cyhalothrin and cyfluthrin

To address concerns around age-related sensitivity to pyrethroids, a life-stage physiologically based pharmacokinetic (PBPK) model, supported by in vitro to in vivo extrapolation (IVIVE) was developed. The model was used to predict age-dependent changes in target tissue exposure of 8 pyrethroids; deltamethrin (DLM), cis-permethrin (CPM), trans-permethrin, esfenvalerate, cyphenothrin, cyhalothrin, cyfluthrin, and bifenthrin. A single model structure was used based on previous work in the rat. Intrinsic clearance (CLint) of each individual cytochrome P450 or carboxylesterase (CES) enzyme that are active for a given pyrethroid were measured in vitro, then biologically scaled to obtain in vivo age-specific total hepatic CLint. These IVIVE results indicate that, except for bifenthrin, CES enzymes are largely responsible for human hepatic metabolism (>50% contribution). Given the high efficiency and rapid maturation of CESs, clearance of the pyrethroids is very efficient across ages, leading to a blood flow-limited metabolism. Together with age-specific physiological parameters, in particular liver blood flow, the efficient metabolic clearance of pyrethroids across ages results in comparable to or even lower internal exposure in the target tissue (brain) in children than that in adults in response to the same level of exposure to a given pyrethroid (Cmax ratio in brain between 1- and 25-year old = 0.69, 0.93, and 0.94 for DLM, bifenthrin, and CPM, respectively). Our study demonstrated that a life-stage PBPK modeling approach, coupled with IVIVE, provides a robust framework for evaluating age-related differences in pharmacokinetics and internal target tissue exposure in humans for the pyrethroid class of chemicals.

Topics: Carboxylesterase; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Humans; Kinetics; Liver; Microsomes, Liver; Models, Biological; Nitriles; Permethrin; Pharmacokinetics; Pyrethrins

The metabolism of bifenthrin (BIF), β-cyfluthrin (CYFL), λ-cyhalothrin (CYHA), cyphenothrin (CYPH) and esfenvalerate (ESF) was studied in liver microsomes, liver cytosol and plasma from male Sprague-Dawley rats aged 90, 21 and 15 days and from adult humans. Pyrethroid metabolism was also studied with some human expressed cytochrome P450 (CYP) and carboxylesterase (CES) enzymes. All five pyrethroids were metabolised by adult (90 day old) rat hepatic microsomal CYP and CES enzymes and by cytosolic CES enzymes. The pyrethroids were also metabolised by human liver microsomes and cytosol. Some species differences were observed. Pyrethroid metabolism by cytosolic CES enzymes contributes to the overall hepatic clearance of these compounds. CYFL, CYHA, CYPH and ESF were metabolised by rat plasma CES enzymes, whereas none of the pyrethroids were metabolised by human plasma. This study demonstrates that the ability of male rats to metabolise these pyrethroids by hepatic CYP and CES enzymes and plasma CES enzymes increases with age. In all instances, apparent intrinsic clearance values were lower in 15 than in 90 day old rats. All pyrethroids were metabolised by some of the human expressed CYP enzymes studied and apart from BIF were also metabolised by CES enzymes.

Topics: Animals; Carboxylesterase; Cytochrome P-450 Enzyme System; Humans; Male; Microsomes, Liver; Nitriles; Pyrethrins; Rats

This study compared four different statistical methods, involving six estimation procedures, for addressing censored left data in measuring temporal trends of eight different pyrethroids measured in sediment from a 10-year data set in a residential California stream (Pleasant Grove Creek). The statistical methods used were: the Kaplan-Meier (km) method; the robust regression on order statistics (ros using normal and log normal distributions rosln); the maximum likelihood estimation (mlen using normal and log normal distributions mleln); and a substitution method (sub) using ½ the detection limit. For five of the eight pyrethroids (bifenthrin, cyfluthrin, cypermethrin, lambda-cyhalothrin, and permethrin), the six statistical methods generally agree, with one exception, that the data set exhibit significant declining trends. In the case of bifenthrin, the slight disagreement among statistical methods only occurred for the mleln estimate that did not show a significant declining trend, whereas the other five methods did. For deltamethrin, esfenvalerate, and fenpropathrin, all six statistical methods were in agreement showing no significant trends. Possible reasons for declining sediment concentrations of pyrethroids in Pleasant Grove Creek are urban label changes effective in 2012-2015 that reduced residential use, variable annual rainfall, and more responsible homeowner use based on outreach/education programs.

Topics: Animals; California; Environmental Monitoring; Insecticides; Nitriles; Permethrin; Pyrethrins; Rivers; Water Pollutants, Chemical

Oregano, a widely used and popular herb, is particularly vulnerable to fraud. Less valued plants, adulterants that are often used for dilution, may introduce into this commodity additional contaminants such as pesticide residues. In this study, more than 400 pesticides were screened in a representative set of 42 genuine and 34 adulterated dried oregano samples collected from various locations across Europe. The results obtained by advanced mass spectrometry-based methods, showed, that some pesticide residues could be detected in virtually all tested samples, nevertheless, on average, higher contamination was found in the adulterated oregano samples. Increased incidence of insecticides such as cyfluthrin, permethrin and cyhalothrin was typical for these samples, moreover, pyriproxyfen was detected exclusively in adulterated samples. Thus, based on a critical assessment of pesticide profiles, suspected adulterated oregano samples can be selected for follow up authenticity testing.

Topics: Europe; Food Contamination; Gas Chromatography-Mass Spectrometry; Mass Spectrometry; Nitriles; Origanum; Pesticide Residues; Pesticides; Pyrethrins

New imine-linked molecularly imprinted covalent organic frameworks (MICOFs) were successfully prepared, using fenvalerate as the dummy template. Schiff base reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-triformylphloroglucinol was rapidly achieved at room temperature, using Sc(OTf)

Topics: Chromatography, High Pressure Liquid; Cold Temperature; Insecticides; Metal-Organic Frameworks; Molecular Imprinting; Nitriles; Plants; Pyrethrins; Solid Phase Extraction; Time Factors

To assess the susceptibility status of malaria vectors to pyrethroids and dichlorodiphenyltrichloroethane (DDT), characterise the mechanisms underlying resistance and evaluate the role of agro-chemical use in resistance selection among malaria vectors in Sengerema agro-ecosystem zone, Tanzania.. Mosquito larvae were collected from farms and reared to obtain adults. The susceptibility status of An. gambiae s.l. was assessed using WHO bioassay tests to permethrin, deltamethrin, lambdacyhalothrin, etofenprox, cyfluthrin and DDT. Resistant specimens were screened for knock-down resistance gene (kdr), followed by sequencing both Western and Eastern African variants. A gas chromatography-mass spectrophotometer (GC-MS) was used to determine pesticide residues in soil and sediments from mosquitoes' breeding habitats.. Anopheles gambiae s.l. was resistant to all the insecticides tested. The population of Anopheles gambiae s.l was composed of Anopheles arabiensis by 91%. The East African kdr (L1014S) allele was found in 13 of 305 specimens that survived insecticide exposure, with an allele frequency from 0.9% to 50%. DDTs residues were found in soils at a concentration up to 9.90 ng/g (dry weight).. The observed high resistance levels of An. gambiae s.l., the detection of kdr mutations and pesticide residues in mosquito breeding habitats demonstrate vector resistance mediated by pesticide usage. An integrated intervention through collaboration of agricultural, livestock and vector control units is vital.

Topics: Agriculture; Animals; Anopheles; DDT; Ecosystem; Genes, Insect; Humans; Insect Vectors; Insecticide Resistance; Insecticides; Malaria; Mutation; Nitriles; Permethrin; Pesticide Residues; Pesticides; Pyrethrins; Soil; Species Specificity; Tanzania

The dissipation of six pesticides (carbendazim, thiabendazole, procymidone, bifenthrin, λ-cyhalothrin, and β-cyfluthrin) in shiitakes from cultivation to postharvest drying process was investigated, and the dietary exposure risk was estimated thereafter. The field trial study indicates that the half-lives of carbendazim, thiabendazole, and procymidone were much shorter than those of bifenthrin, λ-cyhalothrin, and β-cyfluthrin. Furthermore, the effects of two drying processes on the residues and processing factors (PFs) were investigated. The results showed that hot-air drying resulted in higher residues than sunlight exposure drying. Both drying processes led to pesticide residue concentration (with PF > 1), except for thiabendazole upon sunlight exposure treatment. The estimated daily intakes (EDIs) ranged from 0.06% of the acceptable daily intake (ADI) for thiabendazole to 42.43% of the ADI for procymidone. The results show that the six pesticide residues in dried shiitakes are still within acceptable levels for human consumption on the basis of a dietary risk assessment.

Topics: Benzimidazoles; Bridged Bicyclo Compounds; Carbamates; Diet; Environmental Monitoring; Food Contamination; Humans; Nitriles; Pesticide Residues; Pyrethrins; Reproducibility of Results; Risk Assessment; Shiitake Mushrooms; Thiabendazole

Continuous use of the pyrethroid insecticide beta-cypermethrin (beta-cp) has resulted in serious environmental contamination problems. We report here that a novel bacterial strain BSF01, which was isolated from activated sludge and identified as Bacillus subtilis (collection number: CCTCC AB 2014103), showed high efficiency in degrading beta-cp. Strain BSF01 was able to utilize beta-cp as the sole carbon source for growth and degraded 89.4 % of 50 mg L(-1) beta-cp within 7 days. The optimal conditions for beta-cp degradation were determined to be 34.5 °C, pH 6.7, and inocula amount 0.11 g dry wt L(-1) using response surface methodology. The kinetic parameters q max, K s, and K i were established to be 2.19 day(-1), 76.37 mg L(-1), and 54.14 mg L(-1), respectively. The critical inhibitor concentration was determined to be 64.30 mg L(-1). Seven metabolites were identified by gas chromatography-mass spectrometry. Furthermore, a novel biodegradation pathway for beta-cp was proposed on the basis of analysis of the metabolites. This strain was also capable of degrading a wide range of pyrethroid insecticides including cypermethrin, deltamethrin, cyhalothrin, and beta-cyfluthrin, which similar to beta-cp are hazardous chemicals. Taken together, our results depict the biodegradation pathway of beta-cp and highlight the promising potentials of strain BSF01 in bioremediation of pyrethroid-contaminated environments.

Topics: Bacillus subtilis; Biodegradation, Environmental; Gas Chromatography-Mass Spectrometry; Insecticides; Nitriles; Pyrethrins; Sewage

A resistant strain of the Aphis glycines Matsumura (CRR) has developed 76.67-fold resistance to lambda-cyhalothrin compared with the susceptible (CSS) strain. Synergists piperonyl butoxide (PBO), S,S,S-Tributyltrithiophosphate (DEF) and triphenyl phosphate (TPP) dramatically increased the toxicity of lambda-cyhalothrin to the resistant strain. Bioassay results indicated that the CRR strain had developed high levels of cross-resistance to chlorpyrifos (11.66-fold), acephate (8.20-fold), cypermethrin (53.24-fold), esfenvalerate (13.83-fold), cyfluthrin (9.64-fold), carbofuran (14.60-fold), methomyl (9.32-fold) and bifenthrin (4.81-fold), but did not have cross-resistance to chlorfenapyr, imidacloprid, diafenthiuron, abamectin. The transcriptional levels of CYP6A2-like, CYP6A14-like and cytochrome b-c1 complex subunit 9-like increased significantly in the resistant strain than that in the susceptible. Similar trend were observed in the transcripts and DNA copy number of CarE and E4 esterase. Overall, these results demonstrate that increased esterase hydrolysis activity, combined with elevated cytochrome P450 monooxygenase detoxicatication, plays an important role in the high levels of lambda-cyhalothrin resistance and can cause cross-resistance to other insecticides in the CRR strain.

Topics: Animals; Aphids; Cytochrome P-450 Enzyme System; Esterases; Insect Proteins; Insecticide Resistance; Insecticides; Nitriles; Pyrethrins

The effect of spinosad exposure on the susceptibility of pyrethroid- and organophosphate-resistant populations of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), to insecticides was investigated in broiler house farm and laboratory studies. A field pyrethroid- and organophosphate-resistant population showed a 3.6-fold increase in susceptibility to gamma-cyhalothrin following spinosad treatment. Overall, cyfluthrin- and fenitrothion-resistant field populations were more susceptible to these insecticides following spinosad treatments, but populations that were not resistant showed no change in susceptibility following spinosad treatment. In a related study, three broiler farm beetle populations with very similar levels of cyfluthrin and gamma-cyhalothrin resistance and similar susceptibilities to spinosad were used to investigate temporal effects of spinosad field treatments on the susceptibility to pyrethroids. Farm insecticide regimes applied at the start of each flock differed: the control broiler house received no insecticide applications, another house was systematically treated with cyfluthrin at the start of each study flock, and the third house was systematically treated with spinosad at the start of five flocks. Afterwards, treatments reverted to cyfluthrin on all farms. At the end of flocks, beetles were tested with cyfluthrin, gamma-cyhalothrin, and spinosad. The control and cyfluthrin house beetles did not change susceptibility to pyrethroids over the period of the study. In the spinosad house, spinosad had no effect on spinosad susceptibility but dramatically increased cyfluthrin and gamma-cyhalothrin susceptibilities. These new susceptibilities were maintained while spinosad applications continued, but pyrethroid susceptibility declined once spinosad applications ceased. This study provides evidence of a synergistic interaction between spinosad and pyrethroids in pyrethroid-resistant beetles. This evidence has significant implications for management of insecticide-resistant populations through an integrated spinosad-pyrethroid strategy that aims to minimize insecticide use while enhancing control.

Topics: Animals; Coleoptera; Drug Combinations; Drug Interactions; Insecticides; Macrolides; Nitriles; Pyrethrins

We studied the susceptibility to organophosphate, carbamate and pyrethroid insecticides of Aedes aegypti from different regions of high transmission risk for dengue in Panama.. To evaluate the susceptibility to organophosphate, carbamate and pyrethroid insecticides in Ae. aegypti from eight sites belonging to seven municipalities in Panamá.. We collected Ae. aegypti larval populations in different types of breeding sites located in urban areas. Insects were reared in laboratory control conditions. With the F 1 generation of each strain we performed susceptibility bioassays using WHO standardized methodology for larvae and adults.. The eight Ae. Aegypti strains were susceptible to the pyrethroid insecticides: deltamethrin, lambdacyhalothrin and cifluthrin, to the organophosphate fenitrothrion, and to the carbamates propoxur and bendiocarb. Only the CHITRE strain exhibited a moderate resistance to the insecticide deltamethrin in larvae (FR 50 =5x). However, adults were susceptible.. It is necessary to perform periodic surveillance to evaluate the susceptibility of Ae. aegypti populations in the studied municipalities with the purpose of preserving their susceptible. The insecticides applied for Ae. aegypti control can still be used in the evaluated municipalities; however it will depend on the susceptibility of the mosquitoes in the specific area.

Topics: Aedes; Animals; Dose-Response Relationship, Drug; Female; Fenitrothion; Insecticide Resistance; Insecticides; Larva; Nitriles; Panama; Phenylcarbamates; Propoxur; Pyrethrins

Pyrethroid insecticides are hydrophobic compounds that partition to streambed sediments and have been shown to cause toxicity to non-target organisms; their occurrence is well documented in parts of California, but there have been limited studies in other urban and agricultural areas across the United States. To broaden geographic understanding of pyrethroid distributions, bed sediment samples were collected and analyzed from 36 streams in 25 states, with about 2/3 of the sites in urban areas and 1/3 in agricultural areas. At least one pyrethroid (of the 14 included in the analysis) was detected in 78% of samples. Seven pyrethroids were detected in one or more samples. Bifenthrin was the most frequently detected (58% of samples), followed by permethrin (31%), resmethrin (17%), and cyfluthrin (14%). The other three detected pyrethroids (cyhalothrin, cypermethrin and delta/tralomethrin) were found in two or fewer of the samples. Concentrations ranged from 0.3 to 180 ng g(-1) dry weight. The number of pyrethroids detected were higher in the urban samples than in the agricultural samples, but the highest concentrations of individual pyrethroids were split between urban and agricultural sites. The pyrethroids detected in the agricultural areas generally followed use patterns. Predicted toxicity was greater for urban areas and attributed to bifenthrin, cyfluthrin and cypermethrin, while in agricultural areas the toxicity was mainly attributed to bifenthrin.

Topics: Agriculture; Cities; Environmental Monitoring; Geologic Sediments; Insecticides; Nitriles; Permethrin; Pyrethrins; Rivers; United States; Water Pollutants, Chemical; Water Pollution, Chemical

A bacterial strain ZS-S-01, newly isolated from activated sludge, could effectively degrade fenvalerate and its hydrolysis product 3-phenoxybenzoic acid (3-PBA). Based on the morphology, physiological biochemical characteristics, and 16 S rDNA sequence, strain ZS-S-01 was identified as Stenotrophomonas sp. Strain ZS-S-01 could also degrade and utilize deltamethrin, beta-cypermethrin, beta-cyfluthrin, and cyhalothrin as substrates for growth. Strain ZS-S-01 was capable of degrading fenvalerate rapidly without a lag phase over a wide range of pH and temperature, even in the presence of other carbon sources, and metabolized it to yield 3-PBA, then completely degraded it. No persistent accumulative product was detected by HPLC and GC/MS analysis. Studies on biodegradation in various soils showed that strain ZS-S-01 demonstrated efficient degradation of fenvalerate and 3-PBA (both 50 mg·kg(-1)) with a rate constant of 0.1418-0.3073 d(-1), and half-lives ranged from 2.3 to 4.9 days. Compared with the controls, the half-lives for fenvalerate and 3-PBA reduced by 16.9-156.3 days. These results highlight strain ZS-S-01 may have potential for use in bioremediation of pyrethroid-contaminated environment.

Topics: Benzoates; Biodegradation, Environmental; DNA, Bacterial; Nitriles; Pyrethrins; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Sewage; Soil Pollutants; Stenotrophomonas

Most studies on interior (or indoor) residual spraying (IRS) have been targeted on permanent/semipermanent structures. We measured the utility of a portable field bioassay, which can be set up quickly to determine the best chemical repellent or irritant for use as an IRS during an emergency or military situation when displaced persons are temporarily housed in tents. If the bioassay were used over an extended period of time, it would also offer a unique way to monitor vector susceptibility and would be able to determine which chemical is most efficient in individual populations. In total, 2193 mosquitoes belonging to seven species in five genera were collected over the study period. No statistical differences were found between any of the treatments, control, and standard tents utilizing the 4 x 4 Latin square design. Therefore, we conclude that IRS with these tested chemicals in military-issued two-person tents are not effective or significant at stopping mosquito entrance. Further studies on implementation of a portable, field bioassay should include utilizing different mosquito traps in the bioassay and looking at the difference between contact irritants and spatial repellents in different-sized tents, as spatial repellency may be more important in smaller-sized tents.

Topics: Animals; Biological Assay; Culicidae; Disease Transmission, Infectious; Humans; Insect Bites and Stings; Insecticides; Male; Military Medicine; Nitriles; Permethrin; Pyrethrins; Treatment Failure; United States

Gamma-Cyhalothrin was proposed as an agent for management of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), in Australian broiler houses. From 2007 to 2009, baseline susceptibility of 20 Australian broiler farm beetle populations plus an insecticide-susceptible laboratory population was determined for gamma-cyhalothrin by using topical application. In addition, repeat testing and regression analyses of specific beetle populations to gamma-cyhalothrin showed that topical application was a very reliable and repeatable testing method. The 21 populations were tested with a cyfluthrin discriminating concentration (based on LC(99.9), 0.0007% [AI]) to identify possible cross-resistance. Across all populations, there was a significant linear relationship between the gamma-cyhalothrin LC50 value and mortality induced by the cyfluthrin LC(99.9). Full cyfluthrin baseline studies of seven populations indicated that gamma-cyhalothrin was twice as toxic as cyfluthrin, even against susceptible beetles and resistance ratios at the cyfluthrin LC50 and LC(99.9), varied considerably, with maxima of 56.6 and 83.6 respectively. Corresponding ratios for gamma-cyhalothrin for the same populations were 8.6 (LC50) and 7.9 (LC(99.9)). There were no significant correlations between beetle weights and gamma-cyhalothrin LC50 or LC(99.9), values. A discriminating concentration of 0.005% (AI) gamma-cyhalothrin was chosen to detect any future changes in susceptibility. Results of this study suggest that cyfluthrin can confer cross-resistance to gamma-cyhalothrin in A. diaperinus, but the magnitude of this resistance is unpredictable. Thus, widespread and frequent cyfluthrin use in broiler houses in eastern Australia, which has selected for cyfluthrin resistance, also has resulted in reduced susceptibility to gamma-cyhalothrin. Due to its higher relative toxicity, gamma-cyhalothrin is still potentially useful for management of lesser mealworm, but due to cross-resistance issues, adoption of gamma-cyhalothrin for broiler house use will require a cautious and judicious approach.

Topics: Animals; Body Weight; Coleoptera; Housing, Animal; Insecticide Resistance; Insecticides; Larva; Lethal Dose 50; Nitriles; Pyrethrins

Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m x 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m x 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides.

Topics: Agriculture; Insecticides; Mississippi; Nitriles; Pyrethrins; Rain; Water Movements; Water Pollutants, Chemical; Water Purification; Wetlands

Jiroft district has subtropical climate and prone to seasonal malaria transmission with annual parasite index (API) 4.2 per 1000 in 2006. Anopheles stephensi Liston is a dominant malaria vector. The monitoring of insecticide susceptibility and irritability was conducted using discriminative dose as described by WHO.. The IV instar larvae were collected from different larval breeding places and transported to the temporary insectary, fed with Bemax and then 2-3 days-old emerged and sugar-fed adults were used for susceptibility and irritability tests employing WHO methods and kits to organochlorine (OC) and pyrethroid (PY) insecticides.. Mortality rates of field strain of An. stephensi were 91.3 +/- 0.14 and 90 +/- 0.47% to DDT and dieldrin, respectively at one hour exposure time but was susceptible to all pyrethroids tested. The average number of take-offs per min per adult was 2.09 +/- 0.13 for DDT, 0.581 +/- 0.05 for dieldrin, 1.85 +/- 0.08 for permethrin, 1.87 +/- 0.21 for lambda-cyhalothrin, 1.53 +/- 0.13 for cyfluthrin, and 1.23 +/- 0.1 for deltamethrin.. Currently, deltamethrin is being used for indoor residual spraying against malaria vectors in the endemic areas of Iran. The findings revealed that the main malaria species is susceptible to all pyrethroids including deltamethrin, permethrin, cyfluthrin and lambda-cyhalothrin but was tolerant to DDT and dieldrin. This report and the finding are coincided with results of previous studies carried out during 1957-61 in the same area. Irritability tests to OC and PY insecticides revealed the moderate level of irritability to DDT compared to pyrethroids and dieldrin. Monitoring for possible cross-resistance between OC and PY insecticides should come into consideration for malaria control programme.

Topics: Animals; Anopheles; DDT; Dieldrin; Drug Tolerance; Insect Vectors; Insecticide Resistance; Insecticides; Iran; Malaria; Mosquito Control; Nitriles; Permethrin; Pyrethrins

We investigated the residual efficacy of four insecticide formulations used in Chagas disease vector control campaigns: cyfluthrin 12.5% suspension concentrace (SC), lambda-cyhalothrin 10% wettable powder (WP), deltamethrin 2.5% SC, and 2.5% WP on four types of circular blocks of wood, straw with mud, straw with mud painted with lime, and mud containing 5% of cement. Three concentrations of these insecticides were tested: the LC90 (previously determined on filter paper), the double of the LC90, and the recommended operational dose. For each bioassay test, 15 third-stage nymphs of Triatoma infestans (Klug) (Hemiptera: Reduviidae) were exposed for 120 h to each treatment at 24 h, 30, 60, 90, and 180 days post-spraying. Mortality rates, moulting history and behaviour were recorded at 24, 48, 72, and 120 h of exposure. Mortality rates were highest during the first 30 days post-spraying. Highest mortality rates (above 50%) were observed for deltamethrin 2.5% SC and lambda-cyhalothrin 10% WP on wood blocks up to three months post-spraying. Mud was the substrate on which treatments showed lowest persistence, with the other two substrates showing intermediate residual efficacy of all treatments. During the first 30 days WP formulations were not as effective as SC flowable formulations but, overall in the longer term, WP gave grater mortality rates of T. infestans nymphs exposed at up to six months post-spraying. Porous surfaces, especially mud, showed most variability presumably due to absorption of the insecticide. In contrast the less porous surfaces (i.e. wood and lime-coated mud) kept mortality rates high for longer post-treatment, irrespective of the insecticide concentration used.

Topics: Animals; Insect Vectors; Insecticides; Nitriles; Pesticide Residues; Pyrethrins; Time Factors; Triatoma

Type II pyrethroids are a group of insecticides largely used in agriculture and public health. The nervous system is the main target for pyrethroids in insects and mammals. One notable form of toxicity associated with over exposure has been a facial cutaneous paraesthesia and irritation-related respiration symptoms including behavioural excitation mainly observed in workers spraying pyrethroids or in occupational settings. In acutely exposed rats, type II pyrethroids produce a severe syndrome characterized by salivation and choreoathetosis. Because many of the acute functional effects of type II pyrethoids can be associated with the neurotoxic effect on 5-hydroxytryptamine (5-HT) neurones, the objective of the present study was to examine whether deltamethrin, cyfluthrin and lambda-cyhalothrin administration results in changes of 5-HT content in rat brain. Characterizing this target will help us to better understand the toxicological effects of type II pyrethroids.. Rats were injected with either corn oil or pyrethroids (deltamethrin, 20 mg/kg per day, i.p., for 6 days; cyfluthrin, 14 mg/kg per day, i.p., for 6 days; lambda-cyhalothrin, 8 mg/kg per day, i.p., for 6 days). The frontal cortex, hippocampus, midbrain and striatum were removed at 24 hours post treatment and were analysed for content of 5-HT and 5-HIAA using a HPLC method with electrochemical detection.. A serotonin depleting effect was produced by these type II pyrethroids. The concentration of 5-HT and its metabolite 5-HIAA decreased in the brain regions from pyrethroid treated animals. Pyrethroids accelerated the turnover of 5-HT in midbrain and striatum areas. It is concluded that pyrethroids affect serotonin neurotransmission.

Topics: Analysis of Variance; Animals; Brain Chemistry; Chromatography, High Pressure Liquid; Hydroxyindoleacetic Acid; Insecticides; Male; Models, Animal; Nitriles; Pyrethrins; Rats; Rats, Inbred WF; Receptors, Serotonin, 5-HT1; Serotonin; Serotonin Antagonists

The hyperactivity, incoordination, recovery, and mortality produced by four alpha-cyanopyrethroids usually used for Chagas disease vector control (beta-cypermethrin, beta-cyfluthrin, lambda-cyhalothrin, and deltamethrin) were evaluated on third instar nymphs of Rhodnius prolixus. All pyrethroids modified the locomotor activity of the nymphs, which increased linearly as a function of the log of insecticide concentration. lambda-Cyhalothrin showed the lowest values of Effective Concentration 50%, Lethal Concentration 50%, Effective Time 50%, and Lethal Time 50% when insecticides were applied by contact with treated filter papers. Recovery from incoordination was observed after topical application of the insecticides. The recovery was inhibited by the simultaneous application of piperonyl butoxide, suggesting that biotransformation by mixed-function microsomal oxidases is involved in the process of recovery.

Topics: Animals; Insect Control; Insecticides; Lethal Dose 50; Linear Models; Motor Activity; Nitriles; Nymph; Pyrethrins; Rhodnius

The efficacy of various pyrethroid insecticides for use on odour-baited targets to control tsetse was compared in Zimbabwe. Formulations were applied to cotton cloth and polyester net and, at various intervals, the materials were bioassayed by exposing fed female Glossina pallidipes (Austen) (Diptera: Glossinidae) to cloth for 45 s or by inducing them to collide briefly with net. Trial formulations were compared with deltamethrin suspension concentrate (s.c.), the insecticide currently used in tsetse control operations in Zimbabwe. Applying 0.8% suspension of alphacypermethrin to cloth or net produced high mortalities for 9 months which was similar in performance to 0.4% suspension of deltamethrin s.c. Deltamethrin s.c. and beta-cyfluthrin s.c. applied to cloth as 0.1% suspensions were equally effective, producing high mortalities for 2 months during the wet season, and 0.8% suspension of beta-cyfluthrin was effective for 12 months. Suspensions of 0.1% lambdacyhalothrin capsule suspension or 0.1% lambdacyhalothrin wettable powder were significantly less effective than 0.1% deltamethrin s.c. Chemical analyses showed that increasing the concentration of insecticide applied to material increased the initial amount of insecticide on the material and decreased the subsequent rate of loss; 0.1% suspension of beta-cyfluthrin s.c. applied to cloth produced an initial concentration of approximately 280 mg/m2 which declined by 94% in 12 months whereas 0.8% suspension showed no significant decrease in concentration (mean= 1304 mg/m2) over the same period. For controlling tsetse by means of pyrethroid-treated targets, it is suggested that beta-cyfluthrin s.c. is as effective as deltamethrin s.c. but that alphacypermethrin s.c. should be used at twice the concentration of deltamethrin s.c. to obtain the same performance.

Topics: Animals; Insect Control; Insecticides; Nitriles; Odorants; Pyrethrins; Tsetse Flies