Successful introgression of wMel Wolbachia into Aedes aegypti populations in Fiji, Vanuatu and Kiribati

Abstract

Pacific Island countries have experienced periodic dengue, chikungunya and Zika outbreaks for decades. The prevention and control of these mosquito-borne diseases rely heavily on control of Aedes aegypti mosquitoes, which in most settings are the primary vector. Introgression of the intracellular bacterium Wolbachia pipientis ( wMel strain) into Ae. aegypti populations reduces their vector competence and consequently lowers dengue incidence in the human population. Here we describe successful area-wide deployments of wMel-infected Ae. aegypti in Suva, Lautoka, Nadi (Fiji), Port Vila (Vanuatu) and South Tarawa (Kiribati). With community support, weekly releases of wMel-infected Ae. aegypti mosquitoes for between 2 to 5 months resulted in wMel introgression in nearly all locations. Long term monitoring confirmed a high, self-sustaining prevalence of wMel infecting mosquitoes in almost all deployment areas. Measurement of public health outcomes were disrupted by the Covid19 pandemic but are expected to emerge in the coming years.

Author summary

For decades, dengue, Zika and chikungunya have been public health issues across the Pacific Island region. Aedes aegypti mosquitoes are considered most responsible for the transmission of dengue between people. The introduction of a bacteria called Wolbachia pipientis ( wMel strain) to these mosquitoes is known to reduce the transmission of these diseases. Herein, we describe the production and release of wMel-carrying Ae. aegypti mosquitoes into several Pacific Island cities, including Suva, Lautoka, and Nadi in Fiji, Port Vila in Vanuatu, and South Tarawa in Kiribati. With community support, these mosquitoes were released on a weekly basis for periods ranging from 2 to 5 months. The result was a widespread integration of the wMel bacteria into local mosquito populations. Long-term monitoring has shown that the wMel bacteria has been sustained at high levels in mosquitoes in nearly all of the areas where it was introduced. This innovative approach could potentially improve the way we combat mosquito-borne diseases, protecting communities in the Pacific Islands and beyond from the devastating effects of dengue, chikungunya, and Zika.