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Okiring J, Gonahasa S, Maiteki-Sebuguzi C, Katureebe A, Bagala I, Mutungi P, Kigozi SP, Namuganga JF, Nankabirwa JI, Kamya MR, Donnelly MJ, Churcher TS, Staedke SG, Sherrard-Smith E. LLIN Evaluation in Uganda Project (LLINEUP): modelling the impact of COVID-19-related disruptions on delivery of long-lasting insecticidal nets on malaria indicators in Uganda. Malar J 2024; 23:180. [PMID: 38844987 PMCID: PMC11157881 DOI: 10.1186/s12936-024-05008-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 06/04/2024] [Indexed: 06/09/2024] Open
Abstract
BACKGROUND Disruptions in malaria control due to COVID-19 mitigation measures were predicted to increase malaria morbidity and mortality in Africa substantially. In Uganda, long-lasting insecticidal nets (LLINs) are distributed nationwide every 3-4 years, but the 2020-2021 campaign was altered because of COVID-19 restrictions so that the timing of delivery of new nets was different from the original plans made by the National Malaria Control Programme. METHODS A transmission dynamics modelling exercise was conducted to explore how the altered delivery of LLINs in 2020-2021 impacted malaria burden in Uganda. Data were available on the planned LLIN distribution schedule for 2020-2021, and the actual delivery. The transmission model was used to simulate 100 health sub-districts, and parameterized to match understanding of local mosquito bionomics, net use estimates, and seasonal patterns based on data collected in 2017-2019 during a cluster-randomized trial (LLINEUP). Two scenarios were compared; simulated LLIN distributions matching the actual delivery schedule, and a comparable scenario simulating LLIN distributions as originally planned. Model parameters were otherwise matched between simulations. RESULTS Approximately 70% of the study population received LLINs later than scheduled in 2020-2021, although some areas received LLINs earlier than planned. The model indicates that malaria incidence in 2020 was substantially higher in areas that received LLINs late. In some areas, early distribution of LLINs appeared less effective than the original distribution schedule, possibly due to attrition of LLINs prior to transmission peaks, and waning LLIN efficacy after distribution. On average, the model simulations predicted broadly similar overall mean malaria incidence in 2021 and 2022. After accounting for differences in cluster population size and LLIN distribution dates, no substantial increase in malaria burden was detected. CONCLUSIONS The model results suggest that the disruptions in the 2020-2021 LLIN distribution campaign in Uganda did not substantially increase malaria burden in the study areas.
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Affiliation(s)
- Jaffer Okiring
- Clinical Epidemiology Unit, Makerere University College of Health Sciences, PO Box 7475, Kampala, Uganda.
- Infectious Diseases Research Collaboration, Kampala, Uganda.
| | | | | | | | - Irene Bagala
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Peter Mutungi
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Simon P Kigozi
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | | | - Joaniter I Nankabirwa
- Clinical Epidemiology Unit, Makerere University College of Health Sciences, PO Box 7475, Kampala, Uganda
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Moses R Kamya
- Infectious Diseases Research Collaboration, Kampala, Uganda
- Department of Medicine, Makerere University, Kampala, Uganda
| | - Martin J Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
- Wellcome Sanger Institute, Hinxton, UK
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Sarah G Staedke
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
- Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
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Shannon J, Kagone M, Candrinho B, Otikwu S, Ingabire C, Gansane A, Pooda S, Aboubacar F, Ouattara F, Savaio B, Joanguete C, Sixpence L, Koenker H, Uhomoibhi P, Okoko OO, Ali O, Babarinde D, Ogundairo J, Lemah AS, Mbituyumuremyi A, Singirankabo JH, Kawakyu N, Guglielmo F, Fornadel C, Arnett K, Wagman J, Gogue C, Tynuv K, Digre P, Mwesigwa J, Robertson M. A qualitative look at bed net access and use in Burkina Faso, Mozambique, Nigeria, and Rwanda following piloted distributions of dual-active ingredient insecticide-treated nets. Malar J 2024; 23:137. [PMID: 38715035 PMCID: PMC11077758 DOI: 10.1186/s12936-024-04868-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 01/30/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND Universal coverage with insecticide-treated nets (ITNs) is important for malaria control and elimination. The emergence and intensification of insecticide resistance threatens progress made through the deployment of these interventions and has required the development of newer, more expensive ITN types. Understanding malaria prevention behaviour, including barriers and facilitators to net access and use, can support effective decision-making for the promotion and distribution of ITNs. METHODS In-depth interviews and focus group discussions were conducted in 3 to 4 villages per district, in 13 districts across Burkina Faso, Mozambique, Nigeria and Rwanda from 2019 to 2022. Interviews were conducted in the local language, translated and transcribed in English, French or Portuguese. Transcripts were coded and analysed using Nvivo and ATLAS.ti. RESULTS ITNs were obtained from mass distribution campaigns, antenatal care and immunization visits, and purchased on the private market in some locations. While there were divergent perspectives in whether the number of distributed nets were adequate, participants consistently expressed concerns of bias, discrimination, and a lack of transparency with the distribution process. ITNs were frequently used alongside other malaria prevention methods. The primary motivation for use was malaria prevention. While some participants reported using nets nightly throughout the year, other participants reported seasonal use, both due to the perceived higher density of mosquitoes and discomfort of sleeping under a net in the increased heat. Other barriers to consistent net use included activities that take place away from the home, sleeping patterns and arrangements, and sensitivity to the insecticides on the nets. CONCLUSIONS ITNs remain an important malaria control intervention. To ensure adequate and increased net access, distribution campaigns should consider family structures, available sleeping spaces, and other bed sharing preferences when identifying the number of nets needed for distribution. In addition, campaigns should allow for multiple options for net distribution points and timing to accommodate households remote to health services. Continuous distribution channels and complimentary distribution through the private sector could help fill gaps in coverage. Solutions are needed for outdoor malaria transmission, including alternative designs for ITNs, and improving access to complementary personal protective measures.
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Affiliation(s)
| | - Moubassira Kagone
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Baltazar Candrinho
- National Malaria Control Programme, Ministry of Health, Maputo, Mozambique
| | | | | | - Adama Gansane
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Samy Pooda
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Fofana Aboubacar
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Fatou Ouattara
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | | | | | | | | | - Perpetua Uhomoibhi
- National Malaria Elimination Programme, Federal Ministry of Health, Abuja, Nigeria
| | - Okefu Oyale Okoko
- National Malaria Elimination Programme, Federal Ministry of Health, Abuja, Nigeria
| | - Onoja Ali
- Ibolda Health International, Abuja, Nigeria
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Oruni A, Lynd A, Njoroge H, Onyige I, van’t Hof AE, Matovu E, Donnelly MJ. Pyrethroid resistance and gene expression profile of a new resistant An. gambiae colony from Uganda reveals multiple resistance mechanisms and overexpression of Glutathione-S-Transferases linked to survival of PBO-pyrethroid combination. Wellcome Open Res 2024; 9:13. [PMID: 38813466 PMCID: PMC11134160 DOI: 10.12688/wellcomeopenres.19404.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2024] [Indexed: 05/31/2024] Open
Abstract
Background The effectiveness of long-lasting insecticidal nets (LLINs) are being threatened by growing resistance to pyrethroids. To restore their efficacy, a synergist, piperonyl butoxide (PBO) which inhibits cytochrome P450s has been incorporated into pyrethroid treated nets. A trial of PBO-LLINs was conducted in Uganda from 2017 and we attempted to characterize mechanisms of resistance that could impact intervention efficacy. Methods We established an Anopheles gambiae s.s colony in 2018 using female mosquitoes collected from Busia district in eastern Uganda. We first assessed the phenotypic resistance profile of this colony using WHO tube and net assays using a deltamethrin dose-response approach. The Busia colony was screened for known resistance markers and RT-qPCR targeting 15 genes previously associated with insecticide resistance was performed. Results The Busia colony had very high resistance to deltamethrin, permethrin and DDT. In addition, the colony had moderate resistance to alpha-cypermethrin and lambda-cyhalothrin but were fully susceptible to bendiocarb and fenitrothion. Exposure to PBO in combination with permethrin and deltamethrin resulted in higher mortality rates in both net and tube assays, with a higher mortality observed in net assays than tube assays. The kdr marker, Vgsc-995S was at very high frequency (91.7-98.9%) whilst the metabolic markers Coeae1d and Cyp4j5-L43F were at very low (1.3% - 11.5%) and moderate (39.5% - 44.7%) frequencies respectively. Our analysis showed that gene expression pattern in mosquitoes exposed to deltamethrin, permethrin or DDT only were similar in comparison to the susceptible strain and there was significant overexpression of cytochrome P450s, glutathione-s-transferases (GSTs) and carboxyl esterases (COEs). However, mosquitoes exposed to both PBO and pyrethroid strikingly and significantly only overexpressed closely related GSTs compared to unexposed mosquitoes while major cytochrome P450s were underexpressed. Conclusions The high levels of pyrethroid resistance observed in Busia appears associated with a wide range of metabolic gene families.
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Affiliation(s)
- Ambrose Oruni
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, L3 5QA, UK
- College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, Kampala, Central Region, Uganda
| | - Amy Lynd
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, L3 5QA, UK
| | - Harun Njoroge
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, L3 5QA, UK
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), Kisumu, Kenya
| | - Ismail Onyige
- Infectious Diseases Research Collaboration, Kampala, Central Region, Uganda
| | - Arjen E. van’t Hof
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, L3 5QA, UK
| | - Enock Matovu
- College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, Kampala, Central Region, Uganda
| | - Martin J. Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, L3 5QA, UK
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Joseph RN, Mwema T, Eiseb SJ, Maliti DV, Tambo M, Iitula I, Eloff L, Lukubwe O, Smith-Gueye C, Vajda ÉA, Tatarsky A, Katokele ST, Uusiku PN, Walusimbi D, Ogoma SB, Mumbengegwi DR, Lobo NF. Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia. Malar J 2024; 23:77. [PMID: 38486288 PMCID: PMC10941414 DOI: 10.1186/s12936-024-04898-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 03/02/2024] [Indexed: 03/17/2024] Open
Abstract
BACKGROUND Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To address this challenge, the World Health Organization (WHO) recommends the use of piperonyl butoxide (PBO) LLINs in areas where pyrethroid resistance is confirmed to be mediated by mixed function oxidase (MFO). METHODS This study assessed the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to WHO tube bioassays with 4% DDT and 0.05% deltamethrin insecticides. Additionally, the study explored the effect of piperonyl butoxide (PBO) synergist by sequentially exposing mosquitoes to deltamethrin (0.05%) alone, PBO (4%) + deltamethrin (0.05%), and PBO alone. The Anopheles mosquitoes were further identified morphologically and molecularly. RESULTS The findings revealed that An. gambiae sensu stricto (s.s.) (62%) was more prevalent than Anopheles arabiensis (38%). The WHO tube bioassays confirmed resistance to deltamethrin 0.05% in the Oshikoto, Kunene, and Kavango West regions, with mortality rates of 79, 86, and 67%, respectively. In contrast, An. arabiensis displayed resistance to deltamethrin 0.05% in Oshikoto (82% mortality) and reduced susceptibility in Kavango West (96% mortality). Notably, there was reduced susceptibility to DDT 4% in both An. gambiae s.s. and An. arabiensis from the Kavango West region. Subsequently, a subsample from PBO synergist assays in 2020 demonstrated a high proportion of An. arabiensis in Oshana (84.4%) and Oshikoto (73.6%), and 0.42% of Anopheles quadriannulatus in Oshana. Non-amplifiers were also present (15.2% in Oshana; 26.4% in Oshikoto). Deltamethrin resistance with less than 95% mortality, was consistently observed in An. gambiae s.l. populations across all sites in both 2020 and 2021. Following pre-exposure to the PBO synergist, susceptibility to deltamethrin was fully restored with 100.0% mortality at all sites in 2020 and 2021. CONCLUSIONS Pyrethroid resistance has been identified in An. gambiae s.s. and An. arabiensis in the Kavango West, Kunene, and Oshikoto regions, indicating potential challenges for pyrethroid-based IRS and LLINs. Consequently, the data highlights the promise of pyrethroid-PBO LLINs in addressing resistance issues in the region.
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Affiliation(s)
| | | | | | | | - Munyaradzi Tambo
- University of Namibia (UNAM), Windhoek, Namibia
- Washington University School of Medicine, St. Louis, MO, USA
| | - Iitula Iitula
- Ministry of Health and Social Services (MoHSS), Windhoek, Namibia
| | - Lydia Eloff
- University of Namibia (UNAM), Windhoek, Namibia
| | - Ophilia Lukubwe
- Clinton Health Access Initiative (CHAI), Boston, MA, USA
- Namibia University of Science and Technology, Windhoek, Namibia
| | - Cara Smith-Gueye
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
| | - Élodie A Vajda
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
| | - Allison Tatarsky
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
| | - Stark T Katokele
- Ministry of Health and Social Services (MoHSS), Windhoek, Namibia
| | - Petrina N Uusiku
- Ministry of Health and Social Services (MoHSS), Windhoek, Namibia
| | | | - Sheila B Ogoma
- Clinton Health Access Initiative (CHAI), Boston, MA, USA
| | | | - Neil F Lobo
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
- University of Notre Dame, Notre Dame, IN, USA
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Erriah B, Shtukenberg AG, Aronin R, McCarthy D, Brázda P, Ward MD, Kahr B. ROY Crystallization on Poly(ethylene) Fibers, a Model for Bed Net Crystallography. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:2432-2440. [PMID: 38495899 PMCID: PMC10938503 DOI: 10.1021/acs.chemmater.3c03188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/13/2024] [Accepted: 02/14/2024] [Indexed: 03/19/2024]
Abstract
Many long-lasting insecticidal bed nets for protection against disease vectors consist of poly(ethylene) fibers in which insecticide is incorporated during manufacture. Insecticide molecules diffuse from within the supersaturated polymers to surfaces where they become bioavailable to insects and often crystallize, a process known as blooming. Recent studies revealed that contact insecticides can be highly polymorphic. Moreover, insecticidal activity is polymorph-dependent, with forms having a higher crystal free energy yielding faster insect knockdown and mortality. Consequently, the crystallographic characterization of insecticide crystals that form on fibers is critical to understanding net function and improving net performance. Structural characterization of insecticide crystals on bed net fiber surfaces, let alone their polymorphs, has been elusive owing to the minute size of the crystals, however. Using the highly polymorphous compound ROY (5-methyl-2-[(2-nitrophenyl)-amino]thiophene-3-carbonitrile) as a proxy for insecticide crystallization, we investigated blooming and crystal formation on the surface of extruded poly(ethylene) fibers containing ROY. The blooming rates, tracked from the time of extrusion, were determined by UV-vis spectroscopy after successive washes. Six crystalline polymorphs (of the 13 known) were observed on poly(ethylene) fiber surfaces, and they were identified and characterized by Raman microscopy, scanning electron microscopy, and 3D electron diffraction. These observations reveal that the crystallization and phase behavior of polymorphs forming on poly(ethylene) fibers is complex and dynamic. The characterization of blooming and microcrystals underscores the importance of bed net crystallography for the optimization of bed net performance.
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Affiliation(s)
- Bryan Erriah
- Department
of Chemistry and Molecular Design Institute, New York University, New York, 29 Washington Place, New York City, New York 10003, United States
| | - Alexander G. Shtukenberg
- Department
of Chemistry and Molecular Design Institute, New York University, New York, 29 Washington Place, New York City, New York 10003, United States
| | - Reese Aronin
- Department
of Chemistry and Molecular Design Institute, New York University, New York, 29 Washington Place, New York City, New York 10003, United States
| | - Derik McCarthy
- Department
of Chemistry and Molecular Design Institute, New York University, New York, 29 Washington Place, New York City, New York 10003, United States
| | - Petr Brázda
- Department
of Structure Analysis, Institute of Physics, Czech Academy of Sciences, Na Slovance 2/1999, Prague 8 18221, Czech Republic
| | - Michael D. Ward
- Department
of Chemistry and Molecular Design Institute, New York University, New York, 29 Washington Place, New York City, New York 10003, United States
| | - Bart Kahr
- Department
of Chemistry and Molecular Design Institute, New York University, New York, 29 Washington Place, New York City, New York 10003, United States
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Plata-Pineda SE, Cárdenas-Munévar LX, Castro-Cavadía CJ, Buitrago SP, Garzón-Ospina D. Evaluating the genetic diversity of the Plasmodium vivax siap2 locus: A promising candidate for an effective malaria vaccine? Acta Trop 2024; 251:107111. [PMID: 38151069 DOI: 10.1016/j.actatropica.2023.107111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 11/27/2023] [Accepted: 12/24/2023] [Indexed: 12/29/2023]
Abstract
Malaria is the deadliest parasitic disease in the world. Traditional control measures have become less effective; hence, there is a need to explore alternative strategies, such as antimalarial vaccines. However, designing an anti-Plasmodium vivax vaccine is considered a challenge due to the complex parasite biology and the antigens' high genetic diversity. Recently, the sporozoite invasion-associated protein 2 (SIAP2) has been suggested as a potential antigen to be considered in vaccine design due to its significance during hepatocyte invasion. However, its use may be limited by the incomplete understanding of gene/protein diversity. Here, the genetic diversity of pvsiap2 using P. vivax DNA samples from Colombia was assessed. Through PCR amplification and sequencing, we compared the Colombian sequences with available worldwide sequences, revealing that pvsiap2 displays low genetic diversity. Molecular evolutionary analyses showed that pvsiap2 appears to be influenced by directional selection. Moreover, the haplotypes found differ by a few mutational steps and several of them were shared between different geographical areas. On the other hand, several conserved regions within PvSIAP2 were predicted as potential B-cell or T-cell epitopes. Considering these characteristics and its role in hepatocyte invasion, the PvSIAP2 protein emerges as a promising antigen to be considered in a multi-antigen-multi-stage (multivalent) fully effective vaccine against P. vivax malaria.
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Affiliation(s)
- Sergio E Plata-Pineda
- School of Biological Sciences, Grupo de Estudios en Genética y Biología Molecular (GEBIMOL), Universidad Pedagógica y Tecnológica de Colombia - UPTC, Tunja, Boyacá, Colombia
| | - Laura X Cárdenas-Munévar
- School of Biological Sciences, Grupo de Estudios en Genética y Biología Molecular (GEBIMOL), Universidad Pedagógica y Tecnológica de Colombia - UPTC, Tunja, Boyacá, Colombia
| | - Carlos J Castro-Cavadía
- Grupo de Investigaciones Microbiológicas y Biomédicas de Córdoba (GIMBIC), School of Health Sciences, Universidad de Córdoba, Montería, Córdoba, Colombia
| | - Sindy P Buitrago
- School of Biological Sciences, Grupo de Estudios en Genética y Biología Molecular (GEBIMOL), Universidad Pedagógica y Tecnológica de Colombia - UPTC, Tunja, Boyacá, Colombia; Population Genetics And Molecular Evolution (PGAME), Fundación Scient, Tunja, Boyacá, Colombia
| | - Diego Garzón-Ospina
- School of Biological Sciences, Grupo de Estudios en Genética y Biología Molecular (GEBIMOL), Universidad Pedagógica y Tecnológica de Colombia - UPTC, Tunja, Boyacá, Colombia; Population Genetics And Molecular Evolution (PGAME), Fundación Scient, Tunja, Boyacá, Colombia.
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Davis EL, Hollingsworth TD, Keeling MJ. An analytically tractable, age-structured model of the impact of vector control on mosquito-transmitted infections. PLoS Comput Biol 2024; 20:e1011440. [PMID: 38484022 DOI: 10.1371/journal.pcbi.1011440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 03/26/2024] [Accepted: 02/09/2024] [Indexed: 03/27/2024] Open
Abstract
Vector control is a vital tool utilised by malaria control and elimination programmes worldwide, and as such it is important that we can accurately quantify the expected public health impact of these methods. There are very few previous models that consider vector-control-induced changes in the age-structure of the vector population and the resulting impact on transmission. We analytically derive the steady-state solution of a novel age-structured deterministic compartmental model describing the mosquito feeding cycle, with mosquito age represented discretely by parity-the number of cycles (or successful bloodmeals) completed. Our key model output comprises an explicit, analytically tractable solution that can be used to directly quantify key transmission statistics, such as the effective reproductive ratio under control, Rc, and investigate the age-structured impact of vector control. Application of this model reinforces current knowledge that adult-acting interventions, such as indoor residual spraying of insecticides (IRS) or long-lasting insecticidal nets (LLINs), can be highly effective at reducing transmission, due to the dual effects of repelling and killing mosquitoes. We also demonstrate how larval measures can be implemented in addition to adult-acting measures to reduce Rc and mitigate the impact of waning insecticidal efficacy, as well as how mid-ranges of LLIN coverage are likely to experience the largest effect of reduced net integrity on transmission. We conclude that whilst well-maintained adult-acting vector control measures are substantially more effective than larval-based interventions, incorporating larval control in existing LLIN or IRS programmes could substantially reduce transmission and help mitigate any waning effects of adult-acting measures.
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Affiliation(s)
- Emma L Davis
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology, University of Warwick, Coventry, United Kingdom
| | | | - Matt J Keeling
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology, University of Warwick, Coventry, United Kingdom
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Sih C, Protopopoff N, Koffi AA, Ahoua Alou LP, Dangbenon E, Messenger LA, Kulkarni MA, Zoh MG, Camara S, Assi SB, N'Guessan R, Cook J. Efficacy of chlorfenapyr-pyrethroid and piperonyl butoxide-pyrethroid long-lasting insecticidal nets (LLINs) compared to pyrethroid-only LLINs for malaria control in Côte d'Ivoire: a three group, cluster randomised trial. Trials 2024; 25:151. [PMID: 38419075 PMCID: PMC10900640 DOI: 10.1186/s13063-024-07969-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 02/05/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND The massive scale-up of long-lasting insecticidal nets (LLIN) has led to a major reduction in malaria burden in many sub-Saharan African (SSA) countries. The World Health Organization (WHO) has recently issued a strong recommendation for the use of chlorfenapyr-pyrethroid LLINs compared to standard pyrethroid-only LLINs in areas of high insecticide resistance intensity. However, there is still a lack of conclusive evidence on the efficacy of piperonyl butoxide-pyrethroid (PBO-py) LLINs, especially in West Africa, where vector composition and resistance mechanisms may be different from vectors in East Africa. METHODS This is a three-arm, superiority, triple-blinded, cluster randomised trial, with village as the unit of randomisation. This study conducted in Côte d'Ivoire will evaluate the efficacy on epidemiological and entomological outcomes of (1) the control arm: MAGNet® LN, which contains the pyrethroid, alpha-cypermethrin, (2) VEERALIN® LN, a net combining the synergist PBO and alpha-cypermethrin, and (3) Interceptor® G2 LN, which incorporates chlorfenapyr and alpha-cypermethrin, two adulticides with different mechanisms of action. A total of 33 villages with an average of 200 households per village will be identified, mapped, and randomised in a ratio of 1:1:1. Nets will be distributed at a central point following national guidelines with 1 net for every 2 people. The primary outcome of the trial will be incidence of malaria cases (confirmed by rapid diagnostic test (RDT)) in a cohort of 50 children aged 6 months to 10 years in each cluster, followed for 12 months (active case detection). Secondary outcomes are cross-sectional community prevalence of malaria infection (confirmed by RDT) in the study population at 6 and 12 months post-intervention (50 randomly selected persons per cluster), vector density, entomological inoculation rate (EIR), and phenotypic and genotypic insecticide resistance at baseline and 12 months post-intervention in 3 sentinel villages in each treatment arm. DISCUSSION In addition to generating further evidence for next-generation LLINs, this study will also provide the first evidence for pyrethroid-PBO nets in a West African setting. This could further inform WHO recommendations on the pragmatic use of pyrethroid-PBO nets. TRIAL REGISTRATION ClinicalTrials.gov NCT05796193. Registered on April 3, 2023.
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Affiliation(s)
- Colette Sih
- Faculty of Epidemiology and Population Health, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK.
| | - Natacha Protopopoff
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Alphonsine A Koffi
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Ludovic P Ahoua Alou
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Edouard Dangbenon
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Louisa A Messenger
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
- Department of Environmental and Occupational Health, School of Public Health, University of Nevada, Las Vegas, NV, 89154, USA
| | - Manisha A Kulkarni
- School of Epidemiology & Public Health, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Marius G Zoh
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Soromane Camara
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Serge B Assi
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Raphael N'Guessan
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Jackie Cook
- Faculty of Epidemiology and Population Health, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
- Medical Research Council (MRC) International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
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9
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Fairbanks EL, Saeung M, Pongsiri A, Vajda E, Wang Y, McIver DJ, Richardson JH, Tatarsky A, Lobo NF, Moore SJ, Ponlawat A, Chareonviriyaphap T, Ross A, Chitnis N. Inference for entomological semi-field experiments: Fitting a mathematical model assessing personal and community protection of vector-control interventions. Comput Biol Med 2024; 168:107716. [PMID: 38039890 DOI: 10.1016/j.compbiomed.2023.107716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/19/2023] [Accepted: 11/15/2023] [Indexed: 12/03/2023]
Abstract
The effectiveness of vector-control tools is often assessed by experiments as a reduction in mosquito landings using human landing catches (HLCs). However, HLCs alone only quantify a single characteristic and therefore do not provide information on the overall impacts of the intervention product. Using data from a recent semi-field study which used time-stratified HLCs, aspiration of non-landing mosquitoes, and blood feeding, we suggest a Bayesian inference approach for fitting such data to a stochastic model. This model considers both personal protection, through a reduction in biting, and community protection, from mosquito mortality and disarming (prolonged inhibition of blood feeding). Parameter estimates are then used to predict the reduction of vectorial capacity induced by etofenpox-treated clothing, picaridin topical repellents, transfluthrin spatial repellents and metofluthrin spatial repellents, as well as combined interventions for Plasmodium falciparum malaria in Anopleles minimus. Overall, all interventions had both personal and community effects, preventing biting and killing or disarming mosquitoes. This led to large estimated reductions in the vectorial capacity, with substantial impact even at low coverage. As the interventions aged, fewer mosquitoes were killed; however the impact of some interventions changed from killing to disarming mosquitoes. Overall, this inference method allows for additional modes of action, rather than just reduction in biting, to be parameterised and highlights the tools assessed as promising malaria interventions.
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Affiliation(s)
- Emma L Fairbanks
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland.
| | - Manop Saeung
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Arissara Pongsiri
- Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | - Elodie Vajda
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland; Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Yuqian Wang
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
| | - David J McIver
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Allison Tatarsky
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Sarah J Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland; Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, United Republic of Tanzania; The Nelson Mandela, African Institution of Science and Technology, School of Life Sciences and Bio Engineering, Tengeru, Arusha, United Republic of Tanzania
| | - Alongkot Ponlawat
- Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | | | - Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
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10
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Abbott AJ, Matope A, Jones J, Voloshin V, Towers CE, Towers D, McCall PJ. Insecticidal roof barriers mounted on untreated bed nets can be as effective against Anopheles gambiae as regular insecticide-treated bed nets. Sci Rep 2023; 13:22080. [PMID: 38086842 PMCID: PMC10716170 DOI: 10.1038/s41598-023-48499-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 11/27/2023] [Indexed: 12/18/2023] Open
Abstract
Barrier bednets (BBnets), regular bednets with a vertical insecticidal panel to target mosquitoes above the bednet roof, where they are most active, have the potential to improve existing Insecticidal Treated Bednets (ITNs), by reducing the quantity of insecticide required per net, reducing the toxic risks to those using the net, potentially increasing insecticide choice. We evaluated the performance of PermaNet 3.0 (P3) and untreated (Ut) bed nets with and without pyrethroid and piperonyl butoxide roof barriers in killing pyrethroid-resistant and susceptible Anopheles gambiae, simultaneously video-recording mosquito flight tracks. Bioassay results showed that treated roof barriers, particularly the longitudinal P3 barrier (P3L) could be an effective addition to a bed net: P3 + P3L were consistently significantly more effective than the reference P3 bednet while performance of untreated nets could be raised to equal that of the reference P3 following the addition of a P3 barrier. The BBnet's potential to augment existing bednets and enhance their performance is considered.
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Affiliation(s)
- Anthony J Abbott
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Agnes Matope
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Jeff Jones
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Vitaly Voloshin
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Catherine E Towers
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - David Towers
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Philip J McCall
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK.
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11
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Cushing JM, Park J, Farrell A, Chitnis N. Treatment outcome in an SI model with evolutionary resistance: a Darwinian model for the evolution of resistance. JOURNAL OF BIOLOGICAL DYNAMICS 2023; 17:2255061. [PMID: 37733402 DOI: 10.1080/17513758.2023.2255061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 08/30/2023] [Indexed: 09/22/2023]
Abstract
We consider a Darwinian (evolutionary game theoretic) version of a standard susceptible-infectious SI model in which the resistance of the disease causing pathogen to a treatment that prevents death to infected individuals is subject to evolutionary adaptation. We determine the existence and stability of all equilibria, both disease-free and endemic, and use the results to determine conditions under which the treatment will succeed or fail. Of particular interest are conditions under which a successful treatment in the absence of resistance adaptation (i.e. one that leads to a stable disease-free equilibrium) will succeed or fail when pathogen resistance is adaptive. These conditions are determined by the relative breadths of treatment effectiveness and infection transmission rate distributions as functions of pathogen resistance.
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Affiliation(s)
- J M Cushing
- Department of Mathematics, University of Arizona, Interdisciplinary Program in Applied Mathematics, Tucson, AZ, USA
| | - Junpyo Park
- Department of Applied Mathematics, College of Applied Science, Kyung Hee University, Yongin, Republic of Korea
| | - Alex Farrell
- Caris Life Sciences, Phoenix, AZ, USA
- Department of Mathematics, University of Arizona, Tucson, AZ, USA
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
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12
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Pazmiño-Betancourth M, Ochoa-Gutiérrez V, Ferguson HM, González-Jiménez M, Wynne K, Baldini F, Childs D. Evaluation of diffuse reflectance spectroscopy for predicting age, species, and cuticular resistance of Anopheles gambiae s.l under laboratory conditions. Sci Rep 2023; 13:18499. [PMID: 37898634 PMCID: PMC10613238 DOI: 10.1038/s41598-023-45696-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 10/23/2023] [Indexed: 10/30/2023] Open
Abstract
Mid-infrared spectroscopy (MIRS) combined with machine learning analysis has shown potential for quick and efficient identification of mosquito species and age groups. However, current technology to collect spectra is destructive to the sample and does not allow targeting specific tissues of the mosquito, limiting the identification of other important biological traits such as insecticide resistance. Here, we assessed the use of a non-destructive approach of MIRS for vector surveillance, micro diffuse reflectance spectroscopy (µDRIFT) using mosquito legs to identify species, age and cuticular insecticide resistance within the Anopheles gambiae s.l. complex. These mosquitoes are the major vectors of malaria in Africa and the focus on surveillance in malaria control programs. Legs required significantly less scanning time and showed more spectral consistence compared to other mosquito tissues. Machine learning models were able to identify An. gambiae and An. coluzzii with an accuracy of 0.73, two ages groups (3 and 10 days old) with 0.77 accuracy and we obtained accuracy of 0.75 when identifying cuticular insecticide resistance. Our results highlight the potential of different mosquito tissues and µDRIFT as tools for biological trait identification on mosquitoes that transmit malaria. These results can guide new ways of identifying mosquito traits which can help the creation of innovative surveillance programs by adapting new technology into mosquito surveillance and control tools.
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Affiliation(s)
- Mauro Pazmiño-Betancourth
- School of Engineering, University of Glasgow, Glasgow, G12 8QQ, UK.
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.
| | - Victor Ochoa-Gutiérrez
- School of Engineering, University of Glasgow, Glasgow, G12 8QQ, UK
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Heather M Ferguson
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | | | - Klaas Wynne
- School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Francesco Baldini
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | - David Childs
- School of Engineering, University of Glasgow, Glasgow, G12 8QQ, UK
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13
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Matope A, Lees RS, Spiers A, Foster GM. A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools. Malar J 2023; 22:289. [PMID: 37770855 PMCID: PMC10540336 DOI: 10.1186/s12936-023-04717-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Accepted: 09/13/2023] [Indexed: 09/30/2023] Open
Abstract
Vector control interventions play a fundamental role in the control and elimination of vector-borne diseases. The evaluation of vector control products relies on bioassays, laboratory and semi-field tests using live insects to assess the product's effectiveness. Bioassay method development requires a rigorous validation process to ensure that relevant methods are used to capture appropriate entomological endpoints which accurately and precisely describe likely efficacy against disease vectors as well as product characteristics within the manufacturing tolerance ranges for insecticide content specified by the World Health Organization. Currently, there are no standardized guidelines for bioassay method validation in vector control. This report presents a framework for bioassay validation that draws on accepted validation processes from the chemical and healthcare fields and which can be applied for evaluating bioassays and semi-field tests in vector control. The validation process has been categorized into four stages: preliminary development; feasibility experiments; internal validation, and external validation. A properly validated method combined with an appropriate experimental design and data analyses that account for both the variability of the method and the product is needed to generate reliable estimates of product efficacy to ensure that at-risk communities have timely access to safe and reliable vector control products.
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Affiliation(s)
- Agnes Matope
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Rosemary S Lees
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
- Innovation to Impact (I2I), Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Angus Spiers
- Innovation to Impact (I2I), Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Geraldine M Foster
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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14
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Nkahe DL, Sonhafouo-Chiana N, Ndjeunia Mbiakop P, Kekeunou S, Mimpfoundi R, Awono-Ambene P, Wondji CS, Antonio-Nkondjio C. Can the use of larviciding with biological compounds contribute in increasing Anopheles gambiae s.l. susceptibility to pyrethroid in a population expressing high resistance intensity? PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2023; 195:105569. [PMID: 37666599 DOI: 10.1016/j.pestbp.2023.105569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/05/2023] [Indexed: 09/06/2023]
Abstract
BACKGROUND Larviciding using non-insecticide compounds is considered appropriate for controlling outdoor biting mosquitoes and for managing insecticide resistance. However, there is still not enough information on the influence of larviciding in managing pyrethroid resistance. In the present study, we checked whether the introduction of larviciding using the biolarvicide VectoMax G in the city of Yaoundé is contributing in restoring the susceptibility of An. coluzzii populations to pyrethroids. METHODOLOGY The susceptibility status of field An. coluzzii population was evaluated at different time points before and during larviciding treatments. In addition, An. coluzzii larvae collected in the city of Yaoundé, were split into four groups and exposed to different selection regimes for many generations as follow; (i): deltamethrin 0.05%_only, (ii): Vectomax_only, (iii): Vectomax+deltamethrin 0.05%, (iv): VectoMax+deltamethrin 0.05% + susceptible. Life traits parameters were measured in the progeny and compared between colonies. The control was the susceptible laboratory strain "Ngousso". Kdr allele frequency and the profile of expression of different detoxification genes and oxidative stress genes was checked using qPCR analysis. Gene's expression was compared between the first and the last generation of each colony and in field populations collected before and during larviciding. RESULTS An increase in mosquito susceptibility to deltamethrin and permethrin was recorded for the field populations after larviciding implementation. Resistance intensity to deltamethrin was found to decrease from high to low in field populations. Only the colony vectomax+deltamethrin+susceptible presented a high susceptibility to deltamethrin after 21 generations. The kdr gene frequency was found to be unchanged in the field population and laboratory colonies. A significant decrease in the overexpression profile of Gste2 was detected in field population after larviciding implementation. Other genes showing a similar pattern though not significant were Cyp6z1, Cyp6p1 and Cyp6g16. Concerning fitness only the colony vectomax+deltamethrin+susceptible was found to display a fitness profile similar to the susceptible colony with high fecundity, high hatching rate, short development time and long adult survival rate. CONCLUSION The profile of the field population supported reversal of phenotypic resistance to pyrethroids however no reduction in the frequency of the kdr allele was recorded. Some detoxification genes were detected less overexpressed. The study suggest that reversal may take longer to achieve in a population expressing a very high resistance profile and under continuous insecticide selection pressure.
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Affiliation(s)
- Diane Leslie Nkahe
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon; Department of Animal Physiology and Biology, Faculty of Science, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Nadege Sonhafouo-Chiana
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon; Faculty of Science, University of Buea, Buea, P.O. Box 63, Cameroon
| | - Paulette Ndjeunia Mbiakop
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon; Department of Animal Physiology and Biology, Faculty of Science, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Sévilor Kekeunou
- Department of Animal Physiology and Biology, Faculty of Science, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Rémy Mimpfoundi
- Department of Animal Physiology and Biology, Faculty of Science, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Parfait Awono-Ambene
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Charles Sinclair Wondji
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13591, Yaoundé, Cameroon; Vector Biology Liverpool School of Tropical medicine Pembroke Place, Liverpool L3 5QA, UK.
| | - Christophe Antonio-Nkondjio
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon; Faculty of Medicine Paris-Sud, 63 rue Gabriel Peri, 94276, Le Kremlin-Bicêtre, Paris, France..
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15
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Sagna AB, Zéla L, Ouedraogo COW, Pooda SH, Porciani A, Furnival-Adams J, Lado P, Somé AF, Pennetier C, Chaccour CJ, Dabiré RK, Mouline K. Ivermectin as a novel malaria control tool: Getting ahead of the resistance curse. Acta Trop 2023; 245:106973. [PMID: 37352998 DOI: 10.1016/j.actatropica.2023.106973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/14/2023] [Accepted: 06/16/2023] [Indexed: 06/25/2023]
Abstract
Reduction in malaria clinical cases is strongly dependent on the ability to prevent Anopheles infectious bites. Vector control strategies using long-lasting insecticidal nets and indoor residual spraying with insecticides have contributed to significantly reduce the incidence of malaria in many endemic countries, especially in the Sub-Saharan region. However, global progress in reducing malaria cases has plateaued since 2015 mostly due to the increased insecticide resistance and behavioral changes in Anopheles vectors. Additional control strategies are thus required to further reduce the burden of malaria and contain the spread of resistant and invasive Anopheles vectors. The use of endectocides such as ivermectin as an additional malaria control tool is now receiving increased attention, driven by its different mode of action compared to insecticides used so far and its excellent safety record for humans. In this opinion article, we discuss the advantages and disadvantages of using ivermectin for malaria control with a focus on the risk of selecting ivermectin resistance in malaria vectors. We also highlight the importance of understanding how ivermectin resistance could develop in mosquitoes and what its underlying mechanisms and associated molecular markers are, and propose a research agenda to manage this phenomenon.
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Affiliation(s)
- André B Sagna
- MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France.
| | - Lamidi Zéla
- Centre International de Recherche-Développement sur l'Elevage en zone Subhumide, Bobo-Dioulasso, Burkina Faso
| | - Cheick Oumar W Ouedraogo
- Institut de Recherche en Sciences de la Santé, Direction Régionale de l'Ouest, Centre National de Recherche Scientifique et Technologique, Bobo-Dioulasso, Burkina Faso
| | - Sié H Pooda
- Centre International de Recherche-Développement sur l'Elevage en zone Subhumide, Bobo-Dioulasso, Burkina Faso; Université de Dédougou, Dédougou, Burkina Faso
| | | | | | - Paula Lado
- Center for Vector-borne Infectious Diseases, Colorado State University, Fort Collins, CO, USA
| | - Anyirékun F Somé
- Institut de Recherche en Sciences de la Santé, Direction Régionale de l'Ouest, Centre National de Recherche Scientifique et Technologique, Bobo-Dioulasso, Burkina Faso
| | - Cédric Pennetier
- MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France
| | - Carlos J Chaccour
- ISGlobal, Barcelona Institute for Global Health, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Infecciosas, Madrid, Spain; Universidad de Navarra, Pamplona, Spain
| | - Roch K Dabiré
- Institut de Recherche en Sciences de la Santé, Direction Régionale de l'Ouest, Centre National de Recherche Scientifique et Technologique, Bobo-Dioulasso, Burkina Faso
| | - Karine Mouline
- MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France
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16
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Syme T, Nounagnon J, N'dombidjé B, Gbegbo M, Agbevo A, Ahoga J, Ngufor C. Can the performance of pyrethroid-chlorfenapyr nets be reduced when combined with pyrethroid-piperonyl butoxide (PBO) nets? Malar J 2023; 22:214. [PMID: 37480030 PMCID: PMC10362717 DOI: 10.1186/s12936-023-04648-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 07/14/2023] [Indexed: 07/23/2023] Open
Abstract
BACKGROUND Pyrethroid-chlorfenapyr (CFP) and pyrethroid-piperonyl butoxide (PBO) nets are being scaled across endemic countries to improve control of malaria transmitted by pyrethroid-resistant mosquitoes. CFP is a pro-insecticide requiring activation by mosquito cytochrome P450 monooxygenase enzymes (P450s) while PBO improves pyrethroid potency by inhibiting the action of these enzymes in pyrethroid-resistant mosquitoes. The inhibitory action of PBO against P450s may thus reduce the efficacy of pyrethroid-CFP nets when applied inside the same household as pyrethroid-PBO nets. METHODS Two experimental hut trials were performed to evaluate the entomological impact of two different types of pyrethroid-CFP ITN (Interceptor® G2, PermaNet® Dual) when applied alone and in combination with pyrethroid-PBO ITNs (DuraNet® Plus, PermaNet® 3.0) against a pyrethroid-resistant vector population in southern Benin. In both trials, all net types were tested as single and double net treatments. Bioassays were also performed to assess the resistance profile of the vector population at the hut site and investigate interactions between CFP and PBO. RESULTS The vector population was susceptible to CFP but exhibited a high intensity of pyrethroid resistance that was overcame by PBO pre-exposure. Vector mortality was significantly lower in huts with combinations of pyrethroid-CFP nets plus pyrethroid-PBO nets compared to huts with two pyrethroid-CFP nets (74% vs. 85% for Interceptor® G2 and 57% vs. 83% for PermaNet® Dual, p < 0.001). PBO pre-exposure reduced the toxicity of CFP in bottle bioassays suggesting this effect may be partly attributable to antagonism between CFP and PBO. Higher levels of vector mortality were observed in huts with net combinations that included pyrethroid-CFP nets compared to those that did not and highest mortality was achieved when pyrethroid-CFP nets were applied alone as two nets together (83-85%). CONCLUSIONS This study shows evidence of a reduced performance of pyrethroid-CFP nets when combined with pyrethroid-PBO ITNs compared to when applied alone and higher efficacy with net combinations that included pyrethroid-CFP nets. These findings suggest that in similar contexts, prioritizing distribution of pyrethroid-CFP nets over other net types would maximize vector control impact.
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Affiliation(s)
- Thomas Syme
- London School of Hygiene & Tropical Medicine, London, UK.
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin.
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
| | - Judicaël Nounagnon
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Boris N'dombidjé
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Martial Gbegbo
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Abel Agbevo
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Juniace Ahoga
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Corine Ngufor
- London School of Hygiene & Tropical Medicine, London, UK.
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin.
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
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17
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Koffi AA, Camara S, Ahoua Alou LP, Oumbouke WA, Wolie RZ, Tia IZ, Sternberg ED, Yapo FHA, Koffi FM, Assi SB, Cook J, Thomas MB, N'Guessan R. Anopheles vector distribution and malaria transmission dynamics in Gbêkê region, central Côte d'Ivoire. Malar J 2023; 22:192. [PMID: 37349819 DOI: 10.1186/s12936-023-04623-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 06/14/2023] [Indexed: 06/24/2023] Open
Abstract
BACKGROUND A better understanding of vector distribution and malaria transmission dynamics at a local scale is essential for implementing and evaluating effectiveness of vector control strategies. Through the data gathered in the framework of a cluster randomized controlled trial (CRT) evaluating the In2Care (Wageningen, Netherlands) Eave Tubes strategy, the distribution of the Anopheles vector, their biting behaviour and malaria transmission dynamics were investigated in Gbêkê region, central Côte d'Ivoire. METHODS From May 2017 to April 2019, adult mosquitoes were collected monthly using human landing catches (HLC) in twenty villages in Gbêkê region. Mosquito species wereidentified morphologically. Monthly entomological inoculation rates (EIR) were estimated by combining the HLC data with mosquito sporozoite infection rates measured in a subset of Anopheles vectors using PCR. Finally, biting rate and EIR fluctuations were fit to local rainfall data to investigate the seasonal determinants of mosquito abundance and malaria transmission in this region. RESULTS Overall, Anopheles gambiae, Anopheles funestus, and Anopheles nili were the three vector complexes found infected in the Gbêkê region, but there was a variation in Anopheles vector composition between villages. Anopheles gambiae was the predominant malaria vector responsible for 84.8% of Plasmodium parasite transmission in the area. An unprotected individual living in Gbêkê region received an average of 260 [222-298], 43.5 [35.8-51.29] and 3.02 [1.96-4] infected bites per year from An. gambiae, An. funestus and An. nili, respectively. Vector abundance and malaria transmission dynamics varied significantly between seasons and the highest biting rate and EIRs occurred in the months of heavy rainfall. However, mosquitoes infected with malaria parasites remained present in the dry season, despite the low density of mosquito populations. CONCLUSION These results demonstrate that the intensity of malaria transmission is extremely high in Gbêkê region, especially during the rainy season. The study highlights the risk factors of transmission that could negatively impact current interventions that target indoor control, as well as the urgent need for additional vector control tools to target the population of malaria vectors in Gbêkê region and reduce the burden of the disease.
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Affiliation(s)
- Alphonsine A Koffi
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
| | - Soromane Camara
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire.
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire.
| | - Ludovic P Ahoua Alou
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
| | - Welbeck A Oumbouke
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
- Innovative Vector Control Consortium, IVCC, Liverpool, UK
| | - Rosine Z Wolie
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
- Unité de Recherche et de Pédagogie de Génétique, Université Félix Houphouët-Boigny, UFR Biosciences, Abidjan, Côte d'Ivoire
| | - Innocent Z Tia
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
- Centre d'Entomologie Médicale et Vétérinaire, Université Allassane Ouattara, Bouaké, Côte d'Ivoire
| | | | - Florent H A Yapo
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
| | - Fernand M Koffi
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
| | - Serge B Assi
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Jackie Cook
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Matthew B Thomas
- Department of Entomology & Nematology, The University of Florida, Gainesville, FL, USA
| | - Raphael N'Guessan
- Institut Pierre Richet (IPR)/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
- Vector Control Product Evaluation Centre (VCPEC), Institut Pierre Richet (VCPEC-IPR)/INSP, Bouaké, Côte d'Ivoire
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
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18
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Coleman S, Yihdego Y, Gyamfi F, Kolyada L, Tongren JE, Zigirumugabe S, Dery DB, Badu K, Obiri-Danso K, Boakye D, Szumlas D, Armistead JS, Dadzie SK. Estimating malaria transmission risk through surveillance of human-vector interactions in northern Ghana. Parasit Vectors 2023; 16:205. [PMID: 37337221 DOI: 10.1186/s13071-023-05793-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 04/28/2023] [Indexed: 06/21/2023] Open
Abstract
BACKGROUND Vector bionomics are important aspects of vector-borne disease control programs. Mosquito-biting risks are affected by environmental, mosquito behavior and human factors, which are important for assessing exposure risk and intervention impacts. This study estimated malaria transmission risk based on vector-human interactions in northern Ghana, where indoor residual spraying (IRS) and insecticide-treated nets (ITNs) have been deployed. METHODS Indoor and outdoor human biting rates (HBRs) were measured using monthly human landing catches (HLCs) from June 2017 to April 2019. Mosquitoes collected were identified to species level, and Anopheles gambiae sensu lato (An. gambiae s.l.) samples were examined for parity and infectivity. The HBRs were adjusted using mosquito parity and human behavioral observations. RESULTS Anopheles gambiae was the main vector species in the IRS (81%) and control (83%) communities. Indoor and outdoor HBRs were similar in both the IRS intervention (10.6 vs. 11.3 bites per person per night [b/p/n]; z = -0.33, P = 0.745) and control communities (18.8 vs. 16.4 b/p/n; z = 1.57, P = 0.115). The mean proportion of parous An. gambiae s.l. was lower in IRS communities (44.6%) than in control communities (71.7%). After adjusting for human behavior observations and parity, the combined effect of IRS and ITN utilization (IRS: 37.8%; control: 57.3%) on reducing malaria transmission risk was 58% in IRS + ITN communities and 27% in control communities with ITNs alone (z = -4.07, P < 0.001). However, this also revealed that about 41% and 31% of outdoor adjusted bites in IRS and control communities respectively, occurred before bed time (10:00 pm). The mean directly measured annual entomologic inoculation rates (EIRs) during the study were 6.1 infective bites per person per year (ib/p/yr) for IRS communities and 16.3 ib/p/yr for control communities. After considering vector survival and observed human behavior, the estimated EIR for IRS communities was 1.8 ib/p/yr, which represents about a 70% overestimation of risk compared to the directly measured EIR; for control communities, it was 13.6 ib/p/yr (16% overestimation). CONCLUSION Indoor residual spraying significantly impacted entomological indicators of malaria transmission. The results of this study indicate that vector bionomics alone do not provide an accurate assessment of malaria transmission exposure risk. By accounting for human behavior parameters, we found that high coverage of ITNs alone had less impact on malaria transmission indices than combining ITNs with IRS, likely due to observed low net use. Reinforcing effective communication for behavioral change in net use and IRS could further reduce malaria transmission.
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Affiliation(s)
- Sylvester Coleman
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana.
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Yemane Yihdego
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana
| | - Frank Gyamfi
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana
| | - Lena Kolyada
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana
| | - Jon Eric Tongren
- U.S. President's Malaria Initiative, Malaria Branch, U.S. Centers for Disease Control and Prevention, Accra, Ghana
| | - Sixte Zigirumugabe
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Accra, Ghana
| | - Dominic B Dery
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Accra, Ghana
| | - Kingsley Badu
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | | | - Daniel Boakye
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
| | - Daniel Szumlas
- Armed Forces Pest Management Board, 172 Forney Road, Forest Glen Annex, Silver Spring, MD, 20910, USA
| | - Jennifer S Armistead
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Washington, DC, USA
| | - Samuel K Dadzie
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
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Ozodiegwu ID, Ambrose M, Galatas B, Runge M, Nandi A, Okuneye K, Dhanoa NP, Maikore I, Uhomoibhi P, Bever C, Noor A, Gerardin J. Application of mathematical modelling to inform national malaria intervention planning in Nigeria. Malar J 2023; 22:137. [PMID: 37101146 PMCID: PMC10130303 DOI: 10.1186/s12936-023-04563-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 04/15/2023] [Indexed: 04/28/2023] Open
Abstract
BACKGROUND For their 2021-2025 National Malaria Strategic Plan (NMSP), Nigeria's National Malaria Elimination Programme (NMEP), in partnership with the World Health Organization (WHO), developed a targeted approach to intervention deployment at the local government area (LGA) level as part of the High Burden to High Impact response. Mathematical models of malaria transmission were used to predict the impact of proposed intervention strategies on malaria burden. METHODS An agent-based model of Plasmodium falciparum transmission was used to simulate malaria morbidity and mortality in Nigeria's 774 LGAs under four possible intervention strategies from 2020 to 2030. The scenarios represented the previously implemented plan (business-as-usual), the NMSP at an 80% or higher coverage level and two prioritized plans according to the resources available to Nigeria. LGAs were clustered into 22 epidemiological archetypes using monthly rainfall, temperature suitability index, vector abundance, pre-2010 parasite prevalence, and pre-2010 vector control coverage. Routine incidence data were used to parameterize seasonality in each archetype. Each LGA's baseline malaria transmission intensity was calibrated to parasite prevalence in children under the age of five years measured in the 2010 Malaria Indicator Survey (MIS). Intervention coverage in the 2010-2019 period was obtained from the Demographic and Health Survey, MIS, the NMEP, and post-campaign surveys. RESULTS Pursuing a business-as-usual strategy was projected to result in a 5% and 9% increase in malaria incidence in 2025 and 2030 compared with 2020, while deaths were projected to remain unchanged by 2030. The greatest intervention impact was associated with the NMSP scenario with 80% or greater coverage of standard interventions coupled with intermittent preventive treatment in infants and extension of seasonal malaria chemoprevention (SMC) to 404 LGAs, compared to 80 LGAs in 2019. The budget-prioritized scenario with SMC expansion to 310 LGAs, high bed net coverage with new formulations, and increase in effective case management rate at the same pace as historical levels was adopted as an adequate alternative for the resources available. CONCLUSIONS Dynamical models can be applied for relative assessment of the impact of intervention scenarios but improved subnational data collection systems are required to allow increased confidence in predictions at sub-national level.
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Affiliation(s)
- Ifeoma D Ozodiegwu
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA.
| | | | - Beatriz Galatas
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | - Manuela Runge
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Aadrita Nandi
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Kamaldeen Okuneye
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Neena Parveen Dhanoa
- Weinberg College of Arts and Sciences, Northwestern University, Evanston, IL, USA
| | - Ibrahim Maikore
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | | | | | - Abdisalan Noor
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | - Jaline Gerardin
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
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Gleave K, Guy A, Mechan F, Emery M, Murphy A, Voloshin V, Towers CE, Towers D, Ranson H, Foster GM, McCall PJ. Impacts of dual active-ingredient bed nets on the behavioural responses of pyrethroid resistant Anopheles gambiae determined by room-scale infrared video tracking. Malar J 2023; 22:132. [PMID: 37088828 PMCID: PMC10122874 DOI: 10.1186/s12936-023-04548-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 03/31/2023] [Indexed: 04/25/2023] Open
Abstract
BACKGROUND The success of insecticide treated bed nets (ITNs) for malaria vector control in Africa relies on the behaviour of various species of Anopheles. Previous research has described mosquito behavioural alterations resulting from widespread ITN coverage, which could result in a decrease in net efficacy. Here, behaviours were compared including timings of net contact, willingness to refeed and longevity post-exposure to two next-generation nets, PermaNet® 3.0 (P3 net) and Interceptor® G2 (IG2 net) in comparison with a standard pyrethroid-only net (Olyset Net™ (OL net)) and an untreated net. METHODS Susceptible and resistant Anopheles gambiae mosquitoes were exposed to the nets with a human volunteer host in a room-scale assay. Mosquito movements were tracked for 2 h using an infrared video system, collecting flight trajectory, spatial position and net contact data. Post-assay, mosquitoes were monitored for a range of sublethal insecticide effects. RESULTS Mosquito net contact was focused predominantly on the roof for all four bed nets. A steep decay in activity was observed for both susceptible strains when P3 net and OL net were present and with IG2 net for one of the two susceptible strains. Total mosquito activity was higher around untreated nets than ITNs. There was no difference in total activity, the number, or duration, of net contact, between any mosquito strain, with similar behaviours recorded in susceptible and resistant strains at all ITNs. OL net, P3 net and IG2 net all killed over 90% of susceptible mosquitoes 24 h after exposure, but this effect was not seen with resistant mosquitoes where mortality ranged from 16 to 72%. All treated nets reduced the willingness of resistant strains to re-feed when offered blood 1-h post-exposure, with a more pronounced effect seen with P3 net and OL net than IG2 net. CONCLUSION These are the first results to provide an in-depth description of the behaviour of susceptible and resistant Anopheles gambiae strains around next-generation bed nets using a room-scale tracking system to capture multiple behaviours. These results indicate that there is no major difference in behavioural responses between mosquito strains of differing pyrethroid susceptibility when exposed to these new ITNs under the experimental conditions used.
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Affiliation(s)
- Katherine Gleave
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Amy Guy
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Frank Mechan
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Mischa Emery
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Annabel Murphy
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | | | | | - David Towers
- School of Engineering, University of Warwick, Coventry, UK
| | - Hilary Ranson
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Geraldine M Foster
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Philip J McCall
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK.
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21
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Hobbs NP, Weetman D, Hastings IM. Insecticide resistance management strategies for public health control of mosquitoes exhibiting polygenic resistance: A comparison of sequences, rotations, and mixtures. Evol Appl 2023; 16:936-959. [PMID: 37124088 PMCID: PMC10130562 DOI: 10.1111/eva.13546] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 02/22/2023] [Accepted: 03/21/2023] [Indexed: 05/02/2023] Open
Abstract
Malaria control uses insecticides to kill Anopheles mosquitoes. Recent successes in malaria control are threatened by increasing levels of insecticide resistance (IR), requiring insecticide resistance management (IRM) strategies to mitigate this problem. Field trials of IRM strategies are usually prohibitively expensive with long timeframes, and mathematical modeling is often used to evaluate alternative options. Previous IRM models in the context of malaria control assumed IR to have a simple (monogenic) basis, whereas in natural populations, IR will often be a complex polygenic trait determined by multiple genetic variants. A quantitative genetics model was developed to model IR as a polygenic trait. The model allows insecticides to be deployed as sequences (continuous deployment until a defined withdrawal threshold, termed "insecticide lifespan", as indicated by resistance diagnosis in bioassays), rotations (periodic switching of insecticides), or full-dose mixtures (two insecticides in one formulation). These IRM strategies were compared based on their "strategy lifespan" (capped at 500 generations). Partial rank correlation and generalized linear modeling was used to identify and quantify parameters driving the evolution of resistance. Random forest models were used to identify parameters offering predictive value for decision-making. Deploying single insecticides as sequences or rotations usually made little overall difference to their "strategy lifespan", though rotations displayed lower mean and peak resistances. Deploying two insecticides in a full-dose mixture formulation was found to extend the "strategy lifespan" when compared to deploying each in sequence or rotation. This pattern was observed regardless of the level of cross resistance between the insecticides or the starting level of resistance. Statistical analysis highlighted the importance of insecticide coverage, cross resistance, heritability, and fitness costs for selecting an appropriate IRM strategy. Full-dose mixtures appear the most promising of the strategies evaluated, with the longest "strategy lifespans". These conclusions broadly corroborate previous results from monogenic models.
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Affiliation(s)
- Neil Philip Hobbs
- Department of Vector BiologyLiverpool School of Tropical MedicinePembroke PlaceLiverpoolL3 5QAUK
| | - David Weetman
- Department of Vector BiologyLiverpool School of Tropical MedicinePembroke PlaceLiverpoolL3 5QAUK
| | - Ian Michael Hastings
- Department of Tropical Disease BiologyLiverpool School of Tropical MedicinePembroke PlaceLiverpoolL3 5QAUK
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22
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Tungu P, Kabula B, Nkya T, Machafuko P, Sambu E, Batengana B, Sudi W, Derua YA, Mwingira V, Masue D, Malima R, Kitojo C, Serbantez N, Reaves EJ, Mwalimu C, Nhiga SL, Ally M, Mkali HR, Joseph JJ, Chan A, Ngondi J, Lalji S, Nyinondi S, Eckert E, Reithinger R, Magesa S, Kisinza WN. Trends of insecticide resistance monitoring in mainland Tanzania, 2004-2020. Malar J 2023; 22:100. [PMID: 36932400 PMCID: PMC10024418 DOI: 10.1186/s12936-023-04508-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 02/20/2023] [Indexed: 03/19/2023] Open
Abstract
BACKGROUND Insecticide resistance is a serious threat to the continued effectiveness of insecticide-based malaria vector control measures, such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). This paper describes trends and dynamics of insecticide resistance and its underlying mechanisms from annual resistance monitoring surveys on Anopheles gambiae sensu lato (s.l.) populations conducted across mainland Tanzania from 2004 to 2020. METHODS The World Health Organization (WHO) standard protocols were used to assess susceptibility of the wild female An. gambiae s.l. mosquitoes to insecticides, with mosquitoes exposed to diagnostic concentrations of permethrin, deltamethrin, lambdacyhalothrin, bendiocarb, and pirimiphos-methyl. WHO test papers at 5× and 10× the diagnostic concentrations were used to assess the intensity of resistance to pyrethroids; synergist tests using piperonyl butoxide (PBO) were carried out in sites where mosquitoes were found to be resistant to pyrethroids. To estimate insecticide resistance trends from 2004 to 2020, percentage mortalities from each site and time point were aggregated and regression analysis of mortality versus the Julian dates of bioassays was performed. RESULTS Percentage of sites with pyrethroid resistance increased from 0% in 2004 to more than 80% in the 2020, suggesting resistance has been spreading geographically. Results indicate a strong negative association (p = 0.0001) between pyrethroids susceptibility status and survey year. The regression model shows that by 2020 over 40% of An. gambiae mosquitoes survived exposure to pyrethroids at their respective diagnostic doses. A decreasing trend of An. gambiae susceptibility to bendiocarb was observed over time, but this was not statistically significant (p = 0.8413). Anopheles gambiae exhibited high level of susceptibility to the pirimiphos-methyl in sampled sites. CONCLUSIONS Anopheles gambiae Tanzania's major malaria vector, is now resistant to pyrethroids across the country with resistance increasing in prevalence and intensity and has been spreading geographically. This calls for urgent action for efficient malaria vector control tools to sustain the gains obtained in malaria control. Strengthening insecticide resistance monitoring is important for its management through evidence generation for effective malaria vector control decision.
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Affiliation(s)
- Patrick Tungu
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania.
| | - Bilali Kabula
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
- USAID-Okoa Maisha Dhibiti Malaria Project, RTI International, Dar es Salaam, Tanzania
| | - Theresia Nkya
- University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Pendael Machafuko
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Edward Sambu
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Bernard Batengana
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Wema Sudi
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Yahaya A Derua
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Victor Mwingira
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Denis Masue
- University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Robert Malima
- University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Chonge Kitojo
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Dar es Salaam, Tanzania
| | - Naomi Serbantez
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Dar es Salaam, Tanzania
| | - Erik J Reaves
- U.S. President's Malaria Initiative, U.S. Centers for Disease Control and Prevention, Dar es Salaam, Tanzania
| | - Charles Mwalimu
- National Malaria Control Programme, Ministry of Health, Community Development, Gender, Elderly and Children, Dodoma, Tanzania
| | - Samwel L Nhiga
- National Malaria Control Programme, Ministry of Health, Community Development, Gender, Elderly and Children, Dodoma, Tanzania
| | - Mohamed Ally
- National Malaria Control Programme, Ministry of Health, Community Development, Gender, Elderly and Children, Dodoma, Tanzania
| | - Humphrey R Mkali
- USAID-Okoa Maisha Dhibiti Malaria Project, RTI International, Dar es Salaam, Tanzania
| | - Joseph J Joseph
- USAID-Okoa Maisha Dhibiti Malaria Project, RTI International, Dar es Salaam, Tanzania
| | - Adeline Chan
- U.S. President's Malaria Initiative, U.S. Centers for Disease Control and Prevention, Atlanta, USA
| | | | - Shabbir Lalji
- USAID-Okoa Maisha Dhibiti Malaria Project, RTI International, Dar es Salaam, Tanzania
| | - Ssanyu Nyinondi
- USAID-Okoa Maisha Dhibiti Malaria Project, RTI International, Dar es Salaam, Tanzania
| | | | | | - Stephen Magesa
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - William N Kisinza
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
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23
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Unwin HJT, Sherrard-Smith E, Churcher TS, Ghani AC. Quantifying the direct and indirect protection provided by insecticide treated bed nets against malaria. Nat Commun 2023; 14:676. [PMID: 36750566 PMCID: PMC9905482 DOI: 10.1038/s41467-023-36356-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 01/27/2023] [Indexed: 02/09/2023] Open
Abstract
Long lasting insecticidal nets (LLINs) provide both direct and indirect protection against malaria. As pyrethroid resistance evolves in mosquito vectors, it will be useful to understand how the specific benefits LLINs afford individuals and communities may be affected. Here we use modelling to show that there is no minimum LLIN usage needed for users and non-users to benefit from community protection. Modelling results also indicate that pyrethroid resistance in local mosquitoes will likely diminish the direct and indirect benefits from insecticides, leaving the barrier effects intact, but LLINs are still expected to provide enhanced benefit over untreated nets even at high levels of pyrethroid resistance.
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Affiliation(s)
- H Juliette T Unwin
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK.
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK
| | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK
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24
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Tangena JAA, Mategula D, Sedda L, Atkinson PM. Unravelling the impact of insecticide-treated bed nets on childhood malaria in Malawi. Malar J 2023; 22:16. [PMID: 36635658 PMCID: PMC9837906 DOI: 10.1186/s12936-023-04448-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 01/06/2023] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND To achieve malaria elimination it is essential to understand the impact of insecticide-treated net (ITNs) programmes. Here, the impact of ITN access and use on malaria prevalence in children in Malawi was investigated using Malaria Indicator Survey (MIS) data. METHODS MIS data from 2012, 2014 and 2017 were used to investigate the relationship between malaria prevalence in children (6-59 months) and ITN use. Generalized linear modelling (GLM), geostatistical mixed regression modelling and non-stationary GLM were undertaken to evaluate trends, spatial patterns and local dynamics, respectively. RESULTS Malaria prevalence in Malawi was 27.1% (95% CI 23.1-31.2%) in 2012 and similar in both 2014 (32.1%, 95% CI 25.5-38.7) and 2017 (23.9%, 95% CI 20.3-27.4%). ITN coverage and use increased during the same time period, with household ITN access growing from 19.0% (95% CI 15.6-22.3%) of households with at least 1 ITN for every 2 people sleeping in the house the night before to 41.7% (95% CI 39.1-44.4%) and ITN use from 41.1% (95% CI 37.3-44.9%) of the population sleeping under an ITN the previous night to 57.4% (95% CI 55.0-59.9%). Both the geostatistical and non-stationary GLM regression models showed child malaria prevalence had a negative association with ITN population access and a positive association with ITN use although affected by large uncertainties. The non-stationary GLM highlighted the spatital heterogeneity in the relationship between childhood malaria and ITN dynamics across the country. CONCLUSION Malaria prevalence in children under five had a negative association with ITN population access and a positive association with ITN use, with spatial heterogeneity in these relationships across Malawi. This study presents an important modelling approach that allows malaria control programmes to spatially disentangle the impact of interventions on malaria cases.
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Affiliation(s)
- Julie-Anne A. Tangena
- grid.48004.380000 0004 1936 9764Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Donnie Mategula
- grid.48004.380000 0004 1936 9764Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK ,grid.419393.50000 0004 8340 2442Malawi-Liverpool Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Luigi Sedda
- grid.9835.70000 0000 8190 6402Lancaster Ecology and Epidemiology Group, Lancaster University, Lancaster, UK
| | - Peter M. Atkinson
- grid.9835.70000 0000 8190 6402Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster, LA1 4YR UK ,grid.5491.90000 0004 1936 9297Geography and Environmental Science, University of Southampton, Highfield, Southampton, SO17 1BJ UK ,grid.9227.e0000000119573309Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A Datun Road, Beijing, 100101 China
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Burton TA, Kabinga LH, Simubali L, Hayre Q, Moore SJ, Stevenson JC, Lobo NF. Semi-field evaluation of a volatile transfluthrin-based intervention reveals efficacy as a spatial repellent and evidence of other modes of action. PLoS One 2023; 18:e0285501. [PMID: 37167335 PMCID: PMC10174509 DOI: 10.1371/journal.pone.0285501] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 04/25/2023] [Indexed: 05/13/2023] Open
Abstract
Presently, the most common malaria control tools-i.e., long lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS)-are limited to targeting indoor biting and resting behaviors of Anopheles mosquito species. Few interventions are targeted towards malaria control in areas where transmission is driven or persists due to outdoor biting behaviors. This study investigated a volatile pyrethroid-based spatial repellent (VPSR) designed to bridge this gap and provide protection from mosquito bites in outdoor spaces. Southern Province, Zambia, is one such environment where outdoor biting is suspected to contribute to malaria transmission, where people are active in the evening in open-walled outdoor kitchens. This study assessed the VPSR in replica kitchens within a controlled semi-field environment. Endpoints included effects on mosquito host seeking, immediate and delayed mortality, deterrence, blood feeding inhibition, and fertility. Host-seeking was reduced by approximately 40% over the course of nightly releases in chambers containing VPSR devices. Mosquito behavior was not uniform throughout the night, and the modeled effect of the intervention was considerably higher when hourly catch rates were considered. These two observations highlight a limitation of this overnight semi-field design and consideration of mosquito circadian rhythms is recommended for future semi-field studies. Additionally, deterrence and immediate mortality were both observed in treatment chambers, with evidence of delayed mortality and a dose related response. These results demonstrate a primarily personal protective mode of action with possible positive and negative community effects. Further investigation into this primary mode of action will be conducted through a field trial of the same product in nearby communities.
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Affiliation(s)
- Timothy A Burton
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | | | | | - Quinton Hayre
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Sarah J Moore
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, Bagamoyo, Tanzania
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Basel, Switzerland
- Faculty of Science, University of Basel, Basel, Switzerland
- The Nelson Mandela African Institution of Science and Technology (NM-AIST), Tengeru, Arusha, Tanzania
| | - Jennifer C Stevenson
- Macha Research Trust, Choma, Choma District, Zambia
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States of America
| | - Neil F Lobo
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
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Ngonghala CN. Assessing the impact of insecticide-treated nets in the face of insecticide resistance on malaria control. J Theor Biol 2022; 555:111281. [PMID: 36154815 DOI: 10.1016/j.jtbi.2022.111281] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 09/01/2022] [Accepted: 09/17/2022] [Indexed: 01/14/2023]
Abstract
The mosquito-borne disease, malaria, continues to impose a devastating health and economic burden worldwide. In malaria-endemic areas, insecticide-treated nets (ITNs) have been useful in curtailing the burden of the disease. However, mosquito resistance to insecticides, decay in ITN efficacy, net attrition, etc., undermine the effectiveness of ITNs in combatting malaria. In this study, mathematical models that account for asymptomatic infectious humans (through a partially immune class or a separate asymptomatic infectious class), insecticide resistance, and decay in ITN efficacy are proposed and analyzed. Analytical and numerical results of the models when ITN efficacy is constant show that there are parameter regimes for which a backward bifurcation occurs. Local and global sensitivity analyses are performed to identify parameters (some of which are potential targets for disease control) with the most significant influence on the control reproduction (Rc) and disease prevalence. These influential parameters include the maximum biting rate of resistant mosquitoes, ITN coverage, initial ITN efficacy against sensitive mosquitoes, the probability that an infectious mosquito (human) infects a susceptible human (mosquito), and the rate at which adult mosquitoes develop (lose) resistance to insecticides. Simulations of the models show that accounting for asymptomatic infectious humans through a separate class, or not accounting for the decay in ITN efficacy leads to an underestimation of disease burden. In particular, if the initial efficacy of ITNs against sensitive and resistance mosquitoes is 96%, the minimum ITN coverage required to reduce Rc below one (and hence, contain malaria) is approximately 11% (27%) lower when ITN efficacy is averaged (constant) for a model with a separate asymptomatic class. For the model with a partially immune class and decaying ITN efficacy, reducing Rc below one is impossible even if the entire populace uses ITNs. The study shows that replacing ITNs before their prescribed lifespans, or designing ITNs with longer lifespans is important for malaria control. Furthermore, the study shows that piperonyl butoxide (PBO) ITNs (which inhibit or reverse insecticide resistance) outperform regular ITNs in malaria control. Hence, prospects for effectively controlling malaria are enhanced by widespread use of high quality ITNs (e.g. PBO ITNs), especially if the useful lifespans of the ITNs are long enough and the ITNs are replaced before the end of their useful lifespans.
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Affiliation(s)
- Calistus N Ngonghala
- Department of Mathematics, University of Florida, 1400 Stadium Rd, Gainesville, FL 32611, United States of America; Emerging Pathogens Institute, University of Florida, 2055 Mowry Rd, Gainesville, FL 32610, United States of America; Center for African Studies, University of Florida, 427 Grinter Hall 1523 Union Rd, Gainesville, FL 32611, United States of America.
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Soumaila H, Hamani B, Arzika II, Soumana A, Daouda A, Daouda FA, Iro SM, Gouro S, Zaman-Allah MS, Mahamadou I, Kadri S, Salé NM, Hounkanrin W, Mahamadou B, Zamaka HN, Labbo R, Laminou IM, Jackou H, Idrissa S, Coulibaly E, Bahari-Tohon Z, Mathieu E, Carlson J, Dotson E, Awolola TS, Flatley C, Chabi J. Countrywide insecticide resistance monitoring and first report of the presence of the L1014S knock down resistance in Niger, West Africa. Malar J 2022; 21:385. [PMID: 36522727 PMCID: PMC9756763 DOI: 10.1186/s12936-022-04410-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Mass distribution of insecticide-treated nets (ITNs) is the principal malaria vector control strategy adopted by Niger. To better inform on the most appropriate ITN to distribute, the National Malaria Control Programme (NMCP) of Niger and its partners, conducted insecticide resistance monitoring in selected sites across the country. METHODS The susceptibility of Anopheles gambiae sensu lato (s.l.) to chlorfenapyr and pyrethroid insecticides was investigated in a total of sixteen sites in 2019 and 2020, using 2-5-day-old adults reared from wild collected larvae per site. The susceptibility status, pyrethroid resistance intensity at 5 and 10 times the diagnostic concentrations, and piperonyl butoxide (PBO) synergism with diagnostic concentrations of deltamethrin, permethrin and alpha-cypermethrin were assessed using WHO bioassays. Two doses (100 and 200 µg/bottle) of chlorfenapyr were tested using the CDC bottle assay method. Species composition and allele frequencies for knock-down resistance (kdr-L1014F and L1014S) and acetylcholinesterase (ace-1 G119S) mutations were further characterized using polymerase chain reaction (PCR). RESULTS High resistance intensity to all pyrethroids tested was observed in all sites except for alpha-cypermethrin in Gaya and Tessaoua and permethrin in Gaya in 2019 recording moderate resistance intensity. Similarly, Balleyara, Keita and Tillabery yielded moderate resistance intensity for alpha-cypermethrin and deltamethrin, and Niamey V low resistance intensity against deltamethrin and permethrin in 2020. Pre-exposure to PBO substantially increased susceptibility with average increases in mortality between 0 and 70% for tested pyrethroids. Susceptibility to chlorfenapyr (100 µg/bottle) was recorded in all sites except in Tessaoua and Magaria where susceptibility was recorded at the dose of 200 µg/bottle. Anopheles coluzzii was the predominant malaria vector species in most of the sites followed by An. gambiae sensu stricto (s.s.) and Anopheles arabiensis. The kdr-L1014S allele, investigated for the first time, was detected in the country. Both kdr-L1014F (frequencies [0.46-0.81]) and L1014S (frequencies [0.41-0.87]) were present in all sites while the ace-1 G119S was between 0.08 and 0.20. CONCLUSION The data collected will guide the NMCP in making evidence-based decisions to better adapt vector control strategies and insecticide resistance management in Niger, starting with mass distribution of new generation ITNs such as interceptor G2 and PBO ITNs.
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Affiliation(s)
| | - Boubé Hamani
- National Malaria Control Programme, Niamey, Niger
| | | | - Amadou Soumana
- grid.452260.7Centre de Recherche Médicale et Sanitaire, Niamey, Niger
| | | | | | | | - Samira Gouro
- National Malaria Control Programme, Niamey, Niger
| | | | - Izamné Mahamadou
- grid.452260.7Centre de Recherche Médicale et Sanitaire, Niamey, Niger
| | - Saadou Kadri
- grid.452260.7Centre de Recherche Médicale et Sanitaire, Niamey, Niger
| | - Noura Maman Salé
- grid.452260.7Centre de Recherche Médicale et Sanitaire, Niamey, Niger
| | | | | | | | - Rabiou Labbo
- grid.452260.7Centre de Recherche Médicale et Sanitaire, Niamey, Niger
| | | | | | | | - Eric Coulibaly
- U.S. President’s Malaria Initiative, USAID, Niamey, Niger
| | | | - Els Mathieu
- U.S. President’s Malaria Initiative, USAID, Niamey, Niger ,grid.416738.f0000 0001 2163 0069U.S. Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Jenny Carlson
- grid.507606.2Entomology Branch, U.S. President’s Malaria Initiative, Atlanta, GA USA
| | - Ellen Dotson
- grid.416738.f0000 0001 2163 0069U.S. Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Taiwo Samson Awolola
- grid.416738.f0000 0001 2163 0069U.S. Centers for Disease Control and Prevention, Atlanta, GA USA
| | | | - Joseph Chabi
- grid.507606.2PMI VectorLink Project, Washington, DC USA
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Meier CJ, Rouhier MF, Hillyer JF. Chemical Control of Mosquitoes and the Pesticide Treadmill: A Case for Photosensitive Insecticides as Larvicides. INSECTS 2022; 13:1093. [PMID: 36555003 PMCID: PMC9783766 DOI: 10.3390/insects13121093] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/18/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
Insecticides reduce the spread of mosquito-borne disease. Over the past century, mosquito control has mostly relied on neurotoxic chemicals-such as pyrethroids, neonicotinoids, chlorinated hydrocarbons, carbamates and organophosphates-that target adults. However, their persistent use has selected for insecticide resistance. This has led to the application of progressively higher amounts of insecticides-known as the pesticide treadmill-and negative consequences for ecosystems. Comparatively less attention has been paid to larvae, even though larval death eliminates a mosquito's potential to transmit disease and reproduce. Larvae have been targeted by source reduction, biological control, growth regulators and neurotoxins, but hurdles remain. Here, we review methods of mosquito control and argue that photoactive molecules that target larvae-called photosensitive insecticides or PSIs-are an environmentally friendly addition to our mosquitocidal arsenal. PSIs are ingested by larvae and produce reactive oxygen species (ROS) when activated by light. ROS then damage macromolecules resulting in larval death. PSIs are degraded by light, eliminating environmental accumulation. Moreover, PSIs only harm small translucent organisms, and their broad mechanism of action that relies on oxidative damage means that resistance is less likely to evolve. Therefore, PSIs are a promising alternative for controlling mosquitoes in an environmentally sustainable manner.
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Affiliation(s)
- Cole J. Meier
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
| | | | - Julián F. Hillyer
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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Balboné M, Sawadogo I, Soma DD, Drabo SF, Namountougou M, Bayili K, Romba R, Meda GB, Nebié HCR, Dabire RK, Bassolé IHN, Gnankine O. Essential oils of plants and their combinations as an alternative adulticides against Anopheles gambiae (Diptera: Culicidae) populations. Sci Rep 2022; 12:19077. [PMID: 36352066 PMCID: PMC9646863 DOI: 10.1038/s41598-022-23554-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 11/02/2022] [Indexed: 11/11/2022] Open
Abstract
The persistence of malaria and the increasing of resistance of Anopheles gambiae species to chemicals remain major public health concerns in sub-Saharan Africa. Faced to these concerns, the search for alternative vector control strategies as use of essential oils (EOs) need to be implemented. Here, the five EOs from Cymbopogon citratus, Cymbopogon nardus, Eucalyptus camaldulensis, Lippia multiflora, Ocimum americanum obtained by hydro distillation were tested according to World Health Organization procedures on An. gambiae "Kisumu" and field strains collected in "Vallée du Kou". Also, the binary combinations of C. nardus (Cn) and O. americanum (Oa) were examined. As results, among the EOs tested, L. multiflora was the most efficient on both An. gambiae strains regarding KDT50 (50% of mosquitoes knock down time) and KDT95 and rate of morality values. Our current study showed that C8 (Cn 80%: Oa 20%) and C9 (Cn 90%: Oa 10%), were the most toxic to An. gambiae strain "Vallée de Kou" (VK) with the mortality rates reaching 80.7 and 100% at 1% concentration, respectively. These two binary combinations shown a synergistic effect on the susceptible population. However, only C9 gave a synergistic effect on VK population. The bioactivity of the two EOs, C. nardus and O. americanum, was improved by the combinations at certain proportions. The resistance ratios of all EOs and of the combinations were low (< 5). The combinations of C. nardus and O. americanum EOs at 90: 10 ratio and to a lesser extent L. multiflora EO, could be used as alternative bio-insecticides against malaria vectors resistant to pyrethroids in vector control programmes.
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Affiliation(s)
- Mahamoudou Balboné
- Laboratoire d’Entomologie Fondamentale et Appliquée, Unité de Formation et de Recherche en Sciences de la Vie et de la Terre, Université Joseph KI-ZERBO, 03 BP 7021, Ouagadougou, Burkina Faso
| | - Ignace Sawadogo
- grid.433132.40000 0001 2165 6445Institut de Recherche en Sciences Appliquées et Technologies, 03 BP 7047, Ouagadougou, Burkina Faso
| | - Dieudonné Diloma Soma
- grid.418128.60000 0004 0564 1122Institut de Recherche en Sciences de la Santé/Centre Muraz, BP 545, Bobo-Dioulasso, Burkina Faso
| | - Samuel Fogné Drabo
- Laboratoire d’Entomologie Fondamentale et Appliquée, Unité de Formation et de Recherche en Sciences de la Vie et de la Terre, Université Joseph KI-ZERBO, 03 BP 7021, Ouagadougou, Burkina Faso
| | - Moussa Namountougou
- grid.418128.60000 0004 0564 1122Institut de Recherche en Sciences de la Santé/Centre Muraz, BP 545, Bobo-Dioulasso, Burkina Faso ,grid.442667.50000 0004 0474 2212Université Nazi Boni, 01 BP 1091, Bobo-Dioulasso, Burkina Faso
| | - Koama Bayili
- grid.418128.60000 0004 0564 1122Institut de Recherche en Sciences de la Santé/Centre Muraz, BP 545, Bobo-Dioulasso, Burkina Faso
| | - Rahim Romba
- Laboratoire d’Entomologie Fondamentale et Appliquée, Unité de Formation et de Recherche en Sciences de la Vie et de la Terre, Université Joseph KI-ZERBO, 03 BP 7021, Ouagadougou, Burkina Faso
| | - Georges Benson Meda
- grid.418128.60000 0004 0564 1122Institut de Recherche en Sciences de la Santé/Centre Muraz, BP 545, Bobo-Dioulasso, Burkina Faso
| | - Honorat Charles Roger Nebié
- grid.433132.40000 0001 2165 6445Institut de Recherche en Sciences Appliquées et Technologies, 03 BP 7047, Ouagadougou, Burkina Faso
| | - Roch K. Dabire
- grid.418128.60000 0004 0564 1122Institut de Recherche en Sciences de la Santé/Centre Muraz, BP 545, Bobo-Dioulasso, Burkina Faso
| | - Imaël H. N. Bassolé
- Laboratoire d’Entomologie Fondamentale et Appliquée, Unité de Formation et de Recherche en Sciences de la Vie et de la Terre, Université Joseph KI-ZERBO, 03 BP 7021, Ouagadougou, Burkina Faso
| | - Olivier Gnankine
- Laboratoire d’Entomologie Fondamentale et Appliquée, Unité de Formation et de Recherche en Sciences de la Vie et de la Terre, Université Joseph KI-ZERBO, 03 BP 7021, Ouagadougou, Burkina Faso
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Chanda-Kapata P, Ntoumi F, Kapata N, Lungu P, Mucheleng'anga LA, Chakaya J, Tembo J, Himwaze C, Ansumana R, Asogun D, Mfinanga S, Nyasulu P, Mwaba P, Yeboah-Manu D, Zumla A, Nachega JB. Tuberculosis, HIV/AIDS and Malaria Health Services in sub-Saharan Africa - A Situation Analysis of the Disruptions and Impact of the COVID-19 Pandemic. Int J Infect Dis 2022; 124 Suppl 1:S41-S46. [PMID: 35341998 PMCID: PMC8949686 DOI: 10.1016/j.ijid.2022.03.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The unprecedented and ongoing COVID-19 pandemic has exposed weaknesses in African countries' health systems. The impact of shifted focus on COVID-19 for the past 2 years on routine health services, especially those for the epidemics of Tuberculosis, HIV/AIDS and Malaria, have been dramatic in both quantity and quality. METHODS In this article, we reflect on the COVID-19 related disruptions on the Tuberculosis, HIV/AIDS and Malaria routine health services across Africa. RESULTS The COVID-19 pandemic resulted in disruptions of routine health services and diversion of already limited available resources in sub-Saharan Africa. As a result, disease programs like TB, malaria and HIV have recorded gaps in prevention and treatment with the prospects of reversing gains made towards meeting global targets. The extent of the disruption is yet to be fully quantified at country level as most data available is from modelling estimates before and during the pandemic. CONCLUSIONS Accurate country-level data is required to convince donors and governments to invest more into revamping these health services and help prepare for managing future pandemics without disruption of routine services. Increasing government expenditure on health is a critical part of Africa's economic policy. Strengthening health systems at various levels to overcome the negative impacts of COVID-19, and preparing for future epidemics will require strong visionary political leadership. Innovations in service delivery and technological adaptations are required as countries aim to limit disruptions to routine services.
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Affiliation(s)
| | - Francine Ntoumi
- Fondation Congolaise pour la Recherche Médicale (FCRM), Brazzaville, Republic of Congo; Institute for Tropical Medicine, University of Tübingen, Germany.
| | - Nathan Kapata
- National Public Health Institute, Ministry of Health, and UNZA-UCLMS Research and Training Program, Lusaka, Zambia.
| | - Patrick Lungu
- University of Zambia, School of Medicine, Department Internal Medicine, Lusaka, Zambia.
| | - Luchenga Adam Mucheleng'anga
- Ministry of Home Affairs, Office of the State Forensic Pathologist, and UNZA-UCLMS Research and Training Program, University Teaching Hospital, Lusaka, Zambia.
| | - Jeremiah Chakaya
- Department of Medicine, Therapeutics, Dermatology and Psychiatry, Kenyatta University, Nairobi, Kenya.
| | - John Tembo
- HERPEZ and UNZA-UCLMS Research and Training Program, University Teaching Hospital, Lusaka, Zambia.
| | - Cordelia Himwaze
- University Teaching Hospital, Department of Pathology and Microbiology; and UNZA-UCLMS Research and Training Program, University Teaching Hospital, Lusaka, Zambia.
| | - Rashid Ansumana
- Mercy Hospital Research Laboratory, Bo, Freetown, Sierra Leone.
| | - Danny Asogun
- Ambrose Alli University, Ekpoma and Irrua Specialist Teaching Hospital, Nigeria.
| | - Sayoki Mfinanga
- Muhimbili Medical Research Centre National Institute for Medical Research, Dar es Salaam, Tanzania.
| | - Peter Nyasulu
- Division of Epidemiology & Biostatistics, Faculty of Medicine; Health Sciences, Stellenbosch University, Cape Town, South Africa.
| | - Peter Mwaba
- Lusaka Apex Medical University, Faculty of Medicine, and UNZA-UCLMS Research and Training Project, Lusaka, Zambia.
| | - Dorothy Yeboah-Manu
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
| | - Alimuddin Zumla
- Center for Clinical Microbiology, Division of Infection and Immunity, University College London, and NIHR Biomedical Research Centre, UCL Hospitals NHS Foundation Trust, London, United Kingdom; UNZA-UCLMS Research and Training Program Program, Lusaka, Zambia.
| | - Jean B Nachega
- Department of Medicine and Division of Infectious Diseases, Stellenbosch University Faculty of Medicine and Health Sciences, Cape Town, South Africa; Depts of Epidemiology and International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA; Depts of Epidemiology, Infectious Diseases and Microbiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania, USA.
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Bio-efficacy, physical integrity, use and attrition of long-lasting insecticidal nets under operational conditions for malaria prevention in Ghana. PLoS One 2022; 17:e0275825. [PMID: 36240161 PMCID: PMC9565380 DOI: 10.1371/journal.pone.0275825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 09/23/2022] [Indexed: 11/05/2022] Open
Abstract
Background Malaria remains a public health challenge in endemic countries of the world. The use of Long-lasting Insecticidal Nets (LLINs) is one of the major ways of malaria vector control. Recent evidence however suggests some LLINs are unable to maintain their effectiveness over their useful life span. This study assessed the bio-efficacy, physical integrity, use and attrition at 6 and 12-months post-distribution of LLINs (LifeNet). Methods Following a mass distribution of LLINs in the West Mamprusi District of the North-East region of Ghana in 2018, a total of 147 LLINs were sampled for physical integrity and attrition assessment using hole size and the number of holes as a measure of the proportionate hole index (pHI). Bioassays were conducted on sixty randomly selected LLINs using the WHO guidelines for bio-efficacy testing (cone tests), (20 each at baseline, midline and endline) over a one-year study period. Bed net ownership and use as well as malaria vector resistance status were also assessed. Results Findings indicate high bio-efficacy of approximately 100% average mortalities of mosquitoes at baseline, 6-months and 12-months post-distribution. A small proportion of LLINs (0.8% and 5.6% at the 6 and 12-months surveys respectively) were damaged beyond maintenance while 62.4% and 62.7% of LLINs were used the night before the survey for 6 and 12-months post-distribution respectively. Households with electricity were less likely to use LLINs compared to those without electricity (P-value = 0.016, OR = 0.39). There were 20 fewer LLINs recovered at the 12-months relative to the 6-months resulting in 14.3% attrition rate. Susceptibility testing showed high pyrethroid and organochlorine resistance (18%, 67.5% and 3.8%) to local malaria vectors respectively), whereas organophosphates and carbamates recorded vector susceptibility of 100% for pirimiphos-methyl and 98.7% for bendiocarb. Conclusion Biological efficacy, physical integrity and net attrition during the study period were in conformity with respect to the WHOPES one year net use. LLINs remained effective after one-year of usage. Net ownership was high in the study households. There should be continuous and regular distribution campaigns to maintain high coverage.
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Likwela JL, Ngwala PL, Ntumba AK, Ntale DC, Sompwe EM, Mpiana GK, Tshula JK, Likwela TK, Kanku-Ka-Munabe P, Kumbi AN', Ndahambara GK, Ntale HC, Kiamenga ML, Njila JK, Yav GM, Baneti DG, Austin J. Digitalized long-lasting insecticidal nets mass distribution campaign in the context of Covid-19 pandemic in Kongo Central, Democratic Republic of Congo: challenges and lessons learned. Malar J 2022; 21:253. [PMID: 36050676 PMCID: PMC9434528 DOI: 10.1186/s12936-022-04258-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 08/09/2022] [Indexed: 11/20/2022] Open
Abstract
Background The Democratic Republic of the Congo (DRC) organized a first mass distribution campaign of long-lasting insecticidal nets (LLINs) with digitalized data management with coordinated support from the Ministry of Health (MOH) and Santé Pour Tous En Milieu Rural—an ‘Association sans but lucratif’ (SANRU Asbl), in the context of the Covid-19 pandemic in Kongo Central province. This article describes the planning and implementation process of this campaign as well as the challenges and lessons learned. Methods The planning and implementation process was performed in line with the standard guidance issued by the National Malaria Control Programme (NMCP) following the start of Covid-19. The changes and adaptations put in place as well as the challenges encountered are described. Results A total of 5,629,211 people were registered (7.7% above projection) in 1,065,537 households (6.2% below projection) giving an average of 5.3 people per household. Of a total of 3,062,850 LLINs ordered, 2,886,096 were distributed to households (94%). Out of 11,070 villages and 3,947 teams planned, 91.7% of villages were reached and 93% of teams were established. Conclusion The revision of standards of campaign implementation during Covid-19, as well as effective coordination supported by real-time decision-making through digital data management, have been factors in the success of this campaign. Maintaining this momentum is essential to ensure the continuity of malaria prevention services for the population.
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Affiliation(s)
- Joris Losimba Likwela
- University of Kisangani, Kisangani, Democratic Republic of the Congo. .,Sanru Asbl, Kinshasa, Democratic Republic of the Congo.
| | | | | | | | - Eric Mukomena Sompwe
- National Malaria Control Programme, Kinshasa, Democratic Republic of the Congo.,School of Public Health, University of Lubumbashi, Lubumbashi, Democratic Republic of the Congo
| | - Godé Kanyeba Mpiana
- National Malaria Control Programme, Kinshasa, Democratic Republic of the Congo
| | | | | | | | | | | | | | | | | | - Ghislain Makhan Yav
- Cellule d'Appui à la Gestion Financière, Ministère de la Santé, Kinshasa, Democratic Republic of the Congo
| | - Didier Gasigwa Baneti
- Cellule d'Appui à la Gestion Financière, Ministère de la Santé, Kinshasa, Democratic Republic of the Congo
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Nlinwe NO, Nchefor FG, Takwi NB. Impact of long lasting insecticidal nets on asymptomatic malaria during pregnancy, in a rural and urban setting in Cameroon. Parasite Epidemiol Control 2022; 18:e00265. [PMID: 35992014 PMCID: PMC9375851 DOI: 10.1016/j.parepi.2022.e00265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 07/04/2022] [Accepted: 08/09/2022] [Indexed: 11/16/2022] Open
Abstract
According to the world malaria report more malaria cases were reported in 2020 than in 2019, due to disruptions in the distribution of insecticide treated nets, caused by the COVID-19 pandemic. Consequently a projected 34.32% (11.6 million out of 33.8 million) pregnancies were exposed to malaria in the WHO African Region in 2020. This study was therefore designed to assess the impact of long lasting insecticidal nets (LLINs) on asymptomatic malaria in the pregnant women attending the Foumbot District Hospital (rural setting) and the Bamenda Regional Hospital (urban setting). This was a hospital based cross-sectional study done within three months from February to April 2021. A structured questionnaire and the CareStart™ Pf Malaria HRP2 qualitative rapid diagnostic test were used for data collection. Data were analysed using descriptive statistics, and Chi-square test. The relative risk, attributable risk, odds ratio, and likelihood ratio of malaria occurrence in exposed patients were determined by Chi-square (and Fisher's exact) test. The prevalence of asymptomatic malaria was 10.14% (63/621), with a higher prevalence among the pregnant women in the rural setting (12.21%; 37/303), than the urban setting (8.18%; 26/318). As indicated by the attributable risk, 21% of malaria incidence was attributed to absence of LLINs distribution in neighborhoods of the rural setting meanwhile 10% of malaria incidence is attributed to absence of LLINs distribution in neighborhoods of the urban setting. Regular screening for asymptomatic malaria in pregnancy and consistent free distribution of LLINs are recommended in endemic areas, especially in the rural settings.
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Park SK, Lee HJ, Song E, Jung Y, Yoo HJ, Oh JE, Shin HM, Kwon JH. Filling gaps between exposure modeling and the analysis of urinary biomarkers using personal air monitoring: An intervention study of permethrin used in home insecticide spray. INDOOR AIR 2022; 32:e13090. [PMID: 36040288 DOI: 10.1111/ina.13090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 06/17/2022] [Accepted: 07/23/2022] [Indexed: 06/15/2023]
Abstract
Permethrin is one of the most widely used active ingredients in spray-type home insecticides. However, indoor permethrin exposure resulting from the use of home insecticides is not well-characterized, as measured permethrin concentrations in indoor environmental and biological media with a known application rate are scarce. We conducted an intervention study with four participants for seven days. We conducted personal air monitoring and collected 24-h urine samples in which we quantified time-weighted average (TWA) permethrin concentrations in indoor air (Cair ) and urinary concentrations of two permethrin metabolites, 3-phenoxybenzoic acid (3-PBA) and cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis/trans-DCCA). We also estimated (1) TWA Cair using a simple indoor air model and (2) urinary excreted (UE) mass using a simple excretion model with both estimated and measured TWA Cair . Measurements of TWA Cair from personal air monitoring were lower than those estimated from the indoor model by a factor of 2.9 to 49.4. The ratio of estimated to measured UE mass ranged 3.5-18.2 when using estimated TWA Cair and 1.1-2.9 when using measured TWA Cair . Smaller ratios in estimating internal permethrin exposure from personal air monitoring suggest that personal air monitoring could reduce uncertainties in permethrin exposure assessment resulting from the use of spray-type insecticides.
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Affiliation(s)
- Seon-Kyung Park
- Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea
| | - Heon-Jun Lee
- Department of Environmental Engineering, Pusan National University, Busan, Republic of Korea
| | - Eugene Song
- Department of Consumer Science, Chungbuk National University, Chungbuk, Republic of Korea
| | - Yerin Jung
- Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea
- Department of Earth and Environmental Sciences, University of Texas at Arlington, Arlington, Texas, USA
| | - Hyun Jung Yoo
- Department of Consumer Science, Chungbuk National University, Chungbuk, Republic of Korea
| | - Jeong-Eun Oh
- Department of Environmental Engineering, Pusan National University, Busan, Republic of Korea
| | - Hyeong-Moo Shin
- Department of Environmental Science, Baylor University, Waco, Texas, USA
- Department of Environmental and Occupational Health, University of California, Irvine, CA, USA
| | - Jung-Hwan Kwon
- Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea
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Ngangue-Siewe IN, Ndjeunia-Mbiakop P, Kala-Chouakeu NA, Bamou R, Talipouo A, Djamouko-Djonkam L, Vontas J, Mavridis K, Tombi J, Tchuinkam T, Mbida-Mbida JA, Antonio-Nkondjio C. Bendiocarb and Malathion Resistance in Two Major Malaria Vector Populations in Cameroon Is Associated with High Frequency of the G119S Mutation (Ace-1) and Overexpression of Detoxification Genes. Pathogens 2022; 11:pathogens11080824. [PMID: 35894047 PMCID: PMC9330212 DOI: 10.3390/pathogens11080824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/19/2022] [Accepted: 07/21/2022] [Indexed: 12/10/2022] Open
Abstract
The spread of pyrethroid resistance in malaria vectors is a major threat affecting the performance of current control measures. However, there is still not enough information on the resistance profile of mosquitoes to carbamates and organophosphates which could be used as alternatives. The present study assessed the resistance profile of Anopheles gambiae s.l. to bendiocarb and malathion, at the phenotypic and molecular levels, in different eco-epidemiological settings in Cameroon. Anopheles gambiae s.l. mosquitoes were collected from four eco-epidemiological settings across the country and their susceptibility level to bendiocarb and malathion was determined using WHO tubes bioassays. The ace-1 target site G119S mutation was screened by PCR. Reverse Transcription quantitative PCR 3-plex TaqMan assays were used to quantify the level of expression of eight genes associated with metabolic resistance. Resistance to malathion and/or bendiocarb was recorded in all study sites except in mosquitoes collected in Kaélé and Njombé. The Ace-1 (G119S) mutation was detected in high frequencies (>40%) in Kékem and Santchou. Both An. gambiae and An. coluzzii were detected carrying this mutation. The cytochrome P450s gene Cyp6p3 associated with carbamate resistance and the glutathione S-transferase gene Gste2 associated with organophosphate resistance were found to be overexpressed. Genes associated with pyrethroid (Cyp6m2, Cyp9k1, Cyp6p3) and organochlorine (Gste2, Cyp6z1, Cyp6m2) and cuticle resistance (Cyp4g16) were also overexpressed. The rapid spread of resistance to organophosphates and carbamates could seriously compromise future control strategies based on IRS. It is therefore becoming important to assess the magnitude of bendiocarb and malathion resistance countrywide.
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Affiliation(s)
- Idriss Nasser Ngangue-Siewe
- Laboratory of Animal Biology and Physiology, University of Douala, Douala P.O. Box 24157, Cameroon; (I.N.N.-S.); (J.A.M.-M.)
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
| | - Paulette Ndjeunia-Mbiakop
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
- Faculty of Sciences, University of Yaoundé I, Yaoundé P.O. Box 812, Cameroon;
| | - Nelly Armanda Kala-Chouakeu
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
- Vector-Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang P.O. Box 067, Cameroon;
| | - Roland Bamou
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
- Vector-Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang P.O. Box 067, Cameroon;
| | - Abdou Talipouo
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
- Faculty of Sciences, University of Yaoundé I, Yaoundé P.O. Box 812, Cameroon;
| | - Landre Djamouko-Djonkam
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
- Vector-Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang P.O. Box 067, Cameroon;
| | - John Vontas
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Greece; (J.V.); (K.M.)
- Pesticide Science Laboratory, Department of Crop Science, Agricultural University of Athens, 11855 Athens, Greece
| | - Konstantinos Mavridis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Greece; (J.V.); (K.M.)
| | - Jeannette Tombi
- Faculty of Sciences, University of Yaoundé I, Yaoundé P.O. Box 812, Cameroon;
| | - Timoléon Tchuinkam
- Vector-Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang P.O. Box 067, Cameroon;
| | - Jean Arthur Mbida-Mbida
- Laboratory of Animal Biology and Physiology, University of Douala, Douala P.O. Box 24157, Cameroon; (I.N.N.-S.); (J.A.M.-M.)
| | - Christophe Antonio-Nkondjio
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Yaoundé P.O. Box 288, Cameroon; (P.N.-M.); (N.A.K.-C.); (R.B.); (A.T.); (L.D.-D.)
- Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
- Correspondence: ; Tel.: +237-699-53-86-56
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Inferring the epidemiological benefit of indoor vector control interventions against malaria from mosquito data. Nat Commun 2022; 13:3862. [PMID: 35790746 PMCID: PMC9256631 DOI: 10.1038/s41467-022-30700-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 05/11/2022] [Indexed: 12/03/2022] Open
Abstract
The cause of malaria transmission has been known for over a century but it is still unclear whether entomological measures are sufficiently reliable to inform policy decisions in human health. Decision-making on the effectiveness of new insecticide-treated nets (ITNs) and the indoor residual spraying of insecticide (IRS) have been based on epidemiological data, typically collected in cluster-randomised control trials. The number of these trials that can be conducted is limited. Here we use a systematic review to highlight that efficacy estimates of the same intervention may vary substantially between trials. Analyses indicate that mosquito data collected in experimental hut trials can be used to parameterize mechanistic models for Plasmodium falciparum malaria and reliably predict the epidemiological efficacy of quick-acting, neuro-acting ITNs and IRS. Results suggest that for certain types of ITNs and IRS using this framework instead of clinical endpoints could support policy and expedite the widespread use of novel technologies. Estimating the effectiveness of malaria vector control interventions has typically relied on resource-intensive cluster randomised trials. Here, the authors estimate changes in malaria prevalence using entomological data from experimental hut trials, which may provide an alternative route to approval of interventions in some situations.
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Hughes A, Matope A, Emery M, Steen K, Murray G, Ranson H, McCall PJ, Foster GM. A closer look at the WHO cone bioassay: video analysis of the hidden effects of a human host on mosquito behaviour and insecticide contact. Malar J 2022; 21:208. [PMID: 35778744 PMCID: PMC9248144 DOI: 10.1186/s12936-022-04232-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 06/20/2022] [Indexed: 12/04/2022] Open
Abstract
Background The WHO cone test is one of three tests currently used to evaluate the efficacy of insecticide-treated bed nets (ITNs). It generates two test outputs, knockdown and 24-h mortality, both indicative of immediate toxicity but that reveal little about the nature of mosquito and ITN interaction or how results translate to real-world settings. Methods A human arm held 5 mm behind the net surface acted as a host attractant during cone tests and a smartphone was used to capture mosquito behaviour in the cone. Post-exposure blood feeding and survival for nine days were recorded; ingested blood meal size was determined by measuring excreted haematin. Four strains of Anopheles gambiae (insecticide susceptible: Kisumu and N’gousso; insecticide resistant: Banfora and VK7) were tested with and without the host attractant using untreated, Permanet 2.0 and Olyset nets. Video recordings were scan sampled every five seconds to record mosquito positions on either the net, in flight or in contact with the cone. Generalized estimating equations were used to analyse all data except survival within nine days which was analysed using Weighted Cox Regression. Results Net contact was the most frequently recorded behaviour in all Anopheles spp. strains on all nets. Adding the human host as attractant triggered excitatory behaviours: in all strains, the magnitude of net contact was significantly decreased compared to tests without a host. ITN exposure altered the observed behaviour of the two susceptible strains, which exhibited a decreased response to the host during ITN tests. The resistant strains did not alter their behaviour during ITN tests. Significantly less net contact was observed during Olyset Net tests compared to Permanet 2.0. The host presence affected survival after exposure: Banfora and VK7 mosquitoes exposed to Permanet 2.0 with a host lived longer compared to tests performed without a host. However, mosquitoes that blood-fed and survived long enough to digest the blood meal did not exhibit significantly reduced longevity regardless of the presence of the host attractant. Conclusions Simple modifications to the WHO cone test and extension of post-test monitoring beyond the current 24 h enable detailed behavioural characterizations of individual ITNs to be compiled. The effects observed from testing with a host and including blood feeding suggest that more representative estimates of true of ITN efficacy are gained with these modifications than when using the current testing protocol. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04232-4.
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Affiliation(s)
- Angela Hughes
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Agnes Matope
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Mischa Emery
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Keith Steen
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Gregory Murray
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Philip J McCall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Geraldine M Foster
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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Ngongang-Yipmo ES, Tchouakui M, Menze BD, Mugenzi LMJ, Njiokou F, Wondji CS. Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon. Parasit Vectors 2022; 15:230. [PMID: 35754045 PMCID: PMC9233849 DOI: 10.1186/s13071-022-05335-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/23/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are a vital tool in the fight against malaria vectors. However, their efficacy in the field can be impacted by several factors, including patterns of usage, net age, mosquito resistance and the delayed mortality effect, all of which could influence malaria transmission. We have investigated the effectiveness of the various brands of LLINs available in markets and households in Cameroon on pyrethroid-resistant mosquitoes and assessed their post-exposure effect. METHODS Following quality control assessment on a susceptible laboratory mosquito strain, we evaluated the immediate and delayed mortality effects of exposure to LLINs (both newly bough LLINst and used ones collected from households in Elende village, Cameroon, in 2019) using standard WHO cone tests on Anopheles gambiae and Anopheles funestus populations collected from the Centre region of Cameroon. Alive female mosquitoes were genotyped for various resistance markers at different time points post-exposure to evaluate the impact of insecticide resistance on the efficacy of bednets. RESULTS The laboratory-susceptible strain experienced high mortality rates when exposed to all pyrethroid-only brands of purchased nets (Olyset® Net, Super Net, PermaNet® 2.0, Yorkool®, Royal Sentry®) (Mean±SEM: 68.66 ± 8.35% to 93.33 ± 2.90%). However, low mortality was observed among wild An. funestus mosquitoes exposed to the bednets (0 ± 0 to 28 ± 6.7%), indicating a reduced performance of these nets against field mosquitoes. Bednets collected from households also showed reduced efficacy on the laboratory strain (mortality: 19-66%), as well as displaying a significant loss of efficacy against the local wild strains (mortality: 0 ± 0% to 4 ± 2.6% for An. gambiae sensu lato and 0 ± 0% to 8 ± 3.2% for An. funestus). However, compared to the unexposed group, mosquitoes exposed to bednets showed a significantly reduced longevity, indicating that the efficacy of these nets was not completely lost. Mosquitoes with the CYP6P9a-RR and L119F-GSTe2 mutations conferring pyrethroid resistance showed greater longevity after exposure to the Olyset net than their susceptible counterparts, indicating the impact of resistance on bednet efficacy and delayed mortality. CONCLUSION These findings show that although standard bednets drastically lose their efficacy against pyrethroid-resistant field mosquitoes, they still are able to induce delayed mortality in exposed populations. The results of this study also provide evidence of the actual impact of resistance on the quality and efficacy of LLINs in use in the community, with mosquitoes carrying the CYP6P9a-RR and L119F-GSTe2 mutations conferring pyrethroid resistance living longer than their susceptible counterparts. These results highlight the need to use new-generation nets that do not rely solely on pyrethroids.
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Affiliation(s)
- Emilie S. Ngongang-Yipmo
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Magellan Tchouakui
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Benjamin D. Menze
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L35QA UK
| | - Leon M. J. Mugenzi
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Flobert Njiokou
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Charles S. Wondji
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L35QA UK
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Kahamba NF, Finda M, Ngowo HS, Msugupakulya BJ, Baldini F, Koekemoer LL, Ferguson HM, Okumu FO. Using ecological observations to improve malaria control in areas where Anopheles funestus is the dominant vector. Malar J 2022; 21:158. [PMID: 35655190 PMCID: PMC9161514 DOI: 10.1186/s12936-022-04198-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 05/19/2022] [Indexed: 11/10/2022] Open
Abstract
The most important malaria vectors in sub-Saharan Africa are Anopheles gambiae, Anopheles arabiensis, Anopheles funestus, and Anopheles coluzzii. Of these, An. funestus presently dominates in many settings in east and southern Africa. While research on this vector species has been impeded by difficulties in creating laboratory colonies, available evidence suggests it has certain ecological vulnerabilities that could be strategically exploited to greatly reduce malaria transmission in areas where it dominates. This paper examines the major life-history traits of An. funestus, its aquatic and adult ecologies, and its responsiveness to key interventions. It then outlines a plausible strategy for reducing malaria transmission by the vector and sustaining the gains over the medium to long term. To illustrate the propositions, the article uses data from south-eastern Tanzania where An. funestus mediates over 85% of malaria transmission events and is highly resistant to key public health insecticides, notably pyrethroids. Both male and female An. funestus rest indoors and the females frequently feed on humans indoors, although moderate to high degrees of zoophagy can occur in areas with large livestock populations. There are also a few reports of outdoor-biting by the species, highlighting a broader range of behavioural phenotypes that can be considered when designing new interventions to improve vector control. In comparison to other African malaria vectors, An. funestus distinctively prefers permanent and semi-permanent aquatic habitats, including river streams, ponds, swamps, and spring-fed pools. The species is therefore well-adapted to sustain its populations even during dry months and can support year-round malaria transmission. These ecological features suggest that highly effective control of An. funestus could be achieved primarily through strategic combinations of species-targeted larval source management and high quality insecticide-based methods targeting adult mosquitoes in shelters. If done consistently, such an integrated strategy has the potential to drastically reduce local populations of An. funestus and significantly reduce malaria transmission in areas where this vector species dominates. To sustain the gains, the programmes should be complemented with gradual environmental improvements such as house modification to maintain biting exposure at a bare minimum, as well as continuous engagements of the resident communities and other stakeholders.
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Affiliation(s)
- Najat F Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK.
| | - Marceline Finda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Betwel J Msugupakulya
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Francesco Baldini
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Heather M Ferguson
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK.
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa.
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania.
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Hamlet A, Dengela D, Tongren JE, Tadesse FG, Bousema T, Sinka M, Seyoum A, Irish SR, Armistead JS, Churcher T. The potential impact of Anopheles stephensi establishment on the transmission of Plasmodium falciparum in Ethiopia and prospective control measures. BMC Med 2022; 20:135. [PMID: 35440085 PMCID: PMC9020030 DOI: 10.1186/s12916-022-02324-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/07/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sub-Saharan Africa has seen substantial reductions in cases and deaths due to malaria over the past two decades. While this reduction is primarily due to an increasing expansion of interventions, urbanisation has played its part as urban areas typically experience substantially less malaria transmission than rural areas. However, this may be partially lost with the invasion and establishment of Anopheles stephensi. A. stephensi, the primary urban malaria vector in Asia, was first detected in Africa in 2012 in Djibouti and was subsequently identified in Ethiopia in 2016, and later in Sudan and Somalia. In Djibouti, malaria cases have increased 30-fold from 2012 to 2019 though the impact in the wider region remains unclear. METHODS Here, we have adapted an existing model of mechanistic malaria transmission to estimate the increase in vector density required to explain the trends in malaria cases seen in Djibouti. To account for the observed plasticity in An. stephensi behaviour, and the unknowns of how it will establish in a novel environment, we sample behavioural parameters in order to account for a wide range of uncertainty. This quantification is then applied to Ethiopia, considering temperature-dependent extrinsic incubation periods, pre-existing vector-control interventions and Plasmodium falciparum prevalence in order to assess the potential impact of An. stephensi establishment on P. falciparum transmission. Following this, we estimate the potential impact of scaling up ITN (insecticide-treated nets)/IRS (indoor residual spraying) and implementing piperonyl butoxide (PBO) ITNs and larval source management, as well as their economic costs. RESULTS We estimate that annual P. falciparum malaria cases could increase by 50% (95% CI 14-90) if no additional interventions are implemented. The implementation of sufficient control measures to reduce malaria transmission to pre-stephensi levels will cost hundreds of millions of USD. CONCLUSIONS Substantial heterogeneity across the country is predicted and large increases in vector control interventions could be needed to prevent a major public health emergency.
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Affiliation(s)
- Arran Hamlet
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK.
- The Abdul Latif Jameel Institute for Disease and Emergency Analytics, School of Public Health, Imperial College London, London, UK.
| | - Dereje Dengela
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD, 20852, USA
| | - J Eric Tongren
- U.S. President's Malaria Initiative (PMI), Addis Ababa, Ethiopia
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Fitsum G Tadesse
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Teun Bousema
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK
| | - Marianne Sinka
- Department of Zoology, University of Oxford, Oxford, OX1 3SZ, UK
| | - Aklilu Seyoum
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD, 20852, USA
| | - Seth R Irish
- U.S. President's Malaria Initiative, Entomology Branch Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Jennifer S Armistead
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Washington, D.C., USA
| | - Thomas Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
- The Abdul Latif Jameel Institute for Disease and Emergency Analytics, School of Public Health, Imperial College London, London, UK
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Opiyo M, Sherrard-Smith E, Malheia A, Nhacolo A, Sacoor C, Nhacolo A, Máquina M, Jamu L, Cuamba N, Bassat Q, Saúte F, Paaijmans K. Household modifications after the indoor residual spraying (IRS) campaign in Mozambique reduce the actual spray coverage and efficacy. PLOS GLOBAL PUBLIC HEALTH 2022; 2:e0000227. [PMID: 36962153 PMCID: PMC10021718 DOI: 10.1371/journal.pgph.0000227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 03/02/2022] [Indexed: 11/18/2022]
Abstract
Indoor residual spraying of insecticides (IRS) is a key malaria vector control strategy. Whilst human attitude towards IRS is monitored before or shortly after implementation, human activities leading to the modification of insecticide-treated walls post-IRS are not. This could inadvertently reduce the protective effects of IRS. We monitored the extent of modifications to the sprayed indoor wall surfaces by household owners for six months post-IRS campaigns in two districts targeted for malaria elimination in southern Mozambique. In parallel, we assessed building of any additional rooms onto compounds, and mosquito net use. We quantified the contribution of wall modifications, added rooms, prolonged spray campaigns, and product residual efficacies on actual IRS coverage and relative mosquito bite reduction, using a mechanistic approach. Household owners continually modified insecticide-treated walls and added rooms onto compounds. Household surveys in southern Mozambique showed frequent modification of indoor walls (0-17.2% of households modified rooms monthly) and/or added rooms (0-16.2% of households added rooms monthly). Actual IRS coverage reduced from an assumed 97% to just 39% in Matutuine, but only from 96% to 91% in Boane, translating to 43% and 5.8% estimated increases in relative daily mosquito bites per person. Integrating post-IRS knowledge, attitude, and practice (KAP) surveys into programmatic evaluations to capture these modification and construction trends can help improve IRS program efficiency and product assessment.
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Affiliation(s)
- Mercy Opiyo
- Barcelona Institute for Global Health (ISGlobal), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Arlindo Malheia
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Arsenio Nhacolo
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Charfudin Sacoor
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Ariel Nhacolo
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Mara Máquina
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Luis Jamu
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Nelson Cuamba
- National Malaria Control Programme of Mozambique (NMCP), Ministry of Health, Maputo, Mozambique
- PMI VectorLink Project, Abt Associates Inc., Maputo, Mozambique
| | - Quique Bassat
- Barcelona Institute for Global Health (ISGlobal), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
- ICREA, Barcelona, Spain
- Pediatrics Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Esplugues, Barcelona, Spain
- Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Francisco Saúte
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Krijn Paaijmans
- Barcelona Institute for Global Health (ISGlobal), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- The Biodesign Center for Immunotherapy, Vaccines, and Virotherapy, Arizona State University, Tempe, Arizona, United States of America
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, Arizona, United States of America
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Kibondo UA, Odufuwa OG, Ngonyani SH, Mpelepele AB, Matanilla I, Ngonyani H, Makungwa NO, Mseka AP, Swai K, Ntabaliba W, Stutz S, Austin JW, Moore SJ. Influence of testing modality on bioefficacy for the evaluation of Interceptor ® G2 mosquito nets to combat malaria mosquitoes in Tanzania. Parasit Vectors 2022; 15:124. [PMID: 35410250 PMCID: PMC8996609 DOI: 10.1186/s13071-022-05207-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 02/15/2022] [Indexed: 12/02/2022] Open
Abstract
Background Insecticide-treated net (ITN) durability is evaluated using longitudinal bioefficacy and fabric integrity sampling post-distribution. Interceptor® G2 was developed for resistance management and contains two adulticides: alpha-cypermethrin and chlorfenapyr; it is a pro-insecticide that is metabolized into its active form by mosquito-detoxifying enzymes and may be enhanced when the mosquito is physiologically active. To elucidate the impact of bioassay modality, mosquito exposures of the alphacypermethrin ITN Interceptor® and dual adulticide Interceptor® G2 were investigated. Methods This study evaluated the performance of Interceptor® G2 compared to Interceptor® against local strains of mosquitoes in Tanzania. Unwashed and 20× times washed nets were tested. Efficacy of ITNs was measured by four bioassay types: (1) World Health Organisation (WHO) cone test (cone), (2) WHO tunnel test (tunnel), (3) Ifakara ambient chamber test (I-ACT) and (4) the WHO gold standard experimental hut test (hut). Hut tests were conducted against free-flying wild pyrethroid metabolically resistant Anopheles arabiensis and Culex quinquefasciatus. Cone, tunnel and I-ACT bioassays used laboratory-reared metabolically resistant An. arabiensis and Cx. quinquefasciatus and pyrethroid susceptible Anopheles gambiae sensu stricto and Aedes aegypti. Results Against resistant strains, superiority of Interceptor® G2 over Interceptor® was observed in all “free-flying bioassays”. In cone tests (which restrict mosquito flight), superiority of Interceptor® over Interceptor® G2 was recorded. Mortality of unwashed Interceptor® G2 among An. arabiensis was lowest in hut tests at 42.9% (95% CI: 37.3–48.5), although this increased to 66.7% (95% CI: 47.1–86.3) by blocking hut exit traps so mosquitoes presumably increased frequencies of contact with ITNs. Higher odds of mortality were consistently observed in Interceptor® G2 compared to Interceptor® in “free-flying” bioassays using An. arabiensis: tunnel (OR = 1.42 [95% CI:1.19–1.70], p < 0.001), I-ACT (OR = 1.61 [95% CI: 1.05–2.49], p = 0.031) and hut (OR = 2.53 [95% CI: 1.96–3.26], p < 0.001). Interceptor® and Interceptor® G2 showed high blood-feeding inhibition against all strains. Conclusion Both free-flying laboratory bioassays (WHO Tunnel and I-ACT) consistently measured similarly, and both predicted the results of the experimental hut test. For bioefficacy monitoring and upstream product evaluation of ITNs in situ, the I-ACT may provide an alternative bioassay modality with improved statistical power. Interceptor G2® outperformed Interceptor ® against pyrethroid-resistant strains, demonstrating the usefulness of chlorfenapyr in mitigation of malaria. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05207-9.
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Affiliation(s)
- Ummi Abdul Kibondo
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
| | - Olukayode G Odufuwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.,MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, England
| | - Saphina H Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Ahmadi B Mpelepele
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Issaya Matanilla
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Hassan Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Noel O Makungwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Antony P Mseka
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Kyeba Swai
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
| | - Watson Ntabaliba
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Susanne Stutz
- Professional & Specialty Solutions, BASF SE, Public Health, 67117, Limburgerhof, Germany
| | - James W Austin
- Professional & Specialty Solutions, BASF Corporation, Public Health Global Development, Research Triangle Park, NC, 27709, USA
| | - Sarah Jane Moore
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.,University of Basel, Petersplatz 1, 4001, Basel, Switzerland.,Nelson Mandela African Institute of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Tanzania
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Barreaux P, Koella JC, N'Guessan R, Thomas MB. Use of novel lab assays to examine the effect of pyrethroid-treated bed nets on blood-feeding success and longevity of highly insecticide-resistant Anopheles gambiae s.l. mosquitoes. Parasit Vectors 2022; 15:111. [PMID: 35346334 PMCID: PMC8962112 DOI: 10.1186/s13071-022-05220-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 02/24/2022] [Indexed: 11/28/2022] Open
Abstract
Background There is a pressing need to improve understanding of how insecticide resistance affects the functional performance of insecticide-treated nets (ITNs). Standard WHO insecticide resistance monitoring assays are designed for resistance surveillance and do not necessarily provide insight into how different frequencies, mechanisms or intensities of resistance affect the ability of ITNs to reduce malaria transmission. Methods The current study presents some novel laboratory-based assays that attempt to better simulate realistic exposure of mosquitoes to ITNs and to quantify impact of exposure not only on instantaneous mortality, but also on blood-feeding and longevity, two traits that are central to transmission. The assays evaluated the performance of a standard ITN (Permanet® 2.0; Vestergaard Frandsen), a ‘next generation’ combination ITN with a resistance-breaking synergist (Permanet® 3.0) and an untreated net (UTN), against field-derived Anopheles gambiae sensu lato mosquitoes from Côte d’Ivoire exhibiting a 1500-fold increase in pyrethroid resistance relative to a standard susceptible strain. Results The study revealed that the standard ITN induced negligible instantaneous mortality against the resistant mosquitoes, whereas the resistance-breaking net caused high mortality and a reduction in blood-feeding. However, both ITNs still impacted long-term survival relative to the UTN. The impact on longevity depended on feeding status, with blood-fed mosquitoes living longer than unfed mosquitoes following ITN exposure. Exposure to both ITNs also reduced the blood-feeding success, the time spent on the net and blood-feeding duration, relative to the untreated net. Conclusion Although a standard ITN did not have as substantial instantaneous impact as the resistance-breaking net, it still had significant impacts on traits important for transmission. These results highlight the benefit of improved bioefficacy assays that allow for realistic exposure and consider sub- or pre-lethal effects to help assess the functional significance of insecticide resistance. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05220-y.
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Affiliation(s)
- Priscille Barreaux
- Liverpool School of Tropical Medicine, Liverpool, UK. .,Pennsylvania State University, State College, PA, USA. .,University of Neuchâtel, Neuchâtel, Switzerland.
| | | | - Raphael N'Guessan
- London School of Tropical Medicine, London, UK.,Vector Control Product Evaluation Centre, Institute Pierre Richet, Bouaké, Côte d'Ivoire
| | - Matthew B Thomas
- Pennsylvania State University, State College, PA, USA.,University of York, York, UK
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Madgwick PG, Kanitz R. Modelling new insecticide-treated bed nets for malaria-vector control: how to strategically manage resistance? Malar J 2022; 21:102. [PMID: 35331237 PMCID: PMC8944051 DOI: 10.1186/s12936-022-04083-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 02/11/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The program to eradicate malaria is at a critical juncture as a new wave of insecticides for mosquito control enter their final stages of development. Previous insecticides have been deployed one-at-a-time until their utility was compromised, without the strategic management of resistance. Recent investment has led to the near-synchronous development of new insecticides, and with it the current opportunity to build resistance management into mosquito-control methods to maximize the chance of eradicating malaria. METHODS Here, building on the parameter framework of an existing mathematical model, resistance-management strategies using multiple insecticides are compared to suggest how to deploy combinations of available and new insecticides on bed nets to achieve maximum impact. RESULTS Although results support the use of different strategies in different settings, deploying new insecticides ideally together in (or at least as a part of) a mixture is shown to be a robust strategy across most settings. CONCLUSIONS Substantially building on previous works, alternative solutions for the resistance management of new insecticides to be used in bed nets for malaria vector control are found. The results support a mixture product concept as the most robust way to deploy new insecticides, even if they are mixed with a pyrethroid that has lower effectiveness due to pre-existing resistance. This can help deciding on deployment strategies and policies around the sustainable use of these new anti-malaria tools.
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Affiliation(s)
- Philip G Madgwick
- Syngenta, Jealott's Hill International Research Centre, Bracknell, RG42 6EY, UK
| | - Ricardo Kanitz
- Syngenta Crop Protection, Rosentalstrasse 67, 4058, Basel, Switzerland.
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Rapid age-grading and species identification of natural mosquitoes for malaria surveillance. Nat Commun 2022; 13:1501. [PMID: 35314683 PMCID: PMC8938457 DOI: 10.1038/s41467-022-28980-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 02/19/2022] [Indexed: 12/03/2022] Open
Abstract
The malaria parasite, which is transmitted by several Anopheles mosquito species, requires more time to reach its human-transmissible stage than the average lifespan of mosquito vectors. Monitoring the species-specific age structure of mosquito populations is critical to evaluating the impact of vector control interventions on malaria risk. We present a rapid, cost-effective surveillance method based on deep learning of mid-infrared spectra of mosquito cuticle that simultaneously identifies the species and age class of three main malaria vectors in natural populations. Using spectra from over 40, 000 ecologically and genetically diverse An. gambiae, An. arabiensis, and An. coluzzii females, we develop a deep transfer learning model that learns and predicts the age of new wild populations in Tanzania and Burkina Faso with minimal sampling effort. Additionally, the model is able to detect the impact of simulated control interventions on mosquito populations, measured as a shift in their age structures. In the future, we anticipate our method can be applied to other arthropod vector-borne diseases. Knowing the age of malaria-transmitting mosquitoes is important to understand transmission risk as only old mosquitoes can transmit the disease. Here, the authors develop a method based on mid-infrared spectra of mosquito cuticle that can rapidly identify the species and age class of main malaria vectors.
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Martin JL, Messenger LA, Mosha FW, Lukole E, Mosha JF, Kulkarni M, Churcher TS, Sherrard-Smith E, Manjurano A, Protopopoff N, Rowland M. Durability of three types of dual active ingredient long-lasting insecticidal net compared to a pyrethroid-only LLIN in Tanzania: methodology for a prospective cohort study nested in a cluster randomized controlled trial. Malar J 2022; 21:96. [PMID: 35305667 PMCID: PMC8934498 DOI: 10.1186/s12936-022-04119-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 03/05/2022] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Progress achieved by long-lasting insecticidal nets (LLINs) against malaria is threatened by widespread selection of pyrethroid resistance among vector populations. LLINs with non-pyrethroid insecticides are urgently needed. This study aims to assess the insecticide and textile durability of three classes of dual-active ingredient (A.I.) LLINs using techniques derived from established WHO LLIN testing methods to set new standards of evaluation. METHODS A WHO Phase 3 active ingredients and textile durability study will be carried out within a cluster randomized controlled trial in 40 clusters in Misungwi district, Tanzania. The following treatments will be evaluated: (1) Interceptor®G2 combining chlorfenapyr and the pyrethroid alpha-cypermethrin, (2) Royal Guard® treated with pyriproxyfen and alpha-cypermethrin, (3) Olyset™ Plus which incorporates a synergist piperonyl butoxide and the pyrethroid permethrin, and (4) a reference standard alpha-cypermethrin only LLIN (Interceptor®). 750 nets will be followed in 5 clusters per intervention arm at 6, 12, 24 and 36 months post distribution for survivorship and hole index assessment. A second cohort of 1950 nets per net type will be identified in 10 clusters, of which 30 LLINs will be withdrawn for bio-efficacy and chemical analysis every 6 months up to 36 months and another 30 collected for experimental hut trials every year. Bio-efficacy will be assessed using cone bioassays and tunnel tests against susceptible and resistant laboratory strains of Anopheles gambiae sensu stricto. Efficacy of field-collected nets will be compared in six experimental huts. The main outcomes will be Anopheles mortality up to 72 h post exposure, blood feeding and egg maturation using ovary dissection to assess impact on fecundity. CONCLUSIONS Study findings will help develop bio-efficacy and physical durability criteria for partner A.I., in relation to the cRCT epidemiological and entomological outcomes, and refine preferred product characteristics of each class of LLIN. If suitable, the bioassay and hut outcomes will be fitted to transmission models to estimate correlation with cRCT outcomes. TRIAL REGISTRATION NUMBER NCT03554616.
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Affiliation(s)
- Jackline L. Martin
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | | | - Franklin W. Mosha
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
| | - Eliud Lukole
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | - Jacklin F. Mosha
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | | | | | | | - Alphaxard Manjurano
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | | | - Mark Rowland
- London School of Hygiene and Tropical, London, UK
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Runge M, Thawer SG, Molteni F, Chacky F, Mkude S, Mandike R, Snow RW, Lengeler C, Mohamed A, Pothin E. Sub-national tailoring of malaria interventions in Mainland Tanzania: simulation of the impact of strata-specific intervention combinations using modelling. Malar J 2022; 21:92. [PMID: 35300707 PMCID: PMC8929286 DOI: 10.1186/s12936-022-04099-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/23/2022] [Indexed: 11/21/2022] Open
Abstract
Background To accelerate progress against malaria in high burden countries, a strategic reorientation of resources at the sub-national level is needed. This paper describes how mathematical modelling was used in mainland Tanzania to support the strategic revision that followed the mid-term review of the 2015–2020 national malaria strategic plan (NMSP) and the epidemiological risk stratification at the council level in 2018. Methods Intervention mixes, selected by the National Malaria Control Programme, were simulated for each malaria risk strata per council. Intervention mixes included combinations of insecticide-treated bed nets (ITN), indoor residual spraying, larval source management, and intermittent preventive therapies for school children (IPTsc). Effective case management was either based on estimates from the malaria indicator survey in 2016 or set to a hypothetical target of 85%. A previously calibrated mathematical model in OpenMalaria was used to compare intervention impact predictions for prevalence and incidence between 2016 and 2020, or 2022. Results For each malaria risk stratum four to ten intervention mixes were explored. In the low-risk and urban strata, the scenario without a ITN mass campaign in 2019, predicted high increase in prevalence by 2020 and 2022, while in the very-low strata the target prevalence of less than 1% was maintained at low pre-intervention transmission intensity and high case management. In the moderate and high strata, IPTsc in addition to existing vector control was predicted to reduce the incidence by an additional 15% and prevalence by 22%. In the high-risk strata, all interventions together reached a maximum reduction of 76%, with around 70% of that reduction attributable to high case management and ITNs. Overall, the simulated revised NMSP was predicted to achieve a slightly lower prevalence in 2020 compared to the 2015–2020 NMSP (5.3% vs 6.3%). Conclusion Modelling supported the choice of intervention per malaria risk strata by providing impact comparisons of various alternative intervention mixes to address specific questions relevant to the country. The use of a council-calibrated model, that reproduces local malaria trends, represents a useful tool for compiling available evidence into a single analytical platform, that complement other evidence, to aid national programmes with decision-making processes. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04099-5.
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Affiliation(s)
- Manuela Runge
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Sumaiyya G Thawer
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Fabrizio Molteni
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Frank Chacky
- National Malaria Control Programme, Dodoma, Tanzania.,Ministry of Health, Community Development, Gender, Elderly, and Children, Dodoma, Tanzania
| | - Sigsbert Mkude
- National Malaria Control Programme, Dodoma, Tanzania.,Ministry of Health, Community Development, Gender, Elderly, and Children, Dodoma, Tanzania
| | - Renata Mandike
- National Malaria Control Programme, Dodoma, Tanzania.,Ministry of Health, Community Development, Gender, Elderly, and Children, Dodoma, Tanzania
| | - Robert W Snow
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.,Population Health Unit, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Christian Lengeler
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Ally Mohamed
- National Malaria Control Programme, Dodoma, Tanzania.,Ministry of Health, Community Development, Gender, Elderly, and Children, Dodoma, Tanzania
| | - Emilie Pothin
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland. .,CHAI, Clinton Health Access Initiative, New York, USA.
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Williams J, Cowlishaw R, Sanou A, Ranson H, Grigoraki L. In vivo functional validation of the V402L voltage gated sodium channel mutation in the malaria vector An. gambiae. PEST MANAGEMENT SCIENCE 2022; 78:1155-1163. [PMID: 34821465 DOI: 10.1002/ps.6731] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 11/19/2021] [Accepted: 11/25/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND Pyrethroids are the most widely used insecticides for the control of malaria transmitting Anopheles gambiae mosquitoes and rapid increase in resistance to this insecticide class is of major concern. Pyrethroids target the Voltage Gated Sodium Channels (VGSCs), that have a key role in the normal function of the mosquitoes' nervous system. VGSC mutations L995F and L995S have long been associated with pyrethroid resistance and screening for their presence is routine in insecticide resistance management programs. Recently, a VGSC haplotype containing two amino acid substitutions associated with resistance in other species, V402L and I1527T, was identified. These two VGSC mutations are found in tight linkage and are mutually exclusive to the classical L995F/S mutations. RESULTS We identify the presence of the V402L-I1527T haplotype in resistant An. coluzzii colonized strains and in field populations from Burkina Faso, at frequencies higher than previously reported; in some cases almost reaching fixation. Functional validation of V402L in insecticide resistance using a CRISPR/Cas9 genome modified line showed that it confers reduced mortality after exposure to all tested pyrethroids and DDT, but at lower levels compared to L995F. In contrast to L995F however, no fitness costs were identified for mosquitoes carrying V402L under laboratory conditions. CONCLUSION The V402L substitution confers pyrethroid resistance in An. gambiae in the absence of any other VGSC substitution and/or alternative resistance mechanisms. The lower fitness cost associated with this kdr mutation may provide a selective advantage over the classical kdr in some settings and genotyping at this locus should be added in the list of resistant alleles for routine screening.
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Affiliation(s)
- Jessica Williams
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Ruth Cowlishaw
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Antoine Sanou
- Service Scientifique et Technique, Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Hilary Ranson
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Linda Grigoraki
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
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Sherrard-Smith E, Winskill P, Hamlet A, Ngufor C, N'Guessan R, Guelbeogo MW, Sanou A, Nash RK, Hill A, Russell EL, Woodbridge M, Tungu P, Kont MD, Mclean T, Fornadel C, Richardson JH, Donnelly MJ, Staedke SG, Gonahasa S, Protopopoff N, Rowland M, Churcher TS. Optimising the deployment of vector control tools against malaria: a data-informed modelling study. Lancet Planet Health 2022; 6:e100-e109. [PMID: 35065707 DOI: 10.1016/s2542-5196(21)00296-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 10/28/2021] [Accepted: 10/29/2021] [Indexed: 05/10/2023]
Abstract
BACKGROUND Concern that insecticide resistant mosquitoes are threatening malaria control has driven the development of new types of insecticide treated nets (ITNs) and indoor residual spraying (IRS) of insecticide. Malaria control programmes have a choice of vector control interventions although it is unclear which controls should be used to combat the disease. The study aimed at producing a framework to easily compare the public health impact and cost-effectiveness of different malaria prevention measures currently in widespread use. METHODS We used published data from experimental hut trials conducted across Africa to characterise the entomological effect of pyrethroid-only ITNs versus ITNs combining a pyrethroid insecticide with the synergist piperonyl butoxide (PBO). We use these estimates to parameterise a dynamic mathematical model of Plasmodium falciparum malaria which is validated for two sites by comparing simulated results to empirical data from randomised control trials (RCTs) in Tanzania and Uganda. We extrapolated model simulations for a series of potential scenarios likely across the sub-Saharan African region and include results in an online tool (Malaria INtervention Tool [MINT]) that aims to identify optimum vector control intervention packages for scenarios with varying budget, price, entomological and epidemiological factors. FINDINGS Our model indicates that switching from pyrethroid-only to pyrethroid-PBO ITNs could averted up to twice as many cases, although the additional benefit is highly variable and depends on the setting conditions. We project that annual delivery of long-lasting, non-pyrethroid IRS would prevent substantially more cases over 3-years, while pyrethroid-PBO ITNs tend to be the most cost-effective intervention per case averted. The model was able to predict prevalence and efficacy against prevalence in both RCTs for the intervention types tested. MINT is applicable to regions of sub-Saharan Africa with endemic malaria and provides users with a method of designing intervention packages given their setting and budget. INTERPRETATION The most cost-effective vector control package will vary locally. Models able to recreate results of RCTs can be used to extrapolate outcomes elsewhere to support evidence-based decision making for investment in vector control. FUNDING Medical Research Council, IVCC, Wellcome Trust. TRANSLATION For the French translation of the abstract see Supplementary Materials section.
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Affiliation(s)
- Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK.
| | - Peter Winskill
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Arran Hamlet
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Corine Ngufor
- Centre de Recherches Entomologiques de Cotonou, Cotonou, Benin; London School of Hygiene and Tropical Medicine, London, UK
| | | | - Moussa W Guelbeogo
- Centre National de Recherche et de Formation sur le Paludisme, Burkina Faso
| | - Antoine Sanou
- Centre National de Recherche et de Formation sur le Paludisme, Burkina Faso
| | - Rebecca K Nash
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Alexander Hill
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Emma L Russell
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Mark Woodbridge
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Patrick Tungu
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Mara D Kont
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Tom Mclean
- Innovative Vector Control Consortium, Liverpool, UK
| | | | | | | | - Sarah G Staedke
- London School of Hygiene and Tropical Medicine, London, UK; Infectious Diseases Research Collaboration, Kampala, Uganda
| | | | | | - Mark Rowland
- London School of Hygiene and Tropical Medicine, London, UK
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
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50
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Yaro JB, Tiono AB, Ouedraogo A, Lambert B, Ouedraogo ZA, Diarra A, Traore A, Lankouande M, Soulama I, Sanou A, Worrall E, Agboraw E, Sagnon N, Ranson H, Churcher TS, Lindsay SW, Wilson AL. Risk of Plasmodium falciparum infection in south-west Burkina Faso: potential impact of expanding eligibility for seasonal malaria chemoprevention. Sci Rep 2022; 12:1402. [PMID: 35082312 PMCID: PMC8791962 DOI: 10.1038/s41598-022-05056-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 12/10/2021] [Indexed: 11/10/2022] Open
Abstract
Burkina Faso has one of the highest malaria burdens in sub-Saharan Africa despite the mass deployment of insecticide-treated nets (ITNs) and use of seasonal malaria chemoprevention (SMC) in children aged up to 5 years. Identification of risk factors for Plasmodium falciparum infection in rural Burkina Faso could help to identify and target malaria control measures. A cross-sectional survey of 1,199 children and adults was conducted during the peak malaria transmission season in the Cascades Region of south-west Burkina Faso in 2017. Logistic regression was used to identify risk factors for microscopically confirmed P. falciparum infection. A malaria transmission dynamic model was used to determine the impact on malaria cases averted of administering SMC to children aged 5-15 year old. P. falciparum prevalence was 32.8% in the study population. Children aged 5 to < 10 years old were at 3.74 times the odds (95% CI = 2.68-5.22, P < 0.001) and children aged 10 to 15 years old at 3.14 times the odds (95% CI = 1.20-8.21, P = 0.02) of P. falciparum infection compared to children aged less than 5 years old. Administration of SMC to children aged up to 10 years is predicted to avert an additional 57 malaria cases per 1000 population per year (9.4% reduction) and administration to children aged up to 15 years would avert an additional 89 malaria cases per 1000 population per year (14.6% reduction) in the Cascades Region, assuming current coverage of pyrethroid-piperonyl butoxide ITNs. Malaria infections were high in all age strata, although highest in children aged 5 to 15 years, despite roll out of core malaria control interventions. Given the burden of infection in school-age children, extension of the eligibility criteria for SMC could help reduce the burden of malaria in Burkina Faso and other countries in the region.
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Affiliation(s)
- Jean Baptiste Yaro
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
- Department of Biosciences, Durham University, Durham, UK
| | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Alphonse Ouedraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Ben Lambert
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Faculty of Medicine, Imperial College London, London, UK
| | - Z Amidou Ouedraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Amidou Diarra
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Adama Traore
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Malik Lankouande
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Issiaka Soulama
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
- Institut de Recherche en Sciences de la Santé, Ouagadougou, Burkina Faso
| | - Antoine Sanou
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
- Institute of Biodiversity, Animal Health & Comparative Medicine, Glasgow University, Glasgow, UK
| | - Eve Worrall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Efundem Agboraw
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - N'Fale Sagnon
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Faculty of Medicine, Imperial College London, London, UK
| | | | - Anne L Wilson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
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