Effect of Egg Irradiation on Development and Sterility of Wild-Type andWolbachiaTrans-InfectedAedes aegyptiMosquito Vectors

Abstract

Background Sterile Insect Technique (SIT), Incompatible Insect Technique (IIT) and a combination become the alternative promising vector control approaches. In these approaches, the targeted mosquitoes need to be sterilized and released. So far, the irradiation of mosquitoes has been conducted at the pupae or adult stages. In this study, we investigated the possibility of the X-ray irradiation at the egg stage and also assessed the effect on the development and sterility of both wild-type and Wolbachia trans-infected Aedes aegypti mosquito vectors. Methodology/Principal Findings The eggs of Aedes aegypti, both wild-type and Wolbachia trans-infected lines, were irradiated using X-ray at the doses of 1, 3, 5 and 7 Gy. Development of immature stages was observed. For wild-type Aedes aegypti, X-ray irradiation at the doses from 3 Gy decreased the development of the first instar larvae and increased the development of the third instar larvae but there was no effect on pupae when compared to those of the controls (p < 0.05). For Wolbachia trans-infected ones, the irradiation dose as low as 1 Gy could increase the development of the forth-instar larvae while the irradiation dose of 7 Gy induced significantly high mortality in pupae. To assess sterility, males and females emerged from irradiated eggs were mated with the normal ones. Results showed that the irradiation doses for sterilization of Wolbachia trans-infected Ae. aegypti was lower than those of the wild-type ones. The egg hatch rate of both males and females could significantly be reduced from the irradiation dose of 5 Gy in Wolbachia trans-infected Ae. aegypti and 7 Gy in the wild-type ones. Conclusions/Significance Our findings revealed the possibility to sterilize both wild-type and Wolbachia trans-infected Ae. aegypti by applying a low-dose X-ray irradiation at the egg stage. Egg irradiation could make an implementation of SIT, IIT or combined IIT/SIT for vector control much more feasible as the sterile dry eggs are easier to distribute and operate when compared to other developmental stages of mosquitoes.