Scientists develop new vaccine for encephalitis in pigs

Nick Gibbs |

Jessica Harrison and Jody Hobson-Peters (right) hope to save lives and help keep pigs healthy.
Jessica Harrison and Jody Hobson-Peters (right) hope to save lives and help keep pigs healthy.

The spread of Japanese encephalitis in Australia could slow thanks to a new novel vaccine aimed at domesticated pigs.

Severe disease from JEV is rare but potentially fatal in humans, and while it cannot be passed from pigs to people, mosquitoes can act as a pathway.  

“When pigs are bitten by virus-carrying mosquitoes the virus is amplified, increasing the risk to people who may be bitten by a mosquito,” University of Queensland researcher Jody Hobson-Peters says.

“By vaccinating pigs and stopping them from contracting the virus, we’ll help stop this pathway to humans, hopefully saving lives as well as keeping pigs healthy.”

There have been seven deaths among the 46 human cases of JEV notified in Australia since January 2021, according to the federal health department.

Human cases were detected in Victoria, South Australia, NSW and Queensland last year, with the federal government declaring the outbreak a communicable disease incident of national significance.

Two vaccines for humans are approved in Australia but supply has been limited.

The new pig vaccine involved making a hybrid version of the virus using the harmless-to-humans, mosquito-only Binjari virus.

“The resulting chimeric, or hybrid, virus looks identical to JEV but can only grow in mosquito cells and also happens to be dead in this vaccine, so it is very safe to use,” Dr Hobson-Peters said.

“When injected into pigs or other species, the hybrid virus is recognised as JEV by the immune system, which generates antibodies and provides immunity.”

Professor Roy Hall, also from the University of Queensland, said the vaccine performed “extremely well” during recent efficacy trials. 

“More than 90 per cent of the young pigs in the trial were protected from JEV infection and we expect the same in other species like humans and horses,” he said.

Work is now under way with veterinary company Treidlia Biovet to manufacture the vaccine at scale for larger trials. 

“Pending successful outcomes, we hope to roll the vaccine out commercially later in 2023 – a fantastic outcome,” Prof Hall said.

“Australia’s current weather patterns are conducive to its further spread here, so it’s crucial that we have a safe and effective Australian-made vaccine available.”

Researchers hope the vaccine can be further developed for use on humans and a version for horses. 

“This dangerous virus will remain a major health threat to humans and a big problem to the pig and horse industries,” Prof Hall said.