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PubMed1957

Progress in physiological studies of insecticide resistance.

This study deals first with the progress recently made in investigations on the mode of toxic insecticidal action of DDT, lindane and other chlorinated hydrocarbons, pyrethrins and related chemicals, and organo-phosphates, and secondly with resistance mechanisms to the same insecticides.The author feels that, although good progress is being made towards understanding the physiological mechanisms of resistance, the gaps in present knowledge, the types of insecticide to which resistance is developing, and the number of medically important species involved lead inevitably to the conclusion that the general outlook for insect control is deteriorating. He considers that what is now needed is not so much continuation of the present empirical approach to the problem of resistance as intensification of basic studies of the biology, ecology and physiology of the insect species concerned to provide a foundation for more rational alternative control measures.

Insect Control↗

PubMed1960

Susceptibility of body-lice to DDT in a heavily treated area of Yugoslavia.

Body-lice collected in the Kosohovo-Metohia area of Yugoslavia, an area with a long history of epidemic typhus and one which had been treated with DDT since 1947, were tested for their susceptibility to that compound by the standard WHO test and showed an average mortality of 99% to 1.0% DDT and 96% to 0.1% DDT. Freshly fed insects showed 100% mortality at both concentrations. Tests with DDT-impregnated cloth indicated that the LD(50) had tripled between 1955 and 1958.In sleeve tests the body-lice appeared to tolerate 15 times as much DDT as in tests not involving the use of the human arm. Tests were also made to ascertain the effect of lowered temperature on reducing mortality from DDT, and the speed of kill with DDT was compared with that with BHC and pyrethrins.

Animals↗

PubMed2006

Bifenthrin causes neurite retraction in the absence of cell death: a model for pesticide associated neurodegeneration.

BACKGROUND: Bifenthrin is a synthetic pyrethroid insecticide derivative of naturally occurring pyrethrins from chrysanthemum flowers. Bifenthrin is considered relatively safe and therefore incorporated as the active ingredient in preparations sold over the counter for household use. Recent studies have raised concern that chronic exposure to pesticides in the home setting may increase the risk for neurodegenerative diseases. To address this concer, in the present study, bifenthrin is added to pre-differentiated PC12 and effect of bifenthrin on the retraction of existing neurites is observed a model for neurodegeneration. MATERIAL/METHODS: PC12 cells were differentiated with nerve growth factor for twenty-four hours and then treated with what was determined to be a sublethal dose of bifenthrin for up to an additional 48 hours. The percent of cells with neurites was assessed at various times before and after nerve growth factor treatment. Bifenthrin toxicity was determined using trypan blue exclusion. RESULTS: Bifenthrin was not toxic to PC12 cells at concentrations ranging from 1 x 10(-10) M to 1 x 10(-4) M. Twenty-four hours after nerve growth factor treatment, a maximum percent of cells had formed neurites and with a treatment of 1 x 10(-5) M bifenthrin, approximately 80% of these neurites retracted in within 12 additional hours and almost all neurites had retracted within 48 hours. Trypan exclusion showed that these cells were viable. CONCLUSIONS: These data show that bifenthrin can stimulate the retraction of neurites in the absence of frank toxicity.

Animals↗

PubMed1990

Pediculosis.

Pediculosis can be caused by two distinctly different organisms, the head louse and the pubic louse. Although differing anatomically, they produce equivalent disorders, with itching, bites, and nits on the hairs. The head louse causes disease of the scalp, while the pubic louse lives in short hair in the pubic regions, the body, the axillae, the eyebrows, and the eyelashes. Both can be treated with gamma isomer of hexachlorobenzene, but various mixtures of pyrethrins seem more effective. The body louse, which exactly resembles the head louse, is the only one that can transmit disease. Treatment of body louse infestation is mainly cleanliness: washing the patient and changing his clothing.

Animals↗

PubMed1988

Pyrethroid insecticides: stereospecific allosteric interaction with the batrachotoxinin-A benzoate binding site of mammalian voltage-sensitive sodium channels.

Pyrethroid insecticides are synthetic neurotoxins patterned after the naturally occurring pyrethrins. Their mechanism of action is thought to involve effects primarily at the voltage-sensitive sodium channel of both insect and mammalian neurons, although recent studies have raised the possibility that these compounds may also act at the gamma-aminobutyric acid receptor-chloride ionophore complex. Here we show that active pyrethroids of the alpha-cyano-3-phenoxybenzyl class allosterically enhance the binding of [3H]batrachotoxinin-A 20-alpha-benzoate to voltage-sensitive sodium channels of rat brain in a dose-dependent and stereospecific manner. Comparison of the rank order of potency for enhancement of [3H]batrachotoxinin-A 20-alpha-benzoate binding and insecticidal activity in a series of toxic stereoisomers of cypermethrin, representative of the class, reveals a correlation between the two measures. These results support a sodium channel site model for pyrethroid action and suggest a useful and practical method to help evaluate the relationship between effects at the sodium channel and insecticidal potency for members of this class of compounds.

Allosteric Regulation↗

PubMed1989

[Methods of reducing the amount of pediculocide residues on bed linens to safe levels].

The means for reducing the residue of organophosphorous and pyrethrin pediculicides on the fabric to safety levels have been developed due to the use of gas and liquid chromatography. The proposed procedures include linen washing after its pediculicidal treatment. Optimal conditions for the removal of the above substances from the fabric have been set forth. Actual quantity of pediculicides on the fabric after its treatment has been identified.

Animals↗

PubMed1980

Treatment of public lice infestation: a comparison of two agents.

Bulletins issued by both the United States Public Health Service and the Pan American Health Organization have noted a sharp increase in the incidence of public lice infestation (pediculosis pubis) in this country. At the Haight-Ashbury Free Medical Clinic we conducted a controlled, open study comparing the efficacy and safety of Kwell Shampoo (gamma benzene hexachloride; lindane) with RID, an over-the-counter, pyrethrin-based pediculicide. The results showed the two treatments to be equally effective and safe. All adult lice, nymphs, and nits were eradicated at the one week follow-up in fifteen patients treated with single applications of either product. Two patients in each group experienced very slight and transient erythema.

Administration, Topical↗

PubMed1984

Head-lice infestations and their treatment.

Head-lice infestations periodically cause disruption at schools and crèches. The life cycle of the insect and the treatment of infestation are discussed. Treatment is usually relatively simple and effective, relying mainly on the use of insecticides such as gamma benzene hexachloride, malathion and pyrethrins. Appropriate therapy for problem areas, for example the eyebrows, is also described.

Anoplura↗

PubMedDate not supplied

Species and structural variations affecting pyrethroid neurotoxicity.

Pyrethroids provide fascinating patterns and examples of species selectivity resulting from variations in nerve sensitivity and detoxification rates. Three classification systems are useful in considering pyrethroids: origin, structure, stability and use relative to the natural pyrethrin I; lethal and sublethal or knockdown agents; Types I and II symptoms and nerve action. Pyrethroid-detoxifying esterases and oxidases contribute importantly to the species and strain specificity and provide an opportunity to use inhibitors as synergists for improved effectiveness. Pyrethroids are potent and selective neuropharmacological agents inducing repetitive discharges or conduction block in a variety of sensory and motor nerves and in the CNS. Small structural modifications in the pyrethroid often change the type of action as well as the potency and species specificity. Pyrethroid resistance in selected strains of insect pests may involve a modified and pyrethroid-insensitive target site.

Animals↗

PubMed1993

[Pediculosis capitis: a questionnaire survey in 4 schools of the Bordeaux Academy 1990-1991].

A questionnaire survey of head lice treatment was conducted in four schools--each including a nursery and an elementary school--in the Bordeaux area. Two schools were situated in the centre of the city, one in a suburban area and one in a rural area (50 km from the city). Four-page questionnaires were filled in anonymously by the parents in April 1991; 840 answers were obtained (80 p. 100 response rate). Between January 1990 and March 1991, 48.7 p. 100 of children had at least one episode of head lice infestation (infestation rates varied from 38.8 to 62.6 p. 100 depending on the schools); 30.5 p. 100 of children were contaminated for the first time during that period. Lice were detected by the parents in 95 p. 100 of the cases. The prevalence of lice was higher in females (60 p. 100) than in males (40 p. 100). The highest prevalence was noted in the suburban school where 17 p. 100 of the parents were unemployed at the time of the survey. The peak age for head lice was 7, but 19.4 p. 100 of nursery school children aged 2-4 years had been contaminated at least once. Impetigo was rare (1.2 p. 100), and pruritus was noted in only 14.2 p. 100 of the cases. Most children had been contaminated at school. Curative treatment was counselled by a chemist in 87 p. 100 of the cases. Pyrethrins were used in 81 p. 100, and the shampoo (Hegor) plus spray (Paraspecial Poux) association was the most frequent, totalling two-thirds of prescriptions.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed1994

Do mosquito coils and killer sticks work against Anopheles gambiae sensu lato mosquitoes in Zimbabwe?

Tests against Anopheles gambiae s. 1. mosquitoes (malaria transmitting mosquitoes) were carried out in Chegutu, Chiredzi and Kamhororo (Gokwe). These tests were done in relatively closed rural huts and experimental huts. The tests demonstrated that a one hour exposure to smoke from the burning of insecticidal coils contain 0.3 pc pyrethrin, achieve 100 pc knockdown of mosquitoes. Mosquito killer sticks gave 85 pc knockdowns with 30 pc recoveries and less than 10 pc recoveries for the coils. With caged insects in Gokwe the KD50 for both the coils and sticks was been 15 to 20 minutes and the KD90 ranged from 40 to 50 minutes. The coils were observed to more lethal than the sticks. Mortalities were 100 pc for the coils and 85 pc for the killer sticks after a 24 hour holding period.

Animals↗

PubMed1994

Effects of permethrin-impregnated bed nets on malaria vectors of northern Guatemala.

The authors evaluated the effects on malaria vectors of bed nets impregnated with permethrin over the course of a 16-month controlled study in four communities of Northern Guatemala. Anopheles albimanus and An. vestitipennis were the known malaria vectors in the area. Households were allocated to one of three experimental groups: those receiving bed nets impregnated with 500 mg/m2 of permethrin, those receiving untreated bed nets, and those where no intervention measures were taken. The impact of the treated and untreated bed nets on mosquito abundance, behavior, and mortality was determined by indoor/outdoor night-bite mosquito collections, morning pyrethrum spray collections, inspection of bed net surfaces for dead mosquitoes, and capture-release-recapture studies. The duration of the treated nets' residual insecticide effect was assessed by modified WHO cone field bioassays, and their pyrethrin content was estimated by gas-liquid chromatography analysis. The most important observation was that fewer mosquitoes were found to be resting in the households with treated bed nets. The treated nets probably functioned by both repelling and killing vector mosquitoes. Capture-release-recapture studies showed exit rates from houses with treated nets were higher (94%) than those from control houses (72%), a finding that suggests repellency. However, no significant differences were noted between the indoor night-bite mosquito collections at houses with and without treated nets. The horizontal surfaces of treated bed nets were nearly 20 times more likely to contain dead anopheline mosquitoes than were the comparable surfaces of untreated nets. the bioassays indicated that unwashed permethrin-impregnated bed nets retained their insecticidal activity for 6 months after treatment.

Animals↗

PubMedDate not supplied

Determination of pyrethroid residues in vegetables, fruits, grains, beans, and green tea leaves: applications to pyrethroid residue monitoring studies.

Determination of natural pyrethrins and 12 synthetic pyrethroids in agricultural products was investigated. Vegetables and fruits were extracted with acetone, filtered after addition of coagulating solution, partitioned into n-hexane, and cleaned up on a Florisil column (as necessary). Pyrethroids were determined by gas chromatography/electron capture detection (GC/ECD) by using a methyl silicone-coated fused-silica capillary column, and recoveries were calculated by summing peak areas of the components. GC/mass spectrometry was used to identify the pyrethroids detected by GC/ECD monitoring. Grains and beans containing lipids were analyzed by extraction with acetonitrile, partition into n-hexane, Florisil column cleanup, and capillary GC/ECD. The coagulation method was suitable for nonfatty crops such as vegetables, fruits, and green tea leaves, because recoveries were good and Florisil column cleanup was not needed in most cases. The coagulation method was not applicable to lipid-containing crops such as grains and beans because of low recoveries. Recoveries for 18 crops at fortification levels of 0.25-1.0 ppm were 60.0-103.5%. No pyrethroids were detected from the nonfortified crops tested except green tea leaves, in which fluvalinate was detected at 0.89 ppm.

Chromatography, Gas↗

PubMed2001

Monitoring insecticide resistance in house flies (Diptera: Muscidae) from New York dairies.

House flies were collected from dairies across New York state and the levels of resistance to seven insecticides were measured using standard laboratory assays with three to five diagnostic concentrations. The highest levels of resistance were found for tetrachlorvinphos, permethrin and cyfluthrin. Although levels of resistance to methomyl were somewhat lower, they were among the highest ever reported for field-collected house flies. Resistance to pyrethrins was limited primarily to the lowest diagnostic concentration. House flies were susceptible to fipronil at all dairies, suggesting that this material would be highly effective for fly control. The levels of resistance were similar at all the dairies, irrespective of their insecticide use, suggesting substantial movement of flies between facilities. Relative to resistance levels found at New York dairies in 1987, resistance levels had increased for permethrin, were unchanged for tetrachlorvinphos and had decreased for dimethoate. To identify a single diagnostic concentration that could be used in the laboratory assays to assess accurately resistance levels in future studies, we carried out a 'simulated' field bioassay using formulated materials. A diagnostic concentration for each insecticide is proposed on the basis of a comparison of our bioassays.

Adaptation, Physiological↗

PubMed1987

Compatibility of Metarhizium anisopliae var. anisopliae with chemical pesticides.

The effects of various insecticides on the mycelial growth, sporulation and conidial germination of Metarhizium anisopliae var. anisopliae isolate E9 were studied in the laboratory. Chlorpyrifos was the most toxic organophosphate to mycelial growth and sporulation at all concentrations. Temephos, malathion and leptophos were highly toxic to sporulation while malathion was the most inhibitory to germination. The carbamates, carbofuran, methomyl and oxamyl were moderately toxic to mycelial growth and sporulation while oxamyl had an adverse effect on germination. The pyrethroids (pyrethrin, permethrin and resmethrin) and the insect growth regulators (diflubenzuron and methoprene) were not inhibitory to the various developmental stages of isolate E9. The chlorinated hydrocarbons (chlordane, lindane and toxaphene) were more deleterious than all other insecticide groups tested. Among the fungicides, benomyl and maneb produced the greatest inhibition.

Drug Resistance, Microbial↗

PubMed1988

Insecticidal activity of pyrethroids on insects of medical importance.

Pyrethroid insecticides, from natural pyrethrins to photostable analogues, represent important weapons against insect pests of both economic and medical importance. They share many characteristics with DDT, including a negative temperature coefficient, and knockdown and killing activity resulting from action against the sodium channels of the peripheral and central nervous systems. In this review, Eduardo Zerba summarizes what is known about their penetration into target insects, their mode of action, metabolism and excretion.

Journal Article↗

PubMed1987

Pyrolysing insecticidal coils: air pollution by polycyclic aromatic hydrocarbons and other mutagens detected by the Salmonella/microsome test.

Pyrolysing insecticidal coils, which are used commonly for their evaporative release of insecticidal amounts of pyrethrins, have been investigated with respect to the emission of airborne particles, their mutagenic activity in the Salmonella/microsome mutagenicity test and their polycyclic aromatic hydrocarbons (PAH) content. Emitted particles contain compounds that are mutagenic in the absence of exogenous activation, as well as components that require mammalian activation. The particles also contain a range of PAH, but their concentration cannot account for the mutagenic response with mammalian activation. The use of pyrolysing insecticidal coils in semi-enclosed spaces may cause air pollution by releasing mutagenic and carcinogenic compounds that are of a magnitude similar to that found in other air pollution situations.

Journal Article↗

PubMed2026

Evaluation of the effects of domestic tomato processing on biopesticide residue using natural deep eutectic solvents (NADES) extractions.

The present study evaluated the fate of fourteen botanical biopesticides in processed tomato samples. Various processing methods were employed, including washing, dehydration, and the preparation of juice and sauce. The extraction was performed using more sustainable techniques, aimed at minimizing the environmental impact of conventional organic solvents by substituting them with natural deep eutectic solvents (NADES). Solid-liquid extraction (SLE) and dispersive liquid-liquid microextraction with solidification of floating organic drop (DLLME-SFOD) were utilized for solid and liquid tomato samples, respectively. The NADES used was choline chloride:2,3-butanediol (ChClBt) at a 1:4 molar ratio for both techniques, resulting in recovery values ranging from 69.2 to 106.2% for SLE, and extraction efficiencies reaching up to 46.2% for DLLME-SFOD. The impact of these processes was evaluated employing the processing factor (PF), yielding PF values of less than 1 in all cases. Compounds as pyrethrins, azadirachtin, and rotenone persisted after processing, posing a potential consumer risk.

Solanum lycopersicum↗