The association between knockdown resistance and treatment outcome of 1% permethrin lotion in head lice infestations in Nonthaburi province, Thailand.

Head lice infestations significantly impact schoolchildren, with permethrin being the primary treatment. The escalation in the prevalence of the knockdown resistance (kdr) mutation, potentially affecting treatment efficacy, is highly concerning. This study examined head lice infestation prevalence, the efficacy of 1% permethrin lotion, kdr mutation frequency, and the association between kdr genotype and permethrin treatment outcomes in schoolchildren in Nonthaburi province, Thailand. Participants and lice samples were collected from six primary schools using cluster sampling. Clinical outcomes and adverse events were assessed on days 7 and 14 post-treatment. Kdr mutations (T917I) in head lice samples were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Head lice infestation prevalence was 6.1%, with a kdr mutation frequency of 63.2% and a permethrin cure rate of approximately 50%. Multivariate regression analysis revealed the association between kdr genotype and clinical response to permethrin treatment (Odds Ratio (OR) = 13.15, p = 0.005). The presence of resistance genes hinders the cure rate (presence 35.9% versus absence 85.7%). These findings highlight the importance of the kdr genotype in predicting permethrin treatment responses in head lice infestations. Furthermore, in regions with documented reduced permethrin efficacy and a high prevalence of kdr mutations, alternative non-pyrethroid-based pediculicides should be considered. This research could help improve the control of head lice infestations, especially in problematic areas of Thailand.

Understanding Perceptions and Experiences on Acceptability of Oral Ivermectin, Topical Permethrin, and their Combination in the Treatment of Adult Filipino Patients with Scabies: A Multiple Case Study.

Background and Objective: Oral ivermectin, a broad-spectrum anti-parasitic drug, alone or in combination with permethrin, may be a cheaper and more convenient alternative drug to topical permethrin alone in the treatment of classic scabies. There are no previous studies on the treatment acceptability of the three interventions among individual patients with scabies in the Philippines.The purpose of this study was to understand the experiences and perceptions on treatment acceptability for oral ivermectin, topical permethrin or combination treatment among patients with scabies using the multiple-case study approach. Methods: We conducted a qualitative multiple case study among adult Filipino patients with classic scabies who were prescribed oral ivermectin, topical permethrin or its combination at a government tertiary hospital dermatology outpatient clinic from December 2022 to September 2023. Semi-structured interviews were used as the primary source of data and analyzed together with chart reviews, Dermatology Life Quality Index (DLQI) scores, and clinical images. Interviews were transcribed, coded, and triangulated with other secondary data. A three-person research team employed a reflexive and iterative process of familiarization, coding, and thematic analysis using a modified Theoretical Framework of Acceptability (TFA) to generate case descriptions, within-case analyses, and cross-case syntheses. Results: The acceptability of scabies treatments (permethrin, ivermectin, and combination therapy) was generally positive. Permethrin, used in three patient cases, was generally perceived as effective but itch relief varied. The burden of whole-body application of permethrin was context-dependent, influenced by living arrangements and family support. Perceived affordability of permethrin was linked to socioeconomic status. Ivermectin, used by one patient case, was perceived as highly effective with no side effects. Its single dose use did not interfere with patient routine. Combination therapy was also considered effective but potential antagonistic effects and the cost of adding permethrin made it less preferred. Reluctance in taking oral pills was noted. All patients valued medical advice and deferred to their physicians for treatment decisions. Conclusion and Recommendations: All three treatment options were considered effective and safe. Patients generally preferred permethrin over oral ivermectin due to its topical nature and perceived lower side effects. However, affordability and logistical challenges, especially for large households and low-income families, were noted with permethrin. Oral ivermectin elicited hesitation due to its controversial role in COVID-19 and veterinary use. Concerns about added costs and potential antagonism in combination therapy were raised. Despite these considerations, patients ultimately relied on physicians for treatment decisions. This study underscores the importance of understanding patient perspectives, experiences, and the patient-physician relationship in choosing scabies interventions. Addressing patient concerns, providing education, and ensuring ease of use and affordability can enhance treatment acceptability and adherence for better outcomes.

Escalating Threat of Drug-Resistant Human Scabies: Current Insights and Future Directions.

Background: Scabies is a prevalent dermatological condition with significant public health implications. The recent rise in drug-resistant scabies presents new challenges for effective disease management and control. Methods: A comprehensive literature review was conducted using PubMed, Cochrane Library, and Web of Science. Studies published from 2000 to August 2024 were considered, focusing on those reporting drug-resistant scabies and advancements in treatment approaches. Results: Clinical studies, in vitro investigations, and case reports show significant resistance of human scabies to permethrin. Main resistance mechanisms involve genetic mutations in the mites' voltage-gated sodium channels (VGSCs) and enhanced activity or expression of the detoxifying enzyme glutathione S-transferase (GST). Resistance to ivermectin and benzyle benzoate, although suggested by some authors, seems less obvious. The clinical evidence of widespread ivermectin resistance in human scabies infestations is lacking, despite indications of increased tolerance in laboratory settings and anecdotal reports of resistance in patients with crusted scabies. Benzyl benzoate resistance in scabies mites remains unconfirmed. Conclusions: Permethrin-resistant scabies is an escalating threat requiring new management strategies and updated guidelines. Infection control measures, alternative treatments, and ongoing research into new therapeutics are crucial to mitigate the impact of drug-resistant scabies.

Longitudinal evaluation of structural brain alterations in two established mouse models of Gulf War Illness.

Gulf War Illness (GWI) affects nearly 30% of veterans from the 1990-1991 Gulf War (GW) and is a multi-symptom illness with many neurological effects attributed to in-theater wartime chemical overexposures. Brain-focused studies have revealed persistent structural and functional alterations in veterans with GWI, including reduced volumes, connectivity, and signaling that correlate with poor cognitive and motor performance. GWI symptomology components have been recapitulated in rodent models as behavioral, neurochemical, and neuroinflammatory aberrations. However, preclinical structural imaging studies remain limited. This study aimed to characterize the progression of brain structural alterations over the course of 12 months in two established preclinical models of GWI. In the PB/PM model, male C57BL/6 J mice (8-9 weeks) received daily exposure to the nerve agent prophylactic pyridostigmine bromide (PB) and the pyrethroid insecticide permethrin (PM) for 10 days. In the PB/DEET/CORT/DFP model, mice received daily exposure to PB and the insect repellent DEET (days 1-14) and corticosterone (CORT; days 7-14). On day 15, mice received a single injection of the sarin surrogate diisopropylfluorophosphate (DFP). Using a Varian 7 T Bore MRI System, structural (sagittal T2-weighted) scans were performed at 6-, 9-, and 12-months post GWI exposures. Regions of interest, including total brain, ventricles, cortex, hippocampus, cerebellum, and brainstem were delineated in the open source Aedes Toolbox in MATLAB, followed by brain volumetric and cortical thickness analyses in ImageJ. Limited behavioral testing 1 month after the last MRI was also performed. The results of this study compare similarities and distinctions between these exposure paradigms and aid in the understanding of GWI pathogenesis. Major similarities among the models include relative ventricular enlargement and reductions in hippocampal volumes with age. Key differences in the PB/DEET/CORT/DFP model included reduced brainstem volumes and an early and persistent loss of total brain volume, while the PB/PM model produced reductions in cortical thickness with age. Behaviorally, at 13 months, motor function was largely preserved in both models. However, the GWI mice in the PB/DEET/CORT/DFP model exhibited an elevation in anxiety-like behavior.

Effects of permethrin-treated uniforms on tick submissions to a military passive tick surveillance program.

Permethrin-treated clothing is often recommended as a first line of defense against tick-borne diseases. In 2012, the permethrin factory-treated Army Combat Uniform was first made available to active duty Soldiers, Army National Guard, Army Reserve Enlisted Soldiers, and the Senior/Junior Reserve Officers Training Corps. Subsequently, Air Force and Marine Corps personnel were also offered permethrin factory-treated uniforms. Here, we use the passive surveillance data collected through the Military Tick Identification/Infection Confirmation Kit (MilTICK) program to determine the effectiveness of permethrin-treated uniforms at protecting Department of Defense personnel from exposure to tick-borne pathogens in the United States. We analyzed whether submissions by self-reported users of the permethrin-treated uniforms had smaller proportions of engorged ticks, certain cohorts of MilTICK users were better protected than others, and specific tick species were better repelled than others. We found that permethrin use resulted in significantly lower proportions of engorged ticks submitted across MilTICK users. Army and Army National Guard personnel reported more permethrin-treated uniform use than other services. For submissions from active duty personnel serving in uniform, the proportion of tick engorgement in the presence of permethrin increased over time, possibly indicating that permethrin-treated uniforms suffer from reduced performance over the life of the garment. We also found that while permethrin reduced all tick species' ability to feed until engorgement or repletion, blacklegged tick adult females were better able to resist permethrin's lethal effects than lone star tick and American dog tick adult females. Permethrin-treated clothing plays an important role in keeping military personnel safe from tick-borne diseases.

Investigation of the in-vitro lethal effect of spilanthol on demodex and finding the most effective dose.

Demodex species are associated with many dermatological diseases, so an acaricidal agent that is effective against them and safe for skin applications may benefit many diseases. This study aims to investigate the anti-demodex potential of spilanthol, a product obtained from the Spilanthes Acmella plant, by determining the minimal effective dose for the first time in the literature. Demodex mites were obtained from 70 patients with standard superficial skin biopsy. Spilanthol extract was used at 1%, 2%, 3%, 4%, and 5%. Standard immersion oil was used for the negative control, and permethrin 5% was used for the positive control group. The dependent variable is the survival time of the mite. Comparisons with the negative control group, the anti-demodex effect demonstrated itself in all groups, creating a statistically significant difference (p < 0.001). The positive control group, had 3%, 4%, and 5% spilanthol rates which were very similar to the results with 5% permethrin (p > 0.05). Higher concentrations than 3% did not make any additional contribution to survival times. This is the first attempt to show the dose-dependent acaricidal effect of spilanthol on demodex mites. Even the 3% dose shows similar results to 5% permethrin, and no additional effect increase was observed at higher doses. Therefore, in vivo, studies may be planned with a 3% spilanthol dose for further studies.

BASELINE SUSCEPTABILITY AND FIRST OBSERVATION OF KNOCKDOWN RESISTANCE IN AEDES TAENIORHYNCHUS POPULATION OF ST. JOHNS COUNTY, FLORIDA.

The black saltmarsh mosquito, Aedes taeniorhynchus, is a prominent nuisance mosquito within St. Johns County, Florida. Due to their characteristically large outbreaks, and the elevated amount of insecticide application correlated with the outbreaks, local populations of Ae. taeniorhynchus are at an increased risk of developing insecticide resistance. This study was established to form a baseline susceptibility of Ae. taeniorhynchus against two technical grade materials, permethrin, and chlorpyrifos. Centers for Disease Control and Prevention bottle bioassays were conducted with technical-grade materials during two outbreaks in the fall of 2023. Results indicated a baseline susceptibility against the materials tested, but most notably, the phenotypic expression of knockdown resistance (kdr) was observed. Results highlight the need for continued monitoring and investigation into the resistance status and resistance level of this common Florida species.

Exposure of Young Children to Permethrin and Cypermethrin Insecticides in the Residential Environment.

The aims of this study were to evaluate the exposure to permethrin and cypermethrin of young children aged between 2 and 5 years in Nakhon Pathom and Sing Buri provinces, Thailand. A questionnaire that included general demographic information, household characteristics, insecticide usage and exposure-related behavior in children was used to interview parents or family caregivers. Permethrin and cypermethrin concentrations on floor surfaces and children's hands, as well as their urinary metabolites, were analyzed by gas chromatography coupled with mass spectrometry. The results showed that permethrin and cypermethrin were detected in 62% and 83% of the children's hand wipe samples, with geometric mean (GM) levels of 0.02 µg and 0.04 µg, respectively. Permethrin and cypermethrin were detected in 79% and 93% of floor surface wipe samples, with GM levels of 0.90 µg/m2, and 1.49 µg/m2, respectively. For children's urine, the GM concentrations of cis- and trans-DCCA, 3-PBA, and total pyrethroid metabolites were 0.84, 0.31 and 1.23 nmol/g creatinine, respectively. This study found that household insecticide product usage and having a tile floor were associated with increased permethrin concentrations on the children's hands and floor surfaces. However, cypermethrin concentrations on floor surfaces were significantly higher in families using aerosol insecticide sprays and insecticide products in the living room and bedroom. The predictors of the total pyrethroid, DCCA and 3-PBA metabolites are permethrin on children's hands or floor surfaces and cypermethrin on floor surfaces.

Permethrin exposure impacts zebrafish lipid metabolism via the KRAS-PPAR-GLUT signaling pathway, which is mediated by oxidative stress.

Permethrin (Per) is a widely used and frequently detected pyrethroid pesticide in agricultural products and the environment. It may pose potential toxicity to non-target organisms. Per has been reported to affect lipid homeostasis, although the mechanism is undefined. This study aims to explore the characteristic transcriptomic profiles and clarify the underlying signaling pathways of Per-induced lipid metabolism disorder in zebrafish liver. The results showed that environmental exposure to Per caused changes in the liver index, histopathology, and oxidative stress in zebrafish. Moreover, transcriptome results showed that Per heavily altered the pathways involved in metabolism, the immune system, and the endocrine system. We conducted a more in-depth analysis of the genes associated with lipid metabolism. Our findings revealed that exposure to Per led to a disruption in lipid metabolism by activating the KRAS-PPAR-GLUT signaling pathways through oxidative stress. The disruption of lipid homeostasis caused by exposure to Per may also contribute to obesity, hepatitis, and other diseases. The results may provide new insights for the risk of Permethrin to aquatic organisms and new horizons for the pathogenesis of hepatotoxicity.

Reduced effectiveness of permethrin-treated military uniforms after prolonged wear measured by contact irritancy and toxicity bioassays with Ixodes scapularis (Acari: Ixodidae) nymphs.

Factory-treated permethrin uniforms are the primary method used by the US Army to prevent arthropod bites and transmission of arthropod-borne diseases. In this study previously worn uniforms were collected from cadets at the United States Military Academy in West Point, NY to determine the amount of permethrin remaining after prolonged wear and subsequent effects on ticks. Six trousers were collected from cadets in the sophomore, junior, and senior classes. A new, unwashed uniform served as a positive control and an untreated maternity uniform served as a negative control. Fabric samples were removed from each trouser and used in bioassays with laboratory-reared Ixodes scapularis Say nymphs. Contact irritancy bioassays measured the nymphs' ability to remain in contact with fabric for a period of 5 min. Toxicity bioassays measured tick survival at 1 and 24 h after contacting uniform samples. liquid chromatography-mass spectrometry was used to quantify the permethrin content (mg/cm2) in each uniform after the bioassays were complete. The results showed significant amounts of permethrin were lost after extended wear and it was related to the cadet year group. The contact irritancy assays found uniforms with less permethrin did not irritate ticks and cause them to dislodge. Mortality was also affected by permethrin levels, with less ticks dying at 24 h on older uniforms. The results from this study show older uniforms lose most of their permethrin and no longer provide the same levels of protection.

An ultrasensitive solid-state electrochemiluminescence sensor based on Ni-MOF@Ru(bpy)32+ and Au NPs@TiO2 for determination of permethrin.

The novel TiO2 and Ni-MOF materials were synthesized and utilized for the detection of permethrin (PET). A highly sensitive solid-state electrochemiluminescence (ECL) sensor was developed based on Ni-MOF@Ru(bpy)32+ and Au NPs@TiO2. In this sensing platform, Ru(bpy)32+-Tripropyl Amine (TPrA) was used as a luminescent signal, Ni-MOF acted as a carrier to carry more luminescent reagents Ru(bpy)32+. Au NPs acted as promoters facilitated electron transport and TiO2 could further enhance the luminescence intensity of the system by synergistical interaction with Au NPs. The possible mechanisms of signal amplification were investigated. The ECL intensity decreased significantly with increasing PET concentration, enabling the determination of PET amount through the observation of the change in ECL signal intensity (ΔI). Under optimal experimental conditions, the linear range of PET concentration from 1.0 × 10-11 mol L-1 to 1.0 × 10-6 mol L-1, with a detection limit of 3.3 × 10-12 mol L-1 (3S/N). This method was successfully applied to determine PET in various vegetable samples.

Metabolic Resistance and Not Voltage-Gated Sodium Channel Gene Mutation Is Associated with Pyrethroid Resistance of Aedes albopictus (Skuse, 1894) from Cambodia.

(1) Background: In Cambodia, Aedes albopictus is an important vector of the dengue virus. Vector control using insecticides is a major strategy implemented in managing mosquito-borne diseases. Resistance, however, threatens to undermine the use of insecticides. In this study, we present the levels of insecticide resistance of Ae. albopictus in Cambodia and the mechanisms involved. (2) Methods: Two Ae. albopictus populations were collected from the capital, Phnom Penh city, and from rural Pailin province. Adults were tested with diagnostic doses of malathion (0.8%), deltamethrin (0.03%), permethrin (0.25%), and DDT (4%) using WHO tube assays. Synergist assays using piperonyl butoxide (PBO) were implemented before the pyrethroid assays to detect the potential involvement of metabolic resistance mechanisms. Adult female mosquitoes collected from Phnom Penh and Pailin were tested for voltage-gated sodium channel (VGSC) kdr (knockdown resistance) mutations commonly found in Aedes sp.-resistant populations throughout Asia (S989P, V1016G, and F1534C), as well as for other mutations (V410L, L982W, A1007G, I1011M, T1520I, and D1763Y). (3) Results: The two populations showed resistance against all the insecticides tested (<90% mortality). The use of PBO (an inhibitor of P450s) strongly restored the efficacy of deltamethrin and permethrin against the two resistant populations. Sequences of regions of the vgsc gene showed a lack of kdr mutations known to be associated with pyrethroid resistance. However, four novel non-synonymous mutations (L412P/S, C983S, Q1554STOP, and R1718L) and twenty-nine synonymous mutations were detected. It remains to be determined whether these mutations contribute to pyrethroid resistance. (4) Conclusions: Pyrethroid resistance is occurring in two Ae. albopictus populations originating from urban and rural areas of Cambodia. The resistance is likely due to metabolic resistance specifically involving P450s monooxygenases. The levels of resistance against different insecticide classes are a cause for concern in Cambodia. Alternative tools and insecticides for controlling dengue vectors should be used to minimize disease prevalence in the country.

Sub-lethal effects of deltamethrin and permethrin resulted in ultrastructural alterations in scales and oxygen uptake changes of Anabas testudineus (Bloch, 1792).

The present study used scanning electron microscopy (SEM) to assess the toxicity of sub-lethal concentrations of deltamethrin (0.035, 0.007 and 0.0007 mg L-1) and permethrin (0.93, 0.093 and 0.0093 mg L-1) on the ultrastructure of the scales of Anabas testudineus (Bloch, 1792) during a 21 day exposure. The oxygen uptake of the fish during deltamethrin (0.007 and 0.0007 mg L-1) and permethrin (0.093 and 0.0093 mg L-1) exposure was also investigated. The SEM studies revealed abnormal morphological alterations and modifications of fish scales, which were concentration-dependent. Deltamethrin-exposed fish showed severe deformation and fusion of two circuli in different rows, thereby disrupting the normal radii pattern. This fusion was probably caused by the cyanide moiety of the pesticide. On the other hand, permethrin characteristically produced a thick mucus layer over the scale surface. The different concentrations of both the pesticides affected circuli pattern with severe breakage of circuli and loss of lepidonts present over their ridges. Erythrocyte extrusions were also seen at several places over the scale surface. There was significant reduction of oxygen uptake in fish exposed to permethrin at both the concentrations, but in deltamethrin treatments significant reduction occurred only at the higher concentration of 0.007 mg L-1, though this was less than the lower permethrin concentration of 0.0093 mg L-1, and moreover effects of both the pyrethroids on oxygen consumption increased at higher concentrations.

An unusual adverse effect during crusted scabies treatment.

Crusted scabies is a severe form of scabies infestation caused by the ectoparasite Sarcoptes scabiei. Risk factors include immunosuppression, neuropathies, and psychiatric disorders. Its management poses important challenges due to its contagius nature. Here we present a case or Acute Generalized Exanthematous Pustulosis secondary to Ivermectin therapy in a patient with crusted scabies.

GPR39-mediated ERK1/2 signaling reduces permethrin-induced proliferation of estrogen receptor α-negative cells.

Certain insecticides are known to have estrogenic effects by activating estrogen receptors through genomic transcription. This has led researchers to associate specific insecticide use with an increased breast cancer risk. However, it is unclear if estrogen receptor-dependent pathways are the only way in which these compounds induce carcinogenic effects. The objective of this study was to determine the impact of the pyrethroid insecticide permethrin on the growth of estrogen receptor negative breast cancer cells MDA-MB-231. Using tandem mass spectrometric techniques, the effect of permethrin on cellular protein expression was investigated, and gene ontology and pathway function enrichment analyses were performed on the deregulated proteins. Finally, molecular docking simulations of permethrin with the candidate target protein was performed and the functionality of the protein was confirmed through gene knockdown experiments. Our findings demonstrate that exposure to 10-40 µM permethrin for 48 h enhanced cell proliferation and cell cycle progression in MDA-MB-231. We observed deregulated expression in 83 upregulated proteins and 34 downregulated proteins due to permethrin exposure. These deregulated proteins are primarily linked to transmembrane signaling and chemical carcinogenesis. Molecular docking simulations revealed that the overexpressed transmembrane signaling protein, G protein-coupled receptor 39 (GPR39), has the potential to bind to permethrin. Knockdown of GPR39 partially impeded permethrin-induced cellular proliferation and altered the expression of proliferation marker protein PCNA and cell cycle-associated protein cyclin D1 via the ERK1/2 signaling pathway. These findings offer novel evidence for permethrin as an environmental breast cancer risk factor, displaying its potential to impact breast cancer cell proliferation via an estrogen receptor-independent pathway.

A proposal to reduce the amount of permethrin entering wastewater resultant from topical use to treat scabies.

The incidence of scabies is rising in the last years. Subsequently, the use of pharmaceuticals to treat the disease has also increased. Treatment with topical permethrin is usually recommended as a first line agent. This substance is also an aquatic contaminant that is toxic for many non-target organisms, and has been included as a priority substance in the recently published proposal of the European Water Framework Directive. Current guidelines neglect the potential environmental impact of this drug, recommending that the cream should be applied head to toe and "washed off after 8-12 h". Recently, a wiping procedure before hand washing after application of the topical treatment resulted in a 66 % reduction of the amount of diclofenac released in wastewater. The authors suggested that this method could be explored for other topical treatments. In the case of scabiosis, a protocol implicating the whole body needs to be designed. The absorption of topical permethrin is low. Considering the growing incidence of scabies, the amount of the pyrethroid reaching the environment may also be increasing. Therefore, we believe that applying the wiping procedure to the case of topical permethrin deserves consideration. Other measures to minimize the amount of permethrin residues reaching wastewater by washing clothes and bed linen such as wearing single-use pijamas should also be explored. In conclusion, we need to apply a One Health approach in the treatment with scabies, without neglecting the environmental impact of pharmaceuticals. It is not rational to forget drugs once they go down the drain.

In-vivo and in-silico studies to identify toxicity mechanisms of permethrin with the toxicity-reducing role of ginger.

In this study, the toxic effects of permethrin on Allium cepa L. and the protective role of Zingiber officinale rhizome extract (Zoex) were investigated. In this context, 6 different groups were formed. While the control group was treated with tap water, the groups II and III were treated with 10 µg/mL and 20 µg/mL Zoex, respectively, and the group IV was treated with 100 µg/L permethrin. The protective effect of Zoex against permethrin toxicity was studied as a function of dose, and groups V and VI formed for this purpose were treated with 10 µg/mL Zoex + 100 µg/L permethrin and 20 µg/mL Zoex + 100 µg/L permethrin, respectively. After 72 h of germination, cytogenetic, biochemical, physiological, and anatomical changes in meristematic cells of A. cepa were studied. As a result, permethrin application decreased the mitotic index (MI) and increased the frequency of micronuclei (MN), and chromosomal abnormalities. The increase in malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) and the decrease in glutathione (GSH) indicate that permethrin causes oxidative damage. Compared to the control group, a 68.5% decrease in root elongation (p < 0.05) and an 81.8% decrease (p < 0.05) in weight gain were observed in the permethrin-treated group. It was found that the application of Zoex together with permethrin resulted in regression of all detected abnormalities, reduction in the incidence of anatomical damage, MN and chromosomal aberrations, and improvement in MI rates. The most significant improvement was observed in group VI treated with 20 µg/mL Zoex, and Zoex was also found to provide dose-dependent protection. The toxicity mechanism of permethrin was also elucidated by molecular docking and spectral studies. From the data obtained during the study, it was found that permethrin has toxic effects on A. cepa, a non-target organism, while Zoex plays a protective role by reducing these effects.

Differences in excito-repellent behavior between susceptible and permethrin-resistant strains of Aedes aegypti upon exposure to insecticide-treated fabric.

BACKGROUND: An important component of the biological activity of pyrethroids, when used in disease vector control, is excito-repellency. In this study, behavioral differences between insecticide susceptible (Orlando) and pyrethroid resistant (Puerto Rican) strains of Aedes aegypti were explored in a round glass arena using fabrics treated with permethrin, etofenprox, deltamethrin, or DDT. Repellency was evaluated across several variables, including the time to first flight (TFF), number of landings (NOL), total flight time (TFT), and maximum surface contact (MSC), all by video analysis. RESULTS: Results from the Orlando strain indicated they were less likely than the Puerto Rican strain to tolerate tarsal contact with the treated fabrics. All four response variables indicated that the mosquito flight and landing behavior was most affected by pyrethroid resistance [knockdown resistance (kdr)] status. In other experiments, mosquitoes were surgically altered, with antennae ablated bilaterally, and these mosquitoes were more likely to stay on the treated surfaces for longer periods of time, irrespective of any chemical exposure. There were also differences in the responses to antennal ablation between the two strains of mosquitoes, indicating that resistance factors, probably kdr, influence the reactivity of mosquitoes to pyrethroid and DDT treatments, and that it was not completely negated by antennal ablation. CONCLUSIONS: These findings confirm the role of antennal olfactory components in the expression of excito-repellent behaviors, and also support the hypothesis that excito-repellency from pyrethroid/DDT exposure is probably due to a combination of sublethal neurotoxic excitation and interactions with the olfactory system. © 2023 Society of Chemical Industry.