Seasonal Prevalence of Mosquitoes Collected from Light Traps in Korea (1999-2000)

ABSTRACT Adult mosquito collections were conducted from 1999 through 2000 at 29 US military installations located in six provinces in the Republic of Korea (ROK). Adult mosquitoes were collected in New Jersey light traps from 15 May to 15 October each year. Adult mosquito surveillance was conducted to determine the appropriate time for pesticide applications at each of the Army installations. A total of 68,051 and 62,526 adults were collected in 1999 and 2000 respectively, comprising 53,983 (79.3%) females and 14,068 (20.7%) males in 1999, and 50,274 (80.4%) females and 12,252 (19.6%) males in 2000. A total of 19 species from 7 genera were collected. The most common species collected were Anopheles sinensis (34.2%), Culex tritaeniorhynchus (29.4%), Aedes vexans nipponii (18.2%) and Culex pipiens (16.8%). Anopheles sinensis were collected at the same level while Culex tritaeniorhynchus decreased by 6.2% in 2000. The weekly population densities for some species were variable for each of the years, apparently as a result of changing weather conditions.     

Seasonal Prevalence of Mosquitoes Collected from Light Traps in the Republic of Korea, 2002

Adult mosquito surveillance was conducted during 2002 at 30 US military installations and training sites located in six provinces in the Republic of Korea (ROK). Adult mosquitoes were collected in New Jersey and dry ice ‐baited New Jersey light traps from 1 May through 15 October. Mosquito surveillance was conducted to determine threshold levels to initiate pesticide applications and identify malaria infection rates at selected Army installations and training sites. A total of 100,617 adults [82,410 (81.9%) females and 18,207 (18.1%) males] comprising 17 species and 7 genera were collected during 2002. The most common species collected were Culex tritaeniorhynchus Giles (49.5%), Anopheles sinensis Wiedemann (30.9%), Culex pipiens Coquillett(11.8%) and Aedes vexans nipponii (Theobald) (7.1%). Trap indices (TIs) varied widely for species over their range, due in part, to geographical distribution and degree of association with urban communities. Anopheles sinensis were collected at the same level while Culex tritaeniorhynchus increased by 27.2% in 2001, due in part to very high populations of Culex tritaeniorhynchus at Gunsan Air Base. The weekly population densities for some species were variable for each of the years, apparently as a result of variable annual weather conditions. None of Anopheles sp. assayed for plasmodium vivax (Pv) malaria infections by Enzyme Linked Immunosorbent Assay (ELISA) were positive.     

Seasonal Prevalence of Mosquitoes Collected from Light Traps in the Republic of Korea, 2001

ABSTRACT Adult mosquito surveillance was conducted during 2001 at 28 US military installations and training sites located in five provinces in the Republic of Korea (ROK). Adult mosquitoes were collected in New Jersey and dry ice-baited CDC-type light traps from 1 May through 15 October. Mosquito surveillance was conducted to determine threshold levels to initiate pesticide applications and identify malaria infection rates at selected Army installations and training sites. A total of 61,584 adults [45,814 (74.4%) females and 15,770 (25.6%) males] comprising 17 species and 7 genera were collected during 2001. The most common species collected were Anopheles sinensis Wiedemann (36.3%), Aedes vexans nipponii (Theobald) (23.1%), Culex tritaeniorhynchus Giles (22.3%) and Culex pipiens Coquillett (17.6%). Trap indices (TIs) varied widely for species over their range, due in part, to geographical distribution and degree of association with urban communities. During 2001, the TI for An. sinensis was 19.6 females/trap night compared to years 1999 and 2000, when the TI for the Munsan area was 1.4 and 2.9 times (27.7 and 57.4 TI) greater, respectively. The weekly population densities for some species were variable for each of the years, apparently as a result of variable annual weather conditions. None of the 16,302 Anopheles sinensis assayed for plasmodium vivax (Pv) malaria infections by Enzyme Linked Immunosorbent Assay (ELISA) were positive.     

Seasonal prevalence of mosquitoes collected from light traps in the Republic of Korea, 2007

Adult mosquito surveillance was conducted using New Jersey light traps from 1 May to 15 October during 2007 at 14 US Army and three Air Force installations and two US Army training sites located in six provinces in the Republic of Korea to determine threshold levels to initiate pesticide applications based on trap indices. A total of 24 013 adult mosquitoes (19 763 [82.3%] females and 4250 [17.1%] males) comprising 16 species (including five members of the Anopheles Hyrcanus Group) and belonging to seven genera were collected. Females of the most commonly collected species were members of the Anopheles Hyrcanus Group (52.1%), followed by, Culex tritaeniorhynchus Giles (20.6%), Culex pipiens Coquillett (13.8%), and Aedes vexans nipponii (Theobald) (11.6%). Trap indices varied widely for species over their range, due in part, to geographical distribution and degree of association with urban or rural communities.     

Seasonal prevalence and host-seeking of mosquitoes in southeastern Republic of Korea

Adult mosquito surveillance was conducted at two sites at Gijang-gun, Busan southeastern area of the Korean peninsula, in 2004. The most frequently collected species at cow sheds were Anopheles sinensis sensu lato (s.l.) (83.4%), followed by Culex tritaeniorhynchus Giles (8.2%), Culex pipiens Coquillett (5.6%) and Aedes albopictus (Skuse) (2.4%). Adult populations of An. sinensis s.l. peaked during July (Trap Index, TI 1043.1), declining in August (TI 659.4) and September (TI 462.9) in 2004, while Cx. tritaeniorhynchus populations increased in August (TI 77.5) and September (TI 35.9). Adult Cx. tritaeniorhynchus was first collected in the second week of May (TI 4.0) and increased through August with two population peaks in the third week of July (TI 98.0) and the second week of August (TI 99.5). Armigeres subalbatus (Coquillett) was the most frequently collected mosquito at human-landing collections (30.4%) followed by An. sinensis s.l. (28.6%) and members of the Cx. pipiens complex (19.3%). Anopheles sinensis s.l. demonstrated two peaks of host-seeking activity at 22.00–23.00 hours and 02.00–03.00 hours in July, while in August the host-seeking peaks appeared at 22.00–23.00 hours and 03.00–04.00 hours. The black light trap collections of An. sinensis and Cx. tritaeniorhynchus demonstrated significant correlations to the ambient temperatures.     

Seasonal prevalence of mosquitoes collected from light traps in the Republic of Korea, 2005

Adult mosquito surveillance was conducted during 2005 at 22 US military installations and two training sites located in six provinces in the Republic of Korea. Adult mosquitoes were collected in New Jersey light traps from 1 May to 15 October to determine threshold levels to initiate pesticide applications based on trap indices. A total of 27 363 adult mosquitoes (22 368 [81.7%] females and 4995 [18.3%] males) comprising 15 species (including five members of the Anopheles sinensis group) belonging to seven genera were collected. The most common species collected were members of the Anopheles sinensis Wiedemann group (50.2%), followed by Culex tritaeniorhynchus Giles (30.6%), Aedes vexans nipponii (Theobald) (11.8%), and Culex pipiens Coquillett (6.3%) females. Trap indices varied widely for species over their range, due in part to geographical distribution and degree of association with urban or rural communities.     

Seasonal prevalence of mosquitoes collected from light traps in the Republic of Korea, 2006

Adult mosquito surveillance was conducted during 2006 at 22 US Army and Air Force installations and two training sites located in six provinces in the Republic of Korea. Adult mosquitoes were collected in New Jersey light traps from 1 May through 15 October 2006 to determine threshold levels to initiate pesticide applications based on trap indices. In total 16 217 adult mosquitoes [13 612 (83.9%) females and 2605 (16.1%) males] comprising 16 species (including five members of the Anopheles sinensis Group) belonging to eight genera were collected. Females of the most commonly collected species were members of the Anopheles sinensis Wiedemann Group (58.9%), followed by Aedes vexans nipponii (Theobald) (21.3%), Culex tritaeniorhynchus Giles (11.8%) and Culex pipiens Coquillett (5.2%). Trap indices varied widely for species over their range, due in part, to their geographical distribution and degree of association with urban or rural communities.     

Seasonal prevalence of mosquitoes collected from light traps in the Republic of Korea in 2003

Surveillance of adult mosquitoes was conducted at 29 US military installations and training sites in six provinces in the Republic of Korea during 2003. Adult mosquitoes were collected in New Jersey light traps and dry ice‐baited New Jersey light traps from 1 May to 15 October. Mosquito surveillance was conducted to determine threshold levels to initiate pesticide applications and identify malaria infection rates at selected army installations and training sites. A total of 42 024 adult mosquitoes (32 594 females [77.6%] and 9430 males [22. 4%]) comprising 14 species and Anopheles sinensis s.l. (a complex of five species), representing seven genera, were collected. The most common species were members of the Anopheles sinensis Wiedemann complex (54.9%), followed by Aedes vexans nipponii (Theobald) (19.0%), Culex pipiens Coquillett (14.3%) and Culex tritaeniorhynchus Giles (10.6%). Trap indices varied widely for species over their range, due in part to geographical distribution and degree of association with urban communities.     

Seasonal prevalence of mosquitoes collected from light traps with notes on malaria in the Republic of Korea, 2004

Adult mosquito surveillance was conducted during 2004 at 29 US military installations and training sites located in six provinces in the Republic of Korea. Adult mosquitoes were collected in New Jersey light traps and Magnet traps from 1 May through 15 October to determine threshold levels to initiate pesticide applications and to identify malaria infection rates at selected army installations and training sites. A total of 89 206 adults (78 454 [87.9%] females and 10 752 [12.1%] males) comprising 20 species (including five members of the Anopheles Hyrcanus Group) and belonging to seven genera were collected. The most common species collected were members of Culex tritaeniorhynchus Giles (49.4%) and Anopheles sinensis Wiedemann complex (39.1%), followed by Culex pipiens Coquillett (6.1%) and Aedes vexans nipponii (Theobald) (4.2%). Trap indices varied widely for species over their range, due in part to geographical distribution and degree of association with urban communities.     

Seasonal Abundance of Deer and Horse Flies (Diptera: Tabanidae) in the Northern Part of Gyeonggi-do,Republic of Korea

The seasonal abundance of horse and deer flies (family Tabanidae) was analyzed using Mosquito Magnet^® traps at 5 sites located near/in the demilitarized zone, northern Gyeonggi-do, Republic of Korea from late April to early October for 4 consecutive years (2010-2013). A total of 2,999 horse and deer flies (tabanids) belonging to 5 genera and 20 species were collected. Chrysops mlokosiewiczi (90.9%) was the most frequently collected, followed by Haematopota koryoensis (4.8%) and C. suavis (1.0%). The remaining 17 species comprised only of 3.3% of all species collected. C. mlokosiewiczi demonstrated bimodal peak populations during mid-June and early August, while H. koryoensis demonstrated a unimodal peak during mid-July. Overall numbers of tabanids collected were influenced by the previous year’s winter temperatures and precipitation. Population abundance was influenced by habitat with most of tabanids collected from habitats near forested areas, followed by rice paddies, and a beef farm.     

Tabanid Flies (Diptera: Tabanidae) of the Northern Part of Gyeonggi Province, Republic of Korea

Tabanid flies were surveyed using New Jersey light traps and Mosquito Magnet® traps at US Army installations and training sites in the northern part of Gyeonggi Province, Republic of Korea. A total of 344 tabanid flies, comprising 14 species and 5 genera, were collected from June to August during 2003‐2004. Dominant species were Chrysops vanderwulpi (57.3%), Haematopota sinensis (29.1%), Haematopota koryoensis (4.4%) and Tabanus mandarinus (2.3%). Mosquito Magnet traps that generated CO₂through the combustion of propane gas were nearly 6 times more effective in collecting tabanid flies than New Jersey light traps. Based on Mosquito Magnet trap collections, peak populations occurred from mid‐June to early July.;     

Distribution of overwintering mosquitoes (Diptera: Culicidae) in grassy fields in the Republic of Korea, 2007–2008

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.     

Seasonal Distribution of Ticks in Four Habitats near the Demilitarized Zone,Gyeonggi-do (Province), Republic of Korea

This study describes the seasonal distribution of larvae, nymph, and adult life stages for 3 species of ixodid ticks collected by tick drag and sweep methods from various habitats in the Republic of Korea (ROK). Grasses less than 0.5 m in height, including herbaceous and crawling vegetation, and deciduous, conifer, and mixed forests with abundant leaf/needle litter were surveyed at United States (US) and ROK operated military training sites and privately owned lands near the demilitarized zone from April-October, 2004 and 2005. Haemaphysalis longicornis Neumann adults and nymphs were more frequently collected from April-August, while those of Haemaphysalis flava Neumann and Ixodes nipponensis Kitaoka and Saito were collected more frequently from April-July and again during October. H. longicornis was the most frequently collected tick in grass habitats (98.9%), while H. flava was more frequently collected in deciduous (60.2%) and conifer (57.4%) forest habitats. While more H. flava (54.1%) were collected in mixed forest habitats than H. longicornis (35.2%), the differences were not significant. I. nipponensis was more frequently collected from conifer (mean 8.8) compared to deciduous (3.2) and mixed (2.4) forests.     

Enterobius vermicularis Infection among Preschool Children: A 12-Year (2008–2019) Survey in Large Cities and Provinces of the Republic of Korea

A 12-year nationwide survey (2008–2019) was performed to investigate the prevalence of Enterobius vermicularis infection among preschool children in Seoul, 4 large cites (Busan, Incheon, Daegu, and Ulsan), and 9 provinces (grouped into 5 localities) in the Republic of Korea (=Korea). The survey was carried out once a year by 16 regional offices of the Korea Association of Health Promotion. The cello-tape perianal swab method (1 smear per child) was applied to detect eggs of E. vermicularis and other helminths. According to the results, the egg positive rate of E. vermicularis infection in 2008–2009 was 1.8–2.0%, but it decreased gradually to 0.6% in 2019 (P<0.05). The prevalence was significantly higher in boys (0.7–5.0%, mean 1.8%) than in girls (0.5–2.8%, mean 1.3%) (P<0.05). The 2 most southern localities, Jeju-do (Province) and Jeolla-do (inclusive of Jeollabuk-do and Jeollanam-do) and a mid-western province, Gyeonggi-do, revealed higher prevalences, whereas Seoul and Gangwon-do showed lower prevalences. The results indicate that a low-grade prevalence of E. vermicularis infection (less than 4%) has been maintained for the recent 12 years among preschool children in Korea. Continuous monitoring of enterobiasis in the child age group is necessary in Korea.     

Ecology of Hantaan virus at Twin Bridges Training Area,Gyeonggi Province,Republic of Korea, 2005–2007

The Twin Bridges Training Area (TBTA) in the Republic of Korea consists of dirt roads, barren training areas, and forested hillsides adjacent to linear and broad expanses of tall grasses, herbaceous, and scrub vegetation. Of the six species of small mammals, the striped field mouse, Apodemus agrarius, was the most frequently captured (96.1%). Apodemus agrarius capture rates varied from 17.7 to 33.2% during three trapping periods. Gravid females were observed during November‐December 2006 (8.4%) and March 2007 (5.1%). In 2005, the overall seroprevalence of Hantaan virus (HTNV) was high (34.4%) and lower during surveys in 2006 (14.2%) and 2007 (13.8%). Seroprevalence was directly correlated with weight increase of A. agrarius.     

Ornithodoros sawaii (Ixodida: Argasidae) Larvae Collected from Hydrobates monorhis on Sogugul and Gaerin Islands,Jeollanam-do (Province), Republic of Korea

The 65th Medical Brigade and Public Health Command District-Korea, in collaboration with the Migratory Bird Research Center, National Park Research Institute, conducted migratory bird tick surveillance at Sogugul and Gaerin Islands (small rocky bird nesting sites), Jeollanam-do (Province), Republic of Korea (ROK), on 30 July and 1 August 2009. Breeding seabirds captured by hands in their nesting burrows were banded, identified to species, and carefully examined for ticks during the nesting season. A total of 9 Ornithodoros sawaii larvae were removed from 4 adult Hydrobates monorhis (Swinhoe’s storm petrel). The identification of the larvae of O. sawaii collected from migratory seabirds were molecularly confirmed using mitochondrial 16S rDNA primer sets.     

New Records and Reference Collection of Mosquitoes (Diptera: Culicidae) on Jeju Island, Republic of Korea

Mosquito collections were carried out during 2003‐2004 on Jeju Island, Republic of Korea. Eighteen species of mosquitoes in 7 genera were collected, including three new records, Culex (Culex) mimeticus, Culex (Culiciomyia) sasai and Ochlerotatus (Finlaya) nipponicus. Based on the available information, a total of 28 species representing 7 genera have been recorded from Jeju Island. Larval habitat characteristics, collection sites, bionomics, and vector potential for each of these species are described.     

Ecological surveillance of small mammals at Dagmar North Training Area,Gyeonggi Province,Republic of Korea, 2001–2005

A seasonal rodent‐borne disease surveillance program was established at Dagmar North Training Area located near the demilitarized zone, Republic of Korea, from 2001 through 2005. Selected habitats surveyed included earthen banks separating rice paddies, fighting positions along a 5 m rock‐faced earthen berm, and extensive tall grasses with various degrees of herbaceous and scrub vegetation associated with dirt roads, rice paddies, ditches, ponds, or the Imjin River. Of the nine species of small mammals captured, the striped field mouse (Apodemus agrarius), the primary reservoir for Hantaan virus, was the most frequently collected, representing 92.5% of the 1,848 small mammals captured. Males were captured similarly to females during the spring and summer seasons but were captured less frequently during the fall and winter seasons. Gravid rates were highest in the fall (25.5–57.3%) with the lowest rates during the summer (0.0–2.2%). Capture rates were the lowest along earthen banks separating rice paddies (5.5%) and highest in unmanaged tall grasses and crawling vegetation (15.3–43.5%). An increased knowledge of ecological factors that impact the abundance and distribution of small mammals and the associated ectoparasites and pathogens they harbor is critical for developing accurate disease risk assessments and mitigation strategies for preventing vector‐ and rodent‐borne diseases among soldiers training in field environments.     

Insecticide Susceptibility of Field‐collected Blattella germanica (Blattaria: Blattalidae) in Busan,Republic of Korea during 2014

The susceptibility values for field‐collected (BG‐BG) and laboratory (KS‐BG) strains of German cockroaches (BS‐BG), Blattella germanica (L.) to five synthetic pyrethroid and three organophosphate insecticides were assessed by topical application. Both KS‐BG and BS‐BG strains demonstrated the highest levels of susceptibility to deltamethrin with LD₅₀ values of 0.0035 μg/female and 1.5744 μg/female, respectively. The KS‐BG strain demonstrated the lowest susceptibility level to fenthion with an LD₅₀ value of 0.0698 μg/female, while the BS‐BG field population showed the lowest susceptibility to bifenthrin with 4.6811 μg/female. The BS‐BG field population showed resistance levels of 50 to 640 fold higher against the eight pesticides evaluated compared to the KS‐BG strain. The resistance ratios (RR) of the eight pesticides were compared using populations of B. germanica that were collected from the same locality during 2007 and 2014. The field population of B. germanica collected during 2014 demonstrated significantly high resistance to an organophosphates and all pyrethroids when compared with those collected during 2007, but RR values were <10 except for chlorpyrifos‐methyl and chlorpyrifos with RR values of 74 and 104, respectively.