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Avian influenza
What is it?
Avian influenza is a viral disease that affects birds’ respiratory, digestive and nervous systems. The disease affects many domestic and wild species, including chickens, turkeys, pheasants, partridges, quail, pigeons, ducks, geese, guinea fowl and ostriches.
There are different strains of avian influenza virus that differ in their severity in different species. Wild birds can also carry and spread these viruses without showing signs of disease.
Where is it found?
Avian influenza viruses occur in wild birds worldwide and cause disease outbreaks in domestic poultry at irregular intervals. There was a serious outbreak in the Netherlands in 2003 that spread to Belgium and Germany, affecting about 250 farms and requiring the slaughter of more than 28 million poultry.
A major epidemic in poultry was first reported in Southeast Asia in late 2003 and in 2004 spread rapidly to affect eight countries, resulting in the death or slaughter of more than 120 million poultry and (as at March 2005) the deaths of almost 50 people.
There have been five outbreaks of highly pathogenic avian influenza in commercial poultry flocks in Australia, all of which were successfully eradicated by slaughter, disinfection and movement control policies. The most recent outbreak in Australia was in Tamworth, NSW, in 1997.
What are its effects?
Signs of avian influenza can range from mild illness to a highly contagious and rapidly fatal disease with diarrhoea, lack of appetite, reduced egg production, fragile and mis-shapen eggs, inflammation of the head, eyelids, comb, wattles and hocks, nasal discharge, coughing, sneezing, lack of co-ordination and sudden death.
Signs of disease depend on a number of factors including the age and species of birds affected, husbandry practices, environmental conditions, the presence of pre-existing infections and the strain of virus.
The virus is transmitted through contact with faeces or discharges from the eyes and nostrils of an infected bird. The virus can also be spread by contaminated footwear, clothing, crates, equipment, feed, cages, machinery and the movement of infected birds.
Outbreaks in domestic poultry are generally thought to result from contact with wild birds or contamination of food or water supplies by wild birds. Avian influenza spreads very quickly — infected farms must be quarantined and exposed or infected flocks must be destroyed to prevent its spread.
The virus can remain infective at moderate to low temperatures for long periods in the environment and can persist indefinitely in frozen material.
Infection of humans with avian influenza virus is relatively rare and usually results in mild conjunctivitis; however, infection with some types of avian influenza can be fatal in humans. In all reported cases the affected individuals have had close contact with infected birds.
What’s the risk to Australia?
A major outbreak of avian influenza in Australia would be costly to the poultry industry, consumers, and taxpayers. An outbreak in the United States in 1983-84 required an eradication program that cost close to US$65 million, resulted in the destruction of more than 17 million birds, and caused retail egg prices to increase by more than 30 per cent.
AQIS officers at airports and international mail centres have been on high alert for bird and poultry products since the first, isolated cases of avian influenza were reported in Asia in late 2003.
Quarantine officers screen all flights, passengers, baggage, mail and cargo from high-risk countries using X-ray machines, detector dog inspection and physical inspection. They pay particular attention to eggs, egg products, poultry meat, poultry vaccines, feathers and similar items.
Northern Australia Quarantine Strategy (NAQS) fact sheet on Avian Influenza
Product Integrity/Animal and Plant Health information on Avian Influenza