Global Health Impacts of Vector-Borne Diseases Workshop Summary (2016) / Chapter Skim
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A2 - Genetic Control of Aedes Mosquitoes - Luke Alphey, Andrew McKemey, Derric Nimmo, Marco Neira Oviedo, Renaud Lacroix, Kelly Matzen, and Camilla Beech
A2 - Genetic Control of Aedes Mosquitoes - Luke Alphey, Andrew McKemey, Derric Nimmo, Marco Neira Oviedo, Renaud Lacroix, Kelly Matzen, and Camilla Beech
Pages 106-125
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Genetic control of Aedes mosquitoes. Pathogens and Global Health 107(4)
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However, current mosquito control methods have limited effectiveness against some key species which breed in small dispersed bodies of water.
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Though some genetic strategies have been developed using classical genetics, such as the Sterile Insect Technique (SIT) (see section below: Population Suppression Strategies -- Sterile Males Section)
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Population Suppression Strategies -- Sterile Males The most familiar genetics-based population suppression strategy is SIT. This relies on the release of large numbers of sterile males to seek, court, and mate wild females, thereby reducing the reproductive potential of the target wild population.
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Wolbachia achieve a similar effect -- death of offspring of incompatible crosses -- in IIT, though the biochemical and genetic mechanism is unknown. Sterility -- death of most or all offspring -- can also be achieved by using dominant lethal alleles introduced into the genome by recombinant DNA methods, rather than by irradiation.
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. All control interventions place pressures on the target population that may select for various forms of resistance, and genetic control methods are no exception.
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Heterozygous sons will pass the transgene on to half of their offspring, resulting in some additional control, though the high fitness cost of a female-lethal trait means that the transgene will be rapidly eliminated from the target population unless maintained by periodic release of additional homozygous males. This is female-specific RIDL, fsRIDL, which has some similarities to the classical field female-killing (FK)
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, suggesting that expression may impose a significant fitness cost, and also perhaps that the unusual inverted repeat structure involved may be subject to some form of epigenetic silencing. Gene Drive Systems A refractory gene will only have an epidemiologically useful effect if it is present in a significant fraction of the target population.
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Some affinity may be found with classical biological control, where the intention is to introduce a parasitoid or predator to control a pest population, expecting that the biocontrol agent will establish and provide long-lasting control, albeit usually incomplete, for the indefinite future. As with classical biological control, there are concerns regarding the lack of control over the gene drive system once released, its unknown evolutionary trajectory post-release, and the essentially irreversible nature of a release, at least in the case of large-scale releases.
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Can Wolbachia Provide Both Refractoriness and a Gene Drive System? One striking exception to the slow progress with refractoriness and gene drive systems has come from work on Wolbachia in Ae.
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Though in principle the large-scale use of such systems may be reversible by further genetic intervention, restoring the status quo ante is at best uncertain; this irreversibility has been a major discussion point in respect of gene drive systems. In the case of Wolbachia, one may predict that the introduced strain will co-adapt with Ae.
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The use of Wolbachia, presented as "natural,"7 has largely avoided public concerns relating to the use of recombinant DNA methods. Public response to genetic control, either in general 7 http://www.eliminatedengue.com/, accessed October 18, 2012 and April 17, 2013.
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However, regulatory and social factors, while crucial to the adoption of any new technology, are not the main focus of this review. Field trials of genetic control methods known to the authors are: 1.
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Numerous research groups are developing exciting approaches; the first of these have successfully completed their first field trials. Genetic control may soon be deployed on a large scale, delivering clean, affordable, sustainable, scalable solutions to major human vector-borne diseases.
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2008. Guidance for contained field trials of vector mosquitoes engineered to contain a gene drive system: Recom mendations of a scientific working group.
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PLoS Neglected Tropical Diseases 2:e129. Brennan, L.J., B.A.
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2008. Towards a sterile insect technique field release of Anopheles arabiensis mosquitoes in Sudan: Irradiation, transportation, and field cage experimentation.
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phenotype for control of Aedes albopictus. PLoS Neglected Tropical Diseases 6:e1724.
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PLoS Neglected Tropical Diseases 6:e1797. O'Neill, S.L.
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2010. Modelling pulsed releases for sterile insect techniques: Fitness costs of sterile and transgenic males and the effects on mosquito dynamics.
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