Field comparison of broad-spectrum white LED-baited traps with narrow-spectrum green LED-baited traps in the capture of Anopheles mosquitoes (Diptera: Culicidae)

Light-Emitting Diodes (LEDs) have been effective light sources in attracting Anopheles mosquitoes, but the broad-spectrum white light, even with a wide-ranging application in lighting, have not been evaluated yet. In this study, the white light was field evaluated against the green one in the light trapping of anopheline mosquitoes by using two non-suction Silva traps and two CDC-type suction light traps. Anopheline mosquitoes were captured for two 21-night periods of collecting (2022 and 2023). In the first period, two LEDs were used per Silva trap, but three were used in the second one to increase the luminance/illuminance at traps. A CDC-type suction light trap equipped with an incandescent lamp was used in 2022 and a CDC-type suction light trap equipped with a 6 V-white light (higher luminance/illuminance) in 2023. A total of eight species and 3,289 specimens were captured in both periods. The most frequent species were Anopheles triannulatus s.l., An. goeldii, An. evansae and An. argyritarsis. In 2022, white LEDs were less attractive to anopheline mosquitoes than the other light sources, but without statistical difference among treatments (F = 2.703; P = 0.0752; df = 2). In 2023, even with an increased luminance/illuminance at traps, no statistical difference was found between the two LED-baited Silva traps (F = 6.690; P = 0.0024; df = 2), but rather between the 6 V-white-baited CDC-type suction light trap and green-baited Silva traps. Due to some drawbacks and the lower abundance of individuals caught by using white LEDs, the narrow-banded green LEDs is preferable to white ones for attracting anophelines.

Effect of Different Wall Surface Coverage With Deltamethrin-Treated Netting on the Reduction of Indoor-Biting Anopheles Mosquitoes (Diptera: Culicidae)

Indoor residual spray with deltamethrin remains the most common tool for reducing malaria transmission in Thailand. Deltamethrin is commonly used to spray the entire inner surfaces of the walls to prevent mosquitoes from resting. This study compared the mosquito landing responses on humans inside three experimental huts treated with deltamethrin at three different extents of wall coverage (25%, 50%, and full coverage), with one clean/untreated hut serving as a control. There were no significant differences between the numbers of Anopheles mosquitoes landing in the 50% and full coverage huts, whereas, in comparison to both of these, there was a significantly greater number landing in the 25% coverage hut. This study demonstrates that varying the percent coverage of indoor surfaces with deltamethrin-treated netting influences the blood-feeding success of wild Anopheles, and our findings suggest that it may be possible to reduce the extent of insecticide surface treatment while maintaining equivalent mosquito avoidance action to that seen in fully treated structures.

Comparative Efficacy of Commercial Liquid and Mat-Type Electric Vaporizer Insecticides Against Asian Tiger Mosquito (Diptera: Culicidae)

Mat and liquid-type electric insecticide vaporizers continuously emit insecticides into the surrounding air. Because both the target insects, mostly mosquitoes, and humans are exposed to those insecticides, it is crucial to understand and monitor their deposition and spatial distribution in treated areas. In the current study, we examined the evaporation of insecticides from seven commercial liquid and mat vaporizers and measured their knock-down and insecticidal activity against the adult females of the Asian tiger mosquito, Aedes albopictus (Skuse). Electric vaporizers from three manufactures had differences in their heaters and active ingredients. Most had continued evaporation during hourly and daily monitoring; however, some liquid vaporizers failed to continue emission to their designated end periods. Overall, mosquitoes located at the upper position in a Peet-Grady chamber and in a field-simulation room exhibited faster knock-down activity than did mosquitoes in other areas, indicating that the insecticides accumulated on the ceiling area. Although most of mat and liquid vaporizers had <60 min of average KT90 values when tested in the Peet-Grady chamber (1.8 × 1.8 × 1.8 m), they failed to have any knock-down in 2 h of observation in the field-simulation room (6.8 × 3.4 × 2.7 m) but showed 72. 8 ± 11.7% and 56. 7 ± 7.3% knock-down in the mat and liquid vaporizers, respectively, in 3 h of operation. Further study will be required to examine whether this relatively limited efficacy can be compensated by other physiological and behavioral effects, including disruption in host-seeking or blood-sucking activities.

Efficacy of targeted indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-resistant Aedes aegypti

Background

There is an increased need to mitigate the emergence of insecticide resistance and incorporate new formulations and modes of application to control the urban vector Aedes aegypti. Most research and development of insecticide formulations for the control of Ae. aegypti has focused on their peridomestic use as truck-mounted ULV-sprays or thermal fogs despite the widespread knowledge that most resting Ae. aegypti are found indoors. A recent modification of indoor residual spraying (IRS), termed targeted IRS (TIRS) works by restricting applications to 1.5 m down to the floor and on key Ae. aegypti resting sites (under furniture). TIRS also opens the possibility of evaluating novel residual insecticide formulations currently being developed for malaria IRS.

Methods

We evaluated the residual efficacy of chlorfenapyr, formulated as Sylando 240SC, for 12 months on free-flying field-derived pyrethroid-resistant Ae. aegypti using a novel experimental house design in Merida, Mexico. On a monthly basis, 600 female Ae. aegypti were released into the houses and left indoors with access to sugar solution for 24 hours. After the exposure period, dead and alive mosquitoes were counted in houses treated with chlorfenapyr as well as untreated control houses to calculate 24-h mortality. An evaluation for these exposed cohorts of surviving mosquitoes was extended up to seven days under laboratory conditions to quantify “delayed mortality”.

Results

Mean acute (24-h) mortality of pyrethroid-resistant Ae. aegypti ranged 80–97% over 5 months, dropping below 30% after 7 months post-TIRS. If delayed mortality was considered (quantifying mosquito mortality up to 7 days after exposure), residual efficacy was above 90% for up to 7 months post-TIRS application. Generalized Additive Mixed Models quantified a residual efficacy of chlorfenapyr of 225 days (ca. 7.5 months).

Conclusions

Chlorfenapyr represents a new option for TIRS control of Ae. aegypti in urban areas, providing a highly-effective time of protection against indoor Ae. aegypti females of up to 7 months.

Vector control (VC) for managing Aedes aegypti and reducing transmission of Aedes-borne diseases is largely focused on peridomestic insecticide applications. However, the indoor resting behavior of Ae. aegypti and the acceleration of insecticide resistance owed to reduced modes of action have diminished the effectiveness of many VC tools. A targeted Indoor residual spraying (TIRS) modality in experimental housing units was employed to investigate the potential of chlorfenapyr, a pyrrole-class insecticide with known effectiveness to resistant mosquito species. This was the first investigation for chlorfenapyr use against locally resistant Ae. aegypti (Merida, Mexico) with this approach. Two treatment arms were investigated in the present study: TIRS and a control house where only water was sprayed. A comparison of entomological efficacy for TIRS applied to interior perimeter walls below 1.5 m with chlorfenapyr (formulated as Sylando 240SC) at 250 mg/m² over 12 months was assessed. TIRS chlorfenapyr treatments were highly efficacious and led to acute mortalities (after 24 exposure) above 80% up to 5 months; delayed mortalities (to Ae. aegypti) were monitored over seven days post exposures vs untreated controls. When delayed mortality was considered, residual efficacy of chlorfenapyr extended to 7 months. These data provide evidence that TIRS chlorfenapyr is an effective Aedes management tool that surpassed efficacy profiles for other TIRS insecticides that have been previously reported with this method. Further, Chlorfenapyr emerges as a novel addition to Ae. aegypti VC, and future studies should focus on its effectiveness and residual power as part of Phase II-III TIRS trials.

Sterile Insect Technique: Lessons From the Past

When E.F. Knipling conceived of the release of sexually sterile insects to suppress wild populations, he laid down several fundamental qualities that characterized suitable target species-some of which mosquitoes generally violate-including high reproductive rates and large population numbers. Regardless of this, their global importance in public health has led numerous research teams to attempt to use the mosquito sterile insect technique against several species. Because of the degree of financial commitment required for suppression programs, most releases have consisted of preliminary investigations of male performance, population characteristics, and production methods. Those that have accomplished suppression provide important insights regarding the challenges of production, dispersal, and immigration. Insights gained from these studies remain relevant today, regardless of the genetic control technology being applied. In this article, I highlight studies that were notable for the insights that were gained, the intrinsic difficulties that mosquitoes present, and synthesize these into recommendations for successful applications of the sterile insect technique and newer technologies to mosquitoes.

Evaluation of a mosquito home system for controlling Aedes aegypti

BACKGROUND

Dengue is a significant public health issue that is caused by Aedes spp. mosquitoes. The current vector control methods are unable to effectively reduce Aedes populations and thus fail to decrease dengue transmission. Hence, there is an urgent need for new tools and strategies to reduce dengue transmission in a wide range of settings. In this study, the Mosquito Home System (MHS) and Mosquito Home Aqua (MHAQ) formulations were assessed as commercial autodissemination traps in laboratory and small-scale field trials.

METHOD

Multiple series of laboratory and small-scale field trials were performed to assess the efficacy of MHS and MHAQ exposed to Ae. aegypti. In the laboratory trials, various parameters such as fecundity, fertility, wing size, oviposition preferences, residual effects, and MHAQ transference to other containers through controlled experiments were tested. For small-scale field trials, the efficacy of the MHS and MHAQ approaches was determined to ascertain whether wild mosquitoes could transfer the MHAQ formulation from MHS stations to ovitraps.

RESULTS

The data revealed that Ae. aegypti was highly susceptible to low concentrations of MHAQ formulations and had a residual effect of up to 3 months, with MHAQ exposure affecting fecundity, fertility, and mosquito wing size. In the oviposition studies, gravid females strongly preferred the hay infusion compared to tap water and MHAQ during egg-laying in the laboratory. Nevertheless, the use of commercial MHAQ by MHS was highly attractive in field settings compared to conventional ovitraps among local Aedes spp. mosquitoes. In addition, MHAQ horizontal transfer activities in the laboratory and small-scale field trials were demonstrated through larval bioassays. These findings demonstrated the potential of MHAQ to be transferred to new containers in each study site.

CONCLUSION

This study provided proof of principle for the autodissemination of MHAQ. Through further refinement, this technique and device could become an effective oviposition trap and offer an alternative preventive tool for vector control management.

Assessment of Trinidad community stakeholder perspectives on the use of yeast interfering RNA-baited ovitraps for biorational control of Aedes mosquitoes

Dengue, Zika, chikungunya and yellow fever viruses continue to be a major public health burden. Aedes mosquitoes, the primary vectors responsible for transmitting these viral pathogens, continue to flourish due to local challenges in vector control management. Yeast interfering RNA-baited larval lethal ovitraps are being developed as a novel biorational control tool for Aedes mosquitoes. This intervention circumvents increasing issues with insecticide resistance and poses no known threat to non-target organisms. In an effort to create public awareness of this alternative vector control strategy, gain stakeholder feedback regarding product design and acceptance of the new intervention, and build capacity for its potential integration into existing mosquito control programs, this investigation pursued community stakeholder engagement activities, which were undertaken in Trinidad and Tobago. Three forms of assessment, including paper surveys, community forums, and household interviews, were used with the goal of evaluating local community stakeholders' knowledge of mosquitoes, vector control practices, and perceptions of the new technology. These activities facilitated evaluation of the hypothesis that the ovitraps would be broadly accepted by community stakeholders as a means of biorational control for Aedes mosquitoes. A comparison of the types of stakeholder input communicated through use of the three assessment tools highlighted the utility and merit of using each tool for assessing new global health interventions. Most study participants reported a general willingness to purchase an ovitrap on condition that it would be affordable and safe for human health and the environment. Stakeholders provided valuable input on product design, distribution, and operation. A need for educational campaigns that provide a mechanism for educating stakeholders about vector ecology and management was highlighted. The results of the investigation, which are likely applicable to many other Caribbean nations and other countries with heavy arboviral disease burdens, were supportive of supplementation of existing vector control strategies through the use of the yeast RNAi-based ovitraps.

Indoor residual spraying practices against Triatoma infestans in the Bolivian Chaco: contributing factors to suboptimal insecticide delivery to treated households

BACKGROUND

Indoor residual spraying (IRS) of insecticides is a key method to reduce vector transmission of Trypanosoma cruzi, causing Chagas disease in a large part of South America. However, the successes of IRS in the Gran Chaco region straddling Bolivia, Argentina, and Paraguay, have not equalled those in other Southern Cone countries.

AIMS

This study evaluated routine IRS practices and insecticide quality control in a typical endemic community in the Bolivian Chaco.

METHODS

Alpha-cypermethrin active ingredient (a.i.) captured onto filter papers fitted to sprayed wall surfaces, and in prepared spray tank solutions, were measured using an adapted Insecticide Quantification Kit (IQK™) validated against HPLC quantification methods. The data were analysed by mixed-effects negative binomial regression models to examine the delivered insecticide a.i. concentrations on filter papers in relation to the sprayed wall heights, spray coverage rates (surface area / spray time [m2/min]), and observed/expected spray rate ratios. Variations between health workers and householders' compliance to empty houses for IRS delivery were also evaluated. Sedimentation rates of alpha-cypermethrin a.i. post-mixing of prepared spray tanks were quantified in the laboratory.

RESULTS

Substantial variations were observed in the alpha-cypermethrin a.i. concentrations delivered; only 10.4% (50/480) of filter papers and 8.8% (5/57) of houses received the target concentration of 50 mg ± 20% a.i./m2. The delivered concentrations were not related to those in the matched spray tank solutions. The sedimentation of alpha-cypermethrin a.i. in the surface solution of prepared spray tanks was rapid post-mixing, resulting in a linear 3.3% loss of a.i. content per minute and 49% loss after 15 min. Only 7.5% (6/80) of houses were sprayed at the WHO recommended rate of 19 m2/min (± 10%), whereas 77.5% (62/80) were sprayed at a lower than expected rate. The median a.i. concentration delivered to houses was not significantly associated with the observed spray coverage rate. Householder compliance did not significantly influence either the spray coverage rates or the median alpha-cypermethrin a.i. concentrations delivered to houses.

CONCLUSIONS

Suboptimal delivery of IRS is partially attributable to the insecticide physical characteristics and the need for revision of insecticide delivery methods, which includes training of IRS teams and community education to encourage compliance. The IQK™ is a necessary field-friendly tool to improve IRS quality and to facilitate health worker training and decision-making by Chagas disease vector control managers.

Semi-field evaluation of the exposure-free mosquito electrocuting trap and BG-Sentinel trap as an alternative to the human landing catch for measuring the efficacy of transfluthrin emanators against Aedes aegypti

BACKGROUND

The human landing catch (HLC) measures human exposure to mosquito bites and evaluates the efficacy of vector control tools. However, it may expose volunteers to potentially infected mosquitoes. The mosquito electrocuting trap (MET) and BG-Sentinel traps (BGS) represent alternative, exposure-free methods for sampling host-seeking mosquitoes. This study investigates whether these methods can be effectively used as alternatives to HLC for measuring the efficacy of transfluthrin emanator against Aedes aegypti.

METHODS

The protective efficacy (PE) of freestanding passive transfluthrin emanators (FTPEs), measured by HLC, MET and BGS, was compared in no-choice and choice tests. The collection methods were conducted 2 m from an experimental hut with FTPEs positioned at 3 m on either side of them. For the choice experiment, a competitor HLC was included 10 m from the first collection point. One hundred laboratory-reared Ae. aegypti mosquitoes were released and collected for 3 consecutive h.

RESULTS

In the no-choice test, each method measured similar PE: HLC: 66% (95% confidence interval [CI]: 50-82), MET: 55% (95% CI: 48-63) and BGS: 64% (95% CI: 54-73). The proportion of mosquitoes recaptured was consistent between methods (20-24%) in treatment and varied (47-71%) in the control. However, in choice tests, the PE measured by each method varied: HLC: 37% (95% CI: 25-50%), MET: 76% (95% CI: 61-92) and BGS trap: 0% (95% CI: 0-100). Recaptured mosquitoes were no longer consistent between methods in treatment (2-26%) and remained variable in the control (7-42%). FTPE provided 50% PE to the second HLC 10 m away. In the control, the MET and the BGS were less efficacious in collecting mosquitoes in the presence of a second HLC.

CONCLUSIONS

Measuring the PE in isolation was fairly consistent for HLC, MET and BGS. Because HLC is not advisable, it is reasonable to use either MET or BGS as a proxy for HLC for testing volatile pyrethroid (VP) in areas of active arbovirus-endemic areas. The presence of a human host in close proximity invalidated the PE estimates from BGS and METs. Findings also indicated that transfluthrin can protect multiple people in the peridomestic area and that at short range mosquitoes select humans over the BGS.

Semi-field assessment of the Gravid Aedes Trap (GAT) with the aim of controlling Aedes (Stegomyia) aegypti populations

The mosquito Aedes aegypti is the main vector of arboviroses and current approaches to control this vector are not sufficiently effective. Adult traps, such as the BG-Sentinel (BGS), have been successfully used for mosquito surveillance and can also suppress vector populations. A new “passive” trap for gravid Ae. aegypti (Gravid Aedes Trap—GAT) has been shown efficient for Aedes collection and suppress Ae. albopictus populations using mass trapping techniques. Here the GAT was evaluated for the first time as a new tool to control Ae. aegypti in semi-field conditions using simulated outdoor environments (SOE). Two identical large screened chambers inside of a SOE containing different numbers and sizes of artificial breeding sites were used to assess the trapping efficiency of the GAT. One hundred mosquitoes were released into the chambers, and recapture rates evaluated after 48h. The parity status of the captured mosquitoes was also recorded. The number of eggs laid, and breeding productivity were also monitored when using different numbers and sizes of breeding sites. The BGS trap was used here as a control (gold standard) trap to compare capture rates to those of the GAT. The GAT recaptured between 50–65% of the mosquitoes independent of the number and sizes of the breeding sites in the SOEs, whereas the BGS recaptured 60–82% of the females. Both traps showed similar results regarding to the parity status of recaptured mosquitoes. Our results confirmed the effectiveness of GAT for the capture of adult female Ae. aegypti in simulated field environments. The BGS trap recaptured gravid Ae. aegypti before egg-laying in different sizes and number of breading sites, whereas the oviposition activity occurred prior to recapture mosquitoes in the GAT. Based on the results, we believe that GAT is a promising candidate for mass-trapping intervention in urban settings, but a source reduction intervention should be made prior trap deployment. Therefore, we suggest future field studies to confirm the use of GAT as a complementary tool in vector control activities.

New traps for the capture of Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) (Diptera: Culicidae) eggs and adults

The control of arboviruses carried by Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) can be performed with tools that monitor and reduce the circulation of these vectors. Therefore, the efficiency of four types of traps in capturing A. aegypti and A. albopictus eggs and adults, with the biological product Vectobac WG, was evaluated in the field. For this, 20 traps were installed in two locations, which were in the South (Londrina, Paraná) and North (Manaus, Amazonas) Regions of Brazil, from March to April 2017 and January to February 2018, respectively. The UELtrap-E (standard trap) and UELtrap-EA traps captured A. aegypti and A. albopictus eggs: 1703/1866 eggs in Londrina, and 10268/2149 eggs in Manaus, respectively, and presented high ovitraps positivity index (OPI) values (averages: 100%/100% in Londrina, and 100%/96% in Manaus, respectively); and high egg density index (EDI) values (averages: 68/75 in Londrina, and 411/89 in Manaus, respectively), so they had statistically superior efficiency to that of the CRtrap-E and CRtrap-EA traps in both regions, that captured less eggs and adults: 96/69 eggs in Londrina, and 1091/510 eggs in Manaus, respectively. Also presented lower OPI values (averages: 28%/4% in Londrina, and 88%/60% in Manaus, respectively); and lower EDI values (averages: 10.5/9 in Londrina, and 47/30 in Manaus, respectively). The capture ratios of Aedes adults in the UELtrap-EA and CRtrap-EA traps in Londrina and Manaus were 53.3%/29.5% and 0%/9.8%, respectively. UELtrap-EA can be adopted as efficient tool for Aedes monitoring due to their high sensitivity, low cost and ease of use.

Systematic identification of plausible pathways to potential harm via problem formulation for investigational releases of a population suppression gene drive to control the human malaria vector Anopheles gambiae in West Africa

BACKGROUND

Population suppression gene drive has been proposed as a strategy for malaria vector control. A CRISPR-Cas9-based transgene homing at the doublesex locus (dsxFCRISPRh) has recently been shown to increase rapidly in frequency in, and suppress, caged laboratory populations of the malaria mosquito vector Anopheles gambiae. Here, problem formulation, an initial step in environmental risk assessment (ERA), was performed for simulated field releases of the dsxFCRISPRh transgene in West Africa.

METHODS

Building on consultative workshops in Africa that previously identified relevant environmental and health protection goals for ERA of gene drive in malaria vector control, 8 potentially harmful effects from these simulated releases were identified. These were stratified into 46 plausible pathways describing the causal chain of events that would be required for potential harms to occur. Risk hypotheses to interrogate critical steps in each pathway, and an analysis plan involving experiments, modelling and literature review to test each of those risk hypotheses, were developed.

RESULTS

Most potential harms involved increased human (n = 13) or animal (n = 13) disease transmission, emphasizing the importance to subsequent stages of ERA of data on vectorial capacity comparing transgenics to non-transgenics. Although some of the pathways (n = 14) were based on known anatomical alterations in dsxFCRISPRh homozygotes, many could also be applicable to field releases of a range of other transgenic strains of mosquito (n = 18). In addition to population suppression of target organisms being an accepted outcome for existing vector control programmes, these investigations also revealed that the efficacy of population suppression caused by the dsxFCRISPRh transgene should itself directly affect most pathways (n = 35).

CONCLUSIONS

Modelling will play an essential role in subsequent stages of ERA by clarifying the dynamics of this relationship between population suppression and reduction in exposure to specific potential harms. This analysis represents a comprehensive identification of plausible pathways to potential harm using problem formulation for a specific gene drive transgene and organism, and a transparent communication tool that could inform future regulatory studies, guide subsequent stages of ERA, and stimulate further, broader engagement on the use of population suppression gene drive to control malaria vectors in West Africa.

Spatio-temporal impacts of aerial adulticide applications on populations of West Nile virus vector mosquitoes

BACKGROUND

Aerial applications of insecticides that target adult mosquitoes are widely used to reduce transmission of West Nile virus to humans during periods of epidemic risk. However, estimates of the reduction in abundance following these treatments typically focus on single events, rely on pre-defined, untreated control sites and can vary widely due to stochastic variation in population dynamics and trapping success unrelated to the treatment.

METHODS

To overcome these limitations, we developed generalized additive models fitted to mosquito surveillance data collected from CO2-baited traps in Sacramento and Yolo counties, California from 2006 to 2017. The models accounted for the expected spatial and temporal trends in the abundance of adult female Culex (Cx.) tarsalis and Cx. pipiens in the absence of aerial spraying. Estimates for the magnitude of deviation from baseline abundance following aerial spray events were obtained from the models.

RESULTS

At 1-week post-treatment with full spatial coverage of the trapping area by pyrethroid or pyrethrin products, Cx. pipiens abundance was reduced by a mean of 52.4% (95% confidence intrval [CI] - 65.6, - 36.5%) while the use of at least one organophosphate pesticide resulted in a mean reduction of 76.2% (95% CI - 82.8, - 67.9%). For Cx. tarsalis, at 1-week post-treatment with full coverage there was a reduction in abundance of 30.7% (95% CI - 54.5, 2.5%). Pesticide class was not a significant factor contributing to the reduction. In comparison, repetition of spraying over three to four consecutive weeks resulted in similar estimates for Cx. pipiens and estimates of somewhat smaller magnitude for Cx. tarsalis.

CONCLUSIONS

Aerial adulticides are effective for achieving a rapid short-term reduction of the abundance of the primary West Nile virus vectors, Cx. tarsalis and Cx. pipiens. A larger magnitude of reduction was estimated in Cx. pipiens, possibly due to the species' focal distribution. Effects of aerial sprays on Cx. tarsalis populations are likely modulated by the species' large dispersal ability, population sizes and vast productive larval habitat present in the study area. Our modeling approach provides a new way to estimate effects of public health pesticides on vector populations using routinely collected observational data and accounting for spatio-temporal trends and contextual factors like weather and habitat. This approach does not require pre-selected control sites and expands upon past studies that have focused on the effects of individual aerial treatment events.

Assessing the impact of low-technology emanators alongside long-lasting insecticidal nets to control malaria

Malaria control in sub-Saharan Africa relies on the widespread use of long-lasting insecticidal nets (LLINs) or the indoor residual spraying of insecticide. Disease transmission may be maintained even when these indoor interventions are universally used as some mosquitoes will bite in the early morning and evening when people are outside. As countries seek to eliminate malaria, they can target outdoor biting using new vector control tools such as spatial repellent emanators, which emit airborne insecticide to form a protective area around the user. Field data are used to incorporate a low-technology emanator into a mathematical model of malaria transmission to predict its public health impact across a range of scenarios. Targeting outdoor biting by repeatedly distributing emanators alongside LLINs increases the chance of elimination, but the additional benefit depends on the level of anthropophagy in the local mosquito population, emanator effectiveness and the pre-intervention proportion of mosquitoes biting outdoors. High proportions of pyrethroid-resistant mosquitoes diminish LLIN impact because of reduced mosquito mortality. When mosquitoes are highly anthropophagic, this reduced mortality leads to more outdoor biting and a reduced additional benefit of emanators, even if emanators are assumed to retain their effectiveness in the presence of pyrethroid resistance. Different target product profiles are examined, which show the extra epidemiological benefits of spatial repellents that induce mosquito mortality. This article is part of the theme issue 'Novel control strategies for mosquito-borne diseases'.

Control of malaria-transmitting mosquitoes using gene drives

Gene drives are selfish genetic elements that can be re-designed to invade a population and they hold tremendous potential for the control of mosquitoes that transmit disease. Much progress has been made recently in demonstrating proof of principle for gene drives able to suppress populations of malarial mosquitoes, or to make them refractory to the Plasmodium parasites they transmit. This has been achieved using CRISPR-based gene drives. In this article, I will discuss the relative merits of this type of gene drive, as well as barriers to its technical development and to its deployment in the field as malaria control. This article is part of the theme issue 'Novel control strategies for mosquito-borne diseases'.

Novel control strategies for mosquito-borne diseases

Mosquito-borne diseases are an increasing global health challenge, threatening over 40% of the world's population. Despite major advances in malaria control since 2000, recent progress has stalled. Additionally, the risk of Aedes-borne arboviruses is rapidly growing, with the unprecedented spread of dengue and chikungunya viruses, outbreaks of yellow fever and the 2015 epidemic of Zika virus in Latin America. To counteract this growing problem, diverse and innovative mosquito control technologies are currently under development. Conceptually, these span an impressive spectrum of approaches, from invasive transgene cassettes with the potential to crash mosquito populations or reduce the vectorial capacity of a population, to low-cost alterations in housing design that restrict mosquito entry. This themed issue will present articles providing insight into the breadth of mosquito control research, while demonstrating the requirement for an interdisciplinary approach. The issue will highlight mosquito control technologies at varying stages of development and includes both opinion pieces and research articles with laboratory and field-based data on control strategy development. This article is part of the theme issue 'Novel control strategies for mosquito-borne diseases'.

Outcomes from international field trials with Male Aedes Sound Traps: Frequency-dependent effectiveness in capturing target species in relation to bycatch abundance

Aedes aegypti and Aedes albopictus vector dengue, chikungunya and Zika viruses. With both species expanding their global distributions at alarming rates, developing effective surveillance equipment is a continuing priority for public health researchers. Sound traps have been shown, in limited testing, to be highly species-specific when emitting a frequency corresponding to a female mosquito wingbeat. Determining male mosquito capture rates in sound traps based on lure frequencies in endemic settings is the next step for informed deployment of these surveillance tools. We field-evaluated Male Aedes Sound Traps (MASTs) set to either 450 Hz, 500 Hz, 550 Hz or 600 Hz for sampling Aedes aegypti and/or Aedes albopictus and compared catch rates to BG-Sentinel traps within Pacific (Madang, Papua New Guinea) and Latin American (Molas, Mexico and Orange Walk Town, Belize) locations. MASTs set to 450-550 Hz consistently caught male Ae. aegypti at rates comparable to BG-Sentinel traps in all locations. A peak in male Ae. albopictus captures in MASTs set at 550 Hz was observed, with the lowest mean abundance recorded in MASTs set to 450 Hz. While significantly higher abundances of male Culex were sampled in MASTs emitting lower relative frequencies in Molas, overall male Culex were captured in significantly lower abundances in the MASTs, relative to BG-Sentinel traps within all locations. Finally, significant differences in rates at which male Aedes and Culex were positively detected in trap-types per weekly collections were broadly consistent with trends in abundance data per trap-type. MASTs at 550 Hz effectively captured both male Ae. aegypti and Ae. albopictus while greatly reducing bycatch, especially male Culex, in locations where dengue transmission has occurred. This high species-specificity of the MAST not only reduces staff-time required to sort samples, but can also be exploited to develop an accurate smart-trap system-both outcomes potentially reducing public health program expenses.

A Low-Powered and Highly Selective Trap for Male Aedes (Diptera: Culicidae) Surveillance: The Male Aedes Sound Trap

As Aedes aegypti (Linnaeus, Diptera: Culicidae) expands its global distribution and vectors a range of debilitating arboviruses there is an increased need for enhanced mosquito surveillance. Consequently, we developed a Male Aedes Sound Trap (MAST) that requires minimal power and is highly species-specific. Two different versions of the MAST were developed, one that uses synthetic pyrethroid to kill captured mosquitoes (MAST Spray) and another which has an internal divider to create a killing chamber in which a sticky panel can be placed to capture mosquitoes (MAST Sticky). We compared weekly capture rates of male Ae. aegypti and bycatch from the two MAST versions to those from BG-Sentinel (BGS) traps and Sound-producing BG-Gravid Aedes Traps (SGATs) throughout Cairns, northern Australia. Weekly mean male Ae. aegypti catches did not significantly differ between trap types. However, the rate of positive weekly detections of male Ae. aegypti was lower for the MAST Sticky than the other three trap types. The MASTs sampled significantly fewer mosquitoes other than male Ae. aegypti, than either the BGS trap or the SGAT. Also, the MASTs and SGATs all caught significantly less non-Culicidae bycatch than the BGS traps. Consequently, we have developed a versatile male Ae. aegypti trap which is potentially of great benefit to Ae. aegypti surveillance programs.

Implications of Insecticide-Treated Mosquito Net Fishing in Lower Income Countries

INTRODUCTION

Insecticide-treated mosquito nets (ITNs) are highly effective for the control of malaria. Yet widely distributed ITNs have been repurposed as fishing nets throughout the world.

OBJECTIVES

Herein we present a synthesis of the current knowledge of ITN fishing and the toxicity of pyrethroids and discuss the potential implications of widespread fishing with ITNs. We further review effective management strategies in tropical fisheries to explore a framework for managing potential ITN fishing impacts.

DISCUSSION

Pyrethroids are toxic to fish and aquatic environments, and fishing with ITNs may endanger the health of fisheries. Furthermore, although human toxicity to the pyrethroid insecticides that impregnate ITNs is traditionally thought to be low, recent scientific advances have shown that pyrethroid exposure is associated with a host of human health issues, including neurocognitive developmental disorders, diabetes, and cardiovascular disease. Although it is known that ITN fishing is widespread, the implications for both fisheries and human communities is understudied and may be severe. https://doi.org/10.1289/EHP7001.

Efficiency of CO2 -baited CDC miniature light traps under semi-field conditions and characterizing response behaviors of female Aedes aegypti (Diptera: Culicidae)

Aedes aegypti (L.) (Diptera: Culicidae) is an important vector of viruses causing dengue, Zika, chikungunya, and yellow fever and as such is a threat to public health worldwide. Effective trapping methods are essential for surveillance of both mosquito species and disease presence. The Centers for Disease Control Miniature Light Trap (CDC-MLT) is an updated version of the New Jersey light trap, which was developed early in the 20^th century. This trap is widely reported as being less successful for Ae. aegypti than for other mosquito species, although the reason for this is unclear. This trap has engendered more Ae. aegypti-tailored designs that still represent the basic design model. The efficiency of the CDC-MLT alone and with CO₂ was tested under semi-field conditions and the behavior of responding female Ae. aegypti was characterized. The CDC-MLT alone failed to capture any mosquitoes and with CO₂ the capture efficiency was less than 2%. Understanding the behaviors that mosquitoes exhibit while encountering a particular trap design or trapping concept may suggest trap improvements to increase capture efficiency. Moreover, this work contributes to our understanding of mosquito host-seeking behavior.

Effects of Color and Perforated Lid on Ovitrap Preference of Aedes aegypti and Aedes albopictus

The shape and color of an ovitrap affect the sampling efficiency of mosquitoes. We examined the effect of perforated lids of different colored cups on the preference of Aedes aegypti and Ae. albopictus for oviposition containers. The mosquito species were collected from Tuy Hoa City, Phu Yen Province, Vietnam in April 2016. Females of both species laid eggs in cups without a lid in the order of black, red, and green. However, the number of eggs laid by both species was not different between the black cups with a perforated lid and those without a lid. Aedes aegypti females laid more eggs in red cups with a perforated lid than cups without a lid. Green cups with a perforated lid were not preferred by Ae. aegypti and Ae. albopictus. Our results showed that the effect of perforated lids on oviposition preference was dependent on cup color and that it differed between the mosquito species. Out study provides valuable insights for the development of more effective ovitraps for Aedes mosquito surveillance and control.

Semi-field evaluation of a modified commercial My Mosquito Deleter larval trap with sticky paper against Aedes aegypti

Aedes aegypti (L.) is a major vector of yellow fever, dengue, and Zika viruses, and its management can be difficult, especially in situations where insecticide usage is restricted and resistance is present. Traps and trapping techniques have mostly been used for monitoring populations of adult mosquitoes, but several commercially available traps have been evaluated and used to reduce nuisance populations of adult mosquitoes (Kline 2006). Suppression of Ae. aegypti, in particular, requires a suite of integrated control measures. One measure gaining more attention is to attract and kill gravid females by exploiting their oviposition behavior. Recently, a commercial larval trap for control of Culex mosquito larvae has been developed and marketed. The commercial brand name is My Mosquito Deleter (MMD; Destin, FL). When gravid female Culex mosquitoes lay their eggs in the MMD larval trap filled with water, the larvae after hatching from eggs will fall downward through the MMD's baffle system. The mosquito larvae cannot come to the surface due to the physical barrier from the baffle ring and black cone, resulting in larval mortality. During the preliminary experiment with the original MMD trap full of water, no adult mosquitoes were collected when larval mosquitoes were commonly recorded, because the gravid mosquitoes flew away after they laid their eggs. In order to catch gravid Aedes mosquitoes when they come to the trap to lay their eggs on water within the containers, we modified the MMD trap by placing sticky paper around the inside at the top of the trap (at the water line) after removing the baffle ring and lowering the water level to create an air pocket. The purpose of the study was to investigate the capability of a trap originally designed to trap Culex larvae to attract and kill gravid Ae. aegypti females with a simple and inexpensive modification by adding a piece of black sticky paper and lowering the level of water, in contrast to the unmodified MMD trap with a lower level of water.

Technical Limitations Associated With Molecular Barcoding of Arthropod Bloodmeals Taken From North American Deer Species

Accurate species-level identification of the source of arthropod bloodmeals is important for deciphering blood feeding patterns of field-collected specimens. Cytochrome c oxidase I (COI) mitochondrial gene sequencing has been used for this purpose; however, species resolution can be difficult to obtain from certain vertebrate genera, including Odocoileus. Sanger sequencing of mitochondrial genes was employed to identify the bloodmeal source of wild-caught mosquitoes trapped in Greeley, Colorado. Initial sequencing of the COI gene of mitochondrial DNA in bloodmeals was inadequate for species-level resolution of bloodmeals from deer in the genus Odocoileus, with current databases returning low fidelity matches to multiple genera. The use of the hypervariable D loop of the control region provided species-level identification of white-tailed deer (Order: Artiodactyla, Family: Cervidae, Odocoileus virginianus); however, taxonomic identification was successful only to genus for mule (O. hemionus hemionus) and black-tailed deer (O. hemionus columbianus). We advocate the use of multiple loci for bloodmeal analysis and the buildout of available databases to include multiple mitochondrial reference genes for reliable host species identification.

Surveillance of invasive Aedes mosquitoes along Swiss traffic axes reveals different dispersal modes for Aedes albopictus and Ae. japonicus

Over the past three decades, Europe has witnessed an increased spread of invasive aedine mosquito species, most notably Aedes albopictus, a key vector of chikungunya, dengue and Zika virus. While its distribution in southern Europe is well documented, its dispersal modes across the Alps remain poorly investigated, preventing a projection of future scenarios beyond its current range in order to target mosquito control. To monitor the presence and frequency of invasive Aedes mosquitoes across and beyond the Alps we set oviposition and BG-Sentinel traps at potential points of entry with a focus on motorway service areas across Switzerland. We placed the traps from June to September and controlled them for the presence of mosquitoes every other week between 2013 and 2018. Over the six years of surveillance we identified three invasive Aedes species, including Ae. albopictus, Ae. japonicus and Ae. koreicus. Based on the frequency and distribution patterns we conclude that Ae. albopictus and Ae. koreicus are being passively spread primarily along the European route E35 from Italy to Germany, crossing the Alps, while Ae. japonicus has been expanding its range from northern Switzerland across the country most likely through active dispersal.

Because of global trade of used tyres and ornamental plants, invasive mosquitoes of the genus Aedes are spreading passively between continents. Within continents, adults are frequently travelling along roads as hitchhikers in motorised vehicles and may then colonise new areas. Because some Aedes mosquitoes are competent to transmit diseases they threaten public and veterinary health. In Europe, the Asian tiger mosquito, Aedes albopictus is of particular concern as it is a vector of chikungunya, dengue and Zika virus. While its distribution in southern Europe is well documented, its dispersal modes across the Alps remain poorly investigated, preventing a projection of future scenarios beyond its current range in order to target mosquito control. To monitor the introduction of invasive Aedes mosquitoes beyond the Alps we placed traps at motorway service areas across Switzerland. Between 2013 and 2018 we identified three invasive Aedes species, including Ae. albopictus, Ae. koreicus (Korean bush mosquito) and Ae. japonicus (Japanese bush mosquito). Based on the frequency and distribution patterns we conclude that Ae. albopictus and Ae. koreicus are being passively spread primarily along the European route E35 from Italy to Germany, while Ae. japonicus has been expanding its range across Switzerland mainly through active dispersal.

Attraction Versus Capture II: Efficiency of the BG-Sentinel Trap Under Semifield Conditions and Characterizing Response Behaviors of Male Aedes aegypti (Diptera: Culicidae)

Aedes aegypti (L.) is an important vector of viruses causing dengue, Zika, chikungunya, and yellow fever and as such presents a serious threat to public health in tropical regions. Control programs involving 'rear and release' of modified male Ae. aegypti are underway and require effective trapping methods for surveillance of both the released insects and the impacted wild mosquito population. The BG-Sentinel trap (BGS) is widely used in Ae. aegypti surveillance but its level of efficiency, that is, what proportion of the mosquitoes encountering the trap are captured, is unknown. This is especially true for male mosquitoes, the behavior of which is incompletely understood. We tested the efficiency of two versions of the BGS for capturing male Ae. aegypti under semifield conditions with and without CO2 and a human skin odor mimic lure and with these baits combined. A navy-blue BGS trap emitting CO2 and a human skin odor mimic captured 18% of the released male Ae. aegypti, with a capture efficiency of 9 % (of the total encounters with the trap). Male Ae. aegypti had multiple encounters with the BGS that did not result in capture; they crossed over the trap entrance without being captured or landed on the sides of the trap. Swarming behavior around the BGS was also recorded, even when only a visual cue was present. Understanding male Ae. aegypti behaviors during an encounter with the BGS can inform improvement of trap design and therefore capture efficiency for surveillance in control programs.

Evaluation of Unmanned Aerial Vehicles and Neural Networks for Integrated Mosquito Management of Aedes albopictus (Diptera: Culicidae)

Aedes albopictus (Skuse), an invasive disease vector, poses a nuisance and public health threat to communities in the Northeastern United States. Climate change and ongoing adaptation are leading to range expansion of this mosquito into upstate New York and other northeastern states. Organized mosquito control can suppress populations, but it is time consuming, costly, and difficult as Ae. albopictus oviposits in small, artificial, water-holding containers. Unmanned aerial vehicles (UAVs), with centimeter-resolution imaging capabilities, can aid surveillance efforts. In this work, we show that a convolutional neural network trained on images from a UAV is able to detect Ae. albopictus habitat in suburban communities, and the number of containers successfully imaged by UAV predicted the number of containers positive for mosquito larvae per home. The neural network was able to identify some, but not all, potential habitat, with up to 67% precision and 40% recall, and can classify whole properties as positive or negative for larvae 80% of the time. This combined approach of UAV imaging and neutral network analysis has the potential to dramatically increase capacity for surveillance, increasing the reach and reducing the time necessary for conventional on-the-ground surveillance methods.

Gravitrap deployment for adult Aedes aegypti surveillance and its impact on dengue cases

House Index, Container Index, and Breteau Index are the most commonly used indices for dengue vector surveillance. However, these larval indices are a poor proxy for measuring the adult population—which is responsible for disease transmission. Information on the adult distribution and density are important for assessing transmission risk as well as for developing effective control strategies. This study introduces a new entomological index, Gravitrap aegypti index (GAI), which estimates the adult female Aedes aegypti population in the community and presents its association with dengue cases. Gravitraps were deployed across 34 treatment sites in Singapore from September 2013 to September 2016. The GAI, derived from the Gravitrap surveillance data, was analysed to investigate the spatio-temporal patterns of the Ae. aegypti population in Singapore. The index was further categorised into low, moderate, and high-risk groups and its association with dengue cases were examined. A Before-After Control Impact analysis was performed to evaluate the epidemiology impact of Gravitrap system on dengue transmission. The Ae. aegypti population exhibits a seasonal pattern, and spatial heterogeneity in Ae. aegypti abundance was observed among treatment sites. The Ae. aegypti population was also found to be unevenly distributed among floors of an apartment block, with low floors (floors 1–4) having a higher abundance of mosquitoes trapped than mid (floors 5–8) and high (floors ≥9) floors. Areas with high GAI were shown to have higher dengue case count. Gravitrap has also demonstrated to be a good dengue control tool. The contribution of cases by treatment sites to the national numbers was lower after Gravitraps deployment. The GAI, which is of better relevance to dengue transmission risk, could be recommended as an indicator for decision making in vector control efforts, and to monitor the spatio-temporal variability of the adult Aedes population in the country. In addition, findings from this study indicate that Gravitraps can be used as a dengue control tool to reduce dengue transmission.

In the absence of an effective vaccine: vector surveillance and control remain the key strategy for dengue prevention and control. The collection of the adult female Aedes mosquito is thus important to understand disease transmission dynamics. Information on its distribution and density are also essential for assessing transmission risk as well as for devising an effective control strategy. Here, we described a new approach to dengue vector surveillance based on adult female Aedes trapping using Gravitraps. Using the Gravitrap surveillance data, we derived a new entomological index, Gravitrap aegypti index (GAI), which estimates the adult female Ae. aegypti population in the community and presents its association with dengue cases. When analysed, the index can provide useful information on the spatio-temporal distribution of the Ae. aegypti population in the country and hence, assist planning of vector control. The GAI, which is of better relevance to dengue transmission risk, could be used as an indicator for decision making in vector control efforts, and to monitor the spatio-temporal variability of the adult Aedes population. In addition, findings from this study indicate that Gravitraps can be used as a dengue control tool to reduce dengue transmission.

Large-Scale Operational Pyriproxyfen Autodissemination Deployment to Suppress the Immature Asian Tiger Mosquito (Diptera: Culicidae) Populations

Effective suppression of container-inhabiting Asian Tiger [Aedes albopictus (Skuse)] (Diptera: Culicidae) and yellow fever [Aedes aegypti (L.)] (Diptera: Culicidae) mosquitoes presents one of the most intractable problems for modern mosquito control. Traditional tools often fail to control populations of these mosquito species, and are prohibitively expensive or have negative environmental impacts. Novel approaches and tools are urgently needed for integrated container-inhabiting mosquito management programs. One of the most promising techniques is autodissemination. We present the results of a long-term large-scale study conducted in a temperate urbanized environment representing typical Ae. albopictus habitats. Three treatment sites with autodissemination stations and three nearby reference sites were monitored for eggs, immature, and adult mosquitoes over a period of 3 yr from 2014 to 2016. Elevated larval and pupal mortality of 12-19% on average was the most notable outcome in sentinel cups of the treatment sites. The number of eggs in the treatment sites was significantly reduced in 2014, but not in 2015 or 2016. Adult populations remained similar in treatment and reference sites throughout the study. The impact of autodissemination on mosquito populations was lower than reported by previous investigations. Technical and logistical problems associated with wider coverage and working in multiple urban neighborhoods contributed to reduced efficacy. Incorporating autodissemination with routine mosquito control operations and commercializing this methodology for general public use will require further research on combining this tool with other novel or conventional technologies.

The Use of Granular Cyclopentanone as Alternative to Artificial Source of Carbon Dioxide in Improved Passive Outdoor Host Seeking Device (POHD)

Reliable sources of CO2 that are relatively cheap, obtainable, and easy to sustain are immediately required for scaling up of odor-baited mosquito surveillance and control devices. Several odor-baited devices are in the pipeline; however, their scale-up against residual malaria transmission, particularly in resource poor areas, is limited by the unavailability of reliable sources of CO2 and reliance on electrical power sources among other factors. We evaluated the use of granular cyclopentanone as an alternative to artificial or yeast fermentation-produced CO2 in passive outdoor host seeking device (POHD). Experiments were conducted against semifield reared An. arabiensis within the semifield system (SFS) at Ifakara Health Institute. Mosquitoes were tested against odor-baited POHDs augmented with yeast fermentation-produced CO2, granular cyclopentanone, attractive blends (Mbita or Ifakara), or their combinations. An insecticide, bendiocarb, was a killing agent used as a proxy for marking the mosquitoes visit the POHDs. Relative attractiveness of different treatment combinations was compared based on the proportion of dead mosquitoes that visited the POHD. The POHD augmented with granules of cyclopentanone alone was attractive to An. arabiensis as much as, or more than, POHDs augmented with yeast fermentation-produced CO2. The POHD baited with CO2 attracted more mosquitoes than those POHDs baited with synthetic blends alone; when these blends are combined with CO2, they attracted more mosquitoes than individual blends. More importantly, such POHDs baited with cyclopentanone attracted far greater proportion of mosquitoes than the POHD baited with either Mbita or Ifakara blend alone. The granular cyclopentanone strongly enhanced/potentiated the attractiveness of POHD baited with Mbita blends against mosquitoes compared to that of POHD baited with Ifakara blend. Moreover, the granular cyclopentanone retained its residual activity against An. arabiensis for up to 2 months after application particularly when used in combination with Mbita blend. In conclusion, this study demonstrates that cyclopentanone granules have the potential to substitute sources of CO2 in outdoor-based surveillance and control devices, thus warranting evaluation of such alternative under realistic field conditions.

Factors Modulating Captures of Gravid Aedes aegypti Females

To improve detection and assessment of Aedes aegypti abundance, we investigated whether microhabitat factors of the location of autocidal gravid ovitraps (AGO traps) influenced captures of gravid females in 2 locations in southern Puerto Rico. One location had been under vector control for several years using mass AGO trapping (intervention site), where Ae. aegypti abundance was several times lower than in the other study site without mosquito control (nonintervention site). We observed 10 environmental factors describing trap microhabitat location, and monitored water volume and minimum, maximum, and average temperature in AGO traps. Air temperature, relative humidity, and rainfall were recorded at each site. We conducted a hot-spot analysis of AGO traps to understand whether trap captures were influenced by the local abundance of mosquitoes rather than or in addition to trap microhabitat factors. AGO traps were classified using a 2-step cluster analysis based on attributes of trap microhabitats, water temperature, and water volume. Captures of female Ae. aegypti in each cluster per site were compared between resulting clusters to determine whether trap microhabitat factors defining the clusters were associated with trap captures. Trap captures in both study sites were mostly correlated with captures in nearby traps regardless of trap microhabitat factors, possibly reflecting the influence of the spatial aggregation of mosquitoes coming from nearby aquatic habitats or the concentration of dispersing adults. These results indicated that AGO traps can be located at places that can be easily reached during periodic inspections, such as in front of houses, without much regard to local microhabitat conditions.

Context-Dependent Accuracy of the BG-Counter Remote Mosquito Surveillance Device in North Carolina

There is a clear need for improved vector surveillance approaches that are affordable, labor efficient, and safer than traditional methods. The BG-Counter (Biogents USA, Moorefield, WV) is a device for remotely monitoring mosquito activity in combination with the BG-Sentinel (Biogents USA), a widely used trap for the collection of host-seeking mosquitoes. The BG-Counter uses a wireless connection to provide real-time counts of mosquitoes captured by the BG-Sentinel, allowing users to remotely monitor mosquito populations. This study tested the effectiveness of the BG-Counter in 5 North Carolina counties. A total of 96 trap-days resulted in the collection of >45,000 individual mosquitoes representing 35 species. Aedes albopictus was the most common species collected in all counties, except for New Hanover County where Culex nigripalpus was the most common. The mean daily accuracy ranged from 80.1% (New Hanover County) to 9.4% (Jackson County). There was a significant linear relationship between the actual number of mosquitoes collected and the device counts at all sites except Jackson County, the site with the lowest relative mosquito abundance compared with nontarget organisms. A linear regression of daily BG-Counter accuracy and the daily proportion of mosquitoes to the total number of arthropods collected revealed a significant positive linear relationship, supporting the premise that the BG-Counter is less effective when the relative abundance of mosquitoes is low. Mosquito surveillance programs using the BG-Counter should recognize its context-dependent accuracy and routinely evaluate the accuracy of the device based on local conditions.

Attraction Versus Capture: Efficiency of BG-Sentinel Trap Under Semi-Field Conditions and Characterizing Response Behaviors for Female Aedes aegypti (Diptera: Culicidae)

Aedes aegypti (L.) is an important vector of viruses causing dengue, Zika, chikungunya, and yellow fever and as such is a threat to public health worldwide. Effective trapping methods are essential for surveillance of both the mosquito species and disease presence. The BG-Sentinel (BGS) is a widely used to trap Ae. aegypti but little is known of its efficiency, i.e., what proportion of the mosquitoes encountering the trap are captured. The first version of the BGS trap was predominantly white, and the current version is mostly navy blue. While this trap is often deployed without any olfactory lure, it can also be deployed with CO2 and/or a human skin odor mimic lure to increase capture rates. We tested the efficiency of capturing Ae. aegypti under semi-field conditions for the original white version without lures as well the blue version with and without various lure combinations. None of the configurations tested here captured 100% of the mosquitoes that encountered the trap. A navy-blue trap emitting CO2 and a skin odor mimic produced the highest capture (14% of the total insects in the semi-field cage), but its capture efficiency was just 5% (of mosquitoes encountering the trap). Mosquitoes often had multiple encounters with a trap that did not result in capture; they crossed over the trap entrance without being captured or landed on the sides of the trap. Understanding these behaviors and the factors that induce them has the potential to suggest improvement in trap design and therefore capture efficiency.

Toward a blood-free diet for Anopheles darlingi (Diptera: Culicidae)

Due to ethical issues associated with the use of blood for mosquito laboratory experiments, an artificial diet that supports the production of eggs and larvae is highly desirable. We report the development of an artificial diet using direct feeding on protein-rich sugar solution (PRSS) as an alternative to whole blood and evaluated its effects on several biologic parameters of Anopheles darlingi (Root). Field-collected females were fed with different PRSSs containing bovine serum albumin (BSA) at 200 and 400 mg/ml with or without supplemental salts. Engorged mosquitoes were monitored for survival to oviposition, before being forced to oviposit. The proportion ovipositing, number of eggs, and number of larvae were recorded for each treatment. Mosquitoes promptly engorged on PRSSs. The mean proportion of mosquitoes fed with PRSS that survived to oviposition did not differ statistically from that of blood-fed ones. The oviposition proportion of females fed with PRSS at 200 mg/ml was similar to that of blood-fed mosquitoes, whereas mean egg production was lower for most PRSS-fed females, except for those fed with BSA at 400 mg/ml. However, the mean larval production of PRSS-fed mosquitoes was significantly lower than that of blood-fed females. Although feeding An. darlingi on simple PRSS triggered oogenesis and embryogenesis, our results highlight the need for additional nutrients to increase the number of larvae to improve overall reproduction potential.

Assessment of Aedes aegypti (Diptera: Culicidae) Males Flight Ability for SIT Application: Effect of Device Design, Duration of Test, and Male Age

The Sterile Insect Technique (SIT) is a pest control method where large numbers of sterile males are released to induce sterility in wild populations. Since a successful SIT application depends on the released sterile males being competitive with wild males, standard quality control tests are a necessary component of any SIT program. Flight ability (ability to fly out from a device) is a reliable indicator of insect quality. Based on previous studies, we developed four new tubular devices constructed with locally available materials to explore their potential as flight test devices for Aedes aegypti (L.) mass-reared males. Males were allowed to fly upwards through a vertical tube, the ones that flew out were considered successful. The effect of male age (0 to 21 d old), test time interval (30 min to 24 h), and the design of the device (40 and 80 cm height and 2 and 3.5 cm diameter) were evaluated. Our devices determined differences in the flight ability of Ae. aegypti males of different ages. During the first minutes, more old males escaped than young males in three out of four types of devices. However, young males reached higher rates of escape in all cases after 24 h. For standard quality control tests, we recommend testing 2- to 3-d-old sexually mature males in the high and narrow device (80 × 2 cm). Further observations for time intervals between 1 and 5 h might be performed to decide the shortest and more representative interval to use.

Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons

BACKGROUND

Residents of malaria-endemic communities spend several hours outdoors performing different activities, e.g. cooking, story-telling or eating, thereby exposing themselves to potentially-infectious mosquitoes. This compromises effectiveness of indoor interventions, notably long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacy against mosquitoes of hessian fabric mats and ribbons treated with the spatial repellent, transfluthrin, and fitted to chairs and outdoor kitchens, respectively.

METHODS

Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of locally-made transfluthrin-emanating chairs and hessian ribbons were tested in outdoor environments of 28 households in dry and wet seasons, using volunteer-occupied exposure-free double net traps. CDC light traps were used to estimate host-seeking mosquito densities within open-structure outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24 h-mortality. Finally, The World Health Organization insecticide susceptibility tests were conducted on wild-caught Anopheles from the villages.

RESULTS

Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Two-thirds of these spaces were sited under trees, and only one third (34.4%) were built-up. The outdoor structures were usually makeshift kitchens having roofs and partial walls. Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70-85%, while transfluthrin-treated hessian ribbons fitted to the outdoor kitchens caused 77-81% reduction in the general peri-domestic area. Almost all the field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. The An. arabiensis were susceptible to non-pyrethroids (pirimiphos methyl and bendiocarb), but resistant to pyrethroids commonly used on LLINs (deltamethrin and permethrin).

CONCLUSION

Most houses had actively-used peri-domestic outdoor spaces where exposure to mosquitoes occurred. The transfluthrin-treated chairs and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant field-caught malaria vectors. These two new prototype formats for transfluthrin emanators, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.

Pesticide Misting System Enhances Residual Pesticide Treatment of HESCO Geotextile

Residual pesticide treatment of US military materials such as camouflage netting and HESCO blast wall geotextile is an effective way to reduce biting pressure within protected perimeters. However, residual treatments eventually wane and require retreatment in situ, which may not be possible or practical in military scenarios. One solution is to install pesticide misting systems on treated perimeters, which may additively enhance residual treatments, and gradually retreat perimeter material as misted pesticide settles. In this investigation we show that pesticide misting can extend efficacy of residual treatments on HESCO geotextile against mosquitoes and sand flies in a hot-arid desert environment by 1-2 wk.

Evaluation of Novel Trapping Lures for Monitoring Exotic and Native Container-Inhabiting Aedes spp. (Diptera: Culicidae) Mosquitoes

Surveillance for diurnal container-inhabiting mosquitoes such as Aedes albopictus (Skuse), Aedes japonicus japonicus (Theobald), and Aedes triseriatus (Say) have routinely relied on the deployment of multiple trap types, including CO2-baited light traps, gravid traps, oviposition traps, and BG-Sentinel. These trap configurations have met with varying degrees of effectiveness and in many instances likely under-sample these key mosquito vectors. Most recently, the BG-Sentinel trap used in conjunction with the human-scent lure has been largely accepted as the gold-standard for monitoring Ae. albopictus. However, its ability to attract other container-inhabiting Aedes species has not been fully evaluated. During 2018, we tested new scent lures, TrapTech Lure-A and Lure-H (Bedoukian Research, Inc.), using BG-Sentinel traps with CO2 in two regions of Connecticut, Stamford and Hamden, against the BG-Lure. Pooled mosquitoes were additionally screened for arbovirus infection. A total of 47,734 mosquitoes representing 8 genera and 32 species were captured during the study, with the Stamford site deriving on average three times as many mosquitoes per trap, adjusting for sampling effort. Lure-A and Lure-H outperformed the BG-Lure in terms of total numbers, diversity evenness, and the proportion of both Ae. j. japonicus and Ae. triseriatus. There were no significant differences among lures in capturing Ae. albopictus, and in terms of species richness. Fifty-seven isolates of virus (West Nile, Jamestown Canyon, and La Crosse viruses) were obtained during the study, with no significant difference between trap-lure. We highlight both novel lures as effective attractants for use in mosquito surveillance=, which either outperform, or equal, BG-Lure.

A potential global surveillance tool for effective, low-cost sampling of invasive Aedes mosquito eggs from tyres using adhesive tape

BACKGROUND

The international movement of used tyres is a major factor responsible for global introductions of Aedes invasive mosquitoes (AIMs) (Diptera: Culicidae) that are major disease vectors (e.g. dengue, Zika, chikungunya and yellow fever). Surveillance methods are restricted by expense, availability and efficiency to detect all life stages. Currently, no tested method exists to screen imported used tyres for eggs in diapause, the life stage most at risk from accidental introduction. Here we test the efficiency of adhesive tape as an affordable and readily available material to screen tyres for eggs, testing its effect on hatch rate, larval development, DNA amplification and structural damage on the egg surface.

RESULTS

We demonstrated that the properties of adhesive tape can influence pick up of dormant eggs attached to dry surfaces. Tapes with high levels of adhesion, such as duct tape, removed eggs with high levels of efficiency (97% ± 3.14). Egg numbers collected from cleaned used tyres were found to explain larval hatch rate success well, particularly in subsequent larval to adult emergence experiments. The strength of this relationship decreased when we tested dirty tyres. Damage to the exochorion was observed following scanning electron microscopy (SEM), possibly resulting in the high variance in the observed model. We found that five days was the optimal time for eggs to remain on all tested tapes for maximum return on hatch rate success. Tape type did not inhibit amplification of DNA of eggs from three, five or ten days of exposure. Using this DNA, genotyping of AIMs was possible using species-specific markers.

CONCLUSIONS

We demonstrated for the first time that adhesive tapes are effective at removing AIM eggs from tyres. We propose that this method could be a standardised tool for surveillance to provide public health authorities and researchers with an additional method to screen tyre cargo. We provide a screening protocol for this purpose. This method has a global applicability and in turn can lead to increased predictability of introductions and improve screening methods at high risk entry points.

Evaluation of mosquito electrocuting traps as a safe alternative to the human landing catch for measuring human exposure to malaria vectors in Burkina Faso

BACKGROUND

Measuring human exposure to mosquito bites is a crucial component of vector-borne disease surveillance. For malaria vectors, the human landing catch (HLC) remains the gold standard for direct estimation of exposure. This method, however, is controversial since participants risk exposure to potentially infected mosquito bites. Recently an exposure-free mosquito electrocuting trap (MET) was developed to provide a safer alternative to the HLC. Early prototypes of the MET performed well in Tanzania but have yet to be tested in West Africa, where malaria vector species composition, ecology and behaviour are different. The performance of the MET relative to HLC for characterizing mosquito vector population dynamics and biting behaviour in Burkina Faso was evaluated.

METHODS

A longitudinal study was initiated within 12 villages in Burkina Faso in October 2016. Host-seeking mosquitoes were sampled monthly using HLC and MET collections over 14 months. Collections were made at 4 households on each night, with METs deployed inside and outside at 2 houses, and HLC inside and outside at another two. Malaria vector abundance, species composition, sporozoite rate and location of biting (indoor versus outdoor) were recorded.

RESULTS

In total, 41,800 mosquitoes were collected over 324 sampling nights, with the major malaria vector being Anopheles gambiae sensu lato (s.l.) complex. Overall the MET caught fewer An. gambiae s.l. than the HLC (mean predicted number of 0.78 versus 1.82 indoors, and 1.05 versus 2.04 outdoors). However, MET collections gave a consistent representation of seasonal dynamics in vector populations, species composition, biting behaviour (location and time) and malaria infection rates relative to HLC. As the relative performance of the MET was somewhat higher in outdoor versus indoor settings, this trapping method slightly underestimated the proportion of bites preventable by LLINs compared to the HLC (MET = 82.08%; HLC = 87.19%).

CONCLUSIONS

The MET collected proportionately fewer mosquitoes than the HLC. However, estimates of An. gambiae s.l. density in METs were highly correlated with HLC. Thus, although less sensitive, the MET is a safer alternative than the HLC. Its use is recommended particularly for sampling vectors in outdoor environments where it is most sensitive.

Vector Mosquito Surveillance Using Centers For Disease Control and Prevention Autocidal Gravid Ovitraps In San Antonio, Texas

Mosquito surveillance in large urban areas of the southern USA that border Mexico has become increasingly important due to recent transmission of Zika virus and chikungunya virus in the Americas as well as the continued threat of dengue and West Nile viruses. The vectors of these viruses, Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus, co-occur in residential areas, requiring vector control entities to deploy several different trap types, often expensive and labor-intensive, to surveil these ecologically different species. We evaluated the use of a single trap type, the US Centers for Disease Control and Prevention autocidal gravid ovitraps (AGOs), to monitor all 3 vector species across residential neighborhoods in San Antonio, TX, over 12 wk (epiweeks 24-35). Mosquito abundance was highest early in our surveillance period (epiweek 25) and was driven largely by Cx. quinquefasciatus. The AGOs collected significantly more Cx. quinquefasciatus than both Aedes species, with more Ae. aegypti collected than Ae. albopictus. The average number of Ae. aegypti captured per trap was consistent across most neighborhoods except for 2 areas where one had significantly the highest and the other with the lowest mosquitoes collected per trap. The average number of Ae. albopictus captured per trap varied with no clear pattern, and Cx. quinquefasciatus were trapped most often near forested hill country neighborhoods. These results indicate that AGOs are appropriate for detecting and tracking the relative abundance of Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus across a large and diverse urban landscape over time and therefore may be an inexpensive and streamlined option for vector surveillance programs in large cities.

Evaluation of an ultraviolet LED trap for catching Anopheles and Culex mosquitoes in south-eastern Tanzania

BACKGROUND

Improved surveillance techniques are required to accelerate efforts against major arthropod-borne diseases such as malaria, dengue, filariasis, Zika and yellow-fever. Light-emitting diodes (LEDs) are increasingly used in mosquito traps because they improve energy efficiency and battery longevity relative to incandescent bulbs. This study evaluated the efficacy of a new ultraviolet LED trap (Mosclean) against standard mosquito collection methods.

METHODS

The study was conducted in controlled semi-field settings and in field conditions in rural south-eastern Tanzania. The Mosclean trap was compared to commonly used techniques, namely CDC-light traps, human landing catches (HLCs), BG-Sentinel traps and Suna traps.

RESULTS

When simultaneously placed inside the same semi-field chamber, the Mosclean trap caught twice as many Anopheles arabiensis as the CDC-light trap, and equal numbers to HLCs. Similar results were obtained when traps were tested individually in the chambers. Under field settings, Mosclean traps caught equal numbers of An. arabiensis and twice as many Culex mosquitoes as CDC-light traps. It was also better at trapping malaria vectors compared to both Suna and BG-Sentinel traps, and was more efficient in collecting mosquitoes indoors than outdoors. The majority of An. arabiensis females caught by Mosclean traps were parous (63.6%) and inseminated (89.8%). In comparison, the females caught by CDC-light traps were 43.9% parous and 92.8% inseminated.

CONCLUSIONS

The UV LED trap (Mosclean trap) was efficacious for sampling Anopheles and Culex mosquitoes. Its efficacy was comparable to and in some instances better than traps commonly used for vector surveillance. The Mosclean trap was more productive in sampling mosquitoes indoors compared to outdoors. The trap can be used indoors near human-occupied nets, or outdoors, in which case additional CO2 improves catches. We conclude that this trap may have potential for mosquito surveillance. However, we recommend additional field tests to validate these findings in multiple settings and to assess the potential of LEDs to attract non-target organisms, especially outdoors.

[Survey of Anopheles vectors in Nanyang City from 2005 to 2017]

OBJECTIVE

To investigate the malaria vectors in Nanyang City.

METHODS

Two townships were selected as malaria vector surveillance sites in Nanyang City from 2005 to 2017, including Mazhenfu Township in Tanghe County and Huaiyuan Township in Tongbai County, and the malaria vectors were investigated using the semi-overnight human baiting trapping method and mosquito trapping in nets.

RESULTS

The mean density of Anopheles sinensis was 0.65 to 22.30 mosquitos/(person · hour) in the two surveillance sites in Nanyang City using the human baiting trapping method from 2005 to 2017, and the peak density was detected in June and July. An. anthropophagus was captured only in Tongbai County during the period between 2008 and 2011, with a mean density of 0.03 to 1.10 mosquitos/(person · hour). The mean density of An. sinensis was 0.08 to 0.24 mosquitos/(net · night) using the mosquito trapping in nets from 2005 to 2011, and the peak density was detected in July and August, while few An. anthropophagus captured only in Tongbai County, with a mean density of 0.01 to 0.02 mosquitos/(net · night).

CONCLUSIONS

There are malaria vectors in Nanyang City, including An. sinensis and An. anthropophagus, and An. sinensis is the dominant mosquito species.

Citronella oil-loaded electrospun micro/nanofibrous matrices as sustained repellency systems for the Asian tiger mosquito Aedes albopictus

BACKGROUND

Mosquitoes are hematophagous insects of major public health concern, serving as vectors of many diseases. Available products for personal protection against mosquitoes lack adequate efficacy and in most cases need to be reapplied or replaced frequently. In recent years, the encapsulation of the active repellents in various matrices has arisen as an alternative method for the development of new-generation repellent systems. The aim of the present study was to explore the potential of functional micro/nanofibrous matrices as systems for the sustained release of the highly volatile insect-repellent citronella oil.

RESULTS

Micro/nanofibrous single- and triple-layer systems incorporating citronella oil as the active agent were developed via the electrospinning technique using the low-cost, non-toxic, biodegradable polymers cellulose acetate and polyvinylpyrrolidone. All the micro/nanofiber systems produced exhibited prolonged release of citronella oil and a high repellent activity in laboratory bioassays against the mosquito Aedes albopictus for at least 4 weeks.

CONCLUSION

Considering the high volatility of the embedded repellent, the present study demonstrates the strong potential of the micro/nanofibrous matrices to act as carriers of highly volatile repellents for an effective and sustained protection from mosquitoes. © 2019 Society of Chemical Industry.

Videographic analysis of flight behaviours of host-seeking Anopheles arabiensis towards BG-Malaria trap

The BG-Malaria trap (BGM) is an adaptation of the well-known BG-Sentinel trap (BGS) with greater trapping efficiencies for anopheline and culicine mosquitoes. Its continued optimization requires greater understanding of mosquito flight behaviors near it. We used three high-resolution infrared cameras (68 frames/second) to track flight behaviors of laboratory-reared Anopheles arabiensis females in vicinity of the BGM in comparison with BGS. Additional comparisons were done for BGM at 20, 40 and 80cm heights, and for BGMs baited with Ifakara blend plus CO2, CO2 alone, or no bait. More mosquitoes were observed near BGM than BGS. Both BGMs installed 20cm above the floor and baited with CO2 received more visits by host-seeking mosquitoes than the other BGMs evaluated in their respective experiments. Trap designs, height and attractants all influence mosquito activity in vicinity of the traps which can be readily visualized using infrared cameras to accelerate trap development and testing. The greater activity of host-seeking mosquitoes near BGM than BGS supports the proven superiority of BGM traps in field and semi-field settings.

Autocidal gravid ovitraps protect humans from chikungunya virus infection by reducing Aedes aegypti mosquito populations

Background

Public health responses to outbreaks of dengue, chikungunya, and Zika virus have been stymied by the inability to control the primary vector, Aedes aegypti mosquitos. Consequently, the need for novel approaches to Aedes vector control is urgent. Placement of three autocidal gravid ovitraps (AGO traps) in ~85% of homes in a community was previously shown to sustainably reduce the density of female Ae. aegypti by >80%. Following the introduction of chikungunya virus (CHIKV) to Puerto Rico, we conducted a seroprevalence survey to estimate the prevalence of CHIKV infection in communities with and without AGO traps and evaluate their effect on reducing CHIKV transmission.

Methods and findings

Multivariate models that calculated adjusted prevalence ratios (aPR) showed that among 175 and 152 residents of communities with and without AGO traps, respectively, an estimated 26.1% and 43.8% had been infected with CHIKV (aPR = 0.50, 95% CI: 0.37–0.91). After stratification by time spent in their community, protection from CHIKV infection was strongest among residents who reported spending many or all weekly daytime hours in their community:10.3% seropositive in communities with AGO traps vs. 48.7% in communities without (PR = 0.21, 95% CI: 0.11–0.41). The age-adjusted rate of fever with arthralgia attributable to CHIKV infection was 58% (95% CI: 46–66%). The monthly number of CHIKV-infected mosquitos and symptomatic residents were diminished in communities with AGO traps compared to those without.

Conclusions

These findings indicate that AGO traps are an effective tool that protects humans from infection with a virus transmitted by Ae. aegypti mosquitos. Future studies should evaluate their protective effectiveness in large, urban communities.

Aedes species mosquitos transmit pathogens of public health importance, including dengue, Zika, and chikungunya viruses. No tools exist to control these mosquitos that sustainably and effectively prevent human infections. Autocidal gravid ovitraps (AGO traps) have been shown to sustainably reduce Aedes populations by >80%. After chikungunya virus was introduced into Puerto Rico, we conducted serosurveys in communities with and without AGO traps. We observed a two-fold lower prevalence of chikungunya virus infection among residents of communities with AGO traps compared to communities without. Among infected residents of communities with traps, a significant proportion likely had been infected while outside their community. These findings indicate that AGO traps are an effective tool that protects humans from infection with pathogens transmitted by Aedes mosquitos.

Mosquito Control and Coastal Development: How they Have Coexisted and Matured in Florida and Australia

The aims of this review were to compare planning for both mosquito control and land use in east-central Florida, USA, and in New South Wales, Queensland, and the Northern Territory, Australia. Saltwater mosquito production in mangroves and salt marsh is the predominant mosquito control concern in all the areas. Urban encroachment towards saltwater mosquito habitats is a problem in both Florida and Australia. In east-central Florida and the Northern Territory, mosquito control is supported by comprehensive source reduction programs, whereas in Queensland and New South Wales, larviciding is the main method of control. The long-term control by source reduction programs reduces vulnerability to mosquito issues as population encroaches towards wetlands, whereas larviciding programs have to respond repeatedly as problems arise. Problems from urban encroachment are exacerbated if mosquito control and land-use planning are not integrated. Further, urban planning that is not informed by mosquito management can lead to increased mosquito problems by inadvertent design or allowing residential development close to mosquito habitats. This increases the need for mosquito control and related resourcing. At the regional level of governance, Florida and the Northern Territory generally have greater integration between planning for development and mosquito control than at the local government level in New South Wales and Queensland, where there is a lack of integration between mosquito agencies and planners. It is concluded that coordination of planning and mosquito control is more effective at higher government levels than at local levels, which have less connectivity between management areas and/or insufficient resources. The lesson is that collaboration can assist in avoiding or resolving conflicts.

Evaluation and Comparison of Spray Equipment for Indoor Residual Spraying

The World Health Organization (WHO) has recently recommended indoor residual spraying (IRS) as part of a vector control strategy to combat Aedes-borne diseases, including dengue, chikungunya, and Zika viruses. Hand compression sprayers have been used in malaria prevention and control programs worldwide since the 1950s and are a standard for IRS application. However, there are technological advances that should be considered to improve IRS application (e.g., flow-control valves, rechargeable-battery equipment, reduced-drift nozzles, etc.), particularly if interventions are performed in urban areas to target Aedes aegypti. Using WHO guidelines, we contrasted technical characteristics of potential IRS equipment including hand compression sprayers (Hudson X-pert, Goizper IK Vector Control Super), rechargeable-battery sprayers (Solo 416, Birchmeier REC 15ABZ, Hudson NeverPump), and motorized sprayers (Honda WJR 2525, Kawashima AK35GX). Measurements included flow rate, droplet size, battery/fuel life, and technical/physical characteristics. Flow rate, the most important parameter, of the Hudson X-pert was stabilized at 550 ml/min by the use of a control flow valve (CFV). The IK Vector Control Super had integrated CFVs and produced a similar flow as the Hudson X-pert. Rechargeable-battery equipment provided consistent flow as well as negligible noise. Motorized sprayers also produced consistent flow, but their weight, high noise pollution when used indoors, and high engine temperature made them highly unpleasant for technicians. We identify alternatives to the more traditional hand compression Hudson X-pert sprayer with technical and operational considerations for performing IRS.

A Low-Cost, Passive Release Device for the Surveillance and Control of Mosquitoes

Mosquitoes continue to be a major threat to global health, and the ability to reliably monitor, catch, and kill mosquitoes via passive traps is of great importance. Global, low-cost, and easy-to-use outdoor devices are needed to augment existing efforts in mosquito control that combat the spread of disease, such as Zika. Thus, we have developed a modular, portable, non-powered (passive), self-contained, and field-deployable device suitable for releasing volatiles with a wide range of applications such as attracting, repelling, and killing mosquitoes. This unique device relies on a novel nested wick and two-reservoir design that achieves a constant release of volatiles over several hundred hours. Devices loaded with one of either two compounds, geraniol or 1-methylpiperazine (MP), were tested in a controlled environment (32 °C and 70% relative humidity), and both compounds achieved a constant release from our devices at a rate of 2.4 mg/h and 47 mg/h, respectively. The liquid payload can be volatile attractants or repellants as well as mosquitocide-containing feeding solutions for capture and surveillance. This low-cost device can be utilized for both civilian and military mosquito control purposes, but it will be particularly important for protecting those in economically repressed environments, such as sub-Saharan Africa and Central and South America.

Truck-mounted area-wide applications of larvicides and adulticides for extended suppression of adult Aedes albopictus

BACKGROUND

Given the lack of vaccines for most vector-borne diseases, vector control is often the primary option for disease control. Aedes albopictus are difficult to control because the immatures primarily develop in containers ubiquitous in residential properties. Conventional adulticide campaigns often result in brief, rebounding population declines, so incorporating new techniques into an integrated pest management program is imperative. We performed combined area-wide applications of the larvicides Bacillus thuringiensis var. israelensis and pyriproxyfen with the adulticide sumithrin and prallethrin to achieve extended suppression of Ae. albopictus populations in Trenton, NJ, USA. We deployed bioassay cups to assess the spatial penetration and efficacy of the applications.

RESULTS

Inhibition of adult emergence was significantly higher in the treatment bioassay cups than in laboratory controls (z = 4.65, P < 0.0001) and field control bioassay cups (z = 8.93, P < 0.0001). We observed a lower trend in adult numbers following season-long combined application of pyriproxyfen and adulticide, with numbers of adult Ae. albopictus at the treatment site up to five times lower than at the control site.

CONCLUSION

Pyriproxyfen is a powerful mosquito larvicide and pupacide with low mammalian toxicity that shows promise for area-wide vehicle-mounted (either ground or airborne) applications. © 2018 Society of Chemical Industry.