Advances made in beating Buruli ulcer spread across Melbourne
Buruli ulcer – a bacterium first discovered in West Africa and now endemic across Victoria’s Bellarine and Mornington Peninsulas – is in the crosshairs of a team of researchers and public health experts led by the Doherty Institute, identifying prime suspects in the transmission of the skin-eating bacteria.
Buruli ulcer is an infection of the skin and soft tissue by the bacterium, Mycobacterium ulcerans. The bacteria’s toxins attack fat cells under the skin, causing redness and swelling or the formation of a nodule (lump) and then an ulcer.
In the last decade, annual cases in Victoria have increased by 1,000 per cent – with affected people often left with significant cosmetic, and sometimes functional, damage to limbs.
University of Melbourne Professor Tim Stinear, molecular microbiologist at the Institute, leads a world-first transmission intervention study to stop the spread of the bacteria, launched in late 2018. The Beating Buruli in Victoria project includes partnership efforts from Doherty Institute epidemiologists Professor Jodie McVernon and Dr Katherine Gibney, as well as the Victorian Government Department of Health, Mornington Peninsula Shire Council, Barwon Health, Austin Health, CSIRO, AgriBio, and the University of Melbourne.
The project aims to develop evidence-based policies and guidelines to help stop the spread around Victoria and the globe, and actively disrupt disease transmission. It is funded by the National Health and Medical Research Council (NHMRC).
In February 2021, Victoria’s Chief Health Officer Brett Sutton announced new cases of Buruli ulcer had been found in Melbourne’s inner north, the first time a non-coastal region of Melbourne had been affected in recent years.
Interim data from studies undertaken by the Beating Buruli project has been used to advise the Chief Health Officer on the emergence of Buruli ulcer outbreaks.
Professor Stinear said the project’s progress in 2021 focused on investigating a key native Australian animal spreading the bacteria and drawing upon epidemiological tools developed out of the COVID-19 pandemic.
“Australian native possums, including the common eastern ringtail and brushtail possums, are what we call a ‘wildlife reservoir’ species for Mycobacterium ulcerans, the cause of Buruli ulcer. The team’s efforts for 2021 were dedicated to undertaking possum scat surveys, where we collect possum poo at regular intervals in a highly structured survey approach, and then screen them in the lab for the Mycobacterium ulcerans,” says Professor Stinear.
“We’ve demonstrated a clear, positive correlation between areas where possums are carrying the bacteria and humans are getting Buruli ulcer."
“From this data we can build high-resolution maps of where bacteria carrying possums are and, using the same kinds of predictive modelling used for COVID-19, we can build models predicting the geographical risk of humans contracting Buruli.”
“This is a breakthrough, producing a tool that can inform health departments about how to understand and assess the risk of Buruli ulcer in humans.” says Professor Stinear.
While there have been major advances in detecting and treating Buruli ulcer, questions remain about how the disease has spread to humans across Melbourne – now one of the most endemic areas for Buruli ulcer globally.
To answer this question, the Beating Buruli team has also focused on the transmission role of mosquitoes.
“We have been able to establish the percentage of mosquitoes around the Mornington Peninsula carrying mycobacteria S bacterium – and in vector ecology terms, it is considerable,” explains Professor Stinear.
“You can imagine the ways in which possums and mosquitoes could interact in our environment. Our hypothesis is that targeted mosquito control in Buruli ulcer-infected areas will substantially reduce the incidence of disease in humans.
“The Beating Buruli team has consolidated our understanding of the role of possums and mosquitoes in spreading Buruli ulcer in our backyard, and we now have a good handle on the situation to develop suitable tools and interventions to effectively disrupt the spread across Melbourne.”
In a study published in Vaccine, the team reviewed the literature to identify and describe candidate Buruli ulcer vaccines. "Although progress is promising, there remain key questions about the optimal approach to characterising the immunological correlates of protection in humans and strategies to investigate the safety and efficacy of such vaccines in humans."