Farmers fear uncontrolled feral pigs will help spread a rare but serious mosquito-borne virus detected in three states.
Biosecurity Queensland confirmed the detection of Japanese encephalitis virus (JEV) at two southern Queensland piggeries earlier this week, noting there have also been recent detections in NSW and Victoria.
There are concerns the arrival of wet season rains has created the perfect breeding conditions for two key carriers of the disease — mosquitoes and feral pigs.
Geoff Penton says letting feral pig populations boom could pose a real risk to humans. (Supplied: Desert Channels Queensland)
Outback conservation group Desert Channels Queensland operations manager Geoff Penton said it put northern Queensland at risk.
“All it takes is a mosquito to have bitten one of those pigs that have been detected with JEV then sting a feral pig out in the wild,” he said.
“The more opportunity there is for those mosquitoes to get into feral pigs … the more chance it has to continue to spread.”
He said there were concerns the animals could become “reservoirs” of the virus, which can be spread to humans through mosquito bites.
“Japanese encephalitis has been known to be fatal to humans in extreme cases,” he said.
“It’s pretty serious … we need to look at our efforts to reduce feral pig numbers.”
JEV has recently been detected in two piggeries in southern Queensland. (Unsplash: Steven Weeks; licence)
It is the first time JEV has been found in animals in Queensland since 2022, when the detections in more than 80 piggeries across four states prompted an emergency health response.
By the end of the outbreak a year later, federal health authorities said 45 people had been infected and seven had died.
Most JEV infections are mild — the World Health Organisation estimates only 1 250 become severe illness — but there can be lifelong health issues for those who survive a serious case.
Feral pigs ‘propelling’ spread
Prior to the 2022 outbreak, JEV was thought to be limited to seasonal transmission in northern Australia, but the federal Department of Agriculture now considers it established on the mainland.
Quantifying feral pigs’ potential to spread disease can be difficult due to a lack of reliable population data, but virologist Dr Jody Peters said there was no doubt they played a role.
Jody Peters says feral pigs pose a major threat to the spread of JEV. (Supplied: Jody Peters)
“What is probably propelling the incidence, or the circulation of this virus, is our huge feral pig population,”
she said.
An associate professor at the University of Queensland’s School of Chemistry and Molecular Biosciences, she said the natural transmission cycle of the mosquito-borne virus typically involved pigs.
“As well as humans getting the JEV vaccine, mosquito management and wild pig management may, from a biodiversity perspective, be the way forward,” she said.
Japanese encephalitis virus has been declared a disease of national significance. (Flickr: Gilles San Martin; licence)
While work on a vaccine to protect animals from the virus continued, Dr Peters said people who work or live near piggeries, or hunt kangaroos and pigs, should take extra precaution to prevent bites and consider vaccination.
Northern exposure
Along with the threat to human health, JEV can cause reproductive losses in pigs and illness in horses and birds.
It cannot be transmitted through meat or from person to person.
But North West Queensland cattle producer a Lloyd Hick said it was still a real threat to the livestock industry.
Lloyd Hick says feral pig numbers are at the highest he has seen. (Supplied: Lloyd Hicks)
“Once these diseases get into uncontrolled herds of any feral animals there’s the risk of it spreading,”
he said.
“We never really know where it may end up.
“There’s a real risk of this potentially being another issue for people on the land.”
Mr Hick, who is also the chairman of farm industry group AgForce’s cattle board, said it was a reminder strong action was needed to control feral pig populations.
“[We] need to start to really find a way to cull those numbers down … we need to put a break in that cycle,” he said.
