Radiation dose-fractionation in adult Aedes aegypti mosquitoes

Abstract

Balancing process efficiency and adult sterile male biological quality is one of the challenges in the success of the sterile insect technique (SIT) against insect pest populations. For the SIT against mosquitoes, many stress factors need to be taken into consideration when producing sterile males that require high biological quality to remain competitive once released in the field. Pressures of mass rearing, sex sorting, irradiation treatments, packing, transport and release including handling procedures for each step, add to the overall stress budget of the sterile male post-release. Optimizing the irradiation step to achieve maximum sterility while keeping off-target somatic damage to a minimum can significantly improve male mating competitiveness. It is therefore worth examining various protocols that have been found to be effective in other insect species, such as dose fractionation. A fully sterilizing dose of 70 Gy was administered to Aedes aegypti males as one acute dose or fractionated into either two equal doses of 35 Gy, or one low dose of 10 Gy followed by a second dose of 60 Gy. The two doses were separated by either 1- or 2-day intervals. Longevity, flight ability, and mating competitiveness tests were performed to identify beneficial effects of the various treatments. Positive effects of fractionating dose were seen in terms of male longevity and mating competitiveness. Although applying split doses generally improved male quality parameters, the benefits may not outweigh the added labor in SIT programmes for the management of mosquito vectors.

Different mechanisms of X-ray irradiation-induced male and female sterility in Aedes aegypti

“…These findings establish an optimal window for using irradiation to target the female germline for sterilization. In the SIT approach, higher irradiation doses, ranging from 35 to 70 Gy, are applied in order to achieve a 99% male sterility [37,[48][49][50]. It is worthwhile to note that most of these studies use a Gamma radiation source.…”

Radiation dose fractionation and its potential hormetic effects on male Glossina palpalis gambiensis (Diptera: Glossinidae): a comparative study of reproductive and flight quality parameters

“…Other studies based on dose fractionation showed the same trend with improved male performance, i.e., induced sterility, longevity, or mating competitiveness in insect pests of crops, livestock, and vectors of human diseases [52]. Fractionation of the radiation doses applied to the Indian meal moth, Plodia interpunctella showed a significant improvement of male longevity, mating competitiveness, and sterility [14], and similarly, a significant improvement was obtained in male Aedes aegypti's survival and mating competitiveness [67]. Dose fractionation applied to Glossina morsitans increased their residual fertility as compared with a similar but continuous single dose [21].…”

“…The SIT can only be successful when the colony-reared and released sterile males are as competitive as their wild counterparts to mate with wild females [61]. To produce high-quality sterile males for use in SIT programs, factors and processes such as the rearing, sterilization, transport, handling and release must be considered and properly managed as they are the critical factors that can affect the quality of the sterile males [67,69].…”

Upscaling irradiation protocols of Aedes albopictus pupae within an SIT program in Reunion Island

“…For example, in some facilities, the optimum dose for Aedes albopictus is reported to be between 35 and 40 Gy whereas it is 50 Gy for Aedes aegypti 20 , 24 , 29 , 30 . Other facilities require 55 Gy and 70 Gy for the two species respectively 21 , 31 , 32 . Dose–response is also affected significantly by atmospheric conditions during irradiation, and particularly oxygen levels have been shown to have significant impact on irradiation outcome 25 , 33 .…”