Displaying publications 1 - 20 of 39 in total

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  1. Adler PH, Takaoka H, Sofian-Azirun M, Low VL, Ya'cob Z, Chen CD, et al.
    PLoS One, 2016;11(10):e0163881.
    PMID: 27695048 DOI: 10.1371/journal.pone.0163881
    The increasing attention on Vietnam as a biodiversity hotspot prompted an investigation of the potential for cryptic diversity in black flies, a group well known elsewhere for its high frequency of isomorphic species. We analyzed the banding structure of the larval polytene chromosomes in the Simulium tuberosum species group to probe for diversity beyond the morphological level. Among 272 larvae, 88 different chromosomal rearrangements, primarily paracentric inversions, were discovered in addition to 25 already known in the basic sequences of the group in Asia. Chromosomal diversity in Vietnam far exceeds that known for the group in Thailand, with only about 5% of the rearrangements shared between the two countries. Fifteen cytoforms and nine morphoforms were revealed among six nominal species in Vietnam. Chromosomal evidence, combined with available molecular and morphological evidence, conservatively suggests that at least five of the cytoforms are valid species, two of which require formal names. The total chromosomal rearrangements and species (15) now known from the group in Vietnam far exceed those of any other area of comparable size in the world, supporting the country's status as a biodiversity hotspot. Phylogenetic inference based on uniquely shared, derived chromosomal rearrangements supports the clustering of cytoforms into two primary lineages, the Simulium tani complex and the Southeast Asian Simulium tuberosum subgroup. Some of these taxa could be threatened by habitat destruction, given their restricted geographical distributions and the expanding human population of Vietnam.
  2. Lau KW, Chen CD, Lee HL, Izzul AA, Asri-Isa M, Zulfadli M, et al.
    Trop Biomed, 2013 Mar;30(1):36-45.
    PMID: 23665706 MyJurnal
    The aim of the present study was to determine the vertical distribution and abundance of Aedes mosquitoes in multiple storey buildings in Selangor and Kuala Lumpur, Malaysia. Ovitrap surveillance was conducted for 4 continuous weeks in multiple storey buildings in 4 residential areas located in Selangor [Kg. Baiduri (KB)] and Kuala Lumpur [Student Hostel of University of Malaya (UM), Kg. Kerinchi (KK) and Hang Tuah (HT)]. The results implied that Aedes mosquitoes could be found from ground floor to highest floor of multiple storey buildings and data from different elevation did not show significant difference. Ovitrap index for UM, KB, HT and KK ranged from 0 - 29.17%, 0 - 55.56%, 8.33 - 83.33% and 0 - 91.17% respectively. Aedes aegypti and Aedes albopictus were found breeding in HT, KK and KB; while only Ae. albopictus was obtained from UM. The results indicate that the invasion of Aedes mosquitoes in high-rise apartments could facilitate the transmission of dengue virus and new approaches to vector control in this type of residential area should be developed.
  3. Amelia-Yap ZH, Sofian-Azirun M, Chen CD, Lau KW, Suana IW, Syahputra E, et al.
    J Med Entomol, 2019 06 27;56(4):953-958.
    PMID: 30942885 DOI: 10.1093/jme/tjz035
    Resistance to pyrethroid insecticides is widespread in Indonesian Aedes aegypti (Linnaeus), the primary vector of dengue viruses. This study aims to investigate the mutations in the voltage-gated sodium channel (Vgsc) conferring pyrethroid resistance against Ae. aegypti populations from Indonesia. Molecular genotyping of mutations using polymerase chain reaction assay and direct DNA sequencing were performed at positions 989 and 1,016 in IIS6 region, and 1,534 in IIIS6 region of the voltage-gated sodium channel (Vgsc) in nine populations of Indonesian Ae. aegypti. The V1016G and S989P genotyping identified the RR genotype to be predominant in six out of nine populations of Ae. aegypti, whereas the SS genotype occurred only in minority. Interestingly, co-occurrence of the V1016G and S989P mutations was detected in the aforementioned six populations with high frequency. Genotyping of F1534C showed all nine populations exhibited the SS genotype, with merely two individuals from a population were heterozygous (RS). Significant correlations were demonstrated between the allele frequencies of the V1016G mutation and the survivability rates as well as resistance ratios in pyrethroid adult bioassays. This signifies the V1016G can contribute more to the insensitivity of Vgsc than the F1534C. Homozygous 1016G mosquitoes were likelier to survive pyrethroid exposure. Identification of underlying mechanisms resulting in insecticide resistance is advantageous in developing effective mosquito control programs in Indonesia.
  4. Takaoka H, Sofian-Azirun M, Chen CD, Lau KW, Halim MRA, Low VL, et al.
    J Med Entomol, 2017 May 01;54(3):576-586.
    PMID: 27974360 DOI: 10.1093/jme/tjw208
    Two new species, Simulium (Gomphostilbia) sunapii and S. (G.) rangatense, are described based on adults, pupae, and mature larvae from Flores, in the eastern part of the Sunda Archipelago, Indonesia. Simulium (G.) sunapii sp. nov. is placed in the S. asakoae species-group, representing the easternmost geographical record for the group in this archipelago. It is characterized by a small number of male upper-eye large facets in eight or nine vertical columns and 12 horizontal rows. Simulium (G.) rangatense sp. nov. is placed in the S. ceylonicum species-group and is characterized by the pupal gill with six filaments. This new species, together with two related species of the S. ceylonicum species-group in Flores, suggests the species radiation of this species-group might have been accompanied by a reduction of the number of pupal gill filaments from eight to four through six. Taxonomic notes are provided to distinguish these two new species from related species.
  5. Takaoka H, Sofian-Azirun M, Chen CD, Lau KW, Halim MRA, Low VL, et al.
    Trop Biomed, 2018 Dec 01;35(4):951-974.
    PMID: 33601844
    Simulium (Gomphostilbia) dhangi sp. nov., S. (G.) sumbaense sp. nov. and S. (Nevermannia) wayani sp. nov. are described from the Lesser Sunda Archipelago, Indonesia. Simulium (G.) sumbaense sp. nov. is placed in the S. varicorne species-group and is characterized by the pupal gill with eight filaments arranged as (1+1+1+1+2)+2 from dorsal to ventral, while S. (G.) dhangi sp. nov., unplaced to group, is characterized by the pupal gill composed of two inflated trunks and four slender filaments all arising basally, and the short larval antenna as long as the stem of the labral fan. Simulium (N.) wayani sp. nov. belongs to the S. ruficorne species-group and is characterized by the female spermatheca with an unsclerotized neck, and pupal gill with four inflated filaments. The number of species of black flies from the archipelago increases from 19 to 22.
  6. Takaoka H, Sofian-Azirun M, Ya'cob Z, Chen CD, Lau KW, Pham XD
    Zootaxa, 2014;3866(4):555-71.
    PMID: 25283675 DOI: 10.11646/zootaxa.3866.4.6
    Three new species of black flies, Simulium (Nevermannia) langbiangense, S. (N.) phami, and S. (N.) bachmaense, are described on the basis of females, males, pupae and larvae collected in Vietnam. All three species are assigned to the Simulium feuerborni species-group of Simulium (Nevermannia). Simulium (N.) langbiangense sp. nov. is characterized by the female sensory vesicle with a large opening, and a short common basal stalk of the six pupal gill filaments, S. (N.) phami sp. nov. is most striking in having the pupal gill with five filaments, a character not reported in species of the S. feuerborni species-group, and S. (N.) bachmaense sp. nov. is characterized by the female genital fork with a triangular lobe-like projection pointed posteromedially on each arm, and the small larval postgenal cleft. This represents the first record of the S. feuerborni species-group from Vietnam.
  7. Takaoka H, Sofian-Azirun M, Ya'cob Z, Chen CD, Lau KW, Low VL, et al.
    Acta Trop, 2017 May;169:170-186.
    PMID: 28115156 DOI: 10.1016/j.actatropica.2017.01.016
    Surveys of pupae and larvae of black flies were carried out in Bali, Lombok, Sumbawa and Flores in the Lesser Sunda Archipelago, Indonesia, where 10 species were known. A total of 14 simuliid species including four new species and five new records of the genus Simulium were collected, bringing the number of species from the Lesser Sunda Archipelago to 19. They are classified into four subgenera: two in Nevermannia, nine in Gomphostilbia, seven in Simulium and one in Wallacellum. One of four new species, Simulium (Simulium) baliense, is described based on females, males, pupae and larvae from Bali and Lombok. This new species, which is placed in the Simulium striatum species-group of the subgenus Simulium, is closely related to S. (S.) argyrocinctum De Meijere from Java and Sumatra, but it is distinguished from the latter species by the smaller number of the male enlarged upper-eye facets and larval abdomen lacking dorsal pairs of conical protuberances. The distribution record of S. (S.) upikae Takaoka & Davies from Flores is corrected as that of S. (S.) eximium De Meijere. Some aberrant characters of the pupal gill filaments of S. (G.) atratum De Meijere, S. (G.) floresense Takaoka, Hadi & Sigit and S. (G.) sunapii Takaoka, Sofian-Azirun & Suana are illustrated. Characteristics of the fauna of black flies in this archipelago are briefly noted. Keys to all 19 species are provided for females, males, pupae and larvae.
  8. Takaoka H, Sofian-Azirun M, Ya'cob Z, Chen CD, Lau KW, Low VL, et al.
    Zootaxa, 2017 May 05;4261(1):1-165.
    PMID: 28609891 DOI: 10.11646/zootaxa.4261.1.1
    The biodiversity of black flies (Diptera: Simuliidae), which are biting insects of medical and veterinary importance, is strikingly high in Southeast Asian countries, such as Indonesia, Malaysia, Philippines and Thailand. In 2013, we began to explore the fauna of black flies in Vietnam, which has so far been poorly studied. In this monograph, the wealth of the biodiversity of black flies in Vietnam is also confirmed on the basis of the results of our recent investigations, though limited to five provinces in the country.      Morphotaxonomic studies of black flies obtained from Sapa, Lao Cai Province, northern Vietnam, in 2014 and Nghe An Province, northern Vietnam, in 2015, and reexaminations of black flies collected from Tam Dao, Vinh Phuc Province, northern Vietnam, in 2013, Thua Thien Hue Province, central Vietnam, in 2014, and Lam Dong Province, southern Vietnam, in 2014, were conducted. A total of 22 species are described as new, including one in the newly recorded subgenus Montisimulium Rubtsov, and three species are recognized as new records from Vietnam. This investigation brings the number of species of black flies known in Vietnam to 70, all of which are assigned to the genus Simulium Latreille, and are placed in four subgenera (25 in Gomphostilbia Enderlein, one in Montisimulium, seven in Nevermannia Enderlein, and 37 in Simulium Latreille s. str.). The numbers of species-groups recognized include seven in Gomphostilbia, three in Nevermannia and nine in Simulium, indicating a high diversity of putative phylogenetic lineages. New species include S. (G.) sanchayense sp. nov. (= the species formerly regarded as S. (G.) brinchangense Takaoka, Sofian-Azirun & Hashim), S. (S.) lowi sp. nov. (= the species formerly regarded as S. (S.) brevipar Takaoka & Davies), S. (S.) fuscicoxae sp. nov. [= the species formerly regarded as S. (S.) rufibasis Brunetti (in part)], S. (S.) suoivangense sp. nov. [= morphoform 'b' of the S. (S.) tani Takaoka & Davies (complex)]. Newly recorded species are S. (G.) parahiyangum Takaoka & Sigit, S. (N.) maeaiense Takaoka & Srisuka, and S. (S.) doipuiense Takaoka & Choochote (complex) [= the species formerly regarded as S. (S.) rufibasis Brunetti (in part)]. The substitute name, S. (S.) huense, is given for the species that was described under the name of S. (S.) cavum from southern Vietnam. A redescription of the female, male, pupa and larva of S. (G.) asakoae Takaoka & Davies is presented, and the female and larva of S. (G.) hongthaii Takaoka, Sofian-Azirun & Ya'cob are described for the first time. Keys to 10 subgenera in the Oriental Region and all 70 species recorded from Vietnam are provided for females, males, pupae and mature larvae.      As investigations extend nationwide in all the provinces in Vietnam, more new species and records are expected to be discovered. It is hoped that this monograph will be useful as a baseline taxonomic reference for future studies of black flies in Vietnam and neighbouring countries.
  9. Takaoka H, Sofian-Azirun M, Ya'cob Z, Chen CD, Lau KW, Pham XD
    Zootaxa, 2015;3961(1):1-96.
    PMID: 26249374 DOI: 10.11646/zootaxa.3961.1.1
    Surveys of pupae and larvae of black flies (Diptera: Simuliidae) were carried out in Thua Thien Hue Province of central Vietnam, and Lam Dong Province of southern Vietnam in 2014. A total of 26 species belonging to the genus Simulium were collected, consisting of eight known species, one newly recorded species, and 17 new species (of which three species of the subgenus Nevermannia were described in 2014). The remaining 14 new species (nine of the subgenus Gomphostilbia and five of the subgenus Simulium) are described here based on females, males, pupae and mature larvae. The total number of species of black flies in Vietnam is now 46. Keys to identify all 26 species recorded from the two provinces of Vietnam are given for females, males, pupae and mature larvae.
  10. Nurin-Zulkifli IM, Chen CD, Wan-Norafikah O, Lee HL, Faezah K, Izzul AA, et al.
    PMID: 26867376
    Surveillance of mosquitoes and their distribution in association with rainfall, relative humidity, and temperature were conducted in selected suburban and forested areas, namely, Sungai Penchala (Kuala Lumpur) and Taman Alam (Selangor) for 12 months. Armigeres kesseli was the most abundant species in Sungai Penchala while Aedes butleri was the most dominant species in Taman Alam. A positive correlation between mosquito distribution and rainfall was observed in selected mosquito species in Sungai Penchala (Armigeres kesseli, r = 0.75; Armigeres subalbatus, r = 0.62; and Aedes albopictus, r = 0.65) and Taman Alam (Armigeres sp, r = 0.59; Ae. butleri, r = 0.85; and Ae. albopictus, r = 0.62). However, no significant cor- relation was found either between selected mosquito species in both study areas and relative humidity or temperature. Results obtained suggested that vector control programs to be conducted based on temporal distribution of vectors in order to achieve beneficial outcomes with effective costing.
  11. Elia-Amira NMR, Chen CD, Low VL, Lau KW, Haziqah-Rashid A, Amelia-Yap ZH, et al.
    J Med Entomol, 2022 01 12;59(1):301-307.
    PMID: 34459477 DOI: 10.1093/jme/tjab146
    The efficacy of three groups of insect growth regulators, namely juvenile hormone mimics (methoprene and pyriproxyfen), chitin synthesis inhibitors (diflubenzuron and novaluron), and molting disruptor (cyromazine) was evaluated for the first time, against Aedes albopictus Skuse (Diptera: Culicidae) larvae from 14 districts in Sabah, Malaysia. The results showed that all field populations of Ae. albopictus were susceptible towards methoprene, pyriproxyfen, diflubenzuron, novaluron, and cyromazine, with resistance ratio values ranging from 0.50-0.90, 0.60-1.00, 0.67-1.17, 0.71-1.29, and 0.74-1.07, respectively. Overall, the efficacy assessment of insect growth regulators in this study showed promising outcomes and they could be further explored as an alternative to conventional insecticides.
  12. Takaoka H, Sofian-Azirun M, Chen CD, Lau KW, Halim MR, Low VL, et al.
    Zootaxa, 2017 Feb 21;4236(1):zootaxa.4236.1.8.
    PMID: 28264343 DOI: 10.11646/zootaxa.4236.1.8
    Simulium (Gomphostilbia) lemborense sp. nov. is described based on adults, pupae and mature larvae from Flores, in the eastern part of the Sunda Archipelago, Indonesia. This new species is placed in the Simulium batoense species-group of the subgenus Gomphostilbia Enderlein, representing the most eastern distribution record for the group. This new species is characterized by a narrow female frons and pupal gill with eight filaments, of which two filaments of the ventral pair are three to four times as long as the six other filaments. Taxonomic notes are provided to distinguish this new species from related species.
  13. Takaoka H, Sofian-Azirun M, Ya'cob Z, Chen CD, Lau KW, Fernandez K, et al.
    Zootaxa, 2015;3985(1):1-30.
    PMID: 26250021 DOI: 10.11646/zootaxa.3985.1.1
    Species of the Simulium (Simulium) melanopus species-group in Sabah are taxonomically revised by examining type specimens of S. (S.) crassimanum S. (S.) laterale, and S. (S.) nigripilosum, all described from females by Edwards in 1933, and newly collected samples from the vicinity of Mt. Kinabalu. The females of these three species are redescribed, and their males and pupae are described for the first time based on adults reared from pupae. Simulium (S.) liewi Takaoka, 2007 and S. (S.) kinabaluense Smart & Clifford, 1969 are synonymized with S. (S.) crassimanum and S. (S.) laterale, respectively. Simulium (S.) cheedhangi Takaoka, Sofian-Azirun & Ya'cob, 2015 is newly recorded from Sabah. Two new related species, S. (S.) lardizabalae and S. (S.) timpohonense, are described from males reared from pupae. Keys to identify eight species of the S. melanopus species-group in Sabah are provided for females, males, pupae and mature larvae.
  14. Amelia-Yap ZH, Sofian-Azirun M, Chen CD, Suana IW, Lau KW, Elia-Amira NMR, et al.
    J Med Entomol, 2019 04 16;56(3):811-816.
    PMID: 30715464 DOI: 10.1093/jme/tjz007
    The emergence of pyrethroid resistance in Aedes aegypti (L.) has limited the success of vector control. Early detection of resistance could assist authorities in deciding well-suited control strategies to minimize operational failures of Ae. aegypti control. Herein, biochemical analysis was performed to investigate the mechanisms involved in pyrethroid resistance in nine populations of Indonesian Ae. aegypti. Enzymes of adult Ae. aegypti such as esterases (ESTs), glutathione-S-transferases (GSTs), and mixed-function oxidases (MFOs) were characterized. Elevated MFO activity was correlated with resistance phenotype, indicating the role of this enzyme in contributing to pyrethroid resistance. No significant correlations were shown between pyrethroid resistance phenotype and α-ESTs, suggesting that marginally exceeded enzyme levels relative to the reference strain in some pyrethroid-susceptible populations were causative factor for insecticide resistance in other groups of insecticides. However, significant correlation was demonstrated between β-ESTs and pyrethroid resistance phenotype. The lowest enzyme levels in GSTs indicated that this enzyme was not predominant in causing pyrethroid resistance, despite the presence of significant correlations. Because metabolic detoxification fails to comprehensively explain the pyrethroid resistance in some Indonesian Ae. aegypti, additional mechanisms such as altered target sites in voltage-gated sodium channel may also contribute to the high pyrethroid resistance in Ae. aegypti.
  15. Azratul-Hizayu T, Chen CD, Lau KW, Azrizal-Wahid N, Tan TK, Lim YAL, et al.
    Parasitol Int, 2022 Feb;86:102483.
    PMID: 34678492 DOI: 10.1016/j.parint.2021.102483
    This study examines the biological efficacy of four mosquito mat vaporizers each containing different active ingredients: prallethrin with PBO, dimefluthrin, prallethrin, and d-allethrin. The glass chamber assay was used to evaluate their efficacy on Aedes albopictus (Skuse) (Diptera: Culicidae) from nine districts in Selangor, Malaysia. Aedes albopictus exhibited different knockdown rates, with 50% knockdown times, KT50, varying from 1.19 to 2.00 min, 1.22 to 2.20 min, 1.39 to 5.85 min, and 1.39 to 1.92 min for prallethrin with PBO, dimefluthrin, prallethrin and d-allethrin, respectively. In general, all populations of Ae. albopictus were completely knocked down after exposure to all active ingredients except Hulu Selangor population, which showed 96.00% knockdown against d-allethrin. On the contrary, mortality rates were observed from 84.00-100.00%, 84.00-100.00%, 90.67-100.00% and 90.67-100.00% in populations tested with prallethrin with PBO, dimefluthrin, prallethrin and d-allethrin, respectively. Moreover, significant correlations between mortality rates of prallethrin with PBO vs dimefluthrin (r = 0.836, P = 0.003), prallethrin with PBO vs prallethrin (r = 0.760, P = 0.011), and prallethrin vs d-allethrin (r = 0.694, P = 0.026) were also observed, suggesting cross-resistance among pyrethroids. d-allethrin was found to be high in insecticidal activity, followed by prallethrin, prallethrin with PBO, and dimefluthrin. In consistent with mortality due to insecticide exposure, elevated levels of enzyme activities were also demonstrated in Sabak Bernam, Hulu Selangor, Gombak, Petaling, Hulu Langat and Klang populations.
  16. Elia-Amira NMR, Chen CD, Lau KW, Lee HL, Low VL, Norma-Rashid Y, et al.
    J Econ Entomol, 2018 09 26;111(5):2488-2492.
    PMID: 29982497 DOI: 10.1093/jee/toy184
    The present study aims to investigate the susceptibility status of Aedes albopictus (Skuse) collected from residential areas in Sabah, Malaysia towards eight WHO-recommended dosages of larvicides representing the classes of organophosphates and organochlorines. Field and reference strains of Ae. albopictus larvae were bioassayed in accordance to WHO standard methods using diagnostic dosages of bromophos, malathion, fenthion, fenitrothion, temephos, chlorpyrifos, dichlorodiphenyltrichloroethane (DDT), and dieldrin. The results revealed that Ae. albopictus was resistant (mortality < 90%) towards malathion, temephos, and DDT. In addition, most of the Ae. albopictus strains exhibited a wide range of susceptibilities against bromophos, with mortality ranged from 49.33 to 93.33%. On the contrary, only dieldrin was able to induce 100% mortality against all strains of Ae. albopictus. Tolerance to fenitrothion, fenthion, and chlorpyrifos, with mortality ranging from 81.33 to 97.33%, was also observed in this study.
  17. Takaoka H, Sofian-Azirun M, Ya'cob Z, Chen CD, Lau KW, Pham HT
    Zootaxa, 2014;3838(3):347-66.
    PMID: 25081781 DOI: 10.11646/zootaxa.3838.3.6
    Four new species of black flies are described, and three others are reported as newly recorded, based on adults reared from pupae, pupae and larvae collected in and near Tam Dao National Park, Vinh Phuc Province, Vietnam. New species include Simulium (Gomphostilbia) hongthaii sp. nov., S. (G.) tamdaoense sp. nov. (both species placed in the asakoae species-group), S. (Simulium) taythienense sp. nov. and S. (S.) xuandai sp. nov. (the two latter species placed in the striatum species-group). Newly recorded species are S. (G.) brinchangense Takaoka, Sofian-Azirun & Hashim, S. (Nevermannia) aureohirtum Brunetti and S. (S.) brevipar Takaoka & Davies. These discoveries increase the number of species of black flies known in Vietnam from 21 to 28. 
  18. Haziqah-Rashid A, Chen CD, Lau KW, Low VL, Sofian-Azirun M, Suana IW, et al.
    J Med Entomol, 2019 02 25;56(2):514-518.
    PMID: 30462258 DOI: 10.1093/jme/tjy208
    This study was conducted to monitor the susceptibility status of Aedes aegypti (Linnaeus) larvae in the Sunda Islands of Indonesia against various organophosphates and organochlorines. Larval bioassay was performed in accordance with the World Health Organization standard protocol. Field-collected and reference strains of Ae. aegypti larvae were tested against diagnostic doses of eight larvicides belonging to organophosphates and organochlorines, namely bromophos (0.050 mg/liter), chlopyrifos (0.002 mg/liter), fenitrothion (0.020 mg/liter), fenthion (0.025 mg/liter), malathion (0.125 mg/liter), temephos (0.012 mg/liter), DDT (0.012 mg/liter), and dieldrin (0.025 mg/liter). Mortality rates of larvae were recorded at 24-h posttreatment. This study showed that Ae. aegypti larvae from Padang, Samarinda, Manggarai Barat, and South Central Timor were susceptible to both fenitrothion and dieldrin (mortality rates ≥ 98%). About 6 out of 10 field strains of Ae. aegypti larvae were resistant (<80% mortality rates) against fenthion, whereas Ae. aegypti larvae from Kuningan, Samarinda, Sumba, and South Central Timor exhibited some degrees of resistance (mortality rates 80-98%). All field-collected Ae. aegypti larvae were resistant against diagnostic doses of chlorpyrifos, malathion, temephos, and DDT with mortality rates ranging from 0 to 74.67%. Continued insecticide susceptibility studies are essential to identify the efficacy of insecticides for an improved dengue vector control and to delay the development of insecticide resistance.
  19. Chen CD, Lee HL, Chan CK, Ang CL, Azahari AH, Lau KW, et al.
    Trop Biomed, 2009 Dec;26(3):360-5.
    PMID: 20237452
    The bioefficacy of nine commercial formulations of temephos against Aedes aegypti, Aedes albopictus and Culex quinquefasciatus larvae were evaluated in the laboratory. WHO larval bioassay with operational dosage of temephos at 1 mg/L was performed. The larval mortality was recorded every 5 minutes until complete mortality was achieved. All formulations of temephos exhibited various toxicity level against Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus. Generally, larvae of Cx. quinquefasciatus was susceptible to all formulations of temephos, followed by Ae. aegypti and Ae. albopictus.
  20. Putt QY, Ya'cob Z, Adler PH, Chen CD, Hew YX, Izwan-Anas N, et al.
    Parasit Vectors, 2023 Aug 07;16(1):266.
    PMID: 37545007 DOI: 10.1186/s13071-023-05892-0
    BACKGROUND: Prompt and precise identification of black flies (Simuliidae) is crucial, given their biting behaviour and significant impact on human and animal health. To address the challenges presented by morphology and chromosomes in black fly taxonomy, along with the limited availability of molecular data pertaining to the black fly fauna in Vietnam, this study employed DNA-based approaches. Specifically, we used mitochondrial and nuclear-encoded genes to distinguish nominal species of black flies in Vietnam.

    METHODS: In this study, 135 mitochondrial cytochrome c oxidase subunit I (COI) sequences were established for 45 species in the genus Simulium in Vietnam, encompassing three subgenera (Gomphostilbia, Nevermannia, and Simulium), with 64 paratypes of 27 species and 16 topotypes of six species. Of these COI sequences, 71, representing 27 species, are reported for the first time.

    RESULTS: Combined with GenBank sequences of specimens from Malaysia, Myanmar, Thailand, and Vietnam, a total of 234 DNA barcodes of 53 nominal species resulted in a 71% success rate for species identification. Species from the non-monophyletic Simulium asakoae, S. feuerborni, S. multistriatum, S. striatum, S. tuberosum, and S. variegatum species groups were associated with ambiguous or incorrect identifications. Pairwise distances, phylogenetics, and species delimitation analyses revealed a high level of cryptic diversity, with discovery of 15 cryptic taxa. The current study also revealed the limited utility of a fast-evolving nuclear gene, big zinc finger (BZF), in discriminating closely related, morphologically similar nominal species of the S. asakoae species group.

    CONCLUSION: This study represents the first comprehensive molecular genetic analysis of the black fly fauna in Vietnam to our knowledge, providing a foundation for future research. DNA barcoding exhibits varying levels of differentiating efficiency across species groups but is valuable in the discovery of cryptic diversity.

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