Optimization of the irradiation dose for Anopheles coluzzii for implementation of the sterile insect technique

The sterile insect technique (SIT) is a population suppression strategy that involves releasing sterile male insects, which mate with wild females, thereby inducing sterility in the target population. Although SIT represents a promising complementary approach for malaria vector control, its success depends on identifying an irradiation dose that ensures high sterility while preserving the biological performance of males. This study aimed to determine the optimal irradiation dose for sterilizing Anopheles coluzzii, a major malaria vector in West Africa, under laboratory conditions in Burkina Faso.

Experiments were conducted using the 13th generation (G13) of a laboratory strain of Anopheles coluzzii. Pupae were irradiated with doses ranging from 40 to 120 Gy. Key biological parameters, including adult emergence rate, insemination rate, fertility (egg hatching rate), and survival, were evaluated under controlled laboratory conditions.

Irradiation did not affect adult emergence at any of the tested doses. Though insemination rates declined at higher doses, they were not significantly impacted by doses between 40 and 70 Gy. All irradiation doses negatively affected mosquito survival, with more pronounced effects observed at higher doses. Egg hatching rates remained unaffected at 40 and 50 Gy, were significantly reduced at 60 Gy, and were completely suppressed at 70 Gy.

An irradiation dose of 70 Gy appears optimal for Anopheles coluzzii, because it induces complete sterility (0% hatching) while maintaining insemination and emergence rates similar to those of the control group, despite a dose-dependent reduction in survival. Further studies are needed to evaluate the mating competitiveness of males irradiated at this dose under semi-field and field conditions to support the implementation of the sterile insect technique (SIT) in Burkina Faso.