Researchers picking apart a marsupial’s faeces have warned a bacterium causing a flesh-eating ulcer is present “beyond doubt” in a NSW coastal town.

Buruli ulcer has been known to occur in Australia since the 1940s, with cases noted in Northern Territory and far-north Queensland.

But a surge in cases in Victoria, where a case is reported nearly every day, combined with its emergence in a southern NSW coastal town have intrigued researchers.

Analysis recently published suggests it has become endemic in the NSW town of Batemans Bay, about 110km south-east of Canberra.

Researchers pored over the coastal town’s only two known cases, reported in 2021 and 2023, as well as picking apart 27 samples of possum poo.

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Possums are thought to be the main reservoir of the ulcer-causing bacteria, while mosquitoes act as an important transmitter to humans.

“The new cases we report here in Batemans Bay could be a harbinger of a disease expansion in NSW similar to Victoria,” the group of Australian researchers said in peer-reviewed journal PLOS Neglected Tropical Diseases.

“The detection of positive possum excreta samples from Batemans Bay establishes beyond doubt that (the bacteria) is present in local possums.”

The bacteria found in Batemans Bay was distinct from the lineage prevalent in the most endemic areas of Victoria, including Melbourne, Geelong and surrounds.

Initially appearing as an insect bite, the lesion typically takes weeks or months to ulcerate.

Early recognition and diagnosis is critical to prevent skin and tissue loss.

If it is left untreated, extensive ulceration and tissue loss can occur.

In one of the Batemans Bay cases, a 94-year-old man’s ring finger was amputated after a large skin lesion with the ulcer-causing bacteria spread.

Researchers said the many similarities in wildlife composition and insect presence between coastal Victoria and southern NSW made it likely NSW health authorities were facing progressive expansion of ulcer-endemic areas.

Questions remain as to why cases in humans are popping up in areas sometimes hundreds of kilometres apart.

The research was led by infectious diseases doctors, pathologists and researchers across Victoria, NSW and the ACT.

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