Avian influenza, commonly called bird flu, is a highly contagious viral disease of birds worldwide. Avian influenza is classified as a notifiable emergency animal disease in Australia because of its potential socio-economic consequences [1]. There are numerous strains of the avian influenza virus, ranging from low pathogenic forms that produce little to no clinical symptoms to highly pathogenic strains that produce severe disease and death in birds. 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.
Avian influenza poses a serious health and welfare concern for affected birds and in the event of an outbreak resulting in hundreds and thousands of bird deaths from disease of being killed to prevent further spread of the virus. Read more about the animal welfare issues associated with avian influenza, click here.
Does free-range egg or poultry production increase the risk of avian influenza?
As consumer demand increases for free-range eggs and poultry including layer hens, meat chickens and turkeys, there is the potential for free-ranging birds to come into contact, either directly or indirectly, with wild waterfowl. These wild waterfowl can act as a constant source of avian influenza, carrying the virus in their nasal and eye discharge and faeces. However, it is important to note that surveillance testing in Australia has demonstrated that to date only low pathogenic strains of avian influenza have been identified in Australian wild bird populations [2].
How can the risk of avian influenza be managed?
The risk of birds being exposed to infectious sources of avian influenza can be adequately addressed through good biosecurity practices [3,4]. The key to managing the risk of avian influenza is preventing infection in the first place and then if disease does occur, preventing its spread to other birds on the same farm or on other farms.
Bird management
Maintaining good bird health and welfare is critical to minimising the risk of any disease in poultry. Some strategies to maintain good bird health and welfare include:
- managing birds to ensure healthy immune system (i.e. good gut health)
- managing stocking density to avoid overcrowding and allow birds to move around freely and express natural behaviours
- maintaining litter quality in a dry and friable condition
- preventative vaccine protocols and parasite management
- actively monitoring birds for early symptoms
- development and application of avian influenza vaccines.
Wild waterfowl and outdoor access
A major risk for avian influenza infection is direct or indirect contact with wild waterfowl on farm. Therefore, methods to deter waterfowl from farms can greatly reduce the risk of avian influenza being introduced. Some strategies include not placing feed and water sources on the range, netting range areas or utilising new technologies to deter waterfowl [3]. In addition to this, sheds and range areas should be as far away as possible from open water sources to help reduce the risk of waterfowl contact.
The quality of the outdoor range that birds have access to is also important. Management practices to minimise the risk of disease and maintain a good quality outdoor range include regular rotation of the range for parasite control, avoiding or preventing access to muddy or wet areas on the range, and pest and predator management.
Water treatment
In some farming systems, farm water sources such as dams are used as drinking water for birds. These water sources are a potential source of infection and therefore any drinking water from dams or other open sources should be treated and sanitised [5].
Equipment and vehicle disinfection
Most avian influenza outbreaks in Australia have involved a single farm or small cluster of farms with limited spread. However, the routine practice of sharing equipment and vehicles between poultry farms has been identified as a likely source of the spread of the virus between farms [3]. Equipment sharing between sheds or between farms is particularly an issue where little or no disinfection of equipment occurs, making appropriate disinfection of equipment and vehicles a critical aspect to good biosecurity and disease control.
The routine practice of equipment and vehicle sharing between sheds and farms highlights the importance of good biosecurity protocols to be in place for all on-farm staff and visitors such as visitor logs, records of equipment and vehicles movement, and hand and boot washing facilities between sheds.
Farm location
The distance between farms also plays an important role in limiting the spread of disease from farm to farm, in particular the separation of different poultry species (e.g. between farmed ducks to layer hens). Consideration should be given to the location of poultry farms, such as placement in areas with relatively few waterfowl, avoiding known wild bird flight paths, and having a low concentration of poultry farms in areas to help reduce the spread between farms in the event of an outbreak.
Should we keep birds indoors?
Rather than abandoning free-range production systems, producers should aim to manage these systems in order to reduce the risk of their birds contracting avian influenza. Education around good biosecurity practices and the effective implementation of these practices are some of the most important factors when minimising the risk of a disease and preventing the spread of disease to other farms.
References
[1] Animal Health Australia (2019) Emergency Animal Disease.
[2] Wild Health Australia (2024) Wild bird surveillance.
[3] Scott A, Hernandez-Jover M, Groves P et al (2020) An overview of avian influence in the context of the Australian poultry industry. One Health 10, 100139.
[4] Department of Agriculture, Fisheries and Forestry (2009) National Farm Biosecurity Manual: Poultry Production, 1st edition. Australian Government.
[5] Department of Agriculture, Water and the Environment (2019) National Water Biosecurity Manual – Poultry Production. Australian Government.
