Pascal Debrunner/Unsplash
With our summer season dominated by moist climate and booming mosquito populations, well being authorities have been alert to the specter of mosquito-borne illness.
One such illness is Japanese encephalitis virus, which has been detected for the primary time in southeastern Australia. It has been present in pigs at pig farms in Victoria, New South Wales and Queensland, indicating the virus is probably going circulating within the native mosquito populations, which might infect people.
Ongoing rain and flooding ensures appropriate situations for mosquitoes will persist properly into Autumn.
What’s Japanese encephalitis virus?
Japanese encephalitis virus is a part of the flavivirus household, carefully associated to West Nile, Zika, Murray Valley encephalitis, dengue and yellow fever.
An estimated 68,000 circumstances of encephalitis happen yearly throughout Southeast Asia and Western Pacific areas.
The virus is maintained in a cycle between mosquitoes and waterbirds. Pigs are additionally an essential host, particularly the place pigs, mosquitoes, waterbirds, and water our bodies all happen collectively.
Outbreaks usually tend to happen throughout the moist season.
Learn extra:
La Niña will give us a moist summer season. That is nice climate for mozzies
How critical is Japanese encephalitis?
Most contaminated individuals have gentle sickness or no signs in any respect. Signs of fever, joint ache, and rash are frequent however extreme circumstances additionally expertise headache, neck stiffness, confusion, seizures, and typically coma and dying.
Lower than 1% of these contaminated will develop a extreme mind an infection, encephalitis, which can be deadly.
The illness is especially problematic in youngsters, with survivors typically left with important mind accidents.
To verify an infection, cerebrospinal fluid (that surrounds the mind and spinal wire) and blood are examined by specialised public well being laboratory.
Culex annulirostris is the more than likely mosquito to be transmitting Japanese encephalitis virus in Australia and is widespread and plentiful after flooding.
Cameron Webb/NSW Well being Pathology
Why has Japanese encephalitis virus appeared in Australia?
Outbreaks of Japanese encephalitis virus have occurred in nations neighbouring Australia’s north, together with Papua New Guinea and Indonesia.
Concern has typically been raised concerning the potential introduction and unfold of the virus onto the Australian mainland, given the excessive populations of mosquitoes, wild pigs and waterbirds within the north.
Throughout outbreaks of Japanese encephalitis virus in Torres Strait throughout the Nineteen Nineties, the virus even unfold to the Cape York Peninsula. However the virus didn’t take maintain and the final definitive proof of exercise on the mainland was in 2004.
Now the virus is again. A brand new incursion occurred in early 2021, when a human case was recognized within the Northern Territory.
Now there’s proof of Japanese encephalitis virus in pigs in a number of pig farms in New South Wales, Victoria and Queensland. And there’s a danger of transmission to people.
How did the virus make its method south?
Investigations are underway to work out how a lot virus is within the area and assess the continuing danger to human and animal well being. However we’ll by no means definitively know the way (or when) the virus managed to maneuver south.
It may very well be linked to overlapping transmission cycles fuelled by beneficial climate situations that convey water to flood plains, wetlands, and different habitats shared by mosquitoes and waterbirds. Or it may very well be because of migration of contaminated birds or mosquitoes.
There may be little doubt the La Nina-dominated climate patterns that impacted southeastern Australia over the previous two years performed a job.
The unfold of mosquito-borne viruses, resembling Murray Valley encephalitis virus, from northern Australia to southeastern Australia has been documented earlier than. We simply by no means anticipated Japanese encephalitis virus to take this pathway too.
La Nina has introduced above common rainfall to a lot of Australia and flooding has supplied supreme situations for native mosquitoes.
Cameron Webb/NSW Well being Pathology
How are you going to keep away from catching Japanese encephalitis virus?
A vaccine is out there to guard in opposition to Japanese encephalitis virus. This has been demonstrated as an efficient strategy to stop illness outbreaks.
Some Australians have been vaccinated however it hasn’t been a routine a part of worldwide journey, even to nations the place the danger is excessive.
Consideration may very well be given to vaccinating at-risk teams in Australia.
Decreasing additional transmission of the virus to individuals will depend on using pesticides round high-risk places, resembling piggeries the place infections have been recognized, and using private safety measures in opposition to mosquito bites.
Happily, the steps we routinely take to keep away from mosquitoes bites throughout the Australian summer season will work simply as properly in opposition to the mosquitoes more likely to be carrying the virus. Folks simply have to be extra vigilant to guard themselves and household in opposition to mosquito bites.
Learn extra:
Mozzies biting? Here is how to decide on a repellent (and tips on how to use it for the very best safety)
Well being authorities are recommending numerous steps to keep away from mosquito bites. Minimimse time outdoor when mosquitoes are most energetic, particularly daybreak and nightfall. Put on an extended sleeved shirt, lengthy pants and lined sneakers. Apply a topical insect repellent containing Diethyltolumide, picaridin, or oil of lemon eucalyptus.
The climate has clearly contributed to this outbreak however it might additionally help ending it. The onset of cooler climate in autumn will gradual mosquito inhabitants development and as soon as winter arrives, many of the mosquitoes throughout southern areas of Australia will disappear. Not less than for a couple of months.
Cameron Webb and the Division of Medical Entomology, NSW Well being Pathology, have been engaged by a variety of insect repellent and insecticide producers to offer testing of merchandise and supply skilled recommendation on mosquito biology. Cameron has additionally obtained funding from native, state and federal companies to undertake analysis into mosquito-borne illness surveillance and administration.
Andrew van den Hurk has obtained funding from native, state and federal companies to review the ecology of mosquito-borne pathogens, and their surveillance and management. He’s an worker of the Division of Well being, Queensland Authorities.
Dominic Dwyer doesn’t work for, seek the advice of, personal shares in or obtain funding from any firm or organisation that might profit from this text, and has disclosed no related affiliations past their educational appointment.
