Scientists Edit the Genome of Culicoides Biting Midges for the First Time

Scientists have successfully edited the genome of biting midges, opening the door to new research on how these insects transmit disease.

Culicoides biting midges are small blood‑feeding insects responsible for spreading important vector‑borne viruses such as bluetongue virus (BTV), Schmallenberg virus (SBV), and epizootic hemorrhagic disease virus (EHDV), which cause major losses to livestock production worldwide. Despite their importance as disease vectors, Culicoides are amongst the smallest blood‑feeding insects, just 1-4 mm in length, making them difficult to study in the laboratory.

Writing in Scientific Reports, researchers from The Pirbright Institute explain how they used a CRISPR‑based technique to modify the genome of Culicoides midges. The method involves injecting a mix of Cas9 enzyme and guide RNA (gRNA) molecules into female insects. These components are taken up by their oocytes (eggs), where they act like molecular scissors, cutting DNA at specific target locations and inducing mutations.

Lead author Katherine Nevard (Insect Transgenesis Science Technology Platform scientist at The Pirbright Institute) explained that, “due to the size and delicacy of Culicoides, initial attempts to perform gene editing in this species using traditional embryo microinjection methods were unsuccessful”.

In early 2024, Katherine spent two months in the laboratory of Professor Jason Rasgon (Penn State University, USA), an expert in vector genetics and a pioneer of the technologies the team aimed to apply to Culicoides biting midges. During this time, she received training in intrathoracic injection techniques using the ReMOT Control method.

Upon Katherine’s return, the team used intrathoracic injection to apply the recently developed DIPA‑CRISPR method and successfully mutated a gene that controls eye colour in midges, demonstrating that it works in a Culicoides species.

Dr Rafael Homem, who leads the Insect Transgenesis Science Technology Platform at The Pirbright Institute, highlighted that “this is the first demonstration of CRISPR‑based gene editing in any Culicoides species and that it provides a practical approach for genetic manipulation in these insects”.

Dr Christopher Sanders, Head of Entomology at Pirbright, added that “these tools will enable new research and support efforts to better understand Culicoides-borne diseases. Culicoides midges transmit diseases affecting livestock and, in some cases, humans. Improving our understanding of their biology could help reduce disease transmission and improve both animal and human health”.