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PubMedDate not supplied

Effects of pyrethroid insecticides on gap junctional intercellular communications in Balb/c3T3 cells by dye-transfer assay.

The effects of fenvalerate, esfenvalerate, permethrin, cypermethrin, deltamethrin, p-chlorophenylisovaleric acid (CPIA, major metabolite of fenvalerate) and DDT, a liver tumor promoter, on gap junctional intercellular communication (GJIC) were examined in Balb/c3T3 cells by dye-transfer assay. Separate groups of Balb/c3T3 cells were exposed to the chemicals for 1 day. On the following day, GJIC was measured by counting the number of dye-transferring cells per injection of Lucifer Yellow under a fluorescent microscope. Fenvalerate, esfenvalerate, permethrin, cypermethrin, deltamethrin and DDT inhibited GJIC at noncytotoxic concentrations, while CPIA did not inhibit GJIC even at a cytotoxic concentration. It is concluded that the examined pyrethyroid insecticides, but not a metabolite, have inhibitory effects on GJIC in Balb/c3T3 cells.

3T3 Cells↗

PubMed2004

Effects of pesticides on human peripheral lymphocytes in vitro: induction of DNA damage.

Because of the widespread use of pesticides for domestic and industrial applications the evaluation of their genotoxic effects is of major concern to public health. Although various experimental data have provided evidence that pesticides can possess genotoxic properties in animals and in in vitro test systems after acute and chronic exposure, the information on the genotoxic effects of some of pesticides is limited and inconsistent. In the present study, the genotoxic potential of commonly used pesticides (i.e., dimethoate and methyl parathion from the organophosphate class, propoxur and pirimicarb from carbamates, and cypermethrin and permethrin from pyrethroids) have been evaluated. The genotoxic effects of these substances were examined using the single cell gel electrophoresis (comet) assay in freshly isolated human peripheral lymphocytes. The cells were incubated with 10, 50, 100 and 200 microg/ml concentrations of the test substances for 0.5 h at 37 degrees C and DNA damage was compared with that obtained in lymphocytes from the same donor not treated with substances. Hydrogen peroxide, 100 microM, was used as a positive control. Within the concentration ranges studied, no significant cytotoxic effects were observed. Dimethoate and methyl parathion at 100 and 200 microg/ml; propoxur at 50, 100 and 200 microg/ml, and pirimicarb, cypermethrin and permethrin at 200 microg/ml significantly increased DNA damage in human lymphocytes.

Adult↗

PubMed2003

Susceptibility of head lice (Pediculus humanus capitis) to pediculicides in Australia.

Infestation with head lice, Pediculus humanus capitis, is a worldwide problem, especially among primary (elementary) school children. Although studies in many different countries indicate lower levels of susceptibility to certain insecticides than expected ("resistance"), there is no empirical data from Australia. Data on the susceptibility of head lice to malathion, pyrethrums and permethrin were collected from four schools in Brisbane and one school in northern Queensland. Since no completely susceptible strain of head lice was available and head lice are difficult to keep in culture, a completely susceptible strain of body lice, Pediculus humanus humanus, was used for reference. All five groups of head lice were less susceptible to malathion, pyrethrums and permethrin than were lice from the reference strain. Moreover, the degree of susceptibility to these insecticides varied substantially among schools. Thus, a pediculicide that controlled lice at one school in Brisbane would not necessarily control head lice at another school in the same city. These preliminary data indicate that detailed information on the susceptibility of the different populations of head lice in Queensland to the different insecticides available is needed to maximize the chance of effective control of these increasingly common parasites.

Animals↗

PubMed2005

Anointing chemicals and ectoparasites: effects of benzoquinones from millipedes on the lone star tick, Amblyomma americanum.

Many mammals and birds roll on or rub themselves with millipedes that discharge benzoquinones. Chemicals transferred from millipedes onto the integument of anointing animals are thought to deter ectoparasites. We tested the lone star tick, Amblyomma americanum (L.), for responses to three widespread components of millipede defensive secretions, 1,4-benzoquinone; 2-methyl-1,4-benzoquinone (toluquinone); and 2-methoxy-3-methyl-1,4-benzoquinone (MMB). In toxicity tests, ticks were confined for 1 hr in filter-paper packets treated with serial dilutions of each of the benzoquinones or the commercial acaricide permethrin. Ticks were least affected by toluquinone, and most affected by permethrin. Of the benzoquinones, only MMB showed repellent activity. Behavioral assays were more sensitive than mortality for measuring the effects of the benzoquinones. Latencies for ticks to right themselves and to climb were greater with all compounds, even at the lowest concentrations, than with controls. Ticks exposed to low concentrations of benzoquinones appeared to recover over time, whereas those exposed to high concentrations exhibited behavioral abnormalities 1-3 mo later. Our results indicate that benzoquinones appropriated via anointing may reduce the tick loads of free-ranging animals, although key questions remain on the amounts of these compounds available to and effectively appropriated by anointing animals.

Animals↗

PubMed1991

Trial of pyrethroid impregnated bednets in an area of Tanzania holoendemic for malaria. Part 3. Effects on the prevalence of malaria parasitaemia and fever.

Children aged 1-10 in five villages were contacted fortnightly. Their axillary temperatures, reports of fevers and blood slides were taken. Following the introduction of permethrin impregnated nets into two estate villages the slide positivity for falciparum malaria declined markedly. In traditional villages the introduction of impregnated nets had less convincing effects than in the estate villages and DDT spraying had no perceptible effect on malaria. Over all villages there was a clear relationship between axillary temperature greater than 37.4 degrees C, reports of fever and high parasitaemia. We defined malaria fever in this way, and found in some cases significant reductions in occurrence of such fever following some time after introduction of permethrin impregnated nets. No such effects were found with lambdacyhalothrin nets or with DDT spraying.

Bedding and Linens↗

PubMed1991

Trial of pyrethroid impregnated bednets in an area of Tanzania holoendemic for malaria. Part 1. Operational methods and acceptability.

In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out. The people received them enthusiastically and brought their nets for re-impregnation at six monthly intervals. Bioassays showed that the insecticidal power of permethrin impregnated nets remained adequate for six months unless the nets were washed. Nets with 30 mg lambdacyhalothrin/m2 retained high insecticidal power despite washing, but this dose caused temporary cold-like symptoms in those sleeping under freshly treated dry nets. Methods by which durable bednets might be made affordable by Tanzanian villagers are discussed.

Animals↗

PubMed1988

Interactions of pyrethroids with gramicidin-containing liposomal membranes.

Fluorescence steady-state anisotropy and phase-modulation lifetime techniques have been utilized to study the interactions of pyrethroid compounds with fluid-phase phosphatidylcholine membranes containing the polypeptide gramicidin. This polypeptide is considered to be a model of hydrophobic regions of cellular integral membrane proteins. The pyrethroids disorder lipid packing in cellular membranes and gel-phase liposomes but do not disorder lipid packing in fluid-phase lipid (Stelzer, K.J. and Gordon, M.A. (1984) J. Immunopharmacol. 6, 381-410; (1985) Biochim. Biophys. Acta 812, 361-368) Irrespective of liposomal size, gramicidin incorporation resulted in a substantial increase in anisotropy of the fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), in fluid phase lipid. In the absence of gramicidin, permethrin and three other pyrethroids, allethrin, cypermethrin and fenpropathrin, increased DPH anisotropy. In these fluid phase systems, as the protein:lipid ratio was increased, the extent of the pyrethroid-mediated increase in fluorescence anisotropy diminished. Also, the pyrethroids shortened DPH fluorescence lifetimes. At high gramicidin:lipid ratios, permethrin substantially lowered anisotropy in the fluid phase lipid, relative to controls. The data suggest that pyrethroids disturb fluid-phase lipids which have been promoted to a relative state of order by proximity to an integral membrane protein. This type of order is one which is represented by DPH fluorescence anisotropy. A model based on these results is proposed to explain the effects of pyrethroids on lipid packing order in cellular membranes, as determined by DPH fluorescence anisotropy.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1986

PK 11195 antagonism of pyrethroid-induced proconvulsant activity.

The acute administration of 1R,cis, alpha S-cypermethrin, deltamethrin fenvalerate and permethrin produced a dose-dependent lowering of the dose of pentylenetetrazol required to elicit a seizure in rats. The proconvulsant action of cypermethrin displayed stereospecificity in that the 1R, cis, alpha S isomer of cypermethrin was the most potent compound tested, while the non-insecticidal isomer, 1S,cis, alpha R-cypermethrin, was devoid of proconvulsant activity. Pretreatment of rats with PK 11195, an antagonist of the peripheral-type benzodiazepine binding site, elicited a complete reversal of the proconvulsant actions of both deltamethrin and permethrin. In contrast, pretreatment with phenytoin did not alter the pyrethroid-induced proconvulsant activity. These results suggest that the effects of pyrethroids on pentylenetetrazol seizure threshold are mediated via an interaction with peripheral-type benzodiazepine binding sites.

Animals↗

PubMed1989

A comparative analysis of the acute toxicity of technical-grade pyrethroid insecticides and their commercial formulations.

Seventy-two-hour LD50 studies involving the fenvalerate formulation, Pydrin 2.4 E.C., and the permethrin formulation, Ambush, were performed with male Swiss mice to compare the toxicity of the commercial formulations to that of the technical-grade pyrethroids. Comparison of the formulation ip and po LD50 values and the lethality of technical-grade pyrethroids revealed an increased toxicity of the technical-grade material when administered as the commercially formulated products. The calculated ip and po LD50 values for Pydrin 2.4 E.C. and Ambush were calculated to be 62 and 72 mg/kg, respectively, whereas those for Ambush were 429 and 424 mg/kg. Administration of doses of technical-grade fenvalerate which corresponded to the amount of fenvalerate contained in the calculated LD99 value of Pydrin resulted in no deaths. Administration of the LD99 value of Ambush, as the technical-grade product, resulted in no deaths following ip administration, whereas the po value resulted in 100% death. The data indicate an effect of the Pydrin formulation vehicle on fenvalerate toxicity, whereas the Ambush vehicle did not enhance permethrin toxicity. Technical-grade material in general was more toxic following po than ip administration suggesting the corn oil vehicle may have reduced ip absorption.

Administration, Oral↗

PubMed1988

Control of horn flies on cattle with insecticide pellets fired from a CO2-operated pistol.

A method is needed to control pyrethroid-resistant horn flies (Haematobia irritans) which would involve the intermittent application of insecticides to cattle without their confinement for treatment. Our objective was to test a CO2 gas-operated pistol, designed to shoot marking pellets, to determine the number of pellet applications required to obtain season-long control. Also, since horn fly resistance to pyrethroid insecticides is widespread, we tested ten other insecticides as concentrates in pellets. Six pellet pistol applications of 38% permethrin provided 84% control of horn flies for 15 weeks. Single pellet applications of ten non-pyrethroid insecticides indicated that none of these insecticides, at the concentrations tested, were as effective as permethrin for control of pyrethroid-resistant horn flies. Our field evaluation of the pellet-pistol method indicates that it has sufficient merit to justify further testing for horn fly control.

Animals↗

PubMed1987

The action of two classes of pyrethroids on the inhibition of brain Na-Ca and Ca + Mg ATP hydrolyzing activities of the American cockroach.

Ca2+-stimulated ATP hydrolyzing activities (i.e. Na-Ca ATP hydrolysis and Ca + Mg ATP hydrolysis) measured in cockroach brain tissue were highly sensitive to the action of pyrethroid insecticides under in vitro conditions. Non-cyano-containing pyrethroids inhibited Na-Ca ATP hydrolysis to a greater extent than their cyano-containing counterparts. The reverse is true for pyrethroid action on Ca + Mg ATP hydrolysis. Nonmitochondrial Ca + Mg ATP hydrolysis of disrupted synaptosomes was the most sensitive activity examined. Ca2+-stimulated ATP hydrolyzing activities were inhibited in cockroaches poisoned by permethrin in vivo. In vivo poisoning occurred in the presence of a similar amount of bound [14C]permethrin which had been determined to cause a substantial amount of inhibition to Ca2+-stimulated ATP hydrolyzing activities in vitro.

Adenosine Triphosphatases↗

PubMedDate not supplied

Effects of pyrethroid insecticides on operant responding maintained by food.

The pyrethroids are potent insecticides with low concomitant mammalian lethality when compared with other major insecticides. While high doses can lead to hyperactivity, tremors, convulsion and death, low doses have not been as well studied. Since operant behavior can be a sensitive measure of CNS function, male Holtzman rats were trained on a VR25 schedule maintained by 45 mg food pellets. Rats were injected IP with one of four different technical grade pyrethroids: permethrin, allethrin, deltamethrin and fenvalerate. All agents were effective in reducing operant responding and did so in a dose-dependent manner at levels 10 to 100 times below their LD50 values. Time course studies indicated a relatively short duration of action for the Type I agents of less than 60 min for permethrin and 15 min for allethrin. Type II agents were generally effective for greater than 60 min. Results of these studies indicate that operant responding maintained by food is a sensitive measure of the behaviorally disruptive effects of subconvulsive doses of pyrethroids.

Allethrins↗

PubMed2005

Influence of pyrethroids and piperonyl butoxide on the Ca(2+)-ATPase activity of rat brain synaptosomes and leukocyte membranes.

Pyrethroids are widely used insecticides of low acute toxicity in mammals but the consequences of long-term exposure are of concern. Their insecticidal action is related to neurotoxicity and, in addition, there are indications of mammalian immunotoxicity. In order to clarify structure-activity relationships of the membrane interactions of pyrethroids, the present study compared the influence of selected pyrethroids, i.e. permethrin and the more water soluble esbiol (S-bioallethrin), both type I, and cyfluthrin, type II, on the Ca(2+)-ATPase activity of rat brain synaptosomes and peritoneal leukocyte membranes. The pyrethroids were tested alone as well as mixed with the enhancing substance piperonyl butoxide (PBO) at concentration ratios of 1:5 and 1:10. At the highest concentration tested, permethrin (10 microM) alone inhibited the ATPase activity of leukocyte membranes by 20%, whereas the synaptosomes were affected less. Esbiol and cyfluthrin alone did not affect either membrane preparation significantly, whereas PBO (50 microM) alone caused 10-15% inhibition. Mixtures of either pyrethroid with PBO inhibited the ATPase activity of both types of membranes (up to 40% inhibition) in a synergistic manner, which always tended to be supra-additive. With esbiol a true potentiation took place. The synergistic interaction between pyrethroid and PBO was most apparent with mixtures of a concentration ratio of 1:5. The ATPase activity of leukocyte membranes tended to be more susceptible to inhibition than that of synaptosomes. The results are in accordance with the assumption that the mammalian toxicity of pyrethroids can be ascribed to a general disturbance of cell membrane function in neuronal tissue. The results indicate that it may also be the case in the immune apparatus.

Allethrins↗

PubMed2001

A novel method of assessing the effectiveness of protective gloves--results from a pilot study.

We have devised a novel method for evaluating the effectiveness of protective gloves and have undertaken a small study to assess this approach. Three types of glove were tested in a standardised simulation test with a permethrin-based pesticide. Prewashed cotton gloves were used to collect the samples. One was worn over the protective glove on one hand to measure the potential deposition of pesticide on the hands had the gloves not been worn. A second was placed under the protective glove on the opposite hand to measure the actual deposition of permethrin on the hands when the gloves were worn. This regime was reversed half way through each test in an attempt to prevent bias. Measurable inner glove contamination occurred on 25 out of 30 occasions. Geometric mean protection factors were calculated from the ratio of outer and inner sampling glove contamination, with average protection factors of 470, 200 and 96 being obtained for the two nitrile and PVC gloves, respectively. The PVC gloves were the least effective in preventing inner glove contamination, probably because the glove was thick and fairly inflexible, causing more pesticide to enter the glove around the cuff. Although the tasks were standardised, variability occurred due to worker behaviour and equipment failure. The spray pump failed on five occasions, resulting in higher levels of inner glove contamination and a geometric mean protection factor of 32. On the occasions when the pump worked correctly, the level of protection provided by the gloves rose dramatically with mean protection factors of 220 and 450 being obtained for workers categorised as "messy" and "tidy", respectively.

Analysis of Variance↗

PubMed1997

Functional analysis of a rat sodium channel carrying a mutation for insect knock-down resistance (kdr) to pyrethroids.

Pyrethroid insensitivity in resistant (kdr) insects has been correlated with a leucine to phenylalanine replacement in the S6 transmembrane segment of domain II of the axonal sodium channel alpha(para)-subunit. An alpha-subunit of rat brain type II sodium channel containing this mutation has been expressed and its sensitivity to permethrin compared with that of the wild-type channel. The steady-state activation curve of the mutant was shifted 14 mV in the depolarizing direction. We propose that an equivalent shift of the sodium current activation curve in kdr insects could account for their low sensitivity to permethrin toxicity.

Animals↗

PubMedDate not supplied

A randomized controlled trial of insecticide-treated bednets and chaddars or top sheets, and residual spraying of interior rooms for the prevention of cutaneous leishmaniasis in Kabul, Afghanistan.

Anthroponotic cutaneous leishmaniasis (ACL) is a significant public health problem in many towns and cities of south central Asia and the Middle East, resulting in disfigurement and disability which warrants preventive action. A randomized controlled trial was conducted in 1997/98 amongst a non-immune study population of 3666 people in Kabul, Afghanistan, to compare the efficacy of insecticide-treated nets (ITNs), insecticide-treated Islamic cloth wraps (chaddars) used to sleep in, and residual pyrethroid spraying of individual houses for the prevention of ACL. Dosages of insecticide were: ITNs with permethrin, 0.5 g/m2; chaddars with permethrin, 1 g/m2; rooms with lambdacyhalothrin, 30 mg/m2. Cases of ACL were diagnosed on clinical criteria. At the end of the trial period (15 months) the incidence of ACL amongst controls was 7.2%, amongst ITN users 2.4% (OR 0.31, 95% CI 0.2-0.5), amongst impregnated chaddar users 2.5% (OR 0.33, 95% CI 0.2-0.6) and amongst residents of sprayed houses 4.4% (OR 0.60, 95% CI 0.3-0.95). ITNs and impregnated chaddars were equally effective, providing about 65% protective efficacy, with approximately 40% protective efficacy attributable to individual house spraying. No significant differences for age or sex were found between new cases in the intervention and control groups. No serious side-effects were reported and interventions were generally popular; ITNs were the most popular, followed by residual spraying and then impregnated chaddars.

Adolescent↗

PubMedDate not supplied

Studies in vitro on the relative efficacy of current acaricides for Sarcoptes scabiei var. hominis.

Resistance of Sarcoptes scabiei to various topical therapies has been described, but clinical assessment of treatment failure is problematic and in-vitro assays are generally not available. We describe a simple in-vitro analysis used to evaluate the relative efficacy of a range of topical, oral, and herbal treatments available in Australia for the treatment of scabies. S. scabiei var. hominis mites were collected from skin scrapings obtained from 7 crusted scabies patients over a period of 2 years (1997 and 1998). Larvae, nymphal instars, and adult mites were tested within 3 h of collection and continuously exposed to selected commercially available treatment products until death, with the elapsed time recorded. Neem was the only product to show little acaricidal activity. Survival curves indicated that, of the other agents, 5% permethrin (Lyclear) had the slowest killing time, with 35% of mites still alive after 3 h, and 4% still alive after 18-22 h of constant exposure. In contrast, no mites were alive after 3 h exposure to 25% benzyl benzoate (Ascabiol), 1% lindane (Quellada), 5% tea tree oil and 100-8000 ng/g of ivermectin (Equimec). Despite the slower killing time with 5% permethrin, there was no evidence of any mite tolerance in vivo or treatment failure in any patients or contact cases.

Animals↗

PubMedDate not supplied

Pyrethroid-impregnated bed nets for personal protection against malaria for Afghan refugees.

A field trial of permethrin-impregnated bed nets (PIBs) was conducted in 2 Afghan refugee villages in Pakistan. Nets were issued to only 10% of families (= 1398 people); this simulated a situation in which bed nets are gradually adopted by villagers in Afghanistan. A further 10% lacking bed nets were selected as controls from the same villages. An initial survey showed that 86% of household heads were aware that malaria was transmitted by mosquito bites, but only 2% had used bed nets before. Trial families were encouraged to attend the village health centres if they fell ill. Microscopy records showed that, between July and December 1991, 22.4% of the control group became infected with Plasmodium vivax and 13.0% contracted P. falciparum while in the intervention group only 9.9% contracted P. vivax (relative risk 0.58, confidence interval [CI] 95% 0.49-0.68) and only 3.8% contracted P. falciparum (relative risk 0.39, 95% CI 0.29-0.53). A single treatment of the nets with permethrin at 0.5g/m2 remained protective throughout the 6 months' transmission season. 73% of families claimed to use their nets every night; members of families who claimed to use nets less regularly showed an incidence similar to that of the control group. There was no sex or age difference in net use or protective efficacy. Headlouse infestation rates were reduced in PIB users. Few nets were washed, given away or sold. The prospect for PIBs as personal protection appears good, despite people's lack of previous experience.

Adolescent↗