Emergence of Zika Virus in Culex tritaeniorhynchus and Anopheles sinensis Mosquitoes in China

Zika virus(ZIKV)has been isolated from mosquitoes such as Aedes,Mansonia uniformis,and Culex perfuscus;However,the isolation of ZIKV from Anopheles sinensis and Culex tritaeniorhynchus has not yet been reported.In June and July2018,22,985 mosquitoes and 57,500 midges were collected in Jiangxi Province in southeastern China.Among them,six strains of ZIKV were isolated from mosquitoes:four from An.sinensis and two from Cx.tritaeniorhynchus.Molecular genetic analysis showed that the ZIKV isolated from An.sinensis and Cx.tritaeniorhynchus belonged to genotype 2 in the Asian evolutionary branch of ZIKV.In addition,the ZIKV strains isolated from An.sinensis and Cx.tritaeniorhynchus had amino acid substitutions identical to ZIKV strains prevalent in South America since 2015.This study is the first to isolate ZIKV from mosquito specimens collected in the wild of Jiangxi Province,China;This is also the first time that ZIKV has been isolated from An.sinensis and Cx.tritaeniorhynchus.Given that An.sinensis and Cx.tritaeniorhynchus have a very wide geographical distribution in China and even in eastern and southern Asia,the isolation of several strains of ZIKV from these two mosquitoes poses new challenges for the prevention and control of ZIKV infection in the mainland of China and countries and regions with the same distribution of mosquitoes.

Co-circulation of Aedes flavivirus,Culex flavivirus,and Quang Binh virus in Shanghai,China

Background:With increases in global travel and trade,the spread of arboviruses is undoubtedly alarming.Pathogen detection in field-caught mosquitoes can provide the earliest possible warning of transmission.Insect-specific flavivirus(ISFV)has been first detected in 1991 and documented worldwide in the latest ten years.Although infection with ISFVs is apparently limited to insects,an increase in the infection rate of mosquito-borne flaviviruses may be able to induce cytopathic effects in vertebrate cells during co-infection with other human pathogens.However,little is known whether ISFVs persist in most regions of China.Methods:During the mosquito activity season in 2016,a surveillance program was carried out to detect ISFVs in mosquitoes in metropolitan Shanghai,China.The presence of ISFVs was randomly tested in different species of mosquitoes using RT-PCR-based and hemi-nested PCR assays,following by the sequencing of PCR products.Sequences from positive pooled samples were compared with those deposited in GenBank.Thereafter,sequences of representative insect flaviviruses were used for further phylogenetic and molecular evolutionary analyses.Results:Our investigations showed:(1)the presence of Aedes flavivirus(AEFV)in 11/161 pooled samples(nine pools in Songjiang District,one pool in Huangpu District,and one pool in Qingpu District)of Aedes albopictus,(2)the presence of Quang Binh virus(QBV)in 10/195 pooled samples(all in Chongming District)of Culex tritaeniorhynchus;and(3)the presence of Culex flavivirus(CxFV)in 9/228 pooled samples(six pools in Pudong New Area,two pools in Huangpu District,and one pool in Chongming District)of Cx.pipiens.Furthermore,phylogenetic analyses of the gene sequences of envelope proteins indicated that Shanghai CxFV strains belonged to the Asia/USA genotype.The overall maximum likelihood estimation values(and 95%confidence interval)for CxFV,QBV,and AEFV in mosquitoes collected in Shanghai in 2016 were 1.34(0.66-2.45),1.65(0.87-2.85),and 1.51(0.77-2.70)per 1000,respectively.Conclusions:This study reveals the presence and the geographical distribution of ISFVs,and determines the genetic variation and the infection rate of ISFVs in Shanghai,China.At least,three insect flaviviruses including ISFVs,AEFV,CxFV,and QBV,co-circulate in this area.To our knowledge,this is the first report of AEFV in China.

Molecular epidemiology of mosquito-borne viruses at the China-Myanmar border:discovery of a potential epidemic focus of Japanese encephalitis

Background:Mosquito-based arbovirus surveillance can serve as an early warning in evaluating the status of mosquito-borne virus prevalence and thus prevent local outbreaks.Although Tengchong County in Yunnan Province-which borders Myanmar-is abundant and diverse in mosquitoes,very few mosquito-based arbovirus investigations have been conducted in the recent decade.Herein,this study aims to evaluate the presence and the diffusion of mosquito-borne pathogens,currently prevalent in this region.