Genetic analysis of Aedes aegypti captured at two international airports serving to the Greater Tokyo Area during 2012-2015.

The introduction of exotic disease vectors into a new habitat can drastically change the local epidemiological situation. During 2012-2015, larvae and an adult of the yellow-fever mosquito, Aedes aegypti, were captured alive at two international airports serving the Greater Tokyo Area, Japan. Because this species does not naturally distribute in this country, those mosquitoes were considered to be introduced from overseas via air-transportation. To infer the places of origin of those mosquitoes, we genotyped the 12 microsatellite loci for which the most comprehensive population genetic reference is currently available. Although clustering by Bayesian and multivariate methods both suggested that all those mosquitoes captured at the airports in Japan belonged to the Asia/Pacific populations, they were not clustered into a single cluster. Moreover, there was variation in mitochondrial cytochrome oxidase I gene (CoxI) haplotypes among mosquitoes collected in different incidents of discovery which indicated the existence of multiple maternal origins. We conclude there is little evidence to support the overwintering of Ae. aegypti at the airports; nevertheless, special attention is still needed to prevent the invasion of this prominent arbovirus vector.

First report on invasion of yellow fever mosquito, Aedes aegypti, at Narita International Airport, Japan in August 2012.

The invasion of the yellow fever mosquito Aedes aegypti at Narita International Airport, Japan was detected for the first time. During the course of routine vector surveillance at Narita International Airport, 27 Ae. aegypti adults emerged from larvae and pupae collected from a single larvitrap placed near No. 88 spot at passenger terminal 2 on August 8, 2012. After the appearance of Ae. aegypti in the larvitrap, we defined a 400-m buffer zone and started an intensive vector survey using an additional 34 larvitraps and 15 CO2 traps. International aircraft and passenger terminal 2 were also inspected, and one Ae. aegypti male was collected from the cargo space of an international aircraft from Darwin via Manila on August 28, 2012. Larvicide treatment with 1.5% fenitrothion was conducted in 64 catch basins and one ditch in the 400-m buffer zone. Twenty-four large water tanks were also treated at least once with 0.5% pyriproxyfen, an insect growth regulator. No Ae. aegypti eggs or adults were found during the 1-month intensive vector survey after finding larvae and pupae in the larvitrap. We concluded that Ae. aegypti had failed to establish a population at Narita International Airport.