Trombiculid mites are known to be the vector of scrub typhus by transmitting rickettsial pathogen, Orientia tsutsugamushi, to human. In this study, we tried to establish a monitoring system for trombiculid mites using chigger mite collecting traps instead of the conventional rodent-capture method. For selection of collecting points, 10 environmental points were chosen from three regions (Taean, Jinan and Chungju) and two field collections were performed in spring (March-May) and autumn (October-November) seasons from 2013 to 2014. Among 10 environmental points, waterway (37.9%), grass field (28.0%), rice field and field near mountain side (11.4%) and reservoir/wet field (7.3%) showed high collecting rates and they should be included for the representative collecting points for surveillance using chigger mite collecting trap. In order to test the possibility that the dried chigger mites from collecting trap can be used for detection of O. tsutsugamushi, we pooled 30, 10 and 5 chigger mites separately and performed the nested PCR. The infection of O. tsutsugamushi was successfully detected from 5 chigger mites pooling sample. This study shows that chigger mite collecting trap could be an alternative method for monitoring system of scrub typhus vectors.

There are over 3,000 different species of mosquitoes throughout the world; currently 56 species are reported in Korea. Mosquitoes can act as vectors for many disease-causing viruses and parasites during blood sucking. Various species of mosquitoes are estimated to transmit various types of disease to more than 700 million people annually in Africa, South America, Central America, Mexico, Russia, and much of Asia, with millions of resultant deaths. At least two million people annually die of these diseases, and the morbidity rates are many times higher still. To prevent the spread of diseases, KNIH (Korea National Institute of Health) used three categorized methods; identifying or taxonomic analysis of mosquitoes, detecting virus caring mosquitoes, and detecting malaria from Anopheline mosquitoes. We have proved that taxonomic analysis using DNA barcording method (COI gene) is useful to complement identification of mosquito species. In detecting virus, we have reported Cx. orientalis as a new potential Japanese encephalitis virus (JEV) vector. We also reported that the Anopheline mosquito species composition and Plasmodium vivax infection rates in malaria hot spot in Korea.

Aedes albopicuts, known as asian tiger mosquito or forest mosquito, is characterized by its black and white strips on legs and body. Ae. albopictus is an important vector mosquito for the transmission of many viral pathogens such as dengue fever and chikungunya fever. Unlike other mosquito, Ae. albopictus attacks people mainly during the daytime in the forest. To evaluate the diel activity of Ae. albopictus, three times mosquito collecting were conducted using BG Sentinel trap with dry ice in bamboo forest in Damyang-gun, Jeoullanam-do, in South Korea from August to September, 2009. Captured mosquitoes were counted and released every one hour during 25 hours experiment time. The result showed that Ae. albopictus activity began with sun rising at approximately 09:00, with peak in the early evening between 16:00 to 19:00, and ended with sunset at 21:00. Among the several factors affecting on the mosquito activity, light intensity seems to be a main factor. Especially, if the light intensity is over some threshold, it negatively effects on the activity of Ae. albopictus.

As a part of disease vector and possible overseas inflow caused by global warming monitoring around airport and port area, the distribution of domestic mosquitoes was investigated using BG-sentinel trap. Mosquitoes were collected during 5-days per each area in early September, using 10 traps in Cheongju (airport) and 15 traps in Pyeongtaek (port). The numbers of mosquitoes collected in Cheongju and Pyeongtaek area were 1,762 including 10 species and 1,042 including 11 species respectively. In Cheongju, Aedes albopictus (657 individuals, 37.3%) and Culex pipiens complex (415 individuals, 23.6%) were dominant species; while in Pyeongtaek, Cx. pipiens complex (806 individuals, 77.4%) was dominant followed by Anopheles spp. (90 individuals, 8.6%) and Ochlerotatus koreicus (79 individuals, 7.6%). Similar species were collected in both Choengju and Pyeongtaek area. Although most species collected in both Cheongju and Pyeongtaek area were the same, Cx. inatomii was only collected in Pyeongtaek. In case of the Genus Aedes, more number of Ae. albopictus was collected compared to Oc. koreicus in Cheongju; while Oc. koreicus was more in Pyeongtaek. In case of the genus Culex, the individuals belonging to the vishinui group were collected such as Cx. bitaeniorhynchus, Cx. tritaeniorhynchus and Cx. orientalis. This study may provide basic information for efficient prevention of vector mosquito and potential overseas inflow of diseases, also we would try to expand different area in Korea.

A surveillance of chigger mites was conducted to clarify the incidence of scrub typhus vectors by new chigger mite collecting traps instead of trapping wild rodents for surveillance from each 4 collection points of 5 regions from September to November 2012 in Korea. During the surveillance period, 2,829 chiggers were collected and 10 species of 4 genera were identified. The first appearance of chigger mite and patients was 39 week (9.19~9.25) and the density of chigger mites had the peak in 43 week (10.17~10.23) and the density of patients had the peak in 44 week (10.24~10.30), respectively. In Goryeong-gun, a total of 1,797 mites representing 4 genera and 6 species were collected and the predominant species were Leptotrombidium scutellare (86.0%), L. pallidum (6.5%) and L. palpale (4.7%) whereas, In Gurye-gun, a total of 89 mites representing 2 genera and 3 species were collected and the predominant species were L. scutellare (46.5%) and L. palpale (36.2%) in similar to the natural environment. The high collecting rates were recorded at rice field (71.8%) and waterway (11.6%). This result shows that the surveillance of scrub typhus vectors by new chigger mite collecting trap is useful as an eco-friendly method.

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%).

Trombiculid mites are known to be the vector of tsutsugamushi disease by transmitting Orientia tsutsugamushi to human. Although the classification of trombiculid mites is necessary for vector surveillance, their classification by morphological observation is only possible at the larval stage and not easy because of similar shapes as well as tiny body sizes. Further the classification need the specimen production process, it takes much time and the accuracy of classification is changed according to the technology of the researcher. The internal transcribed spacers (ITS) regions of 8 trombiculid mite species were analyzed by amplification using tick common ITS primer sets. We designed molecular marker sets for the identification of five Leptotrombidium species, the lengths of marker L. orientale (1078 bp), L. pallidum (820 bp), L. palpale (1202 bp), L. scutellare (447 bp) and for L. zetum (621 bp) and three Neotrombicula species, the lengths of marker N. gardellai (264 bp), N. japonica (460 bp) and N. kwangneungensis (309 bp) based on alignment of ITS sequences. The markers will be helpful for exact classification of trombiculid mites. This study is the first report on molecular marker of ITS regions of trombiculid mites.

We conducted a investigation for dispersal ability of Aedes albopictus, a dengue vector mosquito, using mark-release-recapture method in Korea. A certain number of fluorescence marked Ae. albopictus was released in four different habitats – urban (Cheonan), suburban (Jochiwon), port (Pyeongtaek), and airport (Cheongju), and sticky traps and BG-traps were used to recapture the mosquito in designated time period. In case of urban and suburban areas, 100 sticky traps were used in 3-week period for both regions, and 19 BG-traps and 15 BG-traps were used in 36-hour period for urban and suburban areas respectively. Using sticky trap, 21 from 1,300 released mosquitoes (1.62%) were recaptured in urban area; while in suburban area, only 2 individuals (0.1%) were recaptured. Most of them were recaptured within 100m from releasing point and about 40% were within 20m distance. When BG-traps were used, 35 from 900 released mosquitoes (3.8%) were recaptured in urban area; while 26 mosquitoes (2.8%) were recaptured in suburban area. The maximum distance of dispersal was 200m in urban and 100m in suburban area, while most of them were recaptured in 50 ~ 80m range. In case of port and airport area, 15 and 10 BG-traps were used respectively to recapture 1,000 released mosquitoes in 5-day period. In port area, 23 mosquitoes (2.3%) were recaptured; while 166 mosquitoes (16.6%) were recaptured in airport area. The maximum distance of dispersal was 130m in both areas; while most of them were recaptured in 50m range. In conclusion, Ae. albopictus has a narrow dispersal range compared to other mosquitoes, a typical characteristic of genus Aedes, and their dispersal ability is greatly affected by various environmental factors. These results can provide basic information for effective prevention of Ae. albopictus and overseas inflow of dengue fever.

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

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.