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MONITORING MOSQUITOES TO PREVENT DISEASE TRANSMISSION

During 2016, AITHM vector control researcher, Professor Scott Ritchie worked in collaboration with Verily Life Sciences (an Alphabet company and Google affiliate) and CSIRO to study the behaviour of male Aedes aegypti mosquitoes in Far North Queensland and identify ways to reduce the wild population of these mosquitoes, preventing transmission of diseases like dengue and Zika and enhancing Australia’s biosecurity.

The research uses the male mosquito, which doesn’t bite and feeds off nectar, to reduce or remove populations of this disease-carrying mosquito species in large urban landscapes. Researchers investigated the behaviour of the male Aedes aegypti mosquito using a mark, release, recapture (MRR) study. After community engagement and support, the study released approximately 1000 male Aedes aegypti mosquitoes, marked with a dye to identify them for recapture, on 16 and 25 November and 5 December in small identified neighbourhood study sites. They were then recaptured through a network of 70 traps to see where they had travelled, how far, what time, and if they had mated with local female Aedes aegypti in that time. Initial results of the MRR Study revealed that, on average, the male mosquitoes flew less than 100 metres, although some flew up to twice that distance. The study found that the released males mated quickly, within the first two days of release. The females, marked with the dye transferred from the males when they mated, were found across the trap network the following week.

The long-term goal of the research is to show that the invasive Aedes aegypti mosquito can be suppressed, and even removed, from the urban landscape. In 2017, the research collaboration intends to carry out further studies in Innisfail which will involve releasing sterile male mosquitoes and testing mosquito production and release tools. This research will allow researchers to see how sterile male mosquitoes behave in the urban environment, and how well they compete with wild Aedes aegypti males for a mate.

These studies will only proceed after extensive engagement with, and support from, the Innisfail community, and with government regulatory approval. This next stage is supported by tools that Verily’s engineers are developing in their laboratories in the United States of America (USA). The JCU cages are being used for experiments to help develop and evaluate a Sterile Insect Technology (SIT) for mosquito population control. The most compelling method for sterilising males is through use of a natural bacterium called Wolbachia. In contrast to the Eliminate Dengue project, which releases male and female Wolbachia infected mosquitoes that are unable to transmit diseases into the wild mosquito population, the SIT method aims to reduce or remove mosquitoes that transmit diseases by releasing sterile male mosquitoes only. The Aedes aegypti mosquito can be infected with Wolbachia by mating them with mosquitoes already infected with the bacterium. Wolbachia is then passed on to the next generation of mosquitoes in the lab rearing process. When males carrying Wolbachia mate with uninfected females, her eggs won’t hatch, limiting numbers of next generation Aedes aegypti. Researchers around the world are currently trialling Wolbachia-based sterile insect technology, including in the US, China, Malaysia and Singapore.

By combining knowledge of mosquito populations and behaviour with Verily’s technologies, this research collaboration aims to reduce or remove the invasive mosquito species from urban landscapes around the world where it spreads diseases, including dengue and Zika.