[Show abstract][Hide abstract] ABSTRACT: We investigated the infection rate for severe fever with thrombocytopenia syndrome virus (SFTSV) among ticks collected from humans during May-October 2013 in South Korea. Haemaphysalis longicornis ticks have been considered the SFTSV vector. However, we detected the virus in H. longicornis, Amblyomma testudinarium, and Ixodes nipponensis ticks, indicating additional potential SFTSV vectors.
[Show abstract][Hide abstract] ABSTRACT: A total of 9,281 larval chigger mites were collected from small mammals captured at Hwaseong-gun, Gyeonggi-do (Province) (2,754 mites from 30 small mammals), Asan city, Chungcheongnam-do (3,358 mites from 48 mammals), and Jangseong-gun, Jeollanam-do (3,169 for 62 mammals) from April-November 2009 in the Republic of Korea (= Korea) and were identified to species. Leptotrombidium pallidum was the predominant species in Hwaseong (95.8%) and Asan (61.2%), while Leptotrombidium scutellare was the predominant species collected from Jangseong (80.1%). Overall, larval chigger mite indices decreased from April (27.3) to June (4.9), then increased in September (95.2) and to a high level in November (169.3). These data suggest that L. pallidum and L. scutellare are the primary vectors of scrub typhus throughout their range in Korea. While other species of larval chigger mites were also collected with some implications in the transmission of Orientia tsutsugamushi, they only accounted for 11.2% of all larval chigger mites collected from small mammals.
The Korean Journal of Parasitology 04/2014; 52(2):225-9. · 0.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Transovarial transmission of Orientia tsutsugamushi in colonies of Leptotrombidium palpale was studied in the parent and F1 and F2 generations. Both transovarial transmission and filial infection rates were 100% in the parent and F1 generations of Leptotrombidium palpale. The filial infection rate in the F1 generation was 100%, but it declined to 94.3% in the F2 progeny. The sex ratio of the F1 generation from infected L. palpale was 1∶0.8 (male:female) and the proportion of males was relatively high. This study is the first to report on the transovarial transmission of O. tsutsugamushi in L. palpale. High transovarial transmission rates in L. palpale suggest that this species might be one of the major vectors of tsutsugamushi disease in Korea.
PLoS ONE 01/2014; 9(4):e88453. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Haemaphysalis longicornis a vector that harbors severe fever with thrombocytopenia syndrome virus (SFTSV), is a major species of tick in South Korea. To investigate the existence and prevalence of SFTSV in Korea, we collected ticks from nine provinces in South Korea for detecting SFTSV. In all, 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 0.46% (55 pools). SFTSV was detected in ticks during all the developmental stages, showing MIR in larvae (2/350, 0.57%), nymphs (38/10,436, 0.36%), males (2/221, 0.90%), and females (13/849, 1.53%), respectively. Viruses were detected in ticks collected between April and September. A higher MIR was detected in ticks from the southern part of the country. We amplified the M and S segment partial genes from a sample and analyzed the nucleotide sequence. The results showed a 93 to 98% homology to Chinese and Japanese strains registered in Genbank.
In this study, we confirmed the existence of SFTSV for the first time in South Korea. The SFTSV prevalence data from the studies are essential for raising the awareness of SFTS in South Korea.
Ticks and Tick-borne Diseases 01/2014; · 2.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Overwintering mosquitoes in a grassy field were surveyed at 13 different localities from December 2007 to February 2008 in the Republic of Korea (ROK). Mosquitoes were collected by putting a white colored tent on the grass, without the base, and heating the inside of the tent. A total of 784 female adults comprising seven species were collected during the study period, including 395 (45.6%) Anopheles pullus, 338 (43.2%) An. sinensis, 21 (2.7%) An. belenrae, 2 (0.3%) An. kleini, 43 (5.5%) Culex tritaeniorhynchus, 20 (2.5%) Cx. inatomii, and 1 (0.3%) Cx. pipiens complex. The mosquitoes showed different overwintering distributions by temperature zone and locality. Predominant species, the malaria vectors An. pullus and An. sinensis, showed different overwintering distributions. Anopheles pullus had a 90.9% collection rate except for Youngju and an average – 0.6°C temperature between December and February. Anopheles pullus showed >50% collection rate in most regions maintained below an average of −1.4°C, and the rate of An. sinensis showed more than 50% collection rate in all regions maintained at an average above −1.1°C. Other species showed regional characteristics; An. belenrae was distributed in the northwest part of the ROK, and An. kleini was collected rarely at one locality in the middle part of ROK. Culex tritaeniorhynchus, a Japanese encephalitis virus vector, was distributed in the southern and costal region and maintained at an above average of −1.0°C. Culex inatomii was collected on the coastal region of the ROK.
[Show abstract][Hide abstract] ABSTRACT: Apoptosis has been shown to be induced and down-regulated by the Hantaan virus (HTNV) nucleocapsid (N) protein. To address these conflicting data, the expression of the p53 protein, one of the key molecules involved in apoptosis, was assessed in the presence of the N protein in A548 and Hela cells. The amount of p53, increased by drug treatment, was reduced when cells were infected with HTNV or transfected with expression vector of HTNV N protein. When cells treated with a proteasome inhibitor (MG132) or an MDM2 antagonist (Nutlin-3), p53 expression was not reduced in N protein-overexpressed cells. We concluded that the HTNV N protein ubiquitinates and degrades p53 MDM2-dependently. Here we report down-regulation of p53 expression through a posttranslational mechanism, MDM2-dependent ubiquitination and degradation, by HTNV N protein. These results indicate that N protein-dependent p53 degradation through ubiquitin proteasome system is one of anti-apoptotic mechanisms by HTNV.
Journal of General Virology 09/2013; · 3.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chikungunya (CHIK) has been classified as a communicable disease group IV in South Korea since late 2010. Based on this, we investigated the extent of imported cases of CHIK in dengue-suspected individuals returning from dengue-endemic regions.
A total of 486 dengue-suspected serum samples were screened for CHIK by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Further RT-PCR-positive samples were used for the viral culture, and CHIK was subsequently confirmed by sequence analysis of the culture samples.
Five out of 107 dengue-positive samples were found to be positive for CHIK and 15 out of 379 dengue-negative samples were found to be positive for CHIK by immunoglobulin M ELISA. Further, a CHIK virus was isolated from one of the two RT-PCR-positive sera by cell culture and confirmed by sequence analysis.
The present study documents the first evidence of travel-associated CHIK infection in South Korea. Considering the intense international traffic between countries, our finding emphasizes the urgent need for active patient and vector surveillance for timely response to reduce the introduction of CHIK in Korea.
Osong public health and research perspectives. 06/2013; 4(3):170-175.
[Show abstract][Hide abstract] ABSTRACT: Abstract The toxicities of 10 insecticides were examined against late third instar Culex tritaeniorhynchus Giles (Diptera: Culicidae) using the direct-contact mortality bioassay. Six geospatially-distant field mosquitoes were collected from Chuncheon-si, Hwaseong, Seosan. Jeonju, Daegu, and Busan in the Republic of Korea. Marked regional variations of insecticide susceptibility were observed. Field populations of Seosan, Jeonju, and Daegu from agricultural areas showed higher to extremely higher insecticide susceptibility to pyrethroids than those of Chuncheon-si, Hwaseong, and Busan strains from non-agricultural areas. Extremely high to low levels of susceptibility were measured: bifenthrin, susceptible ratio (SR) = 2.7-896.3; β-cyfluthrin, SR = 1.8-633.3; α-cypermethrin, SR = 1.2-1,051.9; deltamethrin, SR = 1.3-711.1; permethrin, SR = 1.5-1,053.4; etofenprox, SR = 2.2-29.3; chlorfenapyr, SR = 5.1-103.6; chlorpyrifos, SR = 2.3- 337.0; fenitrothion, SR = 2.0-142.3; and fenthion, SR = 1.4-186.2. Cx. tritaeniorhynchus populations from rice paddies had been under heavy selection pressure due to the agricultural insecticides, and that's why the mosquito species demonstrated high resistance 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 result in continued satisfactory control against field populations of Japanese encephalitis vector mosquitoes.
Journal of Insect Science 01/2013; 13:2. · 0.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, we demonstrated that TBEV-infected ticks have been distributed in the ROK, combined with our previous results. These results suggest that TBEV may exist in the ROK, and H. longicornis, H. flava, and I. nipponensis may be potential vectors of TBEV. In addition, these results emphasize the need for further epidemiological research of TBEV.
We examined for the presence of RNA of TBEV by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR) using ixodid ticks captured in 25 localities of 10 provinces. Ticks were collected by the flagging and dragging method or using sentinel BG traps at forests, grass thickets, and grassland. A total of 13,053 ticks belonging to two genera and four species were collected and pooled (1292 pools), according to collection site, species of tick, and developmental stage.
Among 1292 pools, the envelope (E) protein gene of TBEV was detected using RT-nested PCR in 10 pools (3 pools of the 1,331 adult ticks and 7 pools of the 11,169 nymph ticks) collected from Gangwon-do province, Jeonrabuk-do province, and Jeju Island. The minimum infection rates for TBEV of Haemaphysalis longicornis, Haemaphysalis flava, and Ixodes nipponensis were 0.06%, 0.17%, and 2.38%, respectively. Phylogenetic analysis based on the partial E protein gene was performed to identify relationships between the TBEV strains. This showed that 10 Korean strains clustered with the Western subtype.
In this study, we investigated the prevalence of tick-borne encephalitis virus (TBEV) in ixodid ticks from various regions of the Republic of Korea (ROK) during 2011-2012 to identify whether TBEV is circulating and to determine the endemic regions of TBEV.
Osong public health and research perspectives. 12/2012; 3(4):213-21.
[Show abstract][Hide abstract] ABSTRACT: We assessed the toxicity of 17 steam distillate constituents of Cyperus rotundus (L.) rhizome, another seven known compounds of C. rotundus rhizome, and 14 structurally related compounds to females from an insecticide-susceptible KSS strain and two field-collected SEL and DJN colonies of Blattella germanica (L.). High contact + fumigant toxicity to KSS females was produced by p-cymene, nerol, linalool, o-cymene, (S)-(-)-citronellal, (1S)-(-)-camphor, terpinolene, and m-cymene (LD50, 0.29-0.47 mg/cm2). The toxicity of these compounds was virtually identical against females from any of the three strains, even though SEL and DJN females were resistant to six acetylcholinesterase inhibitors and three pyrethroids (resistance ratio, 9-154 and 12-195). These results indicate that the compounds and insecticides do not share a common mode of action or elicit cross-resistance. The test compounds were effective in closed but not in open containers against SEL females, indicating that their route of insecticidal action was largely a result of vapor action. Structure-activity relationship indicates that structural characteristics, such as types of functional groups, appear to play a role in determining the terpenoid toxicities to B. germanica. C. rotundus rhizome steam distillate constituents and related compounds described merit further study as potential fumigants for the control of resistant cockroach populations in light of global efforts to reduce the level of highly toxic synthetic insecticides in indoor environments.
Journal of Medical Entomology 05/2012; 49(3):631-9. · 1.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Toxicities of 10 insecticides were examined against late third instars of Culex pipiens pallens, the northern house mosquito, using a direct-contact mortality bioassay. Several strains of mosquitoes were tested (insecticide-susceptible KS-CP strain and five geospatially distant field-collected strains (DG-CP, US-CP, BS-CP, GS-CP, and SG-CP)) and identified by polymerase chain reaction. Marked regional variations of insecticide susceptibility were observed. Extremely high to low levels of resistance were measured: bifenthrin, resistance ratio (RR) = 1–521; β-cyfluthrin, RR = 16–397; α-cypermethrin, RR = 9–343; deltamethrin, RR = 1–40; etofenprox, RR = 2–42; permethrin, RR = 3–46; chlorpyrifos, RR = 2–675; fenitrothion, RR = 0.5–364; and fenthion, RR = 2–360. All strains were susceptible to one or more of the insecticides examined. These results indicate that careful selection and rotational use of these insecticides may result in continued satisfactory control against field populations of northern house mosquitoes.
Journal of Asia-Pacific Entomology 03/2012; · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The susceptibility of Culex tritaeniorhynchus collected from Gwangju, Jeollabuk Province, Republic of Korea (ROK) to insecticides was evaluated under laboratory conditions using ten insecticides (7 pyrethroids and 3 organophosphates) that are currently applied by local public health centers in the ROK. Based on the values of median lethal concentration (LC 50), Cx. tritaeniorhynchus larvae were most susceptible to chlorpyrifos (0.006 ppm), fenitrothion (0.022 ppm), fenthion (0.035 ppm) and bifenthrin (0.038 ppm), and were least susceptible to esbiol (1.722 ppm). In comparative resistance tests, the resistance ratios (RRs) of seven insecticides were compared among each other using two strains of Cx. tritaenio-rhynchus that were collected from the same locality during 1992 and 2010. Culex tritaeniorhynchus demonstrated significantly increased RRs to pyrethroids over time, while demonstrating decreased RRs among the organophosphates. Among the pyrethroids, permethrin had the highest RR values of 182.1-and 833.3-fold differences, followed by etofenprox with RRs of 138.4-and 224.1-fold differences in values of LC 50 and concentration that produced 90% mortality (LC90), respec-tively. Culex tritaeniorhynchus strains demonstrated the least amount of change in susceptibility to the organophosphates, chlorpyrifos, fenitrothion and fenthion with 0.020-, 0.019-and 0.001-fold differences in resistance ratios (RRLC 50), respectively.
[Show abstract][Hide abstract] ABSTRACT: Most of the epidemic spread is closely related to the growth environment of insects or rodents as mediators. Climate changes make their growth environment change resulting in an epidemic infection increase. Even though the incidence of scrub typhus is increasing, little is known about scrub typhus compared with other infectious diseases in Korea. The tsutsugamushi infection prevalence of Orientia tsutsugamushi carried by tick was projected for surveillance from April to September in 2011. Chigger mites were collected at Miryang (Mt. Gaji) and Hapcheon (Gaya-myeon) by the Sherman live trap and hanging method. Each collected samples were identified by microscope. Genomic DNAs were purified using CTB extraction kit and amplified by PCR using INNOPLEX TSUTSU detection kit.The number of chigger mites was highest in April, and then gradually declined. No chigger mites were collected in July (1st week) and August (1st week). However, chigger mites were collected again after September. We detected Orientia tsutsugamushi from samples collected in May (2nd week) using INNOPLEX TSUTSU detection kit. There has been no sign of an epidemic disease caused by climate change with the exception of tsutsugamushi infection in Korea until now. But, it is gradually requiring continuous monitoring, and the development of protective technology and emergency system for rapid, accurate diagnosis and treatment.
[Show abstract][Hide abstract] ABSTRACT: 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 LD 50 values of 69.7, 78.8 and 81.9 μg/♀, and adults had LD 50 values of 71.9, 78.8 and 85.4 μg/♀, 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 1438 folds higher for organophosphates (LD 50 values of 0.05 to 0.23 μg/♀) and 62 to 1155 folds higher for pyrethroids (LD 50 values of 0.13 to 2.41 μg/♀). The SRs of Culex pipiens to E. orientalis were 606 to 3595 folds higher for organophosphates with LD 50 values of 0.02–0.17 μg/♀ and 81 to 1365 folds higher for pyrethroids with LD 50 values of 0.11–1.83 μg/♀. 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.
Journal of Asia-Pacific Entomology 10/2011; · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To identify potential vector species of scrub typhus in the Republic of Korea (ROK), chigger mites were harvested from wild rodents captured at nine localities in October 2005. The bodies of the chigger mites were individually punctured with a fine pin, squeezed out internal contents, and examined for Orientia tsutsugamushi DNA by nested polymerase chain reaction. The exoskeleton of associated chiggers was mounted on glass slides with polyvinylalcohol (PVA) medium for identification. Among 830 individuals belonging to 4 genera and 14 species, O. tsutsugamushi was detected from 22 chiggers of six species, with an overall infection rate of 2.7%. The infection rate was highest for Leptotrombidium palpale (5.3%), followed by Neotrombicula japonica (4.3%), Leptotrombidium scutellare (3.7%), Leptotrombidium orientale (3.6%), Eushoengastia koreaensis (1.9%), and Leptotrombidium pallidum (1.5%). This study first reported O. tsutsugamushi infection from N. japonica and E. koreaensis larvae in the ROK. The population densities of L. pallidum (33.4 chiggers/rodent), historically confirmed as a primary vector of scrub typhus in the ROK, were high, whereas its infection rate was relatively low (1.5%). However, E. koreaensis was only collected from 154 individuals at seven collection sites and its infection rate was demonstrated relatively high (mean 1.9%). Additional studies are needed to determine the role of vector species in the epidemiology of scrub typhus.
[Show abstract][Hide abstract] ABSTRACT: Culex pipiens molestus Forskal has been reported as a dominant species in underground structures of urban areas in the Republic of Korea (ROK) during all seasons and becomes bothersome to humans in late autumn and winter. Most Cx. pipiens molestus in septic tanks are controlled in the ROK using larvicides such as Bt and IGR. However, there are a number of problems associated with larvicides, such as high cost and requirement for frequent use. In the present work, a new control method for Cx. pipiens molestus in septic tanks by using mixtures of sucrose solution with insecticides was investigated.
The insecticidal and repellent activities of ten insecticides were evaluated for best control of Cx. pipiens molestus in septic tanks. Firstly, differences in susceptibilities to insecticides were evaluated in topical assays by forced direct contact bioassay and in a screened wire cage by free direct contact bioassay. The difference in insecticide susceptibility in the mosquitoes was the result of repellency by the insecticides. In three septic tanks, the density of Culex mosquitoes was sharply reduced by a deltamethrin-sucrose solution kit.
The results demonstrated the potential for mosquito control by deltamethrin-sucrose solution, and the study offers basic information related to mosquito control in septic tanks.
Pest Management Science 02/2011; 67(6):665-71. · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A surveillance of trombiculid mites was conducted by collecting wild small mammals twice a year (spring and autumn seasons) at 24 localities in Korea from 2005 to 2007 to clarify the nationwide distribution of scrub typhus vectors. Among 783 trapped rodents, Apodemus agrarius accounted for 87.4% and the trapping rate at riverside was recorded the highest. A total of 67,325 mites representing 4 genera and 14 species were collected and their chigger index (C. I.) was 86.0. The predominant species were Leptotrombidium pallidum (52.6%), L. scutellare (27.1%), L. palpale (8.2%), L. orientale (5.6%), and Neotrombicula tamiyai (1.7%). However, the portion of L. scutellare in southern area including endemic provinces such as Jeollabuk‐Do (34.3%), Jeollanam‐Do (49.0%), and Gyeongsangnam‐Do (88%) were relatively higher than middle areas where L. pallidum was predominant in. Additionally, in autumn season, the density of L. scutellare was increased up to 42.0% while that of L. pallidum was decrease to 37.6%. Now we are performing a periodic surveillance again (2011∼2013) and trying to develop a method to identify these trombiculid mites using molecular markers.
[Show abstract][Hide abstract] ABSTRACT: To prevent the influx, propagation and spread of epidemic vectors (vector borne disease) that are increasing due to global warming and climate change, we kept the mosquito vectors under constant surveillance from April (2nd week) to September (3rd week), 2011 in Yeongnam area. Samples were collected at Youngdo (Busan) for Dengue fever and Yellow fever and by support of Gimcheon, Gyeongju, Ulju(Ulsan), Jinju, Hapcheon public health center for Japanese encephalitis and malaria, and also at two sites in Eulsook‐do for Westnile.A BG‐sentinel trap was used to collect samples for Dengue fever and Yellow fever, whereas black light traps were used for Westnile and Japanese encephalitis. At first, mosquito vectors were classified according to a standard classification method and then identified as to whether or not each of the collected samples had the pathogens by using the Real‐time PCR method.Two species of mosquito vectors, Culex pipiens pallens and Ochlerotatus togoi were mostly collected by BG‐sentinel traps. On the other hand, Aedes vexans nipponii and Anopheles sinensis were mainly collected by black light traps (until May). Since then, the number of Culex tritaeniorhynchus gradually increased and then declined in September. The largest number, a total of 12,624 mosquito vectors were collected in the Jinju region during collection. As the result of the Real‐time PCR experiment to detect the pathogens, no viruses had been detected, until now. But it requires sustainable and long‐term monitoring because infectious disease is expected to be spread in the long term.
[Show abstract][Hide abstract] ABSTRACT: Abstract Adult mosquito surveillance was conducted using black light traps in August of 2006 and 2007 at Wangging county and Yanji city, Jilin Province, China to identify the distribution of anopheline mosquitoes in northern China. A total of 2459 female mosquitoes comprising three genera and eight species including Anopheles (Anopheles) lesteri, An. (Ano.) kleini, An. (Ano.) pullus, Culex inatomii, Cx. orientalis, Cx. pipiens, Cx. bitaeniorhynchus and Aedes vexans nipponii were collected. The most commonly collected species was An. kleini which had not been previously reported from China. Anopheles sinensis sensu stricto is commonly collected throughout China, but was not collected from these areas.
[Show abstract][Hide abstract] ABSTRACT: Seven field-collected populations of German cockroach, Blattella germanica (L.) (ICN, DNH, CHN, DGU, BSN, GSN, and GWJ), were tested for susceptibility to eight different insecticides by a topical application method, and were compared to an insecticide-susceptible KSS strain. Marked regional variations of insecticide susceptibility were observed. Extremely high to high levels of resistance were observed in bifenthrin [resistance ratio (RR), 46–159], deltamethrin (RR, 61–160), and esfenvalerate [RR, 70–270; except for BSN females (RR, 20) and GSN females (RR, 24)]. Low to moderate levels of resistance were observed in cypermethrin [RR, 16–29; except for DGU females (RR, 88) and BSN females (RR, 41)], permethrin [RR, 11– 39; except for DNH females (RR, 110) and BSN females (RR, 44)], chlorpyrifos [RR, 2–13; except for GSN and GWJ females (RR, ca. 140)], chlorpyrifos-methyl (RR, 2–8), and fenthion (RR, 8–17). All of the colonies were susceptible to one or more of the insecticides examined. These results indicate that careful selection and rotational use of these insecticides should result in continued satisfactory control against field populations of German cockroach.
Journal of Asia-Pacific Entomology 10/2010; · 0.80 Impact Factor