Avian Influenza (Bird Flu)
Since December 2003, the World Organisation for Animal Health (OIE) has received reports of highly pathogenic H5N1 avian influenza (AI) outbreaks in poultry and other birds from Korea, Japan, Vietnam, Thailand, Cambodia, Laos, Indonesia, China, and Malaysia. Most recently, in July and August 2005, first Russia and then Kazakhstan reported the presence of H5N1 virus. On 8 August 2005 Mongolia reported mass mortalities due to avian influenza in wild migratory birds, but the strain is not yet known.
H5N1 has caused the death of around 60 people to date. Accurate statistics on human deaths caused by H5N1 can be found at the WHO website.
Low pathogenic strains, such as the H5N2 reported in Japan in July 2005, are of less immediate concern as they cause little or no disease in birds and do not infect humans.
What is avian influenza?
Avian influenza is a viral disease of birds. There are many strains of avian influenza virus that cause infections of different severity. These range from low pathogenic or mild to highly pathogenic strains that are associated with severe disease and high mortality in poultry.
What is avian influenza A (H5N1)?
This is the designation of the virus that is currently active in South-East Asia. This particular strain is highly lethal to poultry.
The World Health Organization has identified the main risk of transmitting the highly virulent H5N1 strain of avian influenza as the movement of live birds through local markets, where vendors bring large numbers of birds for breeding or eating. The virus can survive in faeces, on feathers, eggs or meat.
What species of animals does avian influenza affect?
Avian influenza viruses can infect a wide variety of birds including domestic poultry — chickens, turkeys, pheasants, partridges, quail, pigeons, ducks, geese, guinea fowl and ostriches — and wild birds. Some migratory waterfowl, sea birds, and waders are commonly infected with AI viruses, but do not show clinical disease. Avian influenza viruses usually only infect birds. So far, all cases of avian influenza in people have been associated with close contact with birds (e.g. the handling of live infected birds). Theoretically, avian influenza viruses could spread to any species susceptible to influenza viruses such as pigs and horses. In practice, this type of spread is extremely limited.
What are the clinical signs of avian influenza in birds?
The clinical signs are variable and depend on a range of factors including the virulence of the virus, the species and age of the birds infected, the presence of concurrent diseases, and the environment.
In very severe forms the disease appears suddenly and birds die quickly. In less severe forms the birds may be off feed and appear depressed.
In some cases, egg production may fall, and soft-shelled eggs may be produced. There may be profuse watery diarrhoea, combs and wattles may become swollen and blue and respiration may be laboured.
In less severe forms, the clinical signs may include decreased egg production, depression, respiratory signs suggestive of a ‘cold’, swelling of the face, possibly some nervous signs, and diarrhoea.
How is avian influenza spread?
In bird populations, the principal means by which avian influenza viruses initiate outbreaks in domestic poultry is by wild birds, particularly ducks, contaminating food or water supplies and subsequent spread of the virus by the movements of infected live birds or contaminated feed, equipment and materials.
Migratory birds are a potential risk of introducing exotic avian influenza viruses to Australia.
Can anything be done to control AI infection in wild birds?
The WHO fully agrees with the United Nations Food and Agriculture Organisation (FAO) and the OIE that control of avian influenza infection in wild bird populations is not feasible and should not be attempted.
Wild waterfowl have been known for some time to be the natural reservoir of all influenza A viruses. Migratory birds can carry these viruses, in their low-pathogenic form, over long distances, but do not usually develop signs of illness and only rarely die of the disease. The instances in which highly pathogenic avian influenza viruses have been detected in migratory birds are likewise rare and the role of these birds in the spread of highly pathogenic avian influenza remains poorly understood.
Human health
Transmission to humans occurs predominantly through the handling of live infected birds or close contact with them and their excretions. Although investigations are ongoing in the South-East Asian outbreaks, there is currently no evidence of human-to-human transmission with the avian influenza A (H5N1) strain.
If AI were to pose a significant threat (direct or indirect) to Australia's human population, the Australian Government would activate the Australian Action Plan for Pandemic Influenza. This plan provides direction for the development of actions by all Australian Governments, their agencies and emergency services in the event of such an occurrence.
Should travellers to Asia take special precautions?
At this stage, Australian travellers are encouraged to avoid contact with live domestic birds (such as chickens, ducks and geese) on farms and in market places. While travelling, it is suggested that you regularly check the Department of Foreign and Trade Travel Bulletin and country specific travel advice for information about any changes to the current situation and whether additional precautions are recommended.
Has avian influenza ever occurred in Australia?
There have been five outbreaks of avian influenza in commercial bird flocks in Australia, all of which were successfully eradicated. The last reported case was in 1997 in Tamworth, NSW. Previous outbreaks occurred in commercial poultry farms in Victoria (1976, 1985 and 1992) and Queensland (1994).
There have been no incidents of avian influenza in humans reported in Australia.
What is Australia doing about avian influenza?
Animal health authorities have had contingency plans in place for many years to minimise the impact of an outbreak of avian influenza in Australia. These procedures are outlined in the Australian Veterinary Emergency Plan (AUSVETPLAN).
Commercial poultry farmers have well-developed biosecurity systems which have been strengthened in recent years. Poultry farmers are on high alert and are backed up by diagnostic facilities and response plans the equal of anywhere in the world.
Australian Government agencies with responsibility for issues such as animal and human health, quarantine and border protection have been closely monitoring and will continue to monitor the current South-East Asian avian influenza situation.
Australian Quarantine Inspection Service (AQIS) officers at airports and international mail centres have been on high alert for bird and poultry products since the first, isolated cases of AI were reported in Asia in October, 2003. (These products - including uncooked poultry meat - are not permitted entry into Australia).
AQIS is screening (Screening can incorporate any combination of the following: X-rays, detector dog inspection or physical opening and checking of luggage) all flights, passengers and baggage from high-risk countries (including: Japan, South Korea, Taiwan, Vietnam, Thailand, China, Laos, Cambodia, Pakistan and Indonesia), with particular attention to eggs, egg products and poultry.
How well prepared is Australia to handle this disease?
Australia is well prepared to handle an outbreak of avian influenza should the disease occur here because of past experience, international connections, linkages with health and well-tested emergency response plans.
The chicken meat and egg industry in Australia has been well aware of reports of avian influenza in Asia for some time.
Their biosecurity arrangements are designed to keep wild birds such as waterfowl away from production birds. Avian influenza can be carried by migratory bird species that could infect wild birds in Australia. It is highly probable that contact between wild birds, particulary ducks, and poultry establishments was the cause of the avian influenza outbreaks in Australia in the past.
We have a technical response plan that has been well tested.
AUSVETPLAN describes what quarantine measures will be put in place should we have an outbreak, that our policy is to stamp out infected birds, it describes the disposal method of carcasses and what sanitary measures are to be adopted at infection sites to contain the disease.
Is it safe to eat chicken?
Yes. It is safe to eat cooked chicken meat and eggs.
What can I do as a poultry owner?
Good biosecurity, so as to maintain a barrier between domestic birds and wild bird populations, is the single most important factor in reducing the risk of an avian influenza outbreak. Apart from preventing contact between wild and domestic birds, the water supply must also be treated, or from a known safe source.
Further advice on biosecurity guidelines for the poultry industry is available from the Rural Industries Research and Development Corporation and WA Department of Agriculture.
People who may only have a few chickens or a bird aviary also have an important role in terms of surveillance for this disease. Community assistance is being sought, particularly from people who keep birds, to be alert to unusual signs of disease and to report this immediately to their local vet, agriculture agency or the animal disease hotline on 1800 675 888.
Early warning will help to bring any outbreak under control more rapidly.
Signs to look for: The disease is difficult to diagnose and clinical signs are variable, depending on the strain of the virus and the age and species of the birds infected. Clinical signs include sudden death, respiratory distress, loss of appetite, purple discolouration of the wattles, combs and legs, coughing and diarrhoea. A consistent finding is a sudden drop in egg production.
What should I do if I suspect an outbreak or have further questions?
Talk to your local vet, the Chief Veterinary Officer (CVO) in your state or territory or call the Hotline: 1800 675 888 (free call from within Australia - Operating hours 8.00 am - 6.00 pm (EST) Monday to Friday. After Hours - recorded message.
By Department of Agriculture and Water Resources - Last updated 16 November 2012
