Efficacy of a spatial repellent for control of Aedes-borne virus transmission: A cluster-randomized trial in Iquitos, Peru.

Over half the world's population is at risk for viruses transmitted by Aedes mosquitoes, such as dengue and Zika. The primary vector, Aedes aegypti, thrives in urban environments. Despite decades of effort, cases and geographic range of Aedes-borne viruses (ABVs) continue to expand. Rigorously proven vector control interventions that measure protective efficacy against ABV diseases are limited to Wolbachia in a single trial in Indonesia and do not include any chemical intervention. Spatial repellents, a new option for efficient deployment, are designed to decrease human exposure to ABVs by releasing active ingredients into the air that disrupt mosquito-human contact. A parallel, cluster-randomized controlled trial was conducted in Iquitos, Peru, to quantify the impact of a transfluthrin-based spatial repellent on human ABV infection. From 2,907 households across 26 clusters (13 per arm), 1,578 participants were assessed for seroconversion (primary endpoint) by survival analysis. Incidence of acute disease was calculated among 16,683 participants (secondary endpoint). Adult mosquito collections were conducted to compare Ae. aegypti abundance, blood-fed rate, and parity status through mixed-effect difference-in-difference analyses. The spatial repellent significantly reduced ABV infection by 34.1% (one-sided 95% CI lower limit, 6.9%; one-sided P value = 0.0236, z = 1.98). Aedes aegypti abundance and blood-fed rates were significantly reduced by 28.6 (95% CI 24.1%, ∞); z = -9.11) and 12.4% (95% CI 4.2%, ∞); z = -2.43), respectively. Our trial provides conclusive statistical evidence from an appropriately powered, preplanned cluster-randomized controlled clinical trial of the impact of a chemical intervention, in this case a spatial repellent, to reduce the risk of ABV transmission compared to a placebo.

Unlocking the human factor to increase effectiveness and sustainability of malaria vector control.

BACKGROUND: Progress in the fight against malaria has stalled in recent years, highlighting the importance of new interventions and tailored approaches. A critical factor that must be considered across contexts and interventions is human behaviour. MAIN TEXT: Factors such as acceptance of insecticide-treated nets (ITNs) and indoor residual spraying (IRS), ability and willingness to consistently use and appropriately care for ITNs and refraining from post-spray wall modifications can all impact the success of core vector control interventions. Understanding factors that can drive or inhibit these behaviours can contribute to improved social and behaviour change strategies and in turn, improved outcomes. Likewise, patterns of nighttime activities can reveal specific gaps in protection that cannot be filled by core interventions and inform development and deployment of complementary tools that meet people's needs and preferences. There is an opportunity to increase use of approaches such as human-centred design to engage affected communities more actively in identifying and developing sustainable solutions that meet their needs and lifestyles. Integration of social and behavioural research with entomological and epidemiological evaluations will provide a more complete picture of malaria transmission dynamics and inform improved targeting of context-appropriate interventions. Finally, for gains to be maintained, interventions must be rooted within systems that support long-term success. This includes a movement toward more sustainable vector control solutions, increased decision-making and ownership of research, implementation, and strategy development at the country level, and inclusive approaches that ensure all men, women, boys, and girls are engaged as part of the solution. CONCLUSIONS: No matter how efficacious, a tool will remain ineffective if communities do not engage with it or use it regularly. Entering the next decade in the fight against malaria there is a critical opportunity to elevate the role of social and behaviour change to increase the impact and sustainability of malaria control and elimination efforts. This includes removing social and structural barriers to use of existing tools at all levels, human-centred and inclusive design and implementation of new tools, and movement toward long-term solutions led by affected communities.

Evaluation of malaria preventive measures among adult patients attending the Bamendjou and Foumbot district hospitals of the West Region of Cameroon.

BACKGROUND: Although a significant decrease in entomological and epidemiological indicators was reported in Cameroon since the introduction of insecticide-treated bed nets, malaria prevalence remains high also in some parts of the West Region of Cameroon. This study was designed to evaluate malaria preventive measures among patients attending the Bamendjou and Foumbot District hospitals of the West Region of Cameroon. METHODS: This was a cross-sectional study carried out within a period of 3 months, from January to March 2020. Data was obtained using a structured questionnaire and laboratory analysis. The CareStart™ Pf Malaria HRP2 qualitative rapid diagnostic test was used for malaria diagnosis. The questionnaire was designed to collect information on respondent's socio-demographic characteristics, and the use of malaria preventive measures. Data were analysed using descriptive statistics, regression analysis, and Chi-square (and Fisher's exact) test. RESULTS: A total of 170 study participants were recruited in Foumbot and 197 in Bamendjou. Malaria was significantly (P < 0.0001) more prevalent in Foumbot (47.06%) than in Bamendjou (19.8%). In Foumbot, non-use of insect repellent spray (P = 0.0214), insect repellent body cream (P = 0.0009), mosquito spray (P = 0.0001) and not draining stagnant water (P = 0.0004) predisposed to higher risk of malaria. In Bamendjou, non-use of insect repellent spray (P = 0.0012), long-lasting insecticidal bed nets (P = 0.0001), window and door nets (P = 0.0286), predisposed to a higher risk of malaria. CONCLUSIONS: Malaria prevalence was high among the study participants especially in Foumbot. An adequate follow-up to ensure effective execution of the recently launched third phase of LLINs distribution campaign in Cameroon is recommended. Additionally, integrated vector management is required to ensure effective control of malaria transmission in Foumbot and Bamendjou.

Mosquito Control Based on Pesticides and Endosymbiotic Bacterium Wolbachia.

Mosquito-borne diseases, such as dengue fever and Zika, have posed a serious threat to human health around the world. Controlling vector mosquitoes is an effective method to prevent these diseases. Spraying pesticides has been the main approach of reducing mosquito population, but it is not a sustainable solution due to the growing insecticide resistance. One promising complementary method is the release of Wolbachia-infected mosquitoes into wild mosquito populations, which has been proven to be a novel and environment-friendly way for mosquito control. In this paper, we incorporate consideration of releasing infected sterile mosquitoes and spraying pesticides to aim to reduce wild mosquito populations based on the population replacement model. We present the estimations for the number of wild mosquitoes or infection density in a normal environment and then discuss how to offset the effect of the heatwave, which can cause infected mosquitoes to lose Wolbachia infection. Finally, we give the waiting time to suppress wild mosquito population to a given threshold size by numerical simulations.

'We spray and walk away': wall modifications decrease the impact of indoor residual spray campaigns through reductions in post-spray coverage.

Malaria prevalence has significantly reduced since 2000, largely due to the scale-up of vector control interventions, mainly indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLINs). Given their success, these tools remain the frontline interventions in the fight against malaria. Their effectiveness relies on three key ingredients: the intervention, the mosquito vector and the end-user. Regarding the intervention, factors such as the insecticide active ingredient(s) used and the durability and/or bio-efficacy of the tool over time are critical. For the vectors, these factors include biting and resting behaviours and the susceptibility to insecticides. Finally, the end-users need to accept and properly use the intervention. Whilst human attitude and behaviour towards LLINs are well-documented both during and after distribution, only initial coverage is monitored for IRS and in a few geographic settings the residual efficacy of the used product. Here, the historical evidence on end-users modifying their wall surfaces post-spraying is presented, a behaviour that has the potential to reduce actual IRS coverage, effectiveness and impact, as fewer people are truly protected. Therefore, clear guidelines on how to monitor IRS acceptability and/or coverage, both before, during and after spraying, are urgently needed as part of the Monitoring and Evaluation of malaria programmes.

Improving the performance of spray operators through monitoring and evaluation of insecticide concentrations of pirimiphos-methyl during indoor residual spraying for malaria control on Bioko Island.

BACKGROUND: Quality control of indoor residual spraying (IRS) is necessary to ensure that spray operators (SOs) deposit the correct concentration of insecticide on sprayed structures, while also confirming that spray records are not being falsified. METHODS: Using high-performance liquid chromatography (HPLC), this study conducted quality control of the organophosphate insecticide pirimiphos-methyl (Actellic 300CS), during the 2018 IRS round on Bioko Island, Equatorial Guinea. Approximately 60 SOs sprayed a total of 67,721 structures in 16,653 houses during the round. Houses that were reportedly sprayed were randomly selected for quality control testing. The SOs were monitored twice in 2018, an initial screening in March followed by sharing of results with the IRS management team and identification of SOs to be re-trained, and a second screening in June to monitor the effectiveness of training. Insecticide samples were adhesive-lifted from wooden and cement structures and analysed using HPLC. RESULTS: The study suggests that with adequate quality control measures and refresher training, suboptimal spraying was curtailed, with a significant increased concentration delivered to the bedroom (difference = 0.36, P < 0.001) and wooden surfaces (difference 0.41, P = 0.001). Additionally, an increase in effective coverage by SOs was observed, improving from 80.7% in March to 94.7% in June after re-training (McNemar's test; P = 0.03). CONCLUSIONS: The ability to randomly select, locate, and test houses reportedly sprayed within a week via HPLC has led to improvements in the performance of SOs on Bioko Island, enabling the project to better evaluate its own performance.

Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania.

BACKGROUND: Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania. METHODS: The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.-8 a.m.), evenings (6 p.m.-8 p.m.) and at night (11 p.m.-12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets). RESULTS: Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33-55% of An. funestus and 43-50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16-20% of An. funestus and 8-30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47-53% of An. funestus; 60-66% of An. arabiensis). CONCLUSION: While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.

Evaluation of long-lasting indoor residual spraying of deltamethrin 62.5 SC-PE against malaria vectors in India.

BACKGROUND: Deltamethrin 62.5 polymer-enhanced suspension concentrate (SC-PE) is one of the World Health Organization-approved insecticides for indoor residual spraying and was recommended to evaluate its residual activity for determination of appropriate spray cycles in different eco-epidemiologic settings. In the current study, efficacy of deltamethrin 62.5 SC-PE was evaluated against vectors of malaria and its impact on malaria incidence in a Plasmodium falciparum hyper-endemic area in Koraput district, Odisha State, India. METHODS: The trial had two comparable arms, arm 1 with residual spraying of deltamethrin 62.5 SC-PE and arm 2 with deltamethrin 2.5% WP (positive control). Comparative assessment of the impact of each intervention arm on entomological (density, parity, infection and human blood index), epidemiological (malaria incidence) parameters, residual efficacy and adverse effects were evaluated. RESULTS: Both the arms were comparable in terms of entomological and epidemiological parameters. While, deltamethrin 62.5 SC-PE was found to be effective for 150 days in mud and wood surfaces and 157 days in cement surfaces; deltamethrin 2.5% was effective only for 105 days on mud surfaces and 113 days on cement and wood surfaces. CONCLUSIONS: Deltamethrin 62.5 SC-PE had prolonged killing effectiveness up to 5 months. Hence, one round of IRS with deltamethrin 62.5 SC-PE would be sufficient to cover two existing malaria peak transmission seasons (July-August and October-November) in many parts of India.

Epidemiological risk factors for clinical malaria infection in the highlands of Western Kenya.

BACKGROUND: Understanding the complex heterogeneity of risk factors that can contribute to an increased risk of malaria at the individual and household level will enable more effective use of control measures. The objective of this study was to understand individual and household factors that influence clinical malaria infection among individuals in the highlands of Western Kenya. METHODS: This was a matched case-control study undertaken in the Western Kenya highlands. Clinical malaria cases were recruited from health facilities and matched to asymptomatic individuals from the community who served as controls. Each participant was screened for malaria using microscopy. Follow-up surveys were conducted with individual households to collect socio-economic data. The houses were also checked using pyrethrum spray catches to collect mosquitoes. RESULTS: A total of 302 malaria cases were matched to 604 controls during the surveillance period. Mosquito densities were similar in the houses of both groups. A greater percentage of people in the control group (64.6%) used insecticide-treated bed nets (ITNs) compared to the families of malaria cases (48.3%). Use of ITNs was associated with lower level of clinical malaria episodes (odds ratio 0.51; 95% CI 0.39-0.68; P < 0.0001). Low income was the most important factor associated with higher malaria infections (adj. OR 4.70). Use of malaria prophylaxis was the most important factor associated with less malaria infections (adj OR 0.36). Mother's (not fathers) employment status (adj OR 0.48) and education level (adj OR 0.54) was important malaria risk factor. Houses with open eaves was an important malaria risk factor (adj OR 1.72). CONCLUSION: The identification of risk factors for clinical malaria infection provides information on the local malaria epidemiology and has the potential to lead to a more effective and targeted use of malaria control measures. These risk factors could be used to assess why some individuals acquire clinical malaria whilst others do not and to inform how intervention could be scaled at the local level.

A reduction in malaria transmission intensity in Northern Ghana after 7 years of indoor residual spraying.

BACKGROUND: Indoor residual spraying (IRS) is being implemented as one of the malaria prevention methods in the Northern Region of Ghana. Changes in longevity, sporozoite and entomological inoculation rates (EIRs) of major malaria vectors were monitored to assess the impact of IRS in selected districts. METHODS: Monthly human landing catches (HLCs) were used to collect mosquitoes from sentinel sites in three adjacent districts between July 2009 and December 2014: Savelugu Nanton (SND) where IRS had been implemented from 2008 to 2014; Tolon Kumbungu (TKD) where IRS had been implemented between 2008 and 2012 and Tamale Metropolis (TML) with no history of IRS. Mosquitoes were morphologically identified to species level and into sibling species, using PCR. Samples of Anopheles gambiae sensu lato (s.l.) were examined for parity and infectivity. EIR was calculated from biting and infectivity rates of malaria vectors. RESULTS: Parity rates of An. gambiae s.l. decreased significantly (p < 0.0001) in SND from 44.8% in 2011 to 28.1% by 2014, and in TKD from 53.3% in 2011 to 46.6% in 2012 (p = 0.001). However 2 years after IRS was discontinued in TKD, the proportion of parous An. gambiae s.l. increased significantly to 68.5% in 2014 (p < 0.0001). Parity rates in the unsprayed district remained high throughout the study period, ranging between 68.6% in 2011 and 72.3% in 2014. The sum of monthly EIRs post-IRS season (July-December) in SND ranged between 2.1 and 6.3 infective bites/person/season (ib/p/s) during the 3 years that the district was sprayed with alphacypermethrin. EIR in SND was reduced to undetectable levels when the insecticide was switched to pirimiphos methyl CS in 2013 and 2014. Two years after IRS was withdrawn from TKD the sum of monthly EIRs (July-December) increased by about fourfold from 41.8 ib/p/s in 2012 to 154.4 ib/p/s in 2014. The EIR in the control area, TML, ranged between 35 ib/p/s in 2009 to 104.71 ib/p/s by 2014. CONCLUSIONS: This study demonstrates that IRS application did have a significant impact on entomological indicators of malaria transmission in the IRS project districts of Northern Ghana. Transmission indicators increased following the withdrawal of IRS from Tolon Kumbungu District.

Is outdoor vector control needed for malaria elimination? An individual-based modelling study.

BACKGROUND: Residual malaria transmission has been reported in many areas even with adequate indoor vector control coverage, such as long-lasting insecticidal nets (LLINs). The increased insecticide resistance in Anopheles mosquitoes has resulted in reduced efficacy of the widely used indoor tools and has been linked with an increase in outdoor malaria transmission. There are considerations of incorporating outdoor interventions into integrated vector management (IVM) to achieve malaria elimination; however, more information on the combination of tools for effective control is needed to determine their utilization. METHODS: A spatial individual-based model was modified to simulate the environment and malaria transmission activities in a hypothetical, isolated African village setting. LLINs and outdoor attractive toxic sugar bait (ATSB) stations were used as examples of indoor and outdoor interventions, respectively. Different interventions and lengths of efficacy periods were tested. Simulations continued for 420 days, and each simulation scenario was repeated 50 times. Mosquito populations, entomologic inoculation rates (EIRs), probabilities of local mosquito extinction, and proportion of time when the annual EIR was reduced below one were compared between different intervention types and efficacy periods. RESULTS: In the village setting with clustered houses, the combinational intervention of 50% LLINs plus outdoor ATSBs significantly reduced mosquito population and EIR in short term, increased the probability of local mosquito extinction, and increased the time when annual EIR is less than one per person compared to 50% LLINs alone; outdoor ATSBs alone significantly reduced mosquito population in short term, increased the probability of mosquito extinction, and increased the time when annual EIR is less than one compared to 50% LLINs alone, but there was no significant difference in EIR in short term between 50% LLINs and outdoor ATSBs. In the village setting with dispersed houses, the combinational intervention of 50% LLINs plus outdoor ATSBs significantly reduced mosquito population in short term, increased the probability of mosquito extinction, and increased the time when annual EIR is less than one per person compared to 50% LLINs alone; outdoor ATSBs alone significantly reduced mosquito population in short term, but there were no significant difference in the probability of mosquito extinction and the time when annual EIR is less than one between 50% LLIN and outdoor ATSBs; and there was no significant difference in EIR between all three interventions. A minimum of 2 months of efficacy period is needed to bring out the best possible effect of the vector control tools, and to achieve long-term mosquito reduction, a minimum of 3 months of efficacy period is needed. CONCLUSIONS: The results highlight the value of incorporating outdoor vector control into IVM as a supplement to traditional indoor practices for malaria elimination in Africa, especially in village settings of clustered houses where LLINs alone is far from sufficient.

Rotary and High-Pressure Nozzle Spray Plume Droplet Analysis For Aerially Applied Mosquito Adulticides: Laser Diffraction Characterization.

The droplet spectrum of a mosquito adulticide spray plume determines its ability to drift through the target area, impinge on the mosquito, deliver a toxic dose, and the risk of environmental contamination. This paper provides data on droplet spectra produced from 6 nozzles in a high-pressure nozzle spray system and 5 rotary nozzle systems for common mosquito adulticides. Spray plume spectra were measured by laser diffraction. High-pressure nozzles were evaluated at pressures ranging from 500 psi to 6,000 psi. Rotary nozzles were evaluated at rotational speeds ranging from 500 rpm to 24,000 rpm. Measurements were made at wind speeds of 129 km/h (80 mph) to 225 km/h (140 mph). Adulticides included were Fyfanon®, Aqua-Reslin®, Dibrom®, Duet®, Permanone®, and the inert mineral oil, Orchex® 796. High-pressure nozzles produced spray plumes within the US Environmental Protection Agency (EPA) label requirements for all configurations tested except for one at a wind speed of 225 km/h, BETE® MW125. Air speed had no significant effect on the spray plume volume median diameter (Dv(0.5)) at the speeds tested with Fyfanon®. The spray plume 90% drop volume diameter (Dv(0.9)) significantly decreased, 13% at the higher wind speed of 225 km/h. Drop size was inversely related to pressure. Dilution of the product formulations increased the Dv(0.5) of the spray plume but it did not exceed the label requirements. For the PJ15 nozzle, orientation of the nozzle into the wind of up to 135° showed a significant increase in Dv(0.5) at 500 psi, 750 psi, and 1,500 psi. The Dv(0.5) varied <5 µm over the 3 angles examined for any specific pressure. Rotary nozzles produced spray plumes within the EPA label requirements for all test configurations examined. Air speed had no significant effect on Dv(0.5) or Dv(0.9) of the plume at speeds tested with Fyfanon for the ASC A20 nozzle. The rotary AU5000 nozzle using Orchex 796 produced plumes of larger drops in all configurations than any of the rotary nozzles of similar configurations using active ingredient formulations and within EPA label requirements.

Evaluation of Three Commercial Handheld Ultra-Low-Volume Foggers with Aqualure® 20-20 Against Adult Aedes albopictus.

The Anastasia Mosquito Control District (AMCD) tests all equipment before field use to determine if machines are suitable for the needs of the district. Three handheld ultra-low-volume (ULV) foggers--the American LongRay (ULV) Fogger Model 3600B with rechargeable lithium battery (DC model), American LongRay ULV Fogger Model 3600E with 110V or 220V AC power (AC model), and Boston Fog Battery Motorized Fogger (Boston Fogger)--were compared to determine which fogger would be most suitable for use by AMCD. Mortality of caged Aedes albopictus was analyzed after 24 h to determine the success of a single application. All 3 foggers resulted in 100% mortality after 24 h using the insecticide Aqualuer 20-20 (active ingredients permethrin 20.6% and piperonyl butoxide 20.6%) 1:5 dilution with reverse osmosis water. Based on operator safety, robustness, and operational performance, the American LongRay DC model was found to be the most suitable at administering Aqualuer 20-20 against caged adult Ae. albopictus.

Evaluation of Endod (Phytolacca dodecandra: Phytolaccaceae) as a Larvicide Against Anopheles arabiensis, the Principal Vector of Malaria in Ethiopia.

Malaria control methods rely mostly on adult mosquito control using insecticide-treated nets and indoor residual spraying with insecticides. Plants such as endod (Phytolacca dodecandra) can potentially be used for the control of mosquito larvae as a supplement to adult control methods. Following the discovery of endod, a molluscicide plant, more than 5 decades ago in Ethiopia, subsequent studies have shown that its potency can further be increased by simple procedures such as aging endod berry powder in water. This study was conducted to evaluate the killing effect of fresh and aged endod solution against 4th-stage larvae of Anopheles arabiensis. Laboratory-reared An. arabiensis larvae exposed to different concentrations of endod preparation using distilled or spring water had 50% lethal concentration (LC(50))  =  49.6 ppm and 90% lethal concentration (LC(90))  =  234 ppm for fresh and LC(50)  =  36.4 ppm and LC(90)  =  115.7 ppm for the aged endod solution in distilled water against the laboratory population. Against field-collected larvae of the same species, aged preparations in habitat water resulted in higher LC(50) (472.7 ppm) and LC(90) (691 ppm) values, with only a slight improvement over fresh preparations in habitat water (LC(50)  =  456.2 ppm; LC(90)  =  896.1 ppm). In general, although aged preparations of endod required lower concentrations than fresh to kill at least 90% of the larvae, these concentrations were much higher (12-70×) than that required for schistosome-transmitting snails.

Evaluation of Alternative Methods for Testing the Bioefficacy of Household Ambient Insecticide Products Against Aedes albopictus.

Ambient insecticides are receiving increasing attention in many developed countries because of their value in reducing mosquito nuisance. As required by the European Union Biocidal Products Regulation 528/2012, these devices require appropriate testing of their efficacy, which is based on estimating the knockdown and mortality rates of free-flying (free) mosquitoes in a test room. However, evaluations using free mosquitoes present many complexities. The performances of 6 alternative methods with mosquitoes held in 2 different cage designs (steel wire and gauze/plastic) with and without an operating fan for air circulation were monitored in a test room through a closed-circuit television system and were compared with the currently recommended method using free mosquitoes. Results for caged mosquitoes without a fan showed a clearly delayed knockdown effect, whereas outcomes for caged mosquitoes with a fan recorded higher mortality at 24 h, compared to free mosquitoes. Among the 6 methods, cages made of gauze and plastic operating with fan wind speed at 2.5-2.8 m/sec was the only method without a significant difference in results for free mosquitoes, and therefore appears as the best alternative to assess knockdown by ambient insecticides accurately.

The impact of pyrethroid resistance on the efficacy of insecticide-treated bed nets against African anopheline mosquitoes: systematic review and meta-analysis.

BACKGROUND: Pyrethroid insecticide-treated bed nets (ITNs) help contribute to reducing malaria deaths in Africa, but their efficacy is threatened by insecticide resistance in some malaria mosquito vectors. We therefore assessed the evidence that resistance is attenuating the effect of ITNs on entomological outcomes. METHODS AND FINDINGS: We included laboratory and field studies of African malaria vectors that measured resistance at the time of the study and used World Health Organization-recommended impregnation regimens. We reported mosquito mortality, blood feeding, induced exophily (premature exit of mosquitoes from the hut), deterrence, time to 50% or 95% knock-down, and percentage knock-down at 60 min. Publications were searched from 1 January 1980 to 31 December 2013 using MEDLINE, Cochrane Central Register of Controlled Trials, Science Citation Index Expanded, Social Sciences Citation Index, African Index Medicus, and CAB Abstracts. We stratified studies into three levels of insecticide resistance, and ITNs were compared with untreated bed nets (UTNs) using the risk difference (RD). Heterogeneity was explored visually and statistically. Included were 36 laboratory and 24 field studies, reported in 25 records. Studies tested and reported resistance inconsistently. Based on the meta-analytic results, the difference in mosquito mortality risk for ITNs compared to UTNs was lower in higher resistance categories. However, mortality risk was significantly higher for ITNs compared to UTNs regardless of resistance. For cone tests: low resistance, risk difference (RD) 0.86 (95% CI 0.72 to 1.01); moderate resistance, RD 0.71 (95% CI 0.53 to 0.88); high resistance, RD 0.56 (95% CI 0.17 to 0.95). For tunnel tests: low resistance, RD 0.74 (95% CI 0.61 to 0.87); moderate resistance, RD 0.50 (95% CI 0.40 to 0.60); high resistance, RD 0.39 (95% CI 0.24 to 0.54). For hut studies: low resistance, RD 0.56 (95% CI 0.43 to 0.68); moderate resistance, RD 0.39 (95% CI 0.16 to 0.61); high resistance, RD 0.35 (95% CI 0.27 to 0.43). However, with the exception of the moderate resistance category for tunnel tests, there was extremely high heterogeneity across studies in each resistance category (chi-squared test, p<0.00001, I² varied from 95% to 100%). CONCLUSIONS: This meta-analysis found that ITNs are more effective than UTNs regardless of resistance. There appears to be a relationship between resistance and the RD for mosquito mortality in laboratory and field studies. However, the substantive heterogeneity in the studies' results and design may mask the true relationship between resistance and the RD, and the results need to be interpreted with caution. Our analysis suggests the potential for cumulative meta-analysis in entomological trials, but further field research in this area will require specialists in the field to work together to improve the quality of trials, and to standardise designs, assessment, and reporting of both resistance and entomological outcomes.

Updated distribution of Aedes albopictus (Diptera: Culicidae) in Spain: new findings in the mainland Spanish Levante, 2013.

In 2004, Aedes (Stegomyia) albopictus (Skuse, 1894) was observed for the first time in Catalonia, northeastern Spain. A decade later, it has spread throughout the eastern Mediterranean region of the country and the Balearic Islands. Framed within a national surveillance project, we present the results of monitoring in 2013 in the autonomous communities of the mainland Levante. The current study reveals a remarkable increase in the spread of the invasive mosquito in relation to results from 2012; the species was present and well-established in 48 municipalities, most of which were along the Mediterranean coastline from the Valencian Community to the Region of Murcia.

Updating the geographical distribution and frequency of Aedes albopictus in Brazil with remarks regarding its range in the Americas.

The geographical distribution of Aedes albopictus in Brazil was updated according to the data recorded across the country over the last eight years. Countrywide house indexes (HI) for Ae. albopictus in urban and suburban areas were described for the first time using a sample of Brazilian municipalities. This mosquito is currently present in at least 59% of the Brazilian municipalities and in 24 of the 27 federal units (i.e., 26 states and the Federal District). In 34 Brazilian municipalities, the HI values for Ae. albopictus were higher than those recorded for Ae. aegypti, reaching figures as high as HI = 7.72 in the Southeast Region. Remarks regarding the current range of this mosquito species in the Americas are also presented. Nineteen American countries are currently infested and few mainland American countries have not confirmed the occurrence of Ae. albopictus. The large distribution and high frequency of Ae. albopictus in the Americas may become a critical factor in the spread of arboviruses like chikungunya in the new world.

Glucosinolate from leaf of Solanum nigrum L. (Solanaceae) as a new mosquito larvicide.

The present study was carried out to investigate the biocontrol potentiality of active ingredient isolated from ethyl acetate extract of mature leaves of Solanum nigrum L. (Solanaceae) against the larval form of Culex quinquefasciatus Say. Mortality rate at a concentration of 25 mg/L of the active compound was highest (P < 0.05) amongst all tested concentrations. Result of log-probit analysis (at 95% confidence level) revealed that LC50 and LC90 values are inversely proportional to exposure period of bioassay. A clear dose-dependent mortality was observed, as the rate of mortality (Y) was positively correlated with the concentrations of the compound (X); having regression coefficient value close to 1. The compound was found to be ecofriendly as it did not show any adverse effect to the studied nontarget organisms. Chemical characterization of the active ingredient was also carried out by infrared spectroscopic analysis (IR), mass analyses (GC-MS) and carbon-hydrogen-nitrogen-sulphur analyses (CHNS), that revealed the presence of a glucosinolate compound [1-thio-ß-D-glucopyranose-1-[(R)-3-hydroxy-2-ethyl-N-hydroxysulfonyloxy propanimidate] having the molecular formula of C11H21NO10S2.

Evaluation of plant-mediated synthesized silver nanoparticles against vector mosquitoes.

Diseases transmitted by blood-feeding mosquitoes, such as dengue fever, dengue hemorrhagic fever, Japanese encephalitis, malaria, and filariasis, are increasing in prevalence, particularly in tropical and subtropical zones. To control mosquitoes and mosquito-borne diseases, which have worldwide health and economic impacts, synthetic insecticide-based interventions are still necessary, particularly in situations of epidemic outbreak and sudden increases of adult mosquitoes. Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Heliotropium indicum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. Adult mosquitoes were exposed to varying concentrations of aqueous extract of H. indicum and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of H. indicum, and the formation of nanoparticles was observed within 6 h. The results recorded from UV-vis spectrum, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the adult of A. stephensi (lethal dose (LD)50 = 26.712 µg/mL; LD90 = 49.061 µg/mL), A. aegypti (LD50 = 29.626 µg/mL; LD90 = 54.269 µg/mL), and C. quinquefasciatus (LD50 = 32.077 µg/mL; LD90 = 58.426 µg/mL), respectively. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H.indicum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.