Avian influenza: dairy cattle and other livestock

What we know about the dairy herds in the US infected with HPAI H5N1

New Zealand has never had a case of the H5N1 strain high pathogenicity avian influenza (HPAI), a type of avian influenza (bird flu) that affects domestic and wild birds.

While HPAI is not a cattle disease, the H5N1 strain of the virus has been detected in a number of dairy herds in the United States. This is the only known transmission (referred to as 'spillover') to cows worldwide. Information from the American Veterinary Medical Association is that most cattle recover in 2 to 3 weeks with supportive care.

The US infection came from a spillover event where wild birds infected cattle on a handful of farms in northern Texas. The movement of infected cattle has then spread that variant of the virus to other states.

The way the disease is spreading on farms is being investigated. Possible pathways include through feed contamination, cow to cow contact, and milking practices. Testing indicates the virus has spread between cows within the same herd, and from cows to poultry.

A few dairy farmworkers who were in close contact with infected cattle were also infected with the virus. The workers showed mild symptoms and recovered.

HPAI has not been detected or reported in beef cattle to date.

We encourage all farmers to practice good on-farm biosecurity and be aware of the potential risk should HPAI H5N1 arrive here.

A different HPAI strain, H7N6, was detected at a commercial egg farm in Otago on 2 December 2024. This strain is not a wildlife adapted strain like HN51, so is unlikely to be transmitted to mammals.

Practice good biosecurity on your farm

Should HPAI H5N1 arrive in New Zealand, early detection will help us manage an incursion.

Farmers and those keeping animals on lifestyle blocks should be prepared by:

• using good biosecurity practices
• monitoring the health of their herds
• seeking veterinary advice if animals become unwell.

By following biosecurity guidelines, including good hygiene practices, you can reduce the risk of pests and diseases on your farm or lifestyle block.

Clinical signs of HPAI H5N1 in cattle

Cattle with mild illness show non-specific clinical signs such as decreased milk production, thicker colostrum-like milk, reduced appetite, lethargy, fever, and dehydration. Some cattle without clinical signs of disease have tested positive for HPAI.

If HPAI arrives in New Zealand, farmers and vets should be alert for possible spillover into mammals.

This page will be updated with specific information and practices for farmers to reduce the risk of infection should HPAI be detected in New Zealand.

Ways to prevent farm-to-farm bovine spread

• Keep NAIT (National Animal Identification and Tracing) updated. NAIT is a legal requirement and key to good biosecurity, as it makes it easier and faster to trace animals.
• Run cattle in management units that don't mix. Minimise introductions and keep any introductions low risk. For example, keep mobs separate for their duration on grazing blocks.
• Secure boundaries through fencing and due diligence. Make sure nose-to-nose contact is not possible between cattle held on neighbouring properties.
• Ensure any biological products and equipment you bring on-farm (such as borrowed milk feeding equipment) is clean and disinfected prior to use on your property.
• Avoid having staff work across multiple sites.

No risk from drinking pasteurised milk

There is no risk to human health from consuming pasteurised milk and milk products. Repeated testing of milk in the US has confirmed that, although viral fragments may be present in pasteurised milk, pasteurisation kills the virus and these fragments are not infectious.

US authorities have issued caution against consuming raw milk. New Zealand does not import unpasteurised dairy products from the US.

Signs of HPAI in birds

The most obvious sign of HPAI is sudden death in several birds. Other signs can include weakness, tremors, paralysis, difficulty breathing, lack of coordination, blindness, trembling, and diarrhoea.

Poultry show more severe signs than wild birds. These include lethargy, reduced appetite, droopy head, darkened or swollen comb/wattle, panting, nasal secretions, unusual drop in egg production, and bleeding disorders.

If you notice poultry or domestic birds exhibiting signs of HPAI, contact your veterinarian first to rule out more common avian diseases. Wait for your veterinarian's instructions before handling any sick or dead birds.

Culling wild birds can increase bird flu spread

If HPAI H5N1 is detected in New Zealand, farmers and hunters will be advised against actively culling or dispersing wild birds on their property because it can increase the spread of HPAI.

Disturbing groups of wild birds might cause them to scatter and spread the disease further. Other birds will quickly move into the vacated space and may bring the virus with them.

Reporting avian influenza

If you see 3 or more sick or dead poultry in a group, report it immediately to the exotic pest and disease hotline on 0800 809 966 so we can investigate the cause. Do not handle or move the birds.

Provide as much detail as you can, including:

• a GPS reading or other precise location information
• photographs and videos of sick and dead birds
• species name and estimate of the numbers affected
• how many are sick or freshly dead, and the total number of birds present.

We will note the details and one of our specialist biosecurity investigators will assess the information and contact you.

How to report suspected bird flu – fact sheet [PDF, 700 KB]

How we're preparing for HPAI

We're working with the Department of Conservation, the Ministry of Health, Health New Zealand (Te Whatu Ora), and our industry partners to prepare for any detection of HPAI H5N1 in New Zealand.

We're monitoring what's happening overseas

We are monitoring developments overseas and working with international colleagues to learn everything we can from their experiences, so we can keep our industry partners and the dairy community informed.

We are closely monitoring updates from the World Organisation for Animal Health, the World Health Organization, United States Department of Agriculture (USDA), United States Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC). We are in regular contact with the US Chief Veterinary Officer to understand any developments there, and our industry and scientific communities have close links with colleagues in the US.

Find out more about avian influenza

Avian influenza – World Organisation for Animal Health (WOAH)

Information on avian influenza detections in livestock – Animal and Plant Health Inspection Service (USDA)

Updates on Highly Pathogenic Avian Influenza (HPAI) – US Food and Drug Administration (FDA)

Influenza (avian and other zoonotic) – World Health Organization (WHO)