Culex quinquefasciatus: status as a threat to island avifauna and options for genetic control

Abstract

AbstractThe avifauna endemic to islands is particularly susceptible to population declines and extinctions resulting from the introduction of non-native pathogens. Three pathogens of concern are the avian malaria parasites, the avian poxviruses, and West Nile virus—each of which can be transmitted byCulex quinquefasciatus, a highly adaptive and invasive mosquito.Culex quinquefasciatushas dramatically expanded its range in recent centuries and is now established throughout much of the tropics and sub-tropics, including on many islands that are remote from mainland landmasses and where this geographic separation historically protected island species from mosquito-borne diseases. The potential for ecological disruption byCx. quinquefasciatushas been particularly striking in the Hawaiian Islands, where the introduction and transmission of avian malaria and avian poxvirus led to the extinction of several endemic bird species, with many more at risk. WithCx. quinquefasciatusnow present in many insular communities and global trade and tourism increasing links between these areas, both to each other and to mainlands, there is growing concern that patterns of avian decline in Hawai‘i may be played out in other insular ecosystems. The implementation of traditional methods forCx. quinquefasciatuscontrol, including larval source management, is often impractical at large scale and when breeding sites are numerous and difficult to locate—typical issues associated with invasive species removal. One alternative approach would be the utilisation of genetic control methods, several of which have been successfully developed in other mosquitos such asAedes aegyptiand the malaria vectorAnopheles gambiae. However, the development of similar tools forCx. quinquefasciatushas been comparatively limited. Here we review the threat thatCx. quinquefasciatusposes as a vector of avian pathogens to island avifauna and discuss specific examples of at-risk bird populations on the islands of Hawai‘i, New Zealand and Galápagos. We also review the major options for the deployment of genetic control tools againstCx. quinquefasciatus, and discuss the current state of the field with a focus on radiation-based sterilisation, transgenic methods, and transinfections using the bacterial endosymbiontWolbachia.