Displaying publications 21 - 40 of 46 in total

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  1. Fulltext Insecticide susceptibility and resistance development in malathion selected Aedes albopictus (Skuse)
    Selvi S, Edah MA, Nazni WA, Lee HL, Tyagi BK, Sofian-Azirun M, et al.
    Trop Biomed, 2010 Dec;27(3):534-50.
    PMID: 21399596 MyJurnal
    Aedes albopictus was bioassayed to determine resistance development to malathion (OP). Two methods were applied, including WHO larval bioassay to determine the susceptibility to lethal concentration (LC), and adult bioassay to determine lethal time (LT). Larvae from colonies that had undergone selection pressure with malathion to yield 50% mortality were further subjected to selection for subsequent 10 generations. Selection of Ae. albopictus with malathion could relatively induce a consistent resistance ratio of 1.0 throughout 10 generations. It was noted that Ae. albopictus larvae showed less susceptibility to malathion compared to adults. The susceptibility test of adult mosquitoes to diagnostic dosage of 5.0% malathion-impregnated paper showed a variety of susceptibility to malathion when compared to the susceptible strain. Bioassay results indicated that the LT50 values of malathion-selected Ae. albopictus ranged between 11.5 - 58.8 minutes for ten consecutive generations. Biochemical enzyme studies indicated that there was a significant difference (p < 0.05) in esterase level in malathion-selected mosquitoes compared to non-selected control. Electrophoretic patterns of non-specific esterases at different life stages in malathion-selected Ae. albopictus suggested that non-specific esterases do not play a role in resistance of malathion-selected Ae. albopictus.
    Matched MeSH terms: Malathion/pharmacology*
  2. Fulltext Characterization on malathion and permethrin resistance by bioassays and the variation of esterase activity with the life stages of the mosquito Culex quinquefasciatus
    Selvi S, Edah MA, Nazni WA, Lee HL, Azahari AH
    Trop Biomed, 2007 Jun;24(1):63-75.
    PMID: 17568379 MyJurnal
    Larvae and adults of Culex quinquefasciatus were used for the test undertaken for malathion resistant strain (F61 - F65) and permethrin resistant strain (F54 - F58). The results showed that the LC50 for both malathion (F61 - F65) and permethrin (F54 - F58) resistant Cx. quinquefasciatus increased steadily throughout the subsequent five generations, indicating a marked development of resistance. The adult female malathion resistant strain have developed a high resistance level to malathion diagnostic dosage with a resistance ratio of 9.3 to 17.9 folds of resistance compared with the susceptible Cx. quinquefasciatus. Permethrin resistance ratio remained as 1.0 folds of resistance at every generation. It was obvious that malathion resistance developed at a higher rate in adult females compared to permethrin. Enzyme-based metabolic mechanisms of insecticide resistance were investigated based on the biochemical assay principle. From the results obtained obviously shows that there is a significant difference (p < 0.05) in esterase level in both malathion and permethrin selected strains. Female malathion selected strain has the higher level of esterase activity compared to the female permethrin selected strain at (0.8 to 1.04) alpha-Na micromol/min/mg protein versus (0.15 to 0.24) alpha-Na micromol/min/mg protein respectively. This indicated increased level of non-specific esterase is playing an important role in resistance mechanism in female malathion selected strain. Permethrin selected strain exhibited non-specific esterase activity at a very low level throughout the different life stages compared to malathion selected strain. This study suggests that life stages play a predominant role in conferring malathion and permethrin resistance in Cx. quinquefasciatus.
    Matched MeSH terms: Malathion/pharmacology*
  3. Fulltext Determination of homozygous susceptible strain in Culex quinquefasciatus (Say), using single raft sib-selection method
    Hidayati H, Nazni WA, Mohd SA
    Trop Biomed, 2008 Apr;25(1):75-9.
    PMID: 18600207 MyJurnal
    The standard laboratory strain was found to be heterozygous for susceptibility. Hence, an attempt was made to obtain a homozygous susceptible strain in Culex quinquefasciatus (Say) using single raft sib-selection method. Lab-bred females of Cx. quinquefasciatus from insectariums, Unit of Medical Entomology were used in the experiment. After blood feeding Cx. quinquefasciatus mosquitoes laid eggs in raft form, ten rafts selected randomly for the test. Each egg raft was introduced into a plastic tray from number one to number ten. Twenty-five third stage larvae from each tray were exposed to 17.5 microl from 500mg/l malathion in a paper cup label number 1 to number ten. In the bioassay, which had 100% mortality, the respective larva in that particular tray was bred to adult stage for the following generation. Less than 7days old female mosquitoes that emerged from F(0) were used in the test. The F(0) and the subsequent adult and larval stage generations were subjected to adult and larval bioassay. After selection for about 10 generations, a homozygous susceptible strain in Cx. quinquefasciatus was obtained.
    Matched MeSH terms: Malathion/pharmacology
  4. Fulltext Adult and larval insecticide susceptibility status of Culex quinquefasciatus (Say) mosquitoes in Kuala Lumpur Malaysia
    Nazni WA, Lee HL, Azahari AH
    Trop Biomed, 2005 Jun;22(1):63-8.
    PMID: 16880755 MyJurnal
    The susceptibility of Culex quinquefasciatus to chemical insecticides in two field sites in Kuala Lumpur was evaluated using the WHO standard susceptibility test. Less then 7 days old female mosquitos, reared from wild caught females were exposed to discriminating dosages of insecticides at recommended exposure periods. The larval bioassay were conducted using the multiple concentrations and the LC50 value was determined. The results indicated that cyfluthrin is the most effective among all the insecticides tested with LT50 value of 29.95 min and 28.59 min, for the strain from Ampang Hill and Pantai Dalam, respectively. It was surprisingly to note that both these field strains showed 0% mortality when tested against malathion and DDT. The LC50 value indicated that both strains were highly resistant to malathion with resistance ratio of 17,988 folds and 14,053 folds, respectively. This concludes that resistance at larval stages is extremely high compared to adult stages.
    Matched MeSH terms: Malathion/pharmacology
  5. Fulltext Insecticide resistance development in Culex quinquefasciatus (Say), Aedes aegypti (L.) and Aedes albopictus (Skuse) larvae against malathion, permethrin and temephos
    Hamdan H, Sofian-Azirun M, Nazni W, Lee HL
    Trop Biomed, 2005 Jun;22(1):45-52.
    PMID: 16880753
    Laboratory-bred females of Culex quinquefasciatus, Aedes aegypti and Aedes albopictus from the insectarium, Unit of Medical Entomology, Institute for Medical Research were used in the experiment. The late third stage of the F0 larvae which survived the high selection pressure of malathion, permethrin and temephos were reared and colonies were established from adults that emerged. Cx. quinquefasciatus larvae were subjected to selection by malathion and permethrin for 40 generations, Ae. aegypti larvae to malathion, permethrin and temephos for 32 generations and Ae. albopictus larvae were selected against malathion and permethrin for 32 generations and 20 generations against temephos. The rate of resistance development was measured by LC50 value. Cx. quinquefasciatus larvae developed higher resistance to malathion and permethrin compared to Ae. aegypti and Ae. albopictus. On the whole, permethrin resistance developed at a faster rate than malathion and temephos.
    Matched MeSH terms: Malathion/pharmacology
  6. Fulltext Resistance development and insecticide susceptibility in Culex quinquefasciatus against selection pressure of malathion and permethrin and its relationship to cross-resistance towards propoxur
    Selvi S, Endah MA, Nazni WA, Lee HL, Azahari AH
    Trop Biomed, 2005 Dec;22(2):103-13.
    PMID: 16883275
    To determine resistance level and characterize malathion and permethrin resistance in Culex quinquefasciatus, two methods were used namely: WHO procedures of larval bioassay to determine the susceptibility of lethal concentration (LC) and adult bioassay to determine the lethal time (LT) which are resistant to malathion and permethrin. These mosquito strains were bred in the Insectarium, Division of Medical Entomology, IMR. Thousands of late fourth instar larvae which survived the selection pressure to yield 50% mortality of malathion and permethrin were reared and colonies were established from adults that emerged. Larvae from these colonies were then subjected to the subsequent 10 generations in the test undertaken for malathion resistant strain (F61 - F70) and permethrin resistant strain (F54 - F63). Selection pressure at 50% - 70% mortality level was applied to the larvae of each successive generation. The rate of resistance development and resistance ratio (RR) were calculated by LC5 0 for larval bioassay and LT50 value for adult bioassay. The lab bred Cx. quinquefasciatus was used as a susceptible strain for comparison purpose. The adult bioassay test was carried out by using diagnostic dosages of malathion 5.0%, permethrin 0.75% and with propoxur 0.1%. All bioassay results were subjected to probit analysis. The results showed that LC5 0 for both malathion (F61 - F70) and permethrin (F54 - F63) resistant Cx. quinquefasciatus increased steadily to the subsequent 10 generations indicating a marked development of resistance. The adult female malathion resistant strain have developed high resistance level to malathion diagnostic dosage with resistance ratio 9.3 to 9.6 folds of resistance. Permethrin resistance ratio remained as 1.0 folds of resistance at every generation. It was obvious that malathion resistance developing at a higher rate in adult females compared to permethrin. Female adults exposed to 2 hours of exposure period for propoxur 0.1% showed presence of cross-resistance among the both strains of mosquitoes towards propoxur and it was indicated by 70%-100% mortality at 24 hours post-recovery period.
    Matched MeSH terms: Malathion/pharmacology*
  7. Field evaluation of cyfluthrin and malathion 96 TG ULV spraying at high-rise flats on dengue vectors in Malaysia
    Sulaiman S, Pawanchee ZA, Othman HF, Jamal J, Wahab A, Sohadi AR, et al.
    J Vector Ecol, 1998 Jun;23(1):69-73.
    PMID: 9673932
    Cyfluthrin (Solfac ULO15) and malathion 96 TG were evaluated against sentinel sugar-fed adults and 4th-instar larvae of Aedes aegypti at high-rise flats in Malaysia by ULV spraying. The impact of both insecticides on field populations of Aedes spp. (Ae. aegypti and Ae. albopictus) larvae were monitored weekly using containers. Both cyfluthrin and malathion 96 TG showed adulticidal effects but cyfluthrin showed more significant larvicidal effect than malathion 96 TG (P < 0.05).
    Matched MeSH terms: Malathion/administration & dosage*
  8. Fulltext Effect of sublethal dosages of malathion on the oral susceptibility of Aedes aegypti to dengue-2 virus infection
    Lee HL, Argubano RA, Ahmad R
    Southeast Asian J Trop Med Public Health, 1997 Sep;28(3):664-5.
    PMID: 9561626
    Matched MeSH terms: Malathion*
  9. Insecticide susceptibility studies of three cryptic species of the Anopheles balabacensis complex
    Hii JL
    Southeast Asian J Trop Med Public Health, 1984 Mar;15(1):104-11.
    PMID: 6740370
    Susceptibilities of two colonies of the taxon An. dirus (one from Perlis and from Thailand) and one colony of An. balabacensis from Sabah to DDT, dieldrin, malathion, fenitrothion and propoxur were determined. DDT and fenitrothion tolerance was found in An. dirus species B and An. balabacensis. No resistant strain was isolated as the two colonies were not either homozygous or nearly so for resistance. Field testing of the susceptibility of the adults of An. balabacensis to DDT was carried out between 1957 to 1976. The results indicated a progressive rise in the LC50 levels greater than 1% in almost all instance. The variation in the number of sprays applied in some districts have resulted in varying sensitivities. Association between the changes in levels of DDT susceptibility and exophilic habit of An. balabacensis has been observed but needs further confirmation. The significance of these findings and the difficulties in distinguishing tolerant from truly resistant individuals are discussed in relation to accurate species identification.
    Matched MeSH terms: Malathion/pharmacology
  10. Fulltext Rate of resistance development in wild Culex quinquefasciatus (Say) selected by malathion and permethrin
    Nazni WA, Lee HL, Sa'diyah I
    Southeast Asian J Trop Med Public Health, 1998 Dec;29(4):849-55.
    PMID: 10772575
    Wild caught female Culex quinquefasciatus (Say) from Kuala Lumpur were blood fed and reared in the insectarium. The late third stage of the F1 larvae which survived the high selection pressure of malathion and permethrin were reared and colonies were established from adults that emerged. Larvae from these colonies were then subjected in the subsequent 9 generations to higher selection pressure. The rate of resistance development were measured by LC50 value of larval bioassay, LT50 value of adult bioassay and the frequency of the elevated esterase levels. In another set of experiments using the same batch of Culex mosquitos, the larvae were not exposed to any insecticides and the decrease in resistance rate was monitored in each subsequent 9 generations by using similar methods. The heterozygous standard laboratory strain was selected for susceptibility using the single raft sib-selection method. The result showed that the field collected F1 generation was 96.0 and 6.3 fold more resistant to malathion and permethrin, respectively. After selection for about 9 generations the resistance ratio to malathion and permethrin was 6.2 and 767.3 fold more compared to the LC50 values of F1 generations, respectively. Esterase in F1 larvae was 6.0 fold more than the standard laboratory strain.
    Matched MeSH terms: Malathion/pharmacology*
  11. Fulltext Monitoring resistance gene frequencies in Malaysian Culex quinquefasciatus Say adults using rapid non-specific esterase enzyme microassays
    Lee HL, Tadano T
    Southeast Asian J Trop Med Public Health, 1994 Jun;25(2):371-3.
    PMID: 7855659
    The ability to identify the occurrence of different resistance genotypes in field populations of mosquito is considered important for the purpose of optimising chemical control operations. The recent development of rapid microassays of enzymes responsible for resistance has provided a means for rapidly assessing the genetic background of target mosquito populations. This concept is the topic of investigation in this study. Non-specific esterase activity, which is responsible for the resistance to organophosphates in Malaysian Culex quinquefasciatus Say adults, was determined in 3 field populations from Kuala Lumpur City using rapid enzyme assay. The optical density results were used to estimate the genotypic frequencies of the populations. Subsequently, time-dependent changes in the various frequencies were determined. Such techniques allowed rapid assessment of resistance genotypes for decision-making and its possible use in insect control merits further investigation.
    Matched MeSH terms: Malathion/antagonists & inhibitors*
  12. Fulltext Determination of insecticide susceptibility in Culex quinquefasciatus Say adults by rapid enzyme microassays
    Lee HL, Abimbola O, Singh KI
    Southeast Asian J Trop Med Public Health, 1992 Sep;23(3):458-63.
    PMID: 1488701
    Rapid enzyme microassays for the detection of resistance due to organophosphate and carbamate in individual field-collected strains of Culex quinquefasciatus adults were conducted. These tests allowed accurate differentiation by eye, on the basis of color changes of susceptible and resistant individuals. Two separate tests were conducted for the biochemical assays. In the insensitive acetylcholinesterase (AChE) test, acetylthiocholine iodide (ACTH) and 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) were used as substrate and coupling agent respectively. The resulting yellow chromophore indicated AChE activity. Test results showed that the color intensity decreased as increasing concentrations of propoxur were added, thereby confirming the susceptibility of the enzyme to inhibitor. Assay of non-specific esterase however, indicated elevated levels which were correlated with degree of malathion resistance. Electrophoretic data revealed the presence of 2 esterase bands in all strains. It was concluded that such a pattern was not contributory to malathion resistance in adults.
    Matched MeSH terms: Malathion*
  13. Toxicological studies of four insecticides against Musca domestica L
    Yoke OP, Sudderuddin KI
    Southeast Asian J Trop Med Public Health, 1975 Dec;6(4):525-31.
    PMID: 818717
    Toxicological studies of four insecticides (malathion, carbaryl, bioresmethrin, and GH 74) against Musca domestica vicinia (Ampang strain) were undertaken with particular reference to age, sex and posttreatment temperature. It was found that bioresmethrin and GH 74, both with a negative temperature coefficient, have great potential for use against houseflies. In vitro inhibitory studies of head and body esterases showed that unlike malathion and carbaryl, bioresmethrin had only negligible effect on these enzymes. The possibilities of using bioresmethrin and GH 74 for controlling the housefly problem in the Cameron Highlands, West Malaysia are discussed.
    Matched MeSH terms: Malathion/pharmacology
  14. Fulltext Insecticide use for malaria control in Central Java, Indonesia: a review
    Bang YH, Arwati S, Gandahusada S
    Med J Malaysia, 1982 Dec;37(4):308-15.
    PMID: 6762494
    DDT indoor residual sprayings in the Province of Central Java, Indonesia, for the past 28 years are reoieuied in terms ofAnopheles aconitus resistance to DDT and incidences of malaria. DDT resistance by An. aconitus has continued to increase and spread since its first detection in Central Java in 1962. In most areas malaria transmission is perennial, which appears to be not interrupted by DDT residual spraying of inner walls because of DDT resistance. In searching for alternatives to DDT, fenitrothion was the most effective residual compound among five insecticides tested in village scale trials, giving control for about 13 weeks at 2 g/m2. Because the target species rests largely on the lower portions of walls, when applied at 2 g/m2 to only one horizontal swath between 10 and 85 cm from the ground, this compound was effective for over two months, about one-third less than that found in full coverage applications. For a single application this selective method reduced the amount of insecticide by 65 percent and manpower by 43 percent, and three applications, to compensate for less residual effectiveness, will reduce insecticide use by about 50 percent and manpower by 15 percent, compared to two applications with full coverage. Further field investigations on application of insecticides and the ecology of the DDT-resistant vector continue to be needed in Central Java to reduce further the cost of residual sprayings in malaria control programmes. This review also suggests the possibility of other selective spraying methods and anti-vector methods applicable at the village level by the community.
    Matched MeSH terms: Malathion
  15. Fulltext Organochlorines and organophosphates susceptibility of Aedes albopictus Skuse larvae from agricultural and non-agricultural localities in Peninsular Malaysia
    Wan-Norafikah O, Chen CD, Sofian-Azirun M
    Saudi J Biol Sci, 2021 Jan;28(1):1010-1016.
    PMID: 33424394 DOI: 10.1016/j.sjbs.2020.11.040
    Aedes albopictus larvae obtained from different types of agricultural and non-agricultural localities in Peninsular Malaysia were subjected to several larvicides at World Health Organization (WHO) recommended dosages. Upon 24 h of WHO larval bioassay using two organochlorines and six organophosphates, high resistance against dichlorodiphenyltrichloroethane (DDT), temephos, chlorpyrifos and bromophos were demonstrated among all larval populations. Aedes albopictus larvae from both paddy growing areas (92.33% mortality) and rubber estates (97.00% mortality) were moderately resistant to dieldrin while only Ae. albopictus larvae from dengue prone residential areas (89.00% mortality) showed high resistance against dieldrin. All Ae. albopictus larval populations also developed either incipient or high resistance to both malathion (33.67%-95.33% mortality) and fenitrothion (73.00%-92.67% mortality). Only Ae. albopictus larvae from fogging-free residential areas that were tolerant to fenthion (97.33% mortality), whereas Ae. albopictus larvae from dengue prone residential areas were highly resistant to the same organophosphate (88.33% mortality). Cross resistance between intraclass and interclass larvicides of organochlorines and organophosphates were also exhibited in this study. The present study provided baseline data on various susceptibility levels of Ae. albopictus larval populations from different types of agricultural and non-agricultural localities against organochlorines and organophosphates at WHO recommended dosages. Nevertheless, further susceptibility investigations are suggested using revised doses of larvicides established from the local reference strain of Ae. albopictus to prevent the underestimation or overestimation of insecticide resistance level among Ae. albopictus field strains of larvae.
    Matched MeSH terms: Malathion
  16. Laboratory insecticide susceptibility tests against Mansonia larvae
    Yap HH, Hanapi S
    Southeast Asian J Trop Med Public Health, 1976 Dec;7(4):575-80.
    PMID: 67647
    Insecticides Abate, DDT, Dowco-214, Dursban, fenitrothion, fenthion, gamma-HCH, and malathion were tested against the field collected fourth instars larvae of Mansonia from Penang Island, Malaysia. The larvae appeared to be highly susceptible to Dursban and Abate with LC50 values of 1.54 and 1.92 parts per billion respectively. Other chemicals, in decreasing degree of effectiveness, were gamma-HCH, fenthion, P,P'-DDT, Dowco-214, fenithrothion and malathion. The potential use of these chemicals in Mansonia control was discussed. A simple method for collecting and testing Mansonia larvae was also described.
    Matched MeSH terms: Malathion
  17. First molecular genotyping of insensitive acetylcholinesterase associated with malathion resistance in Culex quinquefasciatus Say populations in Malaysia
    Low VL, Chen CD, Lim PE, Lee HL, Lim YA, Tan TK, et al.
    Pest Manag Sci, 2013 Dec;69(12):1362-8.
    PMID: 23404830 DOI: 10.1002/ps.3512
    Given that there is limited available information on the insensitive acetylcholinesterase in insect species in Malaysia, the present study aims to detect the presence of G119S mutation in the acetylcholinesterase gene of Culex quinquefasciatus from 14 residential areas across 13 states and a federal territory in Malaysia.
    Matched MeSH terms: Malathion/pharmacology*
  18. Fulltext Current insecticide susceptibility status of Malaysian Anopheles maculatus Theobald to malathion, permethrin, DDT and deltamethrin
    Rohani A, Aziz I, Zurainee MN, Rohana SH, Zamree I, Lee HL
    Trop Biomed, 2014 Mar;31(1):159-65.
    PMID: 24862056 MyJurnal
    Chemical insecticides are still considered as important control agents for malaria vector control. However, prolonged use of these chemicals may select mosquito vectors for resistance. In this study, susceptibility status of adult Anopheles maculatus collected from 9 localities in peninsular Malaysia, viz., Jeli, Temerloh, Pos Banun, Senderut, Jeram Kedah, Segamat, Kota Tinggi, Kluang and Pos Lenjang were determined using the standard WHO bioassay method in which the adult mosquitoes were exposed to standard insecticide impregnated papers malathion, permethrin, DDT and deltamethrin--at pre-determined diagnostic dosage. Deltamethrin was most effective insecticide among the four insecticides tested, with the LT50 of 29.53 min, compared to malathion (31.67 min), DDT (47.76 min) and permethrin (48.01 min). The effect of all insecticides on the laboratory strain was greater (with all insecticides demonstrated LT50 < 1 hour) than the field strains (deltamethrin 32.7, malathion 53.0, permethrin 62.0, DDT 67.4 min). An. maculatus exhibited low degree of resistance to all test insecticides, indicating that these chemical insecticides are still effective in the control of malaria vector.
    Matched MeSH terms: Malathion/pharmacology
  19. Insecticides in dry sugar baits for the control of the house-fly, Musca domestica L
    Singh KI, Hooi CW, Ha LS
    Southeast Asian J Trop Med Public Health, 1971 Jun;2(2):244-8.
    PMID: 4109414
    Matched MeSH terms: Malathion/pharmacology
  20. Effects of pesticide use on semen quality among farmers in rural areas of Sabah, Malaysia
    Hossain F, Ali O, D'Souza UJ, Naing DK
    J Occup Health, 2010;52(6):353-60.
    PMID: 20924153
    OBJECTIVES: To determine the relationship between semen quality and exposure to pesticide residues.

    METHODS: A cross-sectional study was conducted among male farmers from 3 different communities in Sabah, Malaysia. A total of 152 farmers participated in this study of whom 62 farmers had been exposed to either paraquat or malathion or both to varying extents. Questionnaires were designed to record a history of pesticides exposure and other potential risk factors among farmers. All semen samples were collected, processed and analyzed by qualified personnel based on WHO guidelines. Volume, pH, sperm concentration, motility, morphology and WBC count were examined and recorded. The association between pesticide exposure and semen parameters was highly significant.

    RESULTS: The mean values of volume, pH, sperm concentration, motility, and WBC count were significantly less in the exposed group than in compared with the non-exposed group, with p<0.005. Those who were exposed to pesticides had greater risk of having abnormal semen parameters than those in with the non exposed group, with p values of less than 0.05. The comparison between semen qualities such as lower sperm count, motility and higher percentage of sperm abnormality of those exposed to different types of pesticides (paraquat and malathion) showed no significant differences.

    CONCLUSION: The results showed a significant decline in semen quality with a decline in sperm count, motility and higher percent of teratospermia among subjects with pesticide exposure, and those who were exposed to pesticides had significantly 3 to 9 times greater risk of having abnormal semen parameters.

    Matched MeSH terms: Malathion/adverse effects*
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