Protecting dairies - lessons from bird flu

H5 avian influenza - or H5 bird flu - is an animal health issue of global significance for bird species, wildlife and potentially livestock, with an outbreak in US dairy cattle highlighting why Australian farmers must remain vigilant.
The virus was first detected in US dairy cattle in 2024, causing illness and production losses in affected herds, along with sickness among some exposed dairy farm workers. Since then, it has spread across 18 US states affecting more than 1000 dairy herds.
The movement of the virus from birds into dairy cows was unprecedented, but it provided insight into how the disease behaves in cattle and how it can spread through dairy systems.
Australia remains free from this strain of H5 bird flu, and the assessed risk to the Australian dairy industry is low. However, the experience overseas offers lessons to guide preparedness activities.
In response to the evolving global situation, the Federal Government, working with states, territories and industry, has strengthened national preparedness through enhanced surveillance, improved coordination across animal, wildlife and human health agencies, and targeted investment.
For the dairy sector, the Department of Agriculture, Fisheries and Forestry, supported by Dairy Australia, commissioned an independent risk assessment to understand what a potential spill over event could look like under Australian conditions. The findings - shared with farmers and industry through a recent Dairy Australia-led webinar - provided a clear, evidence-based view of risk and preparedness for Australian farms.
The assessment found the risk of H5 bird flu entering into the Australian dairy herd was low, and if it was to enter, then the risk of spread between farms was also low. Whilst there is still more to learn about the factors influencing H5 bird flu spread in cattle, this lower risk is probably due to a number of factors, including lower farm density and fewer routine cattle movements.
Australia has the added advantage of being pre-warned, whereas in the US the outbreak was unprecedented, resulting in a period of spread before control measures were enacted.
If H5 bird flu should arrive in Australia via bird migration, dairy farmers should keep an eye out for the clinical signs. In infected US herds, the most consistent signs included a sudden drop in milk production, abnormal thick milk resembling severe mastitis, fever and lethargy. Mortality rates in cattle have been low, but morbidity has been high, with many cows becoming clinically unwell and taking weeks or months to recover production.
Prevention measures for Australian industry
Experience from the US outbreak identified a few simple measures which can be taken to prevent introduction and spread of H5:
Animal movements: Where animal purchases or inter-farm movements occur, quarantine and observation before cows join the milking herd can reduce exposure. In the US authorities have also implemented testing protocols for cattle movements and bulk-milk screening.
Milking hygiene: In infected herds, milking hygiene is critically important.
Milking affected or suspect cows last, or separately where possible, can help limit the spread via liners and cups.
Careful handling of mastitic milk, cleaning of equipment and consistent teat preparation all play a role.
Reducing milk aerosols, or airborne milk droplets, is another practical step. High-pressure hosing of milk spills can create fine aerosols; lower-pressure wash-down methods and minimising splash help reduce exposure.
Protecting people is also part of good biosecurity. Wearing gloves during milking and when handling milk or sick animals, washing hands after glove removal, and managing contaminated work clothing are practical measures. Encouraging seasonal flu vaccination helps reduce the rare possibility of dual infection.
Finally, surveillance relies on farmers' experience and instincts. Unusual clusters of mastitis-like illness, sudden production drops, or unexplained bird deaths should prompt early advice.
Generally, preparedness comes back to fundamentals. A written, up-to-date biosecurity plan remains the foundation.
- Andy Hancock, Dairy Australia