source : the age
At first, it looked like an innocuous insect bite on the top of Sarah Fowler’s foot.
The 52-year-old Brunswick woman noticed the small raised bump while staying with her parents on the Mornington Peninsula on New Year’s Day last year.
She went to a GP who prescribed her antibiotics. But the bump kept growing until it looked like a golf ball and her foot began to swell and ache.
Weeks later, a doctor at hospital emergency department diagnosed her with a flesh-eating Buruli ulcer.
Last year, Victoria reported a record-breaking 426 cases of the tissue-destroying ulcer, and more than 100 infections have already been reported this year.
As the state heads into the riskiest months for transmission, the landmark findings of a study from a group of researchers at The Doherty Institute and University of Melbourne could change how Australia halts the spread of the flesh-eating bacteria.
As part of a world-first trial, researchers set up almost 600 specialised eco-friendly mosquito control traps, known as auto-dissemination stations, across transmission hotspots in the Merri-bek and Moonee Valley council areas targeting suburbs in the north-west including Brunswick West, Essendon and Moonee Ponds.
Scientists have long believed mosquitoes are fuelling the spread of the mysterious disease by biting infected possums and then humans.
The skin infection is caused by the bacterium Mycobacterium ulcerans. If it gets under the skin, it can grow and produce a toxin that can melt skin cells and fat.
One of the lead researchers, University of Melbourne medical entomologist Dr Véronique Paris, said control stations were set up in residents’ backyards and in suburban streets to target mosquitoes breeding in small, hidden sources of water around people’s homes.
The black plastic container traps used scent and water to lure in female mosquitoes before coating them in a slow-acting larvicide powder. The insects then unwittingly carried the toxin to surrounding water sources, which could be anywhere from a neighbour’s water tank to roof gutters, killing off mosquito larvae across the entire neighbourhood.
Paris said after eight weeks, between January and March 2024, mosquito egg counts plummeted by about 70 per cent in areas with the traps, effectively suppressing the entire insect population.
“But what surprised us most was the actual impact on the human cases of Buruli ulcer,” Paris said.
After the trial, researchers compared Buruli ulcer cases reported in the six protected zones, which were fitted with the traps, against six nearby untouched “control areas” to measure how well the mosquito stations prevented human infections.
Paris said it was a complex task given it can take many months for Buruli ulcers to develop in the skin after a person is bitten.
Their analysis showed that residents in areas with traps were 83 per cent less likely to contract Buruli ulcers than those in unprotected zones.
Professor Tim Stinear, director of the World Health Organisation Collaborating Centre for Mycobacterium ulcerans at the Doherty Institute, said the findings, published in the Nature Microbiology scientific journal, showed for the first time that reducing mosquito populations could significantly reduce the risk of infection in people.
The microbiologist at the University of Melbourne said the study showed the traps were not only effective at controlling mosquitoes where the control stations were located, but also in surrounding areas.
“We don’t have to kill all mosquitoes, that’s not the message,” Stinear said. “But this trial shows if we can reduce mozzie numbers by simple control measures, then we can measurably reduce transmission risk of the disease.”
Stinear said even adopting simple mosquito control measures at a community level, such as using insect repellent, covering water tanks, installing fly screens and eliminating breeding sites around the home, could reduce the risk of infection.
Sarah Fowler was shocked to discover she had been bitten by a mosquito months before the strange bite even appeared, while she was living in the hotspot of Brunswick West. The antibiotics treated the ulcer – but things got worse before they got better.
“Once you start the antibiotic treatment, it pulls the infection out,” the freelance consultant said.
“There was a hole about the size of a 50¢ piece on my foot full of yellow pus. It was otherworldly looking at my foot and thinking that was on my body.”
Several of her neighbours also had identical ulcers.
Fowler, who now has a large scar on her foot, welcomed the findings of the study.
“It’s great these traps work because it is one of those things where prevention is so important,” she said. “You can’t nip it in the bud once you’ve got it. You have to go through the gruelling cycle of the infection coming out of the wound.”
Director of the Western Public Health Unit in Victoria Dr Finn Romanes said there had been a 350 per cent increase in Buruli ulcer infections in the past five years across the north-west and western suburbs, where the number of cases soared from 35 in 2021 to 123 last year.
“This is very significant and serious infection,” he said. “We still don’t know how it first got in, but it is really clear that it’s spreading from possums through mozzies to humans.”
Romanes said high-risk suburbs grew from 12 last year to 14 this year, with Parkville and Williamstown emerging as new hotspots.
He said the severe ulcer initially manifests as a persistent sore that will not heal, but if it is not treated with antibiotics, the bacteria slowly grows and the wound gets bigger.
He urged people, particularly those living in high-risk areas, to ask their doctor for a swab test if they notice a non-healing sore.
“People can suffer quite significant skin loss or deformity and sometimes even need a skin graft,” he said.
He described the trial’s findings as a “moment of opportunity for public health action”.
“This study describes the real first urban-setting intervention that we know of which prevents transmission across a neighbourhood area,” he said.
The insect traps used in the study are not yet available for purchase in Australia, but regulatory approval for their use is imminent.
Romanes said authorities should explore all options, including using them for pilot schemes or free distribution of the traps to residents in high-risk zones.
There were only 32 cases of the disease in 2010. In 2021, the flesh-eating ulcer spread from the Mornington and Bellarine peninsulas to inner Melbourne and, then in September 2023, a case was identified in Batemans Bay, signalling the leap of the disease to southern NSW.
In 2023, infectious disease experts revealed possums would be vaccinated against the Buruli ulcer to control what they described as an astounding surge of flesh-eating disease across Victoria.
After many years of studying Buruli ulcers, Stinear still found it remarkable that the tropical skin disease was spreading through the suburbs of Melbourne.
“Thirty years ago, we didn’t really know how to detect it, treat it, or how it was spread,” he said.
“Now a group of Australian researchers have answered all of those issues, and we’re moving to a bold place of well, let’s see if we can largely eliminate Buruli ulcer in Victoria.”
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Melissa Cunningham is a health reporter for The Age. She has previously covered crime and justice.Connect via X or email.
