The sixth case of Buruli ulcer has been identified in the Batemans Bay-Moruya area of New South Wales (NSW), prompting health authorities to recommend vigilance. This marks the third case recorded this year and the sixth reported in the region since 2021, all attributed to local acquisition. Research indicates that possums act as reservoirs for the bacterium, with mosquitoes serving as vectors for human transmission.
"The Batemans Bay-Moruya area is being identified as a potential new hotspot for the infection."
Case Overview
A sixth case of Buruli ulcer was confirmed in the Batemans Bay-Moruya area of the Southern NSW Local Health District, with notification occurring in February 2024. All six reported cases in the region since 2021, including three in the past year, are considered to have been acquired locally. This trend has led to the Batemans Bay area being identified as a potential new hotspot for the infection.
Understanding Buruli Ulcer
Buruli ulcer is a bacterial infection caused by Mycobacterium ulcerans, which produces a toxin that damages skin and soft tissues. Untreated, the infection can expand, leading to significant skin and muscle damage.
It is informally described as a 'flesh-eating' infection due to its progression.
Symptoms and Progression
Symptoms can appear months after exposure, often beginning as a small, painless lesion resembling a mosquito bite, or a painless lump on the arms, legs, or face. Over days, weeks, or months, this can develop into an ulcer. If untreated, the ulcer can enlarge and affect deeper tissues, potentially including muscle and bone. Symptoms are not always immediately obvious and can manifest without a visible ulcer. Individuals are advised to look for raised or rough skin patches, swelling in a limb, or fever.
Transmission
Research indicates that the bacterium Mycobacterium ulcerans is transmitted from infected possums to humans primarily via mosquito bites. Possums carry the bacterium in their faeces and can also experience similar ulcerous symptoms. Mosquitoes can acquire the bacterium from these droppings or contaminated environments and subsequently transmit it to humans through bites. Genomic testing has established links between the bacteria found in possums, people, and mosquitoes. The Australian backyard mosquito, Aedes notoscriptus, has been identified as a species of particular concern.
Human-to-human transmission has not been observed.
Geographical Presence and Research
Buruli ulcer is reported in over 30 countries globally. In Australia, it has historically been concentrated in Victoria, particularly in coastal areas such as the Mornington Peninsula, Bellarine Peninsula, and Surf Coast, as well as parts of Far North Queensland and the Northern Territory.
NSW reported its first case in 2006, followed by a cluster on the South Coast in 2023. Genomic analysis of NSW cases indicates they are genetically distinct from those prevalent in Victoria, suggesting independent activity in the region rather than a northward spread.
Scientists at the Doherty Institute at the University of Melbourne have developed a new detection tool. Their studies in Victoria, which recorded 426 cases in 2023 and 39 year-to-date, revealed the bacterium in possum faeces in areas with human infections as early as 2010. This research, published in an American Society for Microbiology journal, compared bacterial DNA from possum faeces with that from human cases to confirm local acquisition. This genomic fingerprinting allows for the detection of the bacterium in the environment prior to widespread human outbreaks.
Estimates suggest the bacterium may be present in an area two to six years before the first human cases are observed.
Surveys of possum faeces are considered a potentially more effective approach for identifying new pathogen activity than testing mosquito populations.
Prevention and Treatment
Health authorities advise minimizing the risk of infection by avoiding mosquito bites. Recommended preventative measures include:
- Wearing loose, long-sleeved, light-coloured clothing when outdoors.
- Applying mosquito repellent containing DEET or Picaridin to exposed skin.
- Installing insect screens in homes.
- Regularly checking and emptying containers of still water to minimize mosquito breeding sites.
- Regularly cleaning gutters and drains.
Individuals with non-healing ulcers are advised to seek medical evaluation. Buruli ulcer is treatable with specific oral antibiotics, typically over a course of six to eight weeks.
This treatment demonstrates a nearly 100% cure rate.
Early treatment is crucial for better outcomes. Severe cases may necessitate surgery and skin grafts. The infection can take months to develop after a mosquito bite, with initial symptoms not always visible for several weeks.