X-ray sterilization of the An. arabiensis genetic sexing strain 'ANO IPCL1' at pupal and adult stages.

With a view to area wide integrated pest management programs with a sterile insect technique (SIT) component against the malaria vector Anopheles arabiensis, the effects of X-ray exposure of males of the genetic sexing strain (GSS) of An. arabiensis, "ANO IPCL1" have been tested. The suitability of X-ray was assessed in comparison to gamma-ray for mosquito sterilization in operational settings where the acquisition of gamma ray irradiators may be problematic. Pupae and adult males were sterilized using X-ray irradiation at 5 increasing doses and effects were observed in terms of fecundity and fertility. Irradiated pupae and adults were further observed for effects on longevity. The adult stage appeared to be more sensitive to radiation exposure than the pupal stage, with a residual fertility of 1% in adults irradiated at 75Gy and 0% at 105Gy, compared to 8%at 75Gy and 4% at 105Gy in adults irradiated at the pupal stage. All treatment groups except those irradiated at 60Gy were statistically different from the control groups in terms of adult longevity post treatment, however overall survival was not highly compromised in the 75Gy treatment group which showed 96% of induced sterility. To ensure the fine balance between the induced sterility and the fitness of the insect produced is achieved, irradiation of adults at this dose may be a good compromise for the SIT as applied for this species, especially in specific cases such as sterilization after female elimination by spiking blood meals. Investigation into the combined effects of blood spiking and irradiation at the adult stage and additional competitiveness studies both in laboratory and field cages will provide more insight into the radiation dose and mosquito stage to be used in the frame of future SIT programs targeting this important malaria vector.