Sugar Baits Research Articles

Previous diet affects the amount but not the type of bait consumed by an invasive ant.

Recent research on multiple invasive ant species has revealed the importance of carbohydrates for achieving high activity levels and outcompeting native ants. However, comparatively little is known about the role of diet and macronutrient preferences for uptake of insecticidal baits used to control invasive ants. We tested whether diet affected yellow crazy ant (Anoplolepis gracilipes Fr Smith) survival and behavior, and whether bait preference would be complementary to past diet. We found that colonies fed only crickets for 28 days had fewer live workers and queens, and less brood per live queen than colonies fed crickets + honeydew but did not differ significantly from colonies fed only honeydew. Colonies that had been fed only crickets were more active (as assessed by interaction with a novel object), retrieved 16-17 times more bait per worker overall, and consumed more of the six bait types than cricket + honeydew and honeydew-only fed colonies. However, prior diet did not affect bait choice. The two highest sugar bait formulations combined accounted for most of the bait consumed across all treatments (cricket-only 74.8% ± 28.1; cricket + honeydew 69.2% ± 12.4; honeydew-only 62.5% ± 30.4). Yellow crazy ant colonies fare better without protein than without carbohydrates. Yellow crazy ants ate the most bait when fed only crickets but did not choose baits complementary to their previous diet. Baits in a sugar-rich carrier may be most effective for the control of yellow crazy ants, regardless of the relative availability of macronutrients. © 2019 Society of Chemical Industry.

Impact of sugar composition on meal distribution, longevity, and insecticide toxicity in Aedes aegypti

Toxic Sugar Baits (TSBs) are an inexpensive and field-applicable approach to deliver a variety of insecticides to sugar-seeking mosquitoes. We reasoned that carbohydrate chemistry could alter the performance and efficacy of TSBs. In this study, the uptake, distribution, and survival of female Aedes aegypti provided with twelve different aqueous sugar meals was recorded. Sucrose, a standard control sugar used in mosquito rearing, is always diverted to the ventral diverticulum upon ingestion; but other sugars that might be found in nectar (e.g., maltose, mannose, and raffinose) dispersed to both the diverticulum and midgut. Sugar meals composed of arabinose, lactose, or cellobiose significantly reduced survival of Ae. aegypti compared to sucrose controls, with or without the addition of boric acid insecticide. The addition of arabinose to a TSB comprised of sucrose and boric acid reduced the survival of Ae. aegypti even when non-toxic sugar meals were readily available. In choice assays, Ae. aegypti were equally likely to feed on TSBs containing arabinose despite the toxicity associated with arabinose ingestion. TSBs typically contain broad spectrum insecticides; insecticidal RNA species that induce species-specific gene silencing are a potential alternative. To assess the potential of RNA delivery in a TSB, biodistribution of double-stranded RNA (dsRNA), was tracked after per os delivery in different sugar meals. None of the sugars tested facilitated uptake of dsRNA into midgut epithelia or other tissues. Overall, sourcing sugar baits from sources containing sugars with toxic properties may improve TSB efficacy in the field.

Nationwide seroprevalence, spatial distribution and risk factors of Leishmania in Jordan

Objective: To explore the seroprevalence, spatial distribution and risk factors for Leishmania seropositivity in Jordan. Methods: Blood samples from 872 apparently healthy participants were randomly selected from 11 governorates in Jordan and tested for anti-Leishmania K39 IgG. Risk factors (animal ownership and agriculture practices) and demographic data were also collected using pre-tested and validated questionnaire. Results: Overall, 2.52% of participants were seropositive for Leishmania spp. Participants living in the Jordan Valley plateau had significantly greater odds (adjusted odds ratio = 3.70, 95% CI 1.37-9.93) of seropositivity than those living in the Highlands after adjustment for age. Conclusions: This study supports the intermittent reports of cutaneous leishmaniasis outbreaks in the Jordan Valley. Vector control measures in the Jordan Valley should be considered, including insecticide treated bed nets, sugar baits and using flowering plants to attract and trap Phlebotomus papatasi sand flies. Active surveillance in the Jordan Valley is also recommended in light of this and other reports.

Transmission blocking sugar baits for the control of Leishmania development inside sand flies using environmentally friendly beta-glycosides and their aglycones

BackgroundThe sand fly Lutzomyia longipalpis is the main vector of American visceral leishmaniasis, a disease caused by parasites of the genus Leishmania. Adults of this insect feed on blood (females only) or sugar from plant sources, but their digestion of carbohydrates is poorly studied. Beta-glycosides as esculin and amygdalin are plant compounds and release toxic compounds as esculetin and mandelonitrile when hydrolyzed. Beta-glucosidase and trehalase are essential enzymes in sand fly metabolism and participate in sugar digestion. It is therefore possible that the toxic portions of these glycosides, released during digestion, affect sand fly physiology and the development of Leishmania.ResultsWe tested the oral administration to sand flies of amygdalin, esculin, mandelonitrile, and esculetin in the sugar meal. These compounds significantly decreased the longevity of Lutzomyia longipalpis females and males. Lutzomyia longipalpis adults have significant hydrolytic activities against esculin and feeding on this compound cause changes in trehalase and β-glucosidase activities. Female trehalase activity is inhibited in vitro by esculin. Esculin is naturally fluorescent, so its ingestion may be detected and quantified in whole insects or tissue samples stored in methanol. Mandelonitrile neither affected the amount of sugar ingested by sand flies nor showed repellent activity. Our results show that mandelonitrile significantly reduces the viability of L. amazonensis, L. braziliensis, L. infantum and L. mexicana, in a concentration-dependent manner. Esculetin caused a similar effect, reducing the number of L. infantum and L. mexicana. Female L. longipalpis fed on mandelonitrile had a reduction in the number of parasites and prevalence of infection after seven days of infection with L. mexicana, either by counting in a Neubauer chamber or by qPCR assays.ConclusionsGlycosides have significant effects on L. longipalpis longevity and metabolism and also affect the development of parasites in culture and inside the insect. These observations might help to conceptualize new vector control strategies using transmission blocking sugar baits.

Foraging preferences of ants on a heterogeneous Brazilian sandy shore habitat

1. Ants may select their food in response to nutritional needs of the colony and forage in a way that optimises a complementary nutrition. Even though resource availability is known to affect ant colony and individual health, there is still no study that has investigated the plastic preferences of ants according to spatial resource availability in naturally heterogeneous conditions.2. Beaches are great biomes to test spatial foraging preference because a complete absence of nectaries can be found. Dorymyrmex nigra Pergande 1896 was found inhabiting a beach in southeastern Brazil, in which nectar sources are heterogeneously distributed. This study tested whether the foraging preference to sugar baits depended on the availability of nectar sources surrounding the nests.3. We found that more D. nigra workers foraged on sugar baits when the colonies lacked naturally occurring nectar in their vicinity compared with colonies with abundant nectar nearby.4. These results show that the foraging preference of ants depends upon resource availability. This is the first study to use a natural mosaic of resource availability to show that resource preference of ants is plastic and varies spatially.

Delivery of a Genetically Marked Serratia AS1 to Medically Important Arthropods for Use in RNAi and Paratransgenic Control Strategies

Understanding how arthropod vectors acquire their bacteria is essential for implementation of paratransgenic and RNAi strategies using genetically modified bacteria to control vector-borne diseases. In this study, a genetically marked Serratia AS1 strain expressing the mCherry fluorescent protein (mCherry-Serratia) was used to test various acquisition routes in six arthropod vectors including Anopheles stephensi, Culex pipiens, Cx. quinquefaciatus, Cx. theileri, Phlebotomus papatasi, and Hyalomma dromedarii. Depending on the species, the bacteria were delivered to (i) mosquito larval breeding water, (ii) host skin, (iii) sugar bait, and (iv) males (paratransgenic). The arthropods were screened for the bacteria in their guts or other tissues. All the hematophagous arthropods were able to take the bacteria from the skin of their hosts while taking blood meal. The mosquitoes were able to take up the bacteria from the water at larval stages and to transfer them transstadially to adults and finally to transfer them to the water they laid eggs in. The mosquitoes were also able to acquire the bacteria from male sperm. The level of bacterial acquisition was influenced by blood feeding time and strategies (pool or vessel feeding), dipping in water and resting time of newly emerged adult mosquitoes, and the disseminated tissue/organ. Transstadial, vertical, and venereal bacterial acquisition would increase the sustainability of the modified bacteria in vector populations and decrease the need for supplementary release experiments whereas release of paratransgenic males that do not bite has fewer ethical issues. Furthermore, this study is required to determine if the modified bacteria can be introduced to arthropods in the same routes in nature.

Short-term movement of Phlebotomus argentipes (Diptera: Psychodidae) in a visceral leishmaniasis-endemic village in Bihar, India.

Visceral leishmaniasis (VL), transmitted by the sand fly, Phlebotomus argentipes, is frequently reported on the Indian subcontinent where its basic ecology is largely unknown. Our objective was to evaluate the effectiveness of sugar solution (10%), containing colored food dye (0.5%) applied to peridomestic vegetation, to mark P. argentipes and subsequently estimate horizontal movement by capturing dye-marked specimens in CDC light traps in a village in Bihar, India. From September 30 to November 27, 2016, a total of 667 captured sand flies were successfully marked using sugar baits, of which 608 were P. argentipes (~91.2%). Although the majority of P. argentipes were captured <100 m from the respective marking sites, a significantly greater proportion of females (15.7%) was captured >100 m from marking sites when compared to males (3.1%). Sand flies that ingested sugar bait were only collected from areas containing >eight vegetation types and mature banana plants. The average number of marked P. argentipes captured per trap-night (±SD) <100 m from respective marking sites was greatest in peridomestic vegetation (Males: 0.9 ± 1.97; Females: 0.63 ± 1.44), followed by areas with livestock (Males: 0.66 ± 2.75; Females: 0.24 ± 0.69), and areas with humans only (Males: 0.1 ± 0.36; Females: 0.11 ± 0.31). To our knowledge, this is the only study in Bihar in which sand flies have been marked with food dyes, and the results demonstrate the potential usefulness of food dyes in estimating short-term movement of P. argentipes. Limitations of this experiment are that the number of each trap location type, vegetation composition at marking sites, and distance of all trap sites from marking sites were not homogenous, and the total number of marked sand flies collected were relatively low. In spite of the above limitations, these data should prove useful in developing a large-scale study addressing the caveats. Results of such a study could provide important information regarding the dynamics of VL transmission and inspire managers to pursue alternative means of sand fly control on the Indian subcontinent.

Field assessment of potential sugar feeding stations for disseminating bacteria in a paratransgenic approach to control malaria

BackgroundUsing bacteria to express and deliver anti-parasite molecules in mosquitoes is among the list of genetic tools to control malaria. The introduction and spread of transgenic bacteria through wild adult mosquitoes is one of the major challenges of this strategy. In prospect of future field experiments, an open field study with blank (without bacteria) attractive sugar bait (ASB) was performed under the assumption that transgenic bacteria would be spread to all sugar fed mosquitoes.MethodsTwo types of ASB stations were developed, one with clay pots (CP) placed at mosquito resting sites and one with window entry traps (WET) placed inside inhabited houses. The ASB consisted in either glucose, honey or fruit cocktail solutions. In addition, mark-release-recapture (MRR) experiment of mosquitoes after feeding them with glucose was also conducted to check the proportion of the mosquito population that can be reached by the two ASB stations as well as its suitability to complement the ASB stations for disseminating bacteria.ResultsOverall, 88% of the mosquitoes were collected in the WET_ASB. The CP_ASB stations were much less attractive with the highest average of 82 ± 11 mosquitoes/day in the CP near the wood piles. The proportions of sugar fed mosquitoes upon ASB were low in both type of ASB stations, ~ 2% and ~ 14% in WET and CP, respectively. Honey solution was the most attractive solution compared to the glucose and the fruit cocktail solutions. The recapture rate in the MRR experiment was low: ~ 4.1% over 7 days.ConclusionThe WET_ASB looks promising to disseminate transgenic bacteria to endophilic West Africa Anopheles mosquito. However, this feeding station may not be fully effective and could be combined with the CP_ASB to also target outdoor resting mosquitoes. Overall, efforts are needed to improve the mosquito-feeding rates upon ASB.

Potential of attractive toxic sugar baits for controlling Musca domestica L., Drosophila melanogaster Meigen, and Megaselia scalaris Loew adult flies

Musca domestica, Drosophila melanogaster and Megaselia scalaris (Diptera: Muscidae, Drosophilidae, and Phoridae, respectively) are common urban pest flies. Potential control of these adult fly species using an attractive toxic sugar bait (ATSB) system was evaluated in the laboratory. ATSB, consisting of a combination of mango fruit syrup (as bait) and acetamiprid (as toxic agent), was evaluated and compared with a commercially available fly bait (EndZone™ Insecticide sticker, FMC Corp., USA) containing acetamiprid. Mango syrup without toxicant (ASB) served as the negative control. The ASB + acetamiprid bait was the most effective control mixture based on initial knockdown within 10 min for house flies and 200 min for phorids. The combination produced a higher percentage of mortality in house flies and phorids, respectively, than in fruit flies; however, there was no significant difference between the bait formulations as indicated by the mean mortality of house flies and phorids. Significant differences in Drosophila mean mortality were demonstrated between the ATSB combinations. These findings suggested a fruit-based ASB + acetamiprid system could be used as a cost-effective, alternative for adult fly control.

Harvesting Sugar From Nonflowering Plants: Implications of a Marked Sugar Bait on Honey Bee (Hymenoptera: Apidae) Whole Hive Health.

Honey bees (Apis mellifera) are effective foragers for floral and extra-floral sources of sugars and as a result may easily be exposed to toxicants in the environment, such as pesticides. Toxic sugar baits (TSB) or insecticide-laced baits are designed for insect vector management but may be a danger to foraging honey bees and their hives. During a mosquito movement study at a zoological institution, nonflowering foliage surrounding the zoo was marked with sugar solution dyed with over the counter food-coloring. Mosquitoes and other insects foraged on the marked sugar and were collected within the zoo. Additionally, four of six honey bee hives within the zoo had workers that also foraged the dyed sugar and consequently colored approximately 57 kg of honey within the hives. This observation identifies a possibility route of toxicant accumulation within the hives from TSB and possible exposure may have whole hive health implications not previously described on an individual bee level.

Managing mosquitoes and ticks in a rapidly changing world - Facts and trends.

Vector-borne diseases transmitted by mosquitoes and ticks are on the rise. The effective and sustainable control of these arthropod vectors is a puzzling challenge for public health worldwide. In the present review, I attempted to provide a concise and updated overview of the current mosquito and tick research scenario. The wide array of control tools recently developed has been considered, with special reference to those approved by the World Health Organization Vector Control Advisory Group (WHO VCAG), as well as novel ones with an extremely promising potential to be exploited in vector control programs. Concerning mosquitoes, a major focus has been given on genetically modified vectors, eave tubes, attractive toxic sugar baits (ATSB) and biocontrol agents. Regarding ticks, the recent development of highly effective repellents and acaricides (including nanoformulated ones) as well as behavior-based control tools, has been highlighted. In the second part of the review, key research questions about biology and control of mosquitoes and ticks have been critically formulated. A timely research agenda outlining hot issues to be addressed in mosquito and tick research is provided. Overall, it is expected that the present review will contribute to boost research and applications on successful mosquito and tick control strategies, along with an improved knowledge of their biology and ecology.

Exposure of a diurnal mosquito vector to floral mimics: Foraging responses, feeding patterns, and significance for sugar bait technology

Food location by mosquitoes is mediated by resource-derived olfactory and visual signals. Smell sensation is intermittent and dependent on the environment, whereas visual signals are continual and precede olfactory cues. Success of mosquito bait technology, where olfactory cues are used for attraction, is being impeded by reduced attractiveness. Despite proof that mosquitoes respond to colored objects, including those mimicking floral shape, and that they can discriminate among flowers, the impacts of artificial flowers on foraging remain unexplored. Using artificial flowers with sugar rewards, we examined the foraging responses of Aedes aegypti to various colors in equal choice bioassays. Starved adults were exposed to single flowers with petals of a given color (Single Blue Flowers [SBFs]; Single Red Flowers [SRFs]; Single Yellow Flowers [SYFs]; Single Pink Flowers [SPIFs]; and Single Purple Flowers [SPFs]) and two others with white petals (SWFs). Discrepancies in response time, visitation, feeding, and resting of both sexes were compared between colored flowers and SWFs. Ae. aegypti exhibited shorter response times to colored flowers compared to SWFs, but this behavior was mostly seen for SBFs or SYFs in females, and SRFs, SYFs, SPIFs, or SPFs in males. When provided an option to land on colored flowers and SWFs, female visitation occurred at high rates on SBFs, SRFs, SYFs, SPIFs, and SPFs; for males, this preference for colored flowers was seen to a lesser degree on SBF and SPIFs. Both sexes exhibited preference for colored flowers as sugar sources, but with different patterns: SPIFs, SRFs, SYFs, and SPFs for females; SYFs, SPFs, SPIFs and SRFs for males. Females preferentially rested on colored flowers when in competition with SWFs, but this preference was more pronounced for SPFs, SRFs, and SBFs. Males exhibited an increased preference for SRFs, SPFs, and SYFs as resting sites. Our results indicated the attraction of Ae. aegypti to rewarding artificial flowers, in some cases in ways similar to live flowering plants. The discovery that both male and female Ae. aegypti can feed on nectar mimics held by artificial flowers opens new avenues for improving sugar bait technology and for developing new attract-and-kill devices.

Scented Sugar Baits Enhance Detection of St. Louis Encephalitis and West Nile Viruses in Mosquitoes in Suburban California.

Scented sugar baits deployed in California deserts detected early West Nile virus (WNV) transmission by mosquitoes, representing a potential improvement to conventional arbovirus surveillance that relies heavily on infection rates in mosquito pools. In this study, we expanded deployment of scented sugar baits into suburban Sacramento and Yolo (2015, 2016) and Riverside Counties (2016), California. The goal of the study was to determine whether scented sugar baits detect WNV and St. Louis encephalitis virus (SLEV) concurrent with mosquito infections in trapped pools in areas of high human density. Between 8 and 10% of sugar baits were WNV RNA positive in both study years across the three counties. In Riverside County, where SLEV re-emerged in 2015, 1% of sugar baits were SLEV positive in 2016. Rates of sugar bait positives were at least 100 times higher than infection rates in trapped mosquitoes in the same districts. The prevalence of sugar bait positives varied temporally and did not coincide with infections in mosquitoes collected at the same sites each week. WNV RNA positive sugar baits were detected up to 2 wk before and after concurrent surveillance detected infection in mosquito pools at the same sites. Sugar baits also detected WNV in Riverside County at locations where no WNV activity was detected in mosquito pools. Sugar baits generated between 0.8 and 1.2 WNV positives per $1,000 and can be more economical than carbon dioxide baited traps that produce 0.8 positives per $1,000. These results indicate that the sugar bait approach enhances conventional arbovirus surveillance in mosquitoes in suburban California.

Development of a Novel Dry, Sticky Trap Design Incorporating Visual Cues for Drosophila suzukii (Diptera: Drosophilidae).

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is currently one of the most serious invasive pests for berry crops and cherries worldwide. The development of an effective monitoring trap that is reliable at detecting small populations to guide management decisions is greatly needed. To develop a novel dry trapping system, D. suzukii were trapped under field conditions in cherry orchards and raspberry high tunnels using various baited dry trap designs that were compared with the currently available deli-cup style traps that utilize a liquid bait or drowning solution. In a test in cherry orchards, red panel and combination yellow panel plus red sphere traps captured significantly more flies than yellow panel traps when all were baited with a Scentry lure. In a separate test in cherry, red sphere traps with the Scentry lure captured significantly more flies than the deli-cup traps with the Scentry lure or with the yeast sugar bait, and red panel traps with the Scentry lure captured significantly more flies than deli-cup traps with the Scentry lure. In raspberry high tunnels, red sphere traps with the Scentry lure captured significantly more flies than deli-cup traps with the Scentry lure. Red traps baited with the same lure as clear deli-cup traps consistently captured more D. suzukii, demonstrating that traps integrating a visual cue in combination with an olfactory cue are superior tools for monitoring D. suzukii. A dry trap requires less labor and maintenance than cup traps containing a liquid, improving the ease of use of D. suzukii monitoring traps.

Impact of Three Species of Aquatic Plants on Anopheles quadrimaculatus and its Effect on the Efficacy of Boric Acid Sugar Baits.

The purpose of this study was to investigate the sugar-feeding behavior of Anopheles quadrimaculatus by measuring the impact of different aquatic plants on its survival. At the same time, the potential use of boric acid in toxic sugar bait (TSB) applications to the leaves of these plants was also evaluated. Mean survival rates of mosquitoes after 120 h feeding on 3 common aquatic plant species-Thalia geniculata, Pontederia cordata, and Limnobium spongia-were 10.55%, 1.86%, and 6.21%, respectively. No significant difference in mortality between mosquitoes feeding on separate plant species was detected (P = 0.05). The TSB efficacy was evaluated by leaf dip bioassay to compare 24-h mortality of mosquitoes feeding on leaves treated with TSB formulation (1% boric acid, 10% sucrose) and leaves dipped in 10% sucrose. Mortality was significantly higher for TSB-treated leaves for T. geniculata (t = 12.5, df = 8, P < 0.0001) and P. cordata (t = 5.42, df = 8, P = 0.0006) than for L. spongia (t = 1.4003, df = 8, P = 0.199). One-way ANOVA analysis showed no significant difference in efficacy between TSB-treated leaves of the 3 plants.

Host plant forensics and olfactory-based detection in Afro-tropical mosquito disease vectors.

The global spread of vector-borne diseases remains a worrying public health threat, raising the need for development of new combat strategies for vector control. Knowledge of vector ecology can be exploited in this regard, including plant feeding; a critical resource that mosquitoes of both sexes rely on for survival and other metabolic processes. However, the identity of plant species mosquitoes feed on in nature remains largely unknown. By testing the hypothesis about selectivity in plant feeding, we employed a DNA-based approach targeting trnH-psbA and matK genes and identified host plants of field-collected Afro-tropical mosquito vectors of dengue, Rift Valley fever and malaria being among the most important mosquito-borne diseases in East Africa. These included three plant species for Aedes aegypti (dengue), two for both Aedes mcintoshi and Aedes ochraceus (Rift Valley fever) and five for Anopheles gambiae (malaria). Since plant feeding is mediated by olfactory cues, we further sought to identify specific odor signatures that may modulate host plant location. Using coupled gas chromatography (GC)-electroantennographic detection, GC/mass spectrometry and electroantennogram analyses, we identified a total of 21 antennally-active components variably detected by Ae. aegypti, Ae. mcintoshi and An. gambiae from their respective host plants. Whereas Ae. aegypti predominantly detected benzenoids, Ae. mcintoshi detected mainly aldehydes while An. gambiae detected sesquiterpenes and alkenes. Interestingly, the monoterpenes β-myrcene and (E)-β-ocimene were consistently detected by all the mosquito species and present in all the identified host plants, suggesting that they may serve as signature cues in plant location. This study highlights the utility of molecular approaches in identifying specific vector-plant associations, which can be exploited in maximizing control strategies such as such as attractive toxic sugar bait and odor-bait technology.

Longevity of Fly Baits Exposed to Field Conditions

Insecticidal fly baits are important tools for adult house fly, Musca domestica L. (Diptera: Muscidae), control, especially on animal operations. Two house fly baits, containing either cyantraniliprole or dinotefuran, were tested on a dairy farm for attractiveness over time compared to a sugar control. Sticky trap and bucket trap house fly catches were recorded for each bait type at 1 h, 3 h, 6 h, 12 h, 24 h, 48 h, 72 h, and 168 h. After 1 wk of exposure to flies and field conditions, these 'aged' baits were tested against fresh baits for fly visitation in the field over 1 h. House flies from each bait type (aged and fresh) were collected and kept under laboratory conditions to assess mortality over 3 d. Average visitation of individual flies to each bait type (fresh) in the field was also evaluated. Sticky traps did not show significant fly catch differences among bait types over time, however bucket trap catches did show significant differences for cyantraniliprole bait and dinotefuran bait compared to sugar at 72 h and 168 h. No significant differences among fly visitation to aged or fresh baits were found. Fresh cyantraniliprole bait and dinotefuran bait resulted in greater fly mortality compared to controls, but not compared to aged toxic baits. Average house fly visitation time was greatest for sugar and cyantraniliprole bait.

Attractive toxic sugar baits for controlling mosquitoes: a qualitative study in Bagamoyo, Tanzania

BackgroundMalaria elimination is unlikely to be achieved without the implementation of new vector control interventions capable of complementing insecticide-treated nets and indoor residual spraying. Attractive-toxic sugar baits (ATSBs) are considered a new vector control paradigm. They are technologically appropriate as they are simple and affordable to produce. ATSBs kill both female and male mosquitoes attracted to sugar feed on a sugary solution containing a mosquitocidal agent and may be used indoors or outdoors. This study explored the views and perceptions on ATSBs of community members from three Coastal Tanzanian communities.MethodsThree communities were chosen to represent coastal urban, peri-urban and rural areas. Sensitization meetings were held with a total of sixty community members where ATSBs were presented and explained their mode of action. At the end of the meeting, one ATSB was given to each participant for a period of 2 weeks, after which they were invited to participate in focus group discussions (FGDs) to provide feedback on their experience.ResultsOver 50% of the participants preferred to use the bait indoors although they had been instructed to place it outdoors. Participants who used the ATSBs indoors reported fewer mosquitoes inside their homes, but were disappointed not to find the dead mosquitoes in the baits, although they had been informed that this was unlikely to happen. Most participants disliked the appearance of the bait and some thought it to be reminiscent of witchcraft. Neighbours that did not participate in the FGDs or sensitizations were sceptical of the baits.ConclusionsThis study delivers insight on how communities in Coastal Tanzania are likely to perceive ATSBs and provides important information for future trials investigating the efficacy of ATSBs against malaria. This new vector control tool will require sensitization at community level regarding its mode of action in order to increase the acceptance and confidence in ATSBs for mosquito control given that most people are not familiar with the new paradigm. A few recommendations for product development and delivery are discussed.

Attacking the mosquito on multiple fronts: Insights from the Vector Control Optimization Model (VCOM) for malaria elimination.

BackgroundDespite great achievements by insecticide-treated nets (ITNs) and indoor residual spraying (IRS) in reducing malaria transmission, it is unlikely these tools will be sufficient to eliminate malaria transmission on their own in many settings today. Fortunately, field experiments indicate that there are many promising vector control interventions that can be used to complement ITNs and/or IRS by targeting a wide range of biological and environmental mosquito resources. The majority of these experiments were performed to test a single vector control intervention in isolation; however, there is growing evidence and consensus that effective vector control with the goal of malaria elimination will require a combination of interventions.Method and findingsWe have developed a model of mosquito population dynamic to describe the mosquito life and feeding cycles and to optimize the impact of vector control intervention combinations at suppressing mosquito populations. The model simulations were performed for the main three malaria vectors in sub-Saharan Africa, Anopheles gambiae s.s, An. arabiensis and An. funestus. We considered areas having low, moderate and high malaria transmission, corresponding to entomological inoculation rates of 10, 50 and 100 infective bites per person per year, respectively. In all settings, we considered baseline ITN coverage of 50% or 80% in addition to a range of other vector control tools to interrupt malaria transmission. The model was used to sweep through parameters space to select the best optimal intervention packages. Sample model simulations indicate that, starting with ITNs at a coverage of 50% (An. gambiae s.s. and An. funestus) or 80% (An. arabiensis) and adding interventions that do not require human participation (e.g. larviciding at 80% coverage, endectocide treated cattle at 50% coverage and attractive toxic sugar baits at 50% coverage) may be sufficient to suppress all the three species to an extent required to achieve local malaria elimination.ConclusionThe Vector Control Optimization Model (VCOM) is a computational tool to predict the impact of combined vector control interventions at the mosquito population level in a range of eco-epidemiological settings. The model predicts specific combinations of vector control tools to achieve local malaria elimination in a range of eco-epidemiological settings and can assist researchers and program decision-makers on the design of experimental or operational research to test vector control interventions. A corresponding graphical user interface is available for national malaria control programs and other end users.

The development of an ivermectin-based attractive toxic sugar bait (ATSB) to target Anopheles arabiensis

BackgroundAn increasing number of countries in sub-Saharan Africa are moving towards malaria-elimination, mostly thanks to successful vector control campaigns. However, elimination has proven challenging, resulting in the persistence of malaria transmission. It is now accepted that in order to eliminate malaria, new complementary vector control approaches must be developed. This study describes the development of a sugar-baited resting place containing a toxic dose of ivermectin for the control of Anopheles arabiensis.ResultsDose response experiments were performed in insectary conditions to determine the LD90 of ivermectin against An. arabiensis. Over 95% of An. arabiensis were knocked down 48 h post-sugar feeding on 10% sucrose solutions containing 0.01% ivermectin. When investigating different juices as attractants, it was observed that An. arabiensis preferred orange, watermelon and commercial guava juice over pawpaw, tomato, mango or banana, but were most likely to feed on simple 10% sugar solution. Using recycled materials, different bait prototypes were tested to determine the best design to maximize sugar feeding. Baits that offered a resting place for the mosquito rather than just a surface to sugar feed were more likely to attract An. arabiensis to sugar feed. The optimized prototype was then placed in different locations within a screen-house, colour-coded with different food dyes, containing competing vegetation (Ricinus communis) and experimental huts where humans slept under bed nets. Around half of all the released An. arabiensis sugar fed on the sugar baits, and approximately 50% of all sugar fed mosquitoes chose the baits close to outdoor vegetation before entering the huts.ConclusionsIvermectin is an effective insecticide for use in sugar baits. The design of the sugar bait can influence feeding rates and, therefore, efficacy. Sugar baits that offer a resting surface are more efficient and sugar feeding on the baits is maximized when these are placed close to peri-domestic vegetation. Attractive toxic sugar baited resting places may provide an additional vector control method to complement with existing strategies.