19
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Attrition, physical integrity and insecticidal activity of long-lasting insecticidal nets in sub-Saharan Africa and modelling of their impact on vectorial capacity

      research-article
      1 , 2 , 3 , 4 , 5 , 6 , 7 , 7 , 8 , 7 , 7 , 9 , 10 , 11 , 11 , 12 , 13 , 13 , 14 , 15 , 16 , 16 , 17 , 16 , 17 , 18 , 18 , 19 , 19 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 7 , 20 , 7 , 20 , 7 , 7 , 1 , 2 ,
      Malaria Journal
      BioMed Central
      Long-lasting insecticidal nets, Durability monitoring, Vectorial capacity, Malaria

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Background

          Long-lasting insecticidal nets (LLINs) are the primary malaria prevention and control intervention in many parts of sub-Saharan Africa. While LLINs are expected to last at least 3 years under normal use conditions, they can lose effectiveness because they fall out of use, are discarded, repurposed, physically damaged, or lose insecticidal activity. The contributions of these different interrelated factors to durability of nets and their protection against malaria have been unclear.

          Methods

          Starting in 2009, LLIN durability studies were conducted in seven countries in Africa over 5 years. WHO-recommended measures of attrition, LLIN use, insecticidal activity, and physical integrity were recorded for eight different net brands. These data were combined with analyses of experimental hut data on feeding inhibition and killing effects of LLINs on both susceptible and pyrethroid resistant malaria vectors to estimate the protection against malaria transmission—in terms of vectorial capacity (VC)—provided by each net cohort over time. Impact on VC was then compared in hypothetical scenarios where one durability outcome measure was set at the best possible level while keeping the others at the observed levels.

          Results

          There was more variability in decay of protection over time by country than by net brand for three measures of durability (ratios of variance components 4.6, 4.4, and 1.8 times for LLIN survival, use, and integrity, respectively). In some countries, LLIN attrition was slow, but use declined rapidly. Non-use of LLINs generally had more effect on LLIN impact on VC than did attrition, hole formation, or insecticide loss.

          Conclusions

          There is much more variation in LLIN durability among countries than among net brands. Low levels of use may have a larger impact on effectiveness than does variation in attrition or LLIN degradation. The estimated entomological effects of chemical decay are relatively small, with physical decay probably more important as a driver of attrition and non-use than as a direct cause of loss of effect. Efforts to maximize LLIN impact in operational settings should focus on increasing LLIN usage, including through improvements in LLIN physical integrity. Further research is needed to understand household decisions related to LLIN use, including the influence of net durability and the presence of other nets in the household.

          Related collections

          Most cited references25

          • Record: found
          • Abstract: found
          • Article: not found

          Expression of the cytochrome P450s, CYP6P3 and CYP6M2 are significantly elevated in multiple pyrethroid resistant populations of Anopheles gambiae s.s. from Southern Benin and Nigeria

          Background Insecticide resistance in Anopheles mosquitoes is threatening the success of malaria control programmes. This is particularly true in Benin where pyrethroid resistance has been linked to the failure of insecticide treated bed nets. The role of mutations in the insecticide target sites in conferring resistance has been clearly established. In this study, the contribution of other potential resistance mechanisms was investigated in Anopheles gambiae s.s. from a number of localities in Southern Benin and Nigeria. The mosquitoes were sampled from a variety of breeding sites in a preliminary attempt to investigate the role of contamination of mosquito breeding sites in selecting for resistance in adult mosquitoes. Results All mosquitoes sampled belonged to the M form of An. gambiae s.s. There were high levels of permethrin resistance in an agricultural area (Akron) and an urban area (Gbedjromede), low levels of resistance in mosquito samples from an oil contaminated site (Ojoo) and complete susceptibility in the rural Orogun location. The target site mutation kdrW was detected at high levels in two of the populations (Akron f = 0.86 and Gbedjromede f = 0.84) but was not detected in Ojoo or Orogun. Microarray analysis using the Anopheles gambiae detox chip identified two P450s, CYP6P3 and CYP6M2 up regulated in all three populations, the former was expressed at particularly high levels in the Akron (12.4-fold) and Ojoo (7.4-fold) populations compared to the susceptible population. Additional detoxification and redox genes were also over expressed in one or more populations including two cuticular pre-cursor genes which were elevated in two of the three resistant populations. Conclusion Multiple resistance mechanisms incurred in the different breeding sites contribute to resistance to permethrin in Benin. The cytochrome P450 genes, CYP6P3 and CYP6M2 are upregulated in all three resistant populations analysed. Several additional potential resistance mechanisms were also identified that warrant further investigation. Metabolic genes were over expressed irrespective of the presence of kdr, the latter resistance mechanism being absent in one resistant population. The discovery that mosquitoes collected from different types of breeding sites display differing profiles of metabolic genes at the adult stage may reflect the influence of a range of xenobiotics on selecting for resistance in mosquitoes.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: found
            Is Open Access

            Reported reasons for not using a mosquito net when one is available: a review of the published literature

            Background A review of the barriers to mosquito net use in malaria-endemic countries has yet to be presented in the published literature despite considerable research interest in this area. This paper partly addresses this gap by reviewing one component of the evidence base; namely, published research pertaining to self-reported reasons for not using a mosquito net among net 'owning' individuals. It was anticipated that the review findings would potentially inform an intervention or range of interventions best suited to promoting greater net use amongst this group. Method Studies were sought via a search of the Medline database. The key inclusion criteria were: that study participants could be identified as owning a mosquito net or having a mosquito net available for use; that these participants on one or more occasions were identified or self-reported as not using the mosquito net; and that reasons for not using the mosquito net were reported. Studies meeting these criteria were included irrespective of mosquito net type. Results A total of 22 studies met the inclusion criteria. Discomfort, primarily due to heat, and perceived (low) mosquito density were the most widely identified reason for non-use. Social factors, such as sleeping elsewhere, or not sleeping at all, were also reported across studies as were technical factors related to mosquito net use (i.e. not being able to hang a mosquito net or finding it inconvenient to hang) and the temporary unavailability of a normally available mosquito net (primarily due to someone else using it). However, confidence in the reported findings was substantially undermined by a range of methodological limitations and a dearth of dedicated research investigation. Conclusions The findings of this review should be considered highly tentative until such time as greater quantities of dedicated, well-designed and reported studies are available in the published literature. The current evidence-base is not sufficient in scope or quality to reliably inform mosquito net promoting interventions or campaigns targeted at individuals who own, but do not (reliably) use, mosquito nets.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              An experimental hut evaluation of PermaNet(®) 3.0, a deltamethrin-piperonyl butoxide combination net, against pyrethroid-resistant Anopheles gambiae and Culex quinquefasciatus mosquitoes in southern Benin.

              PermaNet 3.0 is a long-lasting combination net with deltamethrin present on the sides and a mixture of deltamethrin and piperonyl butoxide (PBO), an oxidase synergist, on the top panel. An experimental hut trial comparing unwashed and 20 times washed PermaNet 3.0 and PermaNet 2.0, Olyset Net and a conventional deltamethrin-treated net washed three times was conducted in southern Benin. Anopheles gambiae and Culex quinquefasciatus from this area are highly resistant to pyrethroids through kdr and cytochrome P450 mechanisms. The unwashed PermaNet 3.0 killed slightly more A. gambiae (52%) than the unwashed PermaNet 2.0 (44%) (P=0.036), indicating only partial synergism of resistance. After washing there was significant loss of activity to a similar level, with PermaNet 3.0 killing 31%, PermaNet 2.0 killing 29% and the conventional net killing 26%. Blood-feeding rates were partially inhibited for unwashed PermaNet 3.0 and Olyset Net (27% inhibition). Personal protection against A. gambiae derived from PermaNet 3.0 was similar to that from PermaNet 2.0 before washing (50% vs. 47%), and after 20 washes it decreased to 30%. Against C. quinquefasciatus, no treatment killed >24% entering the huts. The synergism from unwashed PermaNet 3.0 was lower than expected, probably due to an unidentified resistance mechanism unaffected by PBO. Copyright © 2010 Royal Society of Tropical Medicine and Hygiene. All rights reserved.
                Bookmark

                Author and article information

                Contributors
                Thomas-A.Smith@unibas.ch
                Journal
                Malar J
                Malar. J
                Malaria Journal
                BioMed Central (London )
                1475-2875
                28 August 2020
                28 August 2020
                2020
                : 19
                : 310
                Affiliations
                [1 ]GRID grid.416786.a, ISNI 0000 0004 0587 0574, Swiss Tropical and Public Health Institute, ; 4051 Basel, Switzerland
                [2 ]GRID grid.6612.3, ISNI 0000 0004 1937 0642, University of Basel, ; 4001 Basel, Switzerland
                [3 ]GRID grid.21107.35, ISNI 0000 0001 2171 9311, PMI VectorWorks, , JHU Center for Communication Programs, ; Baltimore, MD USA
                [4 ]Tropical Health LLP, Baltimore, MD USA
                [5 ]GRID grid.507606.2, U.S. President’s Malaria Initiative, U.S. Agency for International Development, ; Washington, DC USA
                [6 ]GRID grid.418309.7, ISNI 0000 0000 8990 8592, Present Address: Bill & Melinda Gates Foundation, ; Seattle, WA USA
                [7 ]GRID grid.416738.f, ISNI 0000 0001 2163 0069, Division of Parasitic Diseases and Malaria, , Centers for Disease Control (CDC) and Prevention, ; Atlanta, GA USA
                [8 ]PMI VectorWorks, Denver, CO USA
                [9 ]GRID grid.436176.1, National Malaria Control Program (NMCP), , Ministry of Health, ; Luanda, Angola
                [10 ]GRID grid.10772.33, ISNI 0000000121511713, Institute of Hygiene and Tropical Medicine, , NOVA University Lisbon, ; Lisbon, Portugal
                [11 ]GRID grid.473220.0, Centre de Recherche Entomologique de Cotonou (CREC), ; Cotonou, Bénin
                [12 ]Programme National de Lutte contre le Paludisme (PNLP), Ministry of Health, Cotonou, Bénin
                [13 ]GRID grid.33058.3d, ISNI 0000 0001 0155 5938, Kenya Medical Research Institute (KEMRI), ; Kisumu, Kenya
                [14 ]Present Address: PMI VectorLink Project, Abt Associates, Lusaka, Zambia
                [15 ]GRID grid.10595.38, ISNI 0000 0001 2113 2211, College of Medicine, , Malaria Alert Centre, ; P/Bag 360, Blantyre 3, Malawi
                [16 ]GRID grid.419229.5, Instituto Nacional de Saúde (INS), ; Ministério da Saúde, Maputo, Mozambique
                [17 ]GRID grid.415752.0, ISNI 0000 0004 0457 1249, National Malaria Control Programme (NMCP), , Ministry of Health, ; Maputo, Mozambique
                [18 ]GRID grid.8191.1, ISNI 0000 0001 2186 9619, Faculté des Sciences et Techniques (FST), , Université Cheikh Anta Diop (UCAD), ; Dakar, Senegal
                [19 ]National Malaria Control Centre (NMCC), Lusaka, Zambia
                [20 ]GRID grid.416738.f, ISNI 0000 0001 2163 0069, U.S. President’s Malaria Initiative, Division of Parasitic Diseases and Malaria, , Centers for Disease Control (CDC) and Prevention, ; Atlanta, GA USA
                Author information
                http://orcid.org/0000-0003-4218-447X
                Article
                3383
                10.1186/s12936-020-03383-6
                7456088
                32859210
                5646a57f-a49f-42c8-a470-8d888694ee9e
                © The Author(s) 2020

                Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

                History
                : 27 June 2020
                : 19 August 2020
                Funding
                Funded by: US President's Malaria Initiative
                Categories
                Research
                Custom metadata
                © The Author(s) 2020

                Infectious disease & Microbiology
                long-lasting insecticidal nets,durability monitoring,vectorial capacity,malaria

                Comments

                Comment on this article