- Cases of Buruli ulcer have increased significantly in Victoria in recent years, particularly along the Mornington and Bellarine peninsulas, and the disease is spreading into new geographical areas.
- The disease is not spread person-to-person.
- Australian native possums can be victims of Buruli ulcer too.
- Research has shown that areas where humans are most frequently contracting Buruli ulcer are areas where mosquitoes and possums are most frequently carrying the causative bacteria.
- A new three-year research project commenced in February 2021 through a collaborative partnership between the Victorian Department of Health, the Doherty Institute, Barwon Health, Austin Health, Agriculture Victoria, the University of Melbourne and the Mornington Peninsula Shire, aiming to better understand how Buruli ulcer is transmitted and determine effective ways to reduce and prevent infections.
- The 'Beating Buruli in Victoria' project hopes to actively disrupt disease transmission for the first time and lead to the development of evidence-based policies and guidelines that can help stop the spread of Buruli ulcer around Victoria and even globally.
Beating Buruli research project updates
The hunt for answers to Beat Buruli In Victoria continues.
Results of surveillance surveys, 2018-2020
Field surveys were conducted throughout the Mornington Peninsula during the summer months of 2018/2019 and 2019/2020, when peak transmission of Buruli ulcer is known to occur.
- Possum faecal surveys were conducted between November 2018 and March 2019, with teams of intrepid field staff collecting more than 2,000 possum faecal pellets at 200 metre intervals in a grid format, spanning the region between Portsea, Rosebud and St Andrews
- From weekly visits between November 2019 and March 2020, more than 50,000 mosquitoes were trapped across the same region from 180 defined sites.
The collected possum excreta and mosquitoes were screened by a sensitive laboratory test for the presence of Mycobacterium ulcerans, the bacteria responsible for causing Buruli ulcer.
The interim results from both the possum faecal survey and the mosquito survey were mapped to the Mornington Peninsula region to show those areas where possums and mosquitoes were most commonly harbouring M. ulcerans.
These data revealed a very strong association between areas where possum excreta and mosquitoes are positive for M. ulcerans, and cases of Buruli ulcer in humans. This allows us to identify areas that are likely areas of Buruli ulcer transmission, where targeted mosquito control activities might be most beneficial to protect the communities.
The mosquito surveillance also showed that there are three dominant species in the region that accounted for 75% of all mosquitoes: Aedes notoscriptus (37%), Culex molestus (27%) and Culex australicus (11%). However, only Ae. notoscriptus was positive for M. ulcerans, indicating that mosquito control activities need to focus on this species (see Fig. 1)
Plan for upcoming studies, 2021–2023
Additional federal government funding was secured in 2020 to undertake a targeted mosquito control trial, focused on the ‘hotspot’ areas of the Mornington Peninsula that were identified as having highest risk of Buruli ulcer transmission.
The trial addresses community concerns raised in 2019 around the use of residual harbourage spraying to control adult mosquitoes. The new intervention study and associated control measures are based on well-established mosquito source reduction strategies that don’t involve spraying. Source reduction strategies include:
- Education campaigns to help homeowners reduce potential breeding habitats for container breeding mosquitoes such as Ae. notoscriptus on their properties, for example in roof gutters and around pot plants.
- Use of simple, cost-effective and non-toxic mosquito traps (called Gravitraps) that reduce mosquito numbers in and around homes. Gravitraps are sustainable and non-toxic and have been used worldwide to effectively reduce mosquito numbers.
- Use of commercial, mosquito-specific insect growth regulators such as 'NoMoz' in public drains and backyard mosquito breeding sites including rain-water tanks, septic tanks, ponds and bird baths.
The first step of the source reduction intervention is to conduct a pilot study, beginning in February 2021, to show that the strategy will effectively reduce mosquito numbers on the Mornington Peninsula. The pilot study will involve recruiting approximately 500 households divided into 10 zones across Blairgowrie and Rye. Five of these zones (250 houses) will be classified as intervention zones, where the mosquito source reduction activities outlined above will take place during a four-week period. The remaining five zones (250 houses) will be control zones, where no activities will occur. Comparing mosquito numbers in the two zones will allow us to measure the effectiveness of the intervention.
Phase 2 of the project is scheduled to take place during summer of 2021/2022, with larger-scale mosquito control activities to occur throughout the Mornington and Bellarine peninsulas. The interventions will focus on mosquito source reduction methods, aiming to reduce mosquito breeding sites in stagnant water on private and public land. It will involve a door-to-door program, where members of the study team will help home and business owners in the intervention areas to identify mosquito breeding sites on their property, and then implement steps to reduce mosquito numbers. These methods have been used successfully around the world to reduce mosquito populations, in a sustainable and ecologically friendly way.
The study team is planning to work in partnership with the district councils in all study areas, to ensure that communities within the study areas are fully informed and supportive of the project.
What is Buruli ulcer?
Buruli ulcer (also known as Bairnsdale ulcer) is an infection of skin and soft tissue caused by the bacterium Mycobacterium ulcerans. The toxin made by the bacteria attacks fat cells under the skin, which leads to localised redness and swelling or the formation of a nodule (lump) and then an ulcer.
Although Buruli ulcer is not fatal, the infection requires prolonged antibiotic treatment and often surgery to remove damaged tissue and/or to repair scarring, and can often leave patients with significant cosmetic and sometimes functional damage to limbs.
Buruli ulcer has been reported in 33 countries around the world including rural West Africa, Central Africa, New Guinea, Latin America and tropical regions of Asia.
Buruli ulcer in Victoria – past and present
In Australia, Buruli ulcer most commonly occurs in localised coastal areas of Victoria. The disease emerged dramatically on the Mornington Peninsula in the mid-2000s, beginning with a handful of cases near Sorrento and increasing to between 200-340 cases per year since 2017.
The Mornington and Bellarine peninsulas are associated with the highest number of cases in Victoria (see Fig. 3), however Frankston, Seaford, the South Eastern Bayside suburbs and East Gippsland are also considered to be endemic areas for Buruli ulcer transmission. (See ‘Who is at risk?’ below for more detail about risk areas in Victoria)
Fig. 3: Rates of Buruli ulcer cases in Victoria by local government area, from 1991 to 2020.
In 2019, two new Buruli ulcer cases were identified in Aireys Inlet on the Surf Coast, and another two cases in the Geelong suburb of Belmont. None of the affected people had reportedly travelled to the known endemic areas. This suggests that local transmission of Buruli ulcer may be spreading into new areas.
In February 2021, local transmission of Buruli ulcer was reported in the inner Melbourne suburbs of Essendon, Moonee Ponds and Brunswick West, after genetic analysis of M. ulcerans bacteria isolated from human and possum cases of Buruli ulcers suggested a common source of infection in the area. This is the first non-coastal area in Victoria to be recognised as a potential area of transmission risk.
Over the past few years, Victorian scientists have been conducting intensive research in a search for answers around the puzzling aspects of this condition. Although it's understood that the infection is picked up from the environment, it's not yet known exactly how humans become infected with the bacteria, or where in the environment the bacteria prefer to live. It is not thought to be spread person-to-person.
The ‘Beating Buruli in Victoria’ research project
Victoria's Department of Health (DH) has supported research into how Buruli ulcer is transmitted for more than a decade, including providing funding to refine development of an internationally recognized molecular test that has enabled detection of Buruli ulcer in the environment and earlier diagnosis and treatment. Recognising the infection early is important to minimise complications from this infection.
The ‘Beating Buruli in Victoria’ project received its first National Health and Medical Research grant in 2018, allowing the collaborative partnership established between the Victorian Department of Health, the Doherty Institute, University of Melbourne, Barwon Health, Austin Health, CSIRO, Agriculture Victoria, and the Mornington Peninsula Shire Council, to undertake ambitious and innovative research to better understand how Buruli ulcer is transmitted in Victoria, and to determine effective ways to reduce and prevent human infections.
Additional federal government funding was secured in 2020 to continue the research into this puzzling disease, through a series of epidemiological, field- and laboratory-based studies planned to take place on the Mornington and Bellarine peninsulas between 2021 and 2023. The ‘Beating Buruli in Victoria’ project hopes to actively disrupt disease transmission for the first time and lead to the development of evidence-based policies and guidelines that can help stop the spread of Buruli ulcer around Victoria and even globally.
Previously completed studies under the ‘Beating Buruli in Victoria’ project
Beating Buruli: the case-control study (2018-2020)
The Beating Buruli case control study was the first research component of the overall ‘Beating Buruli in Victoria’ project that investigated a range of risk and protective factors associated with Buruli ulcer.
It used a case control study design which involved asking people with Buruli ulcer (‘cases’) and people without it ('controls') to complete a short questionnaire. Field surveys were also conducted at the properties of study participants where a range of environmental samples were collected and then tested for Mycobacterium ulcerans at the laboratory.
Comparing questionnaire responses and field survey results from both cases and controls, the team were able to identify factors that increase a person's risk for getting Buruli ulcer and factors that can protect against getting the disease.
The study ran for a total of two years from September 2018 to September 2020. Results of this study are currently being prepared for publication.
Who conducted the study?
The study was jointly conducted by Barwon Health and the CSIRO with additional support being provided by the Department of Health and Human Services, Mornington Peninsula Shire Council, Deakin University, University of Melbourne and Agriculture Victoria.
Beating Buruli: the mosquito control study (2018-2020)
Findings from an earlier case-control study conducted in 2004 on the Bellarine Peninsula showed that getting bitten by mosquitoes, as well as gardening, were possible risk factors for getting Buruli ulcer, while wearing insect repellent protected against infection. Further research, including laboratory studies and mapping the distribution of Buruli ulcer lesions in human cases, strengthened the evidence that mosquitoes might play a significant role in transmission.
These findings were the basis for the planned second major research focus of this project, the Beating Buruli mosquito control study which planned to investigate the effect of mosquito control on the transmission of Buruli ulcer. In the planned research study, some areas were to receive an intensive mosquito control program including residual spraying using pyrethroid insecticides. However, the local government and some residents expressed a preference for interventions that did not involve spraying using pyrethroid insecticides, due to concerns around perceived health effects and possible collateral damage to other insect populations (particularly bees).
A decision was made to defer the intervention study to allow development of an alternative study proposal that did not involve residual spraying using pyrethroid insecticides.
Commonly asked questions about Buruli ulcer
What are the symptoms of Buruli ulcer?
Buruli ulcer usually progresses slowly over several weeks. Occasionally it can develop more rapidly. An ulcer may not be initially present. It can occur anywhere on the body but it is most common on exposed areas of the limbs, such as ankles, back of calf, around the knee, or forearms or around the elbow.
- Initially, a spot that looks like a mosquito or spider bite forms on the skin. This can be itchy and is usually painless, however some patients do notice pain. Small skin spots and bites are common but a feature of Buruli ulcer is that it doesn't settle with short courses of standard antibiotics and worsens instead of healing naturally.
- The spot usually gets bigger over days or weeks and may form a crusty, non-healing scab.
- Over time, the nodule (lump) scab turns into a or scab nodule (lump) thenbreaks down to reveal an ulcer, surrounded by a ring of red swelling, that continues to increase in size and is surrounded by a ring of red swelling.
- Sometimes an ulcer does not form, with the infection presenting as persistent localised pain and swelling (cellulitis), thickened or raised flat areas of red skin with pain and fever.
How long does it take for the symptoms of Buruli ulcer to appear?
It is estimated that in Victoria, the average time from exposure to the bacteria to the onset of first symptoms is about four and half months but can range from two to nine months. Cases are diagnosed year-round, however there is usually a peak in diagnoses in Victoria between June and November each year.
How is Buruli ulcer transmitted?
Buruli ulcer is an infection acquired from the environment. It is not yet known exactly how humans become infected with the bacteria, or where in the environment the bacteria prefer to live. The bacteria may enter through broken skin, and both mosquitoes and some water-dwelling insects have been implicated in the transmission pathway (see Fig. 4). Most cases report some form of skin trauma, including insect bites, prior to the development of the lesion. It is not spread person-to-person. The highest risk for infection is during the warmer months, but transmission can occur at any time of the year.
Fig. 4: Life cycle of the Aedes notoscriptus mosquito. In urban areas, Ae. notoscriptus breeds in standing water in containers such as pot plant saucers, bird baths, dog bowls and old tyres, and plants that hold water. The adults readily attack humans throughout the day in shaded areas but also feed during early mornings, evenings and nights. These mosquitoes are present throughout all of Australia, and can spread Murray Valley encephalitis, Ross River and Barmah Forest viruses and dog heartworm, and new data suggest they may also spread Mycobacterium ulcerans, the bacterium responsible for causing Buruli ulcer.
What is the treatment for Buruli ulcer?
Buruli ulcer can be treated with a course of special oral antibiotics. Surgery is sometimes used in combination with antibiotic therapy. Regular dressings are usually required. Complete healing usually takes between three and six months depending on the size of the ulcer.
As ulcers get bigger over time, early diagnosis and effective treatment are important to minimise tissue loss and reduce the time until the ulcer heals.
Who is at risk?
People of any age can get infected. People who live in or visit the affected areas of Victoria (see Fig. 5) are considered at greatest risk.
- The highest risk is associated with the active transmission areas of Rye, Sorrento, Blairgowrie and Tootgarook on the Mornington Peninsula.
- There is a medium risk associated with areas in the Bellarine Peninsula (Ocean Grove, Barwon Heads, Point Lonsdale, Queenscliff), Frankston and Seaford areas.
- There is a low but material risk associated with the rest of the Bellarine and Mornington Peninsula, the South Eastern Bayside suburbs and East Gippsland.
Together, all these areas are considered the endemic parts of Victoria for Buruli ulcer transmission. Buruli ulcer is rare outside these areas. Recent cases from Aireys Inlet on the Surf Coast and the Geelong suburb of Belmont, as well as Essendon, Moonee Ponds and Brunswick West in inner Melbourne, suggest that these may be emerging areas of local transmission, however at present the risk of transmission in these areas is considered low.Fig. 5: Map of Victoria showing high-, medium- and low-risk areas for transmission of Buruli ulcer.
Evidence to date suggests that mosquitoes play a role in the transmission of M. ulcerans. Exposures to contaminated soil or water following outdoor activities have also been identified as possible sources for transmission. Therefore, the best way to prevent infection is through the use of simple precautionary measures.
Suggestions to reduce the risk of infection include:
- Wear gardening gloves, long-sleeved shirts and trousers when gardening or working outdoors.
- Avoid insect bites by using suitable insect repellents and long clothing, especially during the warmer months.
- Protect cuts or abrasions with sticking plasters.
- Promptly wash and cover any scratches or cuts you receive while working outdoors.
See your doctor if you have a skin lesion and mention the possibility of Buruli ulcer.
Advice for health professionals
Early diagnosis is critical to prevent skin and tissue loss - consider the diagnosis in patients with a persistent ulcer, nodule, papule, or oedema and cellulitis, especially on exposed parts of the body.
Follow the guidance in the Chief Health Officer Advisory on diagnosis and testing, making sure to take a dedicated swab or fresh tissue sample reserved for polymerase chain reaction (PCR) testing for the infection.
People of any age can get infected, and symptoms can occur four weeks to nine months after exposure to any endemic area; however, there are very different levels of risk associated with the parts of Victoria that are endemic.
Buruli ulcer is a routine notifiable condition and must be notified to the Department within five days of diagnosis.
Referral for treatment to doctors experienced in the management of this condition is recommended. The current mainstay of treatment is rifampicin-containing combination oral antibiotic therapy. Surgery may be used in combination with antibiotic therapy where indicated.
About the study
For the Victorian public
Buruli ulcer bacteria identified in inner west Melbourne
Possible new transmission areas for Buruli ulcer in Victoria
Reviewed 19 July 2019