Australia's biggest pork producer SunPork has confirmed its piggeries have been impacted by Japanese encephalitis virus.
JEV is a mosquito-borne viral disease that is spread through the bite of an infected mosquito to people and animals - mostly pigs and horses.
SunPork Group CEO and managing director Dr Robert van Barneveld said several of their sites in the eastern states had been impacted and they were working through it.
"One of the Goondiwindi farms has been infected ... we have an infected premises in New South Wales ... There are infected premises all down the east coast," Dr van Barneveld said.
"We've been working on this endlessly since Friday night when we first were made aware that it was an issue."
Dr van Barneveld said it was not a new occurrence and there was no cause for alarm in the pork industry.
"The piggeries are innocent bystanders. Pigs are not going to infect other pigs. It's not going to have a negative effect at an abattoir. The pork is safe to eat. It's play on," he said.
"If you're going to have an emergency animal disease, this is the one to have. We're not actually anticipating any significant disruption to our operations at all."
Pigs are the focus from a human health perspective as they can infect mosquitoes that can then infect humans. This is not the case with horses.
Humans can become infected with JEV through the bite of an infected mosquito. The virus cannot be transmitted between humans, and it cannot be caught through eating pork or pig products.
"If a mosquito bites people and if it bites horses, they're called dead end hosts, so it doesn't pass on. If it bites a pig - a pig's an amplifier - so if another mosquito bites that pig while it's viremic, which is a very short period of time, it can transmit in the mosquito population," Dr van Barneveld said.
"That's why there are controls around the movement of pigs."
Dr van Barneveld said authorities were working well together to protect humans and animals.
"This is about protecting people and the bad guy in the process is a mosquito and the weather patterns," he said.
"The state health departments and the state chief veterinary officers have worked extremely well together. They understand that eradicating it is going to be very unlikely and they're being very practical around the movement of pigs and making sure people are safe."
He said SunPork had done a lot of preparedness work around African Swine Fever and had good relationships with the state chief veterinary officers which puts it in a very good position to manage this.
"When you get a disease like this, there are a whole stack of legislative instruments that are pushed into place that have to be executed, and they're following those processes.
"Everyone's fairly calm about it and think we can manage through it with minimal disruption."
A vaccine for horses and pigs is available in countries where the disease is endemic, but no JE vaccines for animals are registered for use in Australia, and there is no effective treatment for JE in animals.
On Friday, Australia's Chief Veterinary Officer Dr Mark Schipp said JEV had been confirmed at 14 piggeries across NSW, SA, Queensland and Victoria.
This follows a confirmed human case of JEV in Queensland. Queensland Health said the confirmed case had recent travel in regional southern Queensland and is currently being treated in a Brisbane hospital.
Less than 1 per cent of people infected may develop a serious illness such as encephalitis and experience symptoms including neck stiffness, severe headache and coma, and more rarely, permanent neurological complications or death.
Goondiwindi and District Veterinary Services owner and vet Dr Trisha Pullos said the recent heavy rain in parts of Queensland and NSW had brought with it more mosquitoes and potentially more risk of JEV.
"We've had quite a bit of rain like everybody else, and the mozzies out here are brutal," Dr Pullos said.
Dr Pullos said the main issues were observed in piglets - pigs didn't seem to be affected physically.
"If the piglets are born dead or weak or malformed or something really unusual or if the sow aborts the whole litter - that's the first sign," she said.
"Pigs can amplify the virus. It's not transferable between humans; it seems to be just the mosquitoes that are how we can catch it, so if you can keep the mozzies off you, then we'll be a little bit safer."
She said it was important to get information from reliable sources and anyone who was worried should contact their vet.
"Anybody who's got two pigs in the backyard, or a pig for the kids, or a little kill herd at the back of the property - they need to contact their local vet and just say, 'Hey, I've got two pigs here. What do I need to keep an eye out for?'
"Then what we'll do is we'll let our district vet know who will then let the Chief Veterinary Officer know so we can try and track it a lot faster, because if someone goes and tells their neighbour but doesn't tell the vet then we're already behind the eight ball."
She said there was a risk people had 'bad news fatigue' and wouldn't take things seriously.
"I've found that everyone's a little bit worn out. There's been quite a few comments on our Facebook posts where people are just like, 'Not again', or 'What now?' 'Can it just end?
"We might be at risk of going, 'Oh, whatever', and I want to make sure that they're not going to do that."
JEV was detected in three people in the Torres Strait Islands in 1995. In 1998, two further cases were detected in people in Queensland, including one acquired on the Australian mainland.
JEV is mostly transmitted by bites from infected mosquito vectors and is maintained in mosquito-waterbird or mosquito-waterbird-pig cycles.
Waterbirds, particularly wading birds such as herons and egrets, are the main source from which transmission of JEV can occur. They are important amplifying hosts and hold enough virus in their blood to infect vectors for one to seven days.
Pigs are also major amplifiers of the virus and develop levels of virus in the blood sufficient to infect vectors for around four days.
Horses and a wide range of other species may be infected but do not develop levels of virus in the blood sufficient to infect mosquitoes, so are not involved in maintaining disease in an area.
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