Evaluation of a push–pull system consisting of transfluthrin-treated eave ribbons and odour-baited traps for control of indoor- and outdoor-biting malaria vectors

Mmbando, A. S. et al. (2019) Evaluation of a push–pull system consisting of transfluthrin-treated eave ribbons and odour-baited traps for control of indoor- and outdoor-biting malaria vectors. Malaria Journal, 18, 87. (doi: 10.1186/s12936-019-2714-1) (PMID:30894185) (PMCID:PMC6427877)

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Background: Push–pull strategies have been proposed as options to complement primary malaria prevention tools, indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLINs), by targeting particularly early-night biting and outdoor-biting mosquitoes. This study evaluated different configurations of a push–pull system consisting of spatial repellents [transfluthrin-treated eave ribbons (0.25 g/m2 ai)] and odour-baited traps (CO2-baited BG-Malaria traps), against indoor-biting and outdoor-biting malaria vectors inside large semi-field systems. Methods: Two experimental huts were used to evaluate protective efficacy of the spatial repellents (push-only), traps (pull-only) or their combinations (push–pull), relative to controls. Adult volunteers sat outdoors (1830 h–2200 h) catching mosquitoes attempting to bite them (outdoor-biting risk), and then went indoors (2200 h–0630 h) to sleep under bed nets beside which CDC-light traps caught host-seeking mosquitoes (indoor-biting risk). Number of traps and their distance from huts were varied to optimize protection, and 500 laboratory-reared Anopheles arabiensis released nightly inside the semi-field chambers over 122 experimentation nights. Results: Push-pull offered higher protection than traps alone against indoor-biting (83.4% vs. 35.0%) and outdoor-biting (79% vs. 31%), but its advantage over repellents alone was non-existent against indoor-biting (83.4% vs. 81%) and modest for outdoor-biting (79% vs. 63%). Using two traps (1 per hut) offered higher protection than either one trap (0.5 per hut) or four traps (2 per hut). Compared to original distance (5 m from huts), efficacy of push–pull against indoor-biting peaked when traps were 15 m away, while efficacy against outdoor-biting peaked when traps were 30 m away. Conclusion: The best configuration of push–pull comprised transfluthrin-treated eave ribbons plus two traps, each at least 15 m from huts. Efficacy of push–pull was mainly due to the spatial repellent component. Adding odour-baited traps slightly improved personal protection indoors, but excessive trap densities increased exposure near users outdoors. Given the marginal efficacy gains over spatial repellents alone and complexity of push–pull, it may be prudent to promote just spatial repellents alongside existing interventions, e.g. LLINs or non-pyrethroid IRS. However, since both transfluthrin and traps also kill mosquitoes, and because transfluthrin can inhibit blood-feeding, field studies should be done to assess potential community-level benefits that push–pull or its components may offer to users and non-users.

Item Type:Articles
Additional Information:ASM was funded by Wellcome Trust Masters Fellowship in Public Health and the Association of Physicians of Great Britain and Ireland which fund this research (Grant Number 106356/Z/14/Z). EPAB was funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) (Grant 88881.133584/2016-01) and AEE funded by the Conselho Nacional de Desenvolvimento Científico e Tecnológico of the Ministério da Ciência, Tecnologia e Inovação (CNPq/MCTI) (Grant 310205/2014-0) and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) (Grant PPM-00502-15). FOO was also supported by a Wellcome Trust Intermediate Research Fellowship (Grant Number: WT102350/Z/13/Z), a Howard Hughes Medical Institute (HHMI)—Gates International Research Scholarship (Grant No. OPP1175877) and a Bill & Melinda Gates Foundation Grant (Grant No. OPP1177156).
Glasgow Author(s) Enlighten ID:Ngowo, Halfan and Okumu, Dr Fredros
Authors: Mmbando, A. S., Batista, E. P. A., Kilalangongono, M., Finda, M. F., Mwanga, E. P., Kaindoa, E. W., Kifungo, K., Njalambaha, R. M., Ngowo, H. S., Eiras, A. E., and Okumu, F. O.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Malaria Journal
Publisher:BioMed Central
ISSN (Online):1475-2875
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Malaria Journal 18: 87
Publisher Policy:Reproduced under a Creative Commons License

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