Permethrin Treatments Research Articles

Effects of biochar on ambrosia beetle attacks on redbud and pecan container trees

Abstract Mitigating tree stress can be a valuable strategy to combat ambrosia beetles, such as the granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky; Coleoptera: Curculionidae, Scolytinae) under nursery conditions. Biochar and kaolin clay are known for their stress-relieving properties but their indirect effects on ambrosia beetle in ornamental or pecan (Carya spp.) trees have not been determined. Although entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) and Trichoderma spp. (Hypocreales: Hypocreaceae) have shown effectiveness against adult ambrosia beetles, their role in reducing tree attacks is unclear. Thus, the objective was to determine the effects of biochar, kaolin clay, permethrin (industry standard), and entomopathogenic fungi on reducing ambrosia beetle attacks on young redbud (Cercis canadensis L.; Fabaceae) and pecan trees. The treatments were biochar, kaolin clay, permethrin, biochar + permethrin, kaolin clay + permethrin, B. bassiana, Trichoderma spp., and a nontreated control. Compared to the nontreated trees, biochar and biochar + permethrin treatments significantly reduced ambrosia beetle attacks on redbud trees. Kaolin clay, permethrin, B. bassiana, and Trichoderma spp. did not significantly reduce the number of ambrosia beetle attack holes when compared with the nontreated trees. This suggests that biochar can reduce ambrosia beetle attacks on ornamental trees and should be further evaluated for longer-term effects for multiple seasons.

A push-pull strategy to suppress stable fly (Diptera: Muscidae) attacks on pasture cattle via a coconut oil fatty acid repellent formulation and traps with m-cresol lures.

Stable flies [Stomoxys calcitrans (L.)] are economically important pests of cattle and other livestock. As an alternative to conventional insecticides, we tested a push-pull management strategy using a coconut oil fatty acid repellent formulation and an attractant-added stable fly trap. In our field trials we found that weekly applications of a push-pull strategy can reduce stable fly populations on cattle as well as a standard insecticide (permethrin). We also found that the efficacy periods of the push-pull and permethrin treatments following on-animal application were equivalent. Traps with an attractant lure used as the pull component of the push-pull strategy captured sufficient numbers of stable flies to reduce on-animal numbers by an estimated 17-21%. This is the first proof-of-concept field trial demonstrating the effectiveness of a push-pull strategy using a coconut oil fatty acid-based repellent formulation and traps with an attractant lure to manage stable flies on pasture cattle. Also notable is that the push-pull strategy had an efficacy period equivalent to that of a standard, conventional insecticide under field conditions. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Comparison of sulfur ointment and permethrin treatments in scabies.

Scabies is a contagious, parasitic skin disease that adversely affects the quality of life and, can cause systemic complications if it is not properly treated. Sulfur ointment and permethrin cream are among the most used topical agents in the treatment of scabies. In this study, we aimed to compare the efficacy of sulfur ointment and permethrin cream in the treatment of scabies. In this single-center study, patients who were diagnosed with scabies in the dermatology outpatient clinics of Karabuk University Training and Research Hospital between April, 2021 and September, 2021 were investigated retrospectively. Age, gender, date of diagnosis, topical agent used for scabies treatment, and response to the treatment at the control examination in the second week were recorded. The patients were divided into two groups those receiving 5% permethrin cream or 10% sulfur ointment, and the treatment efficacy of both agents was compared. This study showed that 10% sulfur ointment was significantly more effective in treating scabies than 5% permethrin cream (p< 0.001). Moreover, younger patients with scabies responded better to both treatments. 10% Sulfur ointment can be considered a safe and effective topical option in the treatment of scabies. The resistance to 5% permethrin cream, which is the most commonly used agent for scabies, can be a concern as an unexpected low success rate was obtained in this study.

Insecticide Resistance in Alabama Populations of the Mosquito Aedes albopictus.

The insecticide sensitivity and resistance status of both adults and larvae from six Aedes albopictus samples collected in Tuskegee, Tuscaloosa, Birmingham, Dothan, Mobile, and Montgomery, Alabama, were evaluated for the levels of sensitivity and resistance to eight insecticides: β-cyfluthrin, chlorpyrifos, deltamethrin, etofenprox, fenitrothion, permethrin, resmethrin, and malathion. Adult Ae. albopictus from all locations showed similar results for the difference between the time to 100% mortality and the diagnostic time in the CDC bottle bioassay, although Ae. albopictus survive longer than the diagnostic time to permethrin, fenitrothion, and resmethrin treatments. The larval bioassay indicated that malathion was the least toxic to Ae. albopictus from all locations (LC50: ranging from 0.1 ppm to 1.2 ppm), followed by resmethrin and etofenprox (LC50: 0.05 ppm-0.4 ppm), and deltamethrin and fenitrothion (LC50: 0.01 ppm-0.06 ppm). Chlorpyrifos exhibited the highest larval toxicity (LC50: 0.003 ppm-0.05 ppm). The resistance status of Ae. albopictus from all six locations was similar to the resistance levels found in a previous survey in 2004, indicating that in Alabama the development of resistance is slow in this strain, although comparing the resistance of Ae. albopictus from Tuskegee to that of a susceptible strain showed that it is resistant to chlorpyrifos. The slopes of the dose-response curves to most of the insecticides tested for these field populations of Ae. albopictus were generally similar to or slightly higher than those measured eighteen years previously, indicating that these populations are relatively homozygous in response to all the insecticides tested.

Evaluation of surface versus total permethrin content in permethrin-treated clothing: Implications for protection against mosquitoes

ABSTRACT Permethrin is a synthetic pyrethroid insecticide used to treat uniforms (e.g. military, foresters) and other clothing to protect people against pests (e.g., mosquitoes, ticks). Pests contacting the surface of permethrin-treated clothing (PTC) are repelled and/or killed, depending on the dose and duration of exposure. Hence, it is important to assess the amount of permethrin on the surface of clothing. Fabric swatches prepared using two commercially available permethrin treatments (Insect Shield® & Sawyer Repellant) and one laboratory created treatment (4g permethrin/L) were tested. A Martindale Abrasion and Pilling Tester (MAPT) and gas chromatography were used to assess surface permethrin content (SPC) and total permethrin content (TPC). Sawyer PTC had the highest SPC (mean ± standard error) (32.68±14.55µg/g), followed by Insect Shield® (23.35±2.71µg/g) and lab-created 4g/L permethrin (8.7±0.78µg/g). SPC (after 1000 rubs on MAPT) for Insect Shield®, Sawyer, and 4g/L permethrin groups was significantly lower than TPC (P=0.011, P<0.001, and P=0.001, respectively). The SPC/TPC relationship varied widely between permethrin treatment methods and practical implications for this are discussed. Mosquito repellency tests indicate that Insect Shield®, Sawyer, and lab-created (4g/L) permethrin-treated fabrics showed a significantly higher repellency rate than control (untreated) fabrics (P=0.001, P<0.0001, P<0.0001, respectively). While Insect Shield® had the highest repellency rate against susceptible (53%) and exposed (48%) mosquitoes, differences between groups were not significant. Repellency rates indicate SPC plus other factors (e.g. treatment method) may contribute to mosquito repellency and should be considered in risk assessments for protection against pests.

Assessing efficacies of insect pest management methods to preserve nutritional composition of bagged maize in storehouses located in markets in Nigeria

Maize needs to be stored using effective and safe postharvest management measures to prevent physical insect damage as well as ensure stability of nutritional quality during storage. In this study, conducted in February–December 2016, insect pest management methods for bagged maize preservation in storehouses located in markets in Nigeria were evaluated for their ability to preserve nutritional quality. Study locations were in three grain markets, namely Eleekara market in Oyo town and Arisekola market in Ibadan, Oyo State, South West Nigeria, and Ago market in Ilorin, Kwara State, North Central Nigeria. Treatments comprised Piper guineense(Botanical), Bularafa diatomaceous earth (DE), permethrin powder(Rambo™) (Permethrin), PICSbags(hermetic)and ZeroFly® bags(non-hermetic). The study also had negative control(Control)comprising untreated maize in polypropylene bags. In general, as a result of insect infestation, protein content increased in all treatments except PICS which had the least infestation. After 11 months of storage, Permethrin and PICS treatments had the lowest insect infestation levels and the highest energy levels. Energy level in the Botanical treatment was also high and similar to levels in Permethrin and PICS treatments most likely due to fats and essential oils in P. guineense being adsorbed and/or absorbed by kernels. Fat content was lower in the Control and DE treatments likely due to the Control having the highest insect infestation and the DE adsorbing and/or absorbing fat from kernels. During storage carbohydrate content decreased in all treatments except the Control. However, even in the Control, there was a clear trend of decrease in carbohydrate content. Because the Control had the highest insect (Sitophilus zeamais) infestation and insect damaged kernels (IDK), this trend in decrease in carbohydrate content may be insect related. Ash content increased in the ZeroFly treatment, was unchanged in Botanical, Control, and PICS treatments, and decreased in DE and Permethrin treatments. Nutritional quality variables in this study were within or close to the known value ranges for maize. Therefore, use of maize that had been fumigated well and had a relatively low initial grain MC (9.1%), in addition to the effects of the treatments most likely slowed down population growth of the several insect species that were found and contributed to preserving nutritional quality. The relatively low insect populations in all treatments, including the Control, during the February–September period probably reduced the clarity of effects of infestation on nutritional composition reported in this study.

Functional Analyses of House Fly Carboxylesterases Involved in Insecticide Resistance.

Carboxylesterase-mediated metabolism is one of major mechanisms involved in insecticide resistance. Our previous study has identified multiple carboxylesterase genes with their expression levels were significantly upregulated in pyrethroid resistant house flies. To further explore their metabolic functions, we used insect Spodoptera frugiperda (Sf9) cells to express these carboxylesterases in vitro and measure their hydrolytic activities toward esterase substrates. Our results indicated that these carboxylesterases can efficiently hydrolyze α-naphthyl acetate rather than β- naphthyl acetate. A cell based MTT cytotoxicity assay indicated that carboxylesterase-expressing cells show enhanced tolerance to permethrin, suggesting important roles of these carboxylesterases in metabolizing permethrin and thereby protecting cells from permethrin treatments. The metabolic functions of carboxylesterases were further verified by conducting in vitro metabolism studies toward permethrin and its potential metabolites 3-phenoxybenzyl alcohol and 3-phenoxybenzaldehyde, which not only suggested the potential metabolic pathway of permethrin in insects, but also important roles of these candidate carboxylesterases in metabolizing permethrin and conferring resistance in house flies. Homology modeling and docking were finally conducted to reflect interactions between permethrin ligand and carboxylesterase proteins, visually confirming the metabolic functions of carboxylesterases to insecticides in house flies.

Respiration, predatory behavior and prey consumption by Podisus nigrispinus (Heteroptera: Pentatomidae) nymphs exposed to some insecticides

Podisus nigrispinus Dallas (Heteroptera: Pentatomidae) preys on insect pests in eucalyptus plantations where it can be exposed to insecticides used in pest control. The effect of insecticides on non-target natural enemies requires further study. The objective of the present study was to evaluate the side-effects of Bacillus thuringiensis (Bt), permethrin, tebufenozide and thiamethoxam on third instar nymphs of the predator P. nigrispinus in the laboratory. The toxicity of insecticides for this insect was determined by estimating their lethal concentrations. Podisus nigrispinus behavior after exposure to insecticides was analyzed using a video tracking system and the respiratory rate with a respirometer. Prey/nymph consumption was assessed after 24 h of starvation. The preference of P. nigrispinus nymphs, for prey treated or not with the insecticides, was evaluated in free choice tests. The insecticides Bt [LC50 = 1.10(0.83–1.46) mg mL−1], permethrin [LC50 = 0.25(0.17–0.34) mg mL−1], tebufenozide [LC50 = 5.71(4.17–7.57) mg mL−1] and thiamethoxam [LC50 = 0.04(0.02–0.06) mg mL−1] are toxic to P. nigrispinus nymphs. Bt and the insecticides tebufenozide, permethrin and thiamethoxam reduced the respiratory rate of P. nigrispinus. The insecticides permethrin, tebufenozide and thiamethoxam affect the locomotion of this insect’s nymphs. Prey treated with Bt, permethrin and thiamethoxam are less preferred by P. nigrispinus. The survival of the nymphs of this predator was 93.3%, 66.7%, 56.6%, 0% and 0% in the control, tebufenozide, Bt, permethrin and thiamethoxam treatments, respectively. In addition, the reduction of prey consumption, treated with neurotoxic insecticides, reduces the predatory potential of this natural enemy. Bt and tefubenozide present low toxicity for P. nigrispinus, but the neurotoxic products have low compatibility with this natural enemy and, therefore, are not recommended, with this predator in the management of forest insect pests.

Repellent effects of insecticides on Stephanitis pyrioides Scott (Hemiptera: Tingidae) under laboratory conditions

Stephanitis pyrioides Scott (Hemiptera: Tingidae) is an important insect pest of azalea plants (Rhododendron L. spp.) in the USA. The use of neonicotinoids in landscapes has been reduced because of consumer perceptions that they are not pollinator friendly. The reductions are due mostly to changes in the labels that restrict times these materials can be applied to ornamental plants based on plant phenology and bloom period. Pest management can be improved by using insecticides that repel S. pyrioides. A series of non-contact and contact laboratory assays were conducted with adult S. pyrioides to determine the repellency of insecticides. Insecticides with various modes of action were included in the assays. During the non-contact assay, significantly more S. pyrioides individuals were collected away from the insecticide source than closer to the source when cyfluthrin, bifenthrin, dinotefuran, clothianidin, cyclaniliprole and novaluron were used. During the contact assay, the number of visits was significantly lower for thiamethoxam, lambda-cyhalothrin + bifenthrin + imidacloprid, permethrin, tebufenozide and spinosad treatments than for dinotefuran, azadirachtin, spirotetramat and Chromobacterium subtsugae strain PRAA4-1 T. The adults spent significantly less time on leaves treated with cyfluthrin, permethrin and pyriproxyfen than the other treatments. In a mortality assay performed after 4 h of exposure, significantly more dead adults were found associated with acetamiprid, dinotefuran, thiamethoxam and flupyradifurone compared to chlorantraniliprole, cyantraniliprole, cyclaniliprole, azadirachtin, afidopyropen and flonicamid. After 24 h of exposure, a significantly lower number of fecal spots was observed in the acetamiprid, dinotefuran, thiamethoxam, flupyradifurone, lambda-cyhalothrin, cyantraniliprole, cyclaniliprole, pyrifluquinazon and afidopyropen treatments than chlorantraniliprole and azadirachtin.

Functional Characterization of Carboxylesterases in Insecticide Resistant House Flies, Musca Domestica.

Carboxylesterase-mediated metabolism is thought to play a major role in insecticide resistance in various insects. Several carboxylesterase genes were found up-regulated in the resistant house fly strain, whereas their roles in conferring insecticide resistance remained to be explored. Here, we designed a protocol for the functional characterization of carboxylesterases. Three example experiments are presented: (1) expression and isolation of carboxylesterase proteins through a baculovirus-mediated insect Spodoptera frugiperda (Sf9) cell expression system; (2) a cell-based MTT (3-[4, 5-dimethykthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) cytotoxicity assay to measure the tolerance of insect cells to different permethrin treatments; and (3) in vitro metabolic studies to explore the metabolic capabilities of carboxylesterases toward permethrin. The carboxylesterase gene MdαE7 was cloned from a resistant house fly strain ALHF and used to construct a recombinant baculovirus for Sf9 cells infection. The cell viabilities against different permethrin treatments were measured with the MTT assay. The enhanced cell tolerance of the experimental group (MdαE7-recombinant baculovirus infected cells) compared with those of the control groups (CAT-recombinant baculovirus infected cells and GFP-recombinant baculovirus infected cells) to permethrin treatments suggested the capabilities of MdαE7 in metabolizing insecticides, thereby protecting cells from chemical damages. Besides that, carboxylesterase proteins were expressed in insect Sf9 cells and isolated to conduct an in vitro metabolic study. Our results indicated a significant in vitro metabolic efficiency of MdαE7 toward permethrin, directly indicating the involvement of carboxylesterases in metabolizing insecticides and thus conferring insecticide resistance in house flies.

Carboxylesterase genes in pyrethroid resistant house flies, Musca domestica

Carboxylesterases are one of the major enzyme families involved in the detoxification of pyrethroids. Up-regulation of carboxylesterase genes is thought to be a major component of insecticide resistant mechanisms in insects. Based on the house fly transcriptome and genome database, a total of 39 carboxylesterase genes of different functional clades have been identified in house flies. In this study, eleven of these genes were found to be significantly overexpressed in the resistant ALHF house fly strain compared with susceptible aabys and wild-type CS strains. Eight up-regulated carboxylesterase genes with their expression levels were further induced to a higher level in response to permethrin treatments, indicating that constitutive and inductive overexpression of carboxylesterases are co-responsible for the enhanced detoxification of insecticides. Spatial expression studies revealed these up-regulated genes to be abundantly distributed in fat bodies and genetically mapped on autosome 2 or 3 of house flies, and their expression could be regulated by factors on autosome 1, 2 and 5. Taken together, these results demonstrate that multiple carboxylesterase genes are co-upregulated in resistant house flies, providing further evidence for their involvement in the detoxification of insecticides and development of insecticide resistance.

Head lice treatment with two interventions: Pediculosis capitis profile in female schoolchildren of a rural setting in the south of Iran

Background: Previous research suggests that certain communities, including rural residents, exhibit endemic infestations which can be prevented by banned interventions such as the use of certain chlorinated lice-killing chemicals. The aim of this study was to evaluate two different treatments on head lice among primary school girls of Lar, Fars Province, south of Iran. Patients and Methods: Lindane (1%) or permethrin (1%) shampoos were used on two groups who were treated for live head lice after screening with plastic lice detection combs at schools. A questionnaire form on the epidemiologic factors was included. The outcomes were followed up for 2 weeks from the initial treatment on days 2, 6, 9, and 14. Data analyses were performed using analysis of variance (ANOVA) and Kruskal–Wallis tests. A P value <0.05 was considered to be statistically significant. Results: From 2,084 students examined, 82 girls (3.93%) were infested with pediculosis. No significant correlation was found between head lice infestation level and hair length, hair style, itching, family size, education grade, and age. The data on days 2, 6, 9, and 14 from permethrin and lindane treatments were 71.8%, 64.1%, 89.7%, and 89.7% versus 92.5%, 92.5%, 97.5%, and 95%, respectively. On days 2 (P = 0.017) and 6 (P = 0.002) after treatment, significant differences were noted on reexamination of the cases. Only one reinfestation case was identified during the treatment period. The level of insensitivity to permethrin was twice that of lindane at the end of this period. Conclusion: The level of cure in treated students was similar for both shampoos. Lindane swiftly acted to reduce the level of infested cases by the second day.

Imbalance in redox system of rat liver following permethrin treatment in adolescence and neonatal age

1. The effect of different permethrin treatments on the redox system of rat liver, is presented. Two types of oral administration were chosen: (i) sub-chronic treatment (1/10 of LD50 for 60 days) during adolescence (5 weeks old) and (ii) sub-acute treatment (1/44 of LD50 for 15 days) during early life (from postnatal days 6–21).2. The results show that adolescent permethrin treatment induces damage to the liver redox system, increasing lipid and protein peroxidation and reducing membrane fluidity in the hydrophilic--hydrophobic region of the bilayer. In addition, glutathione peroxidase (GPx) and GSH levels resulted decreased, while glutathione transferase (GST) and catalase (CAT) levels increased.3. The rats treated in early life with permethrin and sacrificed in adult age, showed less signs of damage compared to those exposed during adolescence in which lipid peroxidation was increased by 32%, whereas for the first group the raise was only 11%. Moreover, fluidity improved in the deeper hydrophobic membrane region of the treated group, while the level of CAT was significantly lower compared to the control one.4. Although sub-chronic treatment increased CAT and GST and decreased GPx and GSH levels, the present data suggest that a shorter exposure to permethrin during neonatal age decreased CAT level and it could represent an important risk factor for the onset of long-term liver damage.

Permethrin, a pyrethroid insecticide, potentiates adipogenesis in 3T3‐L1 adipocytes

Permethrin belongs to a family of pyrethroids, naturally occurring insecticides, originating from Chrisanthemum flower heads. It is believed that pyrethroid insecticides have a relatively low toxicity due to limited absorption and fast metabolism, however, the potential link between prolonged exposure to environmental chemicals including pyrethroid insecticides and increased incidence of obesity has been suggested. Thus, the purpose of this study is to determine the effects of permethrin on adipogenesis using 3T3‐L1 adipocyte model. 3T3‐L1 cells were differentiated into adipocytes with 0, 10, and 20 μM permethrin for 6 days. Permethrin treatment at 10 and 20 μM dramatically increased triglyceride deposition compared to control. Expressions of major adipogenic genes, CAATT element binding protein‐α, peroxisome proliferator‐activated receptor‐γ, and fatty acid synthase, and expression of adipose triglyceride lipase were increased by permethrin. However, leptin mRNA expression was not changed by permethrin treatments. These data indicate permethrin could attribute to increased adiposity and potentially impair leptin signaling.

Ovicidal Response of NYDA Formulations on the Human Head Louse (Anoplura: Pediculidae) Using a Hair Tuft Bioassay

Using the in vitro rearing system in conjunction with the hair tuft bioassay, NYDA and NYDA without fragrances formulations (92% wt:wt dimeticones) were 100% ovicidal (0% of treated eggs hatched) after an 8-h exposure of the eggs of the human head louse (Pediculus humanus capitis De Geer) following the manufacturer's instructions. Comparatively, 78 and 66% of eggs similarly exposed hatched after distilled deionized water or Nix (1% permethrin) treatments, respectively. NYDA and NYDA without fragrances formulations were also statistically and substantially more ovicidal than either distilled deionized water or Nix treatments after 10, 30 min, and 1 h exposures. Only the 10 min exposure of eggs to NYDA and NYDA without fragrances formulations resulted in hatched lice that survived to adulthood (5-8% survival). Of the lice that hatched from eggs exposed to NYDA formulations for 10 min, there were no significant differences in the time it took them to become adults, female fecundity or the viability of eggs laid by surviving females. The longevity of adults, however, was reduced after the 10 min treatments of eggs with NYDA and NYDA without fragrances formulations compared with either the distilled deionized water or Nix treatments.

Impacts of permethrin contamination on nematode density and diversity: A microcosm study on benthic meiofauna from a Mediterranean coastal lagoon

A microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg−1), P2: medium (25 mg kg−1) and P3: high (250 mg kg−1)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination.

A microcosm experiment on the effects of permethrin on a free-living nematode assemblage

AbstractMicrocosms were used to assess the impact of permethrin on the abundance and diversity of free-living marine nematodes. The nematodes were exposed to three permethrin concentrations (50, 100 and 150 μg l–1), and the effects were examined after 25 days. The abundances of nematodes at all permethrin concentrations significantly exceeded those in the controls. Multivariate analyses demonstrated that responses of nematode species to permethrin treatments were varied: Pselionema sp., Prochromadorella neapolitana and Spirinia gerlachi were eliminated at the low dose and seemed to be species intolerant to permethrin; Trichotheristus mirabilis and Xyala striata, which increased with increasing contamination levels, seemed to be 'opportunistic' and/or 'resistant' species. Results showed significant differences between univariate measures of diversity of control nematodes and those from permethrin- contaminated microcosms, where all decreased significantly with increasing abundance of the most tolerant species to permethrin. The use of microcosms has allowed the effects of permethrin on nematodes to be assessed individually, which is not possible in the field.

Erythrocyte antioxidants enzymes imbalance following subcutaneous pyrethroid treatments in rats of different sex

Permethrin and deltamethrin are insecticides used all over the world in agriculture to control pests. The aim of this work is to investigate the effects of subcutaneous permethrin and/or deltamethrin treatments on erythrocyte antioxidant enzymes activity in rats of different sex. The results obtained show that permethrin decreases SOD and GPx activity in female rats, while it increases SOD activity in male rats. Deltamethrin treatment reduces GPx activity in male rats, while permethrin has a similar effect but only for short time treatments. A catalase activity decrease was observed in both sexes following pyrethroid treatment but when both the pyrethroids were administrated in male rats, the enzyme activity has increased. In conclusion, this study points out for the first time the importance of rat gender on erythrocyte antioxidant enzymes, which are influenced not only by the length and the type of insecticide treatment but importantly by sex.

Treatment of timber with permethrin in supercritical carbon dioxide to control termites

The solubility of permethrin in supercritical carbon dioxide (scCO 2) was determined, with optimal solubility for the timber impregnation trial and the specific operating conditions examined occurring at 50 °C. Methanol as co-solvent improved solubility, but was not needed for timber impregnation. Eucalyptus obliqua heartwood (a refractory timber), Pinus radiata sapwood and P. radiata LVL were impregnated in a treatment cylinder, and their resistance to attack by termites was compared to that of material protected with standard permethrin treatments using light organic solvent preservative (LOSP). Termite field tests were conducted against Coptotermes acinaciformis and Mastotermes darwiniensis. The choice of solvent system did not affect permethrin efficacy in P. radiata sapwood against termites. P. radiata LVL specimens treated using scCO 2 had slightly lower mean mass losses than those impregnated with LOSP, reflecting slightly higher permethrin uptakes in the former. E. obliqua heartwood was completely destroyed by M. darwiniensis when impregnated with LOSP, but was mostly sound when scCO 2 was used. These results show that scCO 2 did not alter the effectiveness of the insecticide, while giving the added benefit of allowing the impregnation of timbers previously considered refractory to treatment.

Neurotoxicity in murine striatal dopaminergic pathways following long-term application of low doses of permethrin and MPTP

The long-term effects of permethrin (PM) and its interaction with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on striatal dopaminergic pathways were investigated in C57BL/6 mice. In a 3-month exposure, technical PM (1.5 mg/kg) was administered once per week, with MPTP (20 mg/kg) given once on either the 7th week or 11th week. In a 6-month exposure, PM (0.8 mg/kg or 1.5 mg/kg) was administered once per week for 26 weeks, with MPTP (20 mg/kg) given once, on week 24. Alterations in the expression of tyrosine hydroxylase (TH), dopamine transporter (DAT), and α-synuclein proteins were analyzed 1 day after the last PM treatment using western blot assay. PM had no significant effect on striatal dopaminergic pathways by itself, whereas MPTP significantly reduced the expression of TH and DAT proteins. In both exposure paradigms, weekly 1.5 mg/kg PM treatments antagonized the toxic effect of MPTP on TH and DAT expression ( p < 0.05). There was no significant alteration of α-synuclein expression following any exposure to PM and/or MPTP. [ 3H]Tetrabenazine (TBZ) binding assay for expression of striatal vesicular monoamine transporter (VMAT) showed no effect of PM, but the reduction in this protein caused by MPTP was attenuated by PM, consistent with effects on other dopaminergic biomarkers. The overall findings demonstrate that long-term, low-dose exposure to PM alone did not cause signs of neurotoxicity to striatal dopaminergic neural terminals, or enhance the effects of MPTP. We conclude that under typical use conditions, PM poses little Parkinsonian hazard to humans, including when impregnated into clothing for control of biting flies.