Beating Buruli in Victoria

The mosquitoes that were collected during previous research activities are being processed to determine how many of them were carrying M. ulcerans. By identifying geographic areas where mosquitoes carrying M. ulcerans are, we can focus our interventions in these higher-risk areas. We are also undertaking sophisticated mosquito genomic modelling to see how far mosquito populations are travelling and spreading M. ulcerans.

Possum faecal (excreta) surveys are continuing across Melbourne, Greater Geelong and the Mornington and Bellarine Peninsulas. Field staff collect possum excreta that are screened for M. ulcerans in the lab. This identifies geographic areas in which the bacteria are being actively shed into the environment by infected possums.

Possum surveillance studies involve monitoring free-ranging possums in parts of Victoria where Buruli ulcer is known to occur. Revisiting these locations at regular intervals will allow long-term monitoring of the progression of Buruli ulcer disease in possums and its impacts on animal welfare.

• A field trial of a new mosquito trap that has direct and knock-on effects on mosquito populations is proposed for the Mornington Peninsula in early 2023, if permits can be secured for their use. Preliminary trials have shown these traps are effective at reducing populations of Aedes notoscriptus, the mosquitoes that transmit Buruli ulcer.

Barwon Health and the CSIRO led this research, with support from the Department of Health, Mornington Peninsula Shire Council, Deakin University, the Doherty Institute, and Agriculture Victoria.

256 Victorians with Buruli ulcer (‘cases’) and 458 without (‘controls’) participated by completing a study questionnaire in 2018–2020. Field surveys were conducted at the properties of 230 study participants, which involved the collection and testing of multiple environmental samples for the presence of M. ulcerans.

The case control and environmental field survey study results identified several factors associated with an increased risk of a person getting Buruli ulcer (i.e. risk factors), and factors associated with a reduced risk of getting the disease (i.e. protective factors):

• Factors that reduce risk of getting Buruli ulcer include: using insect repellent, wearing long sleeves when outdoors, and immediately tending to wounds.
• Factors that can increase the risk for Buruli ulcer include: a property with possums, ponds and certain types of native plants; having an outdoor job (especially one with regular soil contact); and using bore water for bathing or gardening,

Detailed results of the environmental field survey are available here: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0274627.