Effects of vegetation densities on the performance of attractive targeted sugar baits (ATSBs) for malaria vector control: a semi-field study

• Published in: Malaria Journal
• Main Authors: Letus L. Muyaga, Felician C. Meza, Najat F. Kahamba, Rukiyah M. Njalambaha, Betwel J. Msugupakulya, Emmanuel W. Kaindoa, Halfan S. Ngowo, Fredros O. Okumu
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2023
• Subjects: Anopheles arabiensis; Attractive targeted sugar baits; ATSBs; Vegetation densities; Ifakara Health Institute; Outdoor biting; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-023-04625-z; https://doaj.org/article/1979efd8fe3347cba26bbc2719287755

Abstract Background Attractive targeted sugar baits (ATSBs) control sugar-feeding mosquitoes with oral toxicants, and may effectively complement core malaria interventions, such as insecticide-treated nets even where pyrethroid-resistance is widespread. The technology is particularly efficacious in arid and semi-arid areas. However, their performance remains poorly-understood in tropical areas with year-round malaria transmission, and where the abundant vegetation constitutes competitive sugar sources for mosquitoes. This study compared the efficacies of ATSBs (active ingredient: 2% boric acid) in controlled settings with different vegetation densities. Methods Potted mosquito-friendly plants were introduced inside semi-field chambers (9.6 m by 9.6 m) to simulate densely-vegetated, sparsely-vegetated, and bare sites without any vegetation (two chambers/category). All chambers had volunteer-occupied huts. Laboratory-reared Anopheles arabiensis were released nightly (200/chamber) and host-seeking females recaptured using human landing catches outdoors (8.00 p.m.–9.00 p.m.) and CDC-light traps indoors (9.00 p.m.–6.00 a.m.). Additionally, resting mosquitoes were collected indoors and outdoors each morning using Prokopack aspirators. The experiments included a “before-and-after” set-up (with pre-ATSBs, ATSBs and post-ATSBs phases per chamber), and a “treatment vs. control” set-up (where similar chambers had ATSBs or no ATSBs). The experiments lasted 84 trap-nights. Results In the initial tests when all chambers had no vegetation, the ATSBs reduced outdoor-biting by 69.7%, indoor-biting by 79.8% and resting mosquitoes by 92.8%. In tests evaluating impact of vegetation, the efficacy of ATSBs against host-seeking mosquitoes was high in bare chambers (outdoors: 64.1% reduction; indoors: 46.8%) but modest or low in sparsely-vegetated (outdoors: 34.5%; indoors: 26.2%) and densely-vegetated chambers (outdoors: 25.4%; indoors: 16.1%). Against resting mosquitoes, the ATSBs performed modestly across settings (non-vegetated ...