Participation of irradiated Anopheles arabiensis males in swarms following field release in Sudan.

Tellal B Ageep,Elwaleed Ho Salih,Bashir Alsharif,David Damiens,Abdoulaye Diabaté,Fayez Ta Ahmed,Rosemary S Lees,Ayman Ahmed,Jeremie Rl Gilles,Badria B El Sayed

doi:10.1186/1475-2875-13-484

Abstract

BackgroundThe success of the sterile insect technique (SIT) depends the release of large numbers of sterile males, which are able to compete for mates with the wild male population within the target area. Unfortunately, the processes of colonisation, mass production and irradiation may reduce the competitiveness of sterile males through genetic selection, loss of natural traits and somatic damage. In this context, the capacity of released sterile Anopheles arabiensis males to survive, disperse and participate in swarms at occurring at varying distances from the release site was studied using mark-release-recapture (MRR) techniques.MethodsIn order to assess their participation in swarms, irradiated and marked laboratory-reared male mosquitoes were released 50, 100 or 200 m from the known site of a large swarm on three consecutive nights. Males were collected from this large swarm on subsequent nights. Over the three days a total of 8,100 males were released. Mean distance travelled (MDT), daily probability of survival and estimated population size were calculated from the recapture data. An effect of male age at the time of release on these parameters was observed.ResultsFive per cent of the males released over three days were recaptured. In two-, three- and four-day-old males, MDT was 118, 178 and 170 m, and the daily survival probability 0.95, 0.90 and 0.75, respectively. From the recapture data on the first day following each release, the Lincoln index gives an estimation of 32,546 males in the natural population.DiscussionSterile An. arabiensis males released into the field were able to find and participate in existing swarms, and possibly even initiate swarms. The survival probability decreased with the age of male on release but the swarm participation and the distance travelled by older males seemed higher than for younger males. The inclusion of a pre-release period may thus be beneficial to male competitiveness and increase the attractiveness of adult sexing techniques, such as blood spiking.

Highlights

The success of the sterile insect technique (SIT) depends the release of large numbers of sterile males, which are able to compete for mates with the wild male population within the target area
Observations of Helinski et al [50], who demonstrated the ability of irradiated laboratory-reared males to participate effectively in swarms in a contained semi-field system, are confirmed in the field as observed by Hassan et al [33]
The probability of daily survival was similar to the survival previously reported in wild Anopheles species, usually between 0.8 and 0.9 in the field [44,59,60,61,62]

Summary

Introduction

The success of the sterile insect technique (SIT) depends the release of large numbers of sterile males, which are able to compete for mates with the wild male population within the target area. The processes of colonisation, mass production and irradiation may reduce the competitiveness of sterile males through genetic selection, loss of natural traits and somatic damage In this context, the capacity of released sterile Anopheles arabiensis males to survive, disperse and participate in swarms at occurring at varying distances from the release site was studied using mark-release-recapture (MRR) techniques. Despite a reduction in incidence since the late 1990s, malaria remains a major public health challenge to Sudan, causing between one and two million cases annually between 2010 and 2012 [1] In view of this high burden of disease, the Tropical Medicine Research Institute in Sudan, with the support of the Food and Agriculture Organization of the United Nations (FAO) and the International Atomic Energy Agency (IAEA), initiated a Competitiveness in the field is determined by the ability to survive, disperse and participate efficiently in natural mating behaviour. In addition to the rearing itself, the sterilizing radiation (even when optimized to balance the level of sterility induced and the competitiveness of the irradiated males) could affect male quality: reduced emergence [19,20], reduced longevity [19,21,22], and diminished sperm production [23] have all been observed in irradiated male anopheline mosquitoes

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Conclusion