A second egg farm near Lethbridge has now also tested positive for H7N7 avian influenza, known as 'bird flu', just a week after the first case was announced on July 31.
Agriculture Victoria said the farm was in the Restricted Area established to contain the first outbreak and regular surveillance had enabled rapid identification and containment of the disease.
The highly contagious disease predominantly affects chickens, ducks, geese, turkeys, guinea fowl, quail, pheasants and ostriches.
Many wild birds, including waterfowl and seabirds, can also carry the virus but positive tests among poultry are rare.
Speaking after the first case, Fish Creek free range egg producer and Victorian Farmers Federation Egg Group past president Meg Parkinson, said the state's last on-farm avian influenza case was detected among ducks in 2012.
She said there was a 2013 case in NSW but it had been 30 years since Victoria had seen an infection in chickens.
Routine government testing of wild birds had shown there were cases in the wild, Ms Parkinson said, and the industry was certain they were the source of the infection, but it wasn't known exactly how the disease was transmitted.
"Recent testing has shown H7N7, so people were on the lookout for it," she said.
"Because it's in the wild birds, there's always a possibility so, as soon as those birds started getting sick, a vet was called."
To date, none of the most dangerous forms of avian influenza have been found in Australian wild birds, according to Wildlife Health Australia, but almost all subtypes have been detected.
Victoria's Chief Veterinary Officer Dr Graeme Cooke said Agriculture Victoria had also placed the second farm under quarantine on Wednesday to enable the depopulation of all infected birds and litter.
"We have completed destruction operations on the first farm and implemented surveillance and movement controls across the region," Dr Cooke said.
"It was these measures that allowed the early detection of the virus on this farm.
"Agricultura Victoria thanks both property owners, vets and others who have been cooperative with this operation."
In a bid to contain the outbreak, Agriculture Victoria has called for all poultry in the area to be housed for at least a month.
"We will be introducing an obligation to house all free-range poultry indoors," Dr Cooke said.
"This applies to commercial operators within the control area. Backyard flock owners must take all practical measures to reduce contact between wild birds and their domestic poultry.
"At this stage of the response we consider it prudent to keep the housing order in place for a minimum of thirty days."
All pigeon races, bird shows and bird sales in the Golden Plains Shire were to be cancelled.
An expanded Restricted Area that provides a buffer zone around the newly identified farm has been put in place. The Controlled area remains the same.
The controls prohibit the movement of poultry, birds, related equipment and products within and out of, the designated Control Area of Golden Plains Shire unless a permit has been granted by Agriculture Victoria until further notice.
"This means all poultry and equipment, including hens, chickens, eggs and manure cannot be sold (including online) or given away at farm-gate, on property or taken to any markets," Dr Cooke said.
"This applies equally to commercial and backyard producers."
Ms Parkinson said the rising popularity of backyard hens presented a threat to commercial poultry operations because they were less aware of biosecurity measures and able to detect an infection.
The greatest risk for spreading infection was soiled boots - as was the case in a NSW outbreak amongst caged hens - but it was possible that wild ducks had entered the free-range enclosure, she said.
"Everybody understands that this is always a possibility, that's why we're so fussy about biosecurity," she said.
Agriculture Victoria will be attempting to contact all nearby bird owners, conducting surveillance on poultry and wild birds and continuing to undertake testing for avian influenza to make sure the disease hasn't spread further.
"If you're a poultry or bird owner within Golden Plains Shire and you haven't heard from Agriculture Victoria since last Friday please call us on (03) 4338 2715 to help our surveillance efforts," Dr Cooke said.
"If you have sick or dead poultry or bids or notice a decline in egg production it is important to immediately notify the Emergency Animal Disease Watch Hotline on 1800 675 888 or your vet.
"That number can also be used to report dead or sick wild birds or waterfowl as part of the National Avian Influenza Wild Bird Surveillance program conducted through Wildlife Health Australia."
The Victorian Department of Health and Human Services confirmed the H7N7 virus is not a risk to the public as it rarely affects humans unless there is direct and close contact with sick birds.
"It's a very rare thing for people to get ill from H7N7," Ms Parkinson said.
"You'd have to be very, very close to the chook, you'd have to be picking them up and cuddling them."
There are no food safety issues identified; properly cooked chicken meat and eggs are safe to eat.
If you have had contact with birds on an affected property and you are experiencing cold or flu symptoms, call your doctor or the Department of Health and Human Services on 1300 651 160 for medical advice.
Signs of the disease may include sudden death, birds with difficulty breathing, and a rapid drop in eating.
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