In the United States, Google’s (now Alphabet) Debug initiative has asked the federal government for permission to release up to 32 million sterilised male mosquitoes in California and Florida.
By Nigel Beebe for The Conversation
Male mosquitoes don’t bite or carry disease. The hope is these millions of male mosquitoes will mate with disease-carrying females, the eggs won’t hatch, and mosquito numbers will fall.
Unsurprisingly, the US public has questions about the plan, including whether the release is safe and will work at scale, and what happens afterwards. Google/Alphabet’s plan is to release more than 16 million mozzies each year, for two years.
More than a decade ago, I led a project with Google’s life sciences division, (now known as Verily), to test a novel mosquito-control strategy in far north Queensland.
The results showed releasing specially bred male mosquitoes can dramatically suppress populations of the exotic, invasive mosquito species Aedes aegypti. This species is responsible for spreading deadly diseases such as dengue, Zika, chikungunya and yellow fever. Given the US is seriously considering this approach, our Australian experience offers important lessons.
Using mosquitoes against themselves
This story begins in 2015, when we travelled to Silicon Valley to meet Verily scientists interested in developing a mosquito suppression technology. Their goals aligned closely with our own research, supported by an Australian National Health and Medical Research Council grant, to develop environmentally friendly tools for suppressing invasive mosquitoes.
The strategy focuses on male mosquitoes because they don’t bite, and female Aedes aegypti, which generally only mate once during their lifetime. If that mating event was incompatible – meaning the embryos don’t develop – it could not produce viable offspring. Our challenge was to make mating ineffective.
The approach we ultimately tested relied on Wolbachia, a naturally occurring bacterium found in many insects. Some Wolbachia strains create a form of reproductive incompatibility, as described above.
The theory is simple: release enough Wolbachia-carrying males into a population and, over time, the population declines. The released males are also beautifully evolved to search and find the last females – their large bushy antennae are super-radars for this job.
North Queensland the perfect laboratory
The Cassowary Coast in north Queensland provided ideal conditions for a large-scale trial of this approach. The region contained towns with abundant Aedes aegypti populations, while surrounding agricultural areas limited movement between communities. Equally important was the support of residents, local government and First Nations leaders.
Aedes aegypti likely arrived in Queensland in the late 1800s. It is distinct from our native mosquitoes because it is highly domesticated and feeds mainly on humans.
Before a single mosquito was released, the project team spent two years conducting field surveys and engaging with communities. We met with households, community organisations, First Nations leaders and local councils to discuss the technology and answer questions. The project, known as “Debug Innisfail”, ultimately received regulatory approval from multiple authorities.
Releasing three million male mosquitoes
Field surveys began in 2015, involving a collaborative team spanning Australian and US institutions. During a 20-week release period in 2018, around three million Wolbachia-carrying male mosquitoes were released into three treatment towns. Meanwhile, control towns where no mosquitoes were released were monitored.
The release system itself reflected Verily’s engineering strengths. The company developed bespoke technologies, including machine-learning-based systems capable of separating male and female mosquitoes, crucial to ensuring only males were released.
The results were striking: when compared with control towns, mosquito populations in towns where mosquitoes were released began declining within four weeks. The findings, published in 2021, demonstrated incompatible male mosquito releases could achieve strong suppression.
In two treatment towns, suppression effects persisted into the following year. In one town, monitoring detected only a handful of Aedes aegypti 12 months later, corresponding to roughly 95% suppression.
What this means for the US
The Australian trials provide evidence-based answers to many of the concerns now being raised in the US.
First, ecological impacts are likely to be very small. Aedes aegypti is an invasive species in Australia and many other countries. Because it exclusively lives around humans and bites them, removing it from urban environments has minimal ecological consequences.
Second, the approach can work at scale. Although adult mosquitoes survive for only a few days, continuous releases of highly competitive males can substantially reduce populations across entire towns.
Third, benefits may persist after releases finish. This is because the suppression outcome does not necessarily disappear straight away, and can carry over into subsequent seasons. But that doesn’t mean mosquito biology can be ignored – success depends on factors such as local ecology, mosquito movement patterns, and community participation. The technology alone is not enough.
A model for future mosquito control
Perhaps the most important lesson from the trials is the value of collaboration. This project brought together researchers from six universities and Verily. Combining scientific expertise with industrial-scale engineering accelerated the journey from laboratory concept to real-world field trial in an incredibly short time.
We are still working towards biological and mechanical approaches to efficiently separating male mosquitoes, which would have better utility in developing countries.
As Aedes aegypti expands its range and insecticides fail to suppress it, using the mosquito against itself as the biological control tool will become increasingly important.
The Queensland trials helped lay the groundwork for programs now underway in the US. And they are a reminder that when science, technology and communities work together, it is possible to solve problems that matter.
Nigel Beebe is a professor at The University of Queensland
This article was republished from The Conversation under a Creative Commons licence.
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