Mosquito-transmitted virus on the rise

Flood grounds across the region have become a breeding ground for mosquitoes, which carry the potentially deadly Japanese Encephalitis virus. Picture: FILE

South Burnett residents are being asked to mosquito-proof their dwellings, clothing and livestock as a potentially deadly blood-borne virus has emerged in parts of the country following recent flood events, having already claimed the life of one South Australian.

The Japanese Encephalitis virus, which is according to a dossier by Queensland Health the leading cause of childhood brain inflammation in Asia, was discovered in a piggery in south east Queensland earlier this month, sparking a range of questions in the state’s rural population.

Japanese Encephalitis virus – abbreviated as JEv – is a member of the genus of flaviviruses, sharing the label with well-known viruses like Zika, dengue and yellow fever.

Causes and symptoms

The disease is spread through the bite of an infected mosquito, most commonly the common banded mosquito Culex annulirostris, and most frequently affects pigs, wading birds and horses, with the former two acting as the virus’s main vectors.

The virus cannot be spread between humans.

According to a statement by Queensland Health published on 3 March, JEv infection will go largely unnoticed in a vast majority of cases even after its 5- to 15-day incubation period – but the virus still poses major health risks, especially to vulnerable persons.

“Most human infections of JEV cause no symptoms or mild symptoms such as headache or fever,” the statement read.

“A person with severe disease may present with inflammation of the brain, characterised by sudden onset of vomiting, high fever and chills, severe headache, sensitivity to light, neck stiffness and nausea/vomiting.

“Children aged under five years of age and older people who are infected with JEV are at a higher risk of developing more severe illness,” it read.

Queensland Health further advised that the disease can “rapidly progress to a reduced level of consciousness and coma,” and that “seizures may occur” – of these severe cases, “approximately one-third die, and one-third are left with permanent disabilities”.

However, nearly 99 per cent of people infected with the virus show no symptoms.

The virus’s long history

A Queensland Health dossier on Japanese Encephalitis stated that the virus has been recorded in parts of South East Asia and China, having also recently spread to Melanesia and tropical Australia; JEv is reportedly now considered to be endemic to the Torres Strait region and Papua New Guinea.

“There are between 30,000 and 50,000 cases reported annually worldwide with a case fatality rate of between 20 and 30 per cent,” the QLD Health dossier read.

“A further 50-60 per cent of survivors experience long term neurological [consequences].”

The virus made headlines in Australia in 1995 after an outbreak was confirmed in the Torres Strait, killing two, with a second outbreak recorded in 1998.

“Although the JE virus remains exotic to Australia, seasonal incursions of the JE virus have been detected in the Torres Strait every year with the exception of 1999 since 1995,” QLD Health stated.

What to do

While the Japanese Encephalitis virus can spread quickly thanks to its infection of mosquitos and livestock, there is hope in the form of a preventative vaccine.

“Two JE vaccines, each with different characteristics, are available for use in Australia,” QLD Health stated.

“Imojev is registered for use in people from 9 months of age and is given as a single dose. “JEspect is registered for use in individuals aged over 18 years and is given as a two-dose schedule, 28 days apart. The vaccine can be given in pregnancy, if necessary.”

Once infected and symptomatic, however, there is no specific treatment for the disease, with healthcare workers typically attempting to alleviate ongoing symptoms in patients while the disease runs its course.

When it comes to combatting the disease, then, the main strategy is prevention.

“We encourage Queenslanders to take necessary steps to prevent being bitten by mosquitoes, especially given the recent flooding event which may lead to an increase in mosquito numbers in coming weeks,” Queensland Health stated in a notice on 3 March.

“Measures to prevent mosquito bites include regularly applying insect repellent containing Diethyl Toluamide (DEET), Picaridin, or oil of lemon eucalyptus; wearing loose, light-coloured clothing to cover up arms, legs and feet; and using other insecticide-based mosquito control devices where possible when outside.

“Around your home, it’s important to inspect for common mosquito breeding sites, clean up debris and make sure to empty, wipe out and store any outdoor containers in a dry place.

“It’s also important to ensure flyscreens are in good order so mosquitoes can’t enter your home easily,” the government department added.

Despite the virus having been recorded in Australian piggeries, affected livestock are safe to consume.

“Queensland Health is working collaboratively with the Department of Agriculture and Fisheries and industry, as well as state, territory and national counterparts to discuss a national response,” the department stated.

“Support is also being provided to intensive livestock industry workers.”