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 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 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 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.     

Study of the independent gametophytes found on Jeju Island in South Korea and the first record of the obligate independent gametophyte of Antrophyum obovatum Baker

Fern gametophytes have often been neglected in research; however, studies on gametophytes are crucial for a better understanding of the evolution of ferns. During their life cycle, some gametophytes produce large and long‐lived populations without producing sporophytes and reproduce independently through asexual means, such as through the formation of gemmae. In this study, we investigated independent gametophytes on the Jeju Island of Korea, which was located on the land bridge between East China and Japan during the glacial periods. Fourteen gametophyte populations were collected from seven sites, of which 13 populations were clearly identified as belonging to four fern species known to occur in Jeju Island with BLAST searches using rbcL and trnL‐F sequences. Surprisingly, the last remaining population constituted undescribed taxa in Korea. We presented the first report of the independent gametophytes of Antrophyum obovatum Baker which has not been previously recorded in Korea. It has been supposed that many ferns sought suitable habitat throughout the land bridge between China and Japan. However, Jeju Island might be unsuitable for vittarioid ferns that prefer a tropical or subtropical environment. Consequently, only two species of vittariod ferns (A. obovatum and Haplopteris flexuosa (Fée) E.H. Crane) in the form of a gametophyte and sporophyte, respectively, exist on Jeju Island. Therefore, this gametophyte population must be protected and managed from a conservation perspective. In the case of the independent gametophyte of Hymenophyllum wrightii Bosch, haplotype analysis was conducted based on the rbcL sequences and the result supported that the North American populations were migrated from Japan through land bridge during the glacial periods and Jeju populations were recently established by long‐distance dispersal of the Japanese populations.     

Seasonal and diel patterns of biting midges (Ceratopogonidae) and mosquitoes (Culicidae) on the Parris Island Marine Corps Recruit Depot

The Marine Corps Recruit Depot on Parris Island, SC, is surrounded by tidal salt marshes, which are breeding habitats for many pestiferous biting flies. Knowledge of biting fly behavior patterns is needed to develop effective pest management strategies in urban areas adjacent to salt marshes. We measured biting midge (Ceratopogonidae) and mosquito (Culicidae) seasonal abundance and diel activity patterns on Parris Island using CO₂‐baited suction traps from November 2001 – November 2004. Of the three biting midge species collected, Culicoides furens was most abundant (86.2% of total) and was present in high numbers from late March to November. Culicoides hollensis (12.0% of total) was present during spring and fall but absent in summer and winter; and Culicoides melleus (1.7% of total) was present in spring through fall but absent in winter. Abundance of C. furens had a positive linear correlation with air temperature and rainfall. There were nonlinear correlations between air temperature and C. hollensis and C. melleus numbers, which were most abundant at moderate temperatures. Of 18 mosquito species collected, the most abundant were Aedes taeniorhynchus (42.7% of total), Aedes sollicitans (26.3% of total), Culex salinarius (15.6% of total), Culex quinquefasciatus (7.3% of total), and Aedes vexans (5.7% of total); other species comprised <5% of collections. Aedes taeniorhynchus numbers were positively correlated with temperature and rainfall, and Cx. salinarius was correlated with soil moisture. Activity of most biting midges and mosquitoes were highest the first two hours following sunset. Species of biting flies were present in all months, suggesting that year‐round control measures are necessary to reduce exposure to potential disease vectors and nuisance biting.     

Mosquitoes of Rarotonga,Cook Islands: A survey of breeding sites

Abstract

Two surveys of Rarotonga, Cook Islands (21°20^'S, 160°16^'W) were made to determine the mosquito fauna of the island, and to identify the habitats required for breeding by searching for larvae. The first survey was made during the “dry season” in May 2001, the second during the “wet season” in February 2002. The mosquito fauna comprised four species Culex (Culex) quinquefasciatus Say, Culex (Culex) annulirostris Skuse, Aedes (Stego‐myia) aegypti (Linnaeus) and Aedes (Stegomyia) polynesiensis Marks. Larvae of the Culex species were most often found in larger natural and artificial water bodies. The Aedes species bred in both natural and artificial containers of all sizes. Ae. polynesiensis was the most widespread species, using natural holes in all regions as well as artificial containers in the urban areas. Most larvae of Ae. aegypti were located in small artificial containers. The two Aedes species are the vectors of dengue fever on the island. Mosquito control during outbreaks should specifically target the artificial containers preferred by Aedes sp. for breeding habitats.     

Comparison of different trapping methods for surveillance of mosquito vectors of West Nile virus in Rhône Delta,France

Five trapping methods were compared for monitoring potential vectors of the West Nile virus in four areas in the Camargue Plain of France: carbon dioxide traps, bird‐baited traps, gravid traps, resting boxes, and human landing catches. A total of 73,721 specimens, representing 14 species, was trapped in 2006. Results showed significant differences in species and abundance between the type of traps. Many more specimens were collected using CO₂ traps than any other method, with an average of 212 specimens per night per trap (p<0.05). Culex pipiens was the most abundant species collected (36.8% of total with CO₂ traps), followed by Aedes caspius (22.7%), Anopheles hyrcanus (18.3%), Culex modestus (18.3%), and Aedes detritus (3.2%). Bird‐baited traps captured only eight specimens per night per trap on average, mainly Cx. pipiens (89.9%). The species collected and their abundance are influenced by the trap location, at ground or canopy level. Culex pipiens was twice as abundant in the canopy as on the ground, whereas it was the opposite for Ae. caspius, An. hyrcanus, and Ae. detritus. Culex modestus was equally abundant at both levels. Resting boxes and gravid traps were much less efficient, capturing around 0.3 specimens per night per trap. Results are discussed in relation to West Nile virus surveillance.     

Implications of Plasmodium parasite infected mosquitoes on an insular avifauna: the case of Socorro Island,México

Avian malaria (Plasmodium spp.) has been implicated in the decline of avian populations in the Hawaiian Islands and it is generally agreed that geographically isolated and immunologically naïve bird populations are particularly vulnerable to the pathogenic effects of invasive malaria parasites. In order to assess the potential disease risk of malaria to the avifauna of Socorro Island, México, we surveyed for Plasmodium isolates from 1,300 resident field‐caught mosquitoes. Most of them were identified as Aedes (Ochlerotatus) taeniorhynchus (Wiedemann, 1821), which were abundant in the salt marshes. We also collected Culex quinquefasciatus Say, 1823 close to human dwellings. Mitochondrial ND5 and COII gene sequences of Ae. taeniorhynchus were analyzed and compared to corresponding sequences of mosquitoes of the Galápagos Islands, Latin America, and the North American mainland. Aedes lineages from Socorro Island clustered most closely with a lineage from the continental U.S. Plasmodium spp. DNA was isolated from both species of mosquitoes. From 38 positive pools, we isolated 11 distinct mitochondrial Cytb lineages of Plasmodium spp. Seven of the Plasmodium lineages represent previously documented avian infective strains while four were new lineages. Our results confirm a potential risk for the spread of avian malaria and underscore the need to monitor both the mosquito and avian populations as a necessary conservation measure to protect endangered bird species on Socorro Island.     

A sensitive and reliable restriction enzyme assay to distinguish between the mosquitoes Culex torrentium and Culex pipiens

Culex pipiens pipiens Linnaeus and Culex torrentium Martini (Diptera: Culicidae) are closely related vector species that exist sympatrically in Europe. The two species are morphologically almost identical and can only be distinguished with certainty by characters of the male genitalia. Hence, correct species identification and conclusions on distribution and vector status are very difficult and often neglected. Therefore, we developed a reliable and simple mitochondrial cytochrome c oxidase subunit I (COI) gene restriction enzyme assay to discriminate between Cx. pipiens and Cx. torrentium, based on the analysis of morphologically identified male specimens. We sequenced approximately 830 bp in the 3′ region of the mitochondrial COI gene of 18 morphologically identified males of Cx. pipiens and Cx. torrentium. Two restriction enzymes (FspBI and SspI) that could distinguish between the two species according to species‐specific differences in these sequences were chosen. The restriction enzymes were tested on 227 samples from Sweden and verified by sequencing 44 of them. The enzyme FspBI correctly identified all investigated samples; the enzyme SspI identified all samples except one Cx. torrentium. We hope the method and the findings presented here will help to shed light on the true distribution and relative proportions of the two species in Europe.     

Chromosome-level assembly of Culex pipiens molestus and improved reference genome of Culex pipiens pallens (Culicidae,Diptera)

Culex pipiens molestus and Culex pipiens pallens are two distinct bioforms in the Culex pipiens complex that are important vectors of several pathogens and are widely distributed around the world. In the current study, we present a high-quality chromosome-level genome of Cx. pipiens f. molestus and describe the genetic characteristics of this genome. The assembly genome was 559.749 Mb with contig and scaffold N50 values of 200.952 Mb and 0.370 Mb, and more than 94.78% of the assembled bases were located on 3 chromosomes. A total of 19,399 protein-coding genes were predicted. Many gene families were expanded in the genome of Cx. pipiens f. molestus, particularly those of the chemosensory protein (CSP) and gustatory receptor (GR) gene families. In addition, utilizing Hi-C data, we improved the previously assembled draft genome of Cx. pipiens f. pallens, with scaffold N50 of 186.195 Mb and contig N50 of 0.749 Mb, and more than 97.02% of the assembled bases were located on three chromosomes. This reference genome provides a foundation for genome-based investigations of the unique ecological and evolutionary characteristics of Cx. pipiens f. molestus, and the findings in this study will help to elucidate the mechanisms involved in species divergence in the Culex pipiens complex.     

Wide recognition of Culex pipiens and lack of detection of Culex torrentium through biomolecular differentiation of mosquitoes in the Emilia‐Romagna region,Northern Italy

The Culex pipiens complex includes species with reported differences in vector competence for arthropod‐borne viruses, many of which are of significant importance to human health such as the West Nile virus and the Sindbis virus. This group of mosquitoes is difficult to distinguish morphologically; particularly as adult females. In Europe, the two species of the complex, Culex pipiens Linnaeus 1758 and Culex torrentium Martini 1925, are often found sympatrically. With the aim to characterize the presence and spread of both species in the Emilia‐Romagna region, Northern Italy, mosquitoes of the complex – collected during the West Nile virus surveillance plans – were tested by multiplex real‐time PCR for the detection of the two species Cx. pipiens and Cx. torrentium. A total of 24 165 mosquitoes, collected between 2012 and 2014 from 105 sites, and sorted in 204 pools, were tested. All tested pools were found to be composed of Cx. pipiens, whereas Cx. torrentium was not detected. These results indicate a likely absence of Cx. torrentium mosquitoes within the surveyed territory, whereas Cx. pipiens is widely distributed in the area mentioned. This is in line with previous reports, which describe a pre‐alpine distribution of Cx. torrentium in Italy.     

Blood‐feeding ecology of mosquitoes in zoos

To determine if the unique host assemblages in zoos influence blood‐feeding by mosquitoes (Diptera: Culicidae), a sampling programme was conducted in Greenville and Riverbanks Zoos, South Carolina, U.S.A., from April 2009 to October 2010. A total of 4355 female mosquitoes of 14 species were collected, of which 106 individuals of nine species were blood‐fed. The most common taxa were Aedes albopictus (Skuse), Aedes triseriatus (Say), Anopheles punctipennis (Say), Culex erraticus (Dyar & Knab), Culex pipiens complex (L.) and Culex restuans (Theobald). Molecular analyses (cytochrome b) of bloodmeals revealed that mosquitoes fed on captive animals, humans and wildlife, and took mixed bloodmeals. Host species included one amphibian, 16 birds, 10 mammals (including humans) and two reptiles. Minimum dispersal distances after feeding on captive hosts ranged from 15.5 m to 327.0 m. Mosquito–host associations generally conformed to previous accounts, indicating that mosquito behaviour inside zoos reflects that outside zoos. However, novel variation in host use, including new, exotic host records, warrants further investigation. Zoos, thus, can be used as experiment environments in which to study mosquito behaviour, and the findings extrapolated to non‐zoo areas, while providing medical and veterinary benefits to zoo animals, employees and patrons.     

Spider Fauna of Jeju Island in Korea

A critical check list of the spiders in Jeju island, Korea is presented with review of published reports from 1936 to 2001 and identification of the authors' specimens collected from 1964 to 2001. Total 166 genera 347 species belonging to 36 families of spiders was classified in Jeju Island. The species composition of spiders in Jeju island comprises about 52% of total number of Korean spider species. Dominant spider families with species abundance were Araneidae, Salticidae, Theridiidae, Linyphiidae and Lycosidae. The spider fauna of Jeju island is under strong influence of northern species which are Holarctic and Palearctic species.     

An unsettling explanation for the failure of skatole‐baited ovitraps to capture Culex mosquitoes

Culex mosquitoes are primarily found in temperate and tropical regions worldwide where they play a crucial role as main vectors of filarial worms and arboviruses. In Recife, a northeast city in Brazil, high densities of Culex quinquefasciatus are often found in association with human populated areas. In marked contrast to another part of the city, field tests conducted in the neighborhood of Sitio dos Pintos showed that trapping of mosquitoes in skatole-baited ovitraps did not differ significantly from captures in control (water) traps. Thus, classical and molecular taxonomic approaches were used to analyze the Culex species circulating in Sitio dos Pintos. Results obtained from both approaches agreed on the cocirculation of Culex quinquefasciatus and Culex nigripalpus in three different areas of this neighborhood. What was initially considered as an unexpected failure of this lure turned out to be a more unsettling problem, that is, the first report in Recife of Culex nigripalpus, a vector of Venezuelan equine encephalitis virus and West Nile virus. Unplanned urbanization processes close to remnants of the Atlantic forest, such as observed in Sitio dos Pintos, may have contributed to the introduction of Cx. nigripalpus in urban areas.     

The arbovirus vector Culex torrentium is more prevalent than Culex pipiens in northern and central Europe

Two species of arbovirus vector, Culex torrentium and Culex pipiens (Diptera: Culicidae), occur in several European countries, but difficulties in their accurate identification and discrimination have hampered both detailed and large‐scale distribution and abundance studies. Using a molecular identification method, we identified to species 2559 larvae of Cx. pipiens/torrentium collected from 138 sites in 13 European countries ranging from Scandinavia to the Mediterranean coast. In addition, samples of 1712 males of Cx. pipiens/torrentium collected at several sites in the Czech Republic were identified to species based on the morphology of their hypopygia. We found that the two species occur together in large areas of Europe, and that Cx. torrentium dominates in northern Europe and Cx. pipiens dominates south of the Alps. The transition in dominance occurs in central Europe, where both species are roughly equally common. There was a strong correlation between the length of the growing season at different sites and occurrences of the two species. As the growing season increases, the proportion and detection of Cx. torrentium decrease, whereas those of Cx. pipiens increase. The present findings have important consequences for the interpretation of the results of studies on major enzootic and link‐vectors of mosquito‐borne bird‐associated viruses (i.e. Sindbis, West Nile and Usutu viruses), especially in central Europe and Scandinavia.     

Tolerance to individual and joint effects of arsenic and Bacillus thuringiensis subsp,israelensis or Lysinibacillus sphaericus in Culex mosquitoes

Arsenic contamination of global water supplies has come to the forefront in policy decisions in recent decades. However, the effects of arsenic on lower trophic levels of insects inhabiting contaminated ecosystems are not well understood. One approach to document both acute and sublethal effects of toxicants like arsenic is to assay them in combination with microbial pathogens to evaluate shifts in survival curves of the test organisms. Larvae of Culex quinquefasciatus and Culex tarsalis were reared in water containing 0 or 1 000μg/L of arsenate or arsenite. Fourth instars were then exposed to a range of doses of Bacillus thuringiensis subsp, israelensis （Bti） or Lysinibacillus sphaericus （Ls）, with shifts in lethal concentrations determined. Arsenic accumulation in 4th instars was also quantified, and a relative growth index （RGI） calculated for the treatments and compared to controls. Larvae of both species accumulated between 4 447 ± 169 ng As/g and 6 983 4- 367 ng As/g, though RGI values indicated accumulation did not affect growth and development. In all cases, the LC50＇s and LC90＇s of Cx. quinquefasciatus exposed jointly with arsenic and Bti/Ls were higher than Cx. tarsafis. Cx. tarsafis reared in arsenite showed a significant reduction in their Bti LC90 values compared to the control, indicating a sublethal effect of Bti. When exposed jointly with Ls, arsenite was more toxic than arsenate in Cx. tarsalis. Overall, these results indicate tolerance of these Culex species to arsenic exposures, and why this may occur is discussed.     

蚊幼虫体表微细结构的扫描电镜观察及分类学研究

本文用扫描电镜观察、比较了14种库蚊和6种其他蚊属的幼虫颅壳、呼吸管及尾节的体表微细结构,发现在颅壳上的微棘排列成多角形,在呼吸管和尾节上的微棘则排列成直线.这些微棘在不同区域排列有变化,但在固定的区域却很稳定,具有种内稳定性和种间差异,可以作为分类特征.本文共对20种蚊幼虫的体表微棘图式进行了描述,并以组为单位,对同组内各近似种的微棘图式进行比较和小结,提出它们的区别特征,用于鉴别近似种;根据体表图式,对库蚊个别种类的分类位置提出了不同的看法,讨论了体表微棘的起源及其分类的意义.     

Population Genetic Structure of the Endangered <Emphasis Type="Italic">Brasenia schreberi</Emphasis> in South Korea Based on Nuclear Ribosomal Spacer and Chloroplast DNA Sequences

Genetic variation of nuclear ribosomal ITS (nrITS) and chloroplast DNA (cpDNA) regions was investigated in Brasenia schreberi (Cabombaceae) to assess the population structure and to infer the evolutionary relationship among 12 populations distributed in South Korea. The combined sequence of the two regions was aligned to 2,069 bp, of which 28 sites were variable. In total, 20 genotypes were identified from 240 individuals of B. schreberi. Genotype diversity (Gd) and nucleotide diversity (Pi) on Jeju Island (Gd = 0.2511, Pi = 0.00012) were higher than those of the mainland of South Korea (Gd = 0.1358, Pi = 0.00005). The relatively low level of genetic variation of the mainland populations is associated with its higher genetic differentiation (G _ST = 0.095 on mainland and 0.039 on Jeju Island) and human activities. Minimum spanning network analysis demonstrated that the investigated populations of B. schreberi were subdivided into two geographical groups: the mainland of South Korea and Jeju Island. In addition, analysis of molecular variation showed that a large proportion (73.55%) of genetic differentiation existed between the two regions. These results strongly suggest the presence of significant barriers to gene flow between regions. Thus, the management unit for B. schreberi should be carefully designed to avoid the potential risk that can results from the admixture of individuals from the mainland and Jeju Island regions.     

Insecticide susceptibility and resistance of Culex tritaeniorhynchus (Diptera: Culicidae) larvae collected from Gwangju,Republic of Korea

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 (LC₅₀), 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. tritaeniorhynchus 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 LC₅₀ and concentration that produced 90% mortality (LC₉₀), respectively. 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 (RRLC₅₀), respectively.