Development of a novel biorational strategy for effective and targeted delivery of Bacillus thuringiensis-based insecticides in Aedes mosquito larvae

Mosquito control is a hot topic as females vector several animal and human pathogens that cause diseases through their bites. In addition, by reason of globalization and climate change, areal expansion of mosquitoes is causing an increase in neglected tropical disease outbreaks in non-endemic regions. The Asian tiger mosquito (Aedes albopictus) is major concern due to the exponential spread of this species worldwide and its ability to vector arboviruses as Zika and Dengue.

We aim at contributing to this issue by developing innovative and biorational solutions for mosquito larvae control based on microbial entomopathogens as Bacillus thuringiensis var. israelensis (Bti) and Lysinibacillus sphaericus. In particular, we have designed and tested hydrogel-based insecticidal tools for effective and targeted delivery of entomopathogens in Ae. albopictus breeding sites, which are ubiquitous within domestic and peridomestic environments.

In addition, since we have recently demonstrated that RNAi-mediated immune suppression in lepidopteran pests enhance susceptibility to B. thuringiensis formulates, we challenged the same approach for Ae. albopictus. To identify potential RNAi targets, from the conserved amino acid sequences of genes involved in immune responses in adult mosquitoes of different species, we have identified the full-length mRNA of different putative immune genes in Ae. albopictus larvae and analysed their expression in larvae exposed to entomopathogens. The results obtained pave the way for the development of novel delivery tools for mosquito larvae control containing both Bti and immune silencing dsRNAs to enhance Bti efficacy and counteract selective pressure for resistance development.