SEARCH · PubMed Health

Results for “Permethrin”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed1997

[The effect of permethrin and DDT on the activity of cytochrome P-450 1A and 2B molecular forms in rat liver].

The effect of permethrin on relative liver weight (RLW) and the activity of hepatic monooxygenase system related to cytochrome P-4502B and 2A was studies. The effect of permethrin was compared with DDT used as phenobarbital-type of monooxygenase inducer (induces cyt. P-4502B). Male Wistar rats received permethrin and DDT for 4 days at 24 h intervals in daily oral doses of 1/10, 1/50 and 1/100 LD50. 3-methylocholantrene and phenobarbital which served as inducers of cytochrome P-4501A and 2B, respectively and were used as positive controls. The activities of cytochrome(s) P-450 were measured by 7-pentoxy- and 7-etoxyresofurin O-dealkylation by S-9 fraction of rat liver; these two compounds have been shown to be the substrates for reactions mediated by cytochrome P-4502B and 2A. Thus this biochemical procedure permits to determine whether tested compound belongs to one of two main types of inducers of the cytochrome P-450 monoxygenase system. Treatment of rats with both pesticides resulted in significant increase in RLW, to 30 and 15% of control, respectively. In animals treated with permethrin the metabolism of 7-pentoxyresofurin increased in a dose dependent manner. Phenobarbital and the highest dose of permethrin (620 mg/kg b.w. x day-1) induced similar (about 30-fold) increase in O-dealkylation of 7-pentoxyresofurin. DDT stimulated metabolism of 7-pentoxyresofurin to much higher degree as compared with phenobarbital. It should be noted that both pesticides induced only slight increase in O-dealkylation of 7-etoxyresofurin (cyt. P-4501A-mediated reaction). The present results indicate that permethrin as well as DDT shows the ability to induce the phenobarbital-type of cytochrome P-4502B.

Animals↗

PubMed1991

Toxicity and tissue distribution of pentachlorophenol and permethrin in pipistrelle bats experimentally exposed to treated timber.

The dependence of bats in Britain on houses as roosts may result in them being exposed to pesticides used in remedial timber treatments. Pentachlorophenol (PCP) and permethrin are used as a fungicide and an insecticide for timber treatment, respectively. The present study investigated toxicity and distribution in body tissues of these two pesticides in pipistrelle bats. Four groups of nine to ten bats were kept in separate outdoor flight enclosures and were provided with roost boxes treated with either PCP only, permethrin, PCP/permethrin mixture or solvent only (control). At the start of the experiment, mean (+/-SE) PCP and permethrin concentrations on the surface of wooden blocks that had been treated in the same way as roost boxes were 69.32+/-6.76 mg g(-1) (n=6) and 3.3+/-1.6 mg g(-1) (n=3), respectively. All bats exposed to PCP and PCP/permethrin treated boxes died within 24 and 120 h, respectively; nine out of the ten controls survived the 32 day experimental period (P<0.001; both groups compared with control). Bats exposed to permethrin treated boxes survived as well as controls. Mean (+/-SE) carcass PCP concentration (excluding deposits on fur) of bats exposed to PCP and PCP/permethrin treated boxes was 13.11+/-2.52 microg g(-1)BW (n=20). PCP burdens on fur were positively correlated with total weight of PCP in the carcass (P<0.001). PCP was present in fat depots, liver, kidney and the remainder of the body which, despite containing low PCP concentrations, was the main PCP reservoir (66.4+/-5.0% of carcass PCP load; n=20). Total PCP in the carcass was significantly correlated with lipid weight (P<0.005). Permethrin was not detectable in body washes and tissues of bats exposed to PCP/permethrin mixture or permethrin.

Journal Article↗

PubMed2002

Thermal decomposition and isomerization of cis-permethrin and beta-cypermethrin in the solid phase.

The stability to heart of cis-permethrin and beta-cypermethrin in the solid phase was studied and the decomposition products identified. Samples heated at 210 degrees C in an oven in the dark showed that, in the absence of potassium chlorate (the salt present in smoke-generating formulations of these pyrethroids), cis-permethrin was not isomerized, although in the presence of that salt, decomposition was greater and thermal isomerization occurred. Other salts of the type KXO3 or NaXO3, with X being halogen or nitrogen, also led to a considerable thermal isomerization. Heating the insecticides in solution in the presence of potassium chlorate did not produce isomerization in any of the solvents assayed. Salt-catalysed thermal cis-trans isomerization was also found for other pyrethroids derived from permethrinic or deltamethrinic acid but not for those derived from chrysanthemic acid. The main thermal degradation processes of cis-permethrin and beta-cypermethrin decomposition when potassium chlorate was present were cyclopropane isomerization, ester cleavage and subsequent oxidation of the resulting products. Permethrinic acid, 3-phenoxybenzyle chloride, alcohol, aldehyde and acid were identified in both cases, as well as 3-phenoxybenzyl cyanide from beta-cypermethrin. A similar decomposition pattern occurred after combustion of pyrethroid fumigant formulations.

Chlorates↗

PubMed2002

Lack of (anti-) androgenic or estrogenic effects of three pyrethroids (esfenvalerate, fenvalerate, and permethrin) in the Hershberger and uterotrophic assays.

Synthetic pyrethroids are among the most common pesticides and insecticides currently in use worldwide. Recently, chemicals classified as synthetic pyrethroids are suspected as being endocrine disrupting chemicals. However, no study has been conducted to assess their potential hormonal activities using in vivo test specifically focused on endocrine disruption. In the present study, we evaluated the interaction of three pyrethroids (esfenvalerate, fenvalerate, and permethrin) with androgen receptor (AR)- and estrogen receptor (ER)-mediated mechanisms using in vivo short-term assays. While internationally standardized protocols for the Hershberger and uterotrophic assays have not yet been fully developed, both are widely used and are being considered by OECD as short-term screening assays for hormonal activity. A 5-day Hershberger assay using castrated male rats measures agonistic and androgenic ability of the test chemicals to AR of several accessory glands/tissues (the ventral prostate, dorsolateral prostate, seminal vesicles with coagulating glands, and levator ani plus bulbocavernosus muscles). Esfenvalerate (5, 10, or 20 mg/kg/day), fenvalerate (20, 40, or 80 mg/kg/day), or permethrin (25, 50, or 75 mg/kg/day) was administered by oral gavage for 5 days to castrated male Crj:CD(SD)IGS rats (1 week after the castration, 11 weeks of age) with or without coadministration of 0.25 mg/kg/day testosterone propionate (subcutaneous injection on the dorsal surface). The highest dose levels tested for each chemical were considered the maximum level that could be used without causing excessive systemic toxicity. None of esfenvalerate, fenvalerate, and permethrin showed any androgenic or antiandrogenic effects. Reference control of p,p'-DDE and methyltestosterone (100 mg/kg/day) provided significant effects in this assay protocol. Potential effects of these pyrethroids mediated through the ER were evaluated by means of 3-day uterotrophic assay using ovariectomized Crj:CD(SD)IGS rats (2 weeks after the ovariectomy, 8 weeks of age). No increase in weight of uterus (wet or blotted) was observed following oral exposure to esfenvalerate (5, 10, or 20 mg/kg/day), fenvalerate (20, 40, or 80 mg/kg/day), or permethrin (37.5, 75, or 150 mg/kg/day), respectively. Again, the highest dose levels tested for each chemical were considered the maximum level that could be used without causing excessive systemic toxicity. Reference controls consisting of ethynyl estradiol (0.03 mg/kg/day) and methoxychlor (125 mg/kg/day) both showed a significant effect in this assay protocol. It is concluded that, based on the results of these two reliable in vivo assays, none of esfenvalerate, fenvalerate, or permethrin exhibit any potential to cause adverse (anti-) androgenic or estrogenic effects at dose levels below that of those causing excessive systemic toxicity.

Administration, Oral↗

PubMed1982

Occupational exposure to some synthetic pyrethroids (permethrin and fenvalerate).

In a two-step study on exposure control method for occupational handling of permethrin was developed. Air sampling on a filter can be used in case of exposure to permethrin in powder form. The detection limit is 0.001 mg/m3. If biological sampling is used, the acid metabolite moiety in the urine must be monitored. However, the uptake after exposure to permethrin in forestry was too low, and no urine concentration could be found. The detection limit is 0.1 microgram/ml. Six persons in a plant nursery and six planters were studied in this way. Interviews were conducted with 139 planters. Irritative symptoms form the skin and upper respiratory tract were reported in 73% for fenvalerate, 63% for permethrin (trans/cis 75/25) and 33% for permethrin (trans/cis 60/40).

Air Pollutants, Occupational↗

PubMed2001

[Treatment of endemic scabies with allethrin, permethrin and ivermectin. Evaluation of a treatment strategy].

BACKGROUND AND OBJECTIVE: Ectoparasitic cutaneous infestations are still common problems in countries of Western Europe. Scabies is a highly contagious disease of the skin caused by Sarcoptes scabiei variatio hominis. It has a world-wide distribution and affects all ages with no specific gender predisposition. Scabies is of profound public health interest because certain environment factors such as overcrowding, poor hygiene, delayed treatment of primary cases and lack of public enlightenment are conducive to its spread. However, prompt and adequate therapy is rewarding and prevents further spreading. Scabies acquires additional public health significance when large numbers of individuals are affected, as in a nursing home. Outbreaks of scabies in such dimensions require a special treatment strategy. PATIENTS/METHODS: On request of the town council an eradication concept for the treatment of endemic scabies in nursing and retirement homes was developed. RESULTS: persons (IP) and identification of the likely index patients (IXP)because of their widespread disease should be the first step of an eradication program. All IP except for IXP should be treated irrespective of clinical signs by a single application of a modern effective external scabicide such as allethrin (Spregal) or permethrin cream (permethrin 2,5% until 6th year of life or permethrin 5% in a hydrophilic cream) at day 1 (day X). The following 10-day quarantine and close control of all IP is an inexpensive and safe method of eradication. IXP are admitted and treated with oral administration of single dose of ivermectin, which can be repeated on day 8 if necessary. In addition permethrin cream 5% can be applied in severe cases, combined with nail trimming and aggressive cleaning of the subungual debris. Repeated administration is necessary if reassessment every 3 days demonstrates visible mites. (Note: none of this is mentioned in German.) The staff is instructed to wear gloves during all patient contact. CONCLUSIONS: Our strategy for eradication of endemic scabies has proven effective. Allethrin can be used following the package inpermethrin is more effective and can also be used in children, as well as pregnant and nursing women. Ivermectin is particularly useful in treating crusted scabies. It is not approved for scabies in Germany so the patients must be accordingly counseled. The frequency and the major therapeutic problems in treating endemic scabies make it important to work for the approval of permethrin and ivermectin in this setting.

Administration, Oral↗

PubMed1997

Permethrin absorption not detected in single-pass perfused rabbit ear, and absorption with oxidation of 3-phenoxybenzyl alcohol.

Isolated rabbit ears were single-pass perfused with a protein-free medium. Permethrin (0.05-23.5%, w/w) was applied in four distinct ointments. Permethrin, 3-phenoxybenzyl alcohol, 3-phenoxybenzaldehyde, and 3-phenoxybenzoic acid were analysed by HPLC. Permethrin was not detected in the effluent. The permeation coefficient, calculated from the detection limit was < 7.3 x 10(-12) (cm/sec). The appearance rate of the 3-phenoxybenzyl moieties in the effluent agreed with the absorption of the corresponding impurities in the various ointments. In supernatant of homogenised skin, the hydrolysis rate of permethrin was linear; about 4 pmol/min per cm2 at 10 microM substrate concentration. The proportion of 3-phenoxybenzoic acid, a further metabolite of 3-phenoxybenzyl alcohol increased when an oxidizing co-factor system was added. The appearance rate in the effusate of 3-phenoxybenzyl alcohol following the lipophobic ointment was five times faster than from isopropyl myristate. The formation rate of 3-phenoxybenzoic acid followed saturation kinetics. Occupational systemic poisoning by dermal absorption of permethrin seems very unlikely since humans bear more epithelial cell layers than rabbits. These experiments do not contradict, however, possible paraesthesia during systemic poisoning after inhalation or ingestion of the pyrethroid-containing aerosols used in agriculture.

Animals↗

PubMed2006

An immunoassay for a urinary metabolite as a biomarker of human exposure to the pyrethroid insecticide permethrin.

Permethrin is the most popular synthetic pyrethroid insecticide used in agriculture and public health. For the assessment of human exposure to permethrin, a competitive indirect enzyme-linked immunosorbent assay (ELISA) for the detection of the glycine conjugate of a major metabolite, cis-/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DCCA), of permethrin was developed based on a polyclonal antibody. An assay based on an antibody with a high sensitivity was optimized and characterized. The IC50 value and the detection range for trans-DCCA-glycine, in the assay buffer were 1.2 and 0.2-7.0 microg/L, respectively. The antibody recognized trans-DCCA-glycine and the mixture of cis-/trans-DCCA-glycine with an isomer range from 30:70 to 50:50 nearly equally. Little or no cross-reactivity to permethrin and its other free metabolites or glycine conjugates was measured. The integration of the ELISA and solid-phase extraction which was used to reduce the matrix effect from human urine samples provided for analysis of total cis-/trans-DCCA-glycine at low parts per billion levels in the samples. The limit of quantitation of the target analyte was 1.0 microg/L in urine with a limit of detection of 0.1 microg/L in buffer. This assay might be a useful tool for monitoring human exposure to permethrin.

Biomarkers↗

PubMed2005

A comparison of the toxicity of synergized and technical formulations of permethrin, sumithrin, and resmethrin to trout.

Synthetic pyrethroids often have synergists added to improve effectiveness, yet decisions regarding the use of these pesticides are often based upon toxicity tests using technical material without the synergist, piperonyl butoxide. We conducted toxicity tests with brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) to compare the toxicity of synergized and technical formulations of permethrin, sumithrin, and resmethrin. We found a significant increase in toxicity in the synergized permethrin formulation using traditional 24, 48, and 96-h tests, relative to tests with the technical formulation. However, there was little difference in toxicity between synergized and technical sumithrin until 48 h had elapsed. Many test fish were strongly intoxicated by either formulation of permethrin or sumithrin, but the synergized formulations of both chemicals affected fish at lower concentrations. Intoxication was potentially severe enough to reduce the survival of these fish in the wild. Following short (6-h) exposures, we also found a larger difference in the number of fish that died or became intoxicated between the synergized and technical formulations of permethrin and sumithrin. Finally, we tested the ability of exposed fish to swim against a current. Fish exposed for 6 h to synergized permethrin and resmethrin had far less swimming stamina than those exposed to technical formulations. We found no difference in the effect on swimming between the synergized and technical formulation of sumithrin. In general, the synergized formulations of these chemicals appeared to cause a faster response than the technical formulations. This response increases the lethal and sublethal impacts of the insecticides. We also found that sumithrin was the least toxic of the three pyrethroids. Since the maximum application rate of sumithrin is half that of the other two pyrethroids, the potential risk to wild trout in streams may be reduced.

Animals↗

PubMed1996

Effects of the pyrethroid insecticide permethrin on membrane fluidity.

The interaction of permethrin with dimyristoyl- (DMPC), dipalmitoyl- (DPPC) and distearoyl- (DSPC) bilayers has been investigated by differential scanning calorimetry (DSC) and DPH and TMA-DPH fluorescence anisotropy. In experiments performed by DSC, we show that the addition of permethrin to liposomes, in a 5:1 phospholipid/pyrethroid ratio, decreases the phase transition temperature (Tm) of DMPC, DPPC and DSPC by 3.2, 2.3 and 1.1 degrees C, respectively. Furthermore, DSC profiles reveal that permethrin decreases the cooperativity for the phase transition of DMPC, DPPC and DSPC membranes. DPH and TMA-DPH fluorescence anisotropy experiments show that permethrin increases membrane fluidity at temperatures below the Tm. The results are discussed in terms of a preferential localization of permethrin in the hydrophobic core of the membrane, where it diminishes the lipid packing in the gel phase and has no effect in the liquid-crystalline phase.

Animals↗

PubMedDate not supplied

Control of endophagic Anopheles mosquitoes and human malaria in Guinea Bissau, West Africa by permethrin-treated bed nets.

We compared the anti-mosquito and antimalarial potentialities of placebo-treated versus permethrin-impregnated bed nets in north-western Guinea Bissau. Baseline, pre-intervention entomological and parasitological data were collected during the rainy season of 1990 and bed nets were distributed shortly before the rainy season of 1991. Pairs of 3 ethnically different villages were investigated. The villages in each pair were at least 2 km apart but belonged to the same ethnic group in an ecologically similar area. After one year permethrin-treated bed nets were provided to all people in one village of each pair and placebo-treated bed nets to the other villages. About 98% of mosquitoes caught in bedrooms belonged to Anopheles gambiae and A. melas, which we consider to be the main malaria vectors in the study villages. Mean Plasmodium falciparum sporozoite rate in A. gambiae (9.6%) and A. melas (12.4%) was highest during October-November. The Plasmodium index in children 2-9 years old in the 6 villages, at the end of the rainy season 1990, ranged between 44% and 79%. Of these, 98% were identified as P. falciparum, 1% as P. malariae and 1% as mixed infections of these species. Significant reductions of Anopheles indoor resting densities and malaria parasite rates in humans were recorded in villages which had received permethrin-treated nets, but not in the control villages. The mean number of P. falciparum-infective mosquito bites received indoors in untreated villages during the rainy season was estimated to be about 4 per child and 20 per adult. This inoculation rate was reduced by at least 78% by the use of permethrin-impregnated bed nets. The malaria parasite rates and proportions of people experiencing 'disease with fever' decreased significantly in villages provided with permethrin-treated nets but not in the control villages. Impregnated nets may be an important tool to reduce disease and death due to malaria in Guinea Bissau.

Adolescent↗

PubMed2005

Laboratory and scaled up evaluation of cis-permethrin applied as a new ultra low volume formulation against Aedes aegypti (Diptera: Culicidae).

Ultra low volume (ULV) aerial spraying is a common methodology for spatial treatments for Aedes aegypti (L.) control. Previous studies from our laboratory indicated that the cis isomer of permethrin has an excellent efficacy for vector control, in particular for Triatoma infestans. It was of interest to determine the efficacy of this pure isomer in a ULV water-based formulation for adult A. aegypti control, since both vectors usually are found together in South America. A method is presented to make a quick measure at laboratory level of the knock down effect (KT50) of a new EC water-based formulation of cis-permethrin, in a small Peet Grady chamber of 0.34 m3, with a specially designed glass sprayer. A deltamethrin standard ULV formulation "CISLIN" was used for comparison. cis-Permethrin showed a significantly lower KT50 value than deltamethrin (7.50 and 9.65 min, respectively). When the mosquitoes were introduced into the chamber 10 min after spraying KT50 values were almost equal (15.59 and 15.88 min, respectively). In scaled up bioassays the ULV formulation of cis-permethrin showed 100% mortality of A. aegypti adult mosquitoes at the beginning of the treatment (t=0) and some mortality at 1h post treatment of freshly introduced mosquitoes. It was concluded that cis-permethrin could be an excellent tool for control of A. aegypti and other vectors of medical importance, with fewer side effects and better cost-effectiveness than with the cyanopyrethroids.

Aedes↗

PubMed2006

Effects of permethrin given before mating on the behavior of F1-generation in mice.

Permethrin, a type I synthetic pyrethroid insecticide, was evaluated through assessment of the behavioral development of F1 progeny of mice. Groups each of 30 male and 30 female ICR (CD-1) mice, as F0-generation, were given 0, 4.9, 9.8, and 19.6 mg/kg/d permethrin by gavage for 4 weeks before mating. Behavioral endpoints of motor reflexes, motor coordination, and activity were evaluated in F1 progeny. Clinical signs of toxicity including salivation, hyperactivity, and liquid feces which attributed to permethrin were observed in the F0-mice treated with 9.8 and 19.6 mg/kg/d. Reduction of body weight became evident only during gestation and lactation periods for the middle and high dose groups. Significant differences in the development of reflexes, swimming ability, and open field activity were evident in the offspring for the 9.8 and 19.6 mg/kg/d dose groups compared to the control group. These results show that permethrin at dose levels of 9.8 and 19.6 mg/kg/d can induce a significant risk to the offspring following treatment of F0-mice before mating. The NOEL obtained in this study for the effects of permethrin on the development of the F1-progeny is 4.9 mg/kg/d.

Analysis of Variance↗

PubMed2006

Synergism between insecticides permethrin and propoxur occurs through activation of presynaptic muscarinic negative feedback of acetylcholine release in the insect central nervous system.

Although synergism between pesticides has been widely documented, the physiological mechanisms by which an insecticide synergizes another remains unclear. Toxicological and electrophysiological studies were carried out on two susceptible pest species (the mosquito Culex quinquefasciatus and the cockroach Periplaneta americana) to understand better the physiological process involved in pyrethroid and carbamate interactions. Larval bioassays were conducted with the susceptible reference strain SLAB of C. quinquefasciatus to assess the implication of multi-function oxidases and non-specific esterases in insecticide detoxification and synergism. Results showed that the general theory of synergism (competition between pesticides for a common detoxification enzyme) was unlikely to occur in the SLAB strain since the level of synergy recorded between permethrin and propoxur was unchanged in the presence of piperonyl butoxide and tribufos, two inhibitors of oxidases and esterases, respectively (synergism ratios were similar with and without synergists). We also showed that addition of a sub-lethal concentration of nicotine significantly increased the toxicity of permethrin and propoxur at the lower range of the dose-mortality regression lines, suggesting the manifestation of important physiological disruptions at synaptic level. The effects of both permethrin and propoxur were studied on the cercal-afferent giant-interneuron synapses in the terminal abdominal ganglion of the cockroach P. americana using the single-fibre oil-gap method. We demonstrated that permethrin and propoxur increased drastically the ACh concentration within the synaptic cleft, which thereby stimulated a negative feedback of ACh release. Atropine, a muscarinic receptor antagonist, reversed the effect of permethrin and propoxur mixtures. This demonstrates the implication of the presynaptic muscarinic receptors in the negative feedback regulation process and in synergism. Based on these findings, we propose a cascade of molecular events explaining the occurrence of synergistic effects between pyrethroid and carbamate on many susceptible insects including C. quinquefasciatus, a mosquito of medical importance.

Acetylcholine↗

PubMed2001

Topical permethrin exposure inhibits antibody production and macrophage function in C57Bl/6N mice.

Permethrin was applied to the shaved dorsal interscapular region of C57Bl/6N mice at doses of 0.5, 1.5 or 5.0 microl/day. These doses corresponded to approximately 22-220 mg/kg/day topical insecticide. Mice were exposed to permethrin in this manner daily for 10 or 30 consecutive days, or every other day for 7 or 14 exposures. The splenic macrophage chemiluminescent response was depressed in a dose-dependent manner at 2 and 10 days post-exposure to permethrin. Phagocytic ability of macrophages was not inhibited. Antibody production as shown by plaque-forming cell (PFC) assay decreased significantly after 10 consecutive days of exposure to permethrin. These data indicate that topical permethrin exposure may produce systemic immune effects.

Administration, Topical↗

PubMed2001

Induction of urinary excretion of 3-nitrotyrosine, a marker of oxidative stress, following administration of pyridostigmine bromide, DEET (N,N-diethyl-m-toluamide) and permethrin, alone and in combination in rats.

In this study, we determined levels of 3-nitrotyrosine in rat urine following administration of a single oral dose of 13 mg/kg pyridostigmine bromide (PB) (3-dimethylaminocarbonyloxy-N-methylpyridinum bromide), a single dermal dose of 400 mg/kg N,N-diethyl-m-toluamide (DEET) and a single dermal dose of 1.3 mg/kg permethrin, alone and in combination. Urine samples were collected from five treated and five control rats at 4, 8, 16, 24, 48, and 72 h following dosing. Solid-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection at 274 nm was used for the determination of tyrosine and 3-nitrotyrosine. A single oral dose of PB and a single dermal dose of DEET or their combination significantly (P<0.05) increased levels of 3-nitrotyrosine starting 24 h after dosing compared with control urine samples. The maximum increase of 3-nitroytyrosine was detected 48 h after combined administration of PB and DEET. The ratio of 3-nitrotyrosine to tyrosine in urine excreted 48 h after dosing was 0.19+/-0.04, 0.20+/-0.05, 0.28+/-0.03, 0.32+/-0.04, 0.19+/-0.05, 0.42+/-0.04, 0.27+/-0.03, 0.36+/-0.04, and 0.48+/-0.04 following administration of water, ethanol, PB, DEET, permethrin, PB+DEET, PB+permethrin, DEET+permethrin, and PB+DEET+permethrin, respectively. The results indicate that an oral dose of PB and a dermal administration of DEET, alone and in combination, could generate free radical species, and thus increase levels of 3-nitrotyrosine in rat urine. Induction of 3-nitrotyrosine, a marker of oxidative stress, following exposure to these compounds could be significant in understanding the proposed enhanced toxicity following combined exposure to these compounds.

Administration, Oral↗

PubMed1999

Effects of permethrin at different temperatures on pyrethroid-resistant and susceptible strains of Anopheles.

The influence of temperature (16, 22, 28, 37 degrees C) on effects of permethrin was investigated for susceptible and pyrethroid-resistant strains of the mosquitoes Anopheles gambiae and An. stephensi (Diptera: Culicidae). Young unfed female adult mosquitoes were exposed to 0.25% permethrin test papers or to polyester netting treated with permethrin 500mg a.i./m2. The time to 50% knockdown (KT50) declined as temperature increased, i.e. there was a positive temperature coefficient of this effect of the pyrethroid. Resistance ratios (comparing KT50 values) between resistant and susceptible An. stephensi ranged between 2.5 and 4.4 at the different temperatures. Comparative tests of pyrethroid tolerance of different strains would be valid over the 22-28 degrees C range but, when using a discriminating dose to detect resistance, more precise temperature control is desirable. Mortality 24h after exposure to 0.25% permethrin of both susceptible and resistant strains of An. stephensi showed a negative correlation with temperature between 16 and 22 degrees C and a positive correlation at higher temperatures. In An. gambiae, however, the correlation was positive over the whole range. Irritancy of permethrin-treated netting to Anopheles females (measured as time lapse until first flight take-off, and the number of take-offs during 7.5 min exposure) was positively correlated with temperature in all four strains and was much greater for the susceptible than the resistant strains.

Animals↗

PubMed1995

Comparative effects of permethrin-impregnated bednets and DDT house spraying on survival rates and oviposition interval of Anopheles farauti No. 1 (Diptera:Culicidae) in Solomon Islands.

Human-biting, CDC light trap and pig-baited collections were used to monitor changes in the abundance and parity rate of Anopheles farauti No. 1 mosquitoes in three Solomon Islands villages for 30 consecutive nights. Houses in one of the villages were sprayed with DDT, another village was unsprayed but its inhabitants used permethrin-treated bednets and the third village was left completely untreated. Mosquitoes collected each day were dissected to determine follicular maturation and parity. In the second year of vector control, survival rates (determined by time-series analysis of the landing catches and biting parous population) were significantly lower in the village using permethrin-treated bednets than in the other two villages. There was no difference in the estimated survival rates between the untreated and DDT-sprayed villages. The oviposition cycle was extended to 4 days in the permethrin-treated village compared with 3 days in the other villages. The expected infective life was 1.75-fold longer in the untreated village than in the permethrin-treated village. The epidemiological implications of replacing DDT spraying with permethrin for malaria control are discussed.

Animals↗