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What animal welfare issues are associated with avian influenza?

Avian influenza, commonly called bird flu, is a highly contagious viral disease of birds worldwide. The virus is spread by wild waterfowl (such as ducks, geese, and swans) and shorebirds because they are natural reservoirs, which means they can carry the virus without showing any sign of disease.

There are many strains of the avian influenza virus that are either low pathogenic strains producing little or no clinical symptoms to highly pathogenic strains producing severe disease and high death rates in birds. The avian influenza virus occurs worldwide but the prevalence of certain strains differs between countries [1]. Outbreaks of both low and highly pathogenic strains have occurred in Australia.

Certain highly pathogenic strains of the avian influenza virus, such as H5N1, have caused severe disease and devastating bird deaths in many parts of the world. While the virus does not usually cause disease in mammals including humans some highly pathogenic strains, such as clade, have been linked to spillover infections in farm animals, wildlife, and humans [2]. To date the highly pathogenic strains of H5N1 and clade have not been detected in Australia.

What are the clinical signs of avian influenza?

The clinical signs of avian influenza depend on many factors including how pathogenic the virus is, the species and age of infected birds, and whether they have other diseases. In highly pathogenic strains, clinical signs and death can occur suddenly affecting a large number of birds, whereas in low pathogenic strains the clinical signs are often less obvious.

Common clinical signs of avian influenza include [2,3]:

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

Having skilled persons on farm that can recognise the signs of avian influenza and alert a poultry veterinarian for an accurate diagnosis are essential to preventing further spread of the virus. Owners of birds and backyard hen flocks should also check their birds daily for any changes in their health and behaviour and get advice immediately if they have any concerns.

It is important that any potential signs of avian influenza are reported immediately to the relevant contacts, such as your local vet, agriculture department and the Emergency Animal Disease Watch Hotline on 1800 675 888. The quicker authorities are alerted to avian influenza, the quicker its spread can be stopped and the consequences minimised.

What happens in the event of an avian influenza outbreak?

State and territory governments are responsible for responding and managing avian influenza outbreaks when they occur. Avian influenza is considered a notifiable emergency animal disease (EAD) in Australia, meaning that, in the event of an outbreak, there are strict EAD response steps in place to control and prevent further spread of the disease. These steps are outlined in the AUSVETPLAN avian influenza manual.

Once an avian influenza infection has been confirmed, specialised emergency animal disease teams are activated to implement control measures on the infected farm and any at-risk farms nearby. These control measures may include quarantining the infected farm, movement restrictions, and disease tracing and surveillance activities. To eradicate and prevent further spread of avian influenza, infected birds are depopulated (removed from their shed and killed), and disposed of using approved methods, and then the sheds are decontaminated. Nearby farms and those in surrounding areas are tested and monitored for the disease to ensure the virus has been contained.

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

In the event of an avian influenza outbreak, it is essential to comply with the state and territory government’s directions and control measures. Where large numbers of birds require depopulating, it is extremely important that these birds are all killed humanely. Humane killing means that birds are either killed instantly or rendered insensible until death ensues, without pain, suffering or distress. Methods such as ventilation shutdown are not humane and should never be used.

Animal welfare issues can also occur due to quarantine movement restrictions imposed over a large area. Unaffected poultry may not be able to be transported to slaughter leading to maximum stocking densities in sheds being exceeded and overcrowding occurring on farm. In addition, trucks supplying feed, litter and other supplies may also be delayed.

All those responsible for poultry must have contingency plans for EAD outbreaks and include details to ensure bird welfare is protected in the event of movement restrictions and that all birds can be killed humanely if required.

How can avian influenza outbreaks be prevented?

Practicing biosecurity means protecting the environment, economy, human, and animal health from pests and diseases. Good biosecurity practices are critical to preventing the occurrence and spread of emergency animal diseases such as avian influenza. Commercial poultry farmers should have in place well-developed biosecurity systems, however all bird keepers, particularly those with backyard hens, should also practice strict biosecurity measures.

Birds with access to the outdoors that may come into direct or indirect contact with wild waterfowl are at a higher risk of becoming infected with avian influenza. Good biosecurity measures such as deterring and preventing wild waterfowl accessing areas near the shed or outdoor range area can greatly reduce the risk of avian influenza occurring in free-range housing systems. To learn more about how the risk of avian influenza can be managed in free-range housing systems, click here.


[1] World Organisation for Animal Health (2024) Avian Influenza.

[2] Department of Agriculture, Water and the Environment (2019) Avian influenza or bird flu: the key facts.

[3] Animal Health Australia (2020) Avian influenza.

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Updated on June 5, 2024
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