There’s no doubt about it: the tiger mosquito is at the door! A colony was spotted in a tyre plant close to the port of Antwerp; several dozen individuals, like some kind of vanguard. It was a group of researchers from Gembloux Agro-Bio Tech (Université de Liège) who discovered the first specimen, and sounded the action stations at the Institute of Tropical Medicine in Antwerp. Because this mosquito, originally from South-East Asia, is the vector of serious diseases such as dengue fever or chikungunya and it is... anthropophilic.

Slimane Boukraa smiled when he checked his mosquito trap on 7 July last year at the factory in Vrasene (Antwerp): he had a good catch, with hundreds of insects in the trap. Once back at the laboratory, the researcher from Gembloux Agro-BioTech/Université de Liège (Functional and Evolutionary Entomology Unit) embarked upon the slow and fastidious task of identifying each insect, one by one. With his sharp eye, Slimane can recognise the majority of mosquitoes with the naked eye, confirming them under the microscope. “When I was holding it with the tweezers, I immediately recognised it as the tiger mosquito”, he tells us.  “Its black and white stripy legs are very characteristic”. There was only one among the 500 mosquitoes caught; all the others belonged to the already well-established and known species in Belgium. Only one, but it was an important discovery. This tropical mosquito had already been spotted once before in the same factory in 2000, but hadn't reappeared since, despite a major detection campaign between 2007 and 2011. This second entry proves that its arrival in Belgium some 15 years ago wasn’t accidental.between 2007 and 2011. Thjgneagneeappe,  speciaitoes with the naked eye, confirming them with the Aedes albopictus, its scientific name, has clearly found a weak point...

The company in Vrasene imports used tyres essentially from Japan and the United States to recycle them. For reasons which still remain unknown, the mosquitoes like to lay their eggs in tyres. They often find a bit of stagnant water there, but there are undoubtedly also other elements that attract them: the colour black, a certain level of acidity, the absence of predators, etc. In fact, further investigations uncovered tiger mosquito larvae in small pools of stagnant water inside the tyres. "What’s more", adds S. Boukraa, "a genetic analysis of the adult specimen caught in the trap shows that it’s a strain 99% identical to the stain established in the USA. Our mosquito very probably comes from America. It probably arrived here via the port of Antwerp in a big cargo ship". Under the direction of Professor Frédéric Francis, Slimane Boukraa published his research in the magazine Parasite (1).

(1) Boukraa Slimane, Raharimalala Fara Nantenaina, Zimmer Jean-Yves et al, Reintroduction of the invasive mosquito species Aedes albopictus in Belgium in July 2013, in Parasite (Paris, France) (2013), 20(54)