Towards a sterile insect technique field release of Anopheles arabiensis mosquitoes in Sudan: Irradiation, transportation, and field cage experimentation

Abstract

BackgroundThe work described in this article forms part of a study to suppress a population of the malaria vector Anopheles arabiensis in Northern State, Sudan, with the Sterile Insect Technique. No data have previously been collected on the irradiation and transportation of anopheline mosquitoes in Africa, and the first series of attempts to do this in Sudan are reported here. In addition, experiments in a large field cage under near-natural conditions are described.MethodsMosquitoes were irradiated in Khartoum and transported as adults by air to the field site earmarked for future releases (400 km from the laboratory). The field cage was prepared for experiments by creating resting sites with favourable conditions. The mating and survival of (irradiated) laboratory males and field-collected males was studied in the field cage, and two small-scale competition experiments were performed.ResultsMinor problems were experienced with the irradiation of insects, mostly associated with the absence of a rearing facility in close proximity to the irradiation source. The small-scale transportation of adult mosquitoes to the release site resulted in minimal mortality (< 6%). Experiments in the field cage showed that mating occurred in high frequencies (i.e. an average of 60% insemination of females after one or two nights of mating), and laboratory reared males (i.e. sixty generations) were able to inseminate wild females at rates comparable to wild males. Based on wing length data, there was no size preference of males for mates. Survival of mosquitoes from the cage, based on recapture after mating, was satisfactory and approximately 60% of the insects were recaptured after one night. Only limited information on male competitiveness was obtained due to problems associated with individual egg laying of small numbers of wild females.ConclusionIt is concluded that although conditions are challenging, there are no major obstacles associated with the small-scale irradiation and transportation of insects in the current setting. The field cage is suitable for experiments and studies to test the competitiveness of irradiated males can be pursued. The scaling up of procedures to accommodate much larger numbers of insects needed for a release is the next challenge and recommendations to further implementation of this genetic control strategy are presented.

Genetic elimination of dengue vector mosquitoes

“…Large-scale SIT programs have suppressed or eliminated a number of major agricultural pests (15). SITapproaches for mosquito control have been tried (17)(18)(19) and continue to be proposed (20,21). Factors that may have limited the success of these initial mosquito SIT programs and that are of continued concern in proposed SIT applications include reduced mating competitiveness and residual fertility of irradiated males (22,23), the need to release exclusively males (male mosquitoes do not take blood meals) (20,24), and reduction of density-dependent larval mortality due to early acting lethality (22,25,26).…”

Effect of radiation and/or traditional processings on antinutrients and HCl extractability of calcium, phosphorus and iron of sorghum cultivars

“…The flour was exposed to gamma rays generated by a cobalt-60 source (Gammacell 220, MDS Nordion, Ottawa, Canada). The flour was irradiated at 0, 5, 10 and 15 kGy following the procedures described by Helinski et al (2008) with a dose rate of ca. 3.2 kGy/h at 24±1°C and normal relative humidity.…”

The development of new radiation protocols for insect sterilization using long wavelength x-rays

“…Males subjected to sterilization procedures using this high-energy radiation suffered from a reduced life span and other debilitating effects that made them uncompetitive with the wild population. [35] Sterilization is typically accomplished with gamma ray exposure employing 60 Co or 137 Cs as a source [8]. These radiation sources provide a combination of intense short wavelength gamma rays which do not readily interact with the biological tissue.…”

“…Over the years, SIT has proven to be an environmental friendly method of insect extermination without the use of pesticides, which can lead to unwanted collateral damage to insect species not being targeted for control. The International Atomic Energy Agency (IAEA) initiated a technologies development program to control malaria mosquitoes with the SIT technique in 2004 [8].…”