Avian Influenza

Avian Influenza is more commonly known as ‘bird flu’. It is a highly contagious virus which causes flu-like symptoms, including:

• sudden death
• respiratory distress
• swelling of the head
• coughing
• sneezing
• rasping breathing
• rapid decrease in feed and water intake
• ruffled feathers
• depression
• closed eyes
• diarrhoea
• nervous signs

AI occurs naturally among waterfowl (ducks, geese, swans, gulls, terns, and shorebirds such as storks, plovers and sandpipers) worldwide. Wild birds usually carry the virus without showing any symptoms of the disease.

It can also infect domestic poultry and other bird and animal species. Quail and pheasants are also susceptible to getting AI.

Avian influenza virus strains are designated as low pathogenic (LPAI) or highly pathogenic (HPAI), which means whether birds have no symptoms to mild or severe symptoms.

The high or low designations relate to the potential to cause mortality in infected poultry but doesn’t relate to how infectious the viruses may be to humans, other animals, or other species of birds.

Most strains of AI virus cause minimal disease in wild birds and poultry. However, some LPAI strains can evolve into HPAI strains when they spread among poultry, causing severe disease and death. Sometimes HPAI viruses spill back to wild birds where they may also cause disease or death in certain species and pose a risk of spreading into poultry populations.

Avian Influenza viruses are categorised into subtypes based on their two surface proteins. The H5 and H7 AI virus subtypes pose the greatest potential to evolve into HPAI viruses and are closely monitored by animal health and biosecurity agencies. H5N1 is a particular strain of highly pathogenic avian influenza.

During the past 20 years, HPAI viruses of H7 subtypes have been recognised in wild birds and domestic poultry on numerous isolated occasions in Australia. However, the variant of greatest global concern (H5N1) has not been detected here and our risk for HPAI viruses in Australia is considered low.

Ongoing outbreaks of H5N1 globally have increased our level of risk for incursions of HPAI viruses of global concern. Migratory birds returning to our shores annually between September and November may introduce HPAI viruses.

AI virus is excreted in the saliva, nasal secretions and faeces of infected birds. It is spread between infected birds via close contact, the movement of infected live birds and virus-contaminated poultry products, feed, equipment and materials. The virus can survive long periods in faeces and water and on feathers, eggs or in meat.

In Australia, AI could spread to domestic birds through contamination of feed and water by wild bird droppings or secretions. Infected migratory shore and wading birds could transmit AI to Australian nomadic waterbirds (including ducks), which could mingle with and spread the virus to domestic birds. This can occur through either direct contact between wild and domestic birds, or indirectly through the contamination by wild birds of feed or water of domestic birds.

Occasional outbreaks of internationally notifiable HPAI and LPAI have occurred on poultry farms in Australia.

Each outbreak was quickly detected and stamped out, with only a small number of farms affected.

Annual migration of wild birds has the ongoing potential to introduce new subtypes of AI virus to Australian birds. Waterfowl are thought to have had a role in the spread of the H5N1 virus in Europe, Asia and Africa but they do not normally migrate to Australia. A number of wading bird species do migrate to Australia, but they are not common hosts or spreaders of HPAI viruses. Australia’s strict biosecurity measures prevent the disease from coming into Australia through imported birds or poultry products.

Serious forms of the disease can cause severe symptoms and sudden death in domestic poultry (up to 100 per cent of birds). Mild strains of the disease cause few or no symptoms in poultry and may go undetected in some species of birds, though can result in some deaths.

Domesticated birds (chickens, turkeys, ducks, etc.) may become infected with avian influenza A viruses through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces that have been contaminated with the viruses.

Avian influenza outbreaks in domesticated birds are of concern for several reasons:

• the potential for low pathogenic avian influenza A(H5) and A(H7) viruses to evolve into highly pathogenic avian influenza A(H5) and A(H7) viruses with major agricultural implications
• the potential for rapid spread and significant illness and death among poultry during HPAI outbreaks
• the economic impact and trade restrictions from a highly pathogenic avian influenza outbreak
• the possibility that avian influenza A viruses could be transmitted to humans exposed to infected birds

While the spread of AI from birds to humans is rare, human infections of bird flu can happen when virus gets into a person’s eyes, nose or mouth, or is inhaled. This can happen when virus is in the air, either in droplet form or as possibly dust, and a person breathes it in, or possibly when a person touches something that has virus on it and then touches their mouth, eyes or nose. Human infections with bird flu viruses have occurred most often after unprotected contact with infected birds or surfaces contaminated with bird flu viruses. The virus can survive in bird excrement for over a month and can survive in water for many days, if not weeks, depending on temperature. It is important to know that freezing does not kill the virus.

The H5N1 HPAI can infect humans who come in very close contact with infected birds or their excrement. Most human cases of H5N1 occur in people working closely with birds (e.g. poultry farmers).

AI symptoms in humans can range from tropical flu-like symptoms (e.g. cough, fever, sore throat and muscle aches) to eye infections, with conjunctivitis being the most common sign. Other symptoms can include pneumonia, acute respiratory distress and, in rare cases, death.

Medical advice should be sought immediately if you or anyone you have been in close contact with experience the symptoms noted above after coming into contact with infected or suspect birds. This also applies if you think you have been exposed to other infected materials.

Hunters need to be aware that ducks can carry avian influenza without appearing sick and showing any signs of illness.

The best protection from exposure is to ensure good hygiene is practiced when handling ducks, regardless of them being alive or dead.

As a general precaution, hunters should not harvest, handle or eat birds that look sick or are found dead.

When hunters need to handle waterfowl, they should:

• field dress and prepare game outdoors or in a well-ventilated area
• wear rubber or disposable latex gloves while handling and cleaning game
• when done with handling game, practice good hygiene to prevent any potential disease spread by washing hands thoroughly with soap or disinfectant, and clean knives, equipment and surfaces that come in contact with game
• avoid touching your mouth, eyes, and nose; cover any cuts or grazes with a water resistant dressing under PPE (i.e. band-aid),
• avoid eating, drinking or smoking whilst handling/cleaning birds
• ensure that all game should be thoroughly cooked to an internal temperature of 75 degrees Celsius
• for hunters that are immune-compromised or have a chronic respiratory condition, consider having someone else clean their ducks after hunting to reduce the risk of infection. If this is not possible, they should wear disposable gloves, eye protection and a P2 facemask as a minimum.

Duck hunters can have an important role in detecting and reporting diseases in wild birds.

Australia does not have migratory waterfowl with known flyways. The risk of waterfowl catching AI is posed when they mingle with shore birds and waders that come to Australia from Asia.

In order to mount an effective Australian response, ongoing vigilance and early reporting of signs of the disease is crucial. The immediate reporting of anything unusual, such as large numbers of dead birds, will ensure authorities can contain and eradicate the disease as quickly as possible.

Although H5N1 HPAI has never been detected in wild birds in Australia, several subtypes of LPAI are known to circulate at low levels in waterfowl and shorebird species. These viruses are not believed to cause clinical signs of disease in wild birds.

If you come across a large number of dead birds or any other circumstances that look unusual (e.g. eye or nose discharge or sudden death), you should not handle the birds without the proper PPE. You should then take immediate action. Telephone the national Emergency Animal Disease Watch Hotline on 1800 675 888 (24hrs/7 days). Alternatively, contact the Department of Primary Industries or Agriculture in your state or territory or tell your local veterinarian.

Further information on AI and what you can do to protect yourself from exposure to AI by practicing good hygiene is available from Agriculture Victoria.