Surveillance of invasive Aedes mosquitoes along Swiss traffic axes reveals different dispersal modes for Aedes albopictus and Ae. japonicus

Author summary Because of global trade of used tyres and ornamental plants, invasive mosquitoes of the genusAedesare spreading passively between continents. Within continents, adults are frequently travelling along roads as hitchhikers in motorised vehicles and may then colonise new areas. Because someAedesmosquitoes are competent to transmit diseases they threaten public and veterinary health. In Europe, the Asian tiger mosquito,Aedes albopictusis of particular concern as it is a vector of chikungunya, dengue and Zika virus. While its distribution in southern Europe is well documented, its dispersal modes across the Alps remain poorly investigated, preventing a projection of future scenarios beyond its current range in order to target mosquito control. To monitor the introduction of invasiveAedesmosquitoes beyond the Alps we placed traps at motorway service areas across Switzerland. Between 2013 and 2018 we identified three invasiveAedesspecies, includingAe.albopictus,Ae.koreicus(Korean bush mosquito) andAe.japonicus(Japanese bush mosquito). Based on the frequency and distribution patterns we conclude thatAe.albopictusandAe.koreicusare being passively spread primarily along the European route E35 from Italy to Germany, whileAe.japonicushas been expanding its range across Switzerland mainly through active dispersal. Over the past three decades, Europe has witnessed an increased spread of invasive aedine mosquito species, most notablyAedes albopictus, a key vector of chikungunya, dengue and Zika virus. While its distribution in southern Europe is well documented, its dispersal modes across the Alps remain poorly investigated, preventing a projection of future scenarios beyond its current range in order to target mosquito control. To monitor the presence and frequency of invasiveAedesmosquitoes across and beyond the Alps we set oviposition and BG-Sentinel traps at potential points of entry with a focus on motorway service areas across Switzerland. We placed the traps from June to September and controlled them for the presence of mosquitoes every other week between 2013 and 2018. Over the six years of surveillance we identified three invasiveAedesspecies, includingAe.albopictus,Ae.japonicusandAe.koreicus. Based on the frequency and distribution patterns we conclude thatAe.albopictusandAe.koreicusare being passively spread primarily along the European route E35 from Italy to Germany, crossing the Alps, whileAe.japonicushas been expanding its range from northern Switzerland across the country most likely through active dispersal.