Radiation dose-rate is a neglected critical parameter in dose–response of insects

Abstract

Reproductive sterility is the basis of the sterile insect technique (SIT) and essential for its success in the field. Numerous factors that influence dose–response in insects have been identified. However, historically the radiation dose administered has been considered a constant. Efforts aiming to standardize protocols for mosquito irradiation found that, despite carefully controlling many variable factors, there was still an unknown element responsible for differences in expected sterility levels of insects irradiated with the same dose and handling protocols. Thus, together with previous inconclusive investigations, the question arose whether dose really equals dose in terms of biological response, no matter the rate at which the dose is administered. Interestingly, the dose rate effects studied in human nuclear medicine indicated that dose rate could alter dose–response in mammalian cells. Here, we conducted experiments to better understand the interaction of dose and dose rate to assess the effects in irradiated mosquitoes. Our findings suggest that not only does dose rate alter irradiation-induced effects, but that the interaction is not linear and may change with dose. We speculate that the recombination of reactive oxygen species (ROS) in treatments with moderate to high dose rates might minimize indirect radiation-induced effects in mosquitoes and decrease sterility levels, unless dose along with its direct effects is increased. Together with further studies to identify an optimum match of dose and dose rate, these results could assist in the development of improved methods for the production of high-quality sterile mosquitoes to enhance the efficiency of SIT programs.

Quality Control and Mating Performance of Irradiated Glossina palpalis gambiensis Males

“…This result stressed the importance of regularly controlling the dosimetry parameters of radioactive sources in order to reach the targeted total dose and ensure adequate sterility and insect competitiveness [ 9 ]. In this line, a recent work of Yamada et al [ 40 ] showed that the total dose should not be considered as the main parameter in sterilizing insects. The authors highlighted in irradiated mosquitoes a nonlinear interaction between the dose and dose rate that may change with the dose.…”

Gamma-radiation of Glossina palpalis gambiensis revisited: effect on fertility and mating competitiveness

“…This is important given that tsetse pupae are more radiosensitive than adults [ 13 , 56 ]. It was therefore deemed necessary to re-assess the validity of the 110 Gy dose, especially as local conditions can impact the efficiency of irradiation, including dose [ 65 ].…”

“…A recent, more detailed study with Ae. aegypti pupae showed that at high doses, lower dose rates achieved greater sterility than higher dose rates [ 65 ]. The difference might also be related to a different radiation protocol used.…”

“…It was deemed necessary to investigate the optimal irradiation dose for G . palpalis gambiensis , particularly as local conditions can impact the efficiency of irradiation, including dose-rate [ 65 ]. This study was therefore initiated to assess the effect of gamma-radiation on G. palpalis gambiensis male pupae, as well as their mating performance in walk-in field cages.…”

Effects of radiation on the fitness, sterility and arbovirus susceptibility of a Wolbachia‐free Aedes albopictus strain for use in the sterile insect technique

“…Thus a Wolbachia ‐free GT strain has been established that exhibited similar fitness as the GUA strain. The adult stage was selected for irradiation as numerous factors that affect the dose response in pupae can result in variable and heterogeneous sterility levels 37–39 . Doses of 20 and 30 Gy were sufficient to sterilize males and females, respectively, without affecting male mating competitiveness or female flavivirus susceptibility.…”