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PubMed2001

Comparative efficacy of several insecticides for control of cattle lice (Mallophaga: Trichodectidae and Anoplura: Haematopinidae).

Several insecticides were applied to cattle at various rates, mixtures, application methods and numbers of treatments and evaluated for control of cattle lice. The insecticides included permethrin at various rates as a pour-on with and without the synergist piperonyl butoxide (PBO), and also at various rates as a spray with and without PBO. Pirimiphos-methyl was evaluated as a pour-on at various rates and with one or two applications. Lambda cyhalothrin in microencapsulated formulation was compared to a non-microencapsulated formulation. Rabon(R) was applied as a pour-on at two rates and at one or two treatments for each rate. Dimilin(R) was applied as a pour-on at two rates and mixed with permethrin and applied at two rates. Five endectocides, Eprinex(R), Ivomec(R), Dectomax(R), Cydectin(R) and Phoenectin(R) were all applied at the same rate. The cattle utilized in this research were all infested with a mixture of lice species. The species included: Bovicola (Damalinia) bovis (L.), Haematopinus eurysternus (Nitzsch), Linognthus vituli (L.) and Solenoptes capillatus (Enderlein). Most of the cattle were infested with at least two species and some had three or all four species present. All of the treatments except permethrin 1.0%+5% PBO, at a rate of 3ml/45.4kgwt. provided acceptable lice control with one application. Data indicated that applying the insecticides in early January should provide enough control to render the need for a second treatment unnecessary.

Animals↗

PubMed2004

Determination of enantiomers of synthetic pyrethroids in water by solid phase microextraction - enantioselective gas chromatography.

Solid phase microextraction (SPME) is an ideal sample preparation technique because of its speed and solvent-free features. Sampling by SPME is selective and only the dissolved concentration is measured, which allows measurement of the bioavailable fraction of a contaminant in aqueous media. One potential application of SPME is for analysis of enantiomers of chiral contaminants in environmental samples. In this study, a method was developed for determining enantiomers of (Z)-cis-bifenthrin and cis-permethrin in water using coupled SPME and enantioselective gas chromatography (GC). Following SPME sampling, enantiomers of (Z)-cis-bifenthrin and cis-permethrin were separated at the baseline on a beta-cyclodextrin-based enantioselective column, and analyte enrichment onto the SPME fiber was not enantioselective. The GC response increased as sampling time was increased from 0 to 240 min, and as sampling temperature was increased from 20 to 40 degrees C. Organic solvents such as methanol, acetone, and acetonitrile enhanced, while soil extracts slightly decreased, the GC response. The integrated SPME-enantioselective GC method was used to analyze surface runoff samples. The analysis showed preferential degradation of the 1S-3S enantiomer over the 1R-3R enantiomer for both (Z)-cis-bifenthrin and cis-permethrin. The concentrations detected by SPME-GC were substantially smaller than those determined following solvent extraction, suggesting that SPME-enantioselective GC analysis selectively measured the dissolved fraction.

Chromatography, Gas↗

PubMed2001

Glutathione S-transferases as antioxidant defence agents confer pyrethroid resistance in Nilaparvata lugens.

Selection of a laboratory colony of the brown planthopper Nilaparvata lugens with the pyrethroids permethrin and lambda-cyhalothrin increased its resistance to both insecticides. Biochemical analysis and synergistic studies with metabolic inhibitors indicated that elevated glutathione S-transferases (GSTs) with a predominant peroxidase activity conferred resistance to both pyrethroids, whereas esterases conferred part of the resistance to permethrin. Purified esterases hydrolysed permethrin at a slow rate, but incubation of either pyrethroid or their primary metabolites with partially purified GSTs had no effect on the metabolic profile. Although GSTs were sensitive to inhibition by both pyrethroids, they did not serve as binding proteins, as previously hypothesized [Grant and Matsumura (1988) Insect Biochem. 18, 615-622]. We demonstrate that pyrethroids, in addition to their neurotoxic effect, induce oxidative stress and lipid peroxidation in insects. Pyrethroid exposure induced lipid peroxides, protein oxidation and depleted reduced glutathione. Elevated GSTs in the resistant strains attenuated the pyrethroid-induced lipid peroxidation and reduced mortality, whereas their in vivo inhibition eliminated their protective role. We therefore hypothesize that the main role of elevated GSTs in conferring resistance in N. lugens is through protecting tissues from oxidative damage. Our study extends the GSTs' range of efficacy to pyrethroid insecticides and possibly explains the role of elevated GSTs in other pyrethroid-resistant insects.

Animals↗

PubMed2002

Widespread insecticide resistance in head lice to the over-the-counter pediculocides in England, and the emergence of carbaryl resistance.

BACKGROUND: Increasing resistance to insecticides used for the control of head lice infestation has been documented over the last decade. Treatment failure and tolerance to insecticides have been validated in a number of studies undertaken in several U.K. centres. OBJECTIVES: To establish the extent of insecticide resistance in head lice and acetylcholinesterase activity in the presence of carbaryl in head lice. METHODS: Head lice were collected from school children in four centres across England (Exmouth, Loughborough, Leeds and South Shields), and tested in their response to the insecticides permethrin, phenothrin, malathion and carbaryl. Data were compared with information collected in Bristol and Bath in 1998 and with susceptible body lice. The activity of louse acetylcholinesterase was measured with and without carbaryl in head lice collected in Bristol, Leeds, Loughborough and in body lice. The efficacy of a 1% carbaryl lotion was compared in children in Bristol and Leeds. RESULTS: Compared with body lice, head lice from all six centres were significantly different in their response (P < 0.0001) to permethrin, phenothrin and malathion after 2-h exposure tests. There were significant differences in louse acetylcholinesterase activity in body lice, and head lice collected in Loughborough and Bristol in the presence or absence of carbaryl (P < 0.001), indicating enzyme inhibition. However, the difference for lice from Leeds was not significant (P = 0.363) suggesting that the enzyme was resistant to carbaryl. Eighty-nine per cent of children treated in Leeds with carbaryl were cured compared with 100% in Bristol. CONCLUSIONS: The data suggest head lice resistance is present in many parts of England to over-the-counter products containing synthetic insecticides (permethrin, phenothrin and malathion). They further suggest that resistance is starting to develop to carbaryl in head lice in Leeds and that extensive use of this product would lead to significant resistance.

Acetylcholinesterase↗

PubMed2001

Quantification of pyrethroid insecticides from treated bednets using a mosquito recombinant glutathione S-transferase.

Recombinant glutathione S-transferase (agGST1-6) from the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) was expressed in Escherichia coli using a pET3a vector system. The expressed enzyme was biochemically active with reduced glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). Activity of agGST1-6 with GSH and CDNB was inhibited to different degrees by both alpha-cyano and non-alpha-cyano pyrethroid insecticides. This inhibition was used to develop an assay for quantification of pyrethroids. Standard curves of insecticide concentration against percentage of enzyme inhibition or volume of iodine solution were established by spectrophotometry and iodine volumetric titration, respectively, for permethrin and deltamethrin. These assays allowed estimation of pyrethroid concentrations both spectrophotometrically and visually. For the residue assay of each insecticide, a cut-off point of 50% of the initial pyrethroid impregnation concentration was used, which should differentiate between biologically active and inactive treated bednets. The cross-reactivity of the primary permethrin photodegradants (3-phenoxyalcohol and 3-phenoxybenzoic acid) with the recombinant agGST1-6 was assayed in the same system. No agGST1-6 inhibition by the insecticide metabolites was observed, suggesting that the system is unaffected by primary permethrin metabolites and will accurately measure insecticide parent compound concentrations. The estimated pyrethroid insecticide concentrations, given spectrophotometrically and by iodine titration assay, were comparable to those obtained by direct HPLC quantification of residues extracted from bednets. Hence, it should be relatively easy to adapt this method to produce a test kit for residue quantification in the field.

Animals↗

PubMed1999

Epidemiology and control of scabies in an Egyptian village.

BACKGROUND: Some studies have addressed the epidemiology of scabies among rural populations in developing countries; however, the epidemiology of scabies among the rural population in Egypt is unknown. We sought to determine the magnitude of scabies infestation in an Egyptian village and to evaluate the control measures after 1 year. METHODS: This study was carried out on 3147 residents of Mit-Moaned village in Dakahlia govemorate, Egypt. It was a cross-sectional follow-up study where the same individuals examined in round I were re-examined in round III. The two rounds were separated by a period of 1 year, during which infested patients were followed up and new cases were discovered (round II). Patients and their household contacts received treatment with topical permethrin. Patients showing resistance to permethrin received a single oral dose of ivermectin. RESULTS: In round III, the overall prevalence rate of scabies was reduced from 5.4% in round I to 1.1%. The incidence of new cases among susceptible persons during round II was 1.1%. Scabies was significantly (P < 0.05) more prevalent among families of large size, high crowding index at night, low socioeconomic standards, and those receiving their water supply from a hand pump. Children younger than 10 years showed the highest prevalence. CONCLUSIONS: Our data provide the first complete picture of the epidemiology of scabies in rural Egypt. The epidemiologic characteristics of the disease should be considered in the design of disease control programs for other villages with scabies epidemics. Our findings revealed that good control was achieved with the following: increased awareness and better case finding, education of the staff at the rural health unit, improved hygiene measures, and massive treatment campaigns using effective drugs such as topical permethrin and oral ivermectin.

Adolescent↗

PubMed1990

Susceptibility of insecticide-susceptible and wild house flies (Diptera: Muscidae) to abamectin on whitewashed and unpainted wood.

Unpainted plywood panels treated with 0.1% abamectin (avermectin B1) provided greater than 90% control of house flies, Musca domestica L., susceptible to insecticides for 4 wk and greater than 70% control for 7 wk compared with 46-92% control observed with permethrin at the same time and rate of application. Efficacy of abamectin on whitewashed panels was similar to that observed on unpainted panels, whereas permethrin was ineffective on whitewashed panels at all rates tested (range, 0.001-0.1%) at all intervals after treatment. Bioassays of newly colonized house flies resistant to permethrin indicated that wild populations may be cross-resistant to abamectin.

Animals↗

PubMed1991

Efficacy of three pyrethroids against Leptotrombidium fletcheri (Acari: Trombiculidae) infected and noninfected with scrub typhus.

Toxicities of three pyrethroids, d-phenothrin, decamethrin, and permethrin, were evaluated in the laboratory against Leptotrombidium fletcheri (Womersley & Heaslip). The susceptibilities between populations of the species infected and noninfected with scrub typhus were investigated. The three pesticides exhibited different toxicities to the chiggers. D- phenothrin was the most toxic, followed by decamethrin, then permethrin. There were no significant differences between susceptibilities of the infected and noninfected populations. Log-probit regression lines indicated that the species was most sensitive to increasing concentrations of d-phenothrin and least sensitive to permethrin. The results show that the three pesticides are potential candidates for chemical control of L. fletcheri. It may be possible in the future to conduct similar bioassays only with the noninfected population, thus reducing risk of infection to workers conducting the bioassays. Similarly, there may not be a need to separate field-collected chiggers into the two populations before performing the bioassays.

Animals↗

PubMed1991

Base-line susceptibility of the oriental latrine fly, Chrysomya megacephala (Diptera: Calliphoridae), to five insectides.

Susceptibility to five insecticides was assessed on seven colonies of the oriental latrine fly, Chrysomya megacephala (Fabricius), originating from Japan, Hong Kong, Philippines, Indonesia and Papua New Guinea, and on C. saffranèa (Bigot) from PNG. All the colonies were susceptible to fenitrothion, diazinon, dichlorvos, permethrin and gamma-HCH, although the Jakarta, Manila and Tokyo colonies of C.megacephala were least susceptible (most tolerant) to diazinon, dichlorvos and permethrin. Feral forms of both Chrysomya species were 4-5-fold more susceptible to permethrin at the LD50 level than were all six colonies of the synanthropic form of C.megacephala.

Animals↗

PubMed2003

Mutations of the para sodium channel of Drosophila melanogaster identify putative binding sites for pyrethroids.

The effects of two pyrethroids on recombinant wild-type and mutant (pyrethroid-resistant) Na+ channels of Drosophila melanogaster have been studied. Three mutations that confer resistance (kdr/superkdr) to pyrethroids were inserted, either individually or in combination, into the para Na+ channel of D. melanogaster: L1014F in domain IIS6, M918T in the IIS4-S5 linker, and T929I in domain IIS5. Channels were expressed in Xenopus laevis oocytes and the effects of the pyrethroids permethrin (type I) and deltamethrin (type II) on Na+ currents were investigated using voltage clamp. The Na+ channels deactivated slowly after deltamethrin treatment, the resultant "tail" currents being used to quantify the effects of this pyrethroid. The Hill slope of 2 for deltamethrin action on the wild-type channel and the mutant L1014F channel is indicative of cooperative binding at two or more sites on these channels. In contrast, binding to the mutants M918T and T929I is noncooperative. Tail currents for the wild-type channel and L1014F channel decayed biphasically, whereas those for M918T and T929I mutants decayed monophasically. The L1014F mutant was approximately 20-fold less sensitive than the wild-type to deltamethrin. Surprisingly, the sensitivity of the double mutant M918T+L1014F to deltamethrin was similar to that of M918T alone, whereas the sensitivity of T929I+L1014F was >30,000-fold lower than that of T929I. Permethrin was less potent than deltamethrin, and its binding to all channel types was noncooperative. The decays of permethrin-induced tail currents were exclusively monophasic. These findings are discussed in terms of the properties and possible locations of pyrethroid binding sites on the D. melanogaster Na+ channel.

Amino Acid Substitution↗

PubMed2003

Resistance status of house flies (Diptera: Muscidae) from southeastern Nebraska beef cattle feedlots to selected insecticides.

The status of resistance to three insecticides (permethrin, stirofos, and methoxychlor), relative to a laboratory-susceptible colony, was evaluated in field populations of house flies, Musca domestica L., collected from two beef cattle feedlots in southeastern Nebraska. Topical application and residual exposure to treated glass surfaces were suitable methods for determining the resistance status of house flies to permethrin, stirofos, or methoxychlor. However, in most cases, residual exposure was more sensitive in resistance detection (i.e., higher resistance ratios). The field populations tested were moderately resistant to permethrin (RR = 4.9-fold and RR = 7.3-fold, for topical application and residual exposure, respectively) and extremely resistant to stirofos and methoxychlor (not accurately quantifiable because of low mortality at the highest possible concentrations or doses). Probable explanations for the resistance status of these house fly populations and implications for global feedlot fly management are discussed.

Animals↗

PubMed2005

Insecticide susceptibility of Aedes aegypti and Aedes albopictus across Thailand.

Aedes aegypti (L.) and Aedes albopictus (Skuse), two important vectors of dengue fever and dengue hemorrhagic fever, were collected from Mae Sot, Nakhon Sawan, Nakhon Ratchasima, Surat Thani, and Phatthalung, Thailand, from July 2003 to April 2004. The patterns of insecticide susceptibility to temephos, malathion, and permethrin of both Ae. aegypti and Ae. albopictus larvae were determined. Ae. aegypti from all study sites were resistant to permethrin, they but were susceptible to malathion. Resistance to temephos was detected in all strains of Ae. aegypti, except those from Nakhon Ratchasima. Ae. albopictus larvae had low levels of resistance to all three insecticides, except Mae Sot and Phatthalung strains, which were resistant to permethrin.

Aedes↗

PubMed2006

Use of carboxylesterase activity to remove pyrethroid-associated toxicity to Ceriodaphnia dubia and Hyalella azteca in toxicity identification evaluations.

Increases in the use and application of pyrethroid insecticides have resulted in concern regarding potential effects on aquatic ecosystems. Methods for the detection of pyrethroids in receiving waters are required to monitor environmental levels of these insecticides. One method employed for the identification of causes of toxicity in aquatic samples is the toxicity identification evaluation (TIE); however, current TIE protocols do not include specific methods for pyrethroid detection. Recent work identified carboxylesterase treatment as a useful method for removing/detecting pyrethroid-associated toxicity. The present study has extended this earlier work and examined the ability of carboxylesterase activity to remove permethrin- and bifenthrin-associated toxicity to Ceriodaphnia dubia and Hyalella azteca in a variety of matrices, including laboratory water, Sacramento River (CA, USA) water, and Salinas River (CA, USA) interstitial water. Esterase activity successfully removed 1,000 ng/L of permethrin-associated toxicity and 600 ng/L of bifenthrin-associated toxicity to C. dubia in Sacramento River water. In interstitial water, 200 ng/L of permethrin-associated toxicity and 60 ng/L of bifenthrin-associated toxicity to H. azteca were removed. The selectivity of the method was validated using heat-inactivated enzyme and bovine serum albumin, demonstrating that catalytically active esterase is required. Further studies showed that the enzyme is not significantly inhibited by metals. Matrix effects on esterase activity were examined with municipal effluent and seawater in addition to the matrices discussed above. Results confirmed that the esterase retains catalytic function in a diverse array of matrices, suggesting that this technique can be adapted to a variety of aquatic samples. These data demonstrate the utility of carboxylesterase treatment as a viable step to detect the presence of pyrethroids in receiving waters.

Ammonia↗

PubMed1984

Effects of pyrethroids on lymphocyte membrane lipid packing order.

The effects of pyrethroids on the membrane lipid packing order of murine splenic lymphocytes have been investigated by utilizing the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Fluorescence anisotropy and lifetime measurements indicated alterations in the environment of the probe at pyrethroid concentrations near 1 microM. Decreased packing order of membrane lipids was detected for permethrin and cypermethrin by decreased anisotropy values. Permethrin and cypermethrin decreased fluorescence lifetime over a concentration range similar to that causing anisotropy changes. Anisotropy was predominantly increased in the presence of fluvalinate and fenpropathrin, indicating pronounced quenching of fluorescence by these compounds. However, the anisotropy changes in response to fluvalinate and fenpropathrin occurred at concentrations which were similar to effective concentrations of permethrin and cypermethrin. Compared to the other pyrethroids tested, allethrin required approximately 10 fold higher concentrations to alter anisotropy and lifetime values. Effects of pyrethroids on the phase transition of dipalmitoyl phosphatidylcholine liposomes were also studied to give further insight into the membrane interactions of these compounds. Results from the liposomal system indicate that the effects of pyrethroids on membrane order which were observed in the lymphocyte may be generalizable to other cell types.

Allethrins↗

PubMed1983

Susceptibility of northern fowl mites in North Carolina to five acaricides.

The susceptibilities (dosage-response regression curves) of northern fowl mites collected from six poultry farms in North Carolina were determined for five acaricides by exposure of the mites for 24 hr to acaricide residues inside glass pipettes. The residue concentrations were expressed as parts per million on a weight-volume basis of the acaricide-acetone solution in which the pipettes were immersed prior to testing. All of the acaricides, except malathion, were highly toxic to the northern fowl mites. The mean LD50 values (ppm) were: permethrin, .53; tetrachlorvinphos, 4.06; carbaryl, 4.11; and coumaphos, 5.04. For malathion, the mean LD50 for mites from three caged layer flocks was 119.35 ppm while concentrations as high as 500 ppm gave only low mortalities (20% or less) of mites from the other flocks and LD50 values could not be calculated. These data show that northern fowl mites are highly resistant to malathion in North Carolina, as has been reported elsewhere, but there is no evidence of resistance to the other acaricides tested. The effect of temperature on the toxicity to northern fowl mites of the newest acaricide, permethrin, was determined. Permethrin was significantly more toxic at 20 C than at 25, 30, or 35 C.

Animals↗

PubMed1987

Lyme disease and babesiosis: acaricide focused on potentially infected ticks.

Permethrin-treated cotton, intended as rodent nesting material, was distributed in wooded sites in which the agents of Lyme disease and babesiosis were enzootic, in order to kill immature Ixodes dammini, the ticks that transmit these human pathogens. Such ticks feed most abundantly on white-footed mice (Peromyscus leucopus), apparently the main reservoir hosts of these agents, and tend to concentrate in mouse burrows. Mice captured after permethrin-treated cotton was distributed, were infested by a tenth as many ticks as were those captured in adjacent nontreated sites, a difference that continued throughout the 4-month period of observation. On average, 72% of all mice captured in treated sites were free of ticks, while virtually all mice captured in nontreated sites were infested. Voles (Microtus pennsylvanicus), however, were tick-infested, regardless of site of capture. Laboratory-reared I. dammini failed to attach to mice captured in treated sites, and most such exposed ticks died. Distribution of permethrin-treated cotton appears to be a means for preventing transmission of the pathogens that cause human babesiosis and Lyme disease.

Animals↗

PubMed1999

Resistance to two pyrethroids in Anopheles sinensis from Zhejiang, China.

Probabilities of pyrethroid resistant genotypes in natural populations of Anopheles sinensis Wiedemann were measured with deltamethrin and permethrin. The median lethal concentrations (LC50s) of deltamethrin and permethrin in the susceptible larval population were 0.0209 and 0.1747 ppm, respectively. Under dosages that produced 99% mortality in susceptible laboratory strains of larvae, the lethal percentage of Cangnan larval field populations after 20 min of exposure was only 61.23% for deltamethrin and 64.92% for permethrin. This was much lower than those of other natural populations. Also, the probability of pyrethroid-resistant genotypes in Cangnan adult field populations was at the highest, reaching 0.5867. The results are discussed in relation to future mosquito control programs.

Animals↗

PubMed2003

Pyrethroid susceptibility & enzyme activity in two malaria vectors, Anopheles stephensi (Liston) &. A. culicifacies (Giles) from Mysore, India.

BACKGROUND & OBJECTIVES: Anopheles stephensi and A. culicifacies are the two major vectors of malaria in Karnataka. These mosquito populations are continuously being exposed directly or indirectly to different insecticides including the most effective pyrethroids. Therefore, there is a threat of insecticide resistance development. We subjected these vectors to larval bioassay using two popular pyrethroids viz deltamethrin and permethrin. An attempt was also made to correlate the activities of certain detoxifying enzymes such as A- esterase, B-esterase, glutathione-S transferase (GST) and glucose-6-phosphate dehydrogenase (G6PD) with the tolerance levels of the two vectors. METHODS: Larval bioassay was carried out following the standard WHO procedure on field-collected larvae. The LC50 and LC90 values were calculated following Probit analysis. Biochemical estimations were done with a U V spectrophotometer and the isozyme studies employing native polyacrylamide gel electrophoresis (PAGE). RESULTS: The results of the larval bioassay revealed that A. stephensi has more tolerance to deltamethrin than A. culicifacies and vice versa for permethrin. Biochemical estimations revealed significantly (P < 0.05) higher levels of A-esterase and GST activity in A. stephensi whereas A. culicifacies showed significantly higher (P < 0.05) levels of B-esterase and G6PD activity. The total larval protein assayed was found to be more (P < 0.05) in A. stephensi. The isozyme profiles also revealed difference in mobility, intensity and the number of bands. INTERPRETATION & CONCLUSION: As these malaria vectors are exposed to different kinds of insecticides, they develop increased enzyme activities to overcome the insecticide pressure. This has enhanced the tolerance level against the pyrethroids tested. Thus, A. stephensi was found to be tolerant to deltamethrin depicting a higher activity of A-esterase and GST enzymes, whereas the higher activity of B-esterase and G6PD has resulted in the development of tolerance to permethrin in A. culicifacies.

Animals↗