We conducted nationwide West Nile virus (WNV) surveillance targeting mosquitoes and dead birds to reveal whether the virus and its potential vectors are present in Japan. A total of 32,145 mosquitoes and 742 dead birds were collected from April 2004 through March 2007. The species of most of the mosquitoes collected over the 3 years were Culex tritaeniorhynchus (47.82%) and Anopheles sinensis (28.49%), and other species included Aedes albopictus (6.75%), the Cx. pipiens group (Cx. pipiens pallens and Cx. pipiens molestus: 5.37%), Ae. vexans nipponii (2.54%), Armigeres subalbatus (1.08%), and Ae. japonicus (0.95%). As for the dead birds, most were members of the order Passeriformes (456 specimens), which included several crow species, and the other orders included Anseriformes, Columbiformes, and Ciconiiformes (78, 66, and 36 specimens, respectively). All specimens tested negative for WNV RNA by reverse transcriptase polymerase chain reaction (RT-PCR) in the 2004-2005 period and by real-time RT-PCR in the 2005-2006 and the 2006-2007 periods. Our surveillance provided no evidence for WNV in Japan as of the end of the surveillance period; however, it revealed that several species of potential WNV vectors are distributed widely in Japan, which suggests that WNV in principle could be transmitted by the potential vectors if introduced. Thus, it is essential to take continued precautions against WNV introduction.
(Research Team for Environmental/Enzootic Diseases)
References:
Shirafuji H. et al. (2011) Zoonoses and Public Health, 58: 153-157
