Releasing incompatible males drives strong suppression across populations of wild and <i>Wolbachia</i> -carrying <i>Aedes aegypti</i> in Australia

Abstract

Releasing sterile or incompatible male insects is a proven method of population management in agricultural systems with the potential to revolutionize mosquito control. Through a collaborative venture with the "Debug" Verily Life Sciences team, we assessed the incompatible insect technique (IIT) with the mosquito vector <i>Aedes aegypti</i> in northern Australia in a replicated treatment control field trial. Backcrossing a US strain of <i>Ae. aegypti</i> carrying <i>Wolbachia w</i>AlbB from <i>Aedes albopictus</i> with a local strain, we generated a <i>w</i>AlbB2-F4 strain incompatible with both the wild-type (no <i>Wolbachia</i>) and <i>w</i>Mel-<i>Wolbachia Ae. aegypti</i> now extant in North Queensland. The <i>w</i>AlbB2-F4 strain was manually mass reared with males separated from females using Verily sex-sorting technologies to obtain no detectable female contamination in the field. With community consent, we delivered a total of three million IIT males into three isolated landscapes of over 200 houses each, releasing ∼50 males per house three times a week over 20 wk. Detecting initial overflooding ratios of between 5:1 and 10:1, strong population declines well beyond 80% were detected across all treatment landscapes when compared to controls. Monitoring through the following season to observe the ongoing effect saw one treatment landscape devoid of adult <i>Ae. aegypti</i> early in the season. A second landscape showed reduced adults, and the third recovered fully. These encouraging results in suppressing both wild-type and <i>w</i>Mel-<i>Ae. aegypti</i> confirms the utility of bidirectional incompatibility in the field setting, show the IIT to be robust, and indicate that the removal of this arbovirus vector from human-occupied landscapes may be achievable.