What is avian influenza (or ‘bird flu’) and what is its impact on animal welfare?

Avian influenza, commonly called bird flu, is a highly contagious viral disease that primarily affects birds but can also pose risks to other animals and humans [1]. It is known to affect more than 140 bird species including chickens, turkeys, quail, guinea fowl, ducks, geese, emus and ostriches [2]. Avian influenza is found globally, affecting all continents, including Antarctica.

Australia is geographically isolated, which provides some protection from global outbreaks. However, migratory shorebirds and wild waterfowl like ducks, geese and swans, serve as natural reservoirs of the virus and travel to Australia from regions affected by avian influenza and can therefore introduce the disease. The virus can be classified as low pathogenic, causing mild or no symptoms, or highly pathogenic, leading to severe disease and high mortality rates in birds.

While outbreaks of both low and highly pathogenic strains have occurred in Australia, the highly pathogenic strain known as H5N1 (clade 2.3.4.4b), which has caused severe disease and deaths of wild birds and poultry worldwide, has not yet been detected in the country. The most recent outbreak in Australia occurred in 2024 [3].

What are the clinical signs of avian influenza?

The clinical signs of avian influenza depend on many factors, including the pathogenicity of the strain, the species and age of infected birds, and any pre-existing health conditions. Highly pathogenic strains can cause sudden and widespread deaths, while low pathogenic strains often result in less obvious symptoms.

Common signs of avian influenza include [2,4,5]:

• sudden death in multiple birds
• ruffled feathers, unusual head or neck posture, droopy appearance
• watery eyes
• birds unable to walk or stand
• reluctance to move, eat or drink
• respiratory distress
• diarrhoea
• swollen and discoloured head, wattle, or comb
• a dramatic drop in egg production.

Farm personnel must be trained to recognise these signs and promptly alert a poultry veterinarian for an accurate diagnosis. Backyard bird owners should also monitor their birds daily and seek veterinary advice if they have any concerns. Prompt reporting of suspected cases to local authorities or the Emergency Animal Disease Watch Hotline (1800 675 888) is critical for early intervention and containment of the disease.

What happens during an avian influenza outbreak?

Avian influenza is classified as a notifiable Emergency Animal Disease (EAD) in Australia. In the event of an outbreak, state and territory governments activate response measures as outlined in the AUSVETPLAN avian influenza manual [4]. Key steps in managing an outbreak include:

1. quarantine and movement restrictions: establishing a quarantine radius around the infected property to prevent the spread of the virus
2. disease tracing and surveillance: identifying at-risk locations and testing nearby farms and backyard flocks
3. euthanasia and disposal: infected birds are euthanised and disposed of using approved methods. Unaffected birds within the quarantine radius may also be euthanised to prevent further spread of the disease.
4. decontamination: cleaning and disinfecting facilities, equipment and properties.

Housing orders may also be implemented for nearby properties, requiring free-range poultry and backyard birds to be kept indoors to reduce their risk of exposure to the virus.

Farmers and bird owners must comply with regulatory guidelines to support containment efforts and protect both bird populations and public health.

What are the animal welfare issues associated with avian influenza outbreaks?

In the event of an avian influenza outbreak, large numbers of birds will require euthanasia. It is crucial that all birds are killed humanely. Humane killing means that birds are either killed instantly or rendered insensible until death ensues, without pain, suffering or distress. Mass killing methods such as ventilation shutdown are not humane and should never be used.

Animal welfare issues can also arise due to quarantine movement restrictions imposed across a quarantine radius to contain the disease and reduce its spread. Unaffected poultry within the quarantined radius may not be able to be transported to slaughter, leading, for example, to overcrowding in poultry sheds as birds continue to grow beyond maximum stocking densities. Additionally, movement restrictions on trucks transporting feed, bedding litter and other supplies can result in significant delays, exacerbating welfare concerns.

For this reason, preventative biosecurity measures are essential and must include contingency plans for emergency animal disease. These plans should prioritise bird welfare measures, including strategies for handling movement restrictions and the euthanasia or humane killing of large number of birds if necessary. During an avian influenza outbreak, it is essential to comply with the directions and control measures set by state and territory governments to mitigate the spread of the virus and safeguard animal welfare.

How can avian influenza outbreaks be prevented?

Good biosecurity practices are essential to prevent the occurrence and spread of avian influenza. While commercial poultry farmers have in place biosecurity programs, backyard bird keepers should also adopt steps to protect birds from diseases [5].

Birds with outdoor access are at higher risk of becoming infected with avian influenza if they come into direct or indirect contact with wild waterfowl. Good biosecurity measures may therefore include deterring and preventing wild waterfowl from accessing areas near the poultry shed or outdoor range area. To learn more about the risk of avian influenza in farmed poultry systems, click here.