More than a million birds culled already - and still counting

Authorities are racing to contain the Victorian outbreak of highly contagious avian influenza which has already been confirmed at six poultry farms and one commercial duck operation.

It comes after confirmation today (Wednesday) of a bird flu case at a chicken farm on the outskirts of Sydney.

Tests have confirmed the NSW case is the high pathogenicity avian influenza H7N8, different to strain detected in Victoria.

In Victoria, the bird destruction is already more than double the previous "worst" outbreak in 2020 where six Victorian properties were infected across three local government areas.

In that outbreak, three egg farms, two turkey farms and one emu farm were involved with more than 433,000 birds destroyed as a control measure.

The first detection of an H7 HPAI strain of bird flu was confirmed on May 22 at a poultry farm near Meredith, in the Golden Plains Shire of Victoria.

Meredith is today ground zero, and is host to many commercial egg and chickenmeat sheds, and enjoy close proximity to their major markets about an hour to the east of Melbourne.

Best guess so far on how the outbreak was triggered was the virus hitched a ride on wild birds such as waterfowl.

Officials say testing of samples from Victoria's infected farms found the viruses were similar to low pathogenicity avian influenza viruses commonly detected in Australian wild birds.

Previous bird flu outbreaks in Australia were linked to wild birds.

"Wild birds can carry viruses without showing signs of disease," government officials said.

The virus can survive for a long time in droppings, respiratory secretions, water, feathers, eggs and meat hence the need for culling and decontamination of impacted properties which remain under quarantine.

On May 24, Agriculture Victoria's tracing identified a separate H7 HPAI strain on a poultry farm near Terang in the Shire of Corangamite.

The other poultry and duck farms which have had confirmed cases since are all within the Golden Plains Shire.

Impacted farms can be compensated for stock losses under government schemes.

Since 1976, there have been nine outbreaks of bird flu in commercial birds across Australia including Victoria, Queensland and the last in 2013 in NSW.

The 1994 Queensland outbreak saw the destruction of 310,565 chickens.

The 2013 outbreak in NSW resulted in about 450,000 chickens being culled.

"The (Victorian) infected properties have been placed under quarantine and all birds are being humanely disposed of and the sites cleared of the infection," an Agriculture Victoria spokeswoman said.

"This process is carried out under veterinary supervision, consistent with national policies and considering the welfare of the birds and staff."

More than a million birds will be disposed of across the seven properties, with "depopulation" continuing, officials said,

This figure exceeds the previous outbreaks of avian influenza in 2020, where six properties were affected across three local government areas.

All sites will be cleaned and cleared of the infection.