Testing configurations of attractive toxic sugar bait (ATSB) stations in Mali, West Africa, for improving the control of malaria parasite transmission by vector mosquitoes and minimizing their effect on non-target insects.

BACKGROUND: Application methods of |Attractive Toxic Sugar Baits (ATSB) need to be improved for wide-scale use, and effects on non-target organisms (NTOs) must be assessed. The goals of this study were to determine, at the village level, the effect of different configurations of bait stations to (1) achieve < 25% Anopheles mosquito vector daily feeding rate for both males and females and (2) minimize the effect on non-target organisms. METHODS: Dye was added to Attractive Sugar Bait Stations (without toxin) to mark mosquitoes feeding on the baits, and CDC UV light traps were used to monitor for marked mosquitoes. An array of different traps were used to catch dye marked NTOs, indicating feeding on the ASB. Stations were hung on homes (1, 2, or 3 per home to optimize density) at different heights (1.0 m or 1.8 m above the ground). Eight villages were chosen as for the experiments. RESULTS: The use of one ASB station per house did not mark enough mosquitoes. Use of two and three stations per house gave feeding rates above the 25% goal. There was no statistical difference in the percentage of marked mosquitoes between two and three stations, however, the catches using two and three bait stations were both significantly higher than using one. There was no difference in An. gambiae s.l. feeding when stations were hung at 1.0 and 1.8 m. At 1.8 m stations sustained less accidental damage. ASB stations 1.8 m above ground were fed on by three of seven monitored insect orders. The monitored orders were: Hymenoptera, Lepidoptera, Coleoptera, Diptera, Hemiptera, Neuroptera and Orthoptera. Using one or two stations significantly reduced percentage of bait-fed NTOs compared to three stations which had the highest feeding rates. Percentages were as follows: 6.84 ± 2.03% Brachycera followed by wasps (Hymenoptera: Vespidae) 5.32 ± 2.27%, and Rhopalocera 2.22 ± 1.79%. Hanging the optimal number of stations per house for catching mosquitoes (two) at 1.8 m above ground, limited the groups of non-targets to Brachycera, Chironomidae, Noctuoidea, Rhopalocera, parasitic wasps and wasps (Hymenoptera). Feeding at 1.8 m only occurred when stations were damaged. CONCLUSIONS: The goal of marking quarter of the total Anopheles population per day was obtained using 2 bait stations at 1.8 m height above the ground. This configuration also had minimal effects on non-target insects.

Large-scale field trial of attractive toxic sugar baits (ATSB) for the control of malaria vector mosquitoes in Mali, West Africa.

BACKGROUND: The aim of this field trial was to evaluate the efficacy of attractive toxic sugar baits (ATSB) in Mali, where sustained malaria transmission occurs despite the use of long-lasting insecticidal nets (LLINs). ATSB bait stations were deployed in seven of 14 similar study villages, where LLINs were already in widespread use. The combined use of ATSB and LLINs was tested to see if it would substantially reduce parasite transmission by Anopheles gambiae sensu lato beyond use of LLINs alone. METHODS: A 2-day field experiment was conducted to determine the number of mosquitoes feeding on natural sugar versus those feeding on bait stations containing attractive sugar bait without toxin (ASB)-but with food dye. This was done each month in seven random villages from April to December 2016. In the following year, in seven treatment villages from May to December 2017, two ATSB bait stations containing the insecticide dinotefuran were placed on the outer walls of each building. Vector population density was evaluated monthly by CDC UV light traps, malaise traps, pyrethrum spray (PSCs) and human landing catches (HLCs). Female samples of the catch were tested for age by examination of the ovarioles in dissected ovaries and identification of Plasmodium falciparum sporozoite infection by ELISA. Entomological inoculation rates (EIR) were calculated, and reductions between treated and untreated villages were determined. RESULTS: In the 2-day experiment with ASB each month, there was a lower number of male and female mosquitoes feeding on the natural sugar sources than on the ASB. ATSB deployment reduced CDC-UV trap female catches in September, when catches were highest, were by 57.4% compared to catches in control sites. Similarly, malaise trap catches showed a 44.3% reduction of females in August and PSC catches of females were reduced by 48.7% in September. Reductions of females in HLCs were lower by 19.8% indoors and 26.3% outdoors in September. The high reduction seen in the rainy season was similar for males and reductions in population density for both males and females were > 70% during the dry season. Reductions of females with ≥ 3 gonotrophic cycles were recorded every month amounting to 97.1% in October and 100.0% in December. Reductions in monthly EIRs ranged from 77.76 to 100.00% indoors and 84.95% to 100.00% outdoors. The number of sporozoite infected females from traps was reduced by 97.83% at treated villages compared to controls. CONCLUSIONS: Attractive toxic sugar baits used against Anopheles mosquitoes in Mali drastically reduced the density of mosquitoes, the number of older females, the number of sporozoite infected females and the EIR demonstrating how ATSB significantly reduces malaria parasite transmission.

Frequent sugar feeding behavior by Aedes aegypti in Bamako, Mali makes them ideal candidates for control with attractive toxic sugar baits (ATSB).

BACKGROUND: Current tools and strategies are not sufficient to reliably address threats and outbreaks of arboviruses including Zika, dengue, chikungunya, and yellow fever. Hence there is a growing public health challenge to identify the best new control tools to use against the vector Aedes aegypti. In this study, we investigated Ae. aegypti sugar feeding strategies in Bamako, Mali, to determine if this species can be controlled effectively using attractive toxic sugar baits (ATSB). METHODOLOGY: We determined the relative attraction of Ae. aegypti males and females to a variety of sugar sources including flowers, fruits, seedpods, and honeydew in the laboratory and using plant-baited traps in the field. Next, we observed the rhythm of blood feeding versus sugar feeding activity of Ae. aegypti in vegetation and in open areas. Finally, we studied the effectiveness of spraying vegetation with ATSB on Ae. aegypti in sugar rich (lush vegetation) and in sugar poor (sparse vegetation) urban environments. PRINCIPAL FINDINGS: Male and female laboratory sugar feeding rates within 24 h, on 8 of 16 plants offered were over 80%. The survival rates of mosquitoes on several plant sources were nearly as long as that of controls maintained on sucrose solution. In the field, females were highly attracted to 11 of 20 sugar sources, and 8 of these were attractive to males. Peak periods of host attraction for blood-feeding and sugar feeding in open areas were nearly identical and occurred shortly after sunrise and around sunset. In shaded areas, the first sugar-seeking peak occurred between 11:30 and 12:30 while the second was from 16:30 to 17:30. In a 50-day field trial, ATSB significantly reduced mean numbers of landing / biting female Ae. aegypti in the two types of vegetation. At sugar poor sites, the mean pre-treatment catch of 20.51 females on day 14 was reduced 70-fold to 0.29 on day 50. At sugar rich sites, the mean pre-treatment catch of 32.46 females on day 14 was reduced 10-fold to a mean of 3.20 females on day 50. CONCLUSIONS: This is the first study to show how the vector Ae. aegypti depends on environmental resources of sugar for feeding and survival. The demonstration that Ae. aegypti populations rapidly collapsed after ATSB treatment, in both sugar rich and sugar poor environments, is strong evidence that Ae. aegypti is sugar-feeding frequently. Indeed, this study clearly demonstrates that Ae. aegypti mosquitoes depend on natural sugar resources, and a promising new method for vector control, ATSB, can be highly effective in the fight against Aedes-transmitted diseases.

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

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

The invasive shrub Prosopis juliflora enhances the malaria parasite transmission capacity of Anopheles mosquitoes: a habitat manipulation experiment.

BACKGROUND: A neglected aspect of alien invasive plant species is their influence on mosquito vector ecology and malaria transmission. Invasive plants that are highly attractive to Anopheles mosquitoes provide them with sugar that is critical to their survival. The effect on Anopheles mosquito populations was examined through a habitat manipulation experiment that removed the flowering branches of highly attractive Prosopis juliflora from selected villages in Mali, West Africa. METHODS: Nine villages in the Bandiagara district of Mali were selected, six with flowering Prosopis juliflora, and three without. CDC-UV light traps were used to monitor their Anopheles spp. vector populations, and recorded their species composition, population size, age structure, and sugar feeding status. After 8 days, all of the flowering branches were removed from three villages and trap catches were analysed again. RESULTS: Villages where flowering branches of the invasive shrub Prosopis juliflora were removed experienced a threefold drop in the older more dangerous Anopheles females. Population density dropped by 69.4% and the species composition shifted from being a mix of three species of the Anopheles gambiae complex to one dominated by Anopheles coluzzii. The proportion of sugar fed females dropped from 73 to 15% and males from 77 to 10%. CONCLUSIONS: This study demonstrates how an invasive plant shrub promotes the malaria parasite transmission capacity of African malaria vector mosquitoes. Proper management of invasive plants could potentially reduce mosquito populations and malaria transmission.

A novel window entry/exit trap for the study of endophilic behavior of mosquitoes.

To overcome the limitations of currently used window entry/exit traps, we developed an efficient new glue net entry/exit trap (GNT) that is economical, easily transported and assembled, and can be utilized for a variety of studies which aim to investigate the dynamics of mosquito movements between indoor and outdoor habitats. Cage experiments were conducted to determine what percentage of mosquitoes trying to pass through the netting are actually being caught. The GNT caught 97% of female and 98% of male Anopheles gambiae s.s., as well as 97.5% of female and 98% of male Culex pipiens attempting to cross into a bait chamber adjoining the release cage. During a six day field study, the bedroom windows of 12 homes in Mali were fitted with entry/exit GNTs. Traps without glue were fitted over the inside and outside bedroom windows of an additional 12 homes as a control. A total of 446 An. gambiae s.l. were caught attempting to exit dwellings while 773 An. gambiae s.l. were caught attempting to enter. The number of males and females attempting to exit dwellings were roughly similar (215 and 231 respectively) while there was a slight difference in the number of males and females trying to enter (382 and 430 respectively). Pyrethrum spray catches (PSC's) conducted inside the dwellings on the last day of the experiment yielded only six females and a single male.

Modelling optimum use of attractive toxic sugar bait stations for effective malaria vector control in Africa.

BACKGROUND: The development of insecticide resistance and the increased outdoor-biting behaviour of malaria vectors reduce the efficiency of indoor vector control methods. Attractive toxic sugar baits (ATSBs), a method targeting the sugar-feeding behaviours of vectors both indoors and outdoors, is a promising supplement to indoor tools. The number and configuration of these ATSB stations needed for malaria control in a community needs to be determined. METHODS: A hypothetical village, typical of those in sub-Saharan Africa, 600 × 600 m, consisting of houses, humans and essential resource requirements of Anopheles gambiae (sugar sources, outdoor resting sites, larval habitats) was simulated in a spatial individual-based model. Resource-rich and resource-poor environments were simulated separately. Eight types of configurations and different densities of ATSB stations were tested. Anopheles gambiae population size, human biting rate (HBR) and entomological inoculation rates (EIR) were compared between different ATSB configurations and densities. Each simulated scenario was run 50 times. RESULTS: Compared to the outcomes not altered by ATSB treatment in the control scenario, in resource-rich and resource-poor environments, respectively, the optimum ATSB treatment reduced female abundance by 98.22 and 91.80 %, reduced HBR by 99.52 and 98.15 %, and reduced EIR by 99.99 and 100 %. In resource-rich environments, n × n grid design, stations at sugar sources, resting sites, larval habitats, and random locations worked better in reducing vector population and HBRs than other configurations (P < 0.0001). However, there was no significant difference of EIR reductions between all ATSB configurations (P > 0.05). In resource-poor environments, there was no significant difference of female abundances, HBRs and EIRs between all ATSB configurations (P > 0.05). The optimum number of ATSB stations was about 25 for resource-rich environments and nine for resource-poor environments. CONCLUSIONS: ATSB treatment reduced An. gambiae population substantially and reduced EIR to near zero regardless of environmental resource availability. In resource-rich environments, dispersive configurations worked better in reducing vector population, and stations at or around houses worked better in preventing biting and parasite transmission. In resource-poor environments, all configurations worked similarly. Optimum numbers of bait stations should be adjusted according to seasonality when resource availability changes.

Efficacy of attractive toxic sugar baits (ATSB) against Aedes albopictus with garlic oil encapsulated in beta-cyclodextrin as the active ingredient.

We tested the efficacy of attractive toxic sugar bait (ATSB) with garlic oil microencapsulated in beta-cyclodextrin as active ingredient against Aedes albopictus in suburban Haifa, Israel. Two three-acre gardens with high numbers of Ae. albopictus were selected for perimeter spray treatment with ATSB and ASB (bait containing no active ingredient). Baits were colored with food dye to verify feeding of the mosquitoes. The mosquito population was monitored by human landing catches and sweep net catches in the surrounding vegetation. Experiments lasted for 44 days. Treatment occurred on day 13. The mosquito population collapsed about 4 days after treatment and continued to drop steadily for 27 days until the end of the study. At the experimental site the average pre-treatment landing rate was 17.2 per 5mins. Two days post-treatment, the landing rate dropped to 11.4, and continued to drop to an average of 2.6 during the following 26 days. During the same period, the control population was stable. Few sugar fed females (8-10%) approached a human bait and anthrone tests showed relatively small amounts of sugar within their crop/gut. Around 60-70 % of males caught near our human bait were sugar positive which may indicate that the males were feeding on sugar for mating related behavior. From the vegetation treated with the toxic bait, we recovered significantly fewer (about 10-14%) males and females stained by ATSB than at the ASB-treated control. This may indicate that the toxic baits alter the resting behavior of the poisoned mosquitoes within the vegetation. Almost no Ae. albopictus females (5.2±1.4) approached human bait after treatment with ATSB. It therefore appears that microencapsulated garlic oil is an effective pesticide against Ae. albopictus when used in an ATSB system.

Indoor use of attractive toxic sugar bait (ATSB) to effectively control malaria vectors in Mali, West Africa.

BACKGROUND: Attractive toxic sugar bait (ATSB) solutions containing any gut toxins can be either sprayed on plants or used in simple bait stations to attract and kill sugar-feeding female and male mosquitoes. This field study in Mali demonstrates the effect of ATSB bait stations inside houses as a vector control method that targets and kills endophilic African malaria vectors. METHODS: The studies were conducted in five villages located near the River Niger, Mali. Baseline village-wide assessments of densities for female and male Anopheles gambiae sensu lato were performed by pyrethrum spray collections (PSC) in ten houses in each of five villages. To determine the rate of mosquito feeding on bait stations, one bait station per house containing attractive sugar bait (ASB) (without toxin) plus a food dye marker, was set up in ten houses in each of the five villages. PSC collections were conducted on the following day and the percentage of female and male mosquitoes that had fed was determined by visual inspection for the dye marker. Then, a 50-day field trial was done. In an experimental village, one bait station containing ATSB (1% boric acid active ingredient) was placed per bedroom (58 bedrooms), and indoor densities of female and male An. gambiae s.l. were subsequently determined by PSC, and female mosquitoes were age graded. RESULTS: In the five villages, the percentages of An. gambiae s.l. feeding inside houses on the non-toxic bait stations ranged from 28.3 to 53.1% for females and 36.9 to 78.3% for males. Following ATSB indoor bait station presentation, there was a significant reduction, 90% in female and 93% in male populations, of An. gambiae s.l. at the experimental village. A 3.8-fold decrease in the proportion of females that had undergone four or more gonotrophic cycles was recorded at the experimental village, compared to a 1.2-fold increase at the control village. CONCLUSION: The field trial demonstrates that An. gambiae s.l. feed readily from ATSB bait stations situated indoors, leading to a substantial reduction in the proportion of older female mosquitoes. This study demonstrates that ATSB inside houses can achieve impressive malaria vector control in Africa.

Formulation of attractive toxic sugar bait (ATSB) with safe EPA-exempt substance significantly diminishes the Anopheles sergentii population in a desert oasis.

Attractive toxic sugar bait (ATSB) is a highly effective method which targets mosquitoes based on their sugar foraging behavior, by presenting baits of attractive compounds in combination with sugar and oral toxin to local mosquito populations. Environmental concerns and insecticide selection-pressure have prompted investigations of novel, ecologically-harmless substances which can be used as insecticides. This study examined the efficacy of microencapsulated garlic-oil as the oral toxin component of ATSB for controlling Anopheles sergentii populations inhabiting desert-surrounded wetlands in Israel. ATSB solution containing 0.4% encapsulated garlic oil was applied to local vegetation around a streamlet located in the lower Jordan Valley. To determine the propensity of bait ingestion, and assess the potential ecological impact of the method, mosquito and non-target specimens were collected and tested for the presence of natural plant- or attractive sugar bait (ASB)-derived sugars. Over the experimental period, biting-pressure values in the ATSB treatment site decreased by 97.5%, while at the control site, treated with non-toxic ASB, no significant changes were observed. Approximately 70% of the mosquitoes collected before both treatments, as well as those captured following the application of ASB at the control site, were found to have ingested sugar prior to capture. Non-target insects were minimally affected by the treatment when ATSB was applied to foliage of non-flowering plants. Of the non-Diptera species, only 0.7% of the sampled non-target insects were found to have ingested ASB-solution which was applied to green vegetation, compared with 8.5% which have foraged on ASB-derived sugars applied to flowering plants. Conversely, a high proportion of the non-target species belonging to the order Diptera, especially non-biting midges, were found to have ingested foliage-applied ASB, with more than 36% of the specimens collected determined to have foraged on bait-derived sugars. These results prove that food-grade, EPA-exempt microencapsulated garlic oil is a highly effective insecticide which can be utilized for mosquito population control. The relatively short half-life of this active ingredient makes it a suitable for use in areas where repeated application is possible, limiting the accumulation of deleterious compounds and ensuring minimal environmental impact when applied in accordance with label recommendations.

Control of sand flies with attractive toxic sugar baits (ATSB) and potential impact on non-target organisms in Morocco.

BACKGROUND: The persistence and geographical expansion of leishmaniasis is a major public health problem that requires the development of effective integrated vector management strategies for sand fly control. Moreover, these strategies must be economically and environmentally sustainable approaches that can be modified based on the current knowledge of sand fly vector behavior. The efficacy of using attractive toxic sugar baits (ATSB) for sand fly control and the potential impacts of ATSB on non-target organisms in Morocco was investigated. METHODS: Sand fly field experiments were conducted in an agricultural area along the flood plain of the Ourika River. Six study sites (600 m x 600 m); three with "sugar rich" (with cactus hedges bearing countless ripe fruits) environments and three with "sugar poor" (green vegetation only suitable for plant tissue feeding) environments were selected to evaluate ATSB, containing the toxin, dinotefuran. ATSB applications were made either with bait stations or sprayed on non-flowering vegetation. Control sites were established in both sugar rich and sugar poor environments. Field studies evaluating feeding on vegetation treated with attractive (non-toxic) sugar baits (ASB) by non-target arthropods were conducted at both sites with red stained ASB applied to non-flowering vegetation, flowering vegetation, or on bait stations. RESULTS: At both the sites, a single application of ATSB either applied to vegetation or bait stations significantly reduced densities of both female and male sand flies (Phlebotomus papatasi and P. sergenti) for the five-week trial period. Sand fly populations were reduced by 82.8% and 76.9% at sugar poor sites having ATSB applied to vegetation or presented as a bait station, respectively and by 78.7% and 83.2%, respectively at sugar rich sites. The potential impact of ATSB on non-targets, if applied on green non-flowering vegetation and bait stations, was low for all non-target groups as only 1% and 0.7% were stained with non-toxic bait respectively when monitored after 24 hours. CONCLUSIONS: The results of this field study demonstrate ATSB effectively controls both female and male sand flies regardless of competing sugar sources. Furthermore, ATSB applied to foliar vegetation and on bait stations has low non-target impact.

Decrease of larval and subsequent adult Anopheles sergentii populations following feeding of adult mosquitoes from Bacillus sphaericus-containing attractive sugar baits.

BACKGROUND: Bacillus sphaericus is a mosquito-larvae pathogen which proliferates in the host cadavers, spreading and preserving the infection within the larval habitats for prolonged periods. In this pilot field study, we presented B. sphaericus-containing attractive sugar baits (ASB) to wild Anopheles sergentii adults, with the assumption that bait-fed, B. sphaericus-carrying mosquitoes are able to efficiently transmit the pathogen to the larval habitats, causing larval mortality and leading to a decrease in the subsequent adult population. METHODS: The experiment was conducted over 75 days in two desert-surrounded streamlets. Blooming Ochradenus baccatus bushes were sprayed with bait solutions consisting of sugar and food dye marker solutions, with or without B. sphaericus at the experimental and control streamlets, respectively. Adult mosquito and larvae numbers were monitored before and after the treatment application, and the proportion of bait-fed adults was determined by visual inspection for dye presence. RESULTS: Presence of food dye confirmed a large fraction of the adult mosquito population (70%-75%) readily ingested Bacillus sphaericus- containing bait. By the end of the study period, the larval population at the experimental site was six-fold smaller than the concurrent larval population at the control site. The ensuing adult An. sergentii population was also reduced to about 60% at the experimental site, while the adult mosquito population at the control site had increased 2.4 fold over the same time-frame. The reduction in adult mosquito numbers became apparent after a lag time (10 days), suggesting the treatment had minimal effect on adult longevity, also indicated by the post-treatment increase in the proportion of old mosquitoes and concomitant decrease in the proportion of young mosquitoes. CONCLUSIONS: Presentation of B. sphaericus-containing ASB substantially impacts the larval population, which in turn leads to a significant reduction of the ensuing numbers of adult mosquitoes. Although such outcomes may be the result of other causes, these preliminary results raise the possibility that adult mosquitoes can efficiently transmit the pathogen into the larval habitats. The transfer of B. sphaericus via contaminated adult mosquito carriers may allow introduction of pathogens to breeding places which are dispersed, hard to find, or difficult to access.

A spatial individual-based model predicting a great impact of copious sugar sources and resting sites on survival of Anopheles gambiae and malaria parasite transmission.

BACKGROUND: Agent-based modelling (ABM) has been used to simulate mosquito life cycles and to evaluate vector control applications. However, most models lack sugar-feeding and resting behaviours or are based on mathematical equations lacking individual level randomness and spatial components of mosquito life. Here, a spatial individual-based model (IBM) incorporating sugar-feeding and resting behaviours of the malaria vector Anopheles gambiae was developed to estimate the impact of environmental sugar sources and resting sites on survival and biting behaviour. METHODS: A spatial IBM containing An. gambiae mosquitoes and humans, as well as the village environment of houses, sugar sources, resting sites and larval habitat sites was developed. Anopheles gambiae behaviour rules were attributed at each step of the IBM: resting, host seeking, sugar feeding and breeding. Each step represented one second of time, and each simulation was set to run for 60 days and repeated 50 times. Scenarios of different densities and spatial distributions of sugar sources and outdoor resting sites were simulated and compared. RESULTS: When the number of natural sugar sources was increased from 0 to 100 while the number of resting sites was held constant, mean daily survival rate increased from 2.5% to 85.1% for males and from 2.5% to 94.5% for females, mean human biting rate increased from 0 to 0.94 bites per human per day, and mean daily abundance increased from 1 to 477 for males and from 1 to 1,428 for females. When the number of outdoor resting sites was increased from 0 to 50 while the number of sugar sources was held constant, mean daily survival rate increased from 77.3% to 84.3% for males and from 86.7% to 93.9% for females, mean human biting rate increased from 0 to 0.52 bites per human per day, and mean daily abundance increased from 62 to 349 for males and from 257 to 1120 for females. All increases were significant (P < 0.01). Survival was greater when sugar sources were randomly distributed in the whole village compared to clustering around outdoor resting sites or houses. CONCLUSIONS: Increases in densities of sugar sources or outdoor resting sites significantly increase the survival and human biting rates of An. gambiae mosquitoes. Survival of An. gambiae is more supported by random distribution of sugar sources than clustering of sugar sources around resting sites or houses. Density and spatial distribution of natural sugar sources and outdoor resting sites modulate vector populations and human biting rates, and thus malaria parasite transmission.

Control of Aedes albopictus with attractive toxic sugar baits (ATSB) and potential impact on non-target organisms in St. Augustine, Florida.

The purpose of this study was to test the efficacy of bait stations and foliar applications containing attractive toxic sugar baits (ATSB) and eugenol to control Aedes albopictus. At the same time, the potential impact of these control methods was evaluated on non-target organisms. The study was conducted at five tire sites in St. Augustine, Florida. A. albopictus populations were significantly reduced with ATSB-eugenol applications applied directly to non-flowering vegetation and as bait stations compared with non-attractive sugar baits and control. The application of ATSB made to non-flowering vegetation resulted in more significant reductions of mosquito populations compared to the application of ATSB presented in a bait station. Over 5.5% of the non-targets were stained in the flowering vegetation application site. However, when the attractive sugar bait application was made to non-flowering vegetation or presented in bait stations, the impact on non-target insects was very low for all non-target orders as only 0.6% of the individual insects were stained with the dye from the sugar solutions, respectively. There were no significant differences between the staining of mosquitoes collected in flowering vegetation (206/1000) or non-flowering vegetation (242/1000) sites during the non-target evaluation. Our field studies support the use of eugenol as an active ingredient for controlling the dengue vector A. albopictus when used as an ATSB toxin and demonstrates potential use in sub-tropical and tropical environments for dengue control.

Attractive toxic sugar baits: control of mosquitoes with the low-risk active ingredient dinotefuran and potential impacts on nontarget organisms in Morocco.

We evaluated the efficacy of attractive toxic sugar baits (ATSB) in the laboratory and field with the low-risk active ingredient dinotefuran against mosquito populations. Preliminary laboratory assays indicated that dinotefuran in solution with the sugar baits was ingested and resulted in high mortality of female Culex quinquefasciatus Say and Aedes aegypti Linnaeus. Field studies demonstrated >70% reduction of mosquito populations at 3 wk post-ATSB application. Nontarget feeding of seven insect orders-Hymenoptera, Lepidoptera, Coleoptera, Diptera, Hemiptera, Orthoptera, and Neuroptera-was evaluated in the field after application of attractive sugar baits (ASB) on vegetation by dissecting the guts and searching for food dye with a dissecting microscope. Nontargets were found stained with ASB 0.9% of the time when the application was applied on green nonflowering vegetation. Only two families were significantly impacted by the ASB application: Culicidae (mosquitoes) and Chironomidae (nonbiting midges) of the order Diptera. Pollinators of the other insect orders were not significantly impacted. No mortality was observed in the laboratory studies with predatory nontargets, wolf spiders or ground beetles, after feeding for 3 d on mosquitoes engorged on ATSB applied to vegetation. Overall, this novel control strategy had little impact on nontarget organisms, including pollinators and beneficial insects, and was effective at controlling mosquito populations, further supporting the development of ATSB for commercial use.

Quantifying the mosquito's sweet tooth: modelling the effectiveness of attractive toxic sugar baits (ATSB) for malaria vector control.

BACKGROUND: Current vector control strategies focus largely on indoor measures, such as long-lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS); however mosquitoes frequently feed on sugar sources outdoors, inviting the possibility of novel control strategies. Attractive toxic sugar baits (ATSB), either sprayed on vegetation or provided in outdoor bait stations, have been shown to significantly reduce mosquito densities in these settings. METHODS: Simple models of mosquito sugar-feeding behaviour were fitted to data from an ATSB field trial in Mali and used to estimate sugar-feeding rates and the potential of ATSB to control mosquito populations. The model and fitted parameters were then incorporated into a larger integrated vector management (IVM) model to assess the potential contribution of ATSB to future IVM programmes. RESULTS: In the Mali experimental setting, the model suggests that about half of female mosquitoes fed on ATSB solution per day, dying within several hours of ingesting the toxin. Using a model incorporating the number of gonotrophic cycles completed by female mosquitoes, a higher sugar-feeding rate was estimated for younger mosquitoes than for older mosquitoes. Extending this model to incorporate other vector control interventions suggests that an IVM programme based on both ATSB and LLINs may substantially reduce mosquito density and survival rates in this setting, thereby substantially reducing parasite transmission. This is predicted to exceed the impact of LLINs in combination with IRS provided ATSB feeding rates are 50% or more of Mali experimental levels. In addition, ATSB is predicted to be particularly effective against Anopheles arabiensis, which is relatively exophilic and therefore less affected by IRS and LLINs. CONCLUSIONS: These results suggest that high coverage with a combination of LLINs and ATSB could result in substantial reductions in malaria transmission in this setting. Further field studies of ATSB in other settings are needed to assess the potential of ATSB as a component in future IVM malaria control strategies.

Diurnal resting behavior of adult Culex pipiens in an arid habitat in Israel and possible control measurements with toxic sugar baits.

The distribution of resting Culex pipiens s.l., L. in vegetation at the margins of breeding sites and the effects of a narrow, surrounding, sprayed belt of sugar, food dye and toxin on adult mosquitoes were studied near two pairs of control and experimental sewage ponds close to human habitation in the Judean hills. Control belts were without toxin. A sprayed belt of sugar and toxin 0.5 m from the water gradually reduced the population to an average of 38.3 mosquitoes per trap, 7.6% of the highest catch, which was 504.6 mosquitoes per trap in the control site. In the second experiment, in which bait belts were 5 m from the water, the toxic bait spraying was followed by a rise in catches from 207.9 to 274.9 mosquitoes. This was 41% of the 670.2 mosquitoes per trap in the parallel control site. In areas without toxin treatment, diurnal catches by net amounted to 20,705 mosquitoes. Of these, 86.1% (17,825) were caught within 1m of the water while only 8.2% (1701) were caught at a distance of 3 m. The remainders were caught up to 20 m away. Parity status was determined for female samples caught by net. In areas without toxin, parous females accounted for 37% of the catch and 13.2% were young, meconium containing specimens. The population diminished following spraying of toxic bait 1m from the water and included 13% parous females and 17.6% had meconium in the gut.

Tree-hole breeding mosquitoes in Israel.

A survey was conducted to evaluate the number of tree-hole breeding mosquito species and their distribution in the six principal woodland types in Israel. Out of approximately 3,000 mature trees examined, only 38 contained holes that retained water for extended periods of time, and breeding mosquitoes were observed in 27 of them. Two specialized tree-hole breeders, Aedes pulchritarsis Rondani and Aedes geniculatus Oliver, were found breeding at several sites in northern Israel, always at locations 500 m above sea level (a.s.l) and with high annual precipitation. Aedes albopictus Skuse which, in Israel, is known as an opportunistic container breeder, was found in this study to have adapted remarkably well to breeding in tree holes and was found in most forest types investigated and in most tree species which had adequate tree holes. Two other species, Culiseta annulata Schrank and Culex pipiens Linnaeus instars, were found in one of the tree holes, but did not survive to reach maturity.

An annotated checklist of the horse flies (Diptera: Tabanidae) of Lebanon with remarks on ecology and zoogeography: Pangoniinae and Chrysopsinae.

Knowledge of the horse fly fauna (Diptera: Tabanidae) of Lebanon is fragmentary, while the local fauna of most neighboring countries has been fairly well researched. Within the framework of the 20-year project "The ecology and zoogeography of the Lepidoptera of the Near East," we regularly collected biting flies in the whole region, including Lebanon. During this time we recorded 14 horse fly species for two subfamilies in Lebanon: four Pangoniinae and ten Chrysopsinae. Only a single species, Chrysops flavipes Meigen, 1804, was known previously in Lebanon, but the following four Pangoniinae: Pangonius haustellatus (Fabricius, 1781), Pangonius obscuratus Loew, 1859, Pangonius argentatus (Szilady, 1923), and Pangonius fulvipes (Loew, 1859) and nine Chrysopsinae: Silvius appendiculatus Macquart, 1846, Silvius ochraceus Loew, 1858, Nemorius irritans (Ricardo, 1901), Nemorius vitripennis (Meigen, 1820), Chrysops buxtoniAusten, 1922, Chrysops compactusAusten, 1924, Chrysops caecutiens (Linnaeus, 1758), Chrysops italicus Meigen, 1804, and Chrysops hamatus Loew, 1858 are new records for the Lebanese fauna. The Tabanidae fauna of Lebanon is completely Palearctic and most species are of a Mediterranean distribution type. Lebanon or nearby northern Israel appears to be in the Levant, the southern geographical distribution border for the Pangoniinae and Chrysopsinae.

Attractive toxic sugar bait (ATSB) methods decimate populations of Anopheles malaria vectors in arid environments regardless of the local availability of favoured sugar-source blossoms.

BACKGROUND: Attractive toxic sugar bait (ATSB) methods are a new and promising "attract and kill" strategy for mosquito control. Sugar-feeding female and male mosquitoes attracted to ATSB solutions, either sprayed on plants or in bait stations, ingest an incorporated low-risk toxin such as boric acid and are killed. This field study in the arid malaria-free oasis environment of Israel compares how the availability of a primary natural sugar source for Anopheles sergentii mosquitoes: flowering Acacia raddiana trees, affects the efficacy of ATSB methods for mosquito control. METHODS: A 47-day field trial was conducted to compare impacts of a single application of ATSB treatment on mosquito densities and age structure in isolated uninhabited sugar-rich and sugar-poor oases relative to an untreated sugar-rich oasis that served as a control. RESULTS: ATSB spraying on patches of non-flowering vegetation around freshwater springs reduced densities of female An. sergentii by 95.2% in the sugar-rich oasis and 98.6% in the sugar-poor oasis; males in both oases were practically eliminated. It reduced daily survival rates of female An. sergentii from 0.77 to 0.35 in the sugar-poor oasis and from 0.85 to 0.51 in the sugar-rich oasis. ATSB treatment reduced the proportion of older more epidemiologically dangerous mosquitoes (three or more gonotrophic cycles) by 100% and 96.7%, respectively, in the sugar-poor and sugar-rich oases. Overall, malaria vectorial capacity was reduced from 11.2 to 0.0 in the sugar-poor oasis and from 79.0 to 0.03 in the sugar-rich oasis. Reduction in vector capacity to negligible levels days after ATSB application in the sugar-poor oasis, but not until after 2 weeks in the sugar-rich oasis, show that natural sugar sources compete with the applied ATSB solutions. CONCLUSION: While readily available natural sugar sources delay ATSB impact, they do not affect overall outcomes because the high frequency of sugar feeding by mosquitoes has an accumulating effect on the probability they will be attracted to and killed by ATSB methods. Operationally, ATSB methods for malaria vector control are highly effective in arid environments regardless of competitive, highly attractive natural sugar sources in their outdoor environment.