Characterization of a yeast interfering RNA larvicide with a target site conserved in the synaptotagmin gene of multiple disease vector mosquitoes.

New mosquito control strategies are vitally needed to address established and emerging arthropod-borne infectious diseases. Here we describe the characterization of a yeast interfering RNA larvicide that was developed through the genetic engineering of Saccharomyces cerevisiae (baker's yeast) to express a short hairpin RNA targeting the Aedes aegypti synaptotagmin (Aae syt) gene. The larvicide effectively silences the Aae syt gene, causes defects at the larval neural synapse, and induces high rates of A. aegypti larval mortality in laboratory, simulated-field, and semi-field trials. Conservation of the interfering RNA target site in multiple mosquito species, but not in humans or other non-target species, suggested that it may function as a broad-range mosquito larvicide. In support of this, consumption of the yeast interfering RNA larvicide was also found to induce high rates of larval mortality in Aedes albopictus, Anopheles gambiae, and Culex quinquefasciatus mosquito larvae. The results of these studies suggest that this biorational yeast interfering RNA larvicide may represent a new intervention that can be used to combat multiple mosquito vectors of human diseases. Author summary It is critical that we develop new strategies for the environmentally safe control of disease vector mosquitoes. In this study, baker's yeast was genetically engineered to produce interfering RNA molecules corresponding to the mosquito synaptotagmin (syt) gene, but which do not match any genes in humans or other non-target organisms. Larval consumption of the yeast, which was prepared in a ready-to-use dried inactivated tablet formulation, turned off the syt gene and disrupted function of the mosquito nervous system. The yeast larvicide induced high levels of larval mortality in a variety of different human disease vector mosquito species. Inactivated yeast interfering RNA tablets performed well in contained semi-field experiments, suggesting that this technology, if further developed and optimized in the field, could one day be used for the biorational control of mosquitoes and the prevention of multiple mosquito-borne illnesses.