scholarly journals Evaluation of resistance to pyrethroid and organophosphate adulticides and kdr genotyping in Aedes aegypti populations from Roraima, the Northernmost Brazilian State

2020 ◽  
Author(s):  
Ramão Luciano Nogueira Hayd ◽  
Luana Carrara ◽  
Joel de Melo Lima ◽  
Nathalia Coelho Vargas de Almeida ◽  
José Bento Pereira Lima ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Pyrethroid Resistance ◽  
Control Strategies ◽  
World Health ◽  
Urban Centers ◽  
International Borders ◽  
Two Cities ◽  
Health Organization ◽  
Amazonas State ◽  
Urban Conditions

Abstract Background. Roraima, the northernmost State in Brazil, borders Venezuela and Guyana. Although mostly covered by the tropical forests, the urban centers of this State are highly infested with Ae. aegypti and endemic for dengue, Zika and chikungunya. Herein we present the levels of Ae. aegypti infestation and number of arboviruses cases between 2015 and 2018 in the studied localities. We accessed the insecticide resistance status of Ae. aegypti populations from the capital Boa Vista, two cities on international borders (Pacaraima and Bonfim) and Rorainópolis bordering Amazonas State, in order to evaluate the chemical control efficacy in these localities. Methods. Tests with World Health Organization (WHO)-like tubes impregnated with the pyrethroid deltamethrin (0.05 and 0.12%) and the organophosphate malathion (0.7%) were conducted with Ae. aegypti from Boa Vista, Pacaraima, Bonfim and Rorainópolis, collected in 2016 and 2018. Genotyping of kdr mutations, related to resistance to pyrethroids, was performed for the SNP variations in the sites 1016 and 1534 of the voltage gated sodium channel gene (NaV) with a TaqMan qPCR approach. Results. Ae. albopictus was absent in our collections, and therefore only Ae. aegypti was tested. All Ae. aegypti populations were susceptible to 0.7% malathion in 2016, however mortality dropped to under 90% in Bonfim and Pacaraima populations in 2018. All populations were resistant to 0.05% deltamethrin in both years. The time that 50% of females suffered knockdown (KdT50) under exposition to 0.05% deltamethrin was 3.3-5.9 fold longer in mosquitoes from the populations compared to the susceptible strain Rockefeller. Only Pacaraima population (2018) remained resistant to 0.12% deltamethrin. The kdr genotyping revealed the absence of the wild-type NaVS haplotype (1016Val + 1534Phe) in the populations from Roraima, signifying that all tested insects had a genetic background for pyrethroid resistance. The double kdr NaVR2 haplotype (1016Ile + 15434Cys) was present in higher frequencies in all populations except Rorainópolis, where this haplotype seems to have arrived recently. Conclusions. These results are important for the knowledge about insecticide resistance status of Ae. aegypti populations from Roraima and will help to improve vector control strategies that may be applied to diverse localities under similar geographical and urban conditions.

scholarly journals Evaluation of resistance to pyrethroid and organophosphate adulticides and kdr genotyping in Aedes aegypti populations from Roraima, the Northernmost Brazilian State

2020 ◽  
Author(s):  
Ramão Luciano Nogueira Hayd ◽  
Luana Carrara ◽  
Joel de Melo Lima ◽  
Nathalia Coelho Vargas de Almeida ◽  
José Bento Pereira Lima ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Pyrethroid Resistance ◽  
Control Strategies ◽  
World Health ◽  
Urban Centers ◽  
International Borders ◽  
Two Cities ◽  
Health Organization ◽  
Amazonas State ◽  
Urban Conditions

Abstract Background. Roraima, the northernmost State in Brazil, borders Venezuela and Guyana. Although mostly covered by the tropical forests, the urban centers of this State are highly infested with Ae. aegypti and endemic for dengue, Zika and chikungunya. Herein we present the levels of Ae. aegypti infestation and number of arboviruses cases between 2015 and 2018 in the studied localities. We accessed the insecticide resistance status of Ae. aegypti populations from the capital Boa Vista, two cities on international borders (Pacaraima and Bonfim) and Rorainópolis bordering Amazonas State, in order to evaluate the chemical control efficacy in these localities. Methods. Tests with World Health Organization (WHO)-like tubes impregnated with the pyrethroid deltamethrin (0.05 and 0.12%) and the organophosphate malathion (0.7%) were conducted with Ae. aegypti from Boa Vista, Pacaraima, Bonfim and Rorainópolis, collected in 2016 and 2018. Genotyping of kdr mutations, related to resistance to pyrethroids, was performed for the SNP variations in the sites 1016 and 1534 of the voltage gated sodium channel gene (NaV) with a TaqMan qPCR approach. Results. Ae. albopictus was absent in our collections, and therefore only Ae. aegypti was tested. All Ae. aegypti populations were susceptible to 0.7% malathion in 2016, however mortality dropped to under 90% in Bonfim and Pacaraima populations in 2018. All populations were resistant to 0.05% deltamethrin in both years. The time that 50% of females suffered knockdown (KdT50) under exposition to 0.05% deltamethrin was 3.3-5.9 fold longer in mosquitoes from the populations compared to the susceptible strain Rockefeller. Only Pacaraima population (2018) remained resistant to 0.12% deltamethrin. The kdr genotyping revealed the absence of the wild-type NaVS haplotype (1016Val + 1534Phe) in the populations from Roraima, signifying that all tested insects had a genetic background for pyrethroid resistance. The double kdr NaVR2 haplotype (1016Ile + 15434Cys) was present in higher frequencies in all populations except Rorainópolis, where this haplotype seems to have arrived recently. Conclusions. These results are important for the knowledge about insecticide resistance status of Ae. aegypti populations from Roraima and will help to improve vector control strategies that may be applied to diverse localities under similar geographical and urban conditions.

scholarly journals Evaluation of resistance to pyrethroid and organophosphate adulticides, and kdr genotyping in Ades aegypti populations from Roraima, the Northernmost Brazilian State

2020 ◽  
Author(s):  
Ramão Luciano Nogueira Hayd ◽  
Luana Carrara ◽  
Joel de Melo Lima ◽  
Nathalia Coelho Vargas de Almeida ◽  
José Bento Pereira Lima ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Control Strategies ◽  
Wild Type ◽  
Urban Centers ◽  
Channel Gene ◽  
S Haplotype ◽  
International Borders ◽  
Two Cities ◽  
Amazonas State ◽  
Taqman Qpcr

Abstract Background Roraima is the northernmost State in Brazil and makes international borders with Venezuela and Guyana. Although mostly covered by the tropical forests, the urban centers are highly infested with Ae. aegypti and endemic for dengue, Zika and chikungunya. Here we presented the levels of Ae. aegypti infestation and number of arboviruses cases between 2015 and 2018 in the studied localities. We evaluated the insecticide resistance status of Ae. aegypti populations from the capital Boa Vista, two cities in international borders: Pacaraima and Bonfim, and Rorainópolis in the limit with Amazonas State, collected in 2016 and 2018. Methods WHO like tube tests with the pyrethroid deltamethrin (0.05 and 0.12%) and the organophosphate malathion (0.7%) were conducted. Genotyping of kdr mutations, related to resistance to pyrethroids, were performed for the SNP variations in the sites 1016 and 1534 of the voltage gated sodium channel gene (Na V ) with a TaqMan qPCR approach. Results Only Ae. aegypti was present in our collection, meaning that there is still a barrier that Ae. albopictus was still not able to transpose from Amazonas toward Roraima. All Ae. aegypti populations were susceptible to 0.7% malathion in 2016, however mortality dropped to under 90% in Bonfim and Pacaraima in 2018. All populations were resistant to 0.5% deltamethrin in both years. The time that 50% of females suffered knockdown ( Kd T 50 ) under exposition to 0.5% deltamethrin was 3.3-5.9 fold longer in mosquitoes from the populations compared to Rockefeller. Only Pacaraima (2018) remained resistant to 0.12% deltamethrin. The kdr genotyping revealed the absence of the wild-type Na V S haplotype (1016Val + 1534Phe) in populations from Roraima, meaning that all tested individuals had a genetic background for resistance to pyrethroid. The double kdr Na V R2 haplotype (1016Ile + 15434Cys) was under higher frequencies in all populations except Rorainópolis, where this haplotype seems to have arrived recently. Conclusions These results are important to the knowledge about insecticide resistance status of Ae. aegypti populations from Roraima and will help to improve vector control strategies that may be applied to diverse localities with similar conditions.

scholarly journals Insecticide resistance characteristic of Anopheles vector species successfully controlled by deployment of pyrethroid and PBO long lasting insecticidal treated nets (LLINs) in Tanzania

2021 ◽  
Author(s):  
Johnson Matowo ◽  
David Weetman ◽  
Patricia Pignatell ◽  
Alexandra Wright ◽  
Jacques Charlwood ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Pyrethroid Resistance ◽  
Cluster Randomized Trial ◽  
World Health ◽  
Malaria Vectors ◽  
Metabolizing Enzymes ◽  
Sub Saharan ◽  
Underlying Mechanisms ◽  
Cluster Randomized ◽  
Health Organization

Long lasting insecticidal nets (LLINs) are a proven tool to reduce malaria transmission, but in Africa efficacy is being reduced by pyrethroid resistance in the major vectors. A cluster randomized trial in Muleba district, Tanzania demonstrated that permethrin LLINs co-treated with piperonyl butoxide (PBO), a synergist that can block pyrethroid-metabolizing enzymes in the mosquito, had much greater efficacy than pyrethroid-only nets. Insecticide resistance profiles and underlying mechanisms were investigated in Anopheles gambiae and An. funestus from Muleba during the trial. Diagnostic dose bioassays using permethrin, together with intensity assays, suggest pyrethroid resistance that is both strong and very common, but not extreme. Transcriptomic analysis found multiple P450 genes over expressed including CYP6M2, CYP6Z3, CYP6P3, CYP6P4, CYP6AA1 and CYP9K1 in An. gambiae and CYP6N1, CYP6M7, CYP6M1 and CYP6Z3 in An. funestus. Indeed, very similar suites of P450 enzymes commonly associated with resistant populations elsewhere in Africa were detected as over expressed suggesting a convergence of mechanisms across Sub-Saharan African malaria vectors. The findings give insight into factors that may correlate with pyrethroid PBO LLIN success, broadly supporting model predictions, but revision to guidelines previously issued by the World Health Organization is warranted.

scholarly journals Mapping insecticide resistance in mosquitoes to aid malaria control

2020 ◽  
Author(s):  
Catherine L. Moyes ◽  
Duncan Kobia Athinya ◽  
Tara Seethaler ◽  
Katherine Battle ◽  
Marianne Sinka ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Malaria Control ◽  
Pyrethroid Resistance ◽  
Resistance Management ◽  
Resistance Mechanisms ◽  
World Health ◽  
Malaria Vector Control ◽  
Metabolic Resistance ◽  
Insecticide Resistance Management ◽  
Health Organization

AbstractMalaria 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. 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 (WHO) 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.Significance StatementMalaria control in Africa largely relies on the use of insecticides to prevent mosquitoes from transmitting the malaria parasite to humans, however, these mosquitoes have evolved resistance to these insecticides. To manage this threat to malaria control, it is vital that we map locations where the prevalence of resistance exceeds thresholds defined by insecticide resistance management plans. A geospatial model and data from Africa are used to predict locations where thresholds of resistance linked to specific recommended actions are exceeded. This model is shown to provide more accurate next-year predictions than two simpler approaches. The model is used to generate maps that aid insecticide resistance management planning and that allow targeted deployment of interventions that counter specific mechanisms of resistance.

scholarly journals Personal protection with PBO-pyrethroid synergist-treated nets after 2 years of household use against pyrethroid-resistant Anopheles in Tanzania

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Jackline L. Martin ◽  
Franklin W. Mosha ◽  
Eliud Lukole ◽  
Mark Rowland ◽  
Jim Todd ◽  
...  
Keyword(s):  
Pyrethroid Resistance ◽  
Density Ratio ◽  
Household Survey ◽  
Sensu Stricto ◽  
World Health ◽  
Malaria Vectors ◽  
Personal Protection ◽  
North West ◽  
Hole Index ◽  
Health Organization

Abstract Background The spread of pyrethroid resistance in malaria vectors threatens the effectiveness of standard long-lasting insecticidal nets (LLIN). Synergist nets combine pyrethroid (Py) and piperonyl-butoxide (PBO) to enhance potency against resistance mediated by mono-oxygenase mechanisms. Our project assessed personal protection of the World Health Organization first-in-class PBO-Py LLIN (Olyset Plus) versus the standard LLIN (Olyset net) against pyrethroid-resistant Anopheles gambiae sensu lato (s.l.) and An. funestus in North-West Tanzania after 20 months of household use. Methods From a household survey, 39 standard Olyset net and 39 Olyset Plus houses were selected. The physical integrity and hole index (HI) of the nets were assessed, and resting mosquitoes were collected from inside nets and from room walls. The indoor abundance was estimated using CDC light traps and species identified using PCR. The bioefficacy of PBO and standard LLINs against wild Anopheles was assessed using 30-minute cylinder bioassays. Results Of 2397 Anopheles collected, 8.9% (n = 213) were resting inside standard Olyset nets, while none were found inside Olyset Plus nets (PBO-Py LLINs) of any HI category. Resting density of blood-fed mosquitoes was higher on walls of sleeping rooms with Olyset nets compared to Olyset Plus (0.62 vs 0.10, density ratio [DR]: 0.03, 95% CI 0.01–0.13, p < 0.001). Mosquitoes were found inside Olyset nets of all WHO HI categories, but more were collected inside the more damaged nets (HI ≥ 643) than in less damaged (HI 0–64) nets (DR: 6.4, 95% CI 1.1–36.0, p = 0.037). In bioassay, mortality of An. gambiae s.l. was higher with Olyset Plus than with Olyset nets for new nets (76.8% vs 27.5%) and nets used for 20 months (56.8% vs 12.8%); similar trends were observed with An. funestus. Conclusion The PBO-Py LLINs provided improved protection after 20 months of household use, as demonstrated by the higher bioassay mortality and absence of pyrethroid-resistant An. gambiae sensu stricto (s.s.) and An. funestus collected from inside Olyset Plus nets, irrespective of HI category, as compared to Olyset nets.

Insecticide Resistance in Anopheles stephensi in Somali Region, Eastern Ethiopia

2020 ◽  
Author(s):  
Solomon Yared ◽  
Araya Gebressielasie ◽  
Lambodhar Damodaran ◽  
Victoria Bonnell ◽  
Karen Lopez ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Stephensi ◽  
Mortality Rates ◽  
Resistance Mechanisms ◽  
World Health ◽  
Malaria Vectors ◽  
Eastern Ethiopia ◽  
Pyrethroid Insecticides ◽  
Pirimiphos Methyl ◽  
Health Organization

Abstract Background: The movement of malaria vectors into new areas is a growing concern in the efforts to control malaria. The recent report of Anopheles stephensi in eastern Ethiopia has raised the necessity to understand the insecticide resistance status of the vector in the region to better inform vector-based interventions. The aim of this study was to evaluate insecticide resistance in An. stephensi in eastern Ethiopia using two approaches: 1) World Health Organization (WHO) bioassay tests in An. stephensi and 2) genetic analysis of insecticide resistance genes in An. stephensi in eastern Ethiopia. Methods: Mosquito larvae and pupae were collected from Kebridehar. Insecticide susceptibility of An. stephensi was tested with malathion 5%, bendiocarb 0.1%, propoxur 0.1%, deltamethrin 0.05%, permethrin 0.75%, Pirimiphos-methyl 0.25% and DDT 4%, according to WHO standard protocols. Results: All An. stephensi samples were resistant to carbamates, with mortality rates 23% and 21% for bendiocarb and propoxur, respectively. Adult An. stephensi was also resistant to pyrethroid insecticides with mortality rates 67% for deltamethrin and 53% for permethrin. Resistance to DDT and malathion was detected in An. stephensi with mortality rates of 32% as well as An. stephensi was resistance to pirimiphos-methyl with mortality rates 14%. Analysis of the voltage gate sodium channel gene (vgsc) revealed the absence of kdr L1014 mutations. Conclusion: Overall, these findings support that An. stephensi is resistant to several classes of insecticides, most notably pyrethroids. However, the absence of the kdr L1014 gene may suggest non-target site resistance mechanisms. Continuous insecticide resistance monitoring should be carried out in the region to confirm the documented resistance and exploring mechanisms conferring resistance in An. stephensi in Ethiopia.

scholarly journals Assessing Insecticide Resistance in Adult Mosquitoes: Perspectives on Current Methods

2020 ◽  
Vol 14 ◽  
pp. 117863022095279
Author(s):  
Stephanie L Richards ◽  
Brian D Byrd ◽  
Michael H Reiskind ◽  
Avian V White
Keyword(s):  
Insecticide Resistance ◽  
Training Programs ◽  
Data Interpretation ◽  
Control Measures ◽  
World Health ◽  
Control Programs ◽  
Global Issue ◽  
Control And Prevention ◽  
Health Organization ◽  
Level Training

Mosquito insecticide resistance (IR) is a growing global issue that must be addressed to protect public health. Vector control programs (VCPs) should regularly monitor local mosquito populations for IR and plan control measures accordingly. In some cases, state/federal resources financially support this testing with expertise and/or training programs. Standardization of methods (eg, Centers for Disease Control and Prevention bottle bioassay, World Health Organization tube testing, dose-mortality bioassay) for monitoring IR must be prioritized. One solution is regional hubs of IR monitoring at the state or other level. Training programs on methodology and interpretation of results should be developed and routinely offered to local VCPs conducting IR testing in mosquitoes. Here, current methods for assessing mosquito IR are discussed and insights into a variety of questions from VCPs are considered. It is critical that methods for IR monitoring and data interpretation are standardized through routine training, with the goal of evidence-driven decision making to improve control of mosquitoes and mosquito-borne disease.

scholarly journals No Evidence of SARS-CoV-2 Circulation in Rome (Italy) during the Pre-Pandemic Period: Results of a Retrospective Surveillance

2020 ◽  
Vol 17 (22) ◽  
pp. 8461
Author(s):  
Carlo Capalbo ◽  
Enrico Bertamino ◽  
Alessandro Zerbetto ◽  
Iolanda Santino ◽  
Andrea Petrucca ◽  
...  
Keyword(s):  
Control Strategies ◽  
Local Level ◽  
Central Italy ◽  
Total Sample ◽  
World Health ◽  
Infection Prevalence ◽  
Health Authorities ◽  
Causative Agents ◽  
Definition Of ◽  
Health Organization

In March 2020, the World Health Organization (WHO) declared that the COVID-19 outbreak recorded over the previous months could be characterized as a pandemic. The first known Italian SARS-CoV-2 positive case was reported on 21 February. In some countries, cases of suspected “COVID-19-like pneumonia” had been reported earlier than those officially accepted by health authorities. This has led many investigators to check preserved biological or environmental samples to see whether the virus was detectable on dates prior to those officially stated. With regard to Italy, the results of a microbiological screening in sewage samples collected between the end of February and the beginning of April 2020 from wastewaters in Milan (Northern Italy) and Rome (Central Italy) showed presence of SARS-CoV-2. In the present study, we evaluated, by means of a standardized diagnostic method, the SARS-CoV-2 infection prevalence amongst patients affected by severe acute respiratory syndrome (SARI) in an academic hospital located in Central Italy during the period of 1 November 2019–1 March 2020. Overall, the number of emergency room (ER) visits during the investigated period was 13,843. Of these, 1208 had an influenza-like syndrome, but only 166 matched the definition of SARI as stated in the study protocol. A total of 52 SARI cases were laboratory confirmed as influenza: 26 as a type B virus, 25 as a type A, and 1 as both viruses. Although about 17% of the total sample had laboratory or radiological data compatible with COVID-19, all the nasopharyngeal swabs stored underwent SARS-CoV-2 RT-PCR and tested negative. Based on our result, it is confirmed that the COVID-19 pandemic spread did not start prior to the “official” onset in central Italy. Routine monitoring of SARI causative agents at the local level is critical for reporting epidemiologic and etiologic trends that may differ from one country to another and also among different influenza seasons. This has a practical impact on prevention and control strategies.

scholarly journals Assessment of the susceptibility status of Aedes aegypti (Diptera: Culicidae) populations to pyriproxyfen and malathion in a nation-wide monitoring of insecticide resistance performed in Brazil from 2017 to 2018

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Kauara Brito Campos ◽  
Ademir Jesus Martins ◽  
Cynara de Melo Rodovalho ◽  
Diogo Fernandes Bellinato ◽  
Luciana dos Santos Dias ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Mosquito Control ◽  
Natural Populations ◽  
Adult Emergence ◽  
World Health ◽  
Two Generations ◽  
Wide Scale ◽  
Susceptibility Tests ◽  
The One ◽  
Health Organization

Abstract Background Chemical mosquito control using malathion has been applied in Brazil since 1985. To obtain chemical control effectiveness, vector susceptibility insecticide monitoring is required. This study aimed to describe bioassay standardizations and determine the susceptibility profile of Ae. aegypti populations to malathion and pyriproxyfen, used on a national scale in Brazil between 2017 and 2018, and discuss the observed impacts in arbovirus control. Methods The diagnostic-doses (DD) of pyriproxyfen and malathion were determined as the double of adult emergence inhibition (EI) and lethal doses for 99% of the Rockefeller reference strain, respectively. To monitor natural populations, sampling was performed in 132 Brazilian cities, using egg traps. Colonies were raised in the laboratory for one or two generations (F1 or F2) and submitted to susceptibility tests, where larvae were exposed to the pyriproxyfen DD (0.03 µg/l) and adults, to the malathion DD determined in the present study (20 µg), in addition to the one established by the World Health Organization (WHO) DD (50 µg) in a bottle assay. Dose-response (DR) bioassays with pyriproxyfen were performed on populations that did not achieve 98% EI in the DD assays. Results Susceptibility alterations to pyriproxyfen were recorded in six (4.5%) Ae. aegypti populations from the states of Bahia and Ceará, with Resistance Ratios (RR95) ranging from 1.51 to 3.58. Concerning malathion, 73 (55.3%) populations distributed throughout the country were resistant when exposed to the local DD 20 µg/bottle. On the other hand, no population was resistant, and only 10 (7.6%) populations in eight states were considered as exhibiting decreased susceptibility (mortality ratios between 90 and 98%) when exposed to the WHO DD (50 µg/bottle). Conclusions The feasibility of conducting an insecticide resistance monitoring action on a nation-wide scale was confirmed herein, employing standardized and strongly coordinated sampling methods and laboratory bioassays. Brazilian Ae. aegypti populations exhibiting decreased susceptibility to pyriproxyfen were identified. The local DD for malathion was more sensitive than the WHO DD for early decreased susceptibility detection.

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