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1.
PLoS One ; 15(10): e0228695, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33022007

RESUMO

Aedes aegypti is the main vector of dengue, chikungunya, and Zika viruses, which are of great public health importance in Colombia. Aedes control strategies in Colombia rely heavily on the use of organophosphate and pyrethroid insecticides, providing constant selection pressure and the emergence of resistant populations. In recent years, insecticide use has increased due to the increased incidence of dengue and recent introductions of chikungunya and Zika. In the present study, pyrethroid resistance was studied across six populations of Ae. aegypti from the Caribbean coast of Colombia. Susceptibility to λ-cyhalothrin, deltamethrin, and permethrin was assessed, and resistance intensity was determined. Activity levels of enzymes associated with resistance were measured, and the frequencies of three kdr alleles (V1016I, F1534C, V410L) were calculated. Results showed variations in pyrethroid susceptibility across Ae. aegypti populations and altered enzyme activity levels were detected. The kdr alleles were detected in all populations, with high variations in frequencies: V1016I (frequency ranging from 0.15-0.70), F1534C (range 0.94-1.00), and V410L (range 0.05-0.72). In assays of phenotyped individuals, associations were observed between the presence of V1016I, F1534C, and V410L alleles and resistance to the evaluated pyrethroids, as well as between the VI1016/CC1534/VL410 tri-locus genotype and λ-cyhalothrin and permethrin resistance. The results of the present study contribute to the knowledge of the mechanisms underlying the resistance to key pyrethroids used to control Ae. aegypti along the Caribbean coast of Colombia.


Assuntos
Aedes/genética , Resistência a Inseticidas , Mutação , Piretrinas/farmacologia , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/genética , Aedes/efeitos dos fármacos , Animais , Colômbia , Frequência do Gene , Proteínas de Insetos/genética , Masculino , Nitrilos/farmacologia , Permetrina/farmacologia , Fenótipo
2.
PLoS Med ; 17(9): e1003248, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32946451

RESUMO

BACKGROUND: Two billion long-lasting insecticidal nets (LLINs) have been procured for malaria control. A functional LLIN is one that is present, is in good physical condition, and remains insecticidal, thereby providing protection against vector-borne diseases through preventing bites and killing disease vectors. The World Health Organization (WHO) prequalifies LLINs that remain adequately insecticidal 3 years after deployment. Therefore, institutional buyers often assume that prequalified LLINs are functionally identical with a 3-year lifespan. We measured the lifespans of 3 LLIN products, and calculated their cost per year of functional life, to demonstrate the economic and public health importance of procuring the most cost-effective LLIN product based on its lifespan. METHODS AND FINDINGS: A randomised double-blinded trial of 3 pyrethroid LLIN products (10,571 nets in total) was conducted at 3 follow-up points: 10 months (August-October 2014), 22 months (August-October 2015), and 36 months (October-December 2016) among 3,393 households in Tanzania using WHO-recommended methods. Primary outcome was LLIN functional survival (LLIN present and in serviceable condition). Secondary outcomes were (1) bioefficacy and chemical content (residual insecticidal activity) and (2) protective efficacy for volunteers sleeping under the LLINs (bite reduction and mosquitoes killed). Median LLIN functional survival was significantly different between the 3 net products (p = 0.001): 2.0 years (95% CI 1.7-2.3) for Olyset, 2.5 years (95% CI 2.2-2.8) for PermaNet 2.0 (hazard ratio [HR] 0.73 [95% CI 0.64-0.85], p = 0.001), and 2.6 years (95% CI 2.3-2.8) for NetProtect (HR = 0.70 [95% CI 0.62-0.77], p < 0.001). Functional survival was affected by accumulation of holes, leading to users discarding nets. Protective efficacy also significantly differed between products as they aged. Equivalent annual cost varied between US$1.2 (95% CI $1.1-$1.4) and US$1.5 (95% CI $1.3-$1.7), assuming that each net was priced identically at US$3. The 2 longer-lived nets (PermaNet and NetProtect) were 20% cheaper than the shorter-lived product (Olyset). The trial was limited to only the most widely sold LLINs in Tanzania. Functional survival varies by country, so the single country setting is a limitation. CONCLUSIONS: These results suggest that LLIN functional survival is less than 3 years and differs substantially between products, and these differences strongly influence LLIN value for money. LLIN tendering processes should consider local expectations of cost per year of functional life and not unit price. As new LLIN products come on the market, especially those with new insecticides, it will be imperative to monitor their comparative durability to ensure that the most cost-effective products are procured for malaria control.


Assuntos
Mosquiteiros Tratados com Inseticida/economia , Inseticidas/economia , Controle de Mosquitos/métodos , Animais , Culicidae/efeitos dos fármacos , Vetores de Doenças , Características da Família , Seguimentos , Humanos , Resistência a Inseticidas/efeitos dos fármacos , Mosquiteiros Tratados com Inseticida/tendências , Inseticidas/farmacologia , Malária/prevenção & controle , Controle de Mosquitos/economia , Mosquitos Vetores/efeitos dos fármacos , Piretrinas/farmacologia , Tanzânia/epidemiologia
3.
PLoS One ; 15(9): e0230984, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946446

RESUMO

Insecticide resistance genes are often associated with pleiotropic effects on various mosquito life-history traits. However, very little information is available on the impact of insecticide resistance on blood feeding process in mosquitoes. Here, using two recently detected DNA-based metabolic markers in the major malaria vector, An. funestus, we investigated how metabolic resistance genes could affect the blood meal intake. After allowing both the field F1 and lab F8 Anopheles funestus strains to feed on the human arm for 30 minutes, we assessed the association between key parameters of blood meal process including, probing time, feeding duration, blood feeding success, blood meal size, and markers of glutathione S-transferase (L119F-GSTe2) and cytochrome P450 (CYP6P9a_R)-mediated metabolic resistance. None of the parameters of blood meal process was associated with L119F-GSTe2 genotypes. By contrast, for CYP6P9a_R, homozygous resistant mosquitoes were significantly more able to blood-feed than homozygous susceptible (OR = 3.3; CI 95%: 1.4-7.7; P = 0.01) mosquitoes. Moreover, the volume of blood meal ingested by CYP6P9a-SS mosquitoes was lower than that of CYP6P9a-RS (P<0.004) and of CYP6P9a-RR (P<0.006). This suggests that CYP6P9a gene is inked with the feeding success and blood meal size of An. funestus. However, no correlation was found in the expression of CYP6P9a and that of genes encoding for salivary proteins involved in blood meal process. This study suggests that P450-based metabolic resistance may influence the blood feeding process of Anopheles funestus mosquito and consequently its ability to transmit malaria parasites.


Assuntos
Anopheles/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Glutationa Transferase/metabolismo , Proteínas de Insetos/metabolismo , Mosquitos Vetores/metabolismo , Animais , Anopheles/efeitos dos fármacos , Anopheles/genética , Anopheles/parasitologia , Sangue/metabolismo , Camarões , Sistema Enzimático do Citocromo P-450/genética , Comportamento Alimentar , Feminino , Glutationa Transferase/genética , Humanos , Proteínas de Insetos/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Malária/parasitologia , Malária/prevenção & controle , Malária/transmissão , Mosquitos Vetores/efeitos dos fármacos , Mosquitos Vetores/genética , Mosquitos Vetores/parasitologia , Plasmodium/patogenicidade , Piretrinas/farmacologia , Proteínas e Peptídeos Salivares/metabolismo
4.
PLoS One ; 15(9): e0238601, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32881961

RESUMO

Canines are proven reservoir hosts of Leishmania infantum, the causative agent of human zoonotic visceral leishmaniasis, and therefore domestic dogs play a central role in transmitting the disease to humans. Studies on the effect of insecticide-impregnated dog collars for controlling canine visceral leishmaniasis (CanL) have been increasing; however, meta-analysis has not been conducted. This study assessed the effectiveness of insecticide-impregnated dog collars for preventing CanL. We searched (PubMed, Web of Science, Scopus, Embase, Ovid Medline(R), and Cochrane library), from inception until 2 May 2020. Two authors independently performed articles screening and data extraction. We applied the RoB 2.0 tool to evaluate the risk of bias in randomized trials, while the ROBINS-I tool was used for non-randomized trials. I-squared statistics(I2) and funnel plot and Egger's test, respectively, were used to assesses heterogeneity between studies and publication bias. Relative Risk (RR) and 95% Confidence Interval (CI) were calculated using the random-effects model in Stata 14 software. Out of 242 citations identified, 14 studies comprising 3786 collared dogs and 3428 uncollared dogs were eligible for meta-analysis. The use of deltamethrin-impregnated dog collars(DMC) showed an overall effectiveness of 54% (95%CI: 35-65%, I2 = 63.2%, P = 0.002) in decreasing incidence of CanL, while 10% imidacloprid and 4.5% flumethrin collars provided an overall effectiveness of 90% (95%CI: 80-96%, I2 = 0.0%, P = 0.376). DMC efficacy stratified by follow-up duration was estimated to be 58% (RR = 0.42, 95%CI: 0.20-0.87), 54% (RR = 0.46, 95%CI: 0.31-0.68), 53% (RR = 0.47, 95%CI: 0.29-0.82) for follow-up periods of 5 to 6 months, 1 year and 2 years, respectively. The current evidence indicates that using insecticide-impregnated dog collars can reduce the risk of CanL caused by L. infantum. Therefore, insecticide-impregnated dog collars could be a viable alternative for inclusion as a public health measure for controlling CanL.


Assuntos
Doenças do Cão/prevenção & controle , Inseticidas/farmacologia , Leishmania infantum/efeitos dos fármacos , Leishmaniose Visceral/prevenção & controle , Administração Cutânea , Animais , Doenças do Cão/parasitologia , Cães , Leishmaniose Visceral/veterinária , Neonicotinoides/farmacologia , Nitrilos/farmacologia , Nitrocompostos/farmacologia , Piretrinas/farmacologia
5.
Parasitol Res ; 119(11): 3595-3601, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32935162

RESUMO

Varroosis is the disease caused by the ectoparasitic mite Varroa destructor, one of the most destructive diseases of honeybees. In Spain, there is great concern because there are many therapeutic failures after acaricide treatments intended to control varroosis outbreaks. In some of these cases it is not clear whether such failures are due to the evolution of resistance. Therefore, it is of high interest the development of methodologies to test the level of resistance in mite populations. In this work, a simple bioassay methodology was used to test whether some reports on low efficacy in different regions of Spain were in fact related to reduced Varroa sensitivity to the most used acaricides. This bioassay proved to be very effective in evaluating the presence of mites that survive after being exposed to acaricides. In the samples tested, the mortality caused by coumaphos ranged from 2 to 89%; for tau-fluvalinate, it ranged from 5 to 96%. On the other hand, amitraz caused 100% mortality in all cases. These results suggest the presence of Varroa resistant to coumaphos and fluvalinate in most of the apiaries sampled, even in those where these active ingredients were not used in the last years. The bioassay technique presented here, either alone or in combination with other molecular tools, could be useful in detecting mite populations with different sensitivity to acaricides, which is of vital interest in selecting the best management and/or acaricide strategy to control the parasite in apiaries.


Assuntos
Acaricidas/farmacologia , Resistência a Inseticidas , Varroidae/efeitos dos fármacos , Animais , Abelhas/parasitologia , Bioensaio , Cumafos/farmacologia , Feminino , Infestações por Ácaros , Nitrilos/farmacologia , Piretrinas/farmacologia , Espanha , Toluidinas/farmacologia
6.
Exp Parasitol ; 218: 107986, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32882206

RESUMO

In South America, Triatoma infestans (Hemiptera: Reduviidae) is the main vector of the parasite Trypanosoma cruzi, etiological agent of Chagas disease. The main strategy for vector control is to spray domestic structures with pyrethroids. Reports of populations of T. infestans with varying degrees of resistance to pyrethroids have made the search for alternative molecules for vector control necessary. In the first stage of this work we investigated the lethal activity of amitraz and deltamethrin against susceptible and pyrethroid-resistant nymphs of Triatoma infestans. Lethal dose at 50% (LD50) of susceptible nymphs were compared with those recorded in pyrethroid-resistant nymphs and the resistance ratio (RR50) was obtained. The RR50 of deltamethrin was approximately 300. In the case of amitraz, we observed similar triatomicidal activity in the two nymph populations (RR50: 0.7). In a second stage of the work, we determined the synergistic effect of amitraz and piperonyl butoxide (PBO) on the lethal activity of deltamethrin. The strong synergistic effect of PBO on the lethal activity of deltamethrin in resistant nymphs produced a decrease in RR50 to almost one third of the RR50 reported in absence of the synergist. Amitraz plus PBO lethal activity was similarly increased in pyrethroid susceptible and resistant nymphs. Our data indicate that deltamethrin synergism by amitraz was higher against resistant than to susceptible nymphs (Synergist ratio (SR50) of: 7.2- and 4.1-fold, respectively). In pyrethroid resistant nymphs, the highest level of synergism was obtained combining deltamethrin with amitraz and PBO (SR50: 26.7-fold). These results indicate that this combination could be considered an effective alternative for the control of T. infestans.


Assuntos
Inseticidas/farmacologia , Nitrilos/farmacologia , Sinergistas de Praguicidas/farmacologia , Butóxido de Piperonila/farmacologia , Piretrinas/farmacologia , Toluidinas/farmacologia , Triatoma/efeitos dos fármacos , Animais , Sinergismo Farmacológico , Resistência a Inseticidas , Ninfa/efeitos dos fármacos
7.
Proc Natl Acad Sci U S A ; 117(36): 22042-22050, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32843339

RESUMO

Malaria vector control may be compromised by resistance to insecticides in vector populations. Actions to mitigate against resistance rely on surveillance using standard susceptibility tests, but there are large gaps in the monitoring data across Africa. Using a published geostatistical ensemble model, we have generated maps that bridge these gaps and consider the likelihood that resistance exceeds recommended thresholds. Our results show that this model provides more accurate next-year predictions than two simpler approaches. We have used the model to generate district-level maps for the probability that pyrethroid resistance in Anopheles gambiae s.l. exceeds the World Health Organization thresholds for susceptibility and confirmed resistance. In addition, we have mapped the three criteria for the deployment of piperonyl butoxide-treated nets that mitigate against the effects of metabolic resistance to pyrethroids. This includes a critical review of the evidence for presence of cytochrome P450-mediated metabolic resistance mechanisms across Africa. The maps for pyrethroid resistance are available on the IR Mapper website, where they can be viewed alongside the latest survey data.


Assuntos
Anopheles/efeitos dos fármacos , Resistência a Inseticidas , Inseticidas/farmacologia , Malária/transmissão , Controle de Mosquitos/métodos , Mosquitos Vetores/efeitos dos fármacos , África , Animais , Anopheles/fisiologia , Humanos , Mosquiteiros Tratados com Inseticida , Mosquitos Vetores/fisiologia , Piretrinas/farmacologia
8.
PLoS Negl Trop Dis ; 14(7): e0008404, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32687497

RESUMO

The northeastern semiarid region stands out in the Brazilian context regarding the eco-epidemiology of Chagas disease, in which Triatoma brasiliensis is the main vector of Trypanosoma cruzi. Persistent house invasion threatens the relative levels of progress achieved over previous decades. We conducted an intervention trial with a five-year follow-up to assess the impacts of residual spraying with pyrethroid insecticides on house infestation with T. brasiliensis in 18 rural villages (242 houses) located in the Tauá, Ceará. House infestations were assessed by systematic manual searches for triatomines in every domestic and peridomestic habitat on five occasions. Triatomines were collected in peridomestic (57.5%), sylvatic (35.8%), and intradomiciliary (6.7%) habitats. The most important ecotopes of T. brasiliensis were containing roofing tiles, bricks or rocks (23.4% ± 9.1). Residual insecticide spraying substantially reduced baseline house infestation rates from 27.9% to 5.9% by 6 months post first spraying (MPS). The decline was substantially greater in intradomiciles (11.2% to 0.8%) than in peridomiciles (16.7% to 5%). The mean relative density of triatomines recovered its preintervention values at 14 MPS in intradomiciles, and in the main peridomestic ecotopes. The house infestation levels recorded at 14 MPS persisted thereafter despite all reinfested houses were selectively sprayed on every occasion. Overall average bug infection rates with T. cruzi in the five occasions were in intradomiciles (11.1%), peridomiciles (4.7%) and wild habitats (3.3%). In peridomicile T. cruzi infection rates decreased significantly at all stages after chemical intervention. In intradomicile, the only significant difference occurred at 20 MPS (7.7% to 30.8%). The vectorial capacity of T. brasiliensis, combined with its invasive potential from sylvatic sources and the limited effectiveness of chemical control in the harsh caatinga landscape, pose serious obstacles to the definite elimination of domestic transmission risks. Systematic vector surveillance supported by community participation and locally adapted environmental management measures are needed to reduce the risks of establishment of domestic transmission with T. cruzi in this region.


Assuntos
Controle de Insetos/métodos , Insetos Vetores/efeitos dos fármacos , Inseticidas/farmacologia , Triatoma/efeitos dos fármacos , Distribuição Animal , Animais , Brasil , Habitação , Humanos , Insetos Vetores/fisiologia , Piretrinas/farmacologia , Saúde da População Rural , Triatoma/fisiologia
9.
Nat Commun ; 11(1): 3646, 2020 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-32686679

RESUMO

Papua New Guinea (PNG) has the highest malaria transmission outside of Africa. Long-lasting insecticidal nets (LLINs) are believed to have helped to reduce average malaria prevalence in PNG from 16% in 2008 to 1% in 2014. Since 2015 malaria in PNG has resurged significantly. Here, we present observations documenting decreased bioefficacy of unused LLINs with manufacturing dates between 2013 and 2019 collected from villages and LLIN distributors in PNG. Specifically, we show that of n = 167 tested LLINs manufactured after 2013, only 17% are fulfilling the required World Health Organisation bioefficacy standards of ≥ 80% 24 h mortality or ≥ 95% 60 min knockdown in bioassays with pyrethroid susceptible Anopheles farauti mosquitoes. In contrast, all (100%, n = 25) LLINs with manufacturing dates prior to 2013 are meeting these bioefficacy standards. These results suggest that decreased bioefficacy of LLINs is contributing to the malaria resurgence in PNG and increased scrutiny of LLIN quality is warranted.


Assuntos
Malária , Controle de Mosquitos/métodos , Animais , Anopheles/efeitos dos fármacos , Humanos , Mosquiteiros Tratados com Inseticida , Inseticidas/farmacologia , Malária/epidemiologia , Malária/prevenção & controle , Malária/transmissão , Mosquitos Vetores/efeitos dos fármacos , Papua Nova Guiné/epidemiologia , Piretrinas/farmacologia
10.
Parasitol Res ; 119(10): 3305-3313, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32651636

RESUMO

The genetic structure of natural populations offers insight into the complexities of their dynamics, information that can be relevant to vector control strategies. Microsatellites are useful neutral markers to investigate the genetic structure and gene flow in Triatoma infestans, one of the main vectors of Chagas disease in South America. Recently, a heterogeneous pyrethroid-resistant hotspot was found in the Argentine Gran Chaco, characterized by the highest levels of deltamethrin resistance found at the present time. We applied population genetics analyses to microsatellite and village data and search for associations between the genetic variability and the heterogeneous toxicological pattern previously found. We genotyped 10 microsatellite loci in 67 T. infestans from 6 villages with no, low, and high pyrethroid resistance. The most genetically diverse populations were those susceptible or with low values of resistance. In contrast, high-resistance populations had lower herozygosity and some monomorphic loci. A negative association was found between variability and resistant ratios. Global and pairwise FSTs indicated significant differentiation between populations. The only susceptible population was discriminated in all the performed studies. Low-resistance populations were also differentiated by a discriminant analysis of principal components (DAPC) and were composed mostly by the same two genetic clusters according to STRUCTURE Bayesian algorithm. Individuals from the high-resistance populations were overlapped in the DAPC and shared significant proportions of a genetic cluster. These observations suggest that the resistant populations might have a common origin, although more genetic markers and samples are required to test this hypothesis more rigorously.


Assuntos
Insetos Vetores/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Nitrilos/farmacologia , Piretrinas/farmacologia , Triatoma/genética , Animais , Argentina/epidemiologia , Doença de Chagas/epidemiologia , Doença de Chagas/transmissão , Variação Genética , Repetições de Microssatélites/genética
11.
J Am Mosq Control Assoc ; 36(1): 22-32, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32497474

RESUMO

In several insect species, resistance to pyrethroids and DDT (dichlorodiphenyltrichloroethane) is linked to point mutations in the voltage-gated sodium channel (VGSC) gene. Pyrethroid-based insecticides prolong the opening of sodium channels, causing paralysis known as a "knockdown" effect before mortality occurs. Point mutations in the VGSC gene result in decreased pyrethroid binding and reduced sensitivity to the insecticide-this resistance mechanism is known as knockdown resistance (kdr) as insects do not die but recover from paralysis with time. In Culex mosquito species loss of target site sensitivity to pyrethroids is linked to a number of substitutions, one of which is leucine (L) to phenylalanine (F) at residue 1014 (L1014F) in the VGSC gene. Here we report the identification of kdr-associated pyrethroid resistance and developing resistance in Cx. quinquefasciatus field collections from Collier County, FL. Evaluation of position 1014 of the VGSC in Cx. quinquefasciatus collections from 7 locations in Collier County, FL, revealed a wide range of genotypes from one part of the district to the other. Centers for Disease Control and Prevention bottle bioassay, linear regression analysis, and cage trial evaluations suggest that the L1014F mutation plays a role, at least in part, to the pyrethroid resistance status of Cx. quinquefasciatus collected in Collier County, FL. Furthermore, we identified resistance attributed to both oxidase and esterase activity, indicating that multiple mechanisms are responsible for pyrethroid resistance in Collier County Cx. quinquefasciatus.


Assuntos
Culex/genética , Esterases/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Oxirredutases/genética , Piretrinas/farmacologia , Animais , Culex/efeitos dos fármacos , Culex/enzimologia , Esterases/metabolismo , Feminino , Florida , Oxirredutases/metabolismo
12.
PLoS Negl Trop Dis ; 14(6): e0008350, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32569337

RESUMO

BACKGROUND: The arboviral vector Aedes albopictus became established on all continents except Antarctica in the past 50 years. A consequence of its rapid global invasion is the transmission of diseases previously confined to the tropics and subtropics occurring in temperate regions of the world, including the re-emergence of chikungunya and dengue in Europe. Application of pyrethroids is among the most widely-used interventions for vector control, especially in the presence of an arboviral outbreak. Studies are emerging that reveal phenotypic resistance and monitor mutations at the target site, the para sodium channel gene, primarily on a local scale. METHODS: A total of 512 Ae. albopictus mosquitoes from twelve geographic sites, including those from the native home range and invaded areas, were sampled between 2011 and 2018, and were analyzed at five codons of the para sodium channel gene with mutations predictive of resistance phenotype. Additionally, to test for the origin of unique kdr mutations in Mexico, we analyzed the genetic connectivity of southern Mexico mosquitoes with mosquitoes from home range, the Reunion Island, America and Europe. RESULTS: We detected mutations at all tested positions of the para sodium channel gene, with heterozygotes predominating and rare instance of double mutants. We observed an increase in the distribution and frequency of F1534C/L/S mutations in the ancestral China population and populations in the Mediterranean Greece, the appearance of the V1016G/I mutations as early as 2011 in Italy and mutations at position 410 and 989 in Mexico. The analyses of the distribution pattern of kdr alleles and haplotype network analyses showed evidence for multiple origins of all kdr mutations. CONCLUSIONS: Here we provide the most-up-to-date survey on the geographic and temporal distribution of pyrethroid-predictive mutations in Ae. albopictus by combining kdr genotyping on current and historical samples with published data. While we confirm low levels of pyrethroid resistance in most analyzed samples, we find increasing frequencies of F1534C/S and V1016G in China and Greece or Italy, respectively. The observed patterns of kdr allele distribution support the hypothesis that on site emergence of resistance has contributed more than spread of resistance through mosquito migration/invasions to the current widespread of kdr alleles, emphasizing the importance of local surveillance programs and resistance management.


Assuntos
Aedes/efeitos dos fármacos , Aedes/genética , Resistência a Inseticidas/genética , Piretrinas/farmacologia , Alelos , Animais , Arbovirus , Vetores de Doenças , Variação Genética , Genótipo , Haplótipos , Proteínas de Insetos/genética , Inseticidas/farmacologia , Mosquitos Vetores/genética , Mutação/efeitos dos fármacos , Canais de Sódio/genética
13.
Artigo em Inglês | MEDLINE | ID: mdl-32520213

RESUMO

Although the chemical control against leishmaniasis began in 1953 in Brazil, little information is available on how this strategy has affected populations of phlebotomine sandflies in the field. The objective of this study was to analyze the susceptibility profile of four populations of phlebotomine sandflies to the insecticide alpha-cypermethrin. Sandflies collected in field in four Brazilian municipalities were evaluated using CDC bottles in different concentrations of alpha-cypermethrin. A total of 1,186 phlebotomine sandflies were used in the bioassays. The LD50 ranged from 1.48 to 2.57 ug/mL in the field populations. For a dose of 5 ug/mL of alpha-cypermethrin, the LT50 and LT95 ranged from 17.9 to 27.5 minutes, and LT95 from 39.7 to 61.5 minutes, respectively. All the populations studied were highly susceptible to the insecticide alpha-cypermethrin. Routine studies are needed to detect changes in sandflies susceptibility to insecticides.


Assuntos
Insetos Vetores/efeitos dos fármacos , Inseticidas/farmacologia , Psychodidae/efeitos dos fármacos , Piretrinas/farmacologia , Animais , Brasil , Doenças Endêmicas , Feminino , Insetos Vetores/classificação , Leishmaniose/transmissão , Psychodidae/classificação
14.
Arch Insect Biochem Physiol ; 104(2): e21686, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32378259

RESUMO

Aedes aegypti is the primary mosquito vector of dengue, yellow fever, Zika and chikungunya. Current strategies to control Ae. aegypti rely heavily on insecticide interventions. Pyrethroids are a major class of insecticides used for mosquito control because of their fast acting, highly insecticidal activities and low mammalian toxicity. However, Ae. aegypti populations around the world have begun to develop resistance to pyrethroids. So far, more than a dozen mutations in the sodium channel gene have been reported to be associated with pyrethroid resistance in Ae. aegypti. Co-occurrence of resistance-associated mutations is common in pyrethroid-resistant Ae. aegypti populations. As global use of pyrethroids in mosquito control continues, new pyrethroid-resistant mutations keep emerging. In this microreview, we compile pyrethroid resistance-associated mutations in Ae. aegypti in a chronological order, as they were reported, and summarize findings from functional evaluation of these mutations in an in vitro sodium channel expression system. We hope that the information will be useful for tracing possible evolution of pyrethroid resistance in this important human disease vector, in addition to the development of methods for global monitoring and management of pyrethroid resistance in Ae. aegypti.


Assuntos
Aedes/efeitos dos fármacos , Proteínas de Insetos/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Mutação , Piretrinas/farmacologia , Canais de Sódio/genética , Aedes/genética , Animais
15.
Am J Trop Med Hyg ; 103(2): 810-811, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32394878

RESUMO

According to the WHO, unmanaged insecticide resistance may lead to increases in malaria-related mortality and morbidity. Bangladesh, having made significant progress in malaria control efforts, has recently seen an upswing in malaria cases-58% of which occurred in Bandarban district. Toward identifying entomological drivers of increased malaria, an entomological survey including Anopheles susceptibility to the insecticides in use was conducted in Bandarban. Anopheles vagus, the primary vector of malaria, was found to be resistant to both permethrin and deltamethrin-with only 29% and 55% mortality at 30 minutes, respectively. Intervention strategies in this area-all based on pyrethroids, may need to be reevaluated toward closing this gap in protection and increasing intervention efficacy.


Assuntos
Anopheles/efeitos dos fármacos , Inseticidas/farmacologia , Malária/prevenção & controle , Controle de Mosquitos/métodos , Mosquitos Vetores , Piretrinas/farmacologia , Animais , Anopheles/fisiologia , Bangladesh , Humanos , Resistência a Inseticidas , Malária/transmissão , Nitrilos/farmacologia , Permetrina/farmacologia
16.
PLoS One ; 15(4): e0231251, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32287300

RESUMO

Outdoor residual spraying is proposed for the control of exophilic mosquitoes. However, the residual effect of insecticide mists applied to outdoor resting habitats of mosquitoes is not well characterized. The objective of this study was to assess the longevity of the residual insecticidal effect of three pyrethroid formulations applied to outdoor vegetation against the Southeast Asian malaria vector Anopheles dirus. Lambda-cyhalothrin capsule suspension, deltamethrin emulsifiable concentrate and bifenthrin wettable powder were sprayed on dense bamboo bushes on the Thailand-Myanmar border during the dry season 2018. The duration and magnitude of the residual insecticidal effect were assessed weekly with a standard cone assay, using freshly collected insecticide-treated bamboo leaves and a laboratory-adapted colony of Anopheles dirus sensu stricto susceptible to pyrethroids. The experiment was repeated during the rainy season to assess the persistence of the lambda-cyhalothrin formulation after natural rains and artificial washings. During the dry season (cumulative rainfall = 28 mm in 111 days), mortality and knockdown (KD) rates were >80% for 60 days with bifenthrin and 90 days with lambda-cyhalothrin and deltamethrin. The 50% knockdown time (TKD50) was <15 min with lambda-cyhalothrin and deltamethrin, and <30 min with bifenthrin. During the rainy season (cumulative rainfall = 465 mm in 51 days), mortality and KD rates were >80% for 42 days and TKD50 was <15 min with lambda-cyhalothrin. Additional artificial washing of the testing material with 10L of tap water before performing the cone tests had no significant effect on the residual insecticidal effect of this formulation. Long-lasting residual insecticidal effect can be obtained when spraying pyrethroid insecticides on the outdoor resting habitats of malaria vectors.


Assuntos
Anopheles/efeitos dos fármacos , Insetos Vetores/efeitos dos fármacos , Resistência a Inseticidas , Inseticidas/farmacologia , Controle de Mosquitos/métodos , Nitrilos/farmacologia , Piretrinas/farmacologia , Animais , Anopheles/crescimento & desenvolvimento , Insetos Vetores/crescimento & desenvolvimento , Inseticidas/química , Mianmar , Nitrilos/química , Piretrinas/química , Tailândia
17.
PLoS Negl Trop Dis ; 14(4): e0008154, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32302303

RESUMO

BACKGROUND: Aedes aegypti is a globally distributed vector of human diseases including dengue, yellow fever, chikungunya, and Zika. Pyrethroid insecticides are the primary means of controlling adult A. aegypti populations to suppress arbovirus outbreaks, but resistance to pyrethroid insecticides has become a global problem. Mutations in the voltage-sensitive sodium channel (Vssc) gene are a major mechanism of pyrethroid resistance in A. aegypti. Vssc resistance alleles in A. aegypti commonly have more than one mutation. However, our understanding of the evolutionary dynamics of how alleles with multiple mutations arose is poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: We examined the geographic distribution and association between the common Vssc mutations (V410L, S989P, V1016G/I and F1534C) in A. aegypti by analyzing the relevant Vssc fragments in 25 collections, mainly from Asia and the Americas. Our results showed all 11 Asian populations had two types of resistance alleles: 1534C and 989P+1016G. The 1534C allele was more common with frequencies ranging from 0.31 to 0.88, while the 989P+1016G frequency ranged from 0.13 to 0.50. Four distinct alleles (410L, 1534C, 410L+1534C and 410L+1016I+1534C) were detected in populations from the Americas. The most common was 410L+1016I+1534C with frequencies ranging from 0.50 to 1.00, followed by 1534C with frequencies ranging from 0.13 to 0.50. Our phylogenetic analysis of Vssc supported multiple independent origins of the F1534C mutation. Our results indicated the 410L+1534C allele may have arisen by addition of the V410L mutation to the 1534C allele, or by a crossover event. The 410L+1016I+1534C allele was the result of one or two mutational steps from a 1534C background. CONCLUSIONS/SIGNIFICANCE: Our data corroborated previous geographic distributions of resistance mutations and provided evidence for both recombination and sequential accumulation of mutations contributing to the molecular evolution of resistance alleles in A. aegypti.


Assuntos
Aedes/genética , Alelos , Evolução Molecular , Resistência a Inseticidas/genética , Mutação , Recombinação Genética , Animais , Feminino , Haplótipos , Inseticidas/farmacologia , Masculino , Mosquitos Vetores/genética , Filogenia , Piretrinas/farmacologia
18.
Parasit Vectors ; 13(1): 163, 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32245509

RESUMO

BACKGROUND: Triatomine bugs are responsible for the vectorial transmission of the parasite Trypanosoma cruzi, etiological agent of Chagas disease, a zoonosis affecting 10 million people and with 25 million at risk of infection. Several triatomine species of the genus Rhodnius have been found inhabiting palm crowns where insects can find shelter in leaves axils and blood from palm-associated vertebrates. Rhodnius prolixus insects have been collected in oil palms in Colombia, and high T. cruzi infection rates were found. Since pest control is carried out in oil palm plantations, continuous exposure to insecticides could be occurring in these triatomines. Some insecticides suggested for pest control in oil palm plantations are also recommended for triatomine control in human dwellings. In this study, our objective was to assess if triatomines inhabiting oil palms exhibit resistance to deltamethrin, an insecticide used for vector control. METHODS: Rhodnius prolixus nymphs were sampled in oil palms located in Tauramena, Colombia. To determine deltamethrin resistance, biological and biochemical assays were carried out on fifth-instar nymphs from the F1 generation. For biological assays, pure and commercial deltamethrin were used, and in biochemical assays, activities of detoxifying enzymes related to pyrethroid resistance, such as oxidases, esterases and transferases, were quantified. RESULTS: Deltamethrin lethal dosage 50 and 90 in R. prolixus from oil palms was significantly higher than in those from a susceptible colony suggesting possible deltamethrin resistance. Moreover, mortality with commercial deltamethrin was very low in insects from oil palms. In biochemical assays, the activity of evaluated detoxifying enzymes was significantly higher in R. prolixus from oil palms than in those from the susceptible colony. CONCLUSIONS: Possible deltamethrin resistance found in R. prolixus insects from oil palms could threaten traditional vector control strategies in urban settings if insecticide-resistant triatomines can migrate from oil palms plantations. In palm oil producer countries such as Colombia, the oil palm plantations are growing constantly during the last years. We suggest that pest control strategies in oil palm crops should include triatomine surveillance and toxicological monitoring, especially in zones with several Chagas disease cases.


Assuntos
Resistência a Inseticidas , Inseticidas , Nitrilos/farmacologia , Controle de Pragas/métodos , Saúde Pública/métodos , Piretrinas/farmacologia , Triatoma , Agricultura/métodos , Animais , Colômbia , Insetos Vetores/parasitologia , Ninfa/parasitologia , Óleo de Palmeira , Rhodnius/parasitologia , Triatoma/parasitologia
19.
Korean J Parasitol ; 58(1): 99-102, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32145735

RESUMO

Two-point mutations (V419L and L925I) on the voltage-sensitive sodium channel of bed bugs (Cimex lectularius) are known to confer pyrethroid resistance. To determine the status of pyrethroid resistance in bed bugs in Korea, resistance allele frequencies of bed bug strains collected from several US military installations in Korea and Mokpo, Jeollanamdo, from 2009-2019 were monitored using a quantitative sequencing. Most bed bugs were determined to have both of the point mutations except a few specimens, collected in 2009, 2012 and 2014, having only a single point mutation (L925I). No susceptible allele was observed in any of the bed bugs examined, suggesting that pyrethroid resistance in bed bug populations in Korea has reached a serious level. Large scale monitoring is required to increase our knowledge on the distribution and prevalence of pyrethroid resistance in bed bug populations in Korea. Based on present study, it is urgent to restrict the use of pyrethroids and to introduce effective alternative insecticides. A nation-wide monitoring program to determine the pyrethroid resistance level in bed bugs and to select alternative insecticides should be implemented.


Assuntos
Percevejos-de-Cama/genética , Frequência do Gene , Piretrinas/farmacologia , Animais , Resistência a Medicamentos , República da Coreia
20.
Acta Trop ; 206: 105440, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32156617

RESUMO

Despite reduction in the prevalence of malaria, Guinea-Bissau (GB) is still widely affected by the disease that is primarily vectored by Anopheles gambiae s.l. mosquitoes. Monitoring mosquito susceptibility and investigating the insecticide resistance status is an integral part of malaria control actions. Here, mosquito populations from five regions of GB: Bafatá, Bissau, Buba, Cacheu and Gabu were monitored for species ID and insecticide resistance, using diagnostic and intensity WHO bioassays, as well as molecular assays. Phenotypic and molecular identification of species showed the presence of An. gambiae s.s. (S form), An. coluzzii (M form) and An. arabiensis, as well as rare An. arabiensis/ An. gambiae hybrids. Resistance to permethrin and deltamethrin was found in all Anopheles populations assayed, with the intensity of resistance for permethrin being moderate to high, as confirmed by bioassays performed at concentration intensities of 5X and 10X. Consistent to these findings, molecular analysis showed a higher frequency of knock-down resistance (kdr) mutations (L1014F, L1014S, reaching > 90% in some areas) compared to previous studies in the same region, as well as detected for the first time the presence of the super kdr mutation (N1575Y) in GB. The "iAche" (G119S) resistance mutation was also found in GB in low frequencies (up to 12.41%). Additionally, the synergistic PBO-permethrin bioassays suggested partial involvement of non target (metabolic and/or reduced penetration) resistance mechanism. Expression analysis of known pyrethroid metabolisers indicated the slight overexpression and possible association of the cytochrome P450s CYP6Z1, CYP4G16 with the pyrethroid resistance phenotype. The findings should guide future evidence-based resistance management strategies in GB.


Assuntos
Anopheles/genética , Resistência a Inseticidas/genética , Malária/transmissão , Mosquitos Vetores/genética , Animais , Anopheles/efeitos dos fármacos , Feminino , Guiné-Bissau , Inseticidas/farmacologia , Masculino , Nitrilos/farmacologia , Permetrina/farmacologia , Piretrinas/farmacologia
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