title: Delayed mortality effects cut the malaria transmission potential of insecticide-resistant mosquitoes.
abstract: Malaria transmission has been substantially reduced across Africa through the distribution of long-lasting insecticidal nets (LLINs). However, the emergence of insecticide resistance within mosquito vectors risks jeopardizing the future efficacy of this control strategy. The severity of this threat is uncertain because the consequences of resistance for mosquito fitness are poorly understood: while resistant mosquitoes are no longer immediately killed upon contact with LLINs, their transmission potential may be curtailed because of longer-term fitness costs that persist beyond the first 24 h after exposure. Here, we used a Bayesian state-space model to quantify the immediate (within 24 h of exposure) and delayed (>24 h after exposure) impact of insecticides on daily survival and malaria transmission potential of moderately and highly resistant laboratory populations of the major African malaria vector Anopheles gambiae Contact with LLINs reduced the immediate survival of moderately and highly resistant An. gambiae strains by 60-100% and 3-61%, respectively, and delayed mortality impacts occurring beyond the first 24 h after exposure further reduced their overall life spans by nearly one-half. In total, insecticide exposure was predicted to reduce the lifetime malaria transmission potential of insecticide-resistant vectors by two-thirds, with delayed effects accounting for at least one-half of this reduction. The existence of substantial, previously unreported, delayed mortality effects within highly resistant malaria vectors following exposure to insecticides does not diminish the threat of growing resistance, but posits an explanation for the apparent paradox of continued LLIN effectiveness in the presence of high insecticide resistance.
authors.affiliation: Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom;
authors.forename: Mafalda
authors.initials: M
authors.lastname: Viana
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom.
authors.forename: Angela
authors.initials: A
authors.lastname: Hughes
authors.affiliation: Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom;
authors.forename: Jason
authors.initials: J
authors.lastname: Matthiopoulos
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom hilary.ranson@lstmed.ac.uk.
authors.forename: Hilary
authors.initials: H
authors.lastname: Ranson
authors.affiliation: Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom;
authors.forename: Heather M
authors.initials: HM
authors.lastname: Ferguson
mesh_terms: D000818:Animals; D000852:Anopheles / Q000502:physiology*; D001499:Bayes Theorem; D006801:Humans; D007305:Insecticide Resistance; D057148:Insecticide-Treated Bednets; D008288:Malaria / Q000517:prevention & control* / Q000635:transmission; D009032:Mosquito Control
keywords: Anopheles gambiae; insecticide resistance; long-lasting insecticidal nets; state-space models; transmission potential