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PubMed1997

Biological monitoring of pyrethroids in blood and pyrethroid metabolites in urine: applications and limitations.

The objective of this study was to perform biological monitoring of subjects who are occupationally exposed to pyrethroids. The study group consisted of 30 pest control operators exposed to cyfluthrin, cypermethrin or permethrin. After exposure, 24-h urine samples were collected and 20 ml of blood was drawn. The pyrethroid metabolites cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzoic acid and fluorophenoxybenzoic acid were determined in the urine samples (limit of detection: 0.5 micrograms/l) by GC MS and the pyrethroids in plasma (limit of detection: 5 micrograms) GC-ECD. The concentrations of metabolites in the urine of the pest control operators ranged between < 0.5 micrograms/l and 277 micrograms/l urine. The concentrations of cyfluthrin, cypermethrin and permethrin in the plasma were below the limits of detection (< 5 micrograms/l). To test if the metabolites are specific for pyrethroid exposure, they were determined in the urine of non-exposed subjects (n = 40). In no case could pyrethroid metabolites be detected. A cyfluthrin elimination experiment showed that cyfluthrin metabolites are eliminated following first-order kinetics (t 1/2 = 6.4 h). Storage experiments demonstrate that frozen urine samples (-21 degrees C) show no significant losses of metabolites within a year. In contrast, pyrethroids stored in plasma are susceptible to further biodegeneration.

Adult↗

PubMed2003

Induction of cytochrome P-450 activity in individual Chironomus riparius Meigen larvae exposed to xenobiotics.

Cytochrome P450 activity in individual Chironomus riparius larvae was measured using a microtiter plate adaptation of the ethoxyresorufin-O-deethylase (EROD) assay. The sensitivity of this biomarker was tested by exposing larvae to phenobarbital (0.5 and 1.0 mM) and permethrin (1 and 10 microg/g). Both chemicals induced EROD activity in C. riparius larvae by up to 1.58-fold with PB and 2.47-fold with permethrin. EROD induction was more pronounced after 48 h. The initially high EROD activity in the controls suggested that P450s are induced by stress. Feeding levels prior to exposure also had a significant effect on EROD activity. EROD activity compared to the control was highest when larvae were fed double the normal ration. These results indicate that EROD activity in individual C. riparius may be a useful biomarker to add to a suite of biomarkers for the detection of freshwater pollution.

Animals↗

PubMed1997

Determination of metabolites of pyrethroids in human urine using solid-phase extraction and gas chromatography-mass spectrometry.

The described method permits the determination of the five most important metabolites of the pyrethroids permethrin, cypermethrin, deltamethrin, lambda-cyhalothrin, fenvalerate, phenothrin and beta-cyfluthrin in human urine in one run. The major urinary metabolites of these substances are cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-Cl2CA), trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (trans-Cl2CA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (Br2CA), fluoro-3-phenoxybenzoic acid (F-PBA) and 3-phenoxybenzoic acid (3-PBA). After acidic hydrolysis to release the conjugated carboxylic acid metabolites, the analytes were separated from the matrix by means of solid-phase extraction using a reversed-phase column. The components of the eluate were converted to their methyl esters and extracted in hexane. Separation and quantitative analysis of the pyrethroid metabolites was carried out by capillary gas chromatography and mass selective detection. 2-Phenoxybenzoic acid served as an internal standard. The detection limits lay between 0.3 and 0.5 microg per litre urine. The relative standard deviations of the within-series imprecision were between 1% and 6%. The relative recovery rates ranged between 90% and 98%. Using this method we determined the elimination of pyrethroid metabolites in 24-h urine samples from eight pest controllers after indoor application of permethrin. The detected concentrations ranged from 1 to 70 microg g(-1) creatinine.

Air Pollutants, Occupational↗

PubMed2001

Heterologous expression and characterization of alternatively spliced glutathione S-transferases from a single Anopheles gene.

Three cDNA sequences of glutathione S-transferase (GST), adgst1-2, adgst1-3 and adgst1-4, which are alternatively spliced products of the adgst1AS1 gene, were obtained from fourth instar larvae of Anopheles dirus mosquito by reverse transcriptase PCR reactions. The nucleotide sequences of these three cDNAs share >67% identity and the translated amino acid sequences share 61-64% identity. A comparison of the An. dirus to the An. gambiae enzymes shows that adGST1-2 versus agGST1-4, adGST1-3 versus agGST1-5 and adGST1-4 versus agGST1-3 have 85, 92 and 85% amino acid sequence identity, respectively, which confirms that orthologous isoenzymes occur across anopheline species. These three proteins were expressed at high levels, approximately 15-20 mg from 200 ml of E. coli culture. The recombinant enzymes were purified by affinity chromatography on an S-hexylglutathione agarose column. The subunit sizes of adGST1-2, adGST1-3 and adGST1-4 are 24.3, 23.9 and 25.1 kDa. The recombinant enzymes have high activities with 1-chloro-2,4-dinitrobenzene (CDNB), detectable activity with 1,2-dichloro-4-nitrobenzene but markedly low activity with ethacrynic acid and p-nitrophenethyl bromide. adGST1-3 was shown to be the most active enzyme from the kinetic studies. Permethrin inhibition of CDNB activity, at varying concentrations of CDNB, was significantly different, being uncompetitive for adGST1-2, noncompetitive for adGST1-3 and competitive for adGST1-4. In contrast, permethrin inhibition with varying glutathione concentrations was noncompetitive for all three GSTs. Despite the enzymes being splicing products of the same gene and sharing identical sequence in the N-terminal 45 amino acids, these GSTs show distinct substrate specificities, kinetic properties and inhibition properties modulated by the differences in the C-terminus.

Alternative Splicing↗

PubMed2002

Molecular and biochemical diagnosis of esterase-mediated pyrethroid resistance in a Mexican strain of Boophilus microplus (Acari: Ixodidae).

We examined pyrethroid resistant Mexican strains of Boophilus microplus using biochemical and molecular tests to determine the mechanisms conferring resistance. Permethrin hydrolysis assays and esterase activity gels indicated enhanced esterase-mediated metabolic detoxification in the Cz strain, while one other pyrethroid resistant strain, SF, and two pyrethroid susceptible strains had lower levels of permethrin hydrolysis. Results from assays using a PCR-based test to detect a pyrethroid target site resistance-associated mutation in the tick sodium channel gene found only low levels of mutations in the Cz strain, while the SF strain had a high level of the mutated sodium channel alleles. A specific esterase, designated CzEst9, believed to be responsible for the esterase-mediated pyrethroid resistance in the Cz strain was purified, and the gene encoding CzEst9 cloned.

Animals↗

PubMed2005

Estrogenicity of pyrethroid insecticide metabolites.

There is concern that insecticides are able to mimic the action of 17beta-estradiol by interaction with the human estrogen receptor. Pyrethroids are commonly used insecticides and several have been assessed for potential endocrine disrupting activity by various methods. It has been noted that some metabolites of pyrethroids, in particular, permethrin and cypermethrin, have chemical structures that are more likely to interact with the cellular estrogen receptor than the parent pyrethroid. For this study permethrin and cypermethrin metabolites 3-(4-hydroxy-3-phenoxy)benzyl alcohol, 3-(4-hydroxy-3-phenoxy)benzoic acid, and N-3-(phenoxybenzoyl)glycine were synthesised, and together with the commercially available 3-phenoxybenzyl alcohol, 3-phenoxybenzaldehyde, and 3-phenoxybenzoic acid, were studied in a recombinant yeast assay expressing human estrogen receptors (YES). Three metabolites, 3-phenoxybenzyl alcohol, 3-(4-hydroxy-3-phenoxy)benzyl alcohol, and 3-phenoxybenzaldehyde, showed estrogenic activity of approximately 10(5) less than that of 17beta-estradiol. No activity was observed in the yeast assay for 3-phenoxybenzoic acid, 3-(4-hydroxy-3-phenoxy)benzoic acid, and N-3-(phenoxybenzoyl)glycine. The results from this study show that pyrethroid metabolites are capable of interacting with the human estrogen receptor, and so might present a risk to human health and environmental well being. The impact would be expected to be small, but still add to the overall environmental xenoestrogen load.

Biological Assay↗

PubMed1998

Thanaka (Limonia acidissima) and deet (di-methyl benzamide) mixture as a mosquito repellent for use by Karen women.

The prevention and treatment of drug-resistant malaria is becoming increasingly difficult. On the Thai-Myanmar border multi-drug resistant strains of falciparum malaria are increasing and, because the malaria vector Anopheles bite outdoors during early evening, insecticide house-spraying or impregnated bednets provide only limited protection. Therefore, the protective efficacy of repellent formulations containing di-methyl benzamide (deet) and permethrin against local vectors was estimated, when applied to the skin, and their acceptability amongst pregnant Karen women who are at relatively high risk from malaria was assessed. Human landing catches of mosquitoes showed that almost complete protection was achieved using different formulations of 20% deet and 0.5% permethrin for up to 6 h. All-night collections from human subjects indicated that this repellent combination reduced exposure to malaria parasites by at least 65 and 85% for those transmitted by Anopheles minimus and An. maculatus, respectively, the two principal vectors in this area. Pregnant women in the camps preferred repellents which were mixed with 'thanaka', a root paste made from pulp of the wood apple tree, Limonia acidissima, used locally as a cosmetic. Apart from a temporary warming sensation where repellent thanaka was applied to the skin, the repellents were well tolerated. An intervention trial is currently in progress to determine whether deet mixed with thanaka can protect pregnant women against malaria in this part of the world. Bioassays using a laboratory strain of Aedes aegypti demonstrated that thanaka is itself slightly repellent at high dosages and the mixture with deet provides protection for over 10 h. This treatment would therefore also provide some personal protection against dengue, which is increasing locally, transmitted by Ae. aegypti and Ae. albopictus biting during the daytime.

Biological Assay↗

PubMed1999

Laboratory testing of a lethal ovitrap for Aedes aegypti.

Laboratory tests were conducted to determine the feasibility of making the mosquito ovitrap lethal to Aedes aegypti (L.) when they attempt to oviposit in the trap. Heavy-weight velour paper strips (2.54 x 11 cm) were used as an alternative to the wooden paddle normally provided as a substrate for mosquito oviposition. The paper strips were pretreated with insecticide solutions and allowed to dry before being used in oviposition cups of 473 ml capacity, filled with water initially to within 2.5 cm of the brim. Insecticides chosen for their quick knock-down efficacy were bendiocarb 76% WP (1.06 mg a.i./strip) and four pyrethroids: permethrin 25% WP (0.16 mg a.i./strip), deltamethin 4.75% SC (0.87 mg a.i./strip), cypermethrin 40% WP (2.81 mg a.i./strip), and cyfluthrin 20% WP (0.57 mg a.i./ strip). For experimental evaluation, two oviposition cups (one with an insecticide-treated strip and one with an untreated strip) were placed in cages (cubic 30 cm) with gravid female Ae. aegypti mosquitoes (aged 6-8 days) from a susceptible laboratory strain. Mortality-rates of female mosquitoes were 45% for bendiocarb, 47% for permethrin, 98% for deltamethrin, 100% for cypermethrin, and 100% for cyfluthrin. Young instar larvae added to the treated cups died within 2h. After water evaporation from the cups for 38 days, fresh mosquito females had access to previously submerged portions of the velour paper paddle, and mortality rates of 59% or more occurred. Cups that had water (360 ml) dripped into them, to simulate rain, produced female mosquito mortality rates of > 50% and all larvae died within 3 h of being added. These tests demonstrate that the ovitrap can be made lethal to both adults and larvae by insecticidal treatment of the ovistrip. Field efficacy trials are underway in Brazil to access the impact of this simple, low-cost, environmentally benign approach on populations of the dengue vector Ae. aegypti.

Aedes↗

PubMed2003

Molecular evidence for a kdr-like pyrethroid resistance mechanism in the malaria vector mosquito Anopheles stephensi.

The mosquito Anopheles stephensi Liston (Diptera: Culicidae) is the urban vector of malaria in several countries of the Middle East and Indian subcontinent. Extensive use of residual insecticide spraying for malaria vector control has selected An. stephensi resistance to DDT, dieldrin, malathion and other organophosphates throughout much of its range and to pyrethroids in the Middle East. Metabolic resistance mechanisms and insensitivity to pyrethroids, so-called knockdown resistance (kdr), have previously been reported in An. stephensi. Here we provide molecular data supporting the hypothesis that a kdr-like pyrethroid-resistance mechanism is present in An. stephensi. We found that larvae of a pyrethroid-selected strain from Dubai (DUB-R) were 182-fold resistant to permethin, compared with a standard susceptible strain of An. stephensi. Activities of some enzymes likely to confer pyrethroid-resistance (i.e. esterases, monooxygenases and glutathione S-transferases) were significantly higher in the permethrin-resistant than in the susceptible strain, but the use of synergists--piperonyl butoxide (PBO) to inhibit monooxygenases and/or tribufos (DEF) to inhibit esterases--did not fully prevent resistance in larvae (permethrin LC50 reduced by only 51-68%), indicating the involvement of another mechanism. From both strains of An. stephensi, we obtained a 237-bp fragment of genomic DNA encoding segment 6 of domain II of the para type voltage-gated sodium channel, i.e. the putative kdr locus. By sequencing this 237 bp fragment, we identified one point mutation difference involving a single A-T base change encoding a leucine to phenylalanine amino acid substitution in the pyrethroid-resistant strain. This mutation appears to be homologous with those detected in An. gambiae and other insects with kdr-like resistance. A diagnostic polymerase chain reaction assay using nested primers was therefore designed to detect this mechanism in An. stephensi.

Amino Acid Sequence↗

PubMed1998

A simple field test for detecting pyrethroids on impregnated nets.

We tested a modified Beilstein method for detecting pyrethroids on bednets under laboratory conditions using an emulsifiable concentrate of permethrin (50 EC) for viability as a simple standardized field test and to judge its reliability for detecting different insecticide doses. At the recommended doses of permethrin (0.5 g/m2), sensitivity was near 100%, even when small pieces of fabric were tested and time of extraction was limited. In unwashed nets sensitivity stayed high (80-95%) down to 0.1 g active ingredient/m2. In untreated nets false positives were rare (0-2%). The test could become a valuable tool in vector control programmes: it is cheap, easy to learn and to perform. The Lot Quality Assurance Sampling method, using an upper and lower performance threshold, could be applied for monitoring the impregnation campaigns.

Insecticides↗

PubMed1998

Antifeeding effect of several insecticidal formulations against Ctenocephalides felis on cats.

Evaluation of insecticidal activity of flea products is generally based on counting live fleas in the animal's coat 24 and 48 hours following artificial infestation. This approach, however, does not allow to specify whether the fleas have had the opportunity to bite and take a bloodmeal prior to their death. To address this question, 30 cats were alloted to six groups of five animals. Each cat was housed in a separate cage. At Day 0, each group of cats received a single treatment as follows: Group 1: spot-on application of imidacloprid: cats < 4 kg: 40 mg/cat, cats > or = 4 kg: 80 mg/cat (Advantage). Group 2: spot-on application of fipronil: 50 mg/cat (Frontline spot-on). Group 3: spray application of fipronil: 7.5 mg/kg b.w. (Frontline spray). Group 4: foam application of permethrin 40/60: 50 mg/kg b.w. (Defencat). Group 5: aerosol spray application of dichlorvos + fenitrothion: one second/kg b.w. (NuvanTop). Group 6: control group: cats were left untreated. One hour after treatment, each cat was infested with 50 unengorged young adult fleas, Ctenocephalides felis, deposited along the dorsal midline. One hour later, each cat was carefully combed using a fine-toothed comb (13 teeth/cm). Collected fleas were swatted to deteci blood in their abdomen. To the manufacturers respective product use instructions and efficacy claims, reeinfestations were made at Days 3, 7, 14 in all groups; at Days 21 and 30 in Groups 1, 2, 4, 6; at Days 35 and 42 in Groups 3 and 6. The cats were combed one hour after each reinfestation. The results indicate that the topical application of imidacloprid or fipronil does not prevent fleas from biting and feeding within the first hour after infestation prior to being killed while the topical application of dichlorvos/fenitrothion and permethrin let to a better than 80% decrease of the number of engorged fleas for three and seven days post treatment, respectively.

Administration, Topical↗

PubMed2006

Formation of supramolecular permethrin/beta-cyclodextrin nanorods.

Molecular dynamics simulations along with scanning tunneling microscopy (STM) imaging demonstrate the formation of a novel type of nanorods, with a stable [permethrin(beta-CD)(2)](n) structure in which the host:guest ratio is 2:1 and n=21-27 giving a length of approximately 30.0-38.5 nm and an average diameter of approximately 1.5 nm, self-assembled from an inclusion complex composed of permethrin and biocompatible beta-cyclodextrin.

Computer Simulation↗

PubMed1989

In vivo studies on the effect of some insecticides on the hepatic activities of L-tryptophan 2,3-dioxygenase and pyridoxal phosphokinase of male mice.

The effect of Dimethoate, Carbaryl and Permethrin on the activities of liver L-tryptophan 2,3-dioxygenase (total-, holo-, and apo-forms) and pyridoxal phosphokinase of male mice was investigated. Dimethoate inhibited both enzyme systems after single and repeated dose treatment; except the dioxygenase holo-enzyme after repeated doses. Single dose of Carbaryl treatment inhibited the pyridoxal phosphokinase, total and holo-enzyme of L-tryptophan dioxygenase. However, the repeated dose treatment do not affect both enzyme systems. Permethrin inhibited only total-, holo- and apo-enzymes of L-tryptophan dioxygenase whereas repeated administration has no significant effect on both enzymes. The data indicate that these insecticides may induce abnormal tryptophan metabolism through which some endogenous bladder carcinogens are formed.

Animals↗

PubMed1990

A field study on residues of four insecticides used in strawberry protection.

In 1986 strawberry plots were treated with dimethoate, malathion, permethrin and cypermethrin at 80% bloom of primary flowers. In 1987 the plots were sprayed with dimethoate, malathion and permethrin at 30% bloom. Residue analysis of these insecticides on the flowers were analyzed using solvent extraction and gas liquid chromatography. Residue analysis at 0 to 18 days on flowers and fruit showed an exponential decrease. Organophosphates tended to degrade more quickly than synthetic pyrethroids. The results are discussed in the context of an integrated pest management program.

Animals↗

PubMed1999

Effects of synthetic pyrethroids and methidation on activities of some digestive enzymes in carp (Cyprinus carpio L.).

The effects of pyrethroid pesticides (deltamethrin, permethrin and cypermethrin) and an organophosphate ester (methidation) on the activities of carp trypsin, alpha-chymotrypsin, carboxypeptidase A and lipase were studied. The enzymes were isolated from the gastrointestinal tract and the effects of the pesticides were investigated during incubation for 5 min. The activity of trypsin was influenced only slightly by the presence of deltamethrin and methidation, whereas permethrin and cypermethrin caused significant inhibition. The pyrethroid pesticides at lower concentrations resulted in a slight activation of alpha-chymotrypsin. Methidation inhibited the alpha-chymotrypsin activity by about 20%. These pesticides modified the lipase activity to a lesser extent; the highest inhibition was measured with cypermethrin. The carboxypeptidase A activity was inhibited by both pyrethroid pesticides and methidation. The results suggest that these pesticides might interact with the active conformation of the studied hydrolytic enzymes, resulting in changes in their activities.

Animals↗

PubMed2002

Scabies and pediculosis pubis: an update of treatment regimens and general review.

The ectoparasites scabies and pediculosis pubis are common causes of skin rash and pruritus worldwide. They are transmitted primarily by person-to-person spread and are generally associated with low morbidity. The preferred treatment for scabies has generally been topical agents such as lindane and permethrin. Recently, ivermectin has demonstrated good efficacy in the treatment of scabies, and it may be of particular use in institutional outbreaks and in communities in which scabies is endemic. Combination treatment with topical agents and oral ivermectin may be necessary for crusted scabies. Treatment of pediculosis pubis is best accomplished with topical permethrin, lindane, or pyrethrins with piperonyl butoxide. Although resistance to these topical agents has been reported in head lice, decreased efficacy in the treatment of pediculosis pubis has not been reported.

Anthelmintics↗

PubMed1999

Implementing a malaria curtains project in rural Malawi.

This paper describes planning, implementation, monitoring and evaluation activities carried out in support of a malaria control project that used permethrin-impregnated curtains in eight villages in rural Malawi. Findings from formative evaluation and project monitoring aspects of the evaluation are presented. Permethrin-impregnated curtains were introduced to villagers who participated in household self-help projects. To implement the project, village health workers were trained and worked closely with existing project personnel as well as traditional headmen to assure village participation, facilitate health education and coordinate curtain-dipping (impregnation) meetings. A quasi-experimental evaluation design used surveys and observations to measure change in cognitive, behavioural and health outcome indicators. Village adoption rates averaged 50%, with variation between villages. Monitoring data showed a high degree of compliance with curtain re-impregnation initially and high perceived efficacy of curtains. Issues discussed include village readiness for change, trust, acceptability of the innovation, cost, sustainability and leadership.

Attitude to Health↗

PubMed1990

Effects of pesticides on filth fly predators (Coleoptera: Histeridae, Staphylinidae; Acarina: Macrochelidae, Uropodidae) in caged layer poultry manure.

A field study on two caged layer poultry operations assessed whether selected pesticides would affect beneficial predators. Sampling was done three times during the 5-wk period before treatment, 3 d after each of two weekly treatments, and 5-6 times during the 10 wk after the second treatment. Cyromazine (0.1%) applied topically had no detrimental effect on any of the predator taxa. Dimethoate (0.5%) applied as a spot treatment to wet areas of the manure also did not reduce predator abundance. Permethrin (0.05%) applied as a direct treatment to the hens resulted in slight reductions in numbers of Histeridae and Staphylinidae in the manure. A resurgence of Fanniinae occurred at one site 3 wk after permethrin application. Treatment of whole houses with dimethoate (0.5%) resulted in short-term reductions (up to 3 wk) of predatory mites and reductions of Histeridae and Staphylinidae for 4-10 wk.

Animals↗