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1.
Rev Bras Parasitol Vet ; 28(4): 802-806, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31691737

RESUMO

Population explosions of the stable fly (Stomoxys calcitrans) have become a serious concern for livestock producers near sugarcane mills in some regions of Brazil due to the insect's massive reproduction on sugarcane byproducts and waste. Despite the limited efficiency of insecticides for controlling stable fly outbreaks, producers still rely on chemical control to mitigate the alarming infestations in affected areas. This study evaluated the susceptibility of S. calcitrans populations to cypermethrin in the state of Mato Grosso do Sul, Brazil. Stable flies were tested from three field populations and two colonies, established from flies previously collected at sugarcane mills. Wild flies were collected with Nzi traps in areas of sugarcane plantations. Both wild and colonized flies were exposed to eleven concentrations of cypermethrin in impregnated filter paper bioassays. All the populations proved to be resistant to cypermethrin, with resistance factors among field populations ranging from 6.8 to 38.6. The intensive use of insecticides has led to the development of pyrethroid resistance in stable fly populations in the proximities of sugarcane mills in the state of Mato Grosso do Sul.


Assuntos
Inseticidas/farmacologia , Muscidae/efeitos dos fármacos , Piretrinas/farmacologia , Animais , Bioensaio , Brasil , Resistência a Inseticidas , Dose Letal Mediana
2.
Pestic Biochem Physiol ; 160: 119-126, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31519246

RESUMO

Aedes aegypti thrives in urban environments and transmits several debilitating human viral diseases. Thus, our ability to control this mosquito species in endemic areas is of utmost importance. The use of insecticides, mostly pyrethroids and organophosphates (OPs), has long been the primary means of controlling A. aegypti, but widespread insecticide resistance has emerged. The two main mechanisms of pyrethroid resistance in A. aegypti are CYP-mediated detoxification and mutations in the target site, voltage-sensitive sodium channel (Vssc), referred to as knockdown resistance (kdr). Knowledge about the contributions and interactions of these mechanisms to resistance is important for the understanding of the molecular and evolutionary basis of insecticide resistance, and to determine the effectiveness of insecticides. In this study, we address two aims: 1) determine the patterns of CYP-mediated cross-resistance to pyrethroid and OP insecticides, both in the presence and absence of kdr (S989P + V1016G), and 2) determine whether the interaction between the two mechanisms yields a greater than, less than, or additive effect on resistance. We tested seven pyrethroids and four OPs against three congenic strains of A. aegypti: ROCK (susceptible), CYP:ROCK (CR) (resistant due to CYP-mediated detoxification without kdr), and CYP + KDR:ROCK (CKR) (resistant due to both CYPs and kdr), and compared these to the congenic KDR:ROCK strain that was previously reported. We found that resistance ratios (RRs) were variable between pyrethroids and strains, ranging from 6.2- to 42-fold for CR, and 70- to 261-fold for CKR. In general, we found that CYP-mediated resistance alone contributes less to resistance than kdr. The effect of the combined mechanisms on resistance was significantly greater than additive for all pyrethroids except (1R)-trans-fenfluthrin. CYP-mediated pyrethroid resistance conferred cross-resistance to both methyl paraoxon and fenitrothion, and negative cross-resistance to methyl parathion and naled. Based on our results, we recommend that etofenprox and cyfluthrin be avoided for A. aegypti control in areas where these two resistance mechanisms are prevalent.


Assuntos
Aedes/efeitos dos fármacos , Sistema Enzimático do Citocromo P-450/metabolismo , Organofosfatos/farmacologia , Piretrinas/farmacologia , Animais , Feminino , Técnicas de Silenciamento de Genes , Resistência a Inseticidas/genética , Masculino , Mutação
3.
Pestic Biochem Physiol ; 160: 127-135, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31519247

RESUMO

Environmental xenobiotics can influence the tolerance of insects to chemical insecticides. Heavy metals are widespread distributed, can be easily bio-accumulated in plants and subsequently within phytophagous insects via the food chains. However, less attention has been paid to the effect of heavy metal exposure on their insecticide tolerance. In this study, pre-exposure of copper (Cu, 25-100 mg kg-1) significantly enhanced the subsequent tolerance of Spodoptera litura to ß-cypermethrin, a widely used pyrethroid insecticide in crop field. Cytochrome P450 monooxygenases (CYPs) activities were cross-induced in larvae exposed to Cu and ß-cypermethrin, while the activities of glutathione S-transferase (GST) and carboxylesterase (CarE) were not affected. Application of piperonyl butoxide (PBO), a P450 synergist, effectively impaired the tolerance to ß-cypermethrin in Cu-exposed S. litura larvae with a synergistic ratio of 1.72, indicating that P450s contribute to larval tolerance to ß-cypermethrin induced by Cu exposure. Among the four CYP6AB family genes examined, only larval midgut-specific CYP6AB12 was found to be cross-induced by Cu and ß-cypermethrin. RNA interference (RNAi)-mediated silencing of CYP6AB12 effectively decreased the mRNA levels of the target gene, and significantly reduced the larval tolerance to ß-cypermethrin following exposure to Cu. These results showed that pre-exposure of heavy metal Cu enhanced larval tolerance to ß-cypermethrin in S. litura, possibly through the cross-induction of P450s. Our findings provide new insights on the relationship between heavy metals and chemical insecticides that may benefit both the risk evaluation of heavy metal contamination and development of pest management strategies.


Assuntos
Cobre/farmacologia , Inseticidas/farmacologia , Larva/efeitos dos fármacos , Piretrinas/farmacologia , Spodoptera/efeitos dos fármacos , Animais , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Interferência de RNA , Spodoptera/crescimento & desenvolvimento
4.
Pestic Biochem Physiol ; 159: 9-16, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31400789

RESUMO

An L1024F substitution in the para gene, which encodes a subunit of the voltage-gated sodium channel, has been implicated in pyrethroid resistance in a mite pest, Halotydeus destructor, which attacks rape and other grain crops. A high-resolution melt (HRM) genotyping assay was developed for testing the relative pyrethroid susceptibility of different para genotypes and for high-throughput field screening of resistant alleles. The L1024F mutation was found to be incompletely recessive in phenotypic laboratory bioassays with the pyrethroid pesticide, bifenthrin. While the resistance ratio of heterozygotes (RS) to susceptible homozygotes (SS) was <6 in 24 h bioassays, the resistant homozygotes (RR) (with a resistance ratio > 200,000) survived the recommended field rate of bifenthrin (100 mgL-1). HRM genotyping of mites from field populations across Australia indicated the presence of resistant alleles in Western Australia and South Australia, but not in Victoria and New South Wales. The assay developed will be useful for routine screening of pyrethroid resistance, and the dominance relationships established here point to useful resistance management strategies involving the maintenance of reservoirs of susceptible mites to dilute resistant homozygotes in a population.


Assuntos
Inseticidas/farmacologia , Ácaros/efeitos dos fármacos , Piretrinas/farmacologia , Animais , Genótipo , Heterozigoto , Homozigoto , Resistência a Inseticidas/genética , Programas de Rastreamento , Ácaros/genética
6.
Chem Biol Interact ; 311: 108796, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31421116

RESUMO

Lambda-cyhalothrin (LCT) is a broad-spectrum pesticide widely used in agriculture throughout the world. This pesticide is considered a potential contaminant of surface and underground water as well as food, posing a risk to ecosystems and humans. In this sense, we decided to evaluate the activity of enzymes belonging to the purinergic system, which is linked with regulation of extracellular nucleotides and nucleosides, such as adenosine triphosphate (ATP) and adenosine (Ado) molecules involved in the regulation of inflammatory response. However, there are no data concerning the effects of LCT exposure on the purinergic system, where extracellular nucleotides act as signaling molecules. The aim of this study was to evaluate nucleotide hydrolysis by E-NTPDase (ecto-nucleoside triphosphate diphosphohydrolase), Ecto-NPP (ecto-nucleotide pyrophosphatase/phosphodiesterase), ecto-5'-nucleotidase and ecto-adenosine deaminase (E-ADA) in platelets and liver of adult rats on days 7, 30, 45 and 60 after daily gavage with 6.2 and 31.1 mg/kg bw of LCT. Gene expression patterns of NTPDases1-3 and 5'-nucleotidase were also determined in those tissues. In parallel, lambda-cyhalothrin metabolites [3-(2-chloro-3,3,3- trifluoroprop-1-enyl)-2,2-dimethyl-cyclopropane carboxylic acid (CFMP), 4-hydroxyphenoxybenzoic acid (4-OH-3-PBA), and 3-phenoxybenzoic acid (3-PBA)] were measured in plasma. Results showed that exposure rats to LCT caused a significant increase in the assessed enzymes activities. Gene expression pattern of ectonucleotidases further revealed a significant increase in E-NTPDase1, E-NTPDase2, and E-NTPDase3 mRNA levels after LCT administration at all times. A dose-dependent increase in LCT metabolite levels was also observed but there no significant variations in levels from weeks to week, suggesting steady-steady equilibrium. Correlation analyses revealed that LCT metabolites in the liver and plasma were positively correlated with the adenine nucleotides hydrolyzing enzyme, E-ADA and E-NPP activities in platelets and liver of rats exposed to lambda-cyhalothin. Our results show that LCT and its metabolites may affect purinergic enzymatic cascade and cause alterations in energy metabolism.


Assuntos
Plaquetas/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Fígado/efeitos dos fármacos , Nitrilos/farmacologia , Nucleotidases/genética , Nucleosídeos de Purina/metabolismo , Piretrinas/farmacologia , Adenosina Desaminase/genética , Adenosina Desaminase/metabolismo , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Animais , Plaquetas/enzimologia , Plaquetas/metabolismo , Cromatografia Líquida de Alta Pressão , Hidrólise , Fígado/enzimologia , Fígado/metabolismo , Masculino , Espectrometria de Massas , Nitrilos/sangue , Nitrilos/metabolismo , Nucleotidases/metabolismo , Piretrinas/sangue , Piretrinas/metabolismo , Pirofosfatases/genética , Pirofosfatases/metabolismo , Ratos , Ratos Wistar
7.
Pestic Biochem Physiol ; 158: 77-87, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31378364

RESUMO

Pyrethroid-resistance in onion thrips, Thrips tabaci, has been reported in many countries including Japan. Identifying factors of the resistance is important to correctly monitoring the resistance in field populations. To identify pyrethroid-resistance related genes in T. tabaci in Japan, we performed RNA-Seq analysis of seven T. tabaci strains including two pyrethroid-resistant and five pyrethroid-susceptible strains. We identified a pair of single point mutations, T929I and K1774N, introducing two amino acid mutations, in the voltage-gated sodium channel gene, a pyrethroid target gene, in the two resistant strains. The K1774N is a newly identified mutation located in the fourth repeat domain of the sodium channel. Genotyping analysis of field-collected populations showed that most of the T. tabaci individuals in resistant populations carried the mutation pair, indicating that the mutation pair is closely associated with pyrethroid-resistance in Japan. Another resistance-related mutation, M918L, was also identified in part of the resistant populations. Most of the individuals with the mutation pair were arrhenotokous while all individuals with the M918L single mutation were thelytokous. The result of differentially expressed gene analysis revealed a small number of up-regulated detoxification genes in each resistant strain which might be involved in resistance to pyrethroid. However, no up-regulated detoxification genes common to the two resistant strains were detected. Our results indicate that the mutation pair in the sodium channel gene is the most important target for monitoring pyrethroid-resistance in T. tabaci, and that pyrethroid-resistant arrhenotokous individuals with the mutation pair are likely to be widely distributed in Japan.


Assuntos
Piretrinas/farmacologia , Tisanópteros/efeitos dos fármacos , Tisanópteros/metabolismo , Canais de Sódio Disparados por Voltagem/metabolismo , Animais , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Japão , Mutação/genética , Mutação Puntual/genética , Tisanópteros/genética , Canais de Sódio Disparados por Voltagem/genética
8.
Parasitol Res ; 118(9): 2499-2507, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31363921

RESUMO

Stable flies (Stomoxys calcitrans Linnaeus, 1758) can have a considerable negative impact on animal well-being, health, and productivity. Since insecticides constitute the mainstay for their control, this study aimed at assessing the occurrence of insecticide resistance in S. calcitrans on dairy farms in Brandenburg, Germany. First, the susceptibility of stable flies from 40 dairy farms to a deltamethrin-impregnated fabric was evaluated using the FlyBox® field test method. Then, S. calcitrans strains from 10 farms were reared in the laboratory, and the offspring was tested against the adulticides deltamethrin and azamethiphos and the larvicides cyromazine and pyriproxyfen. The FlyBox® method indicated 100% resistance in stable flies against deltamethrin. Later, to the offspring of those 10 established laboratory strains previously caught on suspected dairy farms, these field findings could be confirmed with mortalities well below 90% 24 h following topical application of the calculated LD95 of deltamethrin and azamethiphos. The ten strains could therefore be classified as resistant to the tested insecticides. In contrast, exposure to the insect growth regulators cyromazine and pyriproxyfen at their recommended concentrations demonstrated 100% efficacy. Both larvicides inhibited the moulting process of the stable fly larval stages completely, showing that the stable fly strains tested were susceptible to them. The intensive use of insecticides in recent decades has probably promoted the development of insecticide resistance. Systematic surveys in different livestock production systems and vigilance are therefore deemed necessary for estimating the risk of insecticide resistance development on a nationwide scale.


Assuntos
Resistência a Inseticidas/fisiologia , Inseticidas/farmacologia , Hormônios Juvenis/farmacologia , Larva/efeitos dos fármacos , Muscidae/efeitos dos fármacos , Animais , Fazendas , Alemanha , Nitrilos/farmacologia , Organotiofosfatos/farmacologia , Piretrinas/farmacologia , Piridinas/farmacologia , Triazinas/farmacologia
9.
Malar J ; 18(1): 224, 2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31272452

RESUMO

BACKGROUND: PermaNet® 3.0 is a deltamethrin-treated combination long-lasting insecticidal net with the addition of synergist piperonylbutoxide (PBO) on its roof section. It is designed to overcome the challenge posed by pyrethroid resistant vector populations against mainstream long-lasting insecticidal nets impregnated with pyrethroids only. The objective of this study was to determine insecticide resistance status of Anopheline and Culicine mosquitoes, to evaluate the bio-efficacy of PermaNet® 3.0 nets and to assess household factors affecting the physical integrity of PermaNet® 3.0 after 3 years of use. METHODS: Insecticide susceptibility test was conducted using the WHO tube test. Bio-activity of PermaNet® 3.0 samples was evaluated using the WHO cone bioassay. Cross-sectional survey was conducted on 150 randomly selected households from two districts to determine household factors affecting net utilization. One hundred fifty PermaNet® 3.0 nets were randomly collected from the community with replacement after 3 years of deployment and physical integrity of each net was assessed. RESULTS: Both Anopheles gambiae sensu lato and Culex quinquefasciatus developed resistance against permethrin and deltamethrin. However, following pre-exposure to synergist PBO the susceptibility of mosquito population increased to both permethrin (from 39% without to 92% with PBO against An. gambiae and from 28% without to 94% with PBO against Culex quinquefasciatus) and deltamethrin (from 52% without to 99% with PBO against An. gambiae and from 43% without to 98% with PBO against Culex quinquefasciatus). Eighty percent (80%) mortality was recorded in wild population of An. gambiae s.l. exposed to unused PermaNet® 3.0, but its bioactivity subsequently declined as washing frequency increased from 0 to 20. The PBO coated roof section of unused PermaNet® 3.0 resulted in higher mosquito mortality (100%) compared to the side panels without PBO (85%). House structure, cooking and washing habits, and damage due to household pests were cited as determinants associated with bed net deterioration. Bed net proportionate hole index (pHI) was ranged from 0 to 6064. Of the 150 PermaNet® 3.0 nets assessed 80, 29 and 41 were considered as 'good', 'acceptable' and 'too torn', respectively. CONCLUSIONS: The bio-efficacy evaluation of PermaNet® 3.0 from Jimma area, southwestern Ethiopia showed moderate efficacy against pyrethroid resistant population of An. gambiae and Culex quinquefasciatus. Thus, NMCPs in parallel to deployment of LLINs, should implement timely insecticide resistance management and integrated vector management strategies to slowdown the evolution and further spread of insecticide resistance. Household factors such as, housing conditions, open flame fire used for cooking and rodent attack were identified as factors contributing to the observed reduced bed net physical integrity in the study area. Universal coverage of bed nets should be accompanied with community awareness creation and training on net utilization and handling.


Assuntos
Anopheles/efeitos dos fármacos , Culex/efeitos dos fármacos , Resistência a Inseticidas , Mosquiteiros Tratados com Inseticida/estatística & dados numéricos , Controle de Mosquitos/instrumentação , Mosquitos Vetores/efeitos dos fármacos , Butóxido de Piperonila/farmacologia , Animais , Etiópia , Feminino , Inseticidas/farmacologia , Malária/prevenção & controle , Nitrilos/farmacologia , Permetrina/farmacologia , Piretrinas/farmacologia
10.
Parasit Vectors ; 12(1): 333, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31269965

RESUMO

BACKGROUND: Aedes aegypti and Ae. albopictus are important vectors of infectious diseases, especially those caused by arboviruses such as dengue, chikungunya and Zika. Aedes aegypti is very well adapted to urban environments, whereas Ae. albopictus inhabits more rural settings. Pyrethroid resistance is widespread in these vectors, but limited data exist from the Southwest Pacific Region, especially from Melanesia. While Aedes vector ecology is well documented in Australia, where incursion of Ae. albopictus and pyrethroid resistance have so far been prevented, almost nothing is known about Aedes populations in neighbouring Papua New Guinea (PNG). With pyrethroid resistance documented in parts of Indonesia but not in Australia, it is important to determine the distribution of susceptible and resistant Aedes populations in this region. METHODS: The present study was aimed at assessing Aedes populations for insecticide resistance in Madang and Port Moresby, located on the north and south coasts of PNG, respectively. Mosquitoes were collected using ovitraps and reared in an insectary. Standard WHO bioassays using insecticide-treated filter papers were conducted on a total of 253 Ae. aegypti and 768 Ae. albopictus adult mosquitoes. Subsets of samples from both species (55 Ae. aegypti and 48 Ae. albopictus) were screened for knockdown resistance mutations in the voltage-sensitive sodium channel (Vssc) gene, the target site of pyrethroid insecticides. RESULTS: High levels of resistance against pyrethroids were identified in Ae. aegypti from Madang and Port Moresby. Aedes albopictus exhibited susceptibility to pyrethroids, but moderate levels of resistance to DDT. Mutations associated with pyrethroid resistance were detected in all Ae. aegypti samples screened. Some genotypes found in the present study had been observed previously in Indonesia. No Vssc mutations associated with pyrethroid resistance were found in the Ae. albopictus samples. CONCLUSIONS: To our knowledge, this is the first report of pyrethroid resistance in Ae. aegypti mosquitoes in PNG. Interestingly, usage of insecticides in PNG is low, apart from long-lasting insecticidal nets distributed for malaria control. Further investigations on how these resistant Ae. aegypti mosquito populations arose in PNG and how they are being sustained are warranted.


Assuntos
Aedes/efeitos dos fármacos , Febre de Chikungunya/transmissão , Dengue/transmissão , Resistência a Inseticidas , Mosquitos Vetores/efeitos dos fármacos , Infecção por Zika virus/transmissão , Aedes/virologia , Animais , Arbovirus/fisiologia , Feminino , Inseticidas/farmacologia , Mosquitos Vetores/virologia , Papua Nova Guiné , Piretrinas/farmacologia
11.
Parasit Vectors ; 12(1): 337, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31287014

RESUMO

BACKGROUND: Aedes aegypti were found developing in the water in open public drains (drain-water, DW) in Jaffna city in northern Sri Lanka, a location where the arboviral diseases dengue and chikungunya are endemic. METHODS: Susceptibilities to the common insecticides dichlorodiphenyltrichloroethane (DDT), malathion, propoxur, permethrin and deltamethrin and activities of the insecticide-detoxifying enzymes carboxylesterase (EST), glutathione S-transferase (GST) and monooxygenase (MO) were compared in adult Ae. aegypti developing in DW and fresh water (FW). RESULTS: DW Ae. aegypti were resistant to the pyrethroids deltamethrin and permethrin, while FW Ae. aegypti were susceptible to deltamethrin but possibly resistant to permethrin. Both DW and FW Ae. aegypti were resistant to DDT, malathion and propoxur. Greater pyrethroid resistance in DW Ae. aegypti was consistent with higher GST and MO activities. CONCLUSIONS: The results demonstrate the potential for insecticide resistance developing in Ae. aegypti adapted to DW. Urbanization in arboviral disease-endemic countries is characterized by a proliferation of open water drains and therefore the findings identify a potential new challenge to global health.


Assuntos
Aedes/enzimologia , Arbovirus/fisiologia , Resistência a Inseticidas , Mosquitos Vetores/enzimologia , Águas Residuárias/parasitologia , Aedes/efeitos dos fármacos , Aedes/virologia , Animais , Carboxilesterase/metabolismo , DDT/farmacologia , Feminino , Saúde Global , Glutationa Transferase/metabolismo , Humanos , Inseticidas/farmacologia , Malation/farmacologia , Masculino , Camundongos , Oxigenases de Função Mista/metabolismo , Mosquitos Vetores/efeitos dos fármacos , Mosquitos Vetores/virologia , Nitrilos/farmacologia , Permetrina/farmacologia , Propoxur/farmacologia , Piretrinas/farmacologia
12.
Malar J ; 18(1): 243, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31315614

RESUMO

BACKGROUND: Malaria vector control is dependent on chemical insecticides applied to walls by indoor residual spraying or on long-lasting insecticidal nets. The emergence and spread of insecticide resistance in major malaria vectors may compromise malaria control and elimination efforts. The aim of this study was to estimate a diagnostic dose for chlorfenapyr (class: pyrrole) and clothianidin (class: neonicotinoid) and assess the baseline susceptibility of three major Anopheles malaria vectors of western Kenya to these two insecticides. METHODS: The Centers for Disease Control and Prevention (CDC) bottle assay was used to determine the diagnostic doses of chlorfenapyr and clothianidin insecticides against the susceptible Kisumu strain of Anopheles gambiae. Probit analysis was used to determine the lethal doses at which 50% (LD50) and 99% (LD99) of the susceptible mosquitoes would be killed 24, 48 and 72 h following exposure for 1 h. Insecticidal efficacy of chlorfenapyr, clothianidin and the pyrethroid deltamethrin was then evaluated against field collected female Anopheles mosquitoes sampled from Nyando, Bumula and Ndhiwa sub-Counties in western Kenya. Members of Anopheles funestus and An. gambiae complexes were identified using polymerase chain reaction (PCR). RESULTS: The determined diagnostic doses of chlorfenapyr and clothianidin insecticides were 50 µg/bottle and 150 µg/bottle, respectively, for An. gambiae, Kisumu strain. When exposed to the diagnostic dose of each insecticide, Anopheles malaria vector populations in western Kenya were susceptible to both insecticides with 100% mortality observed after 72 h. Mortality of mosquitoes exposed to deltamethrin increased over time but did not reach 100%. Mortality of Anopheles arabiensis from Nyando exposed to deltamethrin was 83% at 24 h, 88% at 48 h and 94.5% at 72 h while An. funestus from Ndhiwa was 89% at 24 h, 91.5% at 48 h and 94.5% at 72 h. CONCLUSION: Mosquitoes of western Kenya, despite being resistant to pyrethroids, are susceptible to chlorfenapyr and clothianidin. Field evaluations of the formulated product are needed.


Assuntos
Anopheles/efeitos dos fármacos , Guanidinas/farmacologia , Inseticidas/farmacologia , Controle de Mosquitos , Mosquitos Vetores/efeitos dos fármacos , Neonicotinoides/farmacologia , Piretrinas/farmacologia , Tiazóis/farmacologia , Animais , Relação Dose-Resposta a Droga , Quênia , Dose Letal Mediana , Malária/prevenção & controle , Especificidade da Espécie
13.
Parasitol Res ; 118(9): 2485-2497, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31280327

RESUMO

We evaluated the effects of four different 6-year duration control strategies on the resistance levels and frequency of the pyrethroid target site resistance alleles, superkdr (skdr) and kdr, at four field populations of Haematobia irritans irritans (Linnaeus, 1758) (Diptera: Muscidae) in Louisiana, USA. Consecutive use of pyrethroid ear tags for 6 years caused a significant increase in the resistance ratio to pyrethroids as well as the frequencies of both skdr and kdr resistance alleles. After 3 years of consecutive use of pyrethroid ear tags, followed by 1 year with no treatment, and followed by 2 years with organophosphate ear tags, the resistance ratio for pyrethroid was not significantly affected, the %R-skdr significantly dropped while the %R-kdr allele remained relatively high and stable. Similar results were observed when pyrethroid ear tags were used for three consecutive years, followed by 1 year with no treatment, and followed by 2 years with endosulfan ear tags; however, this treatment resulted in a slight increase in the resistance ratio for pyrethroids. In a mosaic, the resistance ratio for pyrethroids showed a 2.5-fold increase but the skdr-kdr genetic profiles did not change, as the %R alleles (skdr and kdr) remained low and stable through the 6 years. Lack of exposure to pyrethroid insecticides for 3 years significantly affected the skdr mutation but not the kdr mutation, preventing re-establishment of susceptibility to pyrethroids. SS-SR (skdr-kdr) individuals were responsible for the maintenance of the kdr mutation in two of the populations studied, and fitness cost seems to strongly affect the SR-RR genotype. None of the four treatment regimens evaluated in the study had satisfactory results for the management of kdr resistance alleles.


Assuntos
Resistência a Inseticidas/genética , Inseticidas/farmacologia , Muscidae/efeitos dos fármacos , Organofosfatos/farmacologia , Piretrinas/farmacologia , Alelos , Animais , Mutação/genética
14.
Trials ; 20(1): 321, 2019 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159887

RESUMO

BACKGROUND: Long-lasting insecticidal nets (LLINs) are a key malaria control intervention, but their effectiveness is threatened by resistance to pyrethroid insecticides. Some new LLINs combine pyrethroids with piperonyl butoxide (PBO), a synergist that can overcome P450-based metabolic resistance to pyrethroids in mosquitoes. In 2017-2018, the Ugandan Ministry of Health distributed LLINs with and without PBO through a national mass-distribution campaign, providing a unique opportunity to rigorously evaluate PBO LLINs across different epidemiological settings. METHODS/DESIGN: Together with the Ministry of Health, we embedded a cluster-randomised trial to evaluate the impact of LLINs delivered in the 2017-2018 national campaign. A total of 104 clusters (health sub-districts) in Eastern and Western Uganda were involved, covering 48 of 121 (40%) districts. Using adaptive randomisation driven by the number of LLINs available, clusters were assigned to receive one of four types of LLINs, including two brands with PBO: 1) PermaNet 3.0 (n = 32) and 2) Olyset Plus (n = 20); and two without PBO: 3) PermaNet 2.0 (n = 37) and 4) Olyset Net (n = 15). We are conducting cross-sectional community surveys in 50 randomly selected households per cluster (5200 households per survey) and entomological surveillance for insecticide resistance in up to 10 randomly selected households enrolled in the community surveys per cluster (1040 households per survey) at baseline and 6, 12, and 18 months after LLIN distribution. Net durability and bio-efficacy will be assessed in 400 nets withdrawn from households with replacement at 12 months. The primary trial outcome is parasite prevalence as measured by microscopy in children aged 2-10 years in the follow-up surveys. DISCUSSION: PBO LLINs are a promising new tool to reduce the impact of pyrethroid resistance on malaria control. The World Health Organization has issued a preliminary endorsement of PBO LLINs, but additional epidemiological evidence of the effect of PBO LLINs is urgently needed. The results of this innovative, large-scale trial embedded within a routine national distribution campaign will make an important contribution to the malaria control policy in Uganda and throughout Africa, where pyrethroid resistance in malaria vectors has increased dramatically. This model of evaluation could be a paradigm for future assessment of malaria control interventions. TRIAL REGISTRATION: ISRCTN, ISRCTN17516395 . Registered on 14 February 2017. WORLD HEALTH ORGANIZATION TRIAL REGISTRATION DATA SET: See Additional file 1.


Assuntos
Mosquiteiros Tratados com Inseticida , Malária/prevenção & controle , Butóxido de Piperonila/farmacologia , Ensaios Clínicos Controlados Aleatórios como Assunto , Criança , Pré-Escolar , Análise por Conglomerados , Estudos Transversais , Humanos , Resistência a Inseticidas , Piretrinas/farmacologia , Uganda
15.
PLoS Negl Trop Dis ; 13(6): e0007432, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31158225

RESUMO

BACKGROUND: Multiple mutations in the voltage-gated sodium channel have been associated with knockdown resistance (kdr) to DDT and pyrethroid insecticides in a major human disease vector Aedes aegypti. One mutation, V1016G, confers sodium channel resistance to pyrethroids, but a different substitution in the same position V1016I alone had no effect. In pyrethroid-resistant Ae. aegypti populations, V1016I is often linked to another mutation, F1534C, which confers sodium channel resistance only to Type I pyrethroids including permethrin (PMT), but not to Type II pyrethroids including deltamethrin (DMT). Mosquitoes carrying both V1016G and F1534C exhibited a greater level of pyrethroid resistance than those carrying F1534C alone. More recently, a new mutation T1520I co-existing with F1534C was detected in India. However, whether V1016I or T1520I enhances pyrethroid resistance of sodium channels carrying F1534C remains unknown. METHODOLOGY/PRINCIPAL FINDINGS: V1016I, V1016G, T1520I and F1534C substitutions were introduced alone and in various combinations into AaNav1-1, a sodium channel from Aedes aegypti. The mutant channels were then expressed in Xenopus oocytes and examined for channel properties and sensitivity to pyrethroids using the two-electrode voltage clamping technique. The results showed that V1016I or T1520I alone did not alter the AaNav1-1 sensitivity to PMT or DMT. However, the double mutant T1520I+F1534C was more resistant to PMT than F1534C, but remained sensitive to DMT. In contrast, the double mutant V1016I+F1534C was resistant to DMT and more resistant to PMT than F1534C. Furthermore, V1016I/G and F1534C channels, but not T1520I, were resistant to dichlorodiphenyltrichloroethane (DDT). Cryo-EM structures of sodium channels suggest that T1520I allosterically deforms geometry of the pyrethroid receptor site PyR1 in AaNav1-1. The small deformation does not affect binding of DDT, PMT or DMT, but in combination with F1534C it increases the channel resistance to PMT and DDT. CONCLUSIONS/SIGNIFICANCE: Our data corroborated the previously proposed sequential selection of kdr mutations in Ae. aegypti. We proposed that mutation F1534C first emerged in response to DDT/pyrethroids providing a platform for subsequent selection of mutations V1016I and T1520I that confer greater and broader spectrum of pyrethroid resistance.


Assuntos
Aedes/genética , DDT/farmacologia , Evolução Molecular , Resistência a Inseticidas , Inseticidas/farmacologia , Piretrinas/farmacologia , Canais de Sódio/genética , Aedes/efeitos dos fármacos , Substituição de Aminoácidos , Animais , Células Cultivadas , Expressão Gênica , Mosquitos Vetores/efeitos dos fármacos , Mosquitos Vetores/genética , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Mutação de Sentido Incorreto , Canais de Sódio/metabolismo , Xenopus
16.
Pestic Biochem Physiol ; 157: 1-12, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153457

RESUMO

The use of neurotoxic chemical insecticides has led to consequences against the environment, insect resistances and side-effects on non-target organisms. In this context, we developed a novel strategy to optimize insecticide efficacy while reducing doses. It is based on nanoencapsulation of a pyrethroid insecticide, deltamethrin, used as synergistic agent, combined with a non-encapsulated oxadiazine (indoxacarb). In this case, the synergistic agent is used to increase insecticide efficacy by activation of calcium-dependant intracellular signaling pathways involved in the regulation of the membrane target of insecticides. In contrast to permethrin (pyrethroid type I), we report that deltamethrin (pyrethroid type II) produces an increase in intracellular calcium concentration in insect neurons through the reverse Na/Ca exchanger. The resulting intracellular calcium rise rendered voltage-gated sodium channels more sensitive to lower concentration of the indoxacarb metabolite DCJW. Based on these findings, in vivo studies were performed on the cockroach Periplaneta americana and mortality rates were measured at 24 h, 48 h and 72 h after treatments. Comparative studies of the toxicity between indoxacarb alone and indoxacarb combined with deltamethrin or nanoencapsulated deltamethrin (LNC-deltamethrin), indicated that LNC-deltamethrin potentiated the effect of indoxacarb. We also demonstrated that nanoencapsulation protected deltamethrin from esterase-induced enzymatic degradation and led to optimize indoxacarb efficacy while reducing doses. Moreover, our results clearly showed the benefit of using LNC-deltamethrin rather than piperonyl butoxide and deltamethrin in combination commonly used in formulation. This innovative strategy offers promise for increasing insecticide efficacy while reducing both doses and side effects on non-target organisms.


Assuntos
Cálcio/metabolismo , Inseticidas/química , Inseticidas/farmacologia , Nanocápsulas/química , Nitrilos/química , Nitrilos/farmacologia , Oxazinas/química , Oxazinas/farmacologia , Piretrinas/química , Piretrinas/farmacologia , Animais , Células Cultivadas , Baratas , Masculino , Estrutura Molecular , Periplaneta/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismo
17.
Pestic Biochem Physiol ; 157: 196-203, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153469

RESUMO

Overexpression of the cytochrome P450 monooxygenase CYP6A51 has been previously associated with pyrethroid resistance in the Mediterranean fruit fly (medfly) Ceratitis capitata, an important pest species worldwide; however, this association has not been functionally validated. We expressed CYP6A51 gene in Escherichia coli and produced a functional enzyme with preference for the chemiluminescent substrate Luciferin-ME EGE. In vitro metabolism assays revealed that CYP6A51 is capable of metabolizing two insecticides that share the same mode of action, λ-cyhalothrin and deltamethrin, whereas no metabolism or substrate depletion was observed in the presence of spinosad or malathion. We further expressed CYP6A51 in vivo via a GAL4/UAS system in Drosophila melanogaster flies, driving expression with detoxification tissue-specific drivers. Toxicity bioassays indicated that CYP6A51 confers knock-down resistance to both λ-cyhalothrin and deltamethrin. Detection of CYP6A51 - associated pyrethroid resistance in field populations may be important for efficient Insecticide Resistance Management (IRM) strategies.


Assuntos
Ceratitis capitata/efeitos dos fármacos , Ceratitis capitata/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Piretrinas/farmacologia , Animais , Sistema Enzimático do Citocromo P-450/genética , Família 6 do Citocromo P450/genética , Família 6 do Citocromo P450/metabolismo , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Inseticidas/farmacologia , Nitrilos/farmacologia
18.
Pestic Biochem Physiol ; 157: 204-210, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153470

RESUMO

Sulfoxaflor is the first commercially available sulfoximine insecticide, which exhibits highly efficacy against many sap-feeding insect pests and has been applied as an alternative insecticide against cotton aphid in China. This study was conducted to investigate the risk of resistance development, the cross-resistance pattern and the potential resistance mechanisms of sulfoxaflor in Aphis gossypii. A colony (SulR strain) of A. gossypii with 245-fold resistance, originated from Xinjiang field population, was established by continuous selection using sulfoxaflor. The SulR strain has developed cross-resistance to imidacloprid (80.8-fold), acetamiprid (19.3-fold), thiamethoxam (10.0-fold), and flupyradifurone (107.5-fold), while no cross-resistance was detected to malathion, omethoate, bifenthrin, methomyl, and carbosulfan. Piperonyl butoxide and S, S, S-tributyl phosphorotrithioate could significantly increase the toxicity of sulfoxaflor to the SulR strain by 5.99- and 4.18-fold, respectively, whereas no synergistic effect with diethyl maleate was observed. The activities of P450s and carboxylesterase were significantly higher in the SulR strain than that in the SS strain. Further gene expression determination demonstrated that nine P450 genes were significantly increased in SulR strain and suppression the expression of CYP6CY13 and CYP6CY19 by RNAi significantly increased the susceptibility of SulR adult aphids to sulfoxaflor. These results demonstrated that the enhancing detoxification by cytochrome P450 monooxygenase may be involved in A.gossypii resistance to sulfoxaflor.


Assuntos
Afídeos/efeitos dos fármacos , Sistema Enzimático do Citocromo P-450/metabolismo , Piridinas/farmacologia , Compostos de Enxofre/farmacologia , 4-Butirolactona/análogos & derivados , 4-Butirolactona/farmacologia , Animais , Afídeos/genética , Afídeos/metabolismo , Sistema Enzimático do Citocromo P-450/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Neonicotinoides/farmacologia , Nitrocompostos/farmacologia , Piretrinas/farmacologia
19.
Pestic Biochem Physiol ; 157: 26-32, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153474

RESUMO

Nitenpyram is very effective in controlling Nilaparvata lugens (brown planthopper, BPH), and its resistance has been reported in field populations; however, the resistance mechanism remains unclear. In the present study, cross-resistance and resistance mechanisms in nitenpyram-resistant BPH were investigated. A resistant strain (NR) with a high resistance level (164.18-fold) to nitenpyram was evolved through successive selection for 42 generations from a laboratory susceptible strain (NS). The bioassay results showed that the NR exhibited cross-resistance to imidacloprid (37.46-fold), thiamethoxam (71.66-fold), clothianidin (149.17-fold), dinotefuran (98.13-fold), sulfoxaflor (47.24-fold), cycloxaprid (9.33-fold), etofenprox (10.51-fold) and isoprocarb (9.97-fold) but not to triflumezopyrim, chlorpyrifos and buprofezin. The NR showed a 3.21-fold increase in cytochrome P450 monooxygenase (P450) activity compared to that in the NS, while resistance was also synergized (4.03-fold) with the inhibitor piperonyl butoxide (PBO), suggesting a role of P450. Furthermore, the mRNA expression levels of cytochrome P450 (CYP) genes by quantitative real-time PCR results indicated that twelve P450 genes were significantly overexpressed in the NR strain, especially CYP6ER1 (203.22-fold). RNA interference (RNAi) suppression of CYP6ER1 through injection of dsCYP6ER1 led to significant susceptibility in the NR strain. The current study expands our understanding of the nitenpyram resistance mechanism in N. lugens, provides an important reference for integrated pest management (IPM), and enriches the theoretical system of insect toxicology.


Assuntos
Hemípteros/efeitos dos fármacos , Neonicotinoides/farmacologia , Animais , Carbamatos/farmacologia , Guanidinas/farmacologia , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Resistência a Inseticidas , Nitrocompostos/farmacologia , Piretrinas/farmacologia , Piridinas/farmacologia , Pirimidinonas/farmacologia , Interferência de RNA , Tiazóis/farmacologia
20.
Pestic Biochem Physiol ; 157: 69-79, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153479

RESUMO

Carboxylesterases (CarEs) are a major class of detoxification enzymes involved in insecticide resistance in various insect species. In this study, a novel CarE 001G was isolated from the cotton bollworm Helicoverpa armigera, one of the most destructive agricultural insect pests. The open reading frame of 001G has 2244 nucleotides and putatively encodes 747 amino acid residues. The deduced CarE possessed the highly conserved catalytic triads(Ser-Glu-His) and pentapeptide motifs (Gly-X-Ser-X-Gly), suggesting 001G is biologically active. The truncated 001G was successfully expressed in Escherichia coli, and the recombinant proteins were purified and tested. The enzyme kinetic assay showed the purified proteins could catalyze two model substrates, α-naphthyl acetate and ß-naphthyl acetate, with a kcat of 8.8 and 2.3 s-1, a Km of 9.6 and 16.2 µM, respectively. The inhibition study with pyrethroid, organophosphate and neonicotinoid insecticides showed different inhibition profile against the purified CarE. The HPLC assay demonstrated that the purified proteins were able to metabolize ß-cypermethrin, λ-cyhalothrin and fenvalerate insecticides, exhibiting respective specific activities of 1.7, 1.4 and 0.5 nM/min/mg protein. However, the purified proteins were not able to metabolize the chlorpyrifos, parathion-methyl, paraoxon-ethyl and imidacloprid. The modeling and docking analyses consistently demonstrated that the pyrethroid molecule fits snugly into the catalytic pocket of the CarE 001G. Collectively, our results suggest that 001G may play a role in pyrethroids detoxification in H. armigera.


Assuntos
Carboxilesterase/metabolismo , Inseticidas/metabolismo , Inseticidas/farmacologia , Mariposas/enzimologia , Mariposas/metabolismo , Animais , Carboxilesterase/genética , Mariposas/efeitos dos fármacos , Nitrilos/metabolismo , Nitrilos/farmacologia , Piretrinas/metabolismo , Piretrinas/farmacologia
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