Australia could face “a major human outbreak” of the mosquito-borne disease Japanese encephalitis in the coming months, amid fears of a vaccine shortage.
There have been 31 confirmed human cases and six deaths so far this year, and the virus may be endemic to Australia, said researchers at the QIMR Berghofer Medical Research Institute in Brisbane.
About 99 percent of cases are asymptomatic, but some people experience dangerous infections that can cause serious symptoms, including brain swelling, convulsions, paralysis, and coma.
QIMR Berghofer researchers say a third consecutive La Nina has likely created new wetlands where the virus-carrying Culex annulirostris mosquito can breed, increasing the chances of the virus spreading to humans, pigs and wetland birds.
There have been 31 confirmed cases of Japanese encephalitis in humans so far this year, which is transmitted by mosquitoes (pictured), and so far there have been six deaths and the virus may be endemic to Australia
Commercial swine outbreaks (pictured) could endanger anyone living within 4km – up to 740,546 people according to recent models – if bitten by a mosquito
Commercial swine outbreaks could put anyone living within a four-mile radius — which can reach up to 740,546 people — at risk of contracting the Japanese encephalitis virus if bitten by mosquitoes, according to a model published Thursday in the journal Clinical Infectious Diseases. from Oxford Academic.
Study author, associate professor Greg Devine, said Australians living near populations of wading birds are also at risk.
“We are very concerned about further outbreaks of Japanese encephalitis in Australia because of this third consecutive year of La Nina,” said Prof. Devine.
‘The wet and warm weather creates the right environment for mosquitoes to spread and could encourage changes in the distribution of the wild birds that sustain the virus during Australia’s winter months.
“Most Australians have not been exposed to the virus before, so they have no immunity. We urge people to take precautions.”
The good news is that there are effective vaccines for Japanese encephalitis, but Australia “probably don’t have enough” if a significant response is needed.
“If you look at a worst-case scenario, there are a lot more people who need a vaccination than we have doses of vaccine,” said Prof. Devine.
The Victorian government has announced $6.5 million in health protection measures, including free vaccines for people in flooded areas.
A special system will also be set up to monitor and control disease-carrying mosquitoes.
The disease can cause serious symptoms, including brain swelling, paralysis, and coma
There are vaccines against Japanese encephalitis, but Australia “probably doesn’t have enough,” experts warn. Pictured is a stock photo of a health professional drawing a dose of a vaccine
NSW is also expanding free access to vaccines for residents of affected regional areas.
Research is underway to increase the number of vaccinations that can be delivered per vaccine dose.
‘Fractional dosing’ means giving a smaller dose to more people, and has been done before for yellow fever and rabies outbreaks around the world.
“There are some contingencies that are possible if we really need to ramp up vaccination drastically,” said Prof. Devine.
Researchers also don’t know the role of feral pigs in the spread of Japanese encephalitis.
‘In terms of domestic pig houses, Australia has about two and a half million pigs at a time. But we also have an equal number, if not more, of wild pigs and they are equally susceptible to viruses,” said Prof. Devine.
Associate Professor Ricardo Soares Magalhães, of the University of Queensland, said Japanese encephalitis was devastating to swine pigs. Pictured are mosquitoes in a research lab
Associate professor Laith Yakob, an epidemiologist at the London School of Hygiene and Tropical Medicine, said the modeling will help authorities determine the number of vaccine doses needed to cope with a major outbreak.
“The models also help us identify locations for enhanced surveillance efforts to better protect Australian residents in future mosquito seasons,” said Professor Yakob.
Fellow study author Associate Professor Ricardo Soares Magalhães, of the University of Queensland, said Japanese encephalitis was devastating to commercial pig houses, causing abortions and stillbirths.
There is no vaccine available for pigs yet, so farmers are trying to protect herds from mosquitoes.
Most horses are asymptomatic when they contract the virus, but the death rate among those who develop symptoms, especially foals, is about 50 percent.