Identification of Japanese encephalitis virus genotype Ⅰ from mosquitoes in Baoshan,Yunnan

Objective To investigate the distribution of mosquitoes and their natural infection with mosquito-borne viruses in Baoshan of Yunnan province,and provide scientific evidence for the prevention and control of mosquito-borne diseases. Methods Mosquito samples were collected by using mosquito traps in the night from houses and livestock stables in villages in Baoshan in September 2015. The mosquito samples were used to detect the viral RNA with Reverse transcription-polymerase chain reaction (RT-PCR) using Flavivirus,Alphavirus,Bunyavirus and Japanese encephalitis virus (JEV) primers,and positive specimens were sequenced for C/prM gene for homology and phylogenetic analysis. Results A total of 8 202 mosquitoes in 3 species were collected in Longyang district of Baoshan. Culex tritaeriorhynchus, Anopheles sinensis and Armigeres subalbatus accounted for 88.50%(7 259),11.43%(937)and 0.07%(6)of the total,respectively. Thirty mosquito batches were detected by using RT-PCR,and JEV RNA were detected from 14 batches of Cx. tritaeriorhynchus. The sequences of C/prM genes of the 14 JEV strains were obtained. Homology and phylogenetic analysis showed that the 14 JEV strains were in the same clade of genotype Ⅰ(G-Ⅰ)strains of JEV from GenBank,indicating they belonged to G-Ⅰ, and all the JEV strains detected were closely related to the JEV G-Ⅰ strains from Tengchong county of Baoshan in 2007 and adjacent Mangshi and Ruili counties of Dehong in 2010. Conclusion Cx. tritaeriorhynchus was dominant mosquito species and the major transmitting vector of JEV in Baoshan. JEV G-Ⅰ was confirmed to circulate in the area. It was first time to detect JEV G-Ⅰ in Baoshan since 2007.