The purpose of this monitoring is to survey the geographical distribution of tick species using dry ice bait traps and flagging methods at each ten provinces (GangwonⅠ,GangwonⅡ, Gyeonggi, Chungbuk, Chungnam, Gyeongbuk, Gyeongnam, Jeonbuk, Jeonnam and Jeju area) and one Metropolitan area in the Republic of Korea for eight months from April through November, 2016. A total of 65,339 ixodid ticks (8,200 females, 1,988 males, 31,453 nymphs and 23,698 larvae) was collected, belonging to three genera (Haemaphysalis, Ixodes and Amblyomma). Haemaphysalis longicornis was the most commonly collected species, which is represented for 96.88% of all the collected ticks and followed by H. flava (2.69%), I. nipponensis (0.35%), A. testudinarium (0.05%) and H. japonica (0.03%) in the Republic of Korea for the study period. Haemaphysalis longicornis was a dominant species observed in these eleven areas.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne zoonosis and SFTS virus is transmitted to humans by tick bites. The aim of this study was to monitor tick population and its SFTS virus infection. During March 2014 to October 2015, ticks were monthly sampled using dry-ice bait trap and flag method from 4 collecting points in Boeun-gun. A total of 16,500 ticks, including 14,646 Haemaphysalis longicornis (88.7%), 1,825 H. flava (11.1%), and 29 Ixodes nipponensis (0.2%), were collected. Ticks were pooled (5,156 ticks in 456 pools) and tested by RT-PCR and nested PCR and the minimum infection rate of ticks was 0.27% (14 pools) consisting of 0.13% H. longicornis (6 pools), 1.19% H. flava (8 pools). This annual surveillance study will be needed for long-term monitoring of ixodid ticks in Korea.

The geographical distribution of ixodid ticks in were surveyed at 10 areas from April to November 2015. We investigated tick distribution using dry ice bait trap and flagging method as a part of disease vector monitoring in Korea. As a result, ticks collected 29,992 ixodid ticks with 3 genera, 7 species. Among them, Genus Haemaphysalis, Ixodes and Amblyomma accounted for 29,751 (99.2%), 223 (0.7%) and 18 (0.1%). Haemaphysalis longicornis was accounted for 88.9%, which has become the dominant species. Some species, such as H. japonica and Ixodes persulcatus were only collected Gangwon area. Metropolitan area had the highest population of ticks 6,540 (21.8%), Chungbuk area was next 5,049 (16.8%). In environmental distribution, Genus Haemaphysalis was highly collected in grassland site (32.1%) and Genus Ixodes was highly collected in coniferous forest site (43.5%). Upon analysis of the monthly distribution, H. longicornis, the dominant species, was highly collected at nymph stage in May, and its larva was highly collected in September. These studies may provide important information for control and management of tick in Korea.

A surveillance of chigger mites was performed to monitor the incidence of scrub typhus vectors at 5 environmental collection points of 3 locations (Muju, Namwon and Gimge) from April 2016 in Jeollabuk-Do, Korea. During the surveillance period, 3,292 chigger mites were collected and the predominant species were Leptotrombidium pallidum (42.9%). The high environmental collecting rates were recorded at reservoir bank (31.6%) and grassfield (29.7%). We detected Orientia tsutsugamushi from the samples collected in Jeollabuk-Do using nested polymerase chain reaction. The specific DNA of O. tsutsugamushi were detected in 11 pools among total 119 pools and its minimum positive rate was 0.35%. In order to clarify the relationship between chigger mites and scrub typhus cases, further survey will be needed.

Ixodid ticks are notorious as the vector of severe fever with thrombocytopenia syndrome virus (SFTSV) in Korea. To confirm the transovarial transmission of SFTSV, we collected blood-fed adult ticks from animals in SFTS case reported area of Jeju island in 2015. A total of 476 ticks were collected from four host animal species, horse (81.3%), dog (9.0%), roe deer (7.1%) and wild boar (2.5%). They were identified as 1 genus and 2 species, Haemaphysalis longicornis (87.8%) and H. flava (12.2%). Among them, 131 adults hatched their eggs successfully. The body weight of females was highly correlated with the number of egg masses laid (P < 0.05). We confirmed that one adult H. flava was infected with SFTSV and its infection rate was 0.77%. The eggs of the SFTSV-infected adults also were infected with SFTSV and its transovarial transmission was confirmed. This result suggests that the parent generation of H. flava could transmit SFTSV transovarially into their F1 progeny and H. flava might be one of major vectors of SFTSV in Korea.

We investigated the distribution of ixodid ticks in severe fever with thrombocytopenia syndrome (SFTS) case reported areas using flagging method from May to November 2014 in Korea. We collected 13,471 ixodid ticks with 2 genera and 3 species. Among them, Genus Haemaphysalis and Ixodes accounted for 99.9% (13,455) and 0.1% (16), respectively. Genus Haemaphysalis consisted of 2 species, H. longicornis (96.2%) and H. flava (3.7%). I. nipponensis was only collected in Genus Ixodes. H. longicornis was the dominant species (over 90%) in most study areas. Ixodid ticks were evenly distributed at various environmental sites, such as residences, hills, grassfields, fields, graves, copses, other sites. The further study on SFTSV infection in ixodid ticks will be needed.

A surveillance of chigger mites was performed to monitor the incidence of scrub typhus vectors at 4 environmental collection points of 6 locations from September to November 2014 in Korea. During the survey period, 420 chigger mites were collected and the dominant species was Leptotrombidium scutellare (42.6%). The first appearance of chigger mite was at 37th week (9.3.-9.10.) and the collected numbers of chigger mites was the highest at 43rd week (10.17.-10.23.). In Goryeong-gun, 299 chigger mites were collected, whereas 5 chigger mites were collected In Yesan-gun. The high environmental collecting rates were recorded at rice field (56%) and waterway (20%). The annually collected numbers (2012-2014) of chigger mites were compared with the average temperatures in August. This result suggests that the average temperature in August might be related with the annual incidence of scrub typhus vectors in Korea. However, the relationship between climate factors and the density of chigger mites needs to be studied by long-term periodical surveillance.

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.

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.

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.

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 investigated the prevalence of severe fever with thrombocytopenia- syndrome virus (SFTSV) and geographical distribution of ixodid ticks from 25 regions of the Korea during 2011-2012. We collected 25,940 ixodid ticks with 3 genera and 7 species using dry ice bait trap and flagging. Among them, Genus Haemaphysalis, Ixodes and Amblyomma counted 25,821 (99.5%), 118 (0.5%) and 1 (<0.0%). Genus Haemaphysalis consisted of 4 species, H. longicornis (90.4%), H. flava (9.2%), H. formosensis and H. hystricis (<0.1%). Genus Ixodes consisted of 2 species, I. nippoenesis (0.4%) and I. persulcatus (0.1%). Only one Amblyomma testudinarium was collected. The highly infested sites were grassland (50.1%) and mixed stand forest (20.3%). Minimum infection rate (MIR) of SFTSV in H. longicornis was 0.5% in Korea and this rate was similar to that in China (0.46%). Our results showed that H. longicornis is a major vector of SFTSV and its surveillance will be needed at high risk area.