Entomological Surveillance for Flaviviruses at Migratory Bird Stopover Sites in Hokkaido, Japan, and a New Insect Flavivirus Detected inAedes galloisi(Diptera: Culicidae)

Abstract

To investigate the possible spread of West Nile virus (WNV) into Japan, we carried out entomological surveillance for flaviviruses at migratory bird stopover sites in Hokkaido, Japan, during 2003-2006. A total of 3,826 mosquitoes, identified as 15 species in five genera, were collected and 2,465 of these were grouped into 123 pools that were assayed for cytopathic effects on mosquito and mammalian cell cultures and for flavivirus RNA by reverse transcription-polymerase chain reaction using flavivirus universal primer sets for fragments of the NS3 and NS5 genes. Neither WNV nor other mosquito-vertebrate transmitted flaviviruses were detected in mosquitoes collected at any of the sites in Hokkaido, but five Culex flaviviruses and one novel Aedes galloisi flavivirus were identified from Culex pipiens L. s. l. and Aedes galloisi Yamada, respectively. Genetic and phylogenetic analyses based on the partial NS5 nucleotide sequences classified Aedes galloisi flavivirus with the insect flavivirus, but distant from Cell fusing agent, Kamiti river virus, and Culex flaviviruses, showing <74% sequence identities. Polymerase chain reaction-based bloodmeal analysis of 79 females showed that all of the Aedes and Ochlerotatus mosquitoes fed on mammals (deer and humans), whereas, Cx. pipiens s. l. mosquitoes fed on both of avian (ducks and sparrows, 85.7%) and mammalian hosts (dog, 14.3%). We suggest that to date WNV has not become established in Japan.

Insect-specific flaviviruses, a worldwide widespread group of viruses only detected in insects

“…Japan (Hoshino et al, 2012), or in India from Culex tritaeniorhynchus (Datta et al, 2015) (Table 1).…”

“…In Europe, several species of ISFVs have been detected in field-collected mosquitoes from Italy, Portugal, Spain, United Kingdom, Czech Republic, and Greece (Calzolari et al, 2012;Cerutti et al, 2012;Osório et al, 2014;Vázquez et al 2012, Papa et al 2014; furthermore, sequences related to those viruses were detected worldwide (Pabbaraju et al, 2009;Hoshino et al, 2012;Ochieng et al, 2013;Datta et al, 2015) (GB: EF423170-1), strongly suggesting, even without the direct isolation, ISFVs show marked differences from the other flaviviruses and could represent a primordial form of flaviviruses with replication restricted to insects and unable, or slightly adapted, to infect vertebrate cells (Cammisa-Parks et al, 1992). In this article, isolated and putative viruses of this group are listed according to published works and sequences, and available data on geographical spread and ecological features are reported.…”

Distribution and Mosquito Hosts of Chaoyang Virus, a Newly Reported Flavivirus From the Republic of Korea, 2008–2011

“…Mosquito-borne ßaviviruses are a large and divergent group and have been further divided into viruses in mosquito-borne Culex, causative agents of encephalitis and transmitted by Culex spp., and mosquito-borne Aedes, causative agents of hemorrhagic complications and transmitted by Aedes spp. Insect-speciÞc ßavivi-ruses that appear to only infect mosquitoes have been found worldwide (Hoshino et al 2007(Hoshino et al , 2012Blitvich et al 2009;Huhtamo et al 2009;Junglen et al 2009;Wang et al 2009;Tyler et al 2011;Cook et al 2012). Culex ßavivirus was Þrst isolated from Culex pipiens collected in Japan (Hoshino et al 2007).…”

Human Infection with West Nile Virus, Xinjiang, China, 2011

“…It has been reported in Africa, Asia, Europe, Australia, and North America, and is recognized as the most globally widespread mosquito-borne flavivirus ( 2 ). Isolation of WNV has previously been attempted in China, Japan and South Korea; however, no virus has been isolated ( 3 – 5 ). We report isolation of WNVs from mosquitoes in Xinjiang Uyghur Autonomous Region in western China.…”