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Mwaanga G, Ford J, Yukich J, Chanda B, Ashton RA, Chanda J, Munsanje B, Muntanga E, Mulota M, Simuyandi C, Mulala B, Simubali L, Saili K, Simulundu E, Miller J, Hamainza B, Orange E, Wagman J, Mburu MM, Harris AF, Entwistle J, Littrell M. Residual bioefficacy of attractive targeted sugar bait stations targeting malaria vectors during seasonal deployment in Western Province of Zambia. Malar J 2024; 23:169. [PMID: 38811947 PMCID: PMC11138038 DOI: 10.1186/s12936-024-04990-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 05/18/2024] [Indexed: 05/31/2024] Open
Abstract
BACKGROUND The primary vector control interventions in Zambia are long-lasting insecticidal nets and indoor residual spraying. Challenges with these interventions include insecticide resistance and the outdoor biting and resting behaviours of many Anopheles mosquitoes. Therefore, new vector control tools targeting additional mosquito behaviours are needed to interrupt transmission. Attractive targeted sugar bait (ATSB) stations, which exploit the sugar feeding behaviours of mosquitoes, may help in this role. This study evaluated the residual laboratory bioefficacy of Westham prototype ATSB® Sarabi v.1.2.1 Bait Station (Westham Ltd., Hod-Hasharon, Israel) in killing malaria vectors in Western Province, Zambia, during the first year of a large cluster randomized phase-III trial (Clinical Trials.gov Identifier: NCT04800055). METHODS This was a repeat cross-sectional study conducted within three districts, Nkeyema, Kaoma, and Luampa, in Western Province, Zambia. The study was conducted in 12 intervention clusters among the 70 trial clusters (35 interventions, 35 controls) between December 2021 and June 2022. Twelve undamaged bait stations installed on the outer walls of households were collected monthly (one per cluster per month) for bioassays utilizing adult female and male Anopheles gambiae sensu stricto (Kisumu strain) mosquitoes from a laboratory colony. RESULTS A total of 84 field-deployed ATSB stations were collected, and 71 ultimately met the study inclusion criteria for remaining in good condition. Field-deployed stations that remained in good condition (intact, non-depleted of bait, and free of dirt as well as mold) retained high levels of bioefficacy (mean induced mortality of 95.3% in males, 71.3% in females, 83.9% combined total) over seven months in the field but did induce lower mortality rates than non-deployed ATSB stations (mean induced mortality of 96.4% in males, 87.0% in females, 91.4% combined total). There was relatively little variation in corrected mortality rates between monthly rounds for those ATSB stations that had been deployed to the field. CONCLUSION While field-deployed ATSB stations induced lower mortality rates than non-deployed ATSB stations, these stations nonetheless retained relatively high and stable levels of bioefficacy across the 7-month malaria transmission season. While overall mean mosquito mortality rates exceeded 80%, mean mortality rates for females were 24 percentage points lower than among males and these differences merit attention and further evaluation in future studies. The duration of deployment was not associated with lower bioefficacy. Westham prototype ATSB stations can still retain bioefficacy even after deployment in the field for 7 months, provided they do not meet predetermined criteria for replacement.
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Affiliation(s)
| | - Jacob Ford
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA
| | - Joshua Yukich
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA
| | | | - Ruth A Ashton
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA
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Lukenge M, Ignell R, Hill SR. Adenosine triphosphate overrides the aversive effect of antifeedants and toxicants: a model alternative phagostimulant for sugar-based vector control tools. Parasit Vectors 2023; 16:416. [PMID: 37964326 PMCID: PMC10647091 DOI: 10.1186/s13071-023-06039-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 10/30/2023] [Indexed: 11/16/2023] Open
Abstract
BACKGROUND Sugar, when used as the phagostimulant in attractive toxic bait control tools, limits the efficacy and selectivity of this technology. Thus, more potent and selective phagostimulants than sugar are required to improve this technology. The potency of adenosine triphosphate (ATP) as an alternative model phagostimulant was assessed to determine its capacity to override the aversive effects of select antifeedants and toxicants. How ATP and sucrose modulate the rate of toxicity in the yellow fever mosquito Aedes aegypti was also examined. METHODS A no-choice feeding assay was used to investigate the phagostimulatory ability of ATP to override the aversive effects of structurally divergent antifeedant and toxicant compounds, and to modulate the rate of toxicity over 24 h. Binary combinations of antifeedant and toxicant compounds, at various concentrations, were similarly assessed for enhanced lethal potency. In comparison, no-choice open access and cotton wick feeding assays were used to determine the phagostimulatory role of sucrose in the ingestion of boric acid-laced diets. Dissections of the guts were performed to determine the diet destination as dependant on the phagostimulant. RESULTS ATP is a potent phagostimulant that dose dependently overrides aversion to antifeedant and toxicant tastants. Feeding on antifeedant- or toxicant-laced diets that was induced by ATP selectively resulted in rapid knockdown (nicotine, lobeline and caffeine) or death (boric acid and propylene glycol), with a combination of the two lethal compounds inducing a synergistic effect at lower concentrations. ATP- and sucrose-induced feeding predominantly directed the antifeedant- or toxicant-laced meals to the midgut and the crop, respectively. CONCLUSIONS ATP is an efficacious alternative model phagostimulant to sucrose that overrides the aversive effects of antifeedants and toxicants, resulting in rapid toxic effects. Furthermore, this study demonstrates that variation in the rate of toxicity between ATP- and sugar-induced feeding is at least partly regulated by the differential feeding response, volume imbibed and the destination of the meals. Additional research is needed to identify structurally related, stable analogues of ATP due to the ephemeral nature of this molecule. For future applications, the workflow presented in this study may be used to evaluate such analogues for their suitability for use in attractive bait stations designed to target a broad range of haematophagous arthropods and prevent off-target species' feeding.
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Affiliation(s)
- Matthew Lukenge
- Disease Vector Group, Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Rickard Ignell
- Disease Vector Group, Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Sharon Rose Hill
- Disease Vector Group, Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden.
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Chanda J, Wagman J, Chanda B, Kaniki T, Ng’andu M, Muyabe R, Mwenya M, Sakala J, Miller J, Mwaanga G, Simubali L, Mburu MM, Simulundu E, Mungo A, Fraser K, Mwandigha L, Ashton R, Yukich J, Harris AF, Burkot TR, Orange E, Littrell M, Entwistle J. Feeding rates of malaria vectors from a prototype attractive sugar bait station in Western Province, Zambia: results of an entomological validation study. Malar J 2023; 22:70. [PMID: 36855105 PMCID: PMC9974387 DOI: 10.1186/s12936-023-04491-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 02/13/2023] [Indexed: 03/02/2023] Open
Abstract
BACKGROUND Attractive targeted sugar bait (ATSB) stations are a promising new approach to malaria vector control that could compliment current tools by exploiting the natural sugar feeding behaviors of mosquitoes. Recent proof of concept work with a prototype ATSB® Sarabi Bait Station (Westham Co., Hod-Hasharon, Israel) has demonstrated high feeding rates and significant reductions in vector density, human biting rate, and overall entomological inoculation rate for Anopheles gambiae sensu lato (s.l.) in the tropical savannah of western Mali. The study reported here was conducted in the more temperate, rainier region of Western Province, Zambia and was designed to confirm the primary vector species in region and to estimate corresponding rates of feeding from prototype attractive sugar bait (ASB) Sarabi Bait Stations. METHODS The product evaluated was the Sarabi v1.1.1 ASB station, which did not include insecticide but did include 0.8% uranine as a dye allowing for the detection, using UV fluorescence light microscopy, of mosquitoes that have acquired a sugar meal from the ASB. A two-phase, crossover study design was conducted in 10 village-based clusters in Western Province, Zambia. One study arm initially received 2 ASB stations per eligible structure while the other initially received 3. Primary mosquito sampling occurred via indoor and outdoor CDC Miniature UV Light Trap collection from March 01 through April 09, 2021 (Phase 1) and from April 19 to May 28, 2021 (Phase 2). RESULTS The dominant vector in the study area is Anopheles funestus s.l., which was the most abundant species group collected (31% of all Anophelines; 45,038/144,5550), had the highest sporozoite rate (3.16%; 66 positives out of 2,090 tested), and accounted for 94.3% (66/70) of all sporozoite positive specimens. Of those An. funestus specimens further identified to species, 97.2% (2,090/2,150) were An. funestus sensu stricto (s.s.). Anopheles gambiae s.l. (96.8% of which were Anopheles arabiensis) is a likely secondary vector and Anopheles squamosus may play a minor role in transmission. Overall, 21.6% (9,218/42,587) of An. funestus specimens and 10.4% (201/1,940) of An. gambiae specimens collected were positive for uranine, translating into an estimated daily feeding rate of 8.9% [7.7-9.9%] for An. funestus (inter-cluster range of 5.5% to 12.7%) and 3.9% [3.3-4.7%] for An. gambiae (inter-cluster range of 1.0-5.2%). Feeding rates were no different among mosquitoes collected indoors or outdoors, or among mosquitoes from clusters with 2 or 3 ASBs per eligible structure. Similarly, there were no correlations observed between feeding rates and the average number of ASB stations per hectare or with weekly rainfall amounts. CONCLUSIONS Anopheles funestus and An. gambiae vector populations in Western Province, Zambia readily fed from the prototype Sarabi v1.1.1 ASB sugar bait station. Observed feeding rates are in line with those thought to be required for ATSB stations to achieve reductions in malaria transmission when used in combination with conventional control methods (IRS or LLIN). These results supported the decision to implement a large-scale, epidemiological cluster randomized controlled trial of ATSB in Zambia, deploying 2 ATSB stations per eligible structure.
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Affiliation(s)
| | | | | | | | | | | | | | - Jimmy Sakala
- PATH, Lusaka, Zambia ,Present Address: Jhpeigo, Lusaka, Zambia
| | | | | | | | | | | | | | - Keith Fraser
- grid.7445.20000 0001 2113 8111Imperial College London, London, UK
| | - Lazaro Mwandigha
- grid.7445.20000 0001 2113 8111Imperial College London, London, UK ,grid.4991.50000 0004 1936 8948Present Address: University of Oxford, Oxford, UK
| | - Ruth Ashton
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, USA
| | - Joshua Yukich
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, USA
| | | | - Thomas R. Burkot
- grid.1011.10000 0004 0474 1797Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Erica Orange
- grid.415269.d0000 0000 8940 7771PATH, Seattle, USA
| | - Megan Littrell
- grid.416809.20000 0004 0423 0663PATH, Washington, DC USA
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