A surveillance of chigger mites was performed to monitor the incidence of scrub typhus vectors at four environmental collection points in two locations (Sunchang and Haenam) in the Honam region of Korea from August to December 2023. During the surveillance period, 4,174 chigger mites were collected and the predominant species were Leptotrombidium scutellare (94.3%). The density of chigger mites had the peaked at 44 week (10.26~11.1), while the density of patients peaked at 45 week (11.2~11.8) respectively. A positive correlation (r=0.69) observed between scrub typhus patients and vectors. This result suggests that this vector surveillance method will be useful for alarm system of tsutsugamushi disease. However, the relationship between scrub typhus cases and chigger mite density will be studied through long-term periodic surveillance.

Ixodidae에 속하는 일부 참진드기들은 중증열성혈소판감소증후군(severe fever with thrombocytopenia syndrome; SFTS)을 비롯한 질병을 매개하는 공중보건학적으로 중요한 해충이다. 우리나라에서는 2013년 이후로 SFTS 환자 발생수가 지속적으로 증가하는 경향을 보이며, 경상북도는 전국적으로 2번째로 많은 SFTS 환자가 발생하는 지역이다. 본 연구에서는 2019년 경북 상주 지역의 진드기 분포를 조사하기 위해 시민의 생활 반경 주변을 도심 녹지지역, 관리 취약지역 및 농촌지역으로 구별하여 flagging 방법을 통해 진드기를 채집하였고, 채집 진드기내 SFTS 바이러스 보균 여부를 조사하였다. 채집된 진드기 수를 Collection Index (CI = tick number / 1h / 2 people)로 산출한 결과, 상주시 내 총 26개 지점에서 작은소피참진드기와 개피참진드기, 일본참진드기를 포함하는 총 CI 143의 진드기가 채집되었고, 그 중 작은소피참진드기가 96.5%(CI 138)로 우점종으로 확인되었다. 채집된 진드기의 약 92%(131 CI)는 인적이 드물고 시청이나 관계 당국의 관리가 이루어지지 않는 관리 취약지역에서 채집되었으나, 도심의 녹지지역와 농촌 지역에서는 8.4%(CI 12)의 진드기만 관찰되었다. 총 CI 143의 진드기를 26개 pooling 한 후 SFTS 바이러스 존재 여부를 조사하였으나, 모두 음성으로 확인되었다. 본 연구의 결과는 지역주민들로 하여금 진드기 매개 질병으로부터 안전한 생활을 하기 위한 권고 자료로 활용할 수 있을 것으로 기대된다.

2012~2017년까지 강원도 3개 시 ‧ 군(춘천시, 강릉시, 횡성군)에서 채집된 모기는 총 6속 13종, 654,362마리가 채집되었다. 채집된 모기는 분류하여 얼룩날개모기속을 제외하고 종별, 채집일, 채집 장소에 따라 최대 50마리를 1개 실험군으로 reverse transcription-polymerase chain reaction, 염기서열 분석방법으로 플라비바이러스 감염여부를 조사하였다. 채집모기 276,224마리에 대해 7,721개 실험군을 검사한 결과 68개 실험군(0.9%)에서 플라비바이러스 유전자가 검출되었다. 검출된 플라비바이러스의 염기서열 분석결과 4개 실험군은 일본뇌염바이러스 (Japanese encephalitis virus), 64개 실험군은 차오양바이러스(Chaoyang virus)로 확인되었다. 일본뇌염바이러스는 2012년 춘천시에서 채집 된 2,728마리의 빨간집모기 중 1개 실험군, 2013년 횡성군에서 채집된 19마리의 동양집모기 중 1개 실험군, 2017년 춘천시에서 채집된 1,111마리의 빨간집모기 중 1개 실험군, 강릉시에서 채집된 빨간집모기 724마리 중 1개 실험군에서 검출되었다. 검출된 일본뇌염바이러스의 유전형은 모두 Ⅴ형 바이러스였다. 차오양바이러스는 강원도 내에서 6년간 채집된 금빛숲모기 232,871마리, 5,055개 실험군을 대상으로 검사한 결과 63 개 실험군에서 검출되었으며, 춘천지역에서 채집된 빨간집모기 585개 실험군 중 1개 실험군에서 검출되었다. 채집지역별 금빛숲모기의 차오양 바이러스 감염률이 가장 높은 지역은 MIR (최소감염률) 0.32, MLE (최대우도법) 0.33 (CI 0.23~0.46) 감염률을 보인 춘천시였다. 그 뒤로 횡성군 MIR 0.30, MLE 0.30 (CI 0.16~0.52)과 강릉시 MIR 0.21, MLE 0.21 (CI 0.13~0.31)순이었다. 월별 금빛숲모기의 차오양바이러스 감염률은 10월에 MIR 0.38, MLE 0.38 (CI 0.07~1.25)로 가장 높은 감염률을 나타내었다.

Aedes albopictus is an invasive mosquito that can be found in all continents. This species, considered as secondary vector of Dengue virus, has recently been suggested to play a role in the transmission of Zika virus in several countries bordering Brazil. In this study, We surveyed the distribution, abundance and main micro habitats of Ae. albopictus in Koera. The main bloodmeal source of this mosquito was mammals (71%) followed by birds (26%), and fish (1%). In flavivius detection, no virus was detected in this mosquito, but a total of six Japanese encephalitis virus (JEV) positive pools were detected from Culex orientalis and Culex pipiens. To investigate the possibility of using Wolbachia, as one of biological control strategy, we investigated the distribution of Wolbachia infection in Ae. albopicutus according to geographical distribution. Over 99% of the collected this mosquitoes harbored Wolbachia.

We monitored the population of Haemaphysalis longicornis, in Andong, Gyungbuk from April to November, 2018. Among total 2,994 ticks collected for 8 months, H. longicornis 1,677(56%), H. spp Larva 1,074(35.9%), H. flava 213(7.1%), Ixodes nipponensis 30(1.0%) were identified. In addition, considering the environment, 1,727(57.7%), 907(30.3%), 192(6.4%) and 168(5.6%) ticks were collected in the grassland, graves, copse, mountain path, respectively. In the pathogen diagnosis with PCR using SFTS virus specific primers, positive viruses were detected in H. longicornis, H. flava and H. spp from June to October. The minimum field infection rate of June, July, August, September and October were 0.4%, 0.8%, 1.2%, 0.8% and 2.3%. respectively.

Surveillance of the vectors were conducted at a total of 7 locations from March to November, 2018 in Gyeongnam province. In the surveillance, a total of 13 species belonging to seven genera were collected in a total of 15,935 females and 126.5/trap/night (TI; Trap Index) in 2018. Among the collection sites, a bird refuge in Busan, Eulsukdo recorded the highest TI 230.4 (Species Ratio; SR 60.1%) for Cx. tritaeniorhynchus females in 2018. A Cx. tritaeniorhynchus female collected firstly for 2018 in the nation at the pigsty of Busan at 1st April. In the results of isolation of viral RNA from 12 mosquito species including Cx. tritaeniorhynchus, Cx. pipiens, Ae. vexans, Ae. albopictus, and Oc. togoi. Chaoyang virus was positive at a pool of Ar. subalbatus collected at a bird refuge but negative in the other 543 pools (14,295 individuals) in 2018.

3년간(2016-2018년) 청주지역에서 채집된 모기의 발생분포를 채집지 3곳(주거지와 철새도래지, 축사)에서 2종의 트랩(BL트랩과 BG트 랩)을 이용하여 비교 조사하였다. 주거지에서 가장 많이 채집된 모기 종은 빨간집모기였으며, 철새도래지와 축사에서는 금빛숲모기가 가장 많이 채집되었다. 철새도래지와 주거지에서는 BG트랩이 BL트랩보다 모기가 더 많이 채집되었으나 축사에서는 BL트랩에서 더 많은 모기가 채집되 었다. 빨간집모기와 흰줄숲모기, 큰검정들모기는 BG트랩에서 많이 채집되었고 금빛숲모기, 얼룩날개모기류, 동양집모기는 비교적 BL트랩을 선호하는 것으로 조사되었다. 채집된 모기를 분류 ․ 동정한 결과 2016년에는 10종 22,679개체가 채집되었고, 2017년에는 8종 6,502개체가 채집 되어 2016년보다 3.49배 감소하였다. 2018년에는 6,803개체가 채집되어 2016년보다 3.33배 감소하였다. 이러한 결과가 강수량과 관련이 있을 것으로 보이며 기상조건과 여러 변인들(채집지역과 모기종류, 트랩종류)에 의한 모기밀도와의 관련성을 비교한 결과 특정 관련성을 확인할 수는 없었다. 채집된 모기의 병원체 감염을 확인한 결과, 2016년도 축사에서 채집한 금빛숲모기 2개 pool, 2018년에 축사에서 채집한 빨간집모기 1개 의 pool에서 차오양바이러스(chaoyang virus)가 검출되어 각각 0.088와 0.147의 최소감염율(MIR)을 보였다. 2017년에는 바이러스가 검출되 지 않았다.

We investigated population densities of mosquitoes in Gyeongbuk region from March to November, 2017 and pathogens were detected from the mosquitoes. Mosquito populations were investigated at 3 sites in downtown and 1 site in cowshed in Andong, 3 sites in Yeongdeok downtown and 3 sites near migratory birds habitat in Sangju by collecting trap. Total collected female mosquitoes were 7 genus, 13 species, 9,892 individuals and relatively dominant ratios are Aedes vexans (40%), Ae. albopictus (20%), Culex pipiens (16%). Flavivirus were monitored in 9,125 collected mosquitoes by real-time PCR and no target flavivirus causing infectious diseases were detected in Gyeongbuk area in 2017.

Heamaphysalis longicornis is a major vector for Severe Fever with Thrombocytopenia Syndrome (SFTS) virus and the density of the vector has been increasing because of the climate change. The incidence of fatalities due to SFTS is increasing every year. In this study, to evaluate the SFTS transmission by ticks, the density of ticks mediating SFTS was monitored. Tick was collected every month from four different sites (Grass land, Mountain path, Grave, Copse) in Andong with the traps containing dry ice as CO2 attractants. Among 2,572 ticks of 3 species; H. longicornis, H. flava, and Ixodes nipponensis were most abundantly collected from April to August. H. longicornis is the richest species (92.8%), whereas Ixodes nipponensis was the least species (0.8%). The 54.5% of the sample were nymph stage and female/male ratio was 64.3%. According to the pathogene analysis, SFTS virus was detected from H. longicornis adult and larvae stages collected in July and August. In July samples, SFTS virus was detected only from grassland site, but the virus was observed in the sample from all four sites in August. For effective prevention of SFTS, the tick density should be continuously monitored based on the onset time of SFTS with the consideration of habitate, habit & life history of ticks.

West Nile Virus (WNV) is transmitted by infected mosquitoes. Vector mosquitoes usually acquire these pathogens fromfeeding on an infected host, and transmit the pathogens to a naive host during feeding events. To understand the virustransmission dynamics and to survey WNV throughout country, the present study has been conducted. We collected mosquitoesat urban parks in Seongnam, Wonju, Gunsan, Daegu, and Tongyeong using CDC light trap with Dry ice from April toSeptemper in 2017 (mosquito collecting is on going). Among collected mosquitoes, blood-fed mosquitoes were conductedblood meal identification assay and the other mosquitoes were subjected to virus detection using real-time PCR method.A total of 2,290 mosquitoes representing 6 genera and 15 species were collected. The most dominant species was Culexpipiens complex (42.1%) followed by Aedes albopictus (15.1%), Ae. vexans nipponii (14.6%), Ochlerotatus koreicus (9.8%),Cx. orientalis (6.5%), and Armigeres subalbatus (4.4%). The blood meal source were of mammal (93.3%), and birds (6.7%).So far, no WNV has been detected in any mosquitoes.

The members of the genus Flavivirus are noteworthy, as they cause infectious diseases in humans, such as Zika, denguefever, yellow fever, West Nile, and Japanese encephalitis. Due to the increased awareness of the public health risk posedby flavivirus-infected mosquitoes, mosquito collections were performed in six urban parks of South Korea, as the parksare designated for human recreation but also provide suitable habitats for mosquitoes. We examined the diversity andabundance of mosquito species and conducted molecular diagnostics for the detection of flavivirus infections. Monthlycollections were carried out in each park from March to August in 2017. A total of 4,851 mosquitoes (5 genera and13 species) were collected using BG-sentinel traps and then investigated for flavivirus infections. Pathogenic flavivirusinfections causing human diseases were not observed in the field-collected mosquitoes. However, insect-specific flavivirus(ISF) infections were detected in several mosquito pools. ISF has been previously known to enhance or suppress the replicationof medically important flaviviruses in co-infected mosquito cells. In this study, partial sequences of ISF were analyzed.However, further studies are needed in order to determine its genetic characterization and biological function in vivo.

Aedes albopictus is one species of mosquito transmitting flavivirus causing Dengue, Zika, and West Nile fever. Although it is an important disease vector, the genetic study of Ae. alpopictus populations has not been undertaken yet in South Korea. Here, we investigated the genetic variation of 99 Ae. albopictus individuals collected from 29 sites in nine provinces in 2016, through mitochondrial COI gene analysis. Haplotype analyses revealed seven haplogroups in South Korea. The main haplogroup, comprising 76 individuals (77.8%), was genetically identical to the one from Nagasaki. Two groups from Jeju Island (11) and the southern coast of South Korea (nine) were closely related to different Ae. albopictus strains from Kumamoto and Guangdong/Fujian, respectively. However, the others (four) were distinct from these two countries. No geographic divisions of populations were found in the study regions. The results suggest the possibility that the currently prevalent Ae. albopictus in South Korea, represents a part of the descendants that originated from nearby countries. However, more comprehensive investigations are needed to explain its movement routes.