Acute toxicity and teratogenicity of carbaryl (carbamates), tebufenpyrad (pyrazoles), cypermethrin and permethrin (pyrethroids) on the European sea bass (Dicentrarchus labrax L, 1758) early life stages

The toxicity of carbaryl, tebufenpyrad, cypermethrin and permethrin was evaluated in European sea bass Dicentrarchus labrax during the embryonic and larval development using six different concentrations per chemical. The order of the toxicity effectiveness was carbaryl > tebufenpyrad > cypermethrin > permethrin. The larvae were more sensitive to all tested chemicals than embryos. The LC50 of carbaryl, tebufenpyrad, cypermethrin and permethrin was determined as 13.88, 43.96, 92 and 142 ppm and 9.27, 25.67, 48.4 and 72.7 ppm in embryo and larvae, respectively. Furthermore, the tested pesticides exhibited teratogenic effects on D. labrax embryo-larval stages. The observed malformations were coagulation, no spherical egg, unhatched egg, pericardial oedemata, yolk oedemata, lordosis, kyphosis, scoliosis, no eye, cranial deformation and body atrophy. Malformations were induced with 0.5 ppm carbaryl, 10 ppm tebufenpyrad and 50 ppm cypermethrin and permethrin; the highest rates of malformation were noted with 16 ppm carbaryl, 160 ppm tebufenpyrad, 400 ppm cypermethrin and 400 ppm permethrin as 34.5%, 28%, 17.5% and 16%, respectively. A positive correlation between the incidence of malformation and the increase of pesticide concentration was established.

Advances and future prospects of pyrethroids: Toxicity and microbial degradation

Pyrethroids are a class of insecticides structurally similar to that of natural pyrethrins. The application of pyrethrins in agriculture and pest control lead to many kinds of environmental pollution affecting human health and loss of soil microbial population that affect soil fertility and health. Natural pyrethrins have been used since ancient times as insect repellers, and their synthetic versions especially type 2 pyrethroids could be highly toxic to humans. PBO (Piperonyl butoxide) is known to enhance the toxicity of prallethrin in humans due to the resistance in its metabolic degradation. Pyrethroids are also known to cause plasma biochemical profile changes in humans and they also lead to the production of high levels of reactive oxygen species. Further they are also known to increase SGPT activity in humans. Due to the toxicity of pyrethrins in water bodies, soils, and food products, there is an urgent need to develop sustainable approaches to reduce their levels in the respective fields, which are eco-friendly, economically viable, and socially acceptable for on-site remediation. Keeping this in view, an attempt has been made to analyse the advances and prospects in using pyrethrins and possible technologies to control their harmful effects. The pyrethroid types, composition and biochemistry of necessary pyrethroid insecticides have been discussed in detail, in the research paper, along with their effect on insects and humans. It also covers the impact of pyrethroids on different plants and soil microbial flora. The second part deals with the microbial degradation of the pyrethroids through different modes, i.e., bioaugmentation and biostimulation. Many microbes such as Acremonium, Aspergillus, Microsphaeropsis, Westerdykella, Pseudomonas, Staphylococcus have been used in the individual form for the degradation of pyrethroids, while some of them such as Bacillus are even used in the form of consortia.

Effects of temperature and salinity on bioconcentration and toxicokinetics of permethrin in pyrethroid-resistant Hyalella azteca

Recent studies demonstrated pyrethroid resistance associated with voltage-gated sodium channel mutations in populations of the epibenthic amphipod, Hyalella azteca. Resistant populations were able to tolerate and bioconcentrate pyrethroids at concentrations significantly higher than toxic levels for non-resistant populations. In conjunction with elevated bioconcentration potential, environmental alteration particularly as a result of global climate change is anticipated to significantly alter abiotic parameters including temperature and salinity. These changes are expected to influence uptake and biotransformation of contaminants. Thus, the aims of the current study were a) to examine the bioconcentration potential of permethrin in two pyrethroid-resistant clades of H. azteca and b) assess the influence of temperature and salinity changes on toxicokinetic parameters. Two pyrethroid-resistant clades of H. azteca were exposed to ¹⁴C-permethrin at three salinities (0.2, 1.0 and 6.0 practical salinity units (PSU)) and temperatures (18, 23 and 28 °C). Tests were conducted for up to 36 h and uptake, elimination and biotransformation rates were calculated. Both populations demonstrated bioconcentration factors (BCFs) between five and seven times greater than published data for non-resistant H. azteca, with significant differences between clades. Calculated BCF values were comparable to field populations of resistant H. azteca, emphasizing the potential for elevated pyrethroid bioconcentration in the natural environment and increased exposure for predators consuming pyrethroid-resistant aquatic invertebrates. Alterations to temperature and salinity had no statistically significant effect on uptake or parent compound half-life in either population, though biotransformation was elevated at higher temperatures in both populations. Salinity had a variable effect between the two populations, with lower BCF values at 1.0 PSU in clade D H. azteca and greater BCFs at 6.0 PSU in clade C H. azteca. This is the first study to demonstrate the potential for future climate scenarios to influence toxicokinetics in pyrethroid-resistant aquatic organisms.

Multiple insecticide resistance mechanisms in urban population of Anopheles coluzzii (Diptera: culicidae) from Lagos, South-West Nigeria

Malaria is a major public health challenge in Africa with Nigeria accounting for the highest burden of the disease in the world. Vector control has proved to be a highly effective component of malaria control, however, the development and spread of insecticide resistance in major vectors of malaria have been a major challenge. This study assessed resistance mechanisms in Anopheles coluzzii populations from Kosofe, Lagos mainland and Ojo Local Government Areas in Lagos, Nigeria where An. gambiae s.l is resistant to DDT and Permethrin. WHO susceptibility bioassay test was used in determining resistance status of An. coluzzii to discriminating doses of DDT and Permethrin while synergist assay was used to assess the involvement of monooxygenases in resistance development. Sub-species of An. gambiae s.l (An. gambiae and An. coluzzii) were identified using polymerase chain reaction (PCR) and Restriction Fragment Length Polymorphism (PCR-RFLP) while Allele-Specific Polymerase Chain Reaction (AS-PCR) assay was used to detect knockdown mutation (kdr-West; L1014F). Biochemical assays were used in determining the activities of metabolic enzymes. High DDT resistance was recorded in An. coluzzii populations from the three sites. Mortality rate of mosquitoes exposed confirmed Permethrin resistance in Kosofe (50%) and Lagos mainland (48%) but resistance was suspected in Ojo (96%). All specimens tested were confirmed as An. coluzzii with low kdr frequency; 11.6%, 16.4% and 6.7% in Kosofe, Lagos mainland and Ojo respectively. Pre-exposure to synergist (PBO) before exposure to Permethrin led to increased mortality in all populations. Esterase activity was insignificantly overexpressed in Kosofe (p = 0.849) and Lagos mainland (p = 0.229) populations. In contrast, GST activity was significantly lower in populations from Lagos mainland (63.650 ± 9.861; p = 0.007) and Ojo (91.765 ± 4.959; p = 0.042) than Kisumu susceptible strains (120.250 ± 13.972). Monooxygenase activity was higher in Lagos mainland (2.371 ± 0.261) and Ojo (1.361 ± 0.067) populations, albeit significantly in Lagos mainland (p = 0.007) only. Presence of target-site mutation in all populations, increased mortality with pre-exposure to PBO and elevated monooxygenase in Lagos mainland population were confirmed. Multiple resistance mechanisms in some urban populations of An. coluzzii from Lagos, Nigeria calls for appropriate resistance management strategies.

Permethrin-treated baby wraps for the prevention of malaria: results of a randomized controlled pilot study in rural Uganda

Background

Progress against malaria has stalled and may even be slipping backwards in high-burden countries. This is due to a range of factors including insecticide resistance and mosquito feeding behaviours that limit contact with widely-employed interventions including long-lasting insecticidal nets and indoor-residual spraying. Thus, further innovations in malaria control are urgently needed.

Methods

The pilot was a randomized, placebo-controlled pilot study of permethrin-treated baby wraps—known locally as lesus—in children 6–18 months of age at a single site in rural western Uganda. Fifty mother–infant pairs were assigned to permethrin-treated or untreated lesus in a 1:1 allocation. Participants and clinical staff were blinded to group assignments through use of sham treatment and re-treatment of lesus. Participants attended scheduled clinic visits every 2 weeks for a total 12 weeks. The primary outcome of interest was the safety of the intervention, assessed as changes in the frequency of use, rates of discontinuation, and incidence of adverse events, such as skin rash. Secondary outcomes included acceptability and feasibility of the intervention as measured through participant satisfaction and completion of study activities, respectively.

Results

Overall, rates of retention and participation were relatively high with 86.0% (43 of 50) of participants completing all scheduled visits, including 18 (75.0%) and 25 (96.2%) in the intervention and control arms respectively. By the conclusion of the 12-week follow-up period, one adverse event (0.35 events per 100 person-weeks, one-sided 95% CI 0.0–1.65) was reported. Satisfaction with the lesu was high in both groups. In each study arm, there were five incident RDT positive results, but the only PCR-positive results were observed in the control group (n = 2).

Conclusions

Permethrin-treated baby wraps were well-tolerated and broadly acceptable. Adverse events were infrequent and mild. These findings support future trials seeking to determine the efficacy of treated wraps to prevent P. falciparum malaria infection in young children as a complementary tool to existing household-based interventions.

Trial registration: ClinicalTrials.gov Identifier: NCT04102592, Registered 25 September 2019. Available at: https://clinicaltrials.gov/ct2/show/NCT04102592

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04086-w.

Bioefficacy and durability of Olyset® Plus, a permethrin and piperonyl butoxide-treated insecticidal net in a 3-year long trial in Kenya

BACKGROUND

Long-lasting insecticide nets (LLINs) are a core malaria intervention. LLINs should retain efficacy against mosquito vectors for a minimum of three years. Efficacy and durability of Olyset^® Plus, a permethrin and piperonyl butoxide (PBO) treated LLIN, was evaluated versus permethrin treated Olyset^® Net. In the absence of WHO guidelines of how to evaluate PBO nets, and considering the manufacturer's product claim, Olyset^® Plus was evaluated as a pyrethroid LLIN.

METHODS

This was a household randomized controlled trial in a malaria endemic rice cultivation zone of Kirinyaga County, Kenya between 2014 and 2017. Cone bioassays and tunnel tests were done against Anopheles gambiae Kisumu. The chemical content, fabric integrity and LLIN survivorship were monitored. Comparisons between nets were tested for significance using the Chi-square test. Exact binomial distribution with 95% confidence intervals (95% CI) was used for percentages. The WHO efficacy criteria used were ≥ 95% knockdown and/or ≥ 80% mortality rate in cone bioassays and ≥ 80% mortality and/or ≥ 90% blood-feeding inhibition in tunnel tests.

RESULTS

At 36 months, Olyset^® Plus lost 52% permethrin and 87% PBO content; Olyset^® Net lost 24% permethrin. Over 80% of Olyset^® Plus and Olyset^® Net passed the WHO efficacy criteria for LLINs up to 18 and 12 months, respectively. At month 36, 91.2% Olyset^® Plus and 86.4% Olyset^® Net survived, while 72% and 63% developed at least one hole. The proportionate Hole Index (pHI) values representing nets in good, serviceable and torn condition were 49.6%, 27.1% and 23.2%, respectively for Olyset^® Plus, and 44.9%, 32.8% and 22.2%, respectively for Olyset^® Net but were not significantly different.

CONCLUSIONS

Olyset^® Plus retained efficacy above or close to the WHO efficacy criteria for about 2 years than Olyset^® Net (1-1.5 years). Both nets did not meet the 3-year WHO efficacy criteria, and showed little attrition, comparable physical durability and survivorship, with 50% of Olyset^® Plus having good and serviceable condition after 3 years. Better community education on appropriate use and upkeep of LLINs is essential to ensure effectiveness of LLIN based malaria interventions.

Evaluation of anti-lice topical lotion of ozonated olive oil and comparison of its effect with permethrin shampoo

BACKGROUND

Pediculosis is an infestation of lice affecting mostly children and spreads by direct contact with the hair of someone infected. Although topical application of a pediculicide such as permethrin shampoo is the most common cure for head lice, the addition of alternative treatments is necessary due to permethrin resistance and some safety concerns, including irritation, burning sensation, tingling, and breathing problems. Recent studies have indicated that ozone, which is an allotropic form of oxygen, may have anti-pediculosis effects.

OBJECTIVE

This study focused on the evaluation of an ozonated olive oil topical lotion for the treatment of pediculosis and the comparison of its effects with permethrin shampoo.

METHODS

121 patients with proven head pediculosis were divided into two groups. They were treated with either topical ozonated olive oil lotion or permethrin shampoo for one week.

RESULTS

It was shown that the ozonation process enormously improved the physico-chemical properties of olive oil. Specifically, acid and peroxide values increased 60 fold and 200 fold, respectively, while there was a sharp decline for the iodine index (81.8±1.28 to 0 g iodine per 100 g). Additionally, all patients who received the ozonated olive oil lotion were entirely cured after one week of treatment, while those who were treated with permethrin, required to receive more. Statistical analysis of the data also proved this claim.

CONCLUSION

The prepared lotion has shown significant effects in controlling head lice. Thus, it can be prescribed as an effective anti-pediculosis medicine which is biocompatible and has high potential.

Effect of interventions to reduce malaria incidence among military personnel on active duty: study protocol for a cluster randomised controlled trial of the impact of etofenprox-treated uniforms, permethrin-treated uniforms and DEET insect repellent

BACKGROUND

While there is strong evidence that bite protection methods such as permethrin-treated clothing and topical insect repellents are protective against insect bites, there are few studies assessing the impact on malaria infection. This study will estimate the protective efficacy of treated uniforms and DEET insect repellent on the incidence of malaria infection among military personnel in an operational setting. Permethrin-treated uniforms used with DEET lotion will be compared to etofenprox-treated uniforms with DEET lotion. The effect of DEET lotion will be estimated by comparing permethrin-treated uniforms with DEET or placebo lotion.

METHOD

A cluster randomised double-blind placebo-controlled trial is planned to evaluate the effectiveness of the interventions on preventing malaria infections in soldiers on active duty at Mgambo National Service Camp in Tanga, Tanzania. The arms are (1) permethrin-treated uniform with 30% DEET liposome formula; (2) permethrin-treated uniform with placebo lotion; (3) candidate insect repellent system, i.e. etofenprox-treated uniform with 30% DEET liposome formula; and (4) placebo, i.e. untreated uniforms with placebo lotion. The primary outcome is the incidence of Plasmodium falciparum malaria infection detected by polymerase chain reaction (PCR) by active case detection using surveys every 2 weeks for 12 months. Rapid diagnostic tests will be used for the diagnosis of participants with symptoms. The unit of randomisation will be combania: companies formed by recruits aged 18 to 25 years; combania do activities together and sleep in the same dormitory. Unequal randomisation will be used to optimise statistical power for the primary comparison between permethrin-treated uniforms with DEET and etofenprox-treated uniforms with DEET.

DISCUSSION

This trial will provide the estimate of the effects of permethrin with DEET compared to those of the new fabric treatment etofenprox with DEET and any additional effect of using DEET. The results will inform strategies to protect military personnel and civilians who have more outdoor or occupational malaria exposure than the general public.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02938975 .

Enhanced pyrethroid potency in Drosophila melanogaster expressing voltage-gated potassium channel mutants: Insecticidal activity and neuronal action

Previous studies have shown that blockers of voltage-gated potassium (Kv) channels, such as 4-aminopyridine (4-AP) and 2-methoxy-N-((1-phenylcyclopentyl)methyl)benzamide (2-MPB) synergized pyrethroid toxicity as well, or better than, piperonyl butoxide. The present study assessed the involvement of different Kv channels as possible pyrethroid synergist targets in Drosophila melanogaster. Three Kv1 mutants (Sh⁵, Sh¹³³, and Sh^M) and one Kv2 mutant (Shab³) were tested. All Kv1 mutant flies showed increased sensitivity to permethrin in topical and glass contact toxicity assays, of 2- to 11-fold. Central nervous system (CNS) recordings of larval D. melanogaster showed a similar pattern of increased sensitivity. Potentiated effects were also observed with deltamethrin on the mutants Sh⁵ (30- to 35-fold) and Sh¹³³ (33- to 47-fold), but the mutant Sh^M showed little change in sensitivity. In contrast, the Shab³ strain showed toxicity and physiological effects of both pyrethroids that were similar to the susceptible OR strain. Thus, some K⁺ channel mutations mimicked the synergistic effect of channel blockers. Additional studies showed that Shab³ had the highest sensitivity to 4-AP in topical assays, and the Shaker-null mutants, Sh^M and Sh¹³³ showed greater sensitivity to 2-MPB in CNS recordings of larval D. melanogaster. These results suggest that Kv1 channels are a useful synergist target for pyrethroids, as assessed both in whole insects and at the level of the nervous system. Thus, Kv1-targeting compounds can potentially serve as insect control tools to reduce pyrethroid use via synergistic action.

How does sublethal permethrin effect non-target aquatic organisms?

Permethrin is belonged to pyrethroids that are one of the substances developed as an alternative to pesticides. Permethrin, which is used especially in agriculture, can bioaccumulate in the water and sediment when mixed into aquatic ecosystems. For this reason, it is necessary to investigate the effect of this substance on aquatic organisms other than the target organism. The aim of this study was the determination of acute and sublethal effects as antioxidant enzyme levels on different organs and hemolymph biochemistry of the non-target aquatic organism, narrow-clawed crayfish (Astacus leptodactylus), after exposure to permethrin, one of the synthetic pyrethroid pesticides, contaminating aquatic ecosystems due to its increase usage. The invertebrate model organism, the narrow-clawed crayfish, was selected for its bioindicator role in food webs as planktivorous grazers epibenthic scavengers and good alternative models in ecotoxicology studies with the importance in conservation of freshwater ecosystems. The 96-h LC₅₀ value of permethrin to experimental species was estimated as 0.903 μg/L (95% CI = 0.5042-2.2734 μg/L) with probit analysis method. The sublethal concentration of the permethrin was determined by 1/10 of 96-h LC₅₀ values as 0.09 μg/L. There were two control (negative and acetone) groups in the experiment. The sampling of hemolymph and the tissues (gills, hepatopancreas, and muscle) were done 48 h and 96 h after exposure of the permethrin. The total hemocyte counts significantly increased in the 96-h exposed group of permethrin (p<0.05). Among the hemolymph biochemical parameters, the hemolymph potassium and chloride values increased statistically (p<0.05). Malondialdehyde levels (MDA) of gills and muscle were significantly increased, whereas the MDA level of the hepatopancreas was significantly decreased at the end of the experiment (p<0.05). Hyperplasia in the lamella was recorded in gills, while the degenerations of the hepatopancreas tissues were observed. According to obtained results, permethrin was extremely toxic as acutely to narrow-clawed crayfish and also effected at sublethal concentrations.

Exposure to permethrin used as a home insecticide: A case study comparing model predictions and excretion of metabolites

Pyrethroids have been widely used as an active ingredient in home insecticide products since the 1960 s. Although their occurrence in indoor environments has been studied, the contribution of home insecticide application to the aggregate exposure to pyrethroids is not well known. The objective of this study was to estimate the consumer exposure to permethrin, a representative pyrethroid, via the use of home insecticide spray during the summer season using biomonitoring and personal exposure modeling. Exposure to permethrin was assessed by analyzing its urinary metabolites, 3-phenoxybenzoic acid (3-PBA) and cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropan carboxylic acid (cis/trans-DCCA), for a group of consumers (n = 27). The levels of metabolites were also compared with those predicted by a screening exposure model considering personal exposure parameters. The levels of metabolites in 15 participants increased significantly (p < 0.05) with the application of home insecticide products, thereby suggesting that the heavy use of home insecticides during summer could be an important exposure route of permethrin in addition to other sources, such as food consumption. The total amount of excreted 3-PBA and cis/trans-DCCA was lower than the amount estimated by the exposure model for most participants by a factor of 0.9-861.0. These differences could be attributed to the rapid loss of permethrin after application, including sorption to indoor surfaces, reaction with indoor substances, individual biological variations, and ventilation during application. However, the screening exposure model used for the initial safety assessment of biocidal products generally performed well because it did not underestimate the personal exposure to permethrin during the application of home insecticide spray.

High-fat diet-induced aggravation of cardiovascular impairment in permethrin-treated Wistar rats

This study characterized the impact of post-weaning high-fat diet (HFD) and/or permethrin (PER) treatment on heart dysfunction and fibrosis, as well as atherogenic risk, in rats by investigating interactions between HFD and PER. Our results revealed that HFD and/or PER induced remarkable cardiotoxicity by promoting cardiac injury, biomarker leakage into the plasma and altering heart rate and electrocardiogram pattern, as well as plasma ion levels. HFD and/or PER increased plasma total cholesterol, triacylglycerols, and low-density lipoprotein (LDL) cholesterol levels but significantly reduced high-density lipoprotein (HDL) cholesterol. Cardiac content of peroxidation malonaldehyde, protein carbonyls, and reactive oxygen species were remarkably elevated, while glutathione levels and superoxide dismutase, catalase and glutathione peroxidase activities were inhibited in animals receiving a HFD and/or PER. Furthermore, cardiac DNA fragmentation and upregulation of Bax and caspase-3 gene expression supported the ability of HFD and/or PER to induce apoptosis and inflammation in rat hearts. High cardiac TGF-β1 expression explained the profibrotic effects of PER either with the standard diet or HFD. Masson's Trichrome staining clearly demonstrated that HFD and PER could cause cardiac fibrosis. Additionally, increased oxidized LDL and the presence of several lipid droplets in arterial tissues highlighted the atherogenic effects of HFD and/or PER in rats. Such PER-induced cardiac and vascular dysfunctions were aggravated by and associated with a HFD, implying that obese individuals may be more vulnerable to PER exposure. Collectively, post-weaning exposure to HFD and/or PER may promote heart failure and fibrosis, demonstrating the pleiotropic effects of exposure to environmental factors early in life.

Evaluation of Efficiency of Ivermectin Lotion in Comparison with Permethrin Shampoo and Dimethicone Lotion for Treatment of Head Lice (Pediculus humanus capitis) in Areas Covered by Health Centers of Islamshahr City, Tehran, Iran in 2019

Background

Head lice infestation is known as a serious health problem in developing and developed countries. The prevalence of pediculosis in children and females is higher than others. The infestation may cause the absence of student from school and make their parents upset. The aim of current study was to evaluate the WHO recommended insecticides for control of head lice in Islamshahr health center.

Methods

In the current study infested individuals were older than 6 years old and have been diagnosed with at least 3 head lice adult and 10 live nits from less than 0.7 cm scalp. The pediculicides was applied randomly among groups. Permethrin shampoo as a golden standard was used. Dimethicone lotion 4% and Ivermectin lotion was compared with it. This study was conducted on 179 infested people. Results of infestation were evaluated after one month of intervention. Different indicators such as: present of head lice adult or live nit, redness and irritation in head skin were invested.

Results

All the participants were female and 72.6% of them were in the age group of 6-11. The result revealed that aging not only decreases the infection rate but also raised the recovery percentage. The results showed that 79.5% permethrin receiver, 83% of people who treated with Dimethicone lotion and 90.6% of Ivermectin receiver had no head lice. There was no significant difference among these three pediculicides.

Conclusion

There was no significant difference among tested pediculicides. An appropriate pediculicide can be selected by training people.

Efficacy of a single administration of afoxolaner (NexGard®) or fipronil plus permethrin (Frontline® Tri-Act) against Hyalomma marginatum ticks in dogs

This study was conducted to assess the acaricidal efficacy of afoxolaner (NexGard®, Boehringer Ingelheim), and fipronil - permethrin (Frontline® Tri-Act, Boehringer Ingelheim) administered once to dogs experimentally infested with Hyalomma marginatum ticks. Twenty-four Beagle dogs were randomly allocated based on a pre-treatment H. marginatum infestation to an untreated control group, a NexGard® or a Frontline® Tri-Act treated groups. Treatments were administered once on Day 0 as per the products' labels. For the efficacy evaluation, dogs were experimentally infested with 30 adult H. marginatum ticks on Days -2, 7, 28 and 36. In-situ counts were performed at 48 h post-treatment on Day 2 and post-infestations on Days 9, 30 and 38. Ticks were removed and counted at 72 h post-treatment on Day 3 and after each tick infestation on Days 10, 31 and 39. The numbers of live ticks counted in the treated groups were significantly different than in the control group at all time-points (p ≤ 0.0006). The efficacy was at least 97% after 48 h, and at least 99% after 72 h for both treatments. In this study both afoxolaner and fipronil/permethrin formulations demonstrated a high efficacy against adult H. marginatum ticks in treated dogs for at least five weeks.

Delayed treatment with the immunotherapeutic LNFPIII ameliorates multiple neurological deficits in a pesticide-nerve agent prophylactic mouse model of Gulf War Illness

Residual effects of the 1990-1991 Gulf War (GW) still plague veterans 30 years later as Gulf War Illness (GWI). Thought to stem mostly from deployment-related chemical overexposures, GWI is a disease with multiple neurological symptoms with likely immunological underpinnings. Currently, GWI remains untreatable, and the long-term neurological disease manifestation is not characterized fully. The present study sought to expand and evaluate the long-term implications of prior GW chemicals exposure on neurological function 6-8 months post GWI-like symptomatology induction. Additionally, the beneficial effects of delayed treatment with the glycan immunotherapeutic lacto-N-fucopentaose III (LNFPIII) were evaluated. Male C57BL/6J mice underwent a 10-day combinational exposure (i.p.) to GW chemicals, the nerve agent prophylactic pyridostigmine bromide (PB) and the insecticide permethrin (PM; 0.7 and 200 mg/kg, respectively). Beginning 4 months after PB/PM exposure, a subset of the mice were treated twice a week until study completion with LNFPIII. Evaluation of cognition/memory, motor function, and mood was performed beginning 1 month after LNFPIII treatment initiation. Prior exposure to PB/PM produced multiple locomotor, neuromuscular, and sensorimotor deficits across several motor tests. Subtle anxiety-like behavior was also present in PB/PM mice in mood tests. Further, PB/PM-exposed mice learned at a slower rate, mostly during early phases of the learning and memory tests employed. LNFPIII treatment restored or improved many of these behaviors, particularly in motor and cognition/memory domains. Electrophysiology data collected from hippocampal slices 8 months post PB/PM exposure revealed modest aberrations in basal synaptic transmission and long-term potentiation in the dorsal or ventral hippocampus that were improved by LNFPIII treatment. Immunohistochemical analysis of tyrosine hydroxylase (TH), a dopaminergic marker, did not detect major PB/PM effects along the nigrostriatal pathway, but LNFPIII increased striatal TH. Additionally, neuroinflammatory cells were increased in PB/PM mice, an effect reduced by LNFPIII. Collectively, long-term neurobehavioral and neurobiological dysfunction associated with prior PB/PM exposure was characterized; delayed LNFPIII treatment provided multiple behavioral and biological beneficial effects in the context of GWI, highlighting its potential as a GWI therapeutic.

Dysregulation of cellular energetics in Gulf War Illness

Gulf War Illness (GWI) is estimated to have affected about one third of the Veterans who participated in the first Persian Gulf War. The symptoms of GWI include chronic neurologic impairments, chronic fatigue syndrome, as well as fibromyalgia and immune system disorders, collectively referred to as chronic multi-symptom illness. Thirty years after the war, we still do not have an effective treatment for GWI. It is necessary to understand the molecular basis of the symptoms of GWI in order to develop appropriate therapeutic strategies. Cellular energetics are critical to the maintenance of cellular homeostasis, a process that is highly dependent on intact mitochondrial function and there is significant evidence from both human studies and animal models that mitochondrial impairments may lead to GWI symptoms. The available clinical and pre-clinical data suggest that agents that improve mitochondrial function have the potential to restore cellular energetics and treat GWI. To date, the experiments conducted in animal models of GWI have mainly focused on neurobehavioral aspects of the illness. Additional studies to address the fundamental biological processes that trigger the dysregulation of cellular energetics in GWI are warranted to better understand the underlying pathology and to develop new treatment methods. This review highlights studies related to mitochondrial dysfunction observed in both GW veterans and in animal models of GWI.

Voltage-sensitive sodium channel (Vssc) mutations associated with pyrethroid insecticide resistance in Aedes aegypti (L.) from two districts of Jeddah, Kingdom of Saudi Arabia: baseline information for a Wolbachia release program

Background

Dengue suppression often relies on control of the mosquito vector, Aedes aegypti, through applications of insecticides of which the pyrethroid group has played a dominant role. Insecticide resistance is prevalent in Ae. aegypti around the world, and the resulting reduction of insecticide efficacy is likely to exacerbate the impact of dengue. Dengue has been a public health problem in Saudi Arabia, particularly in Jeddah, since its discovery there in the 1990s, and insecticide use for vector control is widespread throughout the city. An alternative approach to insecticide use, based on blocking dengue transmission in mosquitoes by the endosymbiont Wolbachia, is being trialed in Jeddah following the success of this approach in Australia and Malaysia. Knowledge of insecticide resistance status of mosquito populations in Jeddah is a prerequisite for establishing a Wolbachia-based dengue control program as releases of Wolbachia mosquitoes succeed when resistance status of the release population is similar to that of the wild population.

Methods

WHO resistance bioassays of mosquitoes with deltamethrin, permethrin and DDT were used in conjunction with TaqMan^® SNP Genotyping Assays to characterize mutation profiles of Ae. aegypti.

Results

Screening of the voltage-sensitive sodium channel (Vssc), the pyrethroid target site, revealed mutations at codons 989, 1016 and 1534 in Ae. aegypti from two districts of Jeddah. The triple mutant homozygote (1016G/1534C/989P) was confirmed from Al Safa and Al Rawabi. Bioassays with pyrethroids (Type I and II) and DDT showed that mosquitoes were resistant to each of these compounds based on WHO definitions. An association between Vssc mutations and resistance was established for the Type II pyrethroid, deltamethrin, with one genotype (989P/1016G/1534F) conferring a survival advantage over two others (989S/1016V/1534C and the triple heterozygote). An indication of synergism of Type I pyrethroid activity with piperonyl butoxide suggests that detoxification by cytochrome P450s accounts for some of the pyrethroid resistance response in Ae. aegypti populations from Jeddah.

Conclusions

The results provide a baseline for monitoring and management of resistance as well as knowledge of Vssc genotype frequencies required in Wolbachia release populations to ensure homogeneity with the target field population. Vssc mutation haplotypes observed show some similarity with those from Ae. aegypti in southeast Asia and the Indo-Pacific, but the presence of the triple mutant haplotype in three genotypes indicates that the species in this region may have a unique population history.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04867-3.

Assessing the atmospheric fate of pesticides used to control mosquito populations in Houston, TX

During the summer months, urban areas are literal hot spots of mosquito-borne disease transmission and air pollution. Public health authorities release aerosolized pesticides directly into the atmosphere to help control adult mosquito populations and thereby reduce the threat of diseases, such as Zika Virus. The primary adulticides (i.e. pesticides used to control adult mosquito populations) in Houston, TX are permethrin and malathion. These adulticides are typically sprayed at night using ultra-low volume sprayers. Particulate matter (PM) samples including total suspended and fine PM (PM < 2.5 μm in aerodynamic diameter) were collected at four ground-based sites across Houston in 2013 and include daytime, nighttime, and 24 h samples. Malathion is initially sprayed as coarse aerosol (5-25 μm), but is measured in fine aerosol (<2.5 μm) and coarse aerosol in the urban atmosphere. Particle size is relevant both for deposition velocities and for human exposure. Atmospheric permethrin concentrations measured in nighttime samples peak at 60 ng m^-3, while malathion nighttime concentrations peak near 40 ng m^-3. Malaoxon, an oxidation product of malathion, was also frequently detected at concentrations >10 ng m^-3, indicating significant nighttime oxidation. Based on the loss of malathion and the increase in malaoxon, the atmospheric half-life of malathion in Houston was estimated at <12 h, which was significantly shorter than previous half-life estimates (∼days). Importantly, malaoxon is estimated to be 22-33 times more toxic to humans than malathion. Both the aerosol size and the half-life are critical for mosquito control, human exposure, and risk assessment of these routine pesticides.

Extraction of permethrin from impregnated fabrics for determination by ultra-high performance liquid chromatography with diode array detection

Permethrin is a synthetic pyrethroid insecticide that is largely used in the impregnation of fabrics employed for different purposes. This paper reports a detailed study on the conditions for its extraction from fabrics and for its determination by ultra-high performance liquid chromatography with diode array detection (UHPLC-DAD). Several parameters that could affect the extraction efficiency of permethrin were evaluated, such as the extraction time, agitating mode (mechanical or ultrasound-assisted), solvent type (methanol or acetonitrile), concentration, and volume. Under optimized conditions, the extraction was performed for 10 min using a 2 × 2 cm piece of impregnated fabric and 5 mL of pure methanol. The flask containing the sample and the solvent was shaken mechanically using a horizontal roller mixer. The accuracy of the method was assessed by a recovery test, which presented satisfactory results ranging from 86.8% to 95.2%. The method was employed in the analysis of nine samples of commercial fabrics of different colors and grammages that were impregnated with permethrin. The concentration of permethrin found in these samples varied between 25.6 ± 4.2 and 934 ± 119 mg m^-2.

Lacto-N-fucopentaose-III (LNFPIII) ameliorates acute aberrations in hippocampal synaptic transmission in a Gulf War Illness animal model

Approximately one-third of Persian Gulf War veterans are afflicted by Gulf War Illness (GWI), a chronic multisymptom condition that fundamentally presents with cognitive deficits (i.e., learning and memory impairments) and neuroimmune dysfunction (i.e., inflammation). Factors associated with GWI include overexposures to neurotoxic pesticides and nerve agent prophylactics such as permethrin (PM) and pyridostigmine bromide (PB), respectively. GWI-related neurological impairments associated with PB-PM overexposures have been recapitulated in animal models; however, there is a paucity of studies assessing PB-PM-related aberrations in hippocampal synaptic plasticity and transmission that may underlie behavioral impairments. Importantly, FDA-approved neuroactive treatments are currently unavailable for GWI. In the present study, we assessed the efficacy of an immunomodulatory therapeutic, lacto-N-fucopentaose-III (LNFPIII), on ameliorating acute effects of in vivo PB-PM exposure on synaptic plasticity and transmission as well as trophic factor/cytokine expression along the hippocampal dorsoventral axis. PB-PM exposure resulted in hippocampal synaptic transmission deficits 48 h post-exposure, a response that was ameliorated by LNFPIII coadministration, particularly in the dorsal hippocampus (dH). LNFPIII coadministration also enhanced synaptic transmission in the dH and the ventral hippocampus (vH). Notably, LNFPIII coadministration elevated long-term potentiation in the dH. Further, PB-PM exposure and LNFPIII coadministration uniquely altered key inflammatory cytokine and trophic factor production in the dH and the vH. Collectively, these findings demonstrate that PB-PM exposure impaired hippocampal synaptic responses 48 h post-exposure, impairments that differentially manifested along the dorsoventral axis. Importantly, LNFPIII ameliorated GWI-related electrophysiological deficits, a beneficial effect indicating the potential efficacy of LNFPIII for treating GWI.

Integrity, use and care of long-lasting insecticidal nets in Kirinyaga County, Kenya

Background

Vector control is an essential component in prevention and control of malaria in malaria endemic areas. Insecticide treated nets is one of the standard tools recommended for malaria vector control. The objective of the study was to determine physical integrity and insecticidal potency of long-lasting insecticidal nets (LLINs) used in control of malaria vector in Kirinyaga County, Kenya.

Method

The study targeted households in an area which had received LLINs during mass net distribution in 2016 from Ministry of Health. A total of 420 households were sampled using systematic sampling method, where the household heads consented to participate in the study. A semi-structured questionnaire was administered to assess care and use while physical examination was used to determine integrity.

Chemical concentration was determined by gas chromatography mass spectroscopy (GC-MS). Data analysis was done using Statistical Package for Social Sciences (SPSS) version 19.

Results

After 18 months of use, 96.9% (95% CI: 95.2–98.6%) of the distributed nets were still available. Regarding net utilization, 94.1% of household heads reported sleeping under an LLIN the previous night. After physical examination, 49.9% (95% CI: 43–52.8%) of the bed nets had at least one hole. The median number of holes of any size was 2[interquartile range (IQR) 1–4], and most holes were located on the lower part of the nets, [median 3 (IQR 2–5)]. Only 15% of the nets with holes had been repaired. The median concentration for α-cypermethrin was 7.15 mg/m² (IQR 4.25–15.31) and 0.00 mg/g (IQR 0.00–1.99) for permethrin. Based on pHI, Chi-square test varied significantly with the manufacturer (X _{(6, N = 389)} = 29.14, p = 0.04). There was no significant difference between nets with different number of washes (X²(2) = 4.55, p = 0.103).

Conclusion

More than three-quarters of the nets supplied had survived and insecticidal potency was adequate in vector control. Standard procedure for field evaluation of surface insecticidal content available to a mosquito after landing on a net to rest is recommended.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10882-x.

Effects of pyrethroids on brain development and behavior: Deltamethrin

Deltamethrin (DLM) is a Type II pyrethroid pesticide widely used in agriculture, homes, public spaces, and medicine. Epidemiological studies report that increased pyrethroid exposure during development is associated with neurobehavioral disorders. This raises concern about the safety of these chemicals for children. Few animal studies have explored the long-term effects of developmental exposure to DLM on the brain. Here we review the CNS effects of pyrethroids, with emphasis on DLM. Current data on behavioral and cognitive effects after developmental exposure are emphasized. Although, the acute mechanisms of action of DLM are known, how these translate to long-term effects is only beginning to be understood. But existing data clearly show there are lasting effects on locomotor activity, acoustic startle, learning and memory, apoptosis, and dopamine in mice and rats after early exposure. The most consistent neurochemical findings are reductions in the dopamine transporter and the dopamine D1 receptor. The data show that DLM is developmentally neurotoxic but more research on its mechanisms of long-term effects is needed.

Trophic transfer, bioaccumulation and transcriptomic effects of permethrin in inland silversides, Menidia beryllina, under future climate scenarios

Global climate change (GCC) significantly affects aquatic ecosystems. Continual use of pyrethroid insecticides results in contamination of these ecosystems and concurrent GCC raises the potential for synergistic effects. Resistance to pyrethroids has been documented in Hyalella azteca, a common epibenthic amphipod and model organism. Resistant H. azteca can bioconcentrate elevated amounts of pyrethroids and represent a threat to consumers via trophic transfer. In the present study, a predator of H. azteca, the inland silverside (Menidia beryllina), was used to examine the impacts of GCC on pyrethroid bioaccumulation via trophic transfer from resistant prey organisms. M. beryllina were fed ¹⁴C-permethrin dosed pyrethroid-resistant H. azteca for 14 days at three salinities (6, 13 and 20 practical salinity units (PSU)) and two temperatures (18 and 23 °C). Fish were analyzed for total body residues, percent parent compound and percent metabolites. Gene expression in liver and brain tissue were evaluated to assess whether dietary bioaccumulation of permethrin would impact detoxification processes, metabolism, and general stress responses. M. beryllina bioaccumulated significant amounts of permethrin across all treatments, ranging from 39 to 557 ng g^-1 lipid. No statistically significant effect of temperature was found on total bioaccumulation. Salinity had a significant effect on total bioaccumulation, owing to greater bioaccumulation at 6 PSU compared to 13 and 20 PSU, which may be due to alterations to xenobiotic elimination. Permethrin bioaccumulation and the interaction with temperature and salinity elicited significant transcriptional responses in genes relating to detoxification, growth, development, and immune response. Given the increased prevalence of pesticide-resistant aquatic invertebrates, GCC-induced alterations to temperature and salinity, and the predicted increase in pesticide usage, these findings suggest trophic transfer may play an important role in pesticide bioaccumulation and effects in predatory fish.

New mosquito repellency bioassay for evaluation of repellents and pyrethroids using an attractive blood-feeding device

BACKGROUND

With the increasing threat of the worldwide spread of mosquito-borne infectious diseases, consumer interest in anti-mosquito textiles that protect against mosquito bites is also increasing. Accordingly, repellent- or insecticide-treated textiles are gaining popularity. The standardization of commercial textile products is, therefore, indispensable for an authentic and objective evaluation of these products. Here we report a textile testing method using an artificial blood-feeding system that does not involve human volunteers or live animals, which aligns with the policy of protecting human and animal welfare.

METHODS

The attractive blood-feeding device (ABFD) was designed using the Hemotek® membrane feeding system. The repellency of DEET, icaridin and permethrin was assayed using unfed female adults of Aedes albopictus (Skuse) under two different test conditions, namely choice and no-choice tests. The choice test consisted of two feeding units, one chemically treated and untreated, that were installed on the ABFD; mosquitoes attracted to and resting on the feeding units were counted and the overall blood-feeding rates recorded. The no-choice test consisted of two feeding units treated with the same chemical that were installed on the ABFD; mosquitoes attracted to and resting on the feeding units were counted and the blood-feeding rates were recorded. A control test was conducted using two feeding units, both sides of which were untreated.

RESULTS

In the choice test, high repellency (> 95% inhibition of resting on the treated surface) of 1% DEET and 2% icaridin was observed, whereas 2% permethrin was not an effective repellent. Also, high blood-feeding inhibition (> 95%) was observed for 2% DEET and 2% icaridin. In the no-choice test, high repellency was observed for 1% DEET and 2% icaridin, whereas the repellency of 2% permethrin was low. Also, high blood-feeding inhibition was observed for 2% DEET, 4% icaridin and 2% permethrin.

CONCLUSIONS

The accuracy and reproducibility of the developed method demonstrate that the ABFD may be widely used for fundamental experiments in the field of mosquito physiology, for the development of new repellent chemicals and in evaluation studies of mosquito repellent products, such as anti-mosquito textiles. The further development of the membrane and feeding unit systems will enable a more practical evaluation of mosquito repellents and blood-feeding inhibitors, such as pyrethroids.

Contact toxicity of three insecticides for use in tier I pesticide risk assessments with Megachile rotundata (Hymenoptera: Megachilidae)

The current pesticide risk assessment paradigm may not adequately protect solitary bees as it focuses primarily on the honey bee (Apis mellifera). The alfalfa leafcutting bee (Megachile rotundata) is a potential surrogate species for use in pesticide risk assessment for solitary bees in North America. However, the toxicity of potential toxic reference standards to M. rotundata will need to be determined before pesticide risk assessment tests (tier I trials) can be implemented. Therefore, we assessed the acute topical toxicity and generated LD50 values for three insecticides: dimethoate (62.08 ng a.i./bee), permethrin (50.01 ng a.i./bee), and imidacloprid (12.82 ng a.i/bee). The variation in the mass of individual bees had a significant but small effect on these toxicity estimates. Overall, the toxicity of these insecticides to M. rotundata were within the 10-fold safety factor currently used with A. mellifera toxicity estimates from tier I trials to estimate risk to other bee species. Therefore, tier I pesticide risk assessments with solitary bees may not be necessary, and efforts could be directed to developing more realistic, higher-tier pesticide risk assessment trials for solitary bees.