Modelling predicts hundreds of cases of Buruli ulcer

The discovery of a flesh-eating disease in inner suburban Melbourne comes after modelling suggests Victoria could have hundreds of new infections a year in an epidemic lasting up to 20 years.

Health authorities issued an alert on Tuesday after several cases of Buruli ulcer were identified in the Essendon, Moonee Ponds and Brunswick areas.

While authorities say the risk of getting the infection in these areas is low, it’s the first time non-coastal areas in Victoria have been recognised as a potential source of risk.

The skin infection is caused by a bacterium that leads to lesions on the skin that can look like an insect bite.

Doherty Institute professor Tim Stinear, who leads a joint research project into Buruli ulcer, says the disease is rare, yet Victoria has some of the highest case numbers in the world.

He believes it’s probably because Australia’s native possum is particularly susceptible to the bacteria.

“The bacteria are able to infect it and because we have loads of possums living in and around us, the disease has taken a toehold here in southeast Australia,” Professor Stinear said.

Recent modelling suggests Victoria could experience hundreds of new infections a year, and the epidemic could last 10 to 20 years.

In 2019 there were 299 cases and in 2020 218.

There have been 21 cases so far this year compared with 12 for the same time last year.

“I think we have reason to be – I wouldn’t say alarmed – but really keep an eye on this,” Professor Stinear said.

“That’s why we’re trying to come up with an intervention that will stop it spreading.

“If we do nothing then there is the chance this could spread anywhere in Melbourne, just as we’ve seen in the Essendon northern Melbourne cluster.”

Researchers are trying to understand why Buruli ulcer has moved from coastal areas to inner Melbourne.

The bacteria is found naturally in the environment and, besides being detected in mosquitoes, has also been found in vegetation and possum poo.

The potential source of the bacteria in Melbourne’s inner north has not been established, although the bacteria was isolated from the faeces of a possum.

“What we know is possums carry the bacteria that causes these ulcers, and we know that in areas where the possums have the disease, then humans are likely to get the disease,” Professor Stinear said.

One hypothesis is that possums, which have a natural range of about 100 metres, are being moved around.

“We think something is moving the possums or possum faecal material is being moved, perhaps as well, inadvertently,” Professor Stinear said.

Possums shed the bacteria in their droppings, and if they are moved around, the infection could spread.

The bacteria has been spreading around the Mornington and Bellarine peninsulas for the last 20 years and is now moving towards Melbourne.

“There’s enough bacteria contaminating the wider environment that mosquitoes are then picking up the bacteria and spreading it to people,” Professor Stinear said.

“If we look at what’s happened in other Buruli endemic areas around Melbourne and Geelong, we can see once a bacteria gets into an environment it tends to persist.”

Professor Stinear said researchers were about to start a trial to trap mosquitoes in people’s backyards to reduce numbers to levels that are likely to stop the disease spreading.

The lesions caused by the bacteria are most common on limbs and can be painful.

The bacterium produces a toxin that affects the immune system while continuing to damage tissue.

The good news is that the disease is treatable with antibiotics, with early diagnosis the key.

“The problem is when the diagnosis is delayed that people get the wrong treatments and the disease progresses and you’re left with these terrible ulcers, disfigurements and scarring and lifelong disability,” Professor Stinear said.

The disease does not spread from person to person, and there is no evidence it spreads from possums directly to humans.

People of any age can be infected, but notifications are highest in Victorians aged 60 years and over.

Buruli ulcer must be notified to the state health department within five days of diagnosis.

The number of cases in Victoria varies widely from year to year, but numbers have generally been increasing each year from 2013.

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