Population dynamics of five anopheles species of the Hyrcanus group in northern Gyeonggi-do, Korea.

To investigate the population densities of potential malaria vectors, Anopheles species were collected by light traps in malaria endemic areas, Paju and Gimpo, Gyeonggi-do of Korea. Five Anopheles Hyrcanus sibling species (An. sinensis, An. pullus, An. lesteri, An. kleini, and An. belenrae) were identified by PCR. The predominant species, An. pullus was collected during the late spring and mid-summer, while higher population consists of An. sinensis were collected from late summer to early autumn. These 2 species accounted for 92.1% of all Anopheles mosquitoes collected, while the other 3 species accounted for 7.9%. Taking into account of these population densities, late seasonal prevalence, and long-term incubation period (9-13 months) of the Korean Plasmodium vivax strain, An. sinensis s.s is thought to play an important role in the transmission of vivax malaria in the study areas.

Survey of IgE Reactivity to Nonbiting Midges in Korea and Identification of IgE-Binding Protein.

PURPOSE: Chironomids (nonbiting midges) are widely and abundantly distributed near ponds, rivers, and artificially dammed pools used for irrigation. Chironomids contain allergens and cause airway allergy in humans. In this study, we aimed to examine the allergic potential of chironomids in inhabitants living near artificially dammed pools. METHODS: We examined immunoglobulin E (IgE) reactivity to chironomid extracts in the sera of residents living around installed dams and assessed the correlations of IgE responses between chironomids (Chironomus flaviplumus, Chironomus kiiensis, Cricotopus bicinctus) and house dust mites (Dermatophagoides farinae). In addition, we identified potential IgE binding proteins specific for adult C. bicinctus, a popular species in Korea. Specific IgE antibodies in sera collected from the participants against the extracts were tested using enzyme-linked immunosorbent assay (ELISA). RESULTS: The average IgE-positive rates were 10.4%, 8.1%, and 8.2% in C. bicinctus, C. flaviplumus, and C. kiiensis, respectively. The IgE-positive rate and IgE titer of C. bicinctus antigen were higher in residents living around installed dams than in those who lived other places (P = 0.013). Western blotting using sera having high IgE titers to C. bicinctus in ELISA showed the presence of a protein of approximately 42 kDa that was homologous to the actin protein isoform in C. bicinctus extracts as demonstrated using mass spectrometry. CONCLUSIONS: Our results showed that people living near installed dams were more sensitized to C. bicinctus and that the 42 kDa IgE-binding protein could be useful for further studies on chironomid allergic disease and clinical applications.

Preliminary observation on the gradient distribution of hibernating females of Anopheles sinensis and Anopheles pullus in the Republic of Korea.

Hibernating females of the Anopheles hyrcanus complex were collected at 4 different latitudes at the end of the hibernation period in March of 2005 and 2006, and species were confirmed by polymerase chain reaction (PCR) identification. At Paju (37.8 degrees N; average temperature in December February = -3.5 degrees C) 74.6% of the females collected were An. pullus and 22.4% were An. sinensis. At Seosan (36.8 degrees N; December-February average temperature = -1.0 degrees C) and Buan (35.7 degrees N; December-February average temperature = 0.4 degrees C) 14.7% and 14.8% were An. pullus, and 85.3% and 85.2% were An. sinensis, respectively. At Haenam (34.6 degrees N; December-February average temperature = 3.1 degrees C) only An. sinensis was found. Our preliminary results indicate that An. sinensis, unlike An. pullus, is not adapted to survive in cold weather.

Molecular cloning and the allergenic characterization of tropomyosin from Tyrophagus putrescentiae.

Storage mites have been recognized as a cause of asthma and rhinitis. Studies from several countries have shown that the IgE-mediated allergy to storage mites is of considerable importance, especially in rural populations. This study aimed to identify and characterize new allergens from Tyrophagus putrescentiae. A partial cDNA sequence encoding tropomyosin was isolated from the cDNA library by immunoscreening using anti-mouse IgG1 sera raised against T. putrescentiae whole body extract. The deduced amino acid sequence shares 64-94% identity with previously known allergenic tropomyosins. Its recombinant protein was produced by using a pET 28b expression system and purified by affinity chromatography using Ni-NTA agarose. The IgE reactivities of tropomyosins from T. putrescentiae and Dermatophagoides farinae were compared by enzyme linked immunosorbent assay (ELISA). Recombinant Tyr p 10 showed 12.5% (5/40) IgE-binding reactivity, whereas recombinant Der f 10 showed 25% (10/40) IgE-binding reactivity against the same sera from storage mite-sensitized and house dust mite-sensitized subjects. Both recombinant Tyr p 10 and Der f 10 showed little inhibition of IgE binding to T. putrescentiae crude extract by ELISA. Tropomyosin seems to contribute only a small portion of the cross-reactivity with house dust mites.

Outbreak of vivax malaria in areas adjacent to the demilitarized zone, South Korea, 1998.

Malaria had been eradicated in the Republic of Korea (South Korea) by the late 1970s. In 1993, a soldier was infected with Plasmodium vivax malaria in the Demilitarized Zone (DMZ; the border area between North and South Korea), and since then, the number of cases has been steadily increasing year after year. In 1998, 3,932 vivax malaria cases were microscopically confirmed, affecting 2,784 (70.8%) soldiers (including discharged soldiers) and 1,148 (29.2%) civilians. These cases occurred throughout the year, peaking in July (30.1%) and August (30.5%). Most of the patients were infected in areas in or near the DMZ. Taking into consideration entomologic, socioecologic, and epidemiologic factors, it is postulated that there has been an epidemic of malaria in North Korea since 1993, with the number of cases increasing yearly; the continuous infiltration across the DMZ from North Korea of infected female mosquitoes of the vector species Anopheles sinensis resulted in an outbreak of vivax malaria in the DMZ of South Korea.

Molecular evidence for synonymy of Anopheles yatsushiroensis and An. pullus.

Identification of species members of the Hyrcanus Group of Anopheles is difficult because of intraspecific variation in and interspecific similarity among key characters. Hibernating female Anopheles pullus were collected and 6 adults were individually reared. All F1 progeny of wild-caught An. pullus were morphologically identical to An. yatsushiroensis. The 5.8S rDNA-ITS2-28S rDNA region from each of 3 An. pullus and An. yatsushiroensis (wild-caught females) and a portion of the mitochondrial cytochrome oxidase 1 genes from 1 individual of the 2 species were sequenced. The same gene regions from an An. sinensis were sequenced to determine the degree of interspecific sequence variation within the Hyrcanus Group. Consensus sequence of the 5.8S rDNA-ITS2-28S rDNA region from 3 individual An. pullus was completely identical to that from 3 individual An. yatsushiroensis. Examination of molecular data obtained from nuclear DNA and mitochondrial DNA as well as morphological observations in rearing experiments support synonymy of An. yatsushiroensis and An. pullus in Korea.

A DNA barcode library for Korean Chironomidae (Insecta: Diptera) and indexes for defining barcode gap.

Non-biting midges (Diptera: Chironomidae) are a diverse population that commonly causes respiratory allergies in humans. Chironomid larvae can be used to indicate freshwater pollution, but accurate identification on the basis of morphological characteristics is difficult. In this study, we constructed a mitochondrial cytochrome c oxidase subunit I (COI)-based DNA barcode library for Korean chironomids. This library consists of 211 specimens from 49 species, including adults and unidentified larvae. The interspecies and intraspecies COI sequence variations were analyzed. Sophisticated indexes were developed in order to properly evaluate indistinct barcode gaps that are created by insufficient sampling on both the interspecies and intraspecies levels and by variable mutation rates across taxa. In a variety of insect datasets, these indexes were useful for re-evaluating large barcode datasets and for defining COI barcode gaps. The COI-based DNA barcode library will provide a rapid and reliable tool for the molecular identification of Korean chironomid species. Furthermore, this reverse-taxonomic approach will be improved by the continuous addition of other speceis' sequences to the library.

Reemergence of the bedbug Cimex lectularius in Seoul, Korea.

A healthy 30-yr-old woman carrying an insect that had been caught in her living room visited the International Clinic at Severance Hospital, Seoul, in December 2007. The insect she brought was identified to be a nymph of a bedbug, Cimex lectularius, and her skin rashes looked typical bedbug's bites. Her apartment was investigated, and a dead body of a bedbug, cast skins, and hatched eggs were found in her rooms and neighbors' rooms in the same building. She was living in that apartment in Seoul for 9 months since she had moved from New Jersey, USA. We assume that the bedbugs were introduced from abroad, since there had been no report on bedbugs in Seoul for more than 2 decades at least. This is a report of a reemergence of the common bedbug, C. lectularius in Seoul, Korea.

Redestribution of Chironomus salinarius (Diptera: Chironomidae), nuisance midges that emerged in brackish water of Jinhae-man (Bay), Kyongsangnam-do, Korea.

Huge numbers of non-biting midges emerged from brackish water which were made at the harbor construction field in Jinhae City, Kyongsangnam-do, Korea in late summer in 2005, and caused a serious nuisance to villagers. The midges were collected and identified as Chironomus salinarius (Kieffer, 1921). Although this species was recorded in Korea for the first time in 1998, the morphological descriptions were so brief and simple. A full redescription is made with detailed illustrations for ecological and control workers of this nuisance midge.

Field trial on the control effect of fipronil bait against German cockroaches.

A field trial on the control effect of fipronil poison bait against German cockroaches (Blatella germanica) was carried out at different restaurant types in Sinchon, Seoul, Republic of Korea. Monitoring was performed applying food baited traps for 2 days per week. Reduction rates of German cockroaches by applying fipronil baits were 90.9% at Korean restaurants, 96.4% at Chinese restaurants, and 89.4% in beer hall kitchens after 4 weeks of the treatment. Overall average of the reduction rate was 93.9%. As the natural reduction rate at untreated restaurants was 11.5% after 4 weeks, a correction of the average reduction rate by applying the Abbot formula was 93.1%.

Effectiveness of education for control of house dust mites and cockroaches in Seoul, Korea.

We evaluated the efficacy of health education in reducing indoor arthropod allergens in Seoul. The mite control measures comprised the use of mite-proof mattress and pillow coverings, regular washing of potentially infested materials, maintenance of a low humidity, removal of carpets, and frequent vacuum cleaning. Cockroach control measures included trapping, application of insecticides, and protecting food. Of 201 homes enrolled in October 1999, 63 volunteers were included in a 2-year follow-up survey between April 2000 and January 2002. Before intervention, the density of mites/g of dust varied greatly; 27.1/g in childrenos bedding, 20/g in adult bedding, 7.2/g on the floors of childrenos bedrooms, 6.8/g in sofas, 5.9/g on the floors of adultos bedrooms, 3.9/g on living room floors, 3.7/g in carpets, and 1.9 mites/g on kitchen floors. The predominant mite species and house percentages infested were; Dermatophagoides farinae 93%, D. pteronyssinus 9%, and Tyrophagus putrescentiae 8%. Comparing 1999 and 2001 infestations, before and after 25 mo of education, mite abundance was reduced by 98%, from 23.7 to 0.57 mites/g of dust. In 1999, cockroaches were detected in 62% homes: 36% Blattella germanica and 35% Periplaneta spp., including 9% double infestations of B. germanica and P. americana. Following intervention, cockroach infestation rates decreased to 22% of houses in 2000 and 23% in 2001. We conclude that continuous and repetitive health education resulted in the effective control of domestic arthropods.

Studies on Anopheles sinensis, the vector species of vivax malaria in Korea.

Extensive previous studies on taxonomy, behavior/bionomics and control of Anopheles sinensis are reviewed and summarized. Recent molecular identification revealed that the population of An. sinensis complex includes An. sinensis, An. pullus, An. lesteri and at least two new species, and An. yatsushiroensis is synonmy of An. pullus. An. sinensis is the main vector species of vivax malaria in Korea. Larvae of An. sinensis breed in wide range of habitats which are naturally-made clean water, stagnant or flowing; main habitats include rice fields, ditches, streams, irrigation canals, marshes, ponds, ground pools, etc. Their host preferences are highly zoophilic. Human blood rate is very low (0.7-1.7%); nevertheless An. sinensis readily feeds on man when domestic animals are not found near by. They feed on hosts throughout the night from dusk to dawn with a peak period of 02:00-04:00 hours; they are slightly more exophagic (biting outdoors); much larger numbers come into the room when light is on. Main resting places are outdoors such as grasses, vegetable fields and rice fields. A mark-release-recapture study resulted that 37.1% was recaptured within 1 km, 29.4% at 1-3 km, 21.1% at 3-6 km, 10.3% at 6-9 km and 2.1% at 9-12 km distance. An. sinensis hibernate outdoors (mostly under part of dense grasses) during October-March. At the end of the hibernation period (March-April) they feed on cows at daytime. Until today any single measure to effectively control An. sinensis population has not been found. Indoor residual spray with a long-lasting insecticide can not reduce vector population densities, but shorten their life spans in some degree, so contributes to malaria control.

Immunoglobulin E binding reactivity of a recombinant allergen homologous to alpha-Tubulin from Tyrophagus putrescentiae.

Storage mites may cause allergic respiratory diseases in urban areas as well as pose an occupational hazard in rural areas. Characterization of storage mite allergens is important for the development of diagnostic and therapeutic agents against mite-associated allergic disorders. Here we report on the cloning and expression of alpha-tubulin from the storage mite (Tyrophagus putrescentiae). The deduced amino acid sequence of the alpha-tubulin from the storage mite showed as much as 97.3% identity to the alpha-tubulin sequences from other organisms. The highly conserved amino acid sequences of alpha-tubulins across different species of mites may indicate that cross-reactivity for this potential allergen exists. The frequency of immunoglobulin E reactivity of this recombinant protein is 29.3% in sera from storage mite-allergic subjects.

Immunoglobulin E reactivity of recombinant allergen Tyr p 13 from Tyrophagus putrescentiae homologous to fatty acid binding protein.

The storage mite, Tyrophagus putrescentiae, is one of the important causes of allergic disorders. Fifteen allergenic components were demonstrated in storage mite by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting, but only the group 2 allergen Tyr p 2 has been cloned and characterized. In this study, we attempted to identify and characterize new allergens from T. putrescentiae, which is a dominant species of storage mite in Korea. Expressed sequence tags were analyzed to identify possible storage mite allergens, and the cDNA sequence encoding a protein homologous to fatty acid binding protein, a mite group 13 allergen, was identified and named Tyr p 13. Its deduced amino acid sequence showed 61.1 to 85.3% identity with other mite group 13 allergens. The recombinant protein was expressed in Escherichia coli using a pET 28b vector system, and its allergenicity was investigated by enzyme-linked immunosorbent assay (ELISA). The recombinant allergen was detected in 5 of 78 (6.4%) T. putrescentiae-positive sera tested, and it inhibited 61.9% of immunoglobulin E binding to crude extract at an inhibitor concentration of 10 mug/ml by inhibition ELISA using serum from the patient who showed the strongest reaction by ELISA. In this study, a novel allergen was identified in T. putrescentiae. This allergen could be helpful for more-detailed characterizations of storage mite allergy.

Insecticide susceptibility tests on adults of Anopheles sinensis in Korea.

The authors carried out two series of field test to determine the basic lines of DDT and Dieldrin susceptibility of Anopheles sinensis at Andong(1961) and Yoju(1962), where malaria endemicity is relatively high in Korea. Tests were performed in accordance with the standard method established by the World Health Oraganization(1960). The results were summarized as follows: 1. The LC-50 of DDT for A. sinensis caught at Andong as 1.5 %, while for the same species in Yoju was 1.3 %. 2. The LC-50 of Dieldrin for A. sinensis caught at Andong was 0.075 %, while the LC-50 for the same species at Yoju was 0.07 %. These results therefore indicate Anopheles sinensis, as the malaria vector species in Korea, is susceptible to DDT and Dieldrin.

[Study on natural infection of Plasmodium vivax in Anopheles sinensis in Korea]

On epidemiological grounds, Anopheles sinensis has been suspected for many years to be the malaria vector in Korea. Of 7,517 dissections of A. sinensis, one specimen was found for the first time in Korea naturally infected with sporozoites in August 1962. Experimental infection of A. sinensis with Plasmodium vivax had been successfully conducted at earlier date.

Methods Of Sampling Population Of The Japanese Encephalitis Vector Mosquitoes In Korea: A Preliminary Report.

For the determination/confirmation of the vector species of Japanese encephalitis in Korea and for the study of their bionomics, a preliminary assessment of different collecting methods of sampling mosquito population was undertaken. Man-biting catches, cow-biting catches, pig-baited window-trap hut, light trap, dry ice trap and man-baited double net were employed. The advnntages and disadvantages of these methods are discussed. A pig-baited window-trap hut and cow-biting catches outdoors are considered the best ways of collecting large numbers of Culex tritaeniorhynchus summorosus, the most important vector of Japanese encephalitis, for virus isolation and insecticide susceptility testing. The latter method requires, however, more man-power. Light traps set in a pigsty or cowshed are the simplest and most convenient tools for studying tne mosquito population density and seasonal prevalence.

A human case of house dust mite Tarsonemus floricolus collected from sputum.

A 23-year-old medical student showed a positive reaction on a skin test for Paragonimus westermani, and two Tarsonemus floricolus mites were subsequently found by sputum examination and identified morphologically. Our report is the first human case of Tarsonemus floricolus in Korea.

Expression of tropomyosin from Blattella germanica as a recombinant non-fusion protein in Pichia pastoris and comparison of its IgE reactivity with its native counterpart.

Tropomyosins derived from invertebrates are well-known pan allergens. However, the allergenicities of recombinant tropomyosins are variable. Here, we undertook to compare the IgE-binding reactivities of native and recombinant German cockroach tropomyosins. Native tropomyosin was purified by ammonium sulfate fractionation, hydroxyapatite column chromatography, and electroelution, and recombinant tropomyosin was expressed in Pichia pastoris. The allergenicities of the native and recombinant tropomyosins were compared by ELISA inhibition analysis. Native German cockroach tropomyosin showed 18% IgE-binding reactivity to German cockroach sensitized sera. Recombinant tropomyosin was produced without fusion protein and its N-terminus was blocked like that of the native counterpart. The IgE-binding reactivity of the recombinant was found to be comparable to that of native tropomyosin over the concentration range 1-1000 ng/ml by ELISA inhibition testing. Recombinant German cockroach tropomyosin expressed in Pichia pastoris showed better allergenicity than that expressed in Escherichia coli. Other factors in addition to the structural differences of native and recombinant proteins may also influence the IgE reactivities of tropomyosins.

Analysis of amino acid sequence variations and immunoglobulin E-binding epitopes of German cockroach tropomyosin.

The allergenicities of tropomyosins from different organisms have been reported to vary. The cDNA encoding German cockroach tropomyosin (Bla g 7) was isolated, expressed, and characterized previously. In the present study, the amino acid sequence variations in German cockroach tropomyosin were analyzed in order to investigate its influence on allergenicity. We also undertook the identification of immunodominant peptides containing immunoglobulin E (IgE) epitopes which may facilitate the development of diagnostic and immunotherapeutic strategies based on the recombinant proteins. Two-dimensional gel electrophoresis and immunoblot analysis with mouse anti-recombinant German cockroach tropomyosin serum was performed to investigate the isoforms at the protein level. Reverse transcriptase PCR (RT-PCR) was applied to examine the sequence diversity. Eleven different variants of the deduced amino acid sequences were identified by RT-PCR. German cockroach tropomyosin has only minor sequence variations that did not seem to affect its allergenicity significantly. These results support the molecular basis underlying the cross-reactivities of arthropod tropomyosins. Recombinant fragments were also generated by PCR, and IgE-binding epitopes were assessed by enzyme-linked immunosorbent assay. Sera from seven patients revealed heterogeneous IgE-binding responses. This study demonstrates multiple IgE-binding epitope regions in a single molecule, suggesting that full-length tropomyosin should be used for the development of diagnostic and therapeutic reagents.