The recent outbreak of H5 avian influenza, commonly known as H5 bird flu, has emerged as a pressing health concern that affects not only bird populations but also poses risks to wildlife and livestock, such as dairy cattle. A notable incident in 2024 involving H5 bird flu in US dairy herds serves as a crucial reminder for Australian farmers to stay alert and proactive.
This particular strain of the virus was first identified in dairy cows across the United States, leading to both health issues in the animals and significant declines in milk production. Additionally, some dairy farm workers who came into contact with the infected cattle also experienced illness. Since its discovery, the virus has proliferated through 18 states, impacting over 1,000 dairy farms.
What makes this outbreak especially alarming is the unanticipated transmission of the virus from birds to dairy cattle. This unprecedented shift offers valuable insights into the virus's behavior within bovine populations and highlights potential pathways for its spread in dairy farming systems.
Currently, Australia has been fortunate enough to remain free from this H5 strain, and the risk to its dairy industry is regarded as minimal. However, the lessons learned from the American experience are instructive and can inform Australia's future preparedness strategies.
In response to the evolving global landscape regarding avian influenza, the Federal Government, in collaboration with state and territory authorities and industry stakeholders, has taken significant steps to bolster national readiness. This includes enhanced surveillance capabilities, improved coordination between agencies focused on animal, wildlife, and human health, and targeted investment initiatives.
For the dairy sector specifically, the Department of Agriculture, Fisheries and Forestry, along with Dairy Australia, has commissioned an independent risk assessment aimed at outlining what a potential outbreak might entail under Australian conditions. The findings—recently shared with farmers and industry participants during a webinar led by Dairy Australia—offered a comprehensive, evidence-based evaluation of both risks and preparedness strategies relevant to Australian dairy operations.
The assessment concluded that the probability of H5 bird flu infiltrating the Australian dairy herd is low. Furthermore, should it enter, the likelihood of it spreading between farms remains equally low. While further research is necessary to understand the various factors influencing the transmission of H5 bird flu in cattle, several reasons contribute to this relatively lower risk. These include factors such as reduced farm density and fewer routine movements of cattle between locations.
Australia's proactive stance gives it a distinct advantage; unlike the United States, where the outbreak was unexpected and allowed for significant viral spread before control measures were implemented, Australia has the opportunity to prepare in advance.
If the H5 bird flu were to make its way to Australia via migrating birds, dairy farmers must be vigilant for specific clinical symptoms. In the affected US herds, common signs included a sudden drop in milk yield, unusual thickening of milk resembling severe mastitis, fever, and lethargy among the cattle. Although mortality rates remained relatively low, many cows exhibited high levels of illness, taking weeks or even months to recover their normal production levels.
Preventive strategies for the Australian dairy industry can draw from the experiences witnessed during the US outbreak. Here are several straightforward measures that can help avert the introduction and spread of H5:
Animal Movements: When purchasing new animals or moving them between farms, implementing quarantine and observation protocols before integrating cows into the milking herd can significantly reduce exposure to potential infections. Additionally, US authorities have introduced testing requirements for cattle movements and bulk milk screenings to manage risks.
Milking Hygiene: Maintaining strict hygiene practices during milking is vital, especially when handling affected or suspected cows. It’s advisable to milk these animals last or separately to minimize contamination of equipment such as liners and cups. Proper management of mastitic milk, thorough cleaning of milking equipment, and consistent teat preparation are essential practices. Moreover, reducing airborne milk droplets—created by high-pressure washing of spills—by opting for lower-pressure wash methods can lessen exposure risks.
Biosecurity Measures for People: Protecting human health is also a critical aspect of effective biosecurity practices. Wearing gloves while milking and when handling milk or sick animals, washing hands thoroughly after glove removal, and managing potentially contaminated clothing are practical measures to adopt. Promoting seasonal flu vaccinations among farm workers can help mitigate the rare chance of dual infections.
Surveillance and Reporting: Farmers’ instincts and experiences play a crucial role in surveillance. Observing unusual clusters of mastitis-like illnesses, sudden drops in milk production, or unexplained deaths among birds should prompt immediate consultation with veterinary professionals.
Ultimately, preparedness hinges on adhering to fundamental principles. Having a written, regularly updated biosecurity plan is paramount for safeguarding the health of the dairy sector.
- Andy Hancock, Dairy Australia
