Highest Number of Flesh Eating Ulcer Cases Recorded in Australian State

Buruli ulcer has been recorded in Victoria over the past two decades, but transmission to humans has increased in recent years. (mycteria/Shutterstock)

Victoria has recorded the highest number of flesh-eating Buruli ulcer cases, with 363 Victorians succumbing to skin infection in 2023.

But most of the recorded cases were not severe.

This comes after Victoria was considered to be one of the most endemic areas for the disease globally, having recorded the third highest case numbers in 2018, after Ghana and Nigeria. It has since become one of the state’s important public health issues.

Buruli ulcer is an infection of the skin that is caused by the bacterium Mycobacterium ulcerans. It usually presents as a developing painless nodule or lump on the arm or leg and ulcerates over a number of weeks. The lump can sometimes be mistaken for an insect bite.

There is evidence showing that mosquitoes and possums have a role in transmitting the infection.

Health authorities say the mosquito-linked condition can be treated with antibiotics, but early diagnosis was vital.

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Anyone living or visiting coastal areas should take precautions against being bitten, Victoria’s Acting Health Minister, Ingrid Stitt, said on Jan. 18.

“Warmer weather provides mosquitoes with an ideal breeding environment,” Ms. Stitt said.

“Victorians should use an insect repellent with DEET, cover up when outdoors, and practice good hygiene by washing new scratches and cuts.”

Coastal areas such as Mornington Peninsula, Frankston municipality, south-eastern Bayside suburbs of Melbourne, and Bellarine Peninsula, have previously been reported to be areas of risk.

However, non-coastal areas of Essendon, Brunswick, and Moonee Ponds have also recorded cases of the disease.

Surveillance by the State

Buruli ulcer has been recorded in Victoria over the past two decades, but transmission to humans has increased in recent years.

In 2018, the “Beating Buruli in Victoria” initiative between the Department of Health, CSIRO, Doherty Institute, University of Melbourne, Barwon Health, Austin Health, Agriculture Victoria, and the Mornington Peninsula Shire Council was launched to determine when and where Buruli ulcer transmission occurs.

For instance, mosquito surveillance conducted on the Mornington Peninsula captured over 60,000 mosquitoes during a four-month period from November 2019 to March 2020.

The research found that three dominant species of mosquitoes in the region accounted for 86 percent of all mosquitoes: Culex molestus (42 percent), Aedes (Ae.) notoscriptus (37 percent), and Culex australicus (7 percent).

Only Aedes notoscriptus consistently tested positive in the laboratory for Mycobacterium ulcerans.

Some of the methods used to control mosquitoes included the residual spraying of pyrethroid insecticides, which reduced mosquito numbers.

However, the combination of mosquito trapping, mosquito breeding source reduction, and community education did not reduce mosquito numbers.

Another method used was “In2Care” traps, which attract mosquitoes using special green ingredients in a bucket. This method reduced mosquito numbers and was used in outer Melbourne in 2022.

Possum faecal matter has also been examined to determine the outbreak of the disease.

“Our data showed that outbreaks of Buruli ulcer coincided with a high number of possums carrying the bacteria. While it is something we’ve been suspecting for a while, this finding categorically confirms the important role of Australian native possums in the transmission of the bacterium to humans,” said Tim Stinear, University of Melbourne professor, and director of the WHO Collaborating Centre for Mycobacterium ulcerans at the Peter Doherty Institute for Infection and Immunity (Doherty Institute).

Symptoms of Buruli Ulcer

Symptoms can take anywhere from four weeks to nine months to display after exposure.

The progression of symptoms can include:

• A spot that looks like a mosquito or spider bite forms on the skin (most commonly on the limbs)
• The spot grows bigger over days or weeks
• The spot may form a crusty, non-healing scab
• The scab then disintegrates into an ulcer
• The ulcer continues to enlarge
• Unlike other ulcers, this ulcer is usually painless and there is generally no fever or other signs of infection
• The infection may sometimes present with no ulceration but with localised pain, swelling and fever, raised lumps, or thickened or raised flat areas of skin

Diagnosis and Treatment of Buruli Ulcer

A Buruli ulcer is usually diagnosed by a doctor, based on a person’s medical history, travel history, physical examination, and testing.

Treatment usually involves a six to eight week course of specific oral antibiotics.

Surgery is sometimes used in combination with antibiotic therapy if required to promote healing.

Prevention

Some suggestions to reduce the risk of infection include:

• Reducing mosquito breeding sites around the house
• 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
• 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
  • Exposed skin contaminated by soil or water should be washed following outdoor activities