15 Feb 2019
Beating Buruli in Victoria
A new project is seeking to understand the Buruli ulcer epidemic in the Mornington Peninsula and to interrupt disease transmission for the first time.
By Dr Jane Oliver, University of Melbourne
Buruli ulcer (or ‘Bairnsdale ulcer’) is an invasive soft tissue infection caused by Mycobacterium ulcerans. It can cause lasting cosmetic and functional damage. The infection usually responds to oral antibiotics, however surgery is sometimes necessary. West and Central African countries are inequitably affected. In Australia, Buruli ulcer was first noted in the Bairnsdale area (East Gippsland) in the 1930s. An outbreak occurred on Philip Island in the 1990s, followed by an epidemic on the Bellarine Peninsula. From 2015, the annual number of cases notified to the Victorian Department of Health and Human Services (DHHS) increased 3.2–fold, to 340 cases in 2018, with most cases being residents of, or visitors to, the Mornington Peninsula .
How people become infected with M. ulcerans is not fully understood. Some native Australian animals, including possums (which are ubiquitous on the Mornington Peninsula) can develop Buruli ulcer and excrete the pathogen in their faeces. M. ulcerans has also been detected in biting aquatic insects and adult mosquitoes. Previous research has suggested that there is little to no evidence of person-to-person transmission, and it is deemed highly unlikely. Being bitten by mosquitoes and gardening are both activities which appear to increase the risk of developing Buruli ulcer. Use of insect repellent appears to be protective. Possibly, the Mornington Peninsula epidemic is mediated by people being exposed to infected possum faeces through breaks in their skin, or from receiving bites from mosquitoes (which are contaminated with M. ulcerans; perhaps through exposure to possum faeces or by blood-feeding on infected possums) .
An ambitious new study which aims to determine how Buruli ulcer is transmitted, and how to prevent it, is underway. The Beating Buruli in Victoria study is supported by a substantial National Health and Medical Research grant. This is a collaborative partnership between the Victorian Government Department of Health and Human Services, the Doherty Institute, Barwon Health, Austin Health, CSIRO, Agriculture Victoria, the University of Melbourne, and Mornington Peninsula Shire. The study will run for two years. There are two major components.
The first is a case-control study. Here people with Buruli ulcer (cases) and people who live nearby, but do not have it, (the 'controls') complete a short questionnaire. Field surveys to test for M. ulcerans at participants’ residences are also conducted. Cases and controls are then compared to see what exposures are associated with developing Buruli ulcer.
The second component, the Mosquito Control Study, seeks to disrupt disease transmission. This involves a cluster randomised control trial, where small residential areas are identified and randomly assigned to either 'intervention' or 'control' status. All residents of the study area will receive information about how to reduce their risk of mosquito bites. Mosquito surveillance will be performed. ‘Intervention’ areas will also receive a comprehensive mosquito control program, which uses intensive pesticide administration and mosquito trapping.
Finally, rates of Buruli ulcer among residents of control and intervention areas will be compared to see if the mosquito control program was effective in preventing new cases. The Beating Buruli in Victoria study findings are likely to be of significant importance for preventing and controlling epidemics, both in Australia and overseas.