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.

Zika virus (ZIKV) is an ongoing global public health emergency with 74 countries (Sep. 19 2016) and territories reporting evidence of ZIKV transmission since 2015. Total 14 cases of Zika have been reported since January 2016 and all cases have been suspected as infections by mosquito bite on overseas. Vector control strategy of comprehensive national Zika control strategies will be presented on this presentation. To efficiently control Ae. albopictus when Zika inflow into ROK, nine ministers of government held on Zika countermeasure meeting, checked preparatory attitudes and assigned roles of each minster for Zika control. Korea guidelines for Ae. albopictus control were distributed to local governments and related ministers of government and vector control agents in all local government were educated by vector control experts. To block transmission of Zika virus by mosquito bite from overseas travel-associated patients Zika patients in ROK, vector monitoring and control were carried out at surroundings near residences of patients and decreased vector population density.

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.

Vector mosquitoes are related with various diseases on human, such as malaria (Anopheles sinensis (L.), An. sinensis), Japanese encephalitis (Culex tritaeniorhynchus (L.), Cx. tritaeniorhynchus), yellow fever (Aedes albopictus (L.)), dengue hemorrhagic fever (Ae. albopictus) and filariasis (Ae. albopictus), as well as nuisance insect pests (Culex pipiens pallens Foskal, Cx. p. pallens). Continued and repeated use of conventional insecticides such as organophosphorus and carbamates, pyrethroids has often resulted in the widespread development of resistance and has undesirable effects on non-target organisms and environment. Particularly, widespread insecticide resistance has been a major obstacle in the cost-effective integrated vector management program. In theRepublic of Korea (ROK), studies on mass vector mosquito control using insecticides were mainly carried out until 1970’s such as a fuselage-mounted ULV spray system to C-46 aircraft, effectiveness of ground aerosols ULV premiumsumihtion, a helicopter application of ULV Dibrom and residual toxicity of organophosphates in animal shelters for Japanese Encephalitis (JE) and Plasmodium vivax malaria vector mosquito control. Regional insecticide resistance of vector mosquitoes has been annually evaluated since ,early 1980’s, the first detailed study on susceptibility of seven mosquito species to 13 organophosphorus insecticides revealed the DDT and lindane resistance of Cx. tritaeniorhyunchus. Marked annual and regional variations of insecticide resistance have been observed. In comparative resistance, the resistance ratios of various insecticides were compared among each other using two strains of vector mosquitoes that were collected from same locality. An. sinensis from Koyang-si in 1992 and 1981 demonstrated >100 folds and >3000 folds of higher resistance to DDT and to bio-resmethrin. An. sinensis from Paju-si in 2008 demonstrated 30 folds of higher susceptibility to fenthion than those collected in seven years ago. Cx. tritaeniorhynchus from Gwanju in 2010 and in 1992 showed >100 folds of higher resistance to pyrethroids. In comparative regional resistance monitoring, Cx. p. pallens from six localities in the ROK in 2008 and six geospatially-distant field Cx. tritaeniorhynchus strains in 2011 showed marked regional resistance variations. Field populations of Cx. tritaeniorhynchus from agricultural areas demonstrated extremely higher insecticide resistance to pyrethroids than those from non-agricultural areas. Cx. tritaeniorhynchus populations from rice paddies had been under heavy selection pressure due to pyrethroids, which were used for a long time to control agricultural pests in the localities. These results indicate that careful selection and rotational use of these insecticides may results in continued satisfactory control against field populations of vector mosquitoes

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.

Density of malaria vector mosquitoes, Anopheles mosquitoes, and infection of Plamodium vivax from the vector mosquitoes were monitored at 9 surveillance points in Incheonsi, 12 in Gyeonggi province and 7 in Gangwon province in the Republic of Korea (ROK) from April to October of 2010. The seasonal numbers of Anopheles mosquitoes collected weekly showed a high degree of variability. A total of 4,435 mosquitoes were captured using black light traps. Members of the Anopheles mosquito group were the most abundant species and accounted for 71.8% of the mosquitoes collected. The majority of this species were collected from Incheonsi (86.2%), particularly from Ganghwagun (84.8%). During June, populations of this species steadily increased and peak at second week of July. Thereafter, populations of this species decreased by the second week of August and increased by the third week of August, again. Anopheles mosquitoes steadily decreased from the fourth week of August. First Anopheles mosquitoes were reported in Wolgotri (15th weeks/year), Ganghwagun, Incheonsi, followed by Tanhyundong (16th weeks/year), Pajusi, Gyeonggi Province and Daemari (17th weeks/year), Cheolwongun, Gangwon Province. In Ganghwagun in which the most abundant malaria patients (102 patients) were reported, Anopheles mosquitoes demonstrated the highest species portion (over 70%) among collected mosquito species from July to September. Infection rate of P. vivax from the Anopheles mosquitoes also was the highest in Ganghwagun. In Gangwon and Gyeonggi provinces, collection rate of Anopheles mosquitoes and infection rate of P. vivax were relatively lower than those of Ganghwagun. Reported malaria patient cases in Gangwon and Gyeonggi provinces also were relatively lower than those of Ganghwagun. However, detailed results showed that there were some sites in which any correlation between malaria patients and vector mosquitoes were not. This may be resulted from size of surveillance area. Smaller size of surveillance area was, higher accuracy of analysis on correlation between vector mosquitoes and patients was. Further studies on relationship between malaria vector and patients may need for more accurate analysis, such as increase of collection site and so on.

This study was carried out to investigate the inhabitation features of cockroaches in Jejusi, Korea. For sampling, fourteen sites were selected from every two sites of seven different habitat categories, including dwelling house, Korean restaurant, Japanese restaurant, Chinese restaurant, tea-room, hotel-inn and hospital. The cockroaches were weekly captured using sticky-traps from March, 2005 to February, 2006. Studies were focused on the temporal fluctuations of the total sample and two developmental stages (nymph and adult), the sex ratio, the positive trap percentage, and the comparative population sizes of the habitats. The positive trap percentage was 16.64%. Three species, Blatella germanica, Periplaneta americana, and Periplaneta fuliginosa, were confirmed to inhabit in Jejusi. The predominant species was P. fuliginosa (89.16%). Meanwhile, P. americana and B. germanica were shown to be much lower population size (6.44 and 4.40%, respectively). The mean sex ratio was 0.75% (males/females): B. germanica, 0.62%, P. americana, 0.29% and P. fuliginosa, 0.87%. The nymphs (82.19%) surpassed the adults (17.81%) in the individual number. Periplaneta fuliginosa also exceeded much more the other two species (P. americana and B. germanica, 5.37% and 1.67%, respectively) in the nymph number/the collected cockroaches. Both curves of the nymph and adult in the seasonal population change of P. fuliginosa made the peaks at September. This result suggested that the life cycle of this species is univoltine. The positive trap percentage and population size in the Japanese restaurant where was shown to be the most heavily polluted habitats by cockroaches were 20.67% and 0.79 (individuals/trap/week), respectively. Also, Chinese restaurant and dwelling house where were shown to be comparatively high polluted were 31.67% and 23.75% in positive trap percentage and 0.76 and 0.40 in population size, respectively. In contrast, hotel-inn, tea-room, hospital and korean restaurant were shown to be quite or very low numbers as 16.50%, 16.00%, 6.20%, and 6.00% in positive trap percentage, and 0.37, 0.18, 0.10, 0.06 in population size, respectively. It was concluded that there were differences in the species composition and the actual living conditions of the cockroach between Jejusi and other cities of Korea.