The Entomological Efficacy of Piperonyl Butoxide (PBO) Combined with a Pyrethroid in Insecticide-Treated Nets for Malaria Prevention: A Village-Based Cohort Study Prior to Large-Scale Deployment of New Generation Mosquito Nets in Burkina Faso

The efficacy of insecticide-treated nets (ITNs) is increasingly compromised by the prevalence of malaria vectors resistant to pyrethroids. In response to this issue, a new generation of ITNs has been developed that incorporate synergistic components, such as piperonyl butoxide (PBO). The purpose of this study is to provide entomological evidence for the efficacy of a PBO-based ITN brand at the village level, serving as a basis for decision-making before large-scale net deployment. During the high malaria transmission period, ITNs were distributed in each group and vector sampling was conducted biweekly in selected households. Bionomic data were collected to assess the resistance of wild An. gambiae populations to various chemical insecticides. There was a significant disparity in total An. gambiae sl. collected between the ITN arms, the intervention arm (ITN arms), and the control arm (P = 0.003). An. coluzzi was identified as the predominant species in the study area, as confirmed by PCR analysis. Analysis of the blood-feeding inhibition rate revealed that 100% permethrin + PBO ITN exhibited significantly greater inhibition than 66.81% permethrin only ITN. According to the log-time probit regression analysis, permethrin exhibited a knockdown time of 256 min without synergists, while it decreased to 139 min (P = 0.001) when pre-exposed to PBO. The evidence from this trial supports the use of PBO ITNs over standard ITNs for pyrethroids to combat pyrethroid resistance and improve protection against malaria for both individuals and communities, particularly in areas with high pyrethroid resistance.

Scale and Associated Factors of Using Pyrethroid-Impregnated Mosquito Nets as Fishing Tools on Nokoué Lake within Sô-Ava Municipality in Benin, 2020

Background: In lacustrine communities, whether in Benin or elsewhere, populations use impregnated mosquito nets (IMNs) as fishing nets. This depletes the lake of its fishery resources, which in turn are contaminated by the pyrethroids impregnated in the nets. This study aims to determine the scale and factors associated with the use of pyrethroid-impregnated mosquito nets as fishing tools in the municipality of Sô-Ava in Benin. Methods: This is a cross-sectional and analytical study with two components. First, a quantitative component was made up of 280 volunteers who were interviewed in the seven districts of the city. Data collection was done in two phases: the first from September to October 2020, and the second in August 2022. Data were analyzed with Stata and logistic regression was used. Another qualitative component was made up of forty participants chosen by reasoned choice, of which 32 were split into four focus groups of eight members each, and the rest participated in semi-structured interviews. Triangulation of the different sources was used to analyze the data. Results: Around 67% of the population reported using impregnated mosquito nets as fishing tools and 33% exclusively for malaria. Seasonal fishermen (ORa = 2.03, CI = 1.35 - 4.97, P = 0.004) and years of professional experience (ORa = 1.53, CI = 1.00 - 2.05, P = 0.021) increase the risk of using these nets as fishing tools. The use of insecticide-treated mosquito nets against mosquitoes causes skin scratching and impairs breathing because of the impregnation products, as reported by respondents. Conclusion: A high prevalence of inappropriate use of impregnated mosquito nets in fishing practices is highlighted in this study. Interviews in the field revealed that nets are diverted for fishing purposes to increase the volume of catches. Consequently, it will be appropriate to assess the pyrethroid content in water and fishery products.

Determination of 10 Pyrethroids Pesticide Residues in Rice by GC-MS-MS

[Objective] A method was developed for the determination of 10 pyrethroids pesticide residues in rice by GC-MS-MS. [Method] Pyrethroids were extracted with acetonitrile, followed by a salting-out step with anhydrous magnesium sulfate and sodium chloride, cleaned up by florisil solid phase extraction （SPE） cartridge, and determined by multiple reaction monitoring mode. [Result] The method showed good linearity over the range of 0.010-0.500 mg/L for 10 pyrethroid pesticide with correlation coefficients over 0.99. The detection limits were 0.005 -0.010 mg/kg. The method was validated by analyzing samples spiked with 0.05, 0.10, 0.20 mg/kg of 10 pyrethroid pesticides, respectively. The average recoveries in rice ranged from 75.0-115.5%, and the relative standard deviations （RSD） were between 3.9%-6.9%. [Conclusion] The method is easy, accurate and reliable, which can meet the requirement for the simultaneous determination and confirmation of pyrethroid pesticide residues in rice.

Acute Toxicity of Two Pyrethroids Insecticides on Brachionus calyciflorus

[ Objective] The paper was to study the 24 and 48 h acute toxicity of common pyrethroid insecticides of eypermethrin and deltamethrin on Brachionus calyciflorus. [ Method ] With Guangzhou strain of B. colyciflorus as test animal, the standard toxicity test method was used to carry out acute toxicity test, and LC50 of cypermethrin and deltamethrin on rotifer was determined using probit method. [ Result ] LC50 of cypermethrin on rotifer was 3 376.87 and 5.87 μg/L at 24 and 48 h, respectively, and those of deltamethrin on rotifer was 594.56 and 74.17 μg/L, respectively. [Condusion] Acute toxicity of cypermethrin and dehamethrin on rotifer at 24 and 48 h was different, LC50 of cypermethrin and deltamethrin on rotifer at 48 h was more sensitive to monitor the chemical pollutants in water body than LC50 at 24 h.

Estrogenic activities of two synthetic pyrethroids and their metabolites

Synthetic pyrethroids （SPs） are among the most common pesticides in current use, and so far, several SPs have been assessed for their potential estrogenicities by various methods. Previous studies have shown that the estrogenicities partly come from their metabolites. Although considerable information is available with respect to the metabolism and environmental degradation of SPs, little is known about the estrogenicities of the metabolites. In this study, permethrin （PM） and β-cypermethrin （CP）, as well as their metabolites （3-phenoxybenzoic alcohol （PBCOH）, 3-phenoxybenzaldehyde （PBCHO） and 3-phenoxybenzoic acid （PBCOOH） were evaluated for their estrogenic activities in the MCF-7 human breast carcinoma cell line. In the MCF-7 cell proliferation assay, PM and CP exhibited significant estrogenic activities at 10-7 mol/L, comparable to 17β-estradiol （E2） of 10-9 tool/L, with the relative proliferative effect ratios of 55.4% and 56.3%, respectively. The real-time quantitative polymerase chain reaction （qRT-PCR） results confirmed the estrogenicities of PM and CP with significant alteration of pS2 and ERα mRNA levels observed at 10-6 mol/L. For the three major metabolites, PBCOH and PBCOOH exhibited estrogenic activities in all assays, while no significant estrogenic responses was observed for PBCHO compared to the vehicle control. In particular, PBCOH had even slightly stronger estrogenic activity than its parent compounds, indicating that metabolism may be one of the reasons for the estrogenicities of the SPs. Given the widespread use of SPs, the toxicological effects of parent compounds and their metabolites should be taken into consideration in the risk assessment of SPs.

Comparison of Two Procedures for Extraction and Clean-up of Organophosphorus and Pyrethroid Pesticides in Sediment

Two procedures were compared for extraction and clean-up of 20organophosphorus and 19 pyrethroid pesticides in sediment to identify the more effective procedurefor groups of pesticides or individual compounds. In Procedure I, methanol/water and n-hexane wereused for extraction, and 1:10 (v/v) dichloromethane in n-hexane and acetone were used as eluents foreluting the analyte through the cartridge, with one evaporating steps on a rotary evaporator andtwo eluting steps on the cartridge. n-hexane/acetone (2:1, v/v) was used for extraction and elutionin Procedure II with one evaporating step on a rotary evaporator and one eluting step on thecartridge. All extractions were performed under an ultrasonic bath and gas chromatography and massspectrometry were utilized for measurements. Procedure II was developed as a rapid, timesaving, lesscostly and safer substitute for Procedure I which was an old method. Procedure II was moreeffective for almost all the organophosphorus pesticides tested and 11of the 19 pyrethroidpesticides, while Procedure I was more appropriate for analysis of 5 pyrethroid pesticides. However,recoveries of most pyrethroid pesticides were fairly low. Thus, further studies should focus onadjustment and formulation of solvents for more efficient extraction and clean-up of pyrethroidpesticides from sediment samples.

Synthesis and Biological Activity of New Pyrethroid Acid Oxime-esters Containing Pyrazole Ring

A series of compounds containing oxime-ester linkage and pyrazole ring(in place of the ester linkage and the alcohol moiety in pyrethroid ester) was designed and synthesized. The structures of all the compounds prepared were confirmed by 1H NMR and MS spectroscopy as well as elemental analyses. The bioassay data of those compounds against tobacco mosaic virus(TMV), cucumber mosaic virus(CMV), potato virus X(PVX) and potato virus Y(PVY) were presented. Among them compound 6i was found to possess significant plant antiviral activities. But all the compounds showed low insecticidal and acaricidal activities.

Theoretical Study on the Photodegradation Mechanism of Pyrethroid Insecticide Fenvalerate in Water

The photodegradation mechanism of fenvalerate in water has been investigated by density functional theory（DFT）.The geometries of reactants,transition states,intermediates and products are optimized at the B3LYP/6-31G＊ level.The calculated results indicate that the reaction process mainly includes the nucleophilic attack and the substitution reaction by hydroxyl radical to the carbonyl group.By vibrational frequency analysis and intrinsic reaction coordinate（IRC） method,the transition state and its reaction pathway are confirmed.Moreover,the changes of natural population analysis（NPA）,calculated using the Natural bond orbital（NBO） method,are analyzed along with the degradation reaction which can explain the variation of chemical bonds.Additionally,the solvent effect is also investigated and the results show that the reaction preferably takes place in water.

A new household ultrasonic cleaning method for pyrethroids in cabbage

Pyrethroid is widely used in developing countries and is a potential threat to human health.So putting forward an effective pyrethroid cleaning method is of vital importance.Clearance of fenpropathrin,cypermethrin and deltamethrin in cabbage by using ultrasonic treatment accompanied with different baking soda concentrations were investigated in this study.The results of response surface methodology showed that the maximum clearance rate was 70.61% for fenpropathrin under the optimal power,treated time,treated temperature and baking soda concentration,which were 260.02 W,10 min,20.15◦C and 0.014 g/mL,respectively.Similarly,the maximum removal efficiency was 73.72% for cypermethrin under 240 W,13.84 min,19.53℃ and 0.014 g/mL,and 92.15%for deltamethrin under 238.99 W,12.42 min,25℃ and 0.013 g/mL.The clearance rate of pyrethroid by this method was significant higher(P<0.05)than traditional cleaning methods(bathing and running water washing).The contents of the compositions such as vitamin C,total soluble sugar,protein and dietary fiber,texture and sensory evaluation of cabbage were not found obvious changes after the ultrasonic treatment combined with baking soda(P>0.05).Results showed that ultrasonic treatment combined with baking soda was an effective way to eliminate the fenpropathrin,cypermethrin and deltamethrin in cabbage without influencing cabbage quality.

Pyrethroid Insecticide Resistance <i>kdr</i>Gene in the House Fly, <i>Musca domestica</i>(Diptera: Muscidae), in the United Arab Emirates

The house fly, Musca domestica L., is a very important insect because of its role as a vector of several human, livestock, and poultry diseases. Different groups of insecticides, including the pyrethroids, are used to control house flies. The objective of the current study was to conduct a survey of the kdr insecticide resistance gene in the house fly population in the United Arab Emirates (UAE). Flies were collected from five locations (Abu Dhabi, Dubai, Fujairah, Ajman, and Ras Al- Khaymah). Genomic DNA was extracted and polymerase chain reaction (PCR) amplification of specific allele (PASA) was performed. The maximum percentage (70%) of homozygous genotype (kdr/kdr) occurred at Ajman, followed by Dubai (59.5%), and the minimum percentage occurred at Ras Al-Khaymah (14.3%). Resistant insects of the genotype kdr/kdr were detected in all of the tested house fly populations. Ajman and Fujairah house fly populations were in Hardy-Weinberg equilibrium. The resistance kdr allele was found at a high frequency (0.54 - 0.8) at all locations except at Ras Al-Khaymah (0.21). Together, this study demonstrated that the pyrethroid insecticide resistance kdr allele was found in UAE house fly populations, strongly suggesting that a countrywide pyrethroid insecticide resistance management program needs to be implemented.

Time and Dose-related Effects of the Pyrethroid Fluvalinate on Haemolymph Carbohydrates and Gut Lipids of Honeybees,Following in vivo Injection of very Low Doses

The injection to emerging adult workerbees with fluvalinate doses ranging from 1 femtomol to 1 nanomol per individual resulted in a reduction of haemolymph carbohydrate concentrations, particularly at the lowest dose 1 hour after injections. At the same time, a large increase was observed for triacylglycerols and to a much lesser extent for steroids and phospholipids with 0.1 picomol per bee. By contrast, fatty acids, steroids and triacylglycerols exhibited a depress at the higher dose. Most responses were thus biphasic, showing that much attention should be paid to the effects of very low doses of pesticide.

First investigation of deltamethrin pyrethroid susceptibility and resistance status of Anopheles labranchiae(Falleroni, 1926), potential malaria vector in Tunisia

Objective: To evaluate the deltamethrin pyrethroid insecticides against Anopheles labranchiae, potential malaria vector in Tunisia.Methods: Six field populations of Anopheles labranchiae mosquitoes were collected from six localities in Northern and Central Tunisia between October and November 2016.Different bioassays were performed to estimate the level of resistance in each collected population. Two synergists were used to estimate the involvement of detoxification enzymes in insecticide resistance.Results: All studied strains were resistant and the RR50 ranged from 12.5 in sample #1 to72.5 in sample #6. Synergist tests using piperonyl butoxide indicated the involvement of monoxygenases enzymes in the recorded resistance. In contrast, the increase of deltamethrin mortality was not significant in presence of S,S,sributyl phosphorothioate(0.8 < SR < 1.2), suggesting no role of esterases(and/or GST) in the resistance phenotype. The correlation recorded between mortality due to DDT and the LC50 of deltamethrin insecticide indicated an insensitive sodium channel affected by Kdr mutation(Spearman rank correlation, r =-0.59, P < 0.01).Conclusions: These results should be considered in the current mosquitoes control programs in Tunisia. The use of pesticides and insecticides by both agricultural and public health departments in Tunisia should be more rational to reduce the development of resistance in populations. Different insecticide applications should be implemented alternately.

Separation of chlorinated hydrocarbons and organophosphorus, pyrethroid pesticides by silicagel fractionation chromatography and their simultaneous determination by GC-MS

A silicagel fractionation procedure for environmental sample extracts, which separates chlorinated hydrocarbons(CHCs) and organophosphorus, pyrethroid pesticides into two groups for subsequent instrumental analysis, was developed in this study. This method was achieved by optimizing the fraction cut-off volume of elution and different solvents. Using fully activated silica gel and cut-off CHCs collection after 10 ml 10% dichloromethane (DCM) in n-hexane passing through the column resulted in satisfactory separation of CHCs and organophosphorus, pyrethroid pesticides. This procedure had a higher reliability for CHCs than for organophosphorus, pyrethroid pesticides, because there is a relatively reliable recovery for CHCs. This approach is less expensive due to reducing sample pre-treatment time and solvent consumption.

Degradation Dynamics of Pyrethroids in Cigarette Production Environment

[ Objective] In order to provide a reference for safe and reasonable use of pyrethroids in cigarette production, the degradation behaviors of three kinds of pyrethroids in cigarette production environment were studied. [ Method ] Three kinds of pyrethroids （permethrin, cyfluthrin and c/s-cypermethrin） were adminis- trated to two media （cut tobacco and iron sheet surface） in cigarette production environment at MRLs concentration, and the first sampling was conducted at 24 d post administration. Afterwards, sampling was performed once every 7 d, with a total of six times. The degradation rates of insecticides in different media were cal- culated, and degradation models were established. [ Result ] The contents of three kinds of insecticides in two media gradually declined with the prolongation of time, and degradation rates presented the trend of fast-slow-fast ; the degradation rates of permethrin, cyfluthrin and c/s-cypermethrin in cut tobacco at 36 d post ad- ministration were 97.14%, 88.89% and 95.38%, respectively; the degradation rates on iron sheet surface were 29.95%, 48.99% and 40. 24%, respectively. The half lives of three kinds of insecticides in cut tobacco were 1 -2 d, while those on iron sheet surface were 6 - 10 d. [ Conclusion] The contents of three kinds of insecticides in two media gradually declined with the prolongation of time, and their degradation regularity accorded with first order kinetic equation.

Neurolemma-Injected Xenopus Oocytes: An Innovative Ex Vivo Approach to Study the Effects of Pyrethroids on Ion Channels in Their Native State

Microtransplantation of rat brain neurolemma into the plasma membrane of Xenopus laevis oocytes is an ex vivo method used to study channels and receptors in their native state using standard electrophysiological approaches.In this review,we show that oocytes injected with adult rat brain neurolemma elicited tetrodotoxin-sensitive inward ion currents upon membrane depolarization,which were increased in a concentration-dependent manner by treatment with the pyrethroid insecticides permethrin and deltamethrin.Under our initial protocols,oocyte health was reduced over time and neurolemma incorporation varied between batches of oocytes from different frogs,limiting the usefulness of the assay for regulatory issues.A collection of changes to the assay procedure,data acceptance criteria,and analysis method yield substantially improved precision and,hence,assay performance.These changes established this ex vivo approach as a toxicologically relevant assay to study the toxicodynamic action of pyrethroids on ion channels in their native state using neurolemma fragments prepared from juvenile and adult rat brains.

Marine bacterium strain screening and pyrethroid insecticide-degrading efficiency analysis

A pyrethroid insecticide-degrading bacterium, strain HS-24, was isolated from an offshore seawater environment. The strain, which can degrade cypermethrin （CYP） and deltamethrin （DEL）, was identified as Methylophaga sp. The optimal culture and degradation conditions for CYP and DEL by strain HS-24 is pH 7 at 28℃. Under optimum culture conditions, strain HS-24 exhibited a broad degradation concentration range of 100, 200, 400, 600, and 800 mg/L for CYP and DEL. The metabolic intermediates were analyzed by NMR, which provided strong evidence that CYP and DEL removal occurred mainly because of a biological process. The toxicity of the degradation products of strain HS-24 was studied simultaneously by measuring the light output of the luminescence bacterium. This demonstrated that the biodegradation ability of strain HS-24 significantly decreased the toxicity of CYP- and DEL-contaminated aquaculture seawater. Finally, the findings of this paper indicate that strain HS-24 is thus revealed as a biological agent for the remediation of marine aquatic environments.

Spontaneous Mammary Carcinomas in Female Dogs: Association between Immunohistochemical Degrees of Neoplasia Aggressiveness and Residual Pyrethroids

Of the tumors diagnosed in the female dogs have the highest mammary neoplasias incidence. These neoplasias can be influenced by environmental contaminants. Despite evidence of pyrethroid toxicity, carcinogenic potential has not yet been sufficiently elucidated, there is a need to investigate their involvement in mammary tumor. In previous studies, pyrethroid residues were detected in female dogs with mammary neoplasia, however was not investigate the influence of this insecticide in the genesis and aggressiveness of mammary cancer. This study aimed to investigate possible relations between pyrethroid residues and aggressiveness of mammary carcinoma in female dogs. Fifty selected female dogs were divided into five groups of 10 animals each: the Control group, female dogs without mammary neoplasia;the groups Luminal A, Luminal B, HER-2 Superexpression and Basal were constituted by female dogs that presented inguinal mammary carcinoma classified immunohistochemically. The aggressiveness of carcinomas was evaluated by immunohistochemistry (HER-2, p63, estrogen receptor). Residual concentrations of the pyrethroids from the mammary gland and fat tissue adjacent to it were determined by HPLC. Data were analyzed by Chi-Square test. Of the all animals, six presented residues of pyrethroids in mammary samples and 10 presented it in fat tissue samples. There was no statistical evidence that pyrethroids are involved in mammary carcinoma aggressiveness in female dogs.

Bronchiolitis Revealing Pyrethroid Poisoning in a 2-Month-Old Infant

Despite the widespread domestic use of pyrethroid insecticides, very few cases of poisoning are reported in the literature, especially in children. The manifestations are generally benign, and the management is controversial. We report a case of severe intoxication in a 2-month-old infant, initially treated as bronchiolitis, which progressed favorably under atropine. This case illustrates on the one hand the importance of looking for the notion of a spray in the sudden onset of respiratory distress in the infant, and on the other hand monitoring any intoxication with pyrethroids in a small infant in order to consider a treatment with atropine sulfate in case of the occurrence of a muscarinic syndrome.

Evaluation at the Level of Health Facilities, of the Protective Efficacy of LLINs in Children under 5 Years Old from Localities of Low and High Resistance of Vectors to Pyrethroid Insecticides in Benin in West Africa

Context: The resistance to pyrethroids in malaria vectors continues to grow in Africa and could therefore compromise or reduce substantially the effectiveness of LLINs in preventing malaria. It is therefore of paramount importance to evaluate the protective efficacy of LLINs in children sleeping in areas of vector resistance to insecticides in order to draw lessons for future interventions. This study assesses the effect of the use of LLINs on malaria morbidity in clusters of low and high resistance of vectors to pyrethroids. Methods: This is a cross-sectional case-control study with one control for one case that was conducted in the communes of Kétou, Ifangni, Kétou, and Pobè in the Plateau department of southern Benin. The use of LLINs and malaria morbidity was measured and compared in children from clusters of low and high vector resistance to insecticides. In each commune, 30 cases and 30 controls were recruited for a total of 240 children under 5 years of age from villages with low and high insecticide resistance. Results: According to the localities of origin of the children, of all parents of children surveyed, 169 (70.4%) asserted the children slept under an LLIN the day before they arrived at the health center. This rate represents 70.8% (85 children) among the cases and 70.0% (84 children) among the controls without significant difference (p = 0.8). The use of LLINs the day before the survey, the frequency of their use during the two weeks preceding the day of the survey, their availability at the household level, the use of other tools for protection against mosquito bites are the same in the two groups of children (cases and controls) (p > 0.05) as well in low and high resistance villages. On the other hand, the parasite prevalence, the splenomegaly and the geometric means of the parasite densities, are significantly higher in the cases than in the controls (p Conclusion: The evaluation of epidemiological indicators in children under five years old at the level of health centers did not enable demonstrating the impact of resistance on the operational effectiveness of the LLINs. The information collected within the four health facilities only reflects the situation that should normally be seen in the population under the real conditions of use of LLINs in high and low resistance areas.

Determination of Organochlorine and Synthetic Pyrethroid Pesticide Residues in Water Samples Collected from Different Locations of Bangladesh

The present study was aimed to validate an analytical method for the quantification of 19 organochlorine and 2 synthetic pyrethroid pesticide residues in water samples using modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction and Gas Chromatography coupled with Electron Capture Detector (ECD). The selected pesticide residues were determined by in-house validated method. The analytical method was validated by evaluating the accuracy, precision, linearity, limit of detection (LOD) and limit of quantification (LOQ). The average recoveries of the selected pesticides ranged from 78% to 117% with RSDr ≤ 12% in two fortification levels of 0.02 and 0.1 mg/L. The linearity was ≥0.995 for all of the selected pesticides. The LOD ranged from 0.003 to 0.006 mg/L and the LOQ was 0.02 mg/L for all the selected analytes. This method was applied satisfactorily for the residue analysis of 108 water samples collected from nine districts of Bangladesh. Among the analyzed samples, only 4 had cypermethrin residues (0.026 mg/L, 0.034 mg/L, 0.045 mg/L and 0.05 mg/L). The level of detected cypermethrin residues were above the WHO recommended guide line values of water quality.