The invention concerns a genetically transformed or transfected bacterial cell wherein said bacteria is a gut symbiont of an insect vector or insect pest； characterised in that said bacterial cell is transformed to express dsRNA against at least one selected target gene of the insect vector, whereby the effect or viability of said insect is deleteriously compromised； also an insect including said bacterial cell and a method of modulating a target insect gene using said bacterial cell.
