The H5N1 unicorn… for now

By Justin Toohey – Animal Health, Welfare and Biosecurity Advisor, Australian Dairy Farmers

For several years now, Australia has watched Highly Pathogenic Avian Influenza (H5N1) sweep through bird populations across nearly every continent.

Remarkably, to date we remain the only continent free of the virus.

That absence is good news, but it’s also the core reason dairy farmers must stay alert.

Although H5N1 has never been detected in Australia’s wildlife, poultry or cattle, the global pattern is clear.

The unprecedented outbreak in the US dairy herds in 2024 has given us a valuable insight into how the virus behaves in cattle, and how we can best prepare should it eventually arrive here.

While there is a relatively low risk of the disease entering the Australian dairy herd, we must heed the US experience that saw it as the only continent where H5 bird flu directly impacted dairy cattle and their handlers.

US dairy herds have proved particularly vulnerable to the spread of this disease for several reasons.

Compared with Australian dairy farms, they tend to involve shed-based rather than pasture-based systems, with significantly higher movements of people and cattle, including lactating cattle, between operations.

While the risk profile of Australia’s dairy industry is fundamentally different, we must still be vigilant.

This very topic was the focus of a recent industry breakfast held by Australian Dairy Farmers (ADF) at International Dairy Week.

Guest speaker, Dairy Australia’s Dr Andy Hancock, outlined how the US was caught off guard and what we can learn from the US for application here.

This ties in with work last year by Dairy Australia and the Department of Agriculture, Fisheries and Forestry, studying the risks of H5 bird flu to the domestic dairy herd.

It was evident from this presentation that, in the event of H5N1 arriving in Australia, much can be done by dairy farmers to reduce the risk of infection and/or spread among their herds and farm workers. Key recommendations were:

Prevent entry (spillover) by:

1. Keeping poultry away from milking bails
2. Monitoring wild bird populations on farm and requesting tests if any suspicion
3. Where possible, minimising access of wild birds, poultry and other animals to dairy cattle feed and water sources
4. Updating and applying on-farm biosecurity plans
5. Being alert and reporting promptly any illness in cattle, workers or pets

Reduce within-farm spread by:

1. Observing strict hygiene practices, especially on entry and exit of sheds and during milking
2. Not feeding mastitis-affected milk to calves or pets
3. Preferably treating all milk before feeding it to calves or pets
4. Implementing early detection and isolation of infected animals

Reduce between-farm spread by:

1. Minimising animal and people movements
2. Observing strict biosecurity measures, including self-quarantining where possible
3. Avoiding the movement of raw milk between farms

Reduce the impact by:

1. Preparing early for the treatment of sick animals
2. Seriously considering the use of appropriate personal protective equipment
3. Ensuring no human consumption of raw milk
4. Maximising the chance of early detection by increasing surveillance and testing

None of these points is particularly difficult to action, and it’s important to practise them now.

While it is not expected the virus will enter the dairy herd in Australia, we must prepare regardless.

It’s important we remember that in the US it predominantly spread between dairy herds through milk and the movement of infected cattle.

The virus is killed by the pasteurisation process, making processed milk safe for consumption.

By implementing the simple techniques listed above, farmers can be confident they’ll be pulling their weight if the need arises to control the spread of H5N1 in the Australian dairy herd.

What to watch for

If H5N1 were ever detected in Australia, it would be national news.  But the first line of defence on farm is early recognition of symptoms.

The signs of H5N1 in cattle include:

• Sudden, sharp drops in milk production
• Thickened or mastitis-like milk, often multi quarter
• Cows not responding to normal intramammary treatment
• Non-specific illness: fever, dehydration, low rumination
• Clusters of cases rather than isolated events

The process for testing milk samples is straightforward, but only once dairy farmers or field officers suspect something unusual. Remember, the risk is low, but early detection is key!