Australia’s wet, humid summer is leading to a surge in both mosquito populations and the number of Ross River virus cases in humans.
For insect sprayer Dave Ross, he is close to both the problem and the solution.
His sister Michelle caught the virus months ago and has been struck by “excruciating” pain.
Mr Ross has since been working with councils and homeowners to help reduce mosquito numbers and the risk of anyone else getting the virus.
Now with Spider Sprayers in Victoria’s south-east, near an East Gippsland hotspot, it has meant the busiest season of his 15 years in business.
“We’re not taking on any more work. We physically can’t get through the workload at this stage,” he said.
The director of Monash University’s Institute of Vector-Borne Disease, Professor Cameron Simmons, studies how the virus spreads and multiplies.
“Ross River virus really exists in a reservoir of animals, not humans. Most years it’s circulating between a variety of different mammal species,” he said.
While most cases of the virus are asymptomatic, Sale GP David Monash said unpleasant symptoms can develop.
“The classic symptoms of Ross River are a mild rash, joint aches and pains, and a bit of a mild fever,” he said.
“The problem with Ross River fever is the long term consequences. You can get joint damage.”
Sufferers have set up Facebook groups to share their symptoms and how they manage them, with some users describing the fatigue and arthritic pain as “terrible”.
Ross River virus infections have already reached record levels across the country with almost 2,000 cases recorded last year in New South Wales.
Queensland, home of the titular Ross River where the arbovirus was first identified, has recorded 3,533 cases in 2020 and 2021.
Victoria has recorded 448 cases across Victoria — centred on the Bellarine Peninsula, the Surf Coast and East Gippsland — with isolated outbreaks occurring across the state.
Victoria’s executive director for communicable disease, Dr Bruce Bolam, said in a typical year about 200 cases are notified to the department.
In Victoria, councils are responsible for controlling mosquito populations with 12 councils currently participating in the state’s mosquito-borne disease program and receiving funding for mosquito surveillance and vector control.
But controls, using indiscriminate larvicides, are a controversial approach.
“Spraying on public land is always going to be difficult. People have all sorts of different opinions so it’s a really hard one to juggle,” insect sprayer Dave Ross said.
“Gone are the days of mass spraying like they used to do.”
Despite that, the East Gippsland Shire general manager of environment Fiona Weigall said they used some larvicides to combat the Ross River virus they considered endemic across Gippsland Lakes.
“Council monitors a number of breeding locations for the presence of mosquito larvae and manages these areas, as required, with biological larvicides,” she said.
But with the risk of the virus proportionate to population size, Mr Ross said the usual methods of population control have done relatively little.
While spraying has fallen out of popularity, councils have taken to trapping as a way to predict the risk of of an outbreak.
Professor Simmons said despite that, outbreaks rarely occur in the same place.
“The unpredictability of these outbreaks makes effective management difficult, even when we know it’s going to be a wet year,” he said.
But the trapping of mosquitoes also provides an opportunity for a better understanding of the spreader.
“There’s room for much greater research to understand the mosquito species responsible for different outbreaks in different settings,” Professor Simmons said.
“In Victoria I would say it’s relatively poorly understood.”
Unlike seasonal diseases like influenza, the health response to Ross River virus is often on the back foot.
Health authorities have only just issued a warning for Gippsland — despite 79 cases across its six shires.
“The challenge for this particular disease is that it’s episodic,” Professor Simmons said.
“It doesn’t happen every year, so our response is always a reactive response.”
Thank you for seeing this article involving “What’s On in the Geelong Region titled “Ross River virus cases are surging in La Niña conditions and mosquito control needs a silver bullet”. This news update was presented by MyLocalPages as part of our Australian events & what’s on local stories services.
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