Trial success as bacteria eradicates pest mosquito

The results of a landmark trial have shown how bacteria can successfully sterilise and eradicate the invasive, disease-carrying Aedes aegypti mosquito — responsible for spreading dengue, yellow fever and Zika — in a breakthrough that could support the suppression and potential eradication of Aedes aegypti worldwide.

A collaboration between CSIRO, The University of Queensland (UQ), Verily Life Sciences, QIMR Berghofer Medical Research Institute and James Cook University (JCU), the trial involved releasing three million male Aedes aegypti mosquitoes in Northern Queensland, sterilised with bacteria called Wolbachia, across three trial sites over a 20-week period during the summer of 2018. The sterile male insects searched out and mated with wild females, preventing the production of offspring.

“During the trial, we saw over 80% of the mosquito population suppressed across our three trial sites,” said CSIRO scientist and UQ Associate Professor Nigel Beebe.

“When we surveyed the sites the following year, we were very encouraged to see the suppression still in effect, with one of our most productive towns for Aedes aegypti almost devoid of this mosquito with a 97% reduction across the following season.”

Assoc Prof Beebe said the trial results, published in the journal PNAS, demonstrate that the technique is robust and capable of effectively suppressing mosquito populations. He did, however, note that while the mosquito population at the second trial site remained “substantially suppressed” one year on, the population at the third site had fully recovered.

“We are currently investigating the differences observed in the following mosquito season, as they are incredibly informative in further developing this technology and in modelling how we could remove this exotic virus-transmitting pest in other locations worldwide,” he said.

Verily Product Manager Nigel Snoad said it was “a huge achievement” by the joint team to set up and operate the mosquito rearing, sorting and release systems, and to develop strong community engagement and support. “The ongoing suppression after releases stopped is an important result,” he said, “indicating that sustained impact is feasible for this disease vector.”

The technique can also be used to remove the virus-transmitting Asian tiger mosquito, Aedes albopictus, which is now established at Australia’s doorstep in the Torres Strait Islands. Techniques from the trial are being used to support CSIRO-led mosquito suppression programs in French Polynesia and the Hunter region in NSW.

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