As cases of Buruli ulcer increase yearly across Victoria, a recently published study by a collaboration of researchers from Barwon Health, Deakin University and CSIRO, Australia’s national science agency, has provided another step in understanding how the ulcer is transmitted.
Buruli ulcer (sometimes referred to as the Bairnsdale ulcer) is a skin disease caused by the bacterium Mycobacterium ulcerans.
The toxins made by the bacteria destroy skin cells, small blood vessels and the fat under the skin, which causes ulceration and skin loss. These lesions are usually painless. It is important to know that not all Buruli ulcers appear as ‘ulcers‘ – they can be nodules or red painful swellings of limbs (often called cellulitis).
The ulcer generally gets bigger with time, so early diagnosis and prompt treatment can minimise skin loss and make treatment easier.
Transmission pathways for Buruli ulcer (BU) are not fully understood, therefore to examine protective and risk factors for BU, researchers conducted a comprehensive study of 245 adult BU cases and 481 postcode-matched controls across BU-endemic areas of Victoria.
CSIRO Senior Research Scientist, Dr Kim Blasdell, highlighted that this is the largest study conducted into risk and protective factors for Buruli ulcer to date, encompassing environmental, occupational and behavioural data for people living in these risk areas.
The study found the chance of contracting BU was more than double for individuals with diabetes, and nearly three times higher for those working outdoors with soil contact in known transmission areas (compared to indoor work), but lower among those with reported history of BCG vaccination.
The BCG vaccination provides immunity against tuberculosis (TB) caused by a different mycobacterium, but the results of this study suggest there may also be some protection against Mycobacterium ulcerans – the bacteria causing Buruli ulcer.
BU was also associated with the presence of tea trees, ponds, bore water and increasing numbers of possums at locations.
The study also backed the effectiveness of prevention precautions such as applying insect repellent, covering arms and legs outdoors and immediately washing wounds, and found undertaking multiple of these protective behaviours was associated with the lowest odds of acquiring BU.
Cases of Buruli ulcer have increased significantly in Victoria in recent years, particularly along the Mornington and Bellarine peninsulas, and more recently along the Surf Coast and several suburbs of Greater Geelong, including Belmont, Highton, Wandana Heights, Newtown, Grovedale and Marshall, and parts of inner Melbourne, including Essendon, Moonee Ponds, Brunswick West, Pascoe Vale South and Strathmore.
Barwon South West Public Health Unit Epidemiologist, Bridgette McNamara said the study provides clinicians with more evidence that simple prevention steps can help minimise the risk of BU.
“Research has shown that areas where humans are most frequently contracting Buruli ulcer are areas where possums, soil, and mosquitoes are found to be carrying the causative bacteria.
“Our data show that there are groups at increased risk of Buruli ulcer including those working outside with soil contact and those with health conditions such as diabetes.
“This study provides the evidence for what we have been recommending in terms of minimising risk and helping to prevent transmission for the whole community,” she says.
The following precautions can reduce your risk:
- When gardening, working or spending time outdoors:
- Wear gardening gloves, long sleeved shirts and trousers
- Wear insect repellent on any exposed skin
- Protect cuts and abrasions with a dressing
- Promptly wash any new scratches or cuts you receive with soap and apply a topical antiseptic and dressing.
- Reduce mosquito breeding sites around houses and other accommodation by reducing areas where water can pool (including pot plant containers, buckets, open tins or cans, discarded tyres, and other untreated, freshwater pools).
- Mosquito proof your home by securing insect screens on accommodation.
- Avoid mosquito bites by:
- Using personal insect repellents containing diethyltoluamide (DEET) or picaridin
- Covering up by wearing long, loose-fitting, light-coloured clothing
- Avoiding mosquito-prone areas and vector biting times, especially at dusk and dawn.
- Exposed skin contaminated by soil or water should be washed following outdoor activities.
- See your doctor early if you have a slow-healing or suspicious skin lesion.
For more information on Buruli ulcer, click here.