In recent years, the number of Victorians contracting the flesh-eating bacteria known as Buruli ulcer has been on the rise. Last year, a record-breaking 363 cases were reported, bringing attention to the urgent need for understanding how this bacterial infection spreads. While it has long been suspected that mosquitoes play a role in the transmission of the disease, new research has finally shed light on the connection between possums, mosquitoes, and the spread of Buruli ulcer.
The research, published in Nature Microbiology, conducted extensive surveys across a 350 km² area of Victoria to identify the key players in the transmission of Buruli ulcer. Blood samples from mosquitoes were collected and analyzed to determine if they were carrying the bacterium Mycobacterium ulcerans. The findings revealed that Aedes notoscriptus, a common backyard mosquito species in Australia, tested positive for the bacteria. This provided the crucial evidence linking the mosquitoes to the spread of Buruli ulcer.
Further investigation using genomic tests confirmed that the bacteria found on these mosquitoes matched the bacteria found in the feces of possums and humans with Buruli ulcer. Geospatial analysis also revealed that the areas where human Buruli ulcer cases occurred overlapped with areas where both mosquitoes and possums that harbor Mycobacterium ulcerans were active. This evidence solidified the connection between the infection in humans, possums, and mosquitoes.
Aedes notoscriptus, also known as the Australian backyard mosquito, was identified as the primary mosquito species responsible for spreading the bacteria. This species lays its eggs in water-containing containers in backyard habitats. Controlling these “backyard” mosquitoes is crucial in reducing the risk of not only Buruli ulcer but also other mosquito-borne diseases like dengue fever.
Reducing the mosquito population requires a multifaceted approach. Eliminating breeding sites, such as potted plant saucers, blocked gutters and drains, unscreened rainwater tanks, and various other containers, is a critical step. These areas should be emptied weekly or discarded. Insecticides can also play a role in controlling mosquitoes, but caution must be exercised to minimize their impact on beneficial insects. Safe insecticides that specifically target water-filled containers have shown promising results.
While controlling and reducing mosquito populations is important, personal protection measures against mosquito bites remain a vital defense. Wearing loose-fitted, long-sleeved shirts, long pants, and covered shoes provides physical protection from mosquitoes. Applying topical insect repellent to exposed skin areas is also highly effective. Repellents containing diethytolumide (DEET), picaridin, or oil of lemon eucalyptus have been proven to safely and effectively repel mosquitoes.
Although the rise in Buruli ulcer cases is a significant health concern, it is crucial not to overlook the broader context of mosquito-borne diseases. Mosquitoes are responsible for transmitting a wide range of illnesses, and combating these diseases requires both individual and collective efforts. Understanding the role of specific mosquito species, like Aedes notoscriptus in the spread of Buruli ulcer, allows for targeted control measures that can ultimately reduce the incidence of this flesh-eating bacteria and protect public health.