“Far North Queensland is now essentially a dengue-free area for the first time in well over 100 years,” says Dr Richard Gair, Director and Public Health Physician, Tropical Public Health Services Cairns.
Short-term releases of Wolbachia mosquitoes were undertaken up to 8 years ago in some communities – monitoring in these areas has shown that Wolbachia has remained in the local mosquitoes during this time, without the need for further releases. Importantly, there has been reduced dengue transmission in these areas, with a 93 per cent reduction in reported dengue cases. It follows the 5-year success of the WMP method in the city of Townsville.
The study, led by WMP Director and Monash University Professor Scott O’Neill, also demonstrates that Wolbachia bacteria can be readily established in mosquito populations, protecting people from the local spread of dengue, without the need for further releases. Professor O’Neill said he was thrilled at the result.
“We’ve seen almost the complete collapse of locally acquired dengue in previously high-risk transmission areas in cities and communities across Australia’s far north, despite imported dengue cases continuing to rise. In fact, local dengue transmission has essentially disappeared from Cairns for the first time since the early 1980s.”
“Importantly, we’ve shown the method can be readily established in local Aedes aegypti mosquito populations using a variety of methods, including direct involvement of school children, householders, community groups and businesses, who assisted with growing and releasing Wolbachia mosquitoes. These releases were over short release durations, ranging from 2 to 22 weeks. After this, the Wolbachia mosquitoes breed with wild mosquitoes so that the percentage of Wolbachia mosquitoes rises and stays high, and the whole population has a reduced ability to transmit viruses like dengue from person to person.” Professor O’Neill said.
Wolbachia mosquitoes were deployed across a total resident population of 165,000 including a staggered deployment in the Cairns region in 2011 to 2017, and into the urban areas of the Cassowary Coast, Charters Towers and Douglas regions in 2016 and 2017.
Ongoing long-term monitoring will establish whether these communities have been ‘dengue-proofed’ and whether the protection extends to other mosquito-borne viruses like those that cause Zika, chikungunya and yellow fever.
This work was supported by residents of Cairns and surrounding communities, the Bill and Melinda Gates Foundation, the Wellcome Trust, the Queensland Government and the Gillespie Family Foundation.
Titled, ‘Establishment of wMel Wolbachia in Aedes aegypti mosquitoes and reduction of local dengue transmission in Cairns and surrounding locations in northern Queensland, Australia’, the paper can be accessed on Gates Open Research.