Longevity of mass-reared, irradiated and packed male Anopheles arabiensis and Aedes aegypti under simulated environmental field conditions

Abstract

BackgroundTo ensure the success of a mosquito control programme that integrates the sterile insect technique (SIT), it is highly desirable to release sterile males with a maximal lifespan to increase release effectiveness. Understanding sterile male survival under field conditions is thus critical for determining the number of males to be released. Our study aimed to investigate the effect of mass rearing, irradiation, chilling, packing and release time on irradiated male mosquito longevity.MethodsAnopheles arabiensis and Aedes aegypti immature stages were mass-reared using a rack and tray system. Batches of 50 males irradiated at the pupal stage were immobilised, packed into canisters and chilled for 6 hours at 6 °C. Mosquitoes were then transferred either in the early morning or early evening into climate chambers set to simulate the weather conditions, typical of the beginning of the rainy season in Khartoum, Sudan and Juazeiro, Brazil for An. arabiensis and Ae. aegypti, respectively. The longevity of experimental males was assessed and compared to mass-reared control males subjected either to simulated field or laboratory conditions.ResultsThe combined irradiation, chilling and packing treatments significantly reduced the longevity of both An. arabiensis and Ae. aegypti under simulated field conditions (P < 0.001). However, packing alone did not significantly reduce longevity of Ae. aegypti (P = 0.38) but did in An. arabiensis (P < 0.001). Overall, the longevity of mass reared, irradiated and packed males was significantly reduced, with the median survival time (days) lower following an early morning introduction (4.62 ± 0.20) compared to an evening (7.34 ± 0.35) in An. arabiensis (P < 0.001). However, there was no significant difference in longevity between morning (9.07 ± 0.54) and evening (7.76 ± 0.50) in Ae. aegypti (P = 0.14).ConclusionsOur study showed that sterile mass-reared males have a reduced lifespan in comparison to laboratory-maintained controls under simulated field conditions, and that An. arabiensis appeared to be more sensitive to the handling process and release time than Ae. aegypti. Longevity and release time are important parameters to be considered for a successful area-wide integrated vector control programme with a SIT component.

Comparative response to post‐production process of two Anastrepha ludens strains: Application in the sterile insect technique

“…Our study adds to evidence that the packing process reduces sterile male performance irrespective of fly strain. For example, chilling and crowded conditions reduce flight ability and mating competitiveness in sterile males of C. capitata, A. ludens and Anopheles arabiensis (Patton) (Andress et al, 2013;Culbert et al, 2017Culbert et al, , 2018Díaz-Fleischer et al, 2009). Many parts of the packing and transportation process may result in a negative synergism that affects fly quality.…”

Potential Impact of Integrating the Sterile Insect Technique into the Fight against Disease-Transmitting Mosquitoes

“…To quantify and help minimize the impact of mass-rearing, irradiation, and handling on sterile male mosquitoes, several methods to judge the consistency, quality, and predicted performance following release have been suggested. The relative impact of different handling treatments, and combinations of different parameters, could be estimated by comparing the longevity of exposed males (Chung et al 2018;Culbert et al 2018b). Longevity is an important parameter of released males, also sometimes used as a proxy measure of quality.…”

Designing Effective <em>Wolbachia</em> Release Programs for Mosquito and Arbovirus Control

“…Mosquito genetic background can influence pathogen blocking by Wolbachia , Ford et al, 2019 as well as host fitness costs (Ritchie et al, 2015, Carvalho et al, 2020, making it important to evaluate strains in local mosquitoes before releases take place. Handling conditions are also crucial, since rearing, storage, transport and release procedures can affect mosquito quality (Chung et al, 2018, Culbert et al, 2018.…”