Increased detection of Aedes albopictus in Belgium: no overwintering yet, but an intervention strategy is still lacking.

In 2013 and 2014, routine surveillance for invasive mosquito species was implemented in Belgium at 13 potential points of entry. Following the introduction of Aedes (Stegomyia) albopictus (Skuse 1895) to Belgium via a used tyre import company (Vrasene, Province of East Flanders) in July 2013, one female and 17 larvae were collected outdoors during a period of intensive surveillance in summer and autumn 2013, but no control measures were implemented. Although climatic conditions were suitable during the winter of 2013-2014, this reproducing population did not overwinter. Lack of genetic variation, incomplete diapause adaptation and egg desiccation due to long dry periods during diapause or competition with endemic species are possible reasons. More studies on the diapause/longevity of Ae. albopictus eggs in northern temperate climatic conditions and on the competition with endemic species in western and central Europe are warranted to assess the potential for this invasive mosquito to overwinter. Furthermore, following the detection of four Ae. albopictus larvae in a shipment of lucky bamboo at the port of Antwerp in August 2014, one female, one male, 11 pupae and six larvae were collected at the destined lucky bamboo company (Lochristi, Province of East Flanders) in autumn 2014. In this case, immediate control measures were successfully implemented at the nursery. Because of increasing threats and the absence of an invasive mosquito species control policy in Belgium, the need for a permanent vector surveillance and control plan has never been so high.