Investigation of Developmental Stage/Age, Gamma Irradiation Dose, and Temperature in Sterilization of MaleAedes aegypti(Diptera: Culicidae) in a Sterile Insect Technique Program

Abstract

The sterilization process using gamma irradiation is a crucial component in a program using sterile insect technique (SIT) to control Aedes aegypti. Unfortunately, there is no efficient standard protocol for sterilizing mosquitoes that can produce a high level of sterility while maintaining mating ability and longevity. Therefore, we conducted a study of the critical factors necessary to develop such a standard protocol. In this study, male Ae. aegypti pupae, as well as adults aged 1 d and 3 d, were irradiated using a Gamma-cell 220 irradiator doses of 0, 20, 40, 60, 70, 80, and 100 Gray (Gy). In addition, male Ae. aegypti in the pupal and adult stage aged 1 d were irradiated at a dose of 70 Gy at various temperatures. Changes in emergence rates, longevity, sterility, and mating competitiveness were recorded for each combination of parameters. Results showed that an increase of irradiation dose leads to a rise of induced sterility at all developmental stages, while simultaneously reducing emergence rate, survival, and mating competitiveness. Higher temperatures resulted in increased levels of sterility, reduced longevity, and did not affect the ability to mate. This study found that an irradiation dose of 70 Gy at a temperature between 20.00 and 22.30°C administered in the pupal stage induced a high level of sterility (around 98%), while maintaining mating competitiveness and longevity.

Characterization of luminescent dosimeters for sterile insect technique

“…The data presented in Table 2 show that the mean doses measured on 23/11/2021 by the MTS-N and Li2B4O7:Cu,Ag dosimeters showed percentage differences of 5.4% and 5.5%, respectively, in relation to the nominal dose. Similar results were reported by Ernawan and colleagues [10] who is a study to devise a standard protocol for sterilizing Aedes aegypti mosquitoes using a dosimetry system based on Gafchromic HD-V2 films (Ashland, Bridgewater, NJ) to confirm and verify the dose absorbed by the insects. The authors reported that the measured doses were within 5% of the dose specified by the respective irradiator setting.…”

“…But to read alanine dosimeters, Electron Paramagnetic Resonance (EPR) equipment is needed, which is expensive and rarely available in facilities that perform the SIT technique. For this reason, routinely Gafchromic® film systems [8] are used, due to their low-cost and simple measurement technique [2,9,10,11]. However, the performance of this dosimetric system is affected by environmental factors, such as temperature and analysis time [8].…”

Response of male adult Aedes mosquitoes to gamma radiation in different nitrogen environments

“…Indeed, it has been reported that lower temperatures decreased the induced sterility of Ae. aegypti irradiated at the pupal or adult stages ( Ernawan et al, 2022 ).…”

“…While efforts are still being devoted to overcome these difficulties, the focus is now shifting to irradiation during the adult stage. It has been reported that adult Aedes mosquitoes are similarly or slightly more radiosensitive than old pupae with a better quality after irradiation in some cases ( Du et al, 2019 ; Ernawan et al, 2022 ). However, the main challenge is the immobilization and compaction of a large number of adult males for homogenous irradiation with minimal deleterious effects on their downstream quality.…”

“…However, the main challenge is the immobilization and compaction of a large number of adult males for homogenous irradiation with minimal deleterious effects on their downstream quality. In general, cold temperatures are used to knock down the mosquitoes ( Zhang et al, 2020 ; Ernawan et al, 2022 ). However, the quality of the sterile males can be compromised if the chilling temperatures and duration are not carefully controlled.…”