Mosquitoes, the primary vectors of arboviruses, harbor a diverse microbiome that plays a crucial role in their development, immunity, and vector competence, tThe composition of the mosquito microbiome is heavily influenced by the environment and habitats, Therefore, identifying the relationship between the habitat and the mosquito's microbial community can improve the overall understanding of mosquito biology, However, the microbiome profiles of Culex tritaeniorhynchus and Culex orientalis, known as transmission vectors of the Japanese encephalitis virus, are poorly understood. Using 16s rRNA Illumina sequencing, we hereby investigated the microbial profiles in these two mosquito species collected in several areas in Korea. Thirty-six prevalent bacterial familes were identified from these mosquito species. the microbial composition variation were primarily influenced by the mosquito collecting sites. Moreover, species biomakers were identified by utilizing the regional specificity of the mosquito microbiome. Based on the microbiome profiles representing high similarity, Culex orientalis may share an ecological niche with Culex tritaeniorhynchus.

Japanese encephalitis virus (JEV), a mosquito-borne pathogen, is the most important cause of viral encephalitis worldwide. The major vector mosquito of this virus, known as Culex tritaeniorynchus, is mainly live in paddy rice field in Korea. So Japanese encephalitis (JE) is a disease of rural areas. During urbanization, rice cultivated land has decreased also resulting the number of JE patients has decreased. However, recent outbreak of JE in Korea 2010, the patients distribution was not related with that of the mosquito. Therefore, this study was conducted to evaluate involving other mosquito species in the transmission of JEV. Five localities, JE reported in 5 years, have been selected to collect mosquitoes according their habitats (mountain, swap, cow shed, and downtown area) in 2012. Total 22,774 collected mosquitoes were pooled by species, date and site of collection. Of the 1,282 pools, eight (five were from Culex orientalis, one from Culex pipiens complex, and two from Aedes vexans) were found positive for flavivirus RNA in SYBR Green I-based real-time RT-PCR assay. The results of sequences blasting on NCBI showed that the flaviviruses from Cx. orientalis and Cx. pipiens complex were identified as JEV genotype V.

Culex orientalis is belonging to the mimeticus group of the genus Culex and shows various patterns of white pale spots on the wing and wing venation which cause an ambiguity to identify as this species. To confirm whether or not these variations are limited within the species, we observed 230 Cx. orientalis specimens collected in Korea and divided them into 51 variations according to their wing spots patterns. To compare a molecular similarity between the variations, the ITS2 regions of five major variations were analyzed. The results showed that there are more than 97% nucleotide sequence similarity between the variations as well as within a variation. This results suggest that the wing variations of Cx. orientalis are limited a within-species divergence. To further confirm, ITS2 regions of other species (Cx. mimeticus and Cx. jacksoni) in the mimetiucs group will be analyzed and compared with those of Cx. orientalis variations.

Field-collected populations of mayflies, Ephemera orientalis were tested for susceptibility to 10 different insecticides using a direct-contact mortality bioassay. Ephemera orientalis subimagoes were susceptible to the insecticides chlorpyrifos, fenitrothion and chlorfenapyr with LD50 values of 69.7, 78.8 and 81.9μg/♀, and adults had LD50 values of 71.9, 78.8 and 85.4μg/♀, respectively. Susceptibility ratios(SRs) of subimagoes and adults of E. orientalis to the 10 insecticides were 1.0 to1.2 folds. The mayflies showed higher susceptibility to organophosphates than to pyrethroids. The SRs of Anopheles sinensis to E. orientalis were 514 to 1,438 fold higher for organophosphates (LD50 values of 0.05 to 0.23μg/♀) and 62 to 1,155 fold higher forpyrethroids (LD50 values of 0.13 to 2.41μg/♀). The SRs of Culex pipiens to E. orientalis were 606 to 3,595 fold higher for organophosphates with LD50 values of 0.02-0.17μg/♀ and 81 to 1,365 fold higher for pyrethroids with LD50 values of 0.11- 1.83μg/♀. These results indicate that the use of ineffective insecticides will result in unsatisfactory control against field populations of the subimagoes and adults of E. orientalis. This work was supported by a research grant from the National Vector Control and Surveillance work performed by the Korean National Institute of Health.