Reproductive biology and induced sterility as determinants for genetic control of mosquitoes with the Sterile Insect Technique

M. Helinski

Research output: Thesisinternal PhD, WU

Abstract

Malaria remains an important health issue in sub-Saharan Africa, and new methods to reduce the disease are needed. In this thesis, the use of the Sterile Insect Technique (SIT) against the African malaria vector Anopheles arabiensis was explored. The SIT relies on the releases of large numbers of sterilised males. If the sterile males are successful in competing for mates and the females use their sperm for fertilisation, the wild population is reduced. Ultimately, this can lead to a reduction in disease incidence. Sterilisation of the sperm cells occurs by ionising radiation, resulting in the death of the developing embryo after fertilisation. Somatic cells are also damaged, which can lead to a reduced mating competitiveness of the males.
In this thesis I investigated 1) the relationship between dose and induced sterility for pupal or adult stage irradiation, 2) sperm quantity and sperm length polymorphism and the influence of irradiation, 3) the use of stable isotopes to determine mating in mosquitoes, 4) the incidence of multiple mating in relation to irradiation, 5) the fitness of irradiated males in terms of survival and mating competitiveness, and 6) the use of a field cage for mating studies, and the small-scale feasibility of the SIT in Sudan.
Results showed that even though the dose-response curves between dose and induced sterility were largely similar for pupae and adults, irradiation of adults resulted in a better competitiveness compared to pupal irradiation. A negative relationship between dose and competitiveness was observed for pupal stage irradiation. In addition, radiation during the pupal stage affected the number of spermatozoa in the testes and the distribution of sperm lengths, but no impact on the incidence of multiple mating could be observed. Stable isotopes were used successfully to determine paternity in mating. Mating competitiveness of males irradiated as pupae could be improved by a three-fold increase in their number compared to un-irradiated males, but only for the partially-sterilising dose. The small-scale irradiation and transportation of insects in Sudan was feasible, and the preparation of the field cage for experiments successful.
It is concluded that from a biological viewpoint the irradiation of adults would be recommended; however, the feasibility of adult irradiation on a large scale is questionable. The next steps would be to scale up irradiation procedures to accommodate much larger numbers of insects, and to determine male competitiveness in the semi-field system in Sudan. However, many other factors including mass rearing, sexing, and release methodology, are of importance for an SIT programme and only when all components are in place can the true feasibility of the SIT in Sudan be determined.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Dicke, Marcel, Promotor
  • Knols, B.G.J., Co-promotor
Award date20 Jun 2008
Place of PublicationS.l.
Print ISBNs9789085049555
Publication statusPublished - 2008

Keywords

  • sterile insect release
  • genetic control
  • sterilization
  • ionizing radiation
  • stable isotopes
  • mosquito-borne diseases
  • malaria
  • anopheles arabiensis
  • mating competitiveness
  • sudan

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