Culex tritaeniorhynchus Gile is a major vector of Japanese encephalitis in China. The population genetics study is crucial as it helps understanding the epidemiological aspects of mosquito-brone diseases and improving vector control measures. Here, the genetic population structure of C. tritaeniorhynchus in the mainland China were estimated using the cytochrome c oxidase subunit 1 (COI) DNA barcodes region. 485 individuals of C. tritaeniorhynchus were collected from 38 sampling sites in 21 geographic populations in the mainland China. In total, 485 sequences were used to explore the population structure and genetic diversity. The results showed that the populations of C. tritaeniorhynchus had high haplotype diversity (Hd ¼ 0.98, with 303 haplotypes), low nucleotide diversity (p ¼ 0.02245) and high gene flow (Nm ¼ 47.11) with two maternal lineages and four groups. An AMOVA indicated that 98.8% of the total variation originated from variation within populations. In addition, the population genetic structure exhibited by C. tritaeniorhynchus filling the vacant of the genetic structure in the mainland China. Human activities may also assist mosquito movement and migration. Gene flow among the populations of C. tritaeniorhynchus can facilitate the spread of insecticide resistance genes over geographical areas, and it will be a challenging for controlling the populations.

Background: In 2009, China CDC found the distribution of Culex tritaeniorhynchus and Aedes albopictus in Motuo county, Linzhi, Xizang and isolated the epidemic encephalitis V virus from Culex tritaeniorhynchus. However, with the road opend in Motuo County, the trade between people and mosquitoes transmission were more frequent. To illustrate patterns of mosquito population in Linzhi, Xizang, a mosquitoes surveillance was carried.Methods: Adult mosquitoes were collected by light traps and human landing catches, larva by container survey in six counties of Linzhi during August and September 2019. The trapped adult mosquitoes were initially counted and identified according to morphological criteria, and a part of mosquitoes were further identified by PCR. The monitoring data were recorded by Excel 2007, analyzed by SPSS 20.0 software and R.Results: Eight species of mosquitoes belonging to four genera were identified. Culex pipiens pallens (86.80%), Armigeres subalbalus (5.29%) and Aedes vexans (2.99%) were the top three species coolected by 164 light traps on 12 nights with the average mosquito density was 21.20 (mosquitoes per trap per night); Aedes albopictus were only collected in Chayu County Xiachayu Town by human landing catches with high average mosquito density (26.33 mosquitoes per hour per person). The larva were collected from waste tires, cement tanks and drums in Bomi, Milin and Lang Counties. The results of molecular identification are consistent with morphological identification. Aedes albopictus and Culex orientalis were newly recorded species for the first time. It is preliminarily speculated that there is a high potential risk of dengue fever in Xiachayu Town and a certain epidemic risk of Japanese encephalitis, while the risk of malaria is low in Linzhi.Conclusion: Mosquitoes had heterogeneous distribution throughout Linzhi, Xizang. The dominant mosquito species are Culex pipiens pallens. It is emphasized to carry out mosquito surveillance again during the peak period of mosquito activities so as to better understand the distribution and composition of local mosquitoes and assess the mosquito-borne disease risk in this area.