Current and proposed insect targets for gene drive development

Introduction
The emergence of gene drive technology opens-up unprecedented prospects of modifying, suppressing, or even eliminating wild species to serve human purposes. The consequences of choosing to go down this path are very difficult to foresee, especially in the longer term. To help frame further discussion on this topic, we have conducted a survey of gene drive development in insects, screening the the scientific literature up until April 2022. The survey also includes development of so-called ‘x-shredders’, a sex ratio distortion system with close similarities to gene drive technology.
We do not cover issues regarding risks, difficulties in performing robust risk assessments, or the lack of proven methods to confine, halt or reverse engineered gene drives.

Our survey gives an overview of:

• What research has taken place or is ongoing.
• Which species and taxa are current or proposed targets for gene drive development, and which types of gene drives are being put forward. 1
• How far along developments have progressed and what the next stages of experimentation might be.

Key findings:

• There are currently 32 insect targets from six different orders proposed or under development. 2
• While nine of the proposed targets are vectors of human disease, in particular malaria, the majority (21) are agricultural pests, including four livestock pests or livestock disease vectors, which partially overlap with human disease vectors.
• Only three species are proposed as targets because of wider biodiversity impacts or combined economic loss and biodiversity impacts, as well as one for forest management purposes and one for conservation, the latter again overlapping with human disease vectors.
• The majority of gene drive proposals are based on eradication/suppression approaches. Only a very few are projects that are actually aiming to modify characteristics of insects in the wild.
• At the present time no projects are close to producing a usable and proven ‘product’. But some are closer to potential field trials, pending on regulation, risk assessment and further (technical) developments.

Footnotes:

1  Many experimental gene drive systems are being developed and tested in the model organism Drosophila melanogaster. Because we are not aware of any plans to target this organism in the wild, a survey of work in this species is not included here but rather will be presented in a separate table.
2  The vast majority of the targets identified in the literature are single species or species complexes, however some early stage proposals relate to broader taxonomic groups, namely the Glossina genus (Testse flies - row 31), the Scolytinae subfamily (Bark beetles - row 44) and the Thysanoptera order (Thrips - row 51).