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Pyrethroid Resistance (pyrethroid + resistance)
Selected AbstractsHigh-resolution melt analysis for the detection of a mutation associated with permethrin resistance in a population of scabies mitesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2008C. PASAY Abstract Permethrin as a topical acaricide cream is widely used to treat scabies. The neuronal voltage-sensitive sodium channel (Vssc), necessary for the generation of action potentials in excitable cells, is the target of pyrethroid acaricides such as permethrin. Pyrethroid resistance has been linked to specific mutations in the Vssc gene. Following the partial sequencing of the Vssc gene in the scabies mite Sarcoptes scabiei (L.) (Astigmata: Sarcoptidae), we compared Vssc gene sequences from permethrin-sensitive and -tolerant S. scabiei var. canis Gerlach mites, and identified a G to A single nucleotide polymorphism (SNP) in permethrin-tolerant mites resulting in an amino acid change from glycine to aspartic acid in domain III S6. The mutation is in a region of the gene where mutations have been identified in a range of pyrethroid-resistant arthropods. Results of in vitro permethrin exposure assays showed that survival rates for mites bearing the mutation were similar to those previously reported for mites from human subjects where clinical tolerance to permethrin had been observed. A real-time polymerase chain reaction,high-resolution melt (PCR-HRM) assay was developed to detect this SNP. This assay provides a useful methodology for screening for this and other mutations associated with permethrin resistance in scabies mite populations and thus facilitates surveillance for acaricide resistance. [source] Effect of pretreatment with piperonyl butoxide on pyrethroid efficacy against insecticide-resistant Helicoverpa armigera (Lepidoptera: Noctuidae) and Bemisia tabaci (Sternorrhyncha: Aleyrodidae)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2006Susan J Young Abstract Pyrethroid resistance in B-type Bemisia tabaci Gennadius and Australian Helicoverpa armigera Hübner field populations is primarily conferred by esterase isoenzymes which metabolise and sequester pyrethroid insecticides. It has been shown previously that pyrethroid resistance-associated esterases in H. armigera are inhibited by the insecticide synergist piperonyl butoxide (PBO) over a 22-h period. It is demonstrated here that similar inhibition can be obtained against B-type B. tabaci. Small-scale field trials showed excellent levels of pyrethroid control when insects were pretreated with PBO and then dosed with pyrethroid during the time of maximum esterase inhibition. These results demonstrate that PBO can restore pyrethroid efficacy in the field against both B-type B. tabaci and resistant H. armigera. Copyright © 2005 Society of Chemical Industry [source] Glutathione S -transferase detoxification as a potential pyrethroid resistance mechanism in the maize weevil, Sitophilus zeamaisENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2003Daniel B. Fragoso Abstract Insecticide resistance patterns among 16 Brazilian populations of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), were recognized by surveying resistance to three organophosphates (chlorpyrifos-methyl, malathion, and pirimiphos-methyl) and three pyrethroids (cypermethrin, deltamethrin, and permethrin). Two population clusters were obtained: one with three populations (Bragança Paulista, Cristalina, and Nova Andradina) showing low frequency of cypermethrin resistance (13,36%) and negligible frequency of deltamethrin resistance (2,9%); and another with six populations (Campos dos Goytacazes, Ivinhema, Patos de Minas, Penápolis, Uberlândia, and Venda Nova) showing low to negligible levels of pyrethroid resistance (0,23%). The remaining seven populations, including a susceptible, and a DDT- and pyrethroid-resistant reference populations (Sete Lagoas and Jacarezinho, respectively), were significantly different from each other and from the two recognized clusters. In contrast with pyrethroid resistance, organophosphate resistance was negligible except for chlorpyrifos-methyl in two populations (Fátima do Sul and Penápolis). There was no correlation between geographic distance and the Mahalanobis distance estimated from the resistance pattern ordination of the populations by canonical variate analysis, suggesting local selection and/or broad dispersal of resistant populations by grain trade. The results of biochemical in vitro studies measuring the activity of detoxification enzymes (esterases and glutathion S -transferases) in conjunction with canonical correlation analysis suggest a major involvement of enhanced conjugation by glutathione S -transferases (> 2-fold increase) in pyrethroid resistance and, in the case of cypermethrin resistance, enhanced phosphotriesterase activity. [source] Monitoring pyrethroid resistance in field collected Blattella germanica Linn. (Dictyoptera: Blattellidae) in IndonesiaENTOMOLOGICAL RESEARCH, Issue 2 2009Intan AHMAD Abstract The German cockroach, Blattella germanica, is a major and the most common pest in public areas in Indonesia. Although intensive control measures have been carried out to control the populations of this pest, results have been far from successful, which is believed to be because of its resistance to insecticides. A standard World Health Organization (WHO) glass jar test was carried out to determine the resistance level of this insect to pyrethroid insecticides, the most commonly used insecticides for cockroach control in Indonesia. A susceptible S1 strain collected from Tembagapura Papua was compared with four strains collected from Bandung, West Java: strain S2, from a local restaurant; strain S3, from the Bandung train station; and strains S4 and S5, from two different hotels. All strains showed low resistance to the pyrethroid, except the S5 strain, which had a Resistance Ratio (RR)50 of 95 for permethrin. The addition of piperonyl butoxide (PBO) suggests that the detoxifying enzyme mixed function oxidases (MFO) played an important role in the development of resistance to permethrin in the S5 strain, suggested by the high Synergist Ratio (SR) of 70.4. However, the low level of resistance to cypermethrin was not affected by PBO, suggesting that other mechanisms of pyrethroid resistance are involved. Our study is the first report of German cockroach resistance to permethrin in Indonesia, and the findings can be used in formulating potential strategies for cockroach resistance management. [source] Over expression of a Cytochrome P450 (CYP6P9) in a Major African Malaria Vector, Anopheles Funestus, Resistant to PyrethroidsINSECT MOLECULAR BIOLOGY, Issue 1 2008D. A. Amenya Abstract Anopheles funestus Giles is one of the major African malaria vectors. It has previously been implicated in a major outbreak of malaria in KwaZulu/Natal, South Africa, during the period 1996 to 2000. The re-emergence of this vector was associated with monooxygenase-based resistance to pyrethroid insecticides. We have identified a gene from the monooxygenase CYP6 family, CYP6P9, which is over expressed in a pyrethroid resistant strain originating from Mozambique. Quantitative Real-Time PCR shows that this gene is highly over expressed in the egg and adult stages of the resistant strain relative to the susceptible strain but the larval stages showed almost no difference in expression between strains. This gene is genetically linked to a major locus associated with pyrethroid resistance in this A. funestus population. [source] The kdr mutation occurs in the Mopti form of Anopheles gambiaes.s. through introgressionINSECT MOLECULAR BIOLOGY, Issue 5 2000M. Weill Abstract Anopheles gambiaes.s. is a complex of sibling taxa characterized by various paracentric inversions. In west and central Africa, where several taxa are sympatric, a kdr mutation responsible for pyrethroid resistance has been described in only one (the S taxon), suggesting an absence of gene flow between them. Following a thorough sampling, we have found a kdr mutation in another taxon (M). To establish whether this mutation is the same event or not, the large intron upstream of the kdr mutation was sequenced to find polymorphic sites in susceptible/resistant and M/S mosquitoes. The low genetic diversity found in this DNA region indicates that a local genetic sweep has recently occurred. However, some polymorphic sites were found, and it is therefore concluded that the kdr mutation in the M taxon is not an independent mutation event, and is best explained by an introgression from the S taxon. These results are discussed within the context of possible gene flow between members of An. gambiae s.s. taxa, and with the possible spread of the kdr mutation in other closely related malaria vectors of the An. gambiae complex. [source] Pyrethroid resistance/susceptibility and differential urban/rural distribution of Anopheles arabiensis and An. gambiae s.s. malaria vectors in Nigeria and GhanaMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2003M. Kristan Abstract., Resistance to pyrethroid insecticides and DDT caused by the kdr gene in the malaria vector Anopheles gambiae Giles s.s. (Diptera: Culicidae) has been reported in several West African countries. To test for pyrethroid resistance in two more countries, we sampled populations of the An. gambiae complex from south-western Ghana and from urban and rural localities in Ogun State, south-west Nigeria. Adult mosquitoes, reared from field-collected larvae, were exposed to the WHO-recommended discriminating dosage of exposure for 1 h to DDT 4%, deltamethrin 0.05% or permethrin 0.75% and mortality was recorded 24 h post-exposure. Susceptibility of An. gambiae s.l. to DDT was 94,100% in Ghana and 72,100% in Nigeria, indicating low levels of DDT resistance. Deltamethrin gave the highest mortality rates: 97,100% in Ghana, 95,100% in Nigeria. Ghanaian samples of An. gambiae s.l. were fully susceptible to permethrin, whereas some resistance to permethrin was detected at 4/5 Nigerian localities (percentage mortalities 75, 82, 88, 90 and 100%), with survivors including both An. arabiensis Patton and An. gambiae s.s. identified by PCR assay. Even so, the mean knockdown time was not significantly different from a susceptible reference strain, indicating absence or low frequency of kdr -type resistance. Such low levels of pyrethroid resistance are unlikely to impair the effectiveness of pyrethroid-impregnated bednets against malaria transmission. Among Nigerian samples of An. gambiae s.l., the majority from two urban localities were identified as An. arabiensis, whereas the majority from rural localities were An. gambiae s.s. These findings are consistent with those of M. Coluzzi et al. (1979). Differences of ecological distribution between molecular forms of An. gambiae s.s. were also found, with rural samples almost exclusively of the S-form, whereas the M-form predominated in urban samples. It is suggested that ,urban island' populations of An. arabiensis and of An. gambiae s.s. M-form in the rainforest belt of West Africa might be appropriate targets for elimination of these malaria vectors by the sterile insect technique. [source] Pyrethroid and DDT cross-resistance in Aedes aegypti is correlated with novel mutations in the voltage-gated sodium channel geneMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2003C. Brengues Abstract. Samples of the dengue vector mosquito Aedes aegypti (L.) (Diptera: Culicidae) were collected from 13 localities between 1995 and 1998. Two laboratory strains, Bora (French Polynesia) and AEAE, were both susceptible to DDT and permethrin; all other strains, except Larentuka (Indonesia) and Bouaké (Ivory Coast), contained individual fourth-instar larvae resistant to permethrin. Ten strains were subjected to a range of biochemical assays. Many strains had elevated carboxylesterase activity compared to the Bora strain; this was particularly high in the Indonesian strains Salatiga and Semarang, and in the Guyane strain (Cayenne). Monooxygenase levels were increased in the Salatiga and Paea (Polynesia) strains, and reduced in the two Thai strains (Mae Kaza, Mae Kud) and the Larentuka strain. Glutathione S-transferase activity was elevated in the Guyane strain. All other enzyme profiles were similar to the susceptible strain. The presence of both DDT and pyrethroid resistance in the Semarang, Belem (Brazil) and Long Hoa (Vietnam) strains suggested the presence of a knock-down resistant (kdr)-type resistance mechanism. Part of the S6 hydrophobic segment of domain II of the voltage-gated sodium channel gene was obtained by RT-PCR and sequenced from several insects from all 13 field strains. Four novel mutations were identified. Three strains contained identical amino acid substitutions at two positions, two strains shared a different substitution, and one strain was homozygous for a fourth alteration. The leucine to phenylalanine substitution that confers nerve insensitivity to pyrethroids in a range of other resistant insects was absent. Direct neurophysiological assays on individual larvae from three strains with these mutations demonstrated reduced nerve sensitivity to permethrin or lambda cyhalothrin inhibition compared to the susceptible strains. [source] Molecular analysis of pyrethroid resistance conferred by target insensitivity and increased metabolic detoxification in Plutella xylostellaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2010Shoji Sonoda Abstract BACKGROUND: The pyrethroid resistance of the diamondback moth Plutella xylostella (L.) is conferred by increased gene expression of cytochrome P450 to detoxify the insecticide and/or through gene mutation of the sodium channel, which makes the individual insensitive to pyrethroids. However, no information is available about the correlation between the increased metabolic detoxification and the target insensitivity in pyrethroid resistance. RESULTS: Frequencies of pyrethroid-resistant alleles (L1014F, T929I and M918I) and two resistance-related mutations (A1101T and P1879S) at the sodium channel and expression levels of the cytochrome P450 gene CYP6BG1 were examined individually using laboratory and field strains of P. xylostella. Real-time quantitative PCR analysis using the laboratory strains revealed that levels of larval expression of the resistant strain, homozygous for the pyrethroid-resistant alleles other than the M918I, are significantly higher than those of the susceptible strain. In the field strains, the expression levels in insects having the same resistant alleles as those of the resistant strains varied greatly among individuals. The expression levels were not significantly higher than those in the heterozygotes. CONCLUSION: Significant correlation between the target insensitivity and the increased metabolic detoxification in pyrethroid resistance of P. xylostella was observed in the laboratory but not in the field. Copyright © 2010 Society of Chemical Industry [source] Inheritance of beta-cypermethrin resistance in the housefly Musca domestica (Diptera: Muscidae)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2008Lan Zhang Abstract BACKGROUND: Beta-cypermethrin, a synthetic pyrethroid insecticide, was applied frequently in the control of health pests including houseflies, Musca domestica L., in China. However, different levels of resistance to beta-cypermethrin were monitored in field strains of houseflies. A strain of M. domestica, 4420-fold resistant to beta-cypermethrin after continuous 25 generations of selection, was used in this paper to determine the mode of inheritance of pyrethroid resistance. RESULTS: The estimated realized heritability (h2) of beta-cypermethrin resistance was 0.30 in this resistant strain. Results of bioassays showed no significant difference in values of LD50 and slope of log dose-probit lines between reciprocal progenies F1 and F,1, and yielded values of , 0.10 (F1) and , 0.11 (F,1) for the degree of dominance (D). Chi-square analysis from responses of self-bred and backcross progenies (F2, BC1 and BC2 respectively) indicated that the null hypothesis, a single gene responsible for resistance, was accepted. The minimum number of independent segregation genes was 0.93 for F1 by Lande's method. CONCLUSION: It was concluded that beta-cypermethrin resistance in the housefly was inherited as a single, major, autosomal and incompletely recessive factor. These results would provide the basic information for pest management programmes. Copyright © 2007 Society of Chemical Industry [source] Linkage of genes for sodium channel and cytochrome P450 (CYP6B10) in Heliothis virescensPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2002Sujin Park Abstract Genetic linkage of hscp (heliothis sodium channel protein) and CYP6B10 was discovered in Heliothis virescens. The hscp gene encodes the sodium channel target of pyrethroid insecticides and cytochrome P450 genes encode important enzymes involved in detoxication of various pesticides. Previously, two mechanisms, nerve insensitivity due to sodium channel and synergism by propynyl aryl ethers, were observed in pyrethroid-resistant H virescens and were not separated by repeated back-crossing. We hypothesized genetic linkage of target site insensitivity and monooxygenase-mediated detoxication. Single nucleotide polymorphisms were discovered in IIS6 of hscp; Hpy of hscp and CYP6B10. Segregation of these and other markers was tested in backcrosses. We observed co-segregation of hscp to CYP6B10, but both genes assorted independently of y, ye and sex. Genes y and ye assorted independently of each other. This was the first observation of linkage between genes controlling detoxication and sodium ion channel insensitivity in a species known to express high levels of pyrethroid resistance. Linkage was not likely because this species has 31 chromosomes; therefore, we will investigate the possibility of a resistance cassette. We expect similar linkage in other noctuid pests. © 2001 Society of Chemical Industry [source] | ||||||||||