Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets

Hughes, A., Lissenden, N., Viana, M. , Toé, K. H. and Ranson, H. (2020) Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets. Parasites and Vectors, 13(1), 17. (doi: 10.1186/s13071-019-3872-2) (PMID:31924276) (PMCID:PMC6954553)

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Background: The efficacy of long-lasting insecticidal nets (LLINs) in preventing malaria in Africa is threatened by insecticide resistance. Bioassays assessing 24-hour mortality post-LLIN exposure have established that resistance to the concentration of pyrethroids used in LLINs is widespread. However, although mosquitoes may no longer be rapidly killed by LLIN exposure, a delayed mortality effect has been shown to reduce the transmission potential of mosquitoes exposed to nets. This has been postulated to partially explain the continued efficacy of LLINs against pyrethroid-resistant populations. Burkina Faso is one of a number of countries with very high malaria burdens and pyrethroid-resistant vectors, where progress in controlling this disease has stagnated. We measured the impact of LLIN exposure on mosquito longevity in an area of the country with intense pyrethroid resistance to establish whether pyrethroid exposure was still shortening mosquito lifespan in this setting. Methods: We quantified the immediate and delayed mortality effects of LLIN exposure using standard laboratory WHO cone tests, tube bioassays and experimental hut trials on Anopheles gambiae populations originating from the Cascades region of Burkina Faso using survival analysis and a Bayesian state-space model. Results: Following single and multiple exposures to a PermaNet 2.0 LLIN only one of the four mosquito populations tested showed evidence of delayed mortality. No delayed mortality was seen in experimental hut studies using LLINs. A delayed mortality effect was only observed in WHO tube bioassays when deltamethrin concentration was increased above the standard diagnostic dose. Conclusions: As mosquito pyrethroid-resistance increases in intensity, delayed effects from LLIN exposure are substantially reduced or absent. Given the rapid increase in resistance occurring in malaria vectors across Africa it is important to determine whether the failure of LLINs to shorten mosquito lifespan is now a widespread phenomenon as this will have important implications for the future of this pivotal malaria control tool.

Item Type:Articles
Additional Information:NL and HR are funded by the Wellcome Trust under grant agreement number (200222/Z/15/Z) MiRA. MV is supported by a MRC Skills Development Fellowship (MR/ N015320/1) which is jointly funded by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement and is also part of the EDCTP2 programme
Glasgow Author(s) Enlighten ID:Viana, Dr Mafalda
Authors: Hughes, A., Lissenden, N., Viana, M., Toé, K. H., and Ranson, H.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Parasites and Vectors
ISSN (Online):1756-3305
Copyright Holders:Copyright © 2020 The Authors
First Published:First published in Parasites and Vectors 13(1):17
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172685Ecology of insecticide resistant vectors: consequences for the effectiveness of malaria control strategiesMafalda VianaMedical Research Council (MRC)MR/N015320/1Institute of Biodiversity, Animal Health and Comparative Medicine