In recent years, the number of Victorians falling ill with Buruli ulcer, a flesh-eating bacterial infection, has been on the rise. In fact, last year saw the highest number of cases since 2004, with 363 reported infections. Despite its prevalence, the exact method of transmission has remained a mystery. However, groundbreaking research has uncovered the truth: mosquitoes carrying the bacteria become infected by biting possums, and subsequently spread the disease to humans through their bites.
Also known as Bairnsdale ulcer, Buruli ulcer is caused by the bacterium Mycobacterium ulcerans. Initially resembling a simple mosquito bite, the infection progressively evolves over several months into a destructive ulcer, resulting in extensive damage to the affected tissue. While it may start off painless, if left untreated, the ulcer can grow rapidly, earning it its infamous “flesh-eating” label. Fortunately, effective treatment methods exist, such as a course of specific antibiotics lasting six to eight weeks, sometimes accompanied by surgical removal of infected tissue.
Previously, Australian native possums were believed to play a role in the spread of Buruli ulcer, and now, with the latest research, the suspicions regarding mosquitoes have been confirmed. A team of scientists conducted extensive surveys across a 350 km² area of Victoria, collecting mosquitoes and analyzing the specimens to identify the presence of the pathogen. These investigations, outlined in a recent publication in Nature Microbiology, involved tracing the mosquitoes’ contact with infected possums and humans.
Molecular testing revealed that only one species of mosquito, Aedes notoscriptus (commonly known as the Australian backyard mosquito), tested positive for Mycobacterium ulcerans. Genomic tests further reinforced the connection, as the bacteria found on these mosquitoes matched those found in possum feces as well as humans afflicted with Buruli ulcer. Additionally, analysis of mosquito specimens containing blood provided evidence that Aedes notoscriptus feeds on both possums and humans. Geospatial analysis then showed that human cases of Buruli ulcer align with areas where both infected mosquitoes and possums are active.
Control measures to combat the spread of Buruli ulcer should focus on managing mosquito populations, particularly Aedes notoscriptus. By reducing the number of breeding sites for these mosquitoes, the risk of various mosquito-borne diseases, including Buruli ulcer and dengue, can be mitigated. Removing containers that collect water, such as potted plant saucers and unscreened rainwater tanks, and regularly emptying or covering them can significantly reduce mosquito breeding grounds. While the use of insecticides can be effective, caution must be exercised to minimize harm to beneficial insects. However, there are eco-friendly insecticides available for treating water-filled containers, and promising research suggests that mosquito-control methods utilizing mosquitoes themselves to spread insecticides may soon become viable.
While controlling mosquito populations is crucial, personal protection against mosquito bites remains the first line of defense against Buruli ulcer and other mosquito-borne diseases. Wearing loose-fitted, long-sleeved shirts, long pants, and covered shoes can provide physical protection. Additionally, applying insect repellent containing diethyltoluamide (DEET), picaridin, or oil of lemon eucalyptus to all exposed areas of the skin is an effective and safe measure against mosquito bites.
Though the rise in Buruli ulcer cases is undoubtedly concerning, it should not overshadow the numerous other mosquito-borne diseases that pose a threat to public health. Therefore, it is crucial to address the issue comprehensively, focusing on the prevention and control of all these diseases.
The recently conducted research has shed light on the transmission of Buruli ulcer. The role of mosquitoes, specifically Aedes notoscriptus, in transmitting the bacteria from possums to humans has been confirmed. By understanding how the disease spreads, effective measures can be implemented to control the mosquito population and protect individuals from this debilitating infection. However, it is important to remember that Buruli ulcer is just one of many mosquito-borne diseases that necessitate ongoing efforts to safeguard public health.
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