Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 10.381
Filtrar
1.
Environ Geochem Health ; 46(4): 117, 2024 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-38478119

RESUMO

Continuous exposure to airborne pesticides causes their gradual accumulation in the human body, eventually posing a threat to human health. To the best of our knowledge, risk assessment study of pesticide non-occupational exposure to residents in agricultural areas has not been conducted in China. In this study, air samples (gas and dust) were collected from inside and outside residences of seven households and an area near the field in a grain-growing area (wheat and maize rotation) for eight months, and the pesticides present were examined both qualitatively and quantitatively. Using a 95% confidence interval, 9 out of 16 pesticides were detected, namely acetamiprid, acetochlor, atrazine, flucarbazone-sodium, imidacloprid, methyldisulfuron-methyl, nicosulfuron-methyl, pendimethalin, and beta-cyhalothrin, and their safety was subsequently evaluated. The results showed that the inhalation exposure of households to beta-cyhalothrin exceeded the acceptable range in the first residential, and the excess lifetime cancer risk of acetochlor inhalation exposure in six households and area around the field exceeds 1E-6, which highlights the need to strengthen preventive screening for cancer risk.


Assuntos
Neoplasias , Nitrilas , Praguicidas , Piretrinas , Toluidinas , Humanos , Praguicidas/toxicidade , Praguicidas/análise , Exposição Ambiental/análise , Medição de Risco
2.
Malar J ; 23(1): 72, 2024 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-38468292

RESUMO

BACKGROUND: Recently, bacterial endosymbiont, including Wolbachia and Microsporidia were found to limit the infection of Anopheles mosquitoes with Plasmodium falciparum. This study aimed to investigate the natural presence of key transmission-blocking endosymbionts in Anopheles gambiae and Anopheles coluzzii in Southern Benin. METHODS: The present study was conducted in seven communes (Cotonou, Porto-Novo, Aguégués, Ifangni, Pobè Athiémé, and Grand-Popo) of Southern Benin. Anopheles were collected using indoor/outdoor Human Landing Catches (HLCs) and Pyrethrum Spray Catches (PSCs). Following morphological identification, PCR was used to identify An. gambiae sensu lato (s.l.) to species level and to screen for the presence of both Wolbachia and Microsporidia. Plasmodium falciparum sporozoite infection was also assessed using ELISA. RESULTS: Overall, species composition in An. gambiae s.l. was 53.7% An. coluzzii, while the remainder was An. gambiae sensu stricto (s.s.). Combined data of the two sampling techniques revealed a mean infection prevalence with Wolbachia of 5.1% (95% CI 0.90-18.6) and 1.3% (95% CI 0.07-7.8) in An. gambiae s.s. and An. coluzzii, respectively. The mean infection prevalence with Microsporidia was 41.0% (95% CI 25.9-57.8) for An. gambiae s.s. and 57.0% (95% CI 45.4-67.9) for An. coluzzii. Wolbachia was only observed in Ifangni, Pobè, and Cotonou, while Microsporidia was detected in all study communes. Aggregated data for HLCs and PSCs showed a sporozoite rate (SR) of 0.80% (95% CI 0.09-2.87) and 0.69% (95% CI 0.09-2.87) for An. gambiae and An. coluzzii, respectively, with a mean of 0.74% (95% CI 0.20-1.90). Of the four individual mosquitoes which harboured P. falciparum, none were also infected with Wolbachia and one contained Microsporidia. CONCLUSIONS: The present study is the first report of natural infections of field-collected An. gambiae s.l. populations from Benin with Wolbachia and Microsporidia. Sustained efforts should be made to widen the spectrum of bacteria identified in mosquitoes, with the potential to develop endosymbiont-based control tools; such interventions could be the game-changer in the control of malaria and arboviral disease transmission.


Assuntos
Anopheles , Malária Falciparum , Piretrinas , Wolbachia , Animais , Humanos , Benin/epidemiologia , Estudos Transversais , Mosquitos Vetores , Malária Falciparum/epidemiologia , Esporozoítos
3.
Sci Rep ; 14(1): 6029, 2024 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-38472262

RESUMO

Fall armyworm, Spodoptera frugiperda (FAW) is a cosmopolitan crop pest species that has recently become established in sub-Saharan Africa and Southeast Asia. Current FAW control is almost entirely dependent on synthetic pesticides. Biopesticides offer a more sustainable alternative but have limitations. For example, pyrethrum is an effective botanical insecticide with low mammalian toxicity but is highly UV labile, resulting in a rapid loss of efficacy in the field. Beauveria bassiana is an entomopathogenic fungus that is more persistent, but there is a time lag of several days before it causes insect mortality and leads to effective control. The combination of these biopesticides could mitigate their drawbacks for FAW control. Here we evaluated the efficacy of pyrethrum and B. bassiana as individual treatments and in combination against 3rd instar FAW. Four different combinations of these two biopesticides were tested, resulting in an antagonistic relationship at the lowest concentrations of B. bassiana and pyrethrum (1 × 104 conidia mL-1 with 25 ppm) and an additive effect for the other 3 combined treatments (1 × 104 conidia mL-1 with 100 ppm and 1 × 105 conidia mL-1 with 25 ppm and 100 ppm pyrethrum). Additionally, a delay in efficacy from B. bassiana was observed when combined with pyrethrum as well as a general inhibition of growth on agar plates. These results appear to show that this particular combination of biopesticides is not universally beneficial or detrimental to pest control strategies and is dependent on the doses of each biopesticide applied. However, the additive effect shown here at specific concentrations does indicate that combining biopesticides could help overcome the challenges of persistence seen in botanical pesticides and the slow establishment of EPF, with the potential to improve effectiveness of biopesticides for IPM.


Assuntos
Praguicidas , Piretrinas , Animais , Spodoptera/fisiologia , Agentes de Controle Biológico , Controle de Pragas , Larva , Mamíferos
4.
Malar J ; 23(1): 65, 2024 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-38431623

RESUMO

BACKGROUND: Neonicotinoids are potential alternatives for controlling pyrethroid-resistant mosquitoes, but their efficacy against malaria vector populations of sub-Saharan Africa has yet to be investigated. The aim of the present study was to test the efficacy of four neonicotinoids against adult populations of the sibling species Anopheles gambiae and Anopheles coluzzii sampled along an urban-to-rural gradient. METHODS: The lethal toxicity of three active ingredients for adults of two susceptible Anopheles strains was assessed using concentration-response assays, and their discriminating concentrations were calculated. The discriminating concentrations were then used to test the susceptibility of An. gambiae and An. coluzzii mosquitoes collected from urban, suburban and rural areas of Yaoundé, Cameroon, to acetamiprid, imidacloprid, clothianidin and thiamethoxam. RESULTS: Lethal concentrations of neonicotinoids were relatively high suggesting that this class of insecticides has low toxicity against Anopheles mosquitoes. Reduced susceptibility to the four neonicotinoids tested was detected in An. gambiae populations collected from rural and suburban areas. By contrast, adults of An. coluzzii that occurred in urbanized settings were susceptible to neonicotinoids except acetamiprid for which 80% mortality was obtained within 72 h of insecticide exposure. The cytochrome inhibitor, piperonyl butoxide (PBO), significantly enhanced the activity of clothianidin and acetamiprid against An. gambiae mosquitoes. CONCLUSIONS: These findings corroborate susceptibility profiles observed in larvae and highlight a significant variation in tolerance to neonicotinoids between An. gambiae and An. coluzzii populations from Yaoundé. Further studies are needed to disentangle the role of exposure to agricultural pesticides and of cross-resistance mechanisms in the development of neonicotinoid resistance in some Anopheles species.


Assuntos
Anopheles , Guanidinas , Inseticidas , Malária , Piretrinas , Tiazóis , Animais , Inseticidas/farmacologia , Camarões , Resistência a Inseticidas , Mosquitos Vetores , Neonicotinoides/farmacologia , Piretrinas/farmacologia
5.
Pestic Biochem Physiol ; 199: 105799, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38458669

RESUMO

Fenpropathrin (FEN), a pyrethroid pesticide, is frequently detected in natural water bodies, unavoidable pose adverse effects to aquatic organisms. However, the harmful effects and potential mechanisms of FEN on aquatic species are poorly understood. In this study, common carp were treatment with FEN at 0.45 and 1.35 µg/L for 14 d, and the toxic effects and underlying mechanisms of FEN on the intestine of carp were revealed. RNA-seq results showed that FEN exposure cause a wide range of transcriptional alterations in the intestine and the differentially expressed genes were mainly enrichment in the pathways related to immune and metabolism. Specifically, FEN exposure induced pathological damage and altered submicroscopic structure of the intestine, elevated the levels of Bacteroides fragilis enterotoxin, altered the contents of claudin-1, occludin, and zonula occluden-1 (ZO-1), and causing injury to the intestinal barrier. In addition, inflammation-related index TNF-α in the serum and IL-6 in the intestinal tissues were generally increased after FEN exposure. Moreover, FEN exposure promoted an increase in reactive oxygen species (ROS), altered the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), upregulated the contents of malondialdehyde (MDA) in the intestines. The apoptosis-related parameter cytochrome c, caspase-9, and caspase-3 were significantly altered, indicating that inflammation reaction, oxidative stress, and apoptosis may be involved in the toxic mechanism of FEN on carp. Moreover, FEN treatment also altered the intestinal flora community significantly, which may affect the intestinal normal physiological function and thus affect the growth of fish. Overall, the present study help to clarify the intestinal reaction mechanisms after FEN treatment, and provide a basis for the risk assessment of FEN.


Assuntos
Carpas , Piretrinas , Animais , Dieta , Carpas/metabolismo , Proteínas de Peixes/genética , Proteínas de Peixes/metabolismo , Proteínas de Peixes/farmacologia , Intestinos , Antioxidantes/farmacologia , Estresse Oxidativo , Inflamação , Piretrinas/toxicidade
6.
Pestic Biochem Physiol ; 199: 105775, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38458682

RESUMO

Insect cuticular protein (ICP) plays an important role in insect growth and development. However, research on the role of ICP in insecticide resistance is very limited. In this study, insect cuticular protein genes LCP17 and SgAbd5 were cloned and characterized in Helicoverpa armigera based on previous transcriptome data. The functions of LCP17 and SgAbd5 genes in fenvalerate resistance were assessed by RNA interference (RNAi), and their response to fenvalerate was further detected. The results showed that LCP17 and SgAbd5 were overexpressed in the fenvalerate-resistant strain comparing with a susceptible strain. The open reading frames of LCP17 and SgAbd5 genes were 423 bp and 369 bp, encoding 141 and 123 amino acids, respectively. LCP17 and SgAbd5 genes were highly expressed in the larval stage, but less expressed in the adult and pupal stages. The expression level of LCP17 and SgAbd5 genes increased significantly after fenvalerate treatment at 24 h. When the cotton bollworms larvae were exposed to fenvalerate at LD50 level, RNAi-mediated silencing of LCP17 and SgAbd5 genes increased the mortality from 50.68% to 68.67% and 63.89%, respectively; the mortality increased to even higher level, which was 73.61%, when these two genes were co-silenced. Moreover, silencing of these two genes caused the cuticle lamellar structure to become loose, which led to increased penetration of fenvalerate into the larvae. The results suggested that LCP17 and SgAbd5 may be involved in the resistance of cotton bollworm to fenvalerate, and LCP17 and SgAbd5 could serve as potential targets for H. armigera control.


Assuntos
Inseticidas , Mariposas , Nitrilas , Piretrinas , Animais , Inseticidas/toxicidade , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Mariposas/genética , Mariposas/metabolismo , Larva/genética , Larva/metabolismo
7.
Parasit Vectors ; 17(1): 98, 2024 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-38429846

RESUMO

BACKGROUND: For decades, various agrochemicals have been successfully repurposed for mosquito control. However, preexisting resistance caused in larval and adult populations by unintentional pesticide exposure or other cross-resistance mechanisms poses a challenge to the efficacy of this strategy. A better understanding of larval adaptation to the lethal and sublethal effects of residual pesticides in aquatic habitats would provide vital information for assessing the efficacy of repurposed agrochemicals against mosquitoes. METHODS: We reared field-collected mosquito larvae in water containing a concentration of agrochemical causing 100% mortality in susceptible mosquitoes after 24 h (lethal concentration). Using this experimental setup, we tested the effect of lethal concentrations of a pyrrole (chlorfenapyr, 0.10 mg/l), a pyrethroid (deltamethrin, 1.5 mg/l), and three neonicotinoids including imidacloprid (0.075 mg/l), acetamiprid (0.15 mg/l), and clothianidin (0.035 mg/l) on mortality rates, growth, and survival in third-instar larvae of the two sibling species Anopheles gambiae and Anopheles coluzzii collected from Yaoundé, Cameroon. RESULTS: We found that An. gambiae and An. coluzzii larvae were susceptible to chlorfenapyr and were killed within 24 h by a nominal concentration of 0.10 mg/l. Consistent with strong resistance, deltamethrin induced low mortality in both species. Lethal concentrations of acetamiprid, imidacloprid, and clothianidin strongly inhibited survival, growth, and emergence in An. coluzzii larvae. By contrast, depending on the active ingredient and the population tested, 5-60% of immature stages of An. gambiae were able to grow and emerge in water containing a lethal concentration of neonicotinoids, suggesting cross-resistance to this class of insecticides. CONCLUSIONS: These findings corroborate susceptibility profiles observed in adults and suggest that unintentional pesticide exposure or other cross-resistance processes could contribute to the development of resistance to neonicotinoids in some Anopheles populations.


Assuntos
Anopheles , Guanidinas , Inseticidas , Nitrilas , Nitrocompostos , Piretrinas , Tiazóis , Animais , Água , Resistência a Inseticidas , Mosquitos Vetores , Camarões/epidemiologia , Neonicotinoides/farmacologia , Inseticidas/farmacologia , Larva
8.
Parasit Vectors ; 17(1): 115, 2024 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-38454494

RESUMO

BACKGROUND: Indoor residual spraying (IRS) was first implemented in the Atacora department, Benin from 2011 to 2012 using bendiocarb (carbamate) followed by annual spraying with pirimiphos-methyl (organophosphate) from 2013 to 2018. Before and after IRS implementation in Atacora, standard pyrethroid insecticide-treated bed nets were the main method of vector control in the area. This study investigated the knockdown resistance (kdr) gene (L1014F) and the acetylcholinesterase (ace-1) gene (G119S), before and during IRS implementation, and 4-years after IRS withdrawal from Atacora. This was done to assess how changes in insecticide pressure from indoor residual spraying may have altered the genotypic resistance profile of Anopheles gambiae s.l. METHOD: Identification of sibling species of An. gambiae s.l. and detection of the L1014F mutation in the kdr gene and G119S mutation in ace-1 genes was done using molecular analysis. Allelic and genotypic frequencies were calculated and compared with each other before and during IRS implementation and 4 years after IRS withdrawal. The Hardy-Weinberg equilibrium and genetic differentiation within and between populations were assessed. RESULTS: Prevalence of the L1014F mutation in all geographic An. gambiae s.l. (An. gambiae s.s., Anopheles. coluzzii, Anopheles. arabiensis, and hybrids of "An. gambiae s.s. and An. coluzzii") populations increased from 69% before IRS to 87% and 90% during and after IRS. The G119S allele frequency during IRS (20%) was significantly higher than before IRS implementation (2%). Four years after IRS withdrawal, allele frequencies returned to similar levels as before IRS (3%). Four years after IRS withdrawal, the populations showed excess heterozygosity at the ace-1 gene and deficit heterozygosity at the kdr gene, whereas both genes had excess heterozygosity before and during IRS (FIS < 0). No genetic differentiation was observed within the populations. CONCLUSIONS: This study shows that the withdrawal of IRS with bendiocarb and pirimiphos-methyl may have slowed down the selection of individual mosquitoes with ace-1 resistance alleles in contrast to populations of An. gambiae s.l. with the L1014F resistance allele of the kdr gene. This may suggest that withdrawing the use of carbamates or organophosphates from IRS or rotating alternative insecticides with different modes of action may slow the development of ace-1 insecticide-resistance mutations. The increase in the prevalence of the L1014F mutation of the kdr gene in the population, despite the cessation of IRS, could be explained by the growing use of pyrethroids and DDT in agriculture and for other domestic use. More observational studies in countries where carbamates or organophosphates are still being used as public health insecticides may provide additional insights into these associations.


Assuntos
Anopheles , Inseticidas , Fenilcarbamatos , Piretrinas , Animais , Inseticidas/farmacologia , Anopheles/genética , Benin , Alelos , Acetilcolinesterase/genética , Mosquitos Vetores/genética , Piretrinas/farmacologia , Resistência a Inseticidas/genética , Carbamatos/farmacologia , Organofosfatos/farmacologia , Controle de Mosquitos/métodos
9.
Parasit Vectors ; 17(1): 117, 2024 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-38454517

RESUMO

BACKGROUND: Indoor residual spraying (IRS) capitalizes on the natural behavior of mosquitoes because Aedes aegypti commonly seeks indoor resting sites after a blood meal. This behavior allows mosquitoes to be exposed to insecticide-treated surfaces and subsequently killed. Combinations of deltamethrin and clothianidin with different modes of action have shown promise in IRS, effectively targeting both susceptible and pyrethroid-resistant malaria vectors. However, the effects of this approach on Aedes mosquitoes remain unclear. The present study tested the effects of deltamethrin-clothianidin mixture treatment on behavioral responses and life history traits of Taiwanese and Indonesian populations of Ae. aegypti. METHODS: We adopted an excito-repellent approach to explore the behavioral responses of pyrethroid-resistant Ae. aegypti populations from Indonesia and Taiwan to a deltamethrin-clothianidin mixture used in contact irritancy and non-contact repellency treatments. We further evaluated the life history traits of surviving mosquitoes (i.e., delayed mortality after 7-day post-treatment, longevity, fecundity, and egg hatching) and investigated the potential transgenerational hormetic effects of insecticide exposure (i.e., development rate and survival of immatures and adult mosquitos). RESULTS: All tested field populations of Ae. aegypti displayed strong contact irritancy responses; the percentage of escape upon insecticide exposure ranged from 38.8% to 84.7%. However, repellent effects were limited, with the escape percentage ranging from 4.3% to 48.9%. We did not observe immediate knockdown or mortality after 24 h, and less than 15% of the mosquitoes exhibited delayed mortality after a 7-day exposure period. However, the carryover effects of insecticide exposure on the survival of immature mosquitoes resulted in approximately 25% higher immature mortality than that in the control. By contrast, we further documented stimulated survivor reproduction and accelerated transgenerational immature development resulting from the sublethal effects of the insecticide mixture. In particular, the number of eggs laid by treated (both treatments) female mosquitoes increased by at least 60% compared with that of eggs laid by control female mosquitoes. CONCLUSIONS: IRS with deltamethrin-clothianidin effectively deters Aedes mosquitoes from entering residential areas and thereby reduces mosquito bites. However, the application rate (deltamethrin: 25 mg/m2; clothianidin: 200 mg/m2) may be insufficient to effectively kill Aedes mosquitoes. Insecticide response appears to vary across mosquito species; their behavioral and physiological responses to sublethal doses have crucial implications for mosquito control programs.


Assuntos
Aedes , Guanidinas , Inseticidas , Traços de História de Vida , Neonicotinoides , Nitrilas , Piretrinas , Tiazóis , Feminino , Animais , Inseticidas/farmacologia , Aedes/fisiologia , Indonésia , Resistência a Inseticidas , Óvulo , Piretrinas/farmacologia , Controle de Mosquitos/métodos , Mosquitos Vetores
10.
Environ Geochem Health ; 46(4): 126, 2024 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-38483641

RESUMO

The migration of organochlorine pesticides (OCPs) and cypermethrin residues from internal organs to edible tissues of ice-held Labeo rohita (rohu) was investigated in this study. The liver (246 µg/kg) had the highest level of ∑OCP residues, followed by the gills (226 µg/kg), intestine (167 µg/kg), and muscle tissue (54 µg/kg). The predominant OCPs in the liver and gut were endosulfan (53-66 µg/kg), endrin (45-53 µg/kg), and dichloro-diphenyl-trichloroethane (DDT; 26-35 µg/kg). The ∑OCP residues in muscle increased to 152 µg/kg when the entire rohu was stored in ice, but they decreased to 129 µg/kg in gill tissues. On days 5 and 9, the total OCPs in the liver increased to 317 µg/kg and 933 µg/kg, respectively. Beyond day 5 of storage, total internal organ disintegration had led to an abnormal increase in OCP residues of liver-like mass. Despite a threefold increase in overall OCP residues by day 9, accumulation of benzene hexachloride (BHC) and heptachlor was sixfold, endrin and DDT were fourfold, aldrin was threefold, and endosulfan and cypermethrin were both twofold. Endosulfan, DDT, endrin, and heptachlor were similarly lost in the gills at a rate of 40%, while aldrin and BHC were also lost at 60 and 30%, respectively. The accumulation of OCP residues in tissues has been attributed to particular types of fatty acid derivatives. The study concluded that while pesticide diffusion to edible tissues can occur during ice storage, the levels observed were well below the allowable limit for endosulfan, endrin, and DDT.


Assuntos
Hidrocarbonetos Clorados , Resíduos de Praguicidas , Praguicidas , Piretrinas , Humanos , Animais , Praguicidas/toxicidade , Praguicidas/análise , Gelo , Aldrina/análise , DDT/análise , Endossulfano/toxicidade , Endossulfano/análise , Endrin , Resíduos de Praguicidas/análise , Hidrocarbonetos Clorados/toxicidade , Hidrocarbonetos Clorados/análise , Heptacloro/análise , Hexaclorocicloexano , Monitoramento Ambiental
12.
Malar J ; 23(1): 77, 2024 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-38486288

RESUMO

BACKGROUND: Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To address this challenge, the World Health Organization (WHO) recommends the use of piperonyl butoxide (PBO) LLINs in areas where pyrethroid resistance is confirmed to be mediated by mixed function oxidase (MFO). METHODS: This study assessed the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to WHO tube bioassays with 4% DDT and 0.05% deltamethrin insecticides. Additionally, the study explored the effect of piperonyl butoxide (PBO) synergist by sequentially exposing mosquitoes to deltamethrin (0.05%) alone, PBO (4%) + deltamethrin (0.05%), and PBO alone. The Anopheles mosquitoes were further identified morphologically and molecularly. RESULTS: The findings revealed that An. gambiae sensu stricto (s.s.) (62%) was more prevalent than Anopheles arabiensis (38%). The WHO tube bioassays confirmed resistance to deltamethrin 0.05% in the Oshikoto, Kunene, and Kavango West regions, with mortality rates of 79, 86, and 67%, respectively. In contrast, An. arabiensis displayed resistance to deltamethrin 0.05% in Oshikoto (82% mortality) and reduced susceptibility in Kavango West (96% mortality). Notably, there was reduced susceptibility to DDT 4% in both An. gambiae s.s. and An. arabiensis from the Kavango West region. Subsequently, a subsample from PBO synergist assays in 2020 demonstrated a high proportion of An. arabiensis in Oshana (84.4%) and Oshikoto (73.6%), and 0.42% of Anopheles quadriannulatus in Oshana. Non-amplifiers were also present (15.2% in Oshana; 26.4% in Oshikoto). Deltamethrin resistance with less than 95% mortality, was consistently observed in An. gambiae s.l. populations across all sites in both 2020 and 2021. Following pre-exposure to the PBO synergist, susceptibility to deltamethrin was fully restored with 100.0% mortality at all sites in 2020 and 2021. CONCLUSIONS: Pyrethroid resistance has been identified in An. gambiae s.s. and An. arabiensis in the Kavango West, Kunene, and Oshikoto regions, indicating potential challenges for pyrethroid-based IRS and LLINs. Consequently, the data highlights the promise of pyrethroid-PBO LLINs in addressing resistance issues in the region.


Assuntos
Anopheles , Mosquiteiros Tratados com Inseticida , Inseticidas , Nitrilas , Piretrinas , Animais , Inseticidas/farmacologia , Butóxido de Piperonila/farmacologia , DDT , Namíbia , Mosquitos Vetores , Piretrinas/farmacologia , Resistência a Inseticidas , Controle de Mosquitos
13.
Parasit Vectors ; 17(1): 103, 2024 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-38431631

RESUMO

BACKGROUND: Increasing metabolic resistance in malaria vector mosquitoes resulted in the development of insecticide-treated nets (ITNs) with active ingredients (AI) that target them. Bioassays that accurately measure the mortality induced by these AIs on ITNs are needed. Mosquito metabolic enzyme expression follows a circadian rhythm. Thus, this study assessed (i) influence of the time of day of mosquito exposure and (ii) timing of assessment of mortality post exposure (24 and 72 h) to ITNs against vectors that are susceptible to pyrethroids and those with metabolic and knockdown resistance mechanisms. METHODS: Two cone bioassay experiments were conducted following World Health Organization (WHO) guidelines. Firstly, on ITNs incorporated with 2 g AI/kg of deltamethrin (DM) alone, or combined with 8 g AI/kg piperonyl butoxide (PBO) synergist, during the day (9:00-14:00 h) and repeated in the evening (18:00-20:00 h). This was followed by a confirmatory experiment during the afternoon (12:00-14:00 h) and repeated in the night (22:00-24:00 h) using mosquitoes unexposed or pre-exposed to PBO for 1 h before exposure to DM ITNs. Each net piece was tested with a minimum of eight cones per time (N = 24). The outcome was mortality after 24 h (M24) or 72 h (M72) of holding. RESULTS: The cone bioassays performed using metabolic resistant mosquitoes during the evening showed significantly lower M24 than those performed in the day for DM: odds ratio (OR) 0.14 [95% confidence interval (CI) 0.06-0.30, p < 0.0001] and DM PBO [OR 0.29 (95% CI 0.18-0.49, p < 0.0001). M72 was higher than M24 for metabolic resistant mosquitoes exposed to DM [OR 1.44 (95% CI 1.09-1.88), p = 0.009] and DM PBO [OR 1.82 (95% CI 1.42-2.34), p < 0.0001]. An influence of hour of experiment and time of assessment was not observed for mosquitoes that had knockdown resistance or that were pyrethroid-susceptible. CONCLUSIONS: Time of day of experiment and hour of assessment of delayed mortality after exposure of mosquitoes are important considerations in evaluating insecticides that interact with mosquito metabolism to counter metabolic resistant mosquitoes. This is important when evaluating field-aged ITNs that may have lower concentrations of AI.


Assuntos
Anopheles , Mosquiteiros Tratados com Inseticida , Inseticidas , Malária , Piretrinas , Animais , Inseticidas/farmacologia , Controle de Mosquitos/métodos , Mosquitos Vetores , Piretrinas/farmacologia , Butóxido de Piperonila/farmacologia , Resistência a Inseticidas
14.
Malar J ; 23(1): 69, 2024 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-38443984

RESUMO

BACKGROUND: There are several indications that pesticides used in agriculture contribute to the emergence and spread of resistance of mosquitoes to vector control insecticides. However, the impact of such an indirect selection pressure has rarely been quantified and the molecular mechanisms involved are still poorly characterized. In this context, experimental selection with different agrochemical mixtures was conducted in Anopheles gambiae. The multi-generational impact of agrochemicals on insecticide resistance was evaluated by phenotypic and molecular approaches. METHODS: Mosquito larvae were selected for 30 generations with three different agrochemical mixtures containing (i) insecticides, (ii) non-insecticides compounds, and (iii) both insecticide and non-insecticide compounds. Every five generations, the resistance of adults to deltamethrin and bendiocarb was monitored using bioassays. The frequencies of the kdr (L995F) and ace1 (G119S) target-site mutations were monitored every 10 generations. RNAseq was performed on all lines at generation 30 in order to identify gene transcription level variations and polymorphisms associated with each selection regime. RESULTS: Larval selection with agrochemical mixtures did not affect bendiocarb resistance and did not select for ace1 mutation. Contrastingly, an increased deltamethrin resistance was observed in the three selected lines. Such increased resistance was not majorly associated with the presence of kdr L995F mutation in selected lines. RNA-seq identified 63 candidate resistance genes over-transcribed in at least one selected line. These include genes coding for detoxification enzymes or cuticular proteins previously associated with insecticide resistance, and other genes potentially associated with chemical stress response. Combining an allele frequency filtering with a Bayesian FST-based genome scan allowed to identify genes under selection across multiple genomic loci, supporting a multigenic adaptive response to agrochemical mixtures. CONCLUSION: This study supports the role of agrochemical contaminants as a significant larval selection pressure favouring insecticide resistance in malaria vectors. Such selection pressures likely impact kdr mutations and detoxification enzymes, but also more generalist mechanisms such as cuticle resistance, which could potentially lead to cross-tolerance to unrelated insecticide compounds. Such indirect effect of global landscape pollution on mosquito resistance to public health insecticides deserves further attention since it can affect the nature and dynamics of resistance alleles circulating in malaria vectors and impact the efficacy of control vector strategies.


Assuntos
Anopheles , Poluentes Ambientais , Inseticidas , Malária , Nitrilas , Fenilcarbamatos , Piretrinas , Animais , Anopheles/genética , Agroquímicos , Inseticidas/farmacologia , Teorema de Bayes , Resistência a Inseticidas/genética , Mosquitos Vetores/genética , Perfilação da Expressão Gênica
15.
Sci Rep ; 14(1): 5892, 2024 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-38467789

RESUMO

This study was conducted to evaluate the ameliorative, anti-inflammatory, antioxidant, and chemical detoxifying activities of Echinacea purpurea ethanolic extract (EEE) against bifenthrin-induced renal injury. Adult male albino rats (160-200 g) were divided into four groups (10 rats each) and orally treated for 30 days as follows: (1) normal control; (2) healthy animals were treated with EEE (465 mg/kg/day) dissolved in water; (3) healthy animals were given bifenthrin (7 mg/kg/day) dissolved in olive oil; (4) animals were orally administered with EEE 1-h prior bifenthrin intoxication. The obtained results revealed that administration of the animals with bifenthrin caused significant elevations of serum values of urea, creatinine, ALAT and ASAT, as well as renal inflammatory (IL-1ß, TNF-α & IFN-γ), apoptotic (Caspase-3) and oxidative stress (MDA and NO) markers coupled with a marked drop in the values of renal antioxidant markers (GSH, GPx, and SOD) in compare to those of normal control. Administration of EEE prior to bifenthrin resulted in a considerable amelioration of the mentioned deteriorated parameters near to that of control; moreover, the extract markedly improved the histological architecture of the kidney. In conclusion, Echinacea purpurea ethanolic extract has promising ameliorative, antioxidant, anti-inflammatory, renoprotective, and detoxifying efficiencies against bifenthrin-induced renal injury.


Assuntos
Antioxidantes , Echinacea , Rim , Extratos Vegetais , Piretrinas , Masculino , Ratos , Animais , Antioxidantes/farmacologia , Antioxidantes/metabolismo , Rim/metabolismo , Estresse Oxidativo , Etanol/farmacologia , Anti-Inflamatórios/farmacologia
16.
J Agric Food Chem ; 72(10): 5165-5175, 2024 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-38437009

RESUMO

Uridine diphosphate-glycosyltransferase (UGT) is a key phase II enzyme in the insect detoxification system. Pyrethroids are commonly used to control the destructive wheat aphid Rhopalosiphum padi. In this study, we found a highly expressed UGT gene, RpUGT344D38, in both λ-cyhalothrin (LCR)- and bifenthrin (BTR)-resistant strains of R. padi. After exposure to λ-cyhalothrin and bifenthrin, the expression levels of RpUGT344D38 were significantly increased in the resistant strains. Knockdown of RpUGT344D38 did not affect the resistance of BTR, but it did significantly increase the susceptibility of LCR aphids to λ-cyhalothrin. Molecular docking analysis demonstrated that RpUGT344D38 had a stable binding interaction with both bifenthrin and λ-cyhalothrin. The recombinant RpUGT344D38 was able to metabolize 50% of λ-cyhalothrin. This study provides a comprehensive analysis of the role of RpUGT344D38 in the resistance of R. padi to bifenthrin and λ-cyhalothrin, contributing to a better understanding of aphid resistance to pyrethroids.


Assuntos
Afídeos , Inseticidas , Nitrilas , Piretrinas , Animais , Simulação de Acoplamento Molecular
17.
Parasit Vectors ; 17(1): 54, 2024 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-38321481

RESUMO

BACKGROUND: Armenia is considered particularly vulnerable to life-threatening vector-borne diseases (VBDs) including malaria, West Nile virus disease and leishmaniasis. However, information relevant for the control of the vectors of these diseases, such as their insecticide resistance profile, is scarce. The present study was conducted to provide the first evidence on insecticide resistance mechanisms circulating in major mosquito and sand fly populations in Armenia. METHODS: Sampling sites were targeted based mainly on previous historical records of VBD occurrences in humans and vertebrate hosts. Initially, molecular species identification on the collected vector samples was performed. Subsequently, molecular diagnostic assays [polymerase chain reaction (PCR), Sanger sequencing, PCR-restriction fragment length polymorphism (RFLP), quantitative PCR (qPCR)] were performed to profile for major insecticide resistance mechanisms, i.e. target site insensitivity in voltage-gated sodium channel (vgsc) associated with pyrethroid resistance, acetylcholinesterase (ace-1) target site mutations linked to organophosphate (OP) and carbamate (CRB) resistance, chitin synthase (chs-1) target site mutations associated with diflubenzuron (DFB) resistance and gene amplification of carboxylesterases (CCEs) associated with resistance to the OP temephos. RESULTS: Anopheles mosquitoes were principally represented by Anopheles sacharovi, a well-known malaria vector in Armenia, which showed no signs of resistance mechanisms. Contrarily, the knockdown resistance (kdr) mutations V1016G and L1014F/C in the vgsc gene were detected in the arboviral mosquito vectors Aedes albopictus and Culex pipiens, respectively. The kdr mutation L1014S was also detected in the sand fly, vectors of leishmaniasis, Phlebotomus papatasi and P. tobbi, whereas no mutations were found in the remaining collected sand fly species, P. sergenti, P. perfiliewi and P. caucasicus. CONCLUSIONS: This is the first study to report on molecular mechanisms of insecticide resistance circulating in major mosquito and sand fly disease vectors in Armenia and highlights the need for the establishment of systematic resistance monitoring practices for the implementation of evidence-based control applications.


Assuntos
Aedes , Anopheles , Culex , Inseticidas , Leishmaniose , Malária , Phlebotomus , Psychodidae , Piretrinas , Animais , Humanos , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Mosquitos Vetores/genética , Acetilcolinesterase/genética , Anopheles/genética , Armênia , Phlebotomus/genética , Mutação
18.
Trials ; 25(1): 151, 2024 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-38419075

RESUMO

BACKGROUND: The massive scale-up of long-lasting insecticidal nets (LLIN) has led to a major reduction in malaria burden in many sub-Saharan African (SSA) countries. The World Health Organization (WHO) has recently issued a strong recommendation for the use of chlorfenapyr-pyrethroid LLINs compared to standard pyrethroid-only LLINs in areas of high insecticide resistance intensity. However, there is still a lack of conclusive evidence on the efficacy of piperonyl butoxide-pyrethroid (PBO-py) LLINs, especially in West Africa, where vector composition and resistance mechanisms may be different from vectors in East Africa. METHODS: This is a three-arm, superiority, triple-blinded, cluster randomised trial, with village as the unit of randomisation. This study conducted in Côte d'Ivoire will evaluate the efficacy on epidemiological and entomological outcomes of (1) the control arm: MAGNet® LN, which contains the pyrethroid, alpha-cypermethrin, (2) VEERALIN® LN, a net combining the synergist PBO and alpha-cypermethrin, and (3) Interceptor® G2 LN, which incorporates chlorfenapyr and alpha-cypermethrin, two adulticides with different mechanisms of action. A total of 33 villages with an average of 200 households per village will be identified, mapped, and randomised in a ratio of 1:1:1. Nets will be distributed at a central point following national guidelines with 1 net for every 2 people. The primary outcome of the trial will be incidence of malaria cases (confirmed by rapid diagnostic test (RDT)) in a cohort of 50 children aged 6 months to 10 years in each cluster, followed for 12 months (active case detection). Secondary outcomes are cross-sectional community prevalence of malaria infection (confirmed by RDT) in the study population at 6 and 12 months post-intervention (50 randomly selected persons per cluster), vector density, entomological inoculation rate (EIR), and phenotypic and genotypic insecticide resistance at baseline and 12 months post-intervention in 3 sentinel villages in each treatment arm. DISCUSSION: In addition to generating further evidence for next-generation LLINs, this study will also provide the first evidence for pyrethroid-PBO nets in a West African setting. This could further inform WHO recommendations on the pragmatic use of pyrethroid-PBO nets. TRIAL REGISTRATION: ClinicalTrials.gov NCT05796193. Registered on April 3, 2023.


Assuntos
Anopheles , Mosquiteiros Tratados com Inseticida , Inseticidas , Malária , Piretrinas , Criança , Animais , Humanos , Butóxido de Piperonila/farmacologia , Côte d'Ivoire/epidemiologia , Estudos Transversais , Controle de Mosquitos , Mosquitos Vetores , Piretrinas/farmacologia , Inseticidas/efeitos adversos , Resistência a Inseticidas , Malária/epidemiologia , Malária/prevenção & controle
19.
Parasit Vectors ; 17(1): 91, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38414050

RESUMO

BACKGROUND: Over the past two decades, dengue fever (DF) has emerged as a significant arboviral disease in Yunnan province, China, particularly in the China-Myanmar border area. Aedes aegypti, an invasive mosquito species, plays a crucial role in transmitting the dengue virus to the local population. Insecticide-based vector control has been the primary tool employed to combat DF, but the current susceptibility status of Ae. aegypti to commonly used insecticides is unknown. Assessment of Ae. aegypti resistance to pyrethroid insecticides and an understanding of the underlying mechanisms of this resistance in the China-Myanmar border region is of significant strategic importance for effectively controlling the DF epidemic in the area. METHODS: Aedes aegypti larvae collected from Ruili and Gengma counties in Yunnan Province were reared to adults in the laboratory and tested for susceptibility to three pyrethroid insecticides (3.20% permethrin, 0.08% lambda-cyhalothrin and 0.20% deltamethrin) by the standard WHO susceptibility bioassay. Genotyping of mutations in the knockdown gene (kdr), namely S989P, V1016G and F1534C, that are responsible for resistance to pyrethroid insecticides was performed using allele-specific PCR methods. A possible association between the observed resistant phenotype and mutations in the voltage-gated sodium channel gene (VGSC) was also studied. RESULTS: Aedes aegypti mosquitoes collected from the two counties and reared in the laboratory were resistant to all of the pyrethroids tested, with the exception of Ae. aegypti from Gengma County, which showed sensitivity to 0.20% deltamethrin. The mortality rate of Ae. aegypti from Ruili county exposed to 3.20% permethrin did not differ significantly from that of Ae. aegypti from Gengma County (χ2 = 0.311, P = 0.577). By contrast, the mortality rate of Ae. aegypti from Ruili County exposed to 0.08% lambda-cyhalothrin and 0.20% deltamethrin, respectively, was significantly different from that of Ae. aegypti from Gengma. There was no significant difference in the observed KDT50 of Ae. aegypti from the two counties to various insecticides. Four mutation types and 12 genotypes were detected at three kdr mutation sites. Based on results from all tested Ae. aegypti, the V1016G mutation was the most prevalent kdr mutation (100% prevalence), followed by the S989P mutation (81.6%) and the F1534C mutation (78.9%). The constituent ratio of VGSC gene mutation types was significantly different in Ae. aegypti mosquitoes from Ruili and those Gengma. The triple mutant S989P + V1016G + F1534C was observed in 274 Ae. aegypti mosquitoes (60.8%), with the most common genotype being SP + GG + FC (31.4%). The prevalence of the F1534C mutation was significantly higher in resistant Ae. aegypti from Ruili (odds ratio [OR] 7.43; 95% confidence interval [CI] 1.71-32.29; P = 0.01) and Gengma (OR 9.29; 95% CI 3.38-25.50; P = 0.00) counties than in susceptible Ae. aegypti when exposed to 3.20% permethrin and 0.08% lambda-cyhalothrin, respectively. No significant association was observed in the triple mutation genotypes with the Ae. aegypti population exposed to 3.20% permethrin and 0.20% deltamethrin resistance (P > 0.05), except for Ae. aegypti from Gengma County when exposed to 0.08% lambda-cyhalothrin (OR 2.86; 95% CI 1.20-6.81; P = 0.02). CONCLUSIONS: Aedes aegypti from Ruili and Gengma counties have developed resistance to various pyrethroid insecticides. The occurrence of multiple mutant sites in VGSC strongly correlated with the high levels of resistance to pyrethroids in the Ae. aegypti populations, highlighting the need for alternative strategies to manage the spread of resistance. A region-specific control strategy for dengue vectors needs to be implemented in the future based on the status of insecticide resistance and kdr mutations.


Assuntos
Aedes , Dengue , Inseticidas , Nitrilas , Piretrinas , Canais de Sódio Disparados por Voltagem , Animais , Inseticidas/farmacologia , Aedes/genética , Permetrina , Mianmar , China/epidemiologia , Piretrinas/farmacologia , Mutação , Resistência a Inseticidas/genética , Canais de Sódio Disparados por Voltagem/genética , Dengue/epidemiologia , Dengue/prevenção & controle , Surtos de Doenças , Mosquitos Vetores/genética
20.
PLoS Negl Trop Dis ; 18(2): e0011595, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38377131

RESUMO

Insecticide resistance is a serious threat to our ability to control mosquito vectors which transmit pathogens including malaria parasites and arboviruses. Understanding the underlying mechanisms is an essential first step in tackling the challenges presented by resistance. This study aimed to functionally characterise the carboxylesterase, CCEae3A, the elevated expression of which has been implicated in temephos resistance in Aedes aegypti and Aedes albopictus larvae. Using our GAL4/UAS expression system, already established in insecticide-sensitive Anopheles gambiae mosquitoes, we produced transgenic An. gambiae mosquitoes that express an Ae. aegypti CCEae3A ubiquitously. This new transgenic line permits examination of CCEae3A expression in a background in which there is not a clear orthologue in Vectorbase and allows comparison with existing An. gambiae GAL4-UAS lines. Insecticide resistance profiling of these transgenic An. gambiae larvae indicated significant increases in resistance ratio for three organophosphate insecticides, temephos (6), chloropyriphos (6.6) and fenthion (3.2) when compared to the parental strain. Cross resistance to adulticides from three major insecticide classes: organophosphates (malathion, fenitrothion and pirimiphos methyl), carbamates (bendiocarb and propoxur) and pyrethroid (alpha-cypermethrin) was also detected. Resistance to certain organophosphates and carbamates validates conclusions drawn from previous expression and phenotypic data. However, detection of resistance to pirimiphos methyl and alphacypermethrin has not previously been formally associated with CCEae3A, despite occurring in Ae. aegypti strains where this gene was upregulated. Our findings highlight the importance of characterising individual resistance mechanisms, thereby ensuring accurate information is used to guide future vector control strategies.


Assuntos
Aedes , Inseticidas , Compostos Organotiofosforados , Piretrinas , Animais , Aedes/genética , Carbamatos , Inseticidas/farmacologia , Organofosfatos/farmacologia , Temefós/farmacologia , Animais Geneticamente Modificados
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...