pathogenicity (HPAI) depending on the severity of disease caused in chickens. LPAI viruses can occur in wild birds in New Zealand, notably waterfowl (ducks, geese, and swans) and shorebirds, and typically do not cause severe disease.

New Zealand has never had a case of HPAI. As more information emerges about how the disease affects wild bird species in the Southern Ocean, we’ll have a better understanding of the likelihood of it reaching New Zealand through migrating birds.

If HPAI is detected in New Zealand or its territories, the Ministry for Primary Industries (MPI) will be the lead agency and will coordinate any response in partnership with the Department of Conservation (DOC), the Ministry of Health, and Health New Zealand (Te Whatu Ora). Veterinarians have an important role in providing evidence-based advice to clients and communities, as well as reporting any suspected cases of HPAI to MPI.

If you suspect HPAI, contact the exotic pest and disease hotline on 0800 80 99 66 immediately.

The hotline is open 24 hours a day, 7 days a week.

The current outbreak

Prior to 2020, the usual pattern of HPAI emergence was as a mutation of low pathogenicity avian influenza (LPAI) in chickens, associated with contact between waterfowl with LPAI and poultry.

In 2020 a strain of HPAI, H5N1 clade 2.3.4.4b emerged that was well adapted to persisting and spreading in wild bird species. This strain was also different because it established in wildlife population species other than waterfowl. This allowed it to spread across the Atlantic to the Americas and eventually to the Antarctic peninsula through movement of these new host species.

Spillover events into other species are associated with cohabitation or direct consumption of infected animals or faecal matter. Overseas, infected mammals have included dairy cattle, goats, cats, and dogs, as well as wildlife species.

Be alert for signs in commercial and domestic poultry, and wildlife

An outbreak of the HPAI clade 2.3.4.4.b would likely be detected first in wild birds. At this stage, seabirds, shorebirds, and waterfowl are groups of concern. There may be varying signs of disease in infected birds, ranging from respiratory, enteric and neurological disease of varied severity to acute or progressive severe systemic disease with very high mortality.

Include avian influenza in your differential diagnosis list for any unusual disease outbreaks or mortality events.

Clinical signs of HPAI

The most obvious sign of HPAI is rapid mortality among a group of birds. The clinical signs of HPAI in birds are extensive and could cover a variety of clinical conditions across all species of birds.

Clinical signs in domestic backyard poultry flocks

There are several clinical signs which are typical of common diseases in domestic poultry, and do not necessarily indicate HPAI when seen in individual birds in an otherwise well flock. However, for any birds in shared housing, when multiple birds are affected, the following signs may be suspicious of HPAI:

unexpected deaths – sudden and rapid increase in the number of birds found dead with several other birds affected in the same shed or air space
unresponsive – quiet birds who don’t want to come out and engage as usual or come for treats (They may sit around, fluffed up. They may rally temporarily, but then soon tire)
huddling – with each other or against coop furniture/equipment like in nests or around drinkers
bruising – blood spots or swelling, haemorrhages on shanks of the legs and under the skin of the neck
coughing, sneezing, gurgling, rattling or gaping
focal facial swelling, for example, around the eyes
ocular discharge
cessation or marked reduction in egg production
loss of appetite or marked decrease in feed consumption
sudden increase or decrease in water consumption
lethargy and depression
fever or noticeable increase in body temperature
diarrhoea – discoloured or loose watery droppings.

Clinical signs in wild birds

Although HPAI has been isolated in a very wide range of wild bird species, the most common species affected are waterbirds, such as swans, ducks, geese, and scavenging birds, such as gulls and some birds of prey. Clinical signs, involving the respiratory, digestive or nervous system, are highly variable both between species and between individual birds. For example, swans frequently present with neurological signs including head shaking, twisting of the neck, and swimming in circles. Birds of prey often present with ocular and respiratory signs, while ducks and geese may show very few clinical signs.

The extent to which clinical signs are recognised is also affected by proximity to man, for example seabirds may present dead or dying when washed up on beaches, while swans on a local pond may be seen with early clinical signs. Individual birds are likely to be separated from the flock in gregarious species.

Spillover to other species

If HPAI H5N1 is detected in New Zealand and becomes established in wild birds, veterinarians need to be alert and on the lookout for spillover events to non-avian species. Spillover events into other species are associated with cohabitation or direct consumption of infected animals or faecal matter. Overseas, infected mammals have included dairy cattle, goats, cats and dogs, as well as wildlife species.

As with an example of a spillover event into dairy cattle in the US, the clinical presentation may not be typical for an influenza virus. Always consider having HPAI in your list of differential diagnoses, for something that you have not seen before.

Managing suspected HPAI in clinic

Avian influenza is transmitted between birds by direct contact with an infected bird, or indirectly through contaminated body fluids and faeces. It can also be spread by contaminated feed and water and other environmental matrices, or by contaminated vehicles, clothing, footwear, and equipment. Although it is not an airborne virus, there is the risk of droplet transmission over short distances (less than 10 metres).

Prevention of the spread of the disease, both between birds and to humans, is managed by scrupulous biosecurity, hygiene and appropriate personal protection equipment (PPE).

Movement between premises is a risk pathway that is easily managed. Examine birds well away from other animals at the clinic, in an isolation facility or separate area that can be thoroughly cleaned and disinfected afterwards.

Avoid touching your face after contact with birds or surfaces that may be contaminated. Wash hands well and use appropriate disinfectants for footbaths and environmental disinfection. If using phones to capture photos and videos, ensure they can be and are disinfected before and after handling.

Birds should be triaged prior to examination. This should ideally include telephone triage prior to the bird being brought to the practice, and use of photos and videos as appropriate. In the case of captive birds, this should include information about how and where the birds are being kept, any new recent introductions, duration of clinical signs and the number of birds affected.

Wild birds

We recommend that veterinary practices, where possible, review the patient information and history prior to arrival. All birds of concern should be examined outside the main clinic, wearing appropriate PPE and minimising the number of staff involved.

Backyard poultry

Telephone triage and full consideration of the history and clinical signs, alongside practice-based HPAI risk assessment, can be used to make an appropriate decision whether to see the bird outside or inside the veterinary practice.

More detailed advice for veterinarians is being developed in partnership with veterinary organisations, and will be published on this page.

Report it

If you see 3 or more sick or dead birds in a group within a short period, or suspect a case of HPAI, contact the exotic pest and disease hotline on 0800 80 99 66 immediately.

Provide details of the mortality (such as species involved, number dead and location) and your contact details.

Use PPE before handling any potentially infected birds.