Displaying publications 1 - 20 of 128 in total

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  1. Takaoka H, Sofian-Azirun M, Ya'cob Z, Hashim R, Otsuka Y
    J Med Entomol, 2014 May;51(3):517-28.
    PMID: 24897845
    Simulium (Gomphostilbia) leparense sp. nov. is described from females, males, and pupae collected from Peninsular Malaysia. This new species is assigned to the ceylonicum species-group of the subgenus Gomphostilbia, and is characterized by the female and male scuta covered with dark-brown short hairs, smaller number of male upper-eye facets, presence of shiny paired spots on the male abdominal segments 2-8, and absence of grapnel-shaped hooklets on the pupal abdominal segment 9. The male and pupa of S. capillatum Takaoka, which was originally described from larvae collected from Sarawak and Sabah, are described for the first time. Keys to identify all 32 species of the Simulium ceylonicum species-group including 27 species from other countries are provided for females, males, pupae, and mature larvae.
  2. Koou SY, Chong CS, Vythilingam I, Ng LC, Lee CY
    J Med Entomol, 2014 Jan;51(1):170-81.
    PMID: 24605467
    We report the first comprehensive insecticide susceptibility status ofAedes aegypti (L.) larvae from Singapore. The study indicated that Ae. aegypti is susceptible to temephos, although resistance (RR50 = 1.29-4.43-fold) couldbe developing. Of high concern is the detection of moderate to high resistance to permethrin (RR50 = 29-47-fold) and etofenprox (RR50 = 14-34-fold). Biolarvicide Bacillus thuringiensis israelensis (Bti) remains effective. The insecticide susceptibility profile of Ae. aegypti larvae was found to be homogenous among the different sites studied across the island city. The addition of synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based resistance, and a possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities suggested that detoxifying enzymes, mono-oxygenases, esterases, glutathione S-transferases, and altered acetylcholinesterases, generally did not contribute to the resistance observed. This study clearly demonstrated that pyrethroid resistance is widespread among Ae. aegypti population and lowered susceptibility to organophosphates is developing.
  3. Takaoka H, Sofian-Azirun M, Ya'Cob Z
    J Med Entomol, 2014 Jan;51(1):10-26.
    PMID: 24605448
    Two new blackfly species, Simulium (Gomphostilbia) azhari and Simulium (Gomphostilbia) johorense, are described based on adult females, males, pupae, and larvae collected from Peninsular Malaysia, and assigned to the parahiyangum subgroup and the duolongum subgroup of the batoense species group of the subgenus Comphostilbia, respectively. S. (G.) azhari sp. nov. is characterized in the female by the narrow frons, and in the male by the broad style and the ventral plate moderately produced ventrally. S. (G.) johorense sp. nov. is also remarkable in having the female subcosta lacking hairs or bearing a reduced number of hairs ranging from one to five. The pupae of both new species share a similar arrangement of the eight gill filaments (i.e., stalks of dorsal and middle triplets and ventral pair arising at the same level from the short common basal stalk), although relative lengths of filaments of the ventral pair to those of the dorsal and middle triplets are different between the two new species. Taxonomic notes are given to distinguish these new species from other related species. Keys to identify all 10 species of the batoense species group in Peninsular Malaysia are provided for adult females, males, pupae, and mature larvae.
  4. Takaoka H, Sofian-Azirun M, Hashim R
    J Med Entomol, 2013 Nov;50(6):1179-89.
    PMID: 24843921 DOI: 10.1603/me13036
    Simulium (Comphostilbia) izuae sp. nov. is described from female, male, pupal, and larval specimens collected from Cameron's Highlands, Peninsular Malaysia. This new species is placed in the asakoae species-group of the subgenus Gomphostilbia. The pupa of this new species is characterized by the gill with eight long filaments arranged as (3 + 3) + 2 filaments, of which the ventral pair of filaments is borne on a stalk that is always shorter than the common basal stalk. Taxonomic notes to distinguish this new species from five other Malaysian species and 12 other species of the asakoae species-group from other countries are given. Keys to identify all 18 species of the asakoae species-group are also provided for females, males, pupae, and mature larvae.
  5. Takaoka H, Sofian-Azirun M, Ya'cob Z
    J Med Entomol, 2013 Jul;50(4):701-8.
    PMID: 23926767
    ABSTRACT A new black fly species, Simulium (Comphostilbia) langkawiense, is described based on adult female, adult male, pupal, and larval specimens collected from Langkawi Island, Malaysia. This new species is similar in the configuration of the pupal gill to Simulium (Comphostilbia) gombakense Takaoka & Davies, 1995, originally described from Peninsular Malaysia, but differs from the latter species by the female genital fork with an anterolaterally angulated plate on each arm, the female tarsal claw tooth shorter than one half of the claw, the small number of male upper-eye large facets, the ventral plate with its ventral margin nearly flat in the middle when viewed posteriorly, and the inflated structure of the pupal gill with a less produced middle portion (width of middle inflated portion: length of inflated structure = 0.24). Taxonomic notes are also given to separate this new species from two other related species from Nepal and India. This represents another example of a unique species of black fly on one of the continental islands of Peninsular Malaysia.
  6. Abu Tahir N, Ahmad AH
    J Med Entomol, 2013 Sep;50(5):999-1002.
    PMID: 24180104
    Effects of laterite cover soil with different characteristics on survival of buried eggs, third instar larvae, and pupae of Musca domestica (L.) were studied experimentally. Soil treatments were loose dry soil, loose wet soil, compacted dry soil, and compacted wet soil (CWS). Eggs, third instar larvae, and pupae were buried under 30 cm of the different soil treatments and placed under field conditions until adults emerged. Rearing medium was provided for eggs and larvae, and control treatments of all stages were unburied immatures placed on soil surface. Egg and pupal survival to adult were significantly affected by the cover soil treatments, but third instars were more resilient. Wet soil treatments (loose wet soil and CWS) resulted in significantly reduced pupal survival, but increased survival of eggs. However, CWS significantly reduced adult emergence from buried eggs. Though emergence of house flies buried as eggs was significantly reduced, some were able to hatch and emerging first instar larvae developed to pupation. Although cover soil does not completely prevent fly emergence, it did limit development and emergence of buried house flies.
  7. Zuharah WF, Fadzly N, Lester PJ
    J Med Entomol, 2013 Sep;50(5):1014-24.
    PMID: 24180106
    The presence of predators can have dramatic consequences on prey communities, not only by the direct effects of consumption but also through sublethal effects. We investigated the survival rate and subsequent life history of the mosquito Culex pervigilans Bergroth under the influence of its major predator, the backswimmer Anisops wakefieldi White. We established a field experiment with various treatments: 1) control without predators, 2) free-roaming A. wakefieldi (with one, three, or nine A. wakefieldi per container), 3) caged A. wakefieldi (empty cage without predators, with one, three, or nine A. wakefieldi in each cage, and 4) A. wakefieldi cues (with cues concentrations of one, three, or nine A. wakefieldi). Cx. pervigilans eggs were then taken from these four experimental treatments and reared in two different laboratory conditions: 1) in clean water without any traces of predators, or 2) in water with the same treatments as in field. The survival rate of Cx. pervigilans was significantly reduced by the presence of predators or their cues. Even after a brief exposure to waters containing predators or residual cues, the subsequent progeny and the ontogeny of the remaining survivors were still affected. The percentage of eggs that hatched, and the resulting mosquito population, was influenced by the presence of predators or their cues. Our results suggest that sublethal effects may be carried by surviving individuals primarily through the effects of stress, perhaps by epigenetic mechanisms. We may expect to observe similar plasticity in species or populations with high temporal or spatial variability in predation.
  8. Bong LJ, Neoh KB, Jaal Z, Lee CY
    J Med Entomol, 2013 Sep;50(5):1003-13.
    PMID: 24180105
    The effects of four temperatures (15, 23.5, 28, and 35 degrees C) on the biological characteristics of the rove beetle Paederus fuscipes Curtis were studied, and its cuticular permeability also was measured. Specimens successfully developed to adulthood at each temperature tested, but development time of each preadult stage significantly decreased with increasing temperature. Both egg and L1 stages required at least 80 degree days above a threshold of approximately 10 degrees C to develop to the subsequent stage. The lengthy development time and high survival rate of preadults at 15 degrees C suggests that P. fuscipes can survive in a harsh environment during cold weather by hibernating, and this ability could allow preadults to succeed ecologically in temperate countries. However, adult longevity was short, and no fecundity was recorded at 15 degrees C. At 28 degrees C, P. fuscipes exhibited a high survival rate of adults, which had a longer life span and high fecundity; thus, the population had the highest intrinsic rate of increase (0.0788 +/- 0.0051 d(-1)) and the shortest mean generation time (48.57 +/- 1.43 d) at 28 degrees C. At this temperature, the population might reach a size that could facilitate invasion into residential areas. However, in the absence of a hygric environment, P. fuscipes was unable to survive despite favorable temperature. Unlike in adults and pupae, high cuticular permeability values were found in the larval stages. This indicates that larvae are highly susceptible to desiccation, and it explains why the distribution of P. fuscipes is restricted to moist habitats.
  9. Takaoka H, Srisuka W, Saeung A, Choochote W
    J Med Entomol, 2013 May;50(3):493-500.
    PMID: 23802443
    Simulium (Asiosimulium) furvum sp. nov. (Diptera: Simuliidae) is described from female, male, pupal, and larval specimens collected from Maewa National Park, Lampang Province, Thailand. This new species represents the fourth member of the subgenus Asiosimulium Takaoka & Chochoote, one of two small black fly subgenera endemic in the Oriental Region. It is characterized by a pear-shaped spermatheca in the female; a ventral plate in the male with a laterally compressed median keel directed ventrally and with a deep notch posteromedially, and aedeagal membrane with stout spines; and by 22 gill filaments in the pupa. Taxonomic notes are provided to separate this new species from three known species, Simulium (Asiosimulium) oblongum Takaoka & Choochote and Simulium (Asiosimulium) wanchaii Takaoka & Choochote, both from Thailand, and Simulium (Asiosimulium) suchitrae Takaoka from Nepal.
  10. Chan HH, Zairi J
    J Med Entomol, 2013 Mar;50(2):362-70.
    PMID: 23540125
    Insecticide resistance has become a serious issue in vector management programs. Information on insecticidal resistance and its associated mechanisms is important for successful insecticide resistance management. The selection of a colony of permethrin-resistant Aedes albopictus (Skuse) (Diptera: Culicidae), originating from Penang Island, Malaysia, yielded high larval-specific resistance to permethrin and cross-resistance to deltamethrin. Synergism assays showed that the major mechanism underlying this resistance involves cytochrome P450 monooxygenase. The resistance is autosomal, polygenically inherited and incompletely dominant (D = 0.26). Resistant larvae were reared under different conditions to assess the fitness costs. Under high larval density, larval development time of the resistant SGI strain was significantly longer than the susceptible VCRU strain. In both high- and low-density conditions SGI showed a lower rate of emergence and survival compared with the VCRU strain. Resistant larvae were more susceptible to predation by Toxorhynchites splendens (Wiedemann) (Diptera: Culicidae) larvae. The body size of SGI females reared under high-density conditions was larger compared with females of the susceptible strain. SGI females survived longer when starved than did VCRU females. The energy reserve upon eclosion was positively correlated with the size of the adults.
  11. Bong LJ, Neoh KB, Jaal Z, Lee CY
    J Med Entomol, 2012 May;49(3):451-60.
    PMID: 22679850
    The life history characteristics of the rove beetle Paederus fuscipes Curtis were studied under laboratory conditions using three field strains from Malaysia: Desa Wawasan (DW), Sri Pinang (SP), and Ampang Jajar (AJ). The total development time of immature stages differed significantly among the three strains, especially between DW (17.43 +/- 0.16 d), SP (18.60 +/- 0.19 d), and AJ (18.68 +/- 0.22 d). Adult females and males from DW also exhibited a shorter life span, although the difference among strains was not significant. In terms of fecundity, the numbers of eggs laid per female for DW, SP, and AJ were 121.28 +/- 15.98, 127.30 +/- 18.01, and 147.45 +/- 17.12, respectively. Additionally, because of the shorter life span in DW strain, two apparent peaks in age-stage specific fecundity were detected. The beetles compensated for their shorter life span by increasing their reproductive activity to sustain the progeny in the population. The intrinsic rates of increase (r) of P. fuscipes from DW, SP, and AJ were 0.0773 +/- 0.0046 d(-1), 0.0788 +/- 0.0051 d(-1), and 0.0873 +/- 0.0054 d(-1), respectively; and the net reproduction rates (R0) were 40.09 +/- 7.39 offspring, 45.29 +/- 8.74 offspring, and 42.34 +/- 8.25 offspring, respectively. The mean generation time of P. fuscipes from AJ was 43.08 +/- 1.07 d, which was significantly higher than that from DW (47.95 +/- 1.36 d) and SP (48.57 +/- 1.43 d). The total immature development time of P. fuscipes in this study was shorter than values reported in previous studies.
  12. Takaoka H, Sofian-Azirun M, Hashim R, Yacob Z, Chen CD
    J Med Entomol, 2012 Jul;49(4):803-12.
    PMID: 22897040
    Two new species of black flies, Simulium (Comphostilbia) terengganuense sp. nov. and Simulium (Gomphostilbia) aziruni sp. nov. (Diptera: Simuliidae), are described on the basis of reared adult, pupal, and larval specimens collected from Peninsular Malaysia. Both species are placed in the batoense species-group within the subgenus Gomphostilbia, one of two dominant subgenera of the genus Simulium in Peninsular Malaysia as well as in the Oriental Region. Strikingly, three morphological characteristics that rarely occur in the subgenus Gomphostilbia are found in these two new species: the very narrow female frons and the mushroom-like pupal terminal hooks in S. (G.) terengganuense sp. nov. and the pupal gill composed of an inflated horn-like structure and eight slender filaments in S. (G.) aziruni sp. nov.
  13. Ahmad A, Ahmad AH, Dieng H, Satho T, Ahmad H, Aziz AT, et al.
    J Med Entomol, 2011 Nov;48(6):1236-46.
    PMID: 22238885
    There is accumulating evidence that criminals wrap dead bodies in an attempt to conceal evidence. To anticipate the forensic implications of this phenomenon, we examined whether flies that are naturally associated with cadavers exhibit a delay in attendance or differ in species composition and abundance patterns because of the presence of wrapping material. Wrapped and exposed carcasses of dead monkeys placed in an oil plantation in Kedah, Malaysia, were visited over 50 d. On daily visits to each of the six carcasses, visiting adult flies were sampled using hand nets. Flies of 12 families were encountered. Calliphoridae (Chrysomya rufifacies Macquart and C. megacephala (F.) was the most prevalent family, followed by Sphaeroceridae. Some families tended to be more abundant in WRCs (i.e., Calliphoridae, Muscidae, and Phoridae), whereas others (i.e., Piophilidae, Sepsidae, and Psychodidae) were more prevalent in exposed carcasses. Wrapping delayed the arrival of all fly species encountered, with delays varying from 1 to 13 d depending on species. Wrapping did not affect species composition of flies, but prolong the occurrence of some species. The results of the current study emphasize the need to take into consideration the presence of a wrap when estimating postmortem interval.
  14. Tee HS, Saad AR, Lee CY
    J Med Entomol, 2011 Jul;48(4):797-805.
    PMID: 21845938
    The population size, age-class structure, and movement of the American cockroach, Periplaneta americana (L.) (Dictyoptera: Blattidae), were studied in three sewers in Penang, Malaysia, from September 2008 to October 2009. Eighteen to 20 glass-jar traps (two per manhole) were deployed for a 24-h period during each sampling occasion at each sewer. Adults and nymphs were active throughout the study period, with an average monthly trap catch of 57-97 adults and 79-99 nymphs. The mean proportions of adults and nymphs at the three sewers ranged from 0.47 to 0.57. Of the 2177 male and 2717 female cockroaches marked and released over the three sewers, recapture rates were 29.4-45.8 and 30.8-47.0%, respectively. The proportion of marked males and females did not differ significantly from the proportion of recaptured marked males and females. However, the mean number of times a marked female was recaptured was significantly greater than that of males. Of the 783 males and 1,030 females that were marked and recaptured, 19.4 and 24.7%, respectively, had moved between manholes, and significantly more females than males moved between manholes. Of the 406 recaptured marked adults that moved between manholes, 90.4% moved a distance of 2-20 m from their initial release site; one male moved 192 m, the longest distance recorded. Trap catch on each sampling occasion was positively correlated with daily mean temperature. The number of cockroach movements between manholes also was correlated with the mean daily minimum temperature.
  15. How YF, Lee CY
    J Med Entomol, 2010 Nov;47(6):987-95.
    PMID: 21175045
    The effect of temperature and humidity on the survival and water loss of the tropical bed bug, Cimex hemipterus (F.), was studied using two field-collected strains. Insects were exposed to temperatures ranging from 20 to 45 degrees C and relative humidities (RHs) of 33, 75, and 100%. C. hemipterus survived longest under the interaction of low temperature (20 degrees C) and high RH (75-100%). Survival and water loss were significantly affected (P < 0.01) by temperature and RH (either singly, or in interaction). Strain and sex significantly (P < 0.01) influenced bed bug survival, but not on water loss. Eggs, first instars, and adults reached their upper thermal lethal limit within 1 h at 39 degrees C, 44 degrees C, and 46 degrees C, respectively. The survival and water loss profiles showed that starved C. hemipterus started to die after losing 35-45% of their body weights.
  16. How YF, Lee CY
    J Med Entomol, 2010 May;47(3):305-12.
    PMID: 20496576
    This study examined the effects of different life stages (first, second, third, fourth, and five instars; adult females and adult males) and feeding regimes (starved and blood fed) on the active movement activity of the tropical bed bug, Cimex hemipterus (F.), under mixed-stage conditions. We used an extended arena made from Tygon tube coils and observed the movement frequency and movement distance at selected time intervals up to 120 h. The fifth instars and adult males and females showed significantly (P < 0.01) greater movement frequency compared with the other stages. The first and second instars showed limited movement (< 8 m) over the experimental period. Starved bed bugs showed greater movement frequency compared with blood-fed bed bugs, with the exception of adult females. Blood-fed adult females exhibited significantly (P < 0.01) greater movement frequency and distance compared with starved females. Blood-fed females moved up to 42.3 m over 120 h. Regression analysis between movement distance of the fifth instars and adults and the time intervals revealed a positive relationship (r2 = 0.6583; P < 0.01), suggesting that delays in bed bug control efforts will increase the risk of the greater infestation. During bed bug inspection, the presence of only late instars and adults in premises would indicate a new infestation, whereas an established infestation likely would consist of mixed stages.
  17. Foley DH, Rueda LM, Wilkerson RC
    J Med Entomol, 2007 Jul;44(4):554-67.
    PMID: 17695008
    To advance our limited knowledge of global mosquito biogeography, we analyzed country occurrence records from the Systematic Catalog of the Culicidae (http://www.mosquitocatalog. org/main.asp), and we present world maps of species richness and endemism. A latitudinal biodiversity gradient was observed, with species richness increasing toward the equator. A linear log-log species (y)-area (x) relationship (SAR) was found that we used to compare observed and expected species densities for each country. Brazil, Indonesia, Malaysia, and Thailand had the highest numbers of species, and Brazil also had the highest taxonomic output and number of type locations. Brazil, Australia, the Philippines, and Indonesia had the highest numbers of endemic species, but excluding small island countries, Panama, French Guiana, Malaysia, and Costa Rica had the highest densities of total species and endemic species. Globally, 50% of mosquito species are endemic. Island countries had higher total number of species and higher number of endemic species than mainland countries of similar size, but the slope of the SAR was similar for island and mainland countries. Islands also had higher numbers of publications and type locations, possibly due to greater sampling effort and/or species endemism on islands. The taxonomic output was lowest for some countries in Africa and the Middle East. A consideration of country estimates of past sampling effort and species richness and endemism is proposed to guide mosquito biodiversity surveys. For species groups, we show that the number of species of Anopheles subgenus Anopheles varies with those of subgenus Cellia in a consistent manner between countries depending on the region. This pattern is discussed in relation to hypotheses about the historical biogeography and ecology of this medically important genus. Spatial analysis of country species records offers new insight into global patterns of mosquito biodiversity and survey history.
  18. Takaoka H, Sofian-Azirun M, Ya'cob Z
    J Med Entomol, 2012 Nov;49(6):1198-205.
    PMID: 23270147
    Simulium (Simulium) kisapense sp. nov. is described on the basis of reared adult, pupal, and larval specimens collected from Langkawi Island, Peninsular Malaysia, and placed in the multi-striatum species-group in the subgenus Simulium. This new species is characterized by the bare basal section of the female radial vein, the male ventral plate with setae, the eight pupal gill filaments divergent at an angle of >90 degrees, and the shoe-shaped cocoon with small lateral window(s). Taxonomic notes are given to separate this new species from S. (S.) hirtinervis Edwards and S. (S.) malayense Takaoka and Davies, both from Peninsular Malaysia, and several other known species from Bhutan, India, Nepal, and Thailand.
  19. Low VL, Chen CD, Lee HL, Lim PE, Leong CS, Sofian-Azirun M
    J Med Entomol, 2013 Jan;50(1):103-11.
    PMID: 23427658
    A nationwide investigation was carried out to determine the current susceptibility status of Culex quinquefasciatus Say populations against four active ingredients representing four major insecticide classes: DDT, propoxur, malathion, and permethrin. Across 14 study sites, both larval and adult bioassays exhibited dissimilar trends in susceptibility. A correlation between propoxur and malathion resistance and between propoxur and permethrin resistance in larval bioassays was found. The results obtained from this study provide baseline information for vector control programs conducted by local authorities. The susceptibility status of this mosquito should be monitored from time to time to ensure the effectiveness of current vector control operations in Malaysia.
  20. Ahamad M, Ibrahim H, Bujang MK, Sah SA, Mohamad N, Nor SM, et al.
    J Med Entomol, 2013 Jan;50(1):140-6.
    PMID: 23427663
    A comprehensive 8-yr survey of acarine ectoparasites (ticks and mites) of bats was carried out in 18 localities from 2002 to 2009. Most of the surveys were conducted during 14 national biodiversity scientific expeditions throughout Malaysia. The objective was to identify acarines of known public health importance from bats and thus determine whether there is any potential public health risk in Malaysia. Trapping of bats was conducted using Harp traps and Mist nets. In total, 1,579 individuals comprising of 6 families and 52 species of bats were examined alive. In general, 25.6% of the bats were infested with acarines. Infestation rates of ticks, mesostigmatid mites, and chiggers on bats examined were 0.4, 10.4, and 14.7%, respectively. Their prevalence and mean intensity were tabulated. Genera of ticks extracted were Amblyomma, Dermacentor, Ixodes, and Ornithodoros. Of these genera, only two species can be identified to species level and they are Amblyomma cordiferum and Ixodes simplex. In total, 8 genera and 15 species of mesostigmatid mites were found; the species were Ancystropus eonycteris, Ancystropus zeleborii, Echinonysus nasutus, Laelaps aingworthae, Laelaps nuttalli, Laelaps sanguisugus, Laelaps sculpturatus, Longolaelaps longulus, Longolaelaps whartonii, Meristaspis lateralis, Meristaspis macroglossi, Paraperiglischrus rhinolophinus, Spinturnix acuminatus, Spinturnix americanus, and Spinturnix bakeri. Chiggers on bats were represented by 12 genera and 6 species; the species identified were Gahrliepia fletcheri, Riedlinia lipoxena, Trombigastia cadei, Walchiella impar, Walchiella oudemansi, and Whartonia caobangensis. The study produced an up-to-date list of acarine ectoparasites of bats in Malaysia where a total of 38 genera and 47 species of acarines were listed. Findings of the study demonstrated that 5 genera and 1 species of acarines that may pose potential health risks, can be found on bats.
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