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Dengue outbreaks were common in Australia, but this could be a passing trend thanks to research on Wolbachia and the use of genetically bred mosquitoes. Bruno Col recently discussed the efforts being made by the World Mosquito Programme, and we now have a Q&A with Professor Scott O’Neil, for an in-depth account into the use of Wolbachia to control dengue.

Scott O’Neill (PhD FAA FAAAS) is the Director of the Institute of Vector-Borne Disease at Monash University. He leads a large international research collaboration, The Eliminate Dengue Program.

Why release Wolbachia infected Ae. Aegypti mosquitoes into different locations across Australia?

All of our work in Australia has been done in the North Queensland area where the mosquito Aedes aegypti is resident and where there has been regular dengue transmission for many years. Since this was the first-time attempt using this method, we had many different questions we needed to answer about how to deploy it in the best way. In the beginning, we wanted to better understand how well Wolbachia would invade wild mosquito populations and how it would spread.

To do this initial work we chose small isolated communities. Once we had learned from that, we moved our work into more contiguous urban environments to understand how Wolbachia would perform under those conditions. We also wanted to answer questions on what was the minimum size of a deployment area to be successful.

We also had questions to figure out what the best way was to deploy the mosquitoes, such as, how many to release, at what life stage, could the community release them for us. All of these questions were answered in distinct sites in Australia. Finally, when we had answered all the questions we needed to address, we completed deployments into all the areas that had not been covered and that had a history of dengue activity.

Why were these locations chosen?

We chose different locations based on the type of scientific question we were trying to answer from a particular experiment. Ultimately, we ended up covering nearly all the locations in Australia that had a history of dengue outbreaks.

How did you release the mosquitoes?

We used different methods to release, starting with adult mosquito releases. The mosquitoes were held in cups and then released around every 5^th house on the street in the area we were working. We then moved to egg releases where we placed mosquito eggs into a small container with water and food, and the mosquitoes grew in the container and then flew away when they emerged. Finally, we involved the community with the egg release method, where either adults or school children released the eggs around their houses.

How did you measure the establishment of Wolbachia?

We caught wild mosquitoes from our study areas on a regular basis using specialised mosquito traps. We then ran a diagnostic test on them at the lab to work out if they had Wolbachia. In that way we could tell how well the Wolbachia was establishing in the wild mosquito population.

What was the result?

The result showed us that after a relatively short period of release – as little as eight weeks – the Wolbachia would establish, so that nearly all of the wild mosquitoes carried it. Long term monitoring shows that it has stayed in these mosquito populations for nine years to date and shows no sign of diminishing. At the same time, dengue transmission and dengue outbreaks have stopped in Australia. So, what used to be a regular summer occurrence is no longer occurring.

Why is this research important?

It is important because dengue and other viral diseases transmitted by the same mosquito are getting worse and worse around the world, and there seem to be no solutions that are working to stop this worsening problem. This research offers a fairly simple intervention that does not require any spraying of insecticides into the environment and protects communities from these diseases. Not only that, it seems to sustain itself once deployed and as a result is very cost effective.

Why did you decide to publish this on Gates Open Research, via an open research and post publication publishing model?

This platform allowed us to release our results quickly and the open review model made it possible for people to see the peer review process. Most importantly for us, the platform allows us to publish updated versions of the paper. So, as we accumulate more long-term monitoring, we can update these papers to include this information.