Avian Influenza (AI): what you need to know

Emergency Animal Diseases (EADs) pose a serious threat to the health and productivity of Australia’s feedlot industry. This blog series will outline a number of EADs and is designed to help you stay informed, prepared, and ready to respond. 

What Is Avian Influenza (AI)? 

Avian Influenza (AI) is a highly contagious viral infection that primarily affects birds, including poultry and wild avian species. The disease is caused by influenza type A viruses, which vary in severity and are classified as either low pathogenicity AI (LPAI) or high pathogenicity AI (HPAI). 

In March 2024, the United States reported the first-ever detection of highly pathogenic avian influenza (HPAI) strain H5N1 (clade 2.3.4.4b) in dairy cattle, marking a significant mutation of the virus that previously had not been found in bovine species.

Australia remains the only continent free from H5N1, though we do experience LPAI outbreaks. While the risk of H5N1 mutating and spreading to cattle in Australia is considered low, it remains a potential concern. 

About the Disease 

The H5N1 strain detected in the U.S. is a mutation of existing strains, caused by clade 2.3.4.4b, genotype B3.13, which originated from a reassortment of H5N1 and a North American LPAI virus. 

Strains found in Victoria, New South Wales (NSW), and the Australian Capital Territory (ACT) in recent years have all been H7, and while still harmful to poultry and wild birds, they are not as adaptive and persistent as H5N1. 

What Are the Signs of Avian Influenza? 

In Cattle (H5N1-related) While AI traditionally affects birds, the recent U.S. outbreak has shown that H5N1 can also infect cattle. Signs in infected cattle may include: 

• Decreased feed intake 

• Reduced rumination and rumen motility 

• Respiratory issues such as nasal discharge, coughing, pneumonia and laboured breathing 

• Sudden and significant drop in milk production 

• Thickened, colostrum-like milk in severely affected cattle 

• Abnormal, loose or sticky faeces 

• Lameness and possible abortion 

• General signs like lethargy, fever, and dehydration 

In Poultry and Wild Birds AI can severely impact domestic and wild bird populations. Look for: 

• Lethargy, reluctance to eat or move 

• Ruffled feathers, droopy posture 

• Swelling of the head, neck, or limbs 

• Dark or bruised combs, feet, or skin 

• Respiratory symptoms such as coughing or sneezing 

• Diarrhea and reduced egg production 

How Is Avian Influenza Transmitted and Spread? 

Australia’s geographic location and natural migratory barriers have historically provided protection from HPAI strains like H5N1. However, the current H5N1 strain is highly adaptive and has already infected over 40 mammalian species and more than 300 bird species globally. 

Transmission can occur via: 

• Contact with infected wild birds 

• Contaminated feed, water, or bedding 

• Fomites (e.g., boots, tools, vehicles) 

• Mechanical transmission by other animals or humans 

• Evidence suggests possible cattle-to-cattle and cattle-to-bird transmission with the new H5N1 strain 

If an outbreak were to occur, it would likely begin with wild birds contaminating cattle environments, particularly through shared water or feed sources. 

How to Report Avian Influenza in Australia 

Avian Influenza is a notifiable disease. Early detection is critical. Feedlot operators should report if they notice: 

• Multiple cattle off feed across several pens 

• Lethargic cattle with respiratory symptoms 

• Abnormal milk production in lactating cattle 

• Unexplained deaths or illnesses in poultry flocks 

• Multiple dead or sick wild birds or animals 

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If you suspect AI, do not handle the animals directly. H5N1 can be transmitted to humans through close contact.

Document what you observe and contact your veterinarian or the: Emergency Animal Disease (EAD) Watch Hotline: 1800 675 888 

Prompt reporting protects Australia’s livestock, wildlife, and public health.