Novel genetic and biological control methods for an invasive insect pest.

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Aedes albopictus is an invasive mosquito species that transmits human (e.g. Dengue and Chikungunya) and livestock viruses in many countries. It has been spreading steadily through Europe over the course of the last decade, leading to fears that in combination with rising temperatures it may be responsible for major viral epidemics. Furthermore, the mosquito causes severe daytime biting nuisance. Its spread through the south and east USA, where it is now the number one cause of biting complaints, has led to human behavioural change as people spend more time indoors to avoid it. It would therefore be desirable to (i) reduce the frequency with which people are bitten by the mosquito, e.g. by suppressing the mosquito population and (ii) reduce the vectorial capacity of the mosquito population. With such tools, either or both could be applied, as appropriate. Suppression: Mass-release of sterile males can give effective, species-specific, environmentally friendly suppression of target populations, and has done so in large-scale programs against some major agricultural pests. Advances in genetics make genetics-based sterile-release a potentially attractive new strategy for mosquito control (Release of Insects carrying a Dominant Lethal gene, RIDL)1-2. Following success in Aedes aegypti2, we are attempting to transfer this technology to Aedes albopictus. So far we have successfully achieved transformation and also have preliminary data indicating that we can achieve the necessary genetics. The student will develop this work. Reduced vectorial competence: Ae. albopictus in nature are naturally infected with two strains of the inherited intracellular bacterium Wolbachia. Wolbachia can manipulate host reproduction to their own ends using cytoplasmic incompatibility (CI), providing an ability to spread rapidly through populations. It has recently been found that certain strains of Wolbachia (including wMel in Drosophila) are able to block or reduce the development or dissemination of various viruses and filarial nematode parasites in Drosophila and in Aedes aegypti mosquitoes3,4. These data have implications for the control of a variety of insect-borne pathogens of medical and agricultural importance. The wMel strain of Wolbachia will be transferred from D. melanogaster into a tetracycline-cured line of Ae. albopictus using established techniques of cytoplasm transfer, a line selected for high rates of maternal transmission, and effects on Dengue and Chikungunya transmission tested in this line. The CI and immune status will be analysed by crossing and qRT-PCR expression analyses. A unifying feature of these approaches is that they all have their impact via modified mosquitoes mating wild mosquitoes in the field. Quantitative measures of strain performance that would impact this (e.g. mating competitiveness, longevity, flight ability, fecundity, etc as appropriate) will therefore form a significant part of the student's work; data from these experiments will be used to parameterise mathematical models of mosquito populations and also cost-benefit analyses for the more promising strains and strategies. The possibility of combining RIDL and Wolbachia approaches to develop innovative refractory-plus-suppression strategies will also be examined. 1 Thomas, D. D., Donnelly, C. A., Wood, R. J. & Alphey, L. S. Insect population control using a dominant, repressible, lethal genetic system. Science 287, 2474-2476 (2000). 2 Phuc, H. K. et al. Late-acting dominant lethal genetic systems and mosquito control. BMC Biology 5, 11, doi:doi: 10.1186/1741-7007-5-11 (2007). 3 Kambris, Z., Cook, P. E., Phuc, H. K. & Sinkins, S. P. Immune activation by life-shortening Wolbachia and reduced filarial competence in mosquitoes. Science 326, 134-136 (2009). 4 Hedges, L. M., Brownlie, J. C., O'Neill, S. L. & Johnson, K. N. Wolbachia and virus protection in insects. Science 322, 702 (2008).