Development of a population suppression strain of the human malaria vector mosquito, Anopheles stephensi

Background: Transgenic mosquito strains are being developed to contribute to the control of dengue and malaria transmission. One approach uses genetic manipulation to confer conditional, female-specific dominant lethality phenotypes. Engineering of a female-specific flightless phenotype provides a sexing mechanism essential for male-only mosquito, release approaches that result in population suppression of target vector species. Methods: An approach that uses a female-specific gene promoter and antibiotic-repressible lethal factor to produce a sex-specific flightless phenotype was adapted to the human malaria vector, Anopheles stephensi. Transposon- and site-specific recombination-mediated technologies were used to generate a number of transgenic An. stephensi lines that when combined through mating produced the phenotype of flight-inhibited females and flight-capable males. Results: The data shown here demonstrate the successful engineering of a female-specific flightless phenotype in a malaria vector. The flightless phenotype was repressible by the addition of tetracycline to the larval diet. This conditional phenotype allows the rearing of the strains under routine laboratory conditions. The minimal level of tetracycline that rescues the flightless phenotype is higher than that found as an environmental contaminant in circumstances where there is intensive use of antibiotics. Conclusions: These studies support the further development of flightless female technology for applications in malaria control programmes that target the vectors.