Confirmed: flesh-eating Buruli ulcer spread by mosquitoes

Victorian researchers have solved the 80-year mystery surrounding the spread of Buruli ulcer, a neglected tropical skin disease which has become an important public health issue in Victoria. Their findings, published in the journal Nature Microbiology, categorically confirm mosquitoes as the primary vectors transmitting the ulcer-causing bacteria Mycobacterium ulcerans (M. ulcerans) from the environment to people.

How people contract Buruli ulcer has been a central question that has perplexed scientists ever since the discovery of M. ulcerans in the 1940s, with an alarming surge in cases in and around Melbourne and Geelong over the last two decades — from 12 in 2003 to 363 in 2023. Researchers had long suspected mosquitoes were involved, noted Professor Paul Johnson from Austin Health, but there was no precedence for a bacterial infection like Buruli ulcer to be transmitted this way.

“Our team faced considerable scepticism, so we gathered irrefutable evidence to support our claim,” Johnson said.

Led by The Peter Doherty Institute for Infection and Immunity (Doherty Institute) at The University of Melbourne, the Beating Buruli in Victoria project brought together partners from the Bio21 Institute, Agriculture Victoria, Austin Health, the Victorian Department of Health, the Mornington Peninsular Shire, CSIRO and more. Focusing on the Mornington Peninsula, a seaside region outside of Melbourne with one of the highest incidences of Buruli ulcer in the world, the partners trapped and tested more than 65,000 mosquitoes between 2016 and 2021.

“Thanks to genome sequencing, we discovered that the genetic make-up of the bacteria M. ulcerans in mosquitoes was identical to that found in Buruli ulcer patients in the study area,” said Dr Peter Mee, Research Scientist at Agriculture Victoria.

“This was a key part of a compelling body of evidence pointing to mosquitoes as the transmission link.”

The discovery represents a pivotal and significant advancement in the efforts to curb the spread of Buruli ulcer, which has baffled scientists and public health experts for decades.

“So now that mystery is solved with our five-year study revealing that mosquitoes transmit M. ulcerans in south-eastern Australia, making mosquito bite prevention and mosquito control obvious forms of prevention,” said team leader Professor Tim Stinear, Director of the WHO Collaborating Centre for Mycobacterium ulcerans at the Doherty Institute.

“This research is significant because we can all take simple actions, like applying insect repellent and removing stagnant water around the house, to protect the community and reduce the risk of Buruli ulcer.”

The Beating Buruli in Victoria team is currently in the process of rolling out a new trial aimed at reducing mosquito populations in urban areas, specifically around Brunswick West, Pascoe Vale South, Moonee Ponds and Essendon in Victoria, using state-of-the-art, environmentally friendly mosquito traps. Meanwhile, the Doherty Institute’s Dr Katherine Gibney has stressed the importance of ongoing wildlife and mosquito population monitoring — a ‘One Health’ approach.

“Maintaining this type of mosquito surveillance work could offer crucial insights into the epidemiology of Buruli ulcer in the region and inform public health interventions aimed at controlling the disease,” Gibney said.

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