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

Hughes, Angela, Lissenden, Natalie ORCID: https://orcid.org/0000-0002-6578-5537, Viana, Mafalda, Toe, Kobie Hyacinthe and Ranson, Hilary ORCID: https://orcid.org/0000-0003-2332-8247 (2020) 'Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets.'. Parasites & Vectors, Vol 13, e17.

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Abstract

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.
Keywords: Mosquito, Anopheles, Insecticide resistance, Delayed mortality, Longevity, Sub-lethal effects, Long-lasting insecticidal nets (LLINs), Burkina Faso.

Item Type:	Article
Subjects:	QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes QX Parasitology > Insects. Other Parasites > QX 515 Anopheles WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases WA Public Health > Preventive Medicine > WA 240 Disinfection. Disinfestation. Pesticides (including diseases caused by) WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
Faculty: Department:	Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI):	https://doi.org/10.1186/s13071-019-3872-2
Depositing User:	Samantha Sheldrake
Date Deposited:	14 Jan 2020 09:32
Last Modified:	16 Jan 2020 13:48
URI:	https://archive.lstmed.ac.uk/id/eprint/13481

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