The intracellular endosymbiont bacterium Wolbachia is currently considered the most abundant in arthropods and has also been isolated from nematodes, amphipods, isopods, mites and spiders. Recently, Wolbachia-based research was focused on the control of disease vector-population, such as several mosquitoes such as genus Aedes and Anopheles which cause dengue fever and malaria, respectively. For the analysis of regional difference between vector mosquito Aedes albopictus and Wolbachia, we selected different regions and collected Ae. albopictus which were distinguished with mountain chain and waterway. Whole genomic DNA were extracted from collected specimens with 9 regions. PCR analysis and sequencing were accomplished in each specimen for Wolbachia detection and identification using WSP gene. As a results, almost mosquitoes were infected with two strain of Wolbachia both wAlbA and wAlbB. However, regional separation of vector mosquitoes, wAlbA strain of Wolbachia were showed more than 98% sequence similarity. In this study, we first reported that Wolbachia infection and type of Wolbachia in Korea and endosymbiont Wolbachia was showed highly sequence homologies.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging disease, causing high fever, thromobocytopenia, leukopenia, gastrointestinal simptoms (vomiting, diarrhea), hemorrhage and multiorgan dysfunction. It was known that Haemaphysalis longicornis (H. longicornis), a major tick in Korea, is the principal vector for severe fever with thrombocytopenia syndrome virus (SFTSV). Firstly, to investigate the existence and prevalence of SFTSV in the country, we collected the ticks in 9 provinces in South Korea and detected SFTSV from H. longicornis ticks from 2011 to 2012. And we also investigated SFTSV infection in ticks collected from healthy humans without SFTS symptom and their residential areas. From the former study, we collected 13,053 ticks, and H. longicornis (90.8%, 11,856/13,053) was the most abundant among them. The minimum infection rate (MIR) of SFTSV in H. longicornis was 0.5% (59 pools). From the later study, totally 422 ticks of 8 species were collected from humans and at their neighborhood throughout the nation from May to October, 2013 and SFTSVs were detected from 12 pools (5.7% MIR) by RT-PCR. Finally, we diagnosed 35 patients by detecting SFTSV gene with their sera, and isolated 26 SFTSVs among them in 2013. These findings indicate that SFTSVs are prevalent and SFTS is probably endemic in Korea.

The intracellular endosymbiont bacterium Wolbachia is currently considered the most abundant in arthropods. Many Wolbachia manipulate host reproductive systems, it lead to male-killing, cytoplasmic incompatibility, parthenogenesis and feminization of genetic males with large impact on host ecology and evolution in arthropods. In this study, we investigated the distribution of Wolbachia infection in Ae. albopictus according to geographical distribution. We selected 9 areas and collected Ae. albopictus, these areas were distinguished with mountain chain and waterway. Whole genomic DNA were extracted from collected specimens and PCR analysis were accomplished in each specimen using Wolbachia specific primers such as 16S and WSP genes. As a results, we collected 730 Ae. albopictus at least 30 specimens in each area. Wolbachia infection rate showed different patterns between geographical region. Cheonbook, Cheonnam and Yeongdong showed 100% infection rate followed by Jeju (97%), Chungchung (88%), and Gyungnam (85%) with two Wolbachia marker genes. Our results indicated that Ae. albopictus are commonly infected with Wolbachia, it is possible that Wolbachia may act as endosymbiont in Ae. albopictus regardless of geographical region. Although, low infection rate of Wolbachia, we need continuous survey for the evaluation of Wolbachia strain within Ae. albopictus as a vector of dengue fever.

Habitats for migratory birds provide good blood source for blood sucking insects including mosquitoes, which may lead to high population mosquito species. This study was intended to know mosquito fauna in habitats for migratory birds that have preference for bird’s blood. We selected 7 locations for migratory birds (Ansan: a great reedy marsh in lake of Shihwa; Cheonan, Gyeongju, and Pyeongtaek: pine forest; Seosan: a reclaimed land near bay of Cheonsu ; Ulsan: great bamboo forest around Teahwa river) and subdivided each location with four habitats (forest, swamp, cow shed and downtown area) as mosquito collecting site. We used two types of trap for mosquito collection such as CDC black light trap and BG Sentinel trap. Additionally, we use black light and dry ice as an attractive source, respectively. A total of 27,615 mosquitoes representing 9 genera and 18 species were collected. In Ansan, 9 genera and 17 species were collected and in the other locations only 11 to 12 species. Representing by habitats shows this; in forest 9 genera and 17 species, in swamp 8 genera and 16 species, in cow shed 6 genera and 12 species, in downtown 8 genera and 17 species. The dominant species was Culex pipiens (60%) followed by Aedes vexans (11%), Anopheles spp. (8%), Aedes albopictus (7%), and Armigeres subalbatus (5%).

Repellency of 20 plant essential oils to malaria main vector in the Republic of Korea (ROK), Anopheles kleini, was evaluated using skin direct contact bioassay. Anopheles kleini showed the highest repellency to Pelargonium graveolens with EC50 value of 0.244 mg/cm2, followed by Pinus sylvestris and Cinnamomum camphora with EC50 values of 0.484 mg/cm2 and 0.862 mg/cm2. The lowest repellency of An. kleini was revealed from Clary sage oil with EC50 value of 4.665 mg/cm2. Anopheles kleini did not demonstrated any repellency to Lemon, Orange, Neem, Coconut and Olive oil over 20 mg/cm2. Major repellent constituents of Geranium, Pine and Camphora oil were analyzed and identified using Mass-data, GC and GC-Mass. Major constituent of Geranium were β-citronellol (37.0%) and Camphora, 1,8-cineole (35.8%) and Pine, α-terpineol (39.5%). Anopheles kleini showed higher repellency to β-citronellol and 1,8-cineole than to DEET and IR3535 and did not showed any repellency to sabinene and γ-eudesmol over 20 mg/cm2. Residual repellent time of 1,8-cineole and β-citronellol were 26 and 41 min, respectively and DEET, 84 min and IR3535, 102 min. In the light of global efforts to reduce the level of highly toxic synthetic repellents, the three essential oils and their major constituents described merit further study as potential biorepellents for the control of An. kleini populations

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.

Insecticide resistance and activation of the metabolic detoxification enzymes of female Culex pipiens pallens by the blood meal were assessed using a micro-application bioassay and micro-plate enzyme activity assays. Four group of Cx. pipiens pallens were used, a susceptible non-engorging group at seven days after emerging, SNE7 Cp; a resistant non-engorging group at seven days after emerging, RNE7 Cp; a resistant engorged group at one day after blood feeding and a resistant engorged group at seven days after blood feeding, REG7 Cp. Insecticide resistance of Cx. pipiens pallans was increased by the blood feeding. Based on LC50 values, SNE7 Cp demonstrated >50 fold of higher susceptibility to all tested insecticides when compared with RNE7 Cp. RNE7 Cp showed higher susceptibility to all tested insecticides than REG1 Cp and REG7 Cp with a relative susceptibility LC50 (SRLC50) of 25.8 to 50.0 and 25.0 to 48.8. In micro-plate enzyme assays, the metabolic detoxification enzyme activity of Cx. pipiens pallans adult females was increased by the blood feeding. Activation of non-specific esterases (EST), glutathione-S-transferase (GST) and mixed function oxidase (MFO) in RNE7 were higher than in SNE7 and the all tested enzymes in REG1 and REG7 demonstrated significantly higher enzyme activation than RNE7, except for activation of GST in REG1. Activation of MFO in REG1 and REG7 were 209.4- and 74.6- fold higher than in REG7, respectively. Non-specific esterases (EST) and glutathione-S-transferase exhibited < 10 fold of higher Rr values. These results may be significant in terms of the criteria that are used to evaluate resistance, because blood fed female mosquitoes may show enhanced expression of the resistance phenotype, possibly allowing for earlier detection of insecticide resistance.