Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons

Masalu, J. P., Finda, M., Killeen, G. F., Ngowo, H. S. , Pinda, P. G. and Okumu, F. O. (2020) Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons. Malaria Journal, 19, 109. (doi: 10.1186/s12936-020-03180-1) (PMID:32156280) (PMCID:PMC7063784)

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Background: Residents of malaria-endemic communities spend several hours outdoors performing different activities, e.g. cooking, story-telling or eating, thereby exposing themselves to potentially-infectious mosquitoes. This compromises effectiveness of indoor interventions, notably long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacy against mosquitoes of hessian fabric mats and ribbons treated with the spatial repellent, transfluthrin, and fitted to chairs and outdoor kitchens, respectively. Methods: Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of locally-made transfluthrin-emanating chairs and hessian ribbons were tested in outdoor environments of 28 households in dry and wet seasons, using volunteer-occupied exposure-free double net traps. CDC light traps were used to estimate host-seeking mosquito densities within open-structure outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24 h-mortality. Finally, The World Health Organization insecticide susceptibility tests were conducted on wild-caught Anopheles from the villages. Results: Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Two-thirds of these spaces were sited under trees, and only one third (34.4%) were built-up. The outdoor structures were usually makeshift kitchens having roofs and partial walls. Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70–85%, while transfluthrin-treated hessian ribbons fitted to the outdoor kitchens caused 77–81% reduction in the general peri-domestic area. Almost all the field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. The An. arabiensis were susceptible to non-pyrethroids (pirimiphos methyl and bendiocarb), but resistant to pyrethroids commonly used on LLINs (deltamethrin and permethrin). Conclusion: Most houses had actively-used peri-domestic outdoor spaces where exposure to mosquitoes occurred. The transfluthrin-treated chairs and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant field-caught malaria vectors. These two new prototype formats for transfluthrin emanators, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.

Item Type:Articles
Additional Information:The study was funded by Biotechnology and Biological Sciences Research Council (BBSRC) through Building Out Vector-borne diseases in sub-Saharan Africa: the BOVA Network (Grant number: BOVA007). FOO was also funded by Wellcome Trust Intermediate Fellowship in Public Health and Tropical Medicine (Grant number: WT102350/Z/13/Z) and the Howard Hughes Medical Institute (HHMI)-Gates International Scholarship (Grant number: OPP1099295).
Glasgow Author(s) Enlighten ID:Ngowo, Halfan and Okumu, Professor Fredros
Authors: Masalu, J. P., Finda, M., Killeen, G. F., Ngowo, H. S., Pinda, P. G., 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 © 2020 The Authors
First Published:First published in Malaria Journal 19: 109
Publisher Policy:Reproduced under a Creative Commons License

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