A rapid quality control test to foster the development of the sterile insect technique against Anopheles arabiensis

Abstract

Background: With the fight against malaria reportedly stalling there is an urgent demand for alternative and sustainable control measures. As the sterile insect technique (SIT) edges closer to becoming a viable complementary tool in mosquito control, it will be necessary to find standardized techniques of assessing male quality throughout the production system and post-irradiation handling. Flight ability is known to be a direct marker of insect quality. A new version of the reference International Atomic Energy Agency/Food and Agricultural Organization (IAEA/FAO) flight test device (FTD), modified to measure the flight ability and in turn quality of male Anopheles arabiensis within a 2-h period via a series of verification experiments is presented. Methods: Anopheles arabiensis juveniles were mass reared in a rack and tray system. 7500 male pupae were sexed under a stereomicroscope (2500 per treatment). Stress treatments included irradiation (with 50, 90, 120 or 160 Gy, using a Gammacell 220), chilling (at 0, 4, 8 and 10 °C) and compaction weight (5, 15, 25, and 50 g). Controls did not undergo any stress treatment. Three days post-emergence, adult males were subjected to either chilling or compaction (or were previously irradiated at pupal stage), after which two repeats (100 males) from each treatment and control group were placed in a FTD to measure flight ability. Additionally, one male was caged with 10 virgin females for 4 days to assess mating capacity (five repeats). Survival was monitored daily for a period of 15 days on remaining adults (two repeats). Results: Flight ability results accurately predicted male quality following irradiation, with the first significant difference occurring at an irradiation dose of 90 Gy, a result which was reflected in both survival and insemination rates. A weight of 5 g or more significantly reduced flight ability and insemination rate, with survival appearing less sensitive and not significantly impacted until a weight of 15 g was imposed. Flight ability was significantly reduced after treatments at 4 °C with the insemination rate more sensitive to chilling with survival again less sensitive (8 and 0 °C, respectively). Conclusions: The reported results conclude that the output of a short flight ability test, adapted from the previously tested Aedes FTD, is an accurate indicator of male mosquito quality and could be a useful tool for the development of the SIT against An. arabiensis.

Field performance of sterile male mosquitoes released from an uncrewed aerial vehicle

“…For example, a competitiveness of 0.7 to 1.0 was observed for irradiated male A. albopictus under semi-field conditions in Italy ( 31) and of 0.4 to 0.8 in Reunion island (32). Moreover, flight ability of A. albopictus, A. Aegypti, and Anopheles arabiensis was not impaired with radiation doses of up to 40, 90, and 50 Gy, respectively (25,33). Last, triple Wolbachia-infected male A. albopictus irradiated with 40 Gy showed a competitiveness close to 1 in walk-in field cage studies and of 0.5 to 0.7 in the field.…”

Adult mosquito predation and potential impact on the sterile insect technique

“…Since mantises are mainly sit-and-wait predators 53 , chances for a mosquito to escape from predation may rely on its flight speed. Adverse effects of high irradiation doses on male mosquito quality including competitiveness and flight ability have previously been reported 44 , 45 , 54 , 55 . The vulnerability of males irradiated with 100 Gy could therefore be related to reducing of their flight ability.…”

“…albopictus and Anopheles arabiensis are among the species currently targeted by SIT programmes 30 . Significant advances have been made (and are being optimised) in developing SIT package against these mosquitoes, including colonisation, mosquito mass-rearing 31 – 36 , sex-separation 37 – 40 , handling 41 , radiation 42 , 43 , quality control 44 , 45 , and release 46 . In addition, field investigations such as the ecology of reproduction of mosquitoes 47 and the sterile male behaviour 48 , 49 have been carried out to determine the technique’s feasibility.…”

Medium‐term feasibility of the management of the invasive crayfish Procambarus clarkii with the sterile males release technique

“…). A very different point of view evaluates the effects of radiation on the sterility of animals without compromising their viability, either for commercial purposes 12 or for the control of populations of harmful arthropods as, for example, against the vector of malaria Anopheles arabiensis 31 …”