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Obeagu EI, Obeagu GU. Adapting to the shifting landscape: Implications of climate change for malaria control: A review. Medicine (Baltimore) 2024; 103:e39010. [PMID: 39029063 PMCID: PMC11398779 DOI: 10.1097/md.0000000000039010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/21/2024] Open
Abstract
Malaria, a global public health challenge, continues to affect millions of lives, particularly in regions where its transmission is endemic. The interplay between climate change and malaria dynamics has emerged as a critical concern, reshaping the landscape of this vector-borne disease. This review publication, titled "Adapting to the shifting landscape: Implications of climate change for malaria control," explores the multifaceted relationship between climate change and the control of malaria. The paper begins by dissecting the influence of climate change on malaria dynamics, including alterations in temperature, precipitation, and other climatic factors that impact the habitat and life cycle of malaria vectors. It delves into the evolving ecology and behavior of malaria vectors in response to changing climatic conditions, emphasizing the importance of understanding these adaptations. As a response to this shifting landscape, the review discusses adaptive strategies for malaria control, ranging from vector control measures to the utilization of climate data in early warning systems. Community engagement and education are highlighted as essential components of these strategies, recognizing the vital role of local communities in effective malaria control efforts. The paper also identifies future directions and research needs, underscoring the importance of staying ahead of the evolving climate-malaria relationship. This review underscores the urgency of adapting to the changing landscape of malaria transmission driven by climate change. It emphasizes the significance of proactively addressing climate-related challenges to enhance malaria control and protect the health and well-being of vulnerable populations.
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Lukole EA, Cook J, Mosha JF, Mallya E, Aziz T, Kulkarni MA, Matowo NS, Martin J, Rowland M, Kleinschmidt I, Manjurano A, Mosha FW, Protopopoff N. Will a lack of fabric durability be their downfall? Impact of textile durability on the efficacy of three types of dual-active-ingredient long-lasting insecticidal nets: a secondary analysis on malaria prevalence and incidence from a cluster-randomized trial in north-west Tanzania. Malar J 2024; 23:199. [PMID: 38943155 PMCID: PMC11212245 DOI: 10.1186/s12936-024-05020-y] [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: 02/20/2024] [Accepted: 06/20/2024] [Indexed: 07/01/2024] Open
Abstract
BACKGROUND The Dual-Active Ingredient long-lasting insecticidal nets (Dual-AI LLIN) have been developed to counteract the reduced efficacy of pyrethroid (PY)-only nets due to widespread pyrethroid insecticide resistance in malaria vector mosquitoes. They constitute half of the nets distributed in sub-Saharan Africa between 2022 and 2024. However, their effectiveness once they develop holes is unclear, particularly in pyrethroid-resistant settings. This study evaluates the textile integrity of three dual- AI LLINs compared to standard PY LLN, over 3 years of use in a community in Tanzania and the associated impact on malaria prevalence and incidence. METHODS A secondary analysis of data from a randomized controlled trial (RCT) in North-western Tanzania was conducted to evaluate the effectiveness of α-cypermethrin only; pyriproxyfen and α-cypermethrin (PPF-PY); chlorfenapyr and α-cypermethrin (chlorfenapyr-PY); and the synergist piperonyl butoxide and permethrin (PBO-PY) LLINs on malaria infection prevalence and case incidence. The association between the net textile condition and 1/malaria prevalence over 3 years of use between 2019 and 2022, and 2/malaria case incidence in a cohort of children over 2 years of follow-up was assessed between 2019 and 2021. RESULTS There was no significant association between damaged (OR 0.98, 95% CI 0.71-1.37, p-value = 0.655) and too-torn (OR 1.07, 95% CI 0.77-1.47, p-value = 0.694) compared to intact nets on malaria prevalence for all net types. However, there were reduced rates of malaria case incidence in children sleeping under a net in good condition compared to too-torn nets (incidence rate ratio (IRR) 0.76 [95% CI 0.63-0.92], p = 0.005). Malaria incidence was also consistently lower in too-torn PBO-PY LLIN (IRR = 0.37 [95% CI 0.19-0.72], p = 0.003) and chlorfenapyr-PY LLIN (IRR = 0.45 [95% CI 0.33-0.97], p = 0.053) compared to an intact PY-only LLIN during the first year of follow up. In year 2, the incidence was only significantly lower in intact chlorfenapyr-PY LLIN (IRR = 0.49 [95% CI 0.29-0.81], p = 0.006) compared to intact PY LLIN. CONCLUSION The study confirmed that sleeping under a chlorfenapyr-PY LLIN or PBO-PY LLIN offered superior protection to pyrethroid-only nets even when torn. Preventing the development of holes is essential as they impact the level of protection offered against malaria infection. TRIAL REGISTRATION ClinicalTrials.gov, number (NCT03554616).
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Affiliation(s)
- Eliud Andrea Lukole
- Department of Parasitology, National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania.
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK.
| | - Jackie Cook
- Department of Infectious Disease Epidemiology, MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Jacklin F Mosha
- Department of Parasitology, National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Elizabeth Mallya
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Tatu Aziz
- Department of Parasitology, National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Manisha A Kulkarni
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
| | - Nancy S Matowo
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Jacklin Martin
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Immo Kleinschmidt
- Department of Infectious Disease Epidemiology, MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Southern African Development Community Malaria Elimination Eight Secretariat, Windhoek, Namibia
| | - Alphaxard Manjurano
- Department of Parasitology, National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Franklin W Mosha
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Natacha Protopopoff
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
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Ujuju CN, Mokuolu OA, Nwafor-Okoli C, Nnamani KO. Unravelling factors associated with malaria parasitaemia among children 6-24 months to inform malaria interventions in Nigeria: evidence from 2021 Malaria Indicator Survey. Malar J 2023; 22:247. [PMID: 37641100 PMCID: PMC10464367 DOI: 10.1186/s12936-023-04683-3] [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: 03/01/2023] [Accepted: 08/22/2023] [Indexed: 08/31/2023] Open
Abstract
BACKGROUND As an additional two million malaria cases were reported in 2021 compared to the previous year, concerted efforts toward achieving a steady decline in malaria cases are needed to achieve malaria elimination goals. This work aimed at determining the factors associated with malaria parasitaemia among children 6-24 months for better targeting of malaria interventions. METHODS A cross-sectional study analysed 2021 Nigeria Malaria Indicator Survey dataset. Data from 3058 children 6-24 months were analyzed. The outcome variable was children 6-24 months whose parasitaemia was determined using a rapid diagnostic test (RDT). Independent variables include child age in months, mothers' age, mothers' education, region, place of residence, household ownership and child use of insecticide-treated net (ITN), exposure to malaria messages and knowledge of ways to prevent malaria. Logistic regression analysis was conducted to examine possible factors associated with malaria parasitaemia in children 6-24 months. RESULTS Findings revealed that 28.7% of the 3058 children aged 6-24 months tested positive for malaria by RDT. About 63% of children 12-17 months (aOR = 1.63, 95% CI 1.31-2.03) and 91% of children 18 to 24 months (aOR = 1.91, 95% CI 1.51-2.42) were more likely to have a positive malaria test result. Positive malaria test result was also more likely in rural areas (aOR = 1.79, 95% CI 2.02-24.46), northeast (aOR = 1.54, 95% CI 1.02-2.31) and northwest (aOR = 1.63, 95% CI 1.10-2.40) region. In addition, about 39% of children who slept under ITN had a positive malaria test result (aOR = 1.39 95% CI 1.01-1.90). While children of mothers with secondary (aOR = 0.40, 95% CI 0.29-0.56) and higher (aOR = 0.26, 95% CI 0.16-0.43) levels of education and mothers who were aware of ways of avoiding malaria (aOR = 0.69, 95% CI 0.53-0.90) were less likely to have a malaria positive test result. CONCLUSION As older children 12 to 24 months, children residing in the rural, northeast, and northwest region are more likely to have malaria, additional intervention should target them in an effort to end malaria.
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Affiliation(s)
- Chinazo N Ujuju
- Research Department, Data for Decisions Nigeria Ltd, Abuja, Nigeria.
| | - Olugbenga A Mokuolu
- Centre for Malaria and Other Tropical Diseases Care, University of Ilorin Teaching Hospital, Ilorin, Nigeria
- Department of Paediatrics, College of Health Sciences, University of Ilorin, Ilorin, Nigeria
| | | | - Kenechi O Nnamani
- Department of Paediatrics, Nnamdi Azikiwe University Teaching Hospital Nnewi, Nnewi, Anambra State, Nigeria
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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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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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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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Mangani C, Mzilahowa T, Cohee L, Kayange M, Ntenda P, Sixpence A, Gumbo A, Lankhulani S, Goupeyou-Youmsi J, Walker E, Laufer M, Valim C, Seydel K, Wilson ML, Taylor T, Mathanga DP. Malawi ICEMR Malaria Research: Interactions and Results Influencing Health Policies and Practices. Am J Trop Med Hyg 2022; 107:49-54. [PMID: 36228911 PMCID: PMC9662217 DOI: 10.4269/ajtmh.21-1265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 05/14/2022] [Indexed: 01/29/2023] Open
Abstract
Malaria remains a threat to public health in Malawi. It is well acknowledged that malaria research and robust evidence can have an impact on malaria policy and practice, resulting in positive population health gains. We report policy-relevant research contributions that the Malawi International Center of Excellence for Malaria Research (ICEMR) in partnership with local and international collaborators has made. Findings from our ICEMR studies have shown that long-lasting insecticide-treated bed nets (LLINs) impregnated with piperonyl butoxide reduced mosquito blood feeding more compared with conventional LLINs. On the other hand, we showed that few LLINs are maintained up to the end of their 3-year life span, and that older nets are less effective. These results support the policy change decisions by the Malawi National Malaria Control Program to switch from conventional LLINs to piperonyl butoxide LLINs, and to conduct mass LLIN distribution campaigns every 2 years. Our studies on epidemiological patterns of malaria infection showed that school-age children have higher malaria infection rates and lower use of control measures compared with younger children and adults. These findings added to the evidence base that influenced the National Malaria Control Program to endorse school-based malaria interventions as part of its national policy. Research supported by the Malawi ICEMR is contributing to in-country policy decisions and to the implementation of evidence-based interventions. Through our long-term studies we intend to continue providing practical and policy-relevant evidence necessary, ultimately, to eliminate malaria infection in Malawi.
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Affiliation(s)
- Charles Mangani
- Department of Epidemiology and Biostatistics, School of Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi;,Address correspondence to Charles Mangani, Department of Epidemiology and Biostatistics, Kamuzu University of Health Sciences, P/Bag 360 Chichiri, Blantyre 3. E-mail:
| | - Themba Mzilahowa
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Lauren Cohee
- Department of Pediatrics, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Michael Kayange
- National Malaria Control Program, Ministry of Health, Lilongwe, Malawi
| | - Peter Ntenda
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Alick Sixpence
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Austin Gumbo
- National Malaria Control Program, Ministry of Health, Lilongwe, Malawi
| | - Sosten Lankhulani
- National Malaria Control Program, Ministry of Health, Lilongwe, Malawi
| | | | - Edward Walker
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan
| | - Miriam Laufer
- Department of Pediatrics, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Clarissa Valim
- Department of Global Health, Boston University School of Public Health, Boston, Massachusetts
| | - Karl Seydel
- Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan
| | - Mark L. Wilson
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, Michigan
| | - Terrie Taylor
- Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan
| | - Don P. Mathanga
- Department of Epidemiology and Biostatistics, School of Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi;,Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
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Sustainable Organic Farming, Food Safety and Pest Management: An Evolutionary Game Analysis. MATHEMATICS 2022. [DOI: 10.3390/math10132269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
There is an increasing realization that industrial, large-scale agriculture can negatively impact both food quality and the environment, and that alternatives should be thoroughly considered. Consisting of various participants with distinct and often competing interests, organic food chains have a dynamic structure. We consider an evolutionary game theory model for the dynamics of an organic supply chain with farmers, their customers and the government as the main stakeholders. After describing stakeholder strategies and constructing appropriate payoff matrices for the interactions between farmers and customers and between farmers and the government, respectively, sufficient conditions for the stability of the equilibria for the associated replicator equations were found. Those conditions were then interpreted in practical terms, the corresponding possible outcomes being determined and numerically illustrated. It was seen that a sustainable shift from a conventional strategy to an organic one requires the efforts of all involved stakeholders. As far as the evolutionary interaction between farmers and customers is concerned, it was seen that the purchasing power and the organic awareness of customers are of the utmost importance for the establishment and diffusion of organic strategies in the supply chain. Furthermore, a situation in which the preferences of farmers and consumers for an organic (or conventional) strategy change periodically may occur. Regarding the evolutionary interaction between farmers and the government, strong support for organic farmers is needed at first, and then the consumption habits and environmental awareness of the consumers can be cultivated. This promotes the establishment, development and enrichment of an organic supply chain which, at a certain point, can persist even without governmental subsidies.
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Alhassan Y, Dwomoh D, Amuasi SA, Nonvignon J, Bonful H, Tetteh M, Agyabeng K, Kotey M, Yawson AE, Bosomprah S. Impact of insecticide-treated nets and indoor residual spraying on self-reported malaria prevalence among women of reproductive age in Ghana: implication for malaria control and elimination. Malar J 2022; 21:120. [PMID: 35413832 PMCID: PMC9003985 DOI: 10.1186/s12936-022-04136-3] [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: 10/15/2021] [Accepted: 03/22/2022] [Indexed: 11/10/2022] Open
Abstract
Background The Global Fund alone contributed 56% of all international financing for malaria and has invested more than US$13.5 billion in malaria treatment, prevention, and control programmes by June 2021. These investments include interventions such as mosquito nets, indoor residual spraying, and preventive treatment for children and pregnant women. However, there is paucity of studies for assessment of such investments to a reduction in malaria prevalence. This study was aimed at quantifying the impact of household access to insecticide-treated nets (ITNs) and the indoor residual spraying (IRS) on self-reported malaria prevalence among women of reproductive age in Ghana. Methods The study analysed the 2016 Ghana Malaria Indicator Survey (MIS) data. The MIS is a nationwide survey that included women aged 15–49 years. Poisson regression model with inverse probability to treatment weighting was used to determine average treatment effect estimate of the two malaria interventions on self-reported malaria prevalence among women of reproductive age in Ghana. Results A total sample of 4861 women interviewed from the 2016 Ghana MIS was used for analysis. The prevalence of self-reported malaria in 2016 was 34.4% (95% CI [32.4%, 36.4%]). Approximately 80.0% of women lived in households with access to ITNs [Percentage (Pr) = 79.9%, (95% CI [78.0%, 81.7%])], 12.4% (95% CI [7.5%, 19.8%]) of the households had access to IRS and 11.4% (95% CI [7.0%, 18.0%]) of the households had access to both ITNs and IRS. Household access to only ITN contributed to 7.1 percentage point (pt) reduction in the self-reported malaria among women (95% CI [− 12.0%, − 2.1%], p = 0.005) whilst IRS at the households contributed to 6.8pt reduction in malaria prevalence (95% CI [− 12.0%, − 2.1%], p = 0.005). Households with access to both ITNs and IRS contributed to a 27.1pt reduction in self-reported malaria prevalence among women (95% CI [− 12.0%, − 2.1%], p = 0.005). Conclusion Access to both ITNs and application of IRS at the household level contributed to a significant reduction in self-reported malaria prevalence among women of reproductive age in Ghana. This finding confirms the need for integration of malaria control interventions to facilitate attainment of malaria elimination in Ghana. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04136-3.
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Affiliation(s)
- Yakubu Alhassan
- Department of Health Policy, Planning and Management, School of Public Health, University of Ghana, Accra, Ghana
| | - Duah Dwomoh
- Department of Biostatistics, School of Public Health, University of Ghana, Accra, Ghana.
| | - Susan Ama Amuasi
- Department of Physician Assistantship and Public Health, School of Medicine and Health Sciences, Central University College, Accra, Ghana
| | - Justice Nonvignon
- Department of Health Policy, Planning and Management, School of Public Health, University of Ghana, Accra, Ghana
| | - Harriet Bonful
- Department of Epidemiology, School of Public Health, University of Ghana, Accra, Ghana
| | - Mary Tetteh
- Department of Health Policy, Planning and Management, School of Public Health, University of Ghana, Accra, Ghana
| | - Kofi Agyabeng
- Department of Biostatistics, School of Public Health, University of Ghana, Accra, Ghana
| | - Martha Kotey
- Department of Epidemiology, School of Public Health, University of Ghana, Accra, Ghana
| | - Alfred E Yawson
- Department of Community Health, University of Ghana Medical School, University of Ghana, Accra, Ghana
| | - Samuel Bosomprah
- Department of Biostatistics, School of Public Health, University of Ghana, Accra, Ghana
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10
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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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11
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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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12
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Mbewe RB, Keven JB, Mzilahowa T, Mathanga D, Wilson M, Cohee L, Laufer MK, Walker ED. Blood-feeding patterns of Anopheles vectors of human malaria in Malawi: implications for malaria transmission and effectiveness of LLIN interventions. Malar J 2022; 21:67. [PMID: 35241083 PMCID: PMC8892392 DOI: 10.1186/s12936-022-04089-7] [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: 08/23/2021] [Accepted: 02/16/2022] [Indexed: 11/23/2022] Open
Abstract
Background Access to human hosts by Anopheles mosquitoes is a key determinant of vectorial capacity for malaria, but it can be limited by use of long-lasting insecticidal nets (LLINs). In Malawi, pyrethroid-treated LLINs with and without the synergist piperonyl butoxide (PBO) were distributed to control malaria. This study investigated the blood-feeding patterns of malaria vectors and whether LLINs containing pyrethroid and PBO led to a reduction of human blood feeding than those containing only pyrethroids. Methods Mosquitoes were sampled inside houses from May 2019 through April 2020 by aspiration, pyrethrum spray catch, and light trap methods in two sites. One site (Namanolo, Balaka district) had LLINs containing only pyrethroids whereas the other (Ntaja, Machinga district) had LLINs with both pyrethroids and PBO. Anopheles species, their blood-meal host, and infection with Plasmodium falciparum were determined using PCR methods. Results A total of 6585 female Anopheles were sampled in 203 houses. Of these, 633 (9.6%) were blood-fed mosquitoes comprising of 279 (44.1%) Anopheles arabiensis, 103 (16.3%) Anopheles gambiae 212 (33.5), Anopheles funestus, 2 (0.3%), Anopheles parensis and 37 (5.8%) were unidentified Anopheles spp. Blood meal hosts were successfully identified for 85.5% (n = 541) of the blood-fed mosquitoes, of which 436 (81.0%) were human blood meals, 28 (5.2%) were goats, 11 (2.0%) were dogs, 60 (11.1%) were mixed goat-human blood meals, 5 (0.9%) were dog–human, and 1 was a mixed dog-goat. Human blood index (fraction of blood meals that were humans) was significantly higher in Namanolo (0.96) than Ntaja (0.89). Even though human blood index was high, goats were over-selected than humans after accounting for relative abundance of both hosts. The number of infectious Anopheles bites per person-year was 44 in Namanolo and 22 in Ntaja. Conclusion Although LLINs with PBO PBO may have reduced human blood feeding, access to humans was extremely high despite high LLIN ownership and usage rates in both sites. This finding could explain persistently high rates of malaria infections in Malawi. However, this study had one village for each net type, thus the observed differences may have been a result of other factors present in each village. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04089-7.
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Affiliation(s)
- Rex B Mbewe
- Department of Physics and Biochemical Sciences, Polytechnic, University of Malawi, Blantyre, Malawi. .,Department of Entomology, Michigan State University, East Lansing, MI, 48824, USA.
| | - John B Keven
- Department of Entomology, Michigan State University, East Lansing, MI, 48824, USA.,Department of Public Health, University of California-Irvine, Irvine, CA, USA
| | - Themba Mzilahowa
- Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Don Mathanga
- Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Mark Wilson
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI, USA
| | - Lauren Cohee
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Miriam K Laufer
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Edward D Walker
- Department of Entomology, Michigan State University, East Lansing, MI, 48824, USA.,Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
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13
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Namias A, Jobe NB, Paaijmans KP, Huijben S. The need for practical insecticide-resistance guidelines to effectively inform mosquito-borne disease control programs. eLife 2021; 10:e65655. [PMID: 34355693 PMCID: PMC8346280 DOI: 10.7554/elife.65655] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 07/26/2021] [Indexed: 11/13/2022] Open
Abstract
Monitoring local mosquito populations for insecticide resistance is critical for effective vector-borne disease control. However, widely used phenotypic assays, which are designed to monitor the emergence and spread of insecticide resistance (technical resistance), do not translate well to the efficacy of vector control products to suppress mosquito numbers in the field (practical resistance). This is because standard testing conditions such as environmental conditions, exposure dose, and type of substrate differ dramatically from those experienced by mosquitoes under field conditions. In addition, field mosquitoes have considerably different physiological characteristics such as age and blood-feeding status. Beyond this, indirect impacts of insecticide resistance and/or exposure on mosquito longevity, pathogen development, host-seeking behavior, and blood-feeding success impact disease transmission. Given the limited number of active ingredients currently available and the observed discordance between resistance and disease transmission, we conclude that additional testing guidelines are needed to determine practical resistance-the efficacy of vector control tools under relevant local conditions- in order to obtain programmatic impact.
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Affiliation(s)
- Alice Namias
- Département de Biologie, Ecole Normale Supérieure, PSL Research University, Paris, France
- Institut des Sciences de l'Evolution de Montpellier (ISEM), Université de Montpellier, CNRS, IRD, EPHE, Montpellier, France
| | - Ndey Bassin Jobe
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Life Sciences C, Tempe, United States
| | - Krijn Petrus Paaijmans
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Life Sciences C, Tempe, United States
- The Biodesign Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, Biodesign Institute, Tempe, United States
- ISGlobal, Carrer del Rosselló, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Distrito da Manhiça, Mozambique
| | - Silvie Huijben
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Life Sciences C, Tempe, United States
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14
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Effectiveness of long-lasting insecticidal nets in prevention of malaria among individuals visiting health centres in Ziway-Dugda District, Ethiopia: matched case-control study. Malar J 2021; 20:301. [PMID: 34217315 PMCID: PMC8254940 DOI: 10.1186/s12936-021-03833-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Accepted: 06/27/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria is a major health problem in Ethiopia. Sleeping under long-lasting insecticidal nets (LLINs) is its major control strategy. Despite high LLINs use (84%) in Ziway-Dugda District, malaria remained a public health problem, raising concern on its effectiveness. Understanding the effectiveness of malaria control interventions is vital. This study evaluated the effectiveness of LLINs and determinants of malaria in Ziway-Dugda District, Arsi Zone Ethiopia. METHODS A matched case-control study was conducted among 284 study participants (71 cases and 213 controls) in Ziway-Dugda District, Arsi Zone, Ethiopia from March to May, 2017. Three health centers were selected randomly, and enrolled individuals newly diagnosed for malaria proportionally. Cases and controls were individuals testing positive and negative for malaria using rapid diagnostic tests. Each case was matched to three controls using the age of (5 years), gender and village of residence. The information was collected using pre-tested structured questionnaires through face to face interviews and observation. Data were entered into Epi-Info version 3.5, and analysed using Stata version-12. Conditional logistic regression was performed, and odds of LLINs use were compared using matched Adjusted Odds Ratio (AOR), 95% confidence interval (CI) and p-value of < 0.05. RESULTS One hundred twenty-three (61.2%) of the controls and 22 (32.8%) of cases had regularly slept under LLINs in the past two weeks. Using multivariate analysis, sleeping under LLINs for the past two weeks (AOR = 0.23, 95%CI = 0.11-0.45); living in houses sprayed with indoor residual spray (IRS) (AOR = 0.23, 95%CI: 0.10-0.52); and staying late outdoors at night in the past two-weeks (AOR = 2.99, 95%CI = 1.44-6.19) were determinant factors. CONCLUSIONS Sleeping under LLINs is effective for malaria prevention in the district. IRS and staying late outdoors at night were determinants of malaria. It is recommended to increase attention on strengthening LLINs use and IRS in the area.
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15
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Andronescu LR, Sharma A, Peterson I, Kachingwe M, Kachepa W, Liang Y, Gutman JR, Mathanga DP, Chinkhumba J, Laufer MK. The effect of intermittent preventive treatment of malaria during pregnancy and placental malaria on infant risk of malaria. J Infect Dis 2021; 225:248-256. [PMID: 34216212 DOI: 10.1093/infdis/jiab351] [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: 03/25/2021] [Accepted: 07/02/2021] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Intermittent preventive treatment of malaria during pregnancy (IPTp) with dihydroartemisinin-piperaquine (DP) provides greater protection from placental malaria than sulfadoxine-pyrimethamine (SP). Some studies suggest placental malaria alters the risk of malaria infection in infants, but few studies have quantified the effect of IPTp on infant susceptibility to malaria. METHODS Infants born to pregnant women enrolled in a randomized clinical trial comparing IPTp-SP and IPTp-DP in Malawi were followed from birth to 24 months to assess effect of IPTp and placental malaria on time to first malaria episode and P. falciparum incidence. RESULTS In total, 192 infants born to mothers randomized to IPTp-SP and 195 to mothers randomized to IPTp-DP were enrolled. Infants in the IPTp exposure groups did not differ significantly regarding incidence of clinical malaria (IRR= 1.03; 95% CI: 0.58 - 1.86) or incidence of infection (IRR= 1.18; 95% CI: 0.92-1.55). Placental malaria exposure was not associated with incidence of clinical malaria (IRR= 1.03; 95% CI: 0.66-1.59) or incidence of infection (IRR:= 1.15; 95% CI: 0.88-1.50). Infant sex, season of birth, and maternal gravidity did not confound results. CONCLUSIONS We did not find evidence that IPTp regimen or placental malaria exposure influenced risk of malaria during infancy in this population.
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Affiliation(s)
- Liana R Andronescu
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Ankur Sharma
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Ingrid Peterson
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Martin Kachingwe
- Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Witness Kachepa
- Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Yuanyuan Liang
- Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Julie R Gutman
- Malaria Branch, Centers for Disease Control and Prevention, Atlanta, GA 30333 USA
| | - Don P Mathanga
- Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Jobiba Chinkhumba
- Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Miriam K Laufer
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201 USA
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16
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Threats to the effectiveness of insecticide-treated bednets for malaria control: thinking beyond insecticide resistance. LANCET GLOBAL HEALTH 2021; 9:e1325-e1331. [PMID: 34216565 DOI: 10.1016/s2214-109x(21)00216-3] [Citation(s) in RCA: 73] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/03/2021] [Accepted: 04/23/2021] [Indexed: 12/22/2022]
Abstract
From 2004 to 2019, insecticide-treated bednets (ITNs) have been the most effective tool for reducing malaria morbidity and mortality in sub-Saharan Africa. Recently, however, the decline in malaria cases and deaths has stalled. Some suggest that this inertia is due to increasing resistance in malaria vectors to the pyrethroid insecticides used for treating ITNs. However, there is presently little evidence to reach this conclusion and we therefore recommend that a broader perspective to evaluate ITN effectiveness in terms of access to nets, use of nets, bioefficacy, and durability should be taken. We argue that a single focus on insecticide resistance misses the bigger picture. To improve the effects of ITNs, net coverage should increase by increasing funding for programmes, adopting improved strategies for increasing ITN uptake, and enhancing the longevity of the active ingredients and the physical integrity of nets, while simultaneously accelerating the development and evaluation of novel vector control tools.
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17
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Danwang C, Khalil É, Achu D, Ateba M, Abomabo M, Souopgui J, De Keukeleire M, Robert A. Fine scale analysis of malaria incidence in under-5: hierarchical Bayesian spatio-temporal modelling of routinely collected malaria data between 2012-2018 in Cameroon. Sci Rep 2021; 11:11408. [PMID: 34075157 PMCID: PMC8169670 DOI: 10.1038/s41598-021-90997-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 05/20/2021] [Indexed: 11/28/2022] Open
Abstract
The current study aims to provide a fine-scale spatiotemporal estimate of malaria incidence among Cameroonian under-5, and to determine its associated environmental factors, to set up preventive interventions that are adapted to each health district of Cameroon. Routine data on symptomatic malaria in children under-5 collected in health facilities, between 2012 and 2018 were used. The trend of malaria cases was assessed by the Mann–Kendall (M–K) test. A time series decomposition was applied to malaria incidence to extract the seasonal component. Malaria risk was estimated by the standardised incidence ratio (SIR) and smoothed by a hierarchical Bayesian spatiotemporal model. In total, 4,052,216 cases of malaria were diagnosed between 2012 and 2018. There was a gradual increase per year, from 369,178 in 2012 to 652,661 in 2018. After adjusting the data for completeness, the national incidence ranged from 489‰ in 2012 to 603‰ in 2018, with an upward trend (M–K test p-value < 0.001). At the regional level, an upward trend was observed in Adamaoua, Centre without Yaoundé, East, and South regions. There was a positive spatial autocorrelation of the number of malaria incident-cases per district per year as suggested by the Moran’s I test (statistic range between 0.11 and 0.53). The crude SIR showed a heterogeneous malaria risk with values ranging from 0.00 to 8.90, meaning that some health districts have a risk 8.9 times higher than the national annual level. The incidence and risk of malaria among under-5 in Cameroon are heterogeneous and vary significantly across health districts and seasons. It is crucial to adapt malaria prevention measures to the specificities of each health district, in order to reduce its burden in health districts where the trend is upward.
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Affiliation(s)
- Celestin Danwang
- Epidemiology and Biostatistics Unit, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Box: B1.30.13, Brussels, Belgium.
| | - Élie Khalil
- Epidemiology and Biostatistics Unit, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Box: B1.30.13, Brussels, Belgium
| | - Dorothy Achu
- National Malaria Control Program, Ministry of Public Health, Yaoundé, Cameroon
| | - Marcelin Ateba
- National Malaria Control Program, Ministry of Public Health, Yaoundé, Cameroon
| | - Moïse Abomabo
- National Malaria Control Program, Ministry of Public Health, Yaoundé, Cameroon
| | - Jacob Souopgui
- Department of Molecular Biology, Institute of Biology and Molecular Medicine, Universite Libre de Bruxelles, Gosselies, Belgium
| | - Mathilde De Keukeleire
- Epidemiology and Biostatistics Unit, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Box: B1.30.13, Brussels, Belgium
| | - Annie Robert
- Epidemiology and Biostatistics Unit, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Box: B1.30.13, Brussels, Belgium
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18
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Mosha JF, Kulkarni MA, Messenger LA, Rowland M, Matowo N, Pitt C, Lukole E, Taljaard M, Thickstun C, Manjurano A, Mosha FW, Kleinschmidt I, Protopopoff N. Protocol for a four parallel-arm, single-blind, cluster-randomised trial to assess the effectiveness of three types of dual active ingredient treated nets compared to pyrethroid-only long-lasting insecticidal nets to prevent malaria transmitted by pyrethroid insecticide-resistant vector mosquitoes in Tanzania. BMJ Open 2021; 11:e046664. [PMID: 34006037 PMCID: PMC7942254 DOI: 10.1136/bmjopen-2020-046664] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/21/2021] [Accepted: 02/15/2021] [Indexed: 01/21/2023] Open
Abstract
INTRODUCTION The massive scale-up of long-lasting insecticidal nets (LLINs) has led to major reductions in malaria burden in many sub-Saharan African countries. This progress is threatened by widespread insecticide resistance among malaria vectors. This cluster-randomised controlled trial (c-RCT) compares three of the most promising dual active ingredients LLINs (dual-AI LLINs), which incorporate mixtures of insecticides or insecticide synergists to standard LLINs in an area of pyrethroid insecticide resistance. METHODS A four-arm, single-blinded, c-RCT will evaluate the effectiveness of three types of dual-AI LLINs (1) Royal Guard, combining two insecticides, pyriproxyfen and the pyrethroid alpha-cypermethrin; (2) Interceptor G2, combining chlorfenapyr and alpha-cypermethrin; (3) Olyset Plus, an LLIN combining a synergist, piperonyl butoxide and the pyrethroid permethrin, compared with; (4) Interceptor LN, a standard LLIN containing the pyrethroid alpha-cypermethrin as the sole AI. The primary outcomes are malaria infection prevalence in children aged 6 months-14 years and entomological inoculation rate (EIR), as a standard measure of malaria transmission at 24 months postintervention and cost-effectiveness. ETHICS AND DISSEMINATION Ethical approval was received from the institutional review boards of the Tanzanian National Institute for Medical Research, Kilimanjaro Christian Medical University College, London School of Hygiene and Tropical Medicine, and University of Ottawa. Study findings will be actively disseminated via reports and presentations to stakeholders, local community leaders, and relevant national and international policy makers as well as through conferences, and peer-reviewed publications. TRIAL REGISTRATION NUMBER NCT03554616.
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Affiliation(s)
- Jacklin F Mosha
- Parasitology, National Institute for Medical Research Mwanza Research Centre, Mwanza, United Republic of Tanzania
| | - Manisha A Kulkarni
- Epidemiology & Public Health, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada
| | - Louisa A Messenger
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Mark Rowland
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Nancy Matowo
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Catherine Pitt
- Global Health and Development, London School of Hygiene & Tropical Medicine, London, UK
| | - Eliud Lukole
- Parasitology, National Institute for Medical Research Mwanza Research Centre, Mwanza, United Republic of Tanzania
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Monica Taljaard
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Charles Thickstun
- Epidemiology & Public Health, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada
| | - Alphaxard Manjurano
- Parasitology, National Institute for Medical Research Mwanza Research Centre, Mwanza, United Republic of Tanzania
| | - Franklin W Mosha
- Parasitology, Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
| | - Immo Kleinschmidt
- Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
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Owuor KO, Machani MG, Mukabana WR, Munga SO, Yan G, Ochomo E, Afrane YA. Insecticide resistance status of indoor and outdoor resting malaria vectors in a highland and lowland site in Western Kenya. PLoS One 2021; 16:e0240771. [PMID: 33647049 PMCID: PMC7920366 DOI: 10.1371/journal.pone.0240771] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/16/2021] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Long Lasting Insecticidal Nets (LLINs) and indoor residual spraying (IRS) represent powerful tools for controlling malaria vectors in sub-Saharan Africa. The success of these interventions relies on their capability to inhibit indoor feeding and resting of malaria mosquitoes. This study sought to understand the interaction of insecticide resistance with indoor and outdoor resting behavioral responses of malaria vectors from Western Kenya. METHODS The status of insecticide resistance among indoor and outdoor resting anopheline mosquitoes was compared in Anopheles mosquitoes collected from Kisumu and Bungoma counties in Western Kenya. The level and intensity of resistance were measured using WHO-tube and CDC-bottle bioassays, respectively. The synergist piperonyl butoxide (PBO) was used to determine if metabolic activity (monooxygenase enzymes) explained the resistance observed. The mutations at the voltage-gated sodium channel (Vgsc) gene and Ace 1 gene were characterized using PCR methods. Microplate assays were used to measure levels of detoxification enzymes if present. RESULTS A total of 1094 samples were discriminated within Anopheles gambiae s.l. and 289 within An. funestus s.l. In Kisian (Kisumu county), the dominant species was Anopheles arabiensis 75.2% (391/520) while in Kimaeti (Bungoma county) collections the dominant sibling species was Anopheles gambiae s.s 96.5% (554/574). The An. funestus s.l samples analysed were all An. funestus s.s from both sites. Pyrethroid resistance of An.gambiae s.l F1 progeny was observed in all sites. Lower mortality was observed against deltamethrin for the progeny of indoor resting mosquitoes compared to outdoor resting mosquitoes (Mortality rate: 37% vs 51%, P = 0.044). The intensity assays showed moderate-intensity resistance to deltamethrin in the progeny of mosquitoes collected from indoors and outdoors in both study sites. In Kisian, the frequency of vgsc-L1014S and vgsc-L1014F mutation was 0.14 and 0.19 respectively in indoor resting malaria mosquitoes while those of the outdoor resting mosquitoes were 0.12 and 0.12 respectively. The ace 1 mutation was present in higher frequency in the F1 of mosquitoes resting indoors (0.23) compared to those of mosquitoes resting outdoors (0.12). In Kimaeti, the frequencies of vgsc-L1014S and vgsc-L1014F were 0.75 and 0.05 respectively for the F1 of mosquitoes collected indoors whereas those of outdoor resting ones were 0.67 and 0.03 respectively. The ace 1 G119S mutation was present in progeny of mosquitoes from Kimaeti resting indoors (0.05) whereas it was absent in those resting outdoors. Monooxygenase activity was elevated by 1.83 folds in Kisian and by 1.33 folds in Kimaeti for mosquitoes resting indoors than those resting outdoors respectively. CONCLUSION The study recorded high phenotypic, metabolic and genotypic insecticide resistance in indoor resting populations of malaria vectors compared to their outdoor resting counterparts. The indication of moderate resistance intensity for the indoor resting mosquitoes is alarming as it could have an operational impact on the efficacy of the existing pyrethroid based vector control tools. The use of synergist (PBO) in LLINs may be a better alternative for widespread use in these regions recording high insecticide resistance.
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Affiliation(s)
- Kevin O. Owuor
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - Maxwell G. Machani
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Wolfgang R. Mukabana
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
- Science for Health Society, Nairobi, Kenya
| | - Stephen O. Munga
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Guiyun Yan
- Program in Public Health, College of Health Sciences, University of California, Irvine, California, United States of America
| | - Eric Ochomo
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Yaw A. Afrane
- Department of Medical Microbiology, University of Ghana Medical School, University of Ghana, Accra, Ghana
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Rani L, Thapa K, Kanojia N, Sharma N, Singh S, Grewal AS, Srivastav AL, Kaushal J. An extensive review on the consequences of chemical pesticides on human health and environment. JOURNAL OF CLEANER PRODUCTION 2021. [PMID: 0 DOI: 10.1016/j.jclepro.2020.124657] [Citation(s) in RCA: 314] [Impact Index Per Article: 104.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
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Affiliation(s)
- Geoffrey Guenther
- Department of Pediatrics, Children's National Hospital, Washington, DC, USA
| | - Daniel Muller
- The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Dominic Moyo
- Department of Paediatric and Child Health, University of Malawi College of Medicine, Blantyre, Malawi
| | - Douglas Postels
- Department of Pediatric Neurology, George Washington University/ Children's National Medical Center; Washington DC, USA; Blantyre Malaria Project; Blantyre, Malawi, Street Address: Department of Neurology; 111 Michigan Avenue NW; Washington DC; 20010; USA
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Okumu F. The fabric of life: what if mosquito nets were durable and widely available but insecticide-free? Malar J 2020; 19:260. [PMID: 32690016 PMCID: PMC7370456 DOI: 10.1186/s12936-020-03321-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/04/2020] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Bed nets are the commonest malaria prevention tool and arguably the most cost-effective. Their efficacy is because they prevent mosquito bites (a function of physical durability and integrity), and kill mosquitoes (a function of chemical content and mosquito susceptibility). This essay follows the story of bed nets, insecticides and malaria control, and asks whether the nets must always have insecticides. METHODS Key attributes of untreated or pyrethroid-treated nets are examined alongside observations of their entomological and epidemiological impacts. Arguments for and against adding insecticides to nets are analysed in contexts of pyrethroid resistance, personal-versus-communal protection, outdoor-biting, need for local production and global health policies. FINDINGS Widespread resistance in African malaria vectors has greatly weakened the historical mass mosquitocidal effects of insecticide-treated nets (ITNs), which previously contributed communal benefits to users and non-users. Yet ITNs still achieve substantial epidemiological impact, suggesting that physical integrity, consistent use and population-level coverage are increasingly more important than mosquitocidal properties. Pyrethroid-treatment remains desirable where vectors are sufficiently susceptible, but is no longer universally necessary and should be re-examined alongside other attributes, e.g. durability, coverage, acceptability and access. New ITNs with multiple actives or synergists could provide temporary relief in some settings, but their performance, higher costs, and drawn-out innovation timelines do not justify singular emphasis on insecticides. Similarly, sub-lethal insecticides may remain marginally-impactful by reducing survival of older mosquitoes and disrupting parasite development inside the mosquitoes, but such effects vanish under strong resistance. CONCLUSIONS The public health value of nets is increasingly driven by bite prevention, and decreasingly by lethality to mosquitoes. For context-appropriate solutions, it is necessary to acknowledge and evaluate the potential and cost-effectiveness of durable untreated nets across different settings. Though ~ 90% of malaria burden occurs in Africa, most World Health Organization-prequalified nets are manufactured outside Africa, since many local manufacturers lack capacity to produce the recommended insecticidal nets at competitive scale and pricing. By relaxing conditions for insecticides on nets, it is conceivable that non-insecticidal but durable, and possibly bio-degradable nets, could be readily manufactured locally. This essay aims not to discredit ITNs, but to illustrate how singular focus on insecticides can hinder innovation and sustainability.
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Affiliation(s)
- Fredros Okumu
- Environmental Health & Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.
- School of Public Health, University of the Witwatersrand, Johannesburg, Republic of South Africa.
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK.
- School of Life Science and Bioengineering, Nelson Mandela African Institution of Science & Technology, Arusha, Tanzania.
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Gowelo S, McCann RS, Koenraadt CJM, Takken W, van den Berg H, Manda-Taylor L. Community factors affecting participation in larval source management for malaria control in Chikwawa District, Southern Malawi. Malar J 2020; 19:195. [PMID: 32487233 PMCID: PMC7265157 DOI: 10.1186/s12936-020-03268-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/23/2020] [Indexed: 11/12/2022] Open
Abstract
Background To further reduce malaria, larval source management (LSM) is proposed as a complementary strategy to the existing strategies. LSM has potential to control insecticide resistant, outdoor biting and outdoor resting vectors. Concerns about costs and operational feasibility of implementation of LSM at large scale are among the reasons the strategy is not utilized in many African countries. Involving communities in LSM could increase intervention coverage, reduce costs of implementation and improve sustainability of operations. Community acceptance and participation in community-led LSM depends on a number of factors. These factors were explored under the Majete Malaria Project in Chikwawa district, southern Malawi. Methods Separate focus group discussions (FGDs) were conducted with members from the general community (n = 3); health animators (HAs) (n = 3); and LSM committee members (n = 3). In-depth interviews (IDIs) were conducted with community members. Framework analysis was employed to determine the factors contributing to community acceptance and participation in the locally-driven intervention. Results Nine FGDs and 24 IDIs were held, involving 87 members of the community. Widespread knowledge of malaria as a health problem, its mode of transmission, mosquito larval habitats and mosquito control was recorded. High awareness of an association between creation of larval habitats and malaria transmission was reported. Perception of LSM as a tool for malaria control was high. The use of a microbial larvicide as a form of LSM was perceived as both safe and effective. However, actual participation in LSM by the different interviewee groups varied. Labour-intensiveness and time requirements of the LSM activities, lack of financial incentives, and concern about health risks when wading in water bodies contributed to lower participation. Conclusion Community involvement in LSM increased local awareness of malaria as a health problem, its risk factors and control strategies. However, community participation varied among the respondent groups, with labour and time demands of the activities, and lack of incentives, contributing to reduced participation. Innovative tools that can reduce the labour and time demands could improve community participation in the activities. Further studies are required to investigate the forms and modes of delivery of incentives in operational community-driven LSM interventions.
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Affiliation(s)
- Steven Gowelo
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands. .,Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.,Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | | | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Lucinda Manda-Taylor
- Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.,Department of Health Systems and Policy, School of Public Health and Family Medicine, College of Medicine, Blantyre, Malawi
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Bell GJ, Loop M, Topazian HM, Hudgens M, Mvalo T, Juliano JJ, Kamthunzi P, Tegha G, Mofolo I, Hoffman I, Bailey JA, Emch M. Case reduction and cost-effectiveness of the RTS,S/AS01 malaria vaccine alongside bed nets in Lilongwe, Malawi. Vaccine 2020; 38:4079-4087. [PMID: 32362527 DOI: 10.1016/j.vaccine.2020.04.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 04/10/2020] [Accepted: 04/13/2020] [Indexed: 01/22/2023]
Abstract
BACKGROUND RTS,S/AS01, the most advanced vaccine against malaria, is now undergoing pilot implementation in Malawi, Ghana, and Kenya where an estimated 360,000 children will be vaccinated each year. In this study we evaluate RTS,S/AS01 alongside bed net use and estimate cost-effectiveness. METHODS RTS,S/AS01 phase III trial and bed net prevalence data were used to determine the effect of vaccination in the urban/periurban and rural areas of Lilongwe, Malawi. Cost data were used to calculate the cost-effectiveness of various interventions over three years. FINDINGS Since bed nets reduce malaria incidence and homogeneous vaccine efficacy was assumed, participants without bed nets received greater relative benefit from vaccination with RTS,S/AS01 than participants with bed nets. Similarly, since malaria incidence in rural Lilongwe is higher than in urban Lilongwe, the impact and cost-effectiveness of vaccine interventions is increased in rural areas. In rural Lilongwe, we estimated that vaccinating one child without a bed net would prevent 2·59 (1·62 to 3·38) cases of malaria over three years, corresponding to a cost of $10·08 (7·71 to 16·13) per case averted. Alternatively, vaccinating one child with a bed net would prevent 1·59 (0·87 to 2·57) cases, corresponding to $16·43 (10·16 to 30·06) per case averted. Providing RTS,S/AS01 to 30,000 children in rural Lilongwe was estimated to cost $782,400 and to prevent 58,611 (35,778 to 82,932) cases of malaria over a three-year period. Joint interventions providing both vaccination and bed nets (to those without them) were estimated to prevent additional cases of malaria and to be similarly cost-effective, compared to vaccine-only interventions. INTERPRETATION To maximize malaria prevention, vaccination and bed net distribution programs could be integrated. FUNDING Impacts of Environment, Host Genetics and Antigen Diversity on Malaria Vaccine Efficacy (1R01AI137410-01).
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Affiliation(s)
- Griffin J Bell
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Matthew Loop
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Hillary M Topazian
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Michael Hudgens
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Tisungane Mvalo
- University of North Carolina, Chapel Hill, NC 27599, USA; University of North Carolina Project, Lilongwe, Malawi.
| | - Jonathan J Juliano
- Division of Infectious Diseases, School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Portia Kamthunzi
- University of North Carolina, Chapel Hill, NC 27599, USA; University of North Carolina Project, Lilongwe, Malawi.
| | - Gerald Tegha
- University of North Carolina Project, Lilongwe, Malawi.
| | - Innocent Mofolo
- University of North Carolina, Chapel Hill, NC 27599, USA; University of North Carolina Project, Lilongwe, Malawi.
| | - Irving Hoffman
- University of North Carolina, Chapel Hill, NC 27599, USA; University of North Carolina Project, Lilongwe, Malawi.
| | - Jeffrey A Bailey
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI 02903, USA
| | - Michael Emch
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
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Runge M, Snow RW, Molteni F, Thawer S, Mohamed A, Mandike R, Giorgi E, Macharia PM, Smith TA, Lengeler C, Pothin E. Simulating the council-specific impact of anti-malaria interventions: A tool to support malaria strategic planning in Tanzania. PLoS One 2020; 15:e0228469. [PMID: 32074112 PMCID: PMC7029840 DOI: 10.1371/journal.pone.0228469] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 01/16/2020] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION The decision-making process for malaria control and elimination strategies has become more challenging. Interventions need to be targeted at council level to allow for changing malaria epidemiology and an increase in the number of possible interventions. Models of malaria dynamics can support this process by simulating potential impacts of multiple interventions in different settings and determining appropriate packages of interventions for meeting specific expected targets. METHODS The OpenMalaria model of malaria dynamics was calibrated for all 184 councils in mainland Tanzania using data from malaria indicator surveys, school parasitaemia surveys, entomological surveillance, and vector control deployment data. The simulations were run for different transmission intensities per region and five interventions, currently or potentially included in the National Malaria Strategic Plan, individually and in combination. The simulated prevalences were fitted to council specific prevalences derived from geostatistical models to obtain council specific predictions of the prevalence and number of cases between 2017 and 2020. The predictions were used to evaluate in silico the feasibility of the national target of reaching a prevalence of below 1% by 2020, and to suggest alternative intervention stratifications for the country. RESULTS The historical prevalence trend was fitted for each council with an agreement of 87% in 2016 (95%CI: 0.84-0.90) and an agreement of 90% for the historical trend (2003-2016) (95%CI: 0.87-0.93) The current national malaria strategy was expected to reduce the malaria prevalence between 2016 and 2020 on average by 23.8% (95% CI: 19.7%-27.9%) if current case management levels were maintained, and by 52.1% (95% CI: 48.8%-55.3%) if the case management were improved. Insecticide treated nets and case management were the most cost-effective interventions, expected to reduce the prevalence by 25.0% (95% CI: 19.7%-30.2) and to avert 37 million cases between 2017 and 2020. Mass drug administration was included in most councils in the stratification selected for meeting the national target at minimal costs, expected to reduce the prevalence by 77.5% (95%CI: 70.5%-84.5%) and to avert 102 million cases, with almost twice higher costs than those of the current national strategy. In summary, the model suggested that current interventions are not sufficient to reach the national aim of a prevalence of less than 1% by 2020 and a revised strategic plan needs to consider additional, more effective interventions, especially in high transmission areas and that the targets need to be revisited. CONCLUSION The methodology reported here is based on intensive interactions with the NMCP and provides a helpful tool for assessing the feasibility of country specific targets and for determining which intervention stratifications at sub-national level will have most impact. This country-led application could support strategic planning of malaria control in many other malaria endemic countries.
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Affiliation(s)
- Manuela Runge
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Robert W. Snow
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, England, United Kingodm
- Population Health Unit, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Fabrizio Molteni
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Sumaiyya Thawer
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Ally Mohamed
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Renata Mandike
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Emanuele Giorgi
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, England, United Kingodm
| | - Peter M. Macharia
- Population Health Unit, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Thomas A. Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Christian Lengeler
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Emilie Pothin
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Clinton Health Access Initiative, Boston, Massachusetts, United States of America
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Shah MP, Steinhardt LC, Mwandama D, Mzilahowa T, Gimnig JE, Bauleni A, Wong J, Wiegand R, Mathanga DP, Lindblade KA. The effectiveness of older insecticide-treated bed nets (ITNs) to prevent malaria infection in an area of moderate pyrethroid resistance: results from a cohort study in Malawi. Malar J 2020; 19:24. [PMID: 31941502 PMCID: PMC6964029 DOI: 10.1186/s12936-020-3106-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 01/07/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A previous cohort study in Malawi showed that users of new insecticide-treated bed nets (ITNs) were significantly protected against malaria compared to non-users, despite moderate levels of pyrethroid resistance among the primary mosquito vectors. The present study investigated whether ITNs that were 1-2 years old continued to protect users in the same area with moderate pyrethroid resistance. METHODS One year following a baseline cross-sectional malaria parasitaemia prevalence survey and universal distribution of deltamethrin ITNs (May 2012), a fixed cohort of 1223 children aged 6-59 months was enrolled (April 2013). Children were tested for parasitaemia at monthly scheduled visits and at unscheduled sick visits from May to December 2013 using rapid diagnostic tests. ITN use the prior night and the condition of ITNs (based on presence of holes) was assessed by caregiver self-report. The incidence rate ratio (RR) comparing malaria infection among users and non-users of ITNs was modelled using generalized estimating equations adjusting for potential confounders and accounting for repeated measures on each child. The protective efficacy (PE) of ITN use was calculated as 1 - RR. RESULTS In this cohort, self-reported ITN use remained consistently high (> 95%) over the study period. Although users of ITNs were slightly more protected compared to non-users of ITNs, the difference in incidence of infection was not statistically significant (RR 0.83, 95% confidence interval [CI] 0.54-1.27). Among ITN users, malaria incidence was significantly lower in users of ITNs with no holes (of any size) compared to users of ITNs with ≥ 1 hole (RR 0.82, 95% CI 0.69-0.98). CONCLUSIONS There was no significant PE of using 1-2 year-old ITNs on the incidence of malaria in children in an area of moderate pyrethroid resistance, but among ITN users, the authors found increased protection by ITNs with no holes compared to ITNs with holes. Given the moderate levels of pyrethroid resistance in the primary malaria vector and recent evidence of added benefits of ITNs with synergists or non-pyrethroid insecticides, next-generation ITNs may be a useful strategy to address pyrethroid resistance and should be further explored in Malawi.
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Affiliation(s)
- Monica P Shah
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA.
| | - Laura C Steinhardt
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Dyson Mwandama
- College of Medicine, Malaria Alert Centre, Blantyre, Malawi
| | | | - John E Gimnig
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Andy Bauleni
- College of Medicine, Malaria Alert Centre, Blantyre, Malawi
| | - Jacklyn Wong
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Ryan Wiegand
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Don P Mathanga
- College of Medicine, Malaria Alert Centre, Blantyre, Malawi
| | - Kim A Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA
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Kawale P, Pagliari C, Grant L. What does the Malawi Demographic and Health Survey say about the country's first Health Sector Strategic Plan? J Glob Health 2019; 9:010314. [PMID: 31217952 PMCID: PMC6551483 DOI: 10.7189/jogh.09.010314] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Paul Kawale
- Nkhoma Hospital, Nkhoma, Malawi.,Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, UK
| | - Claudia Pagliari
- Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, UK
| | - Liz Grant
- Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, UK
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Collins E, Vaselli NM, Sylla M, Beavogui AH, Orsborne J, Lawrence G, Wiegand RE, Irish SR, Walker T, Messenger LA. The relationship between insecticide resistance, mosquito age and malaria prevalence in Anopheles gambiae s.l. from Guinea. Sci Rep 2019; 9:8846. [PMID: 31222175 PMCID: PMC6586859 DOI: 10.1038/s41598-019-45261-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 05/30/2019] [Indexed: 11/15/2022] Open
Abstract
Insecticide resistance across sub-Saharan Africa may impact the continued effectiveness of malaria vector control. We investigated the association between carbamate and pyrethroid resistance with Anopheles gambiae s.l. parity, Plasmodium falciparum infection, and molecular insecticide resistance mechanisms in Guinea. Pyrethroid resistance was intense, with field populations surviving ten times the insecticidal concentration required to kill susceptible individuals. The L1014F kdr-N1575Y haplotype and I1527T mutation were significantly associated with mosquito survival following permethrin exposure (Prevalence Ratio; PR = 1.92, CI = 1.09–3.37 and PR = 2.80, CI = 1.03–7.64, respectively). Partial restoration of pyrethroid susceptibility following synergist pre-exposure suggests a role for mixed-function oxidases. Carbamate resistance was lower and significantly associated with the G119S Ace-1 mutation. Oocyst rates were 6.8% and 4.2% among resistant and susceptible mosquitoes, respectively; survivors of bendiocarb exposure were significantly more likely to be infected. Pyrethroid resistant mosquitoes had significantly lower parity rates than their susceptible counterparts (PR = 1.15, CI = 1.10–1.21). Our findings emphasize the need for additional studies directly assessing the influence of insecticide resistance on mosquito fitness.
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Affiliation(s)
- Emma Collins
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Natasha M Vaselli
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Moussa Sylla
- Centre National de Formation et de Recherche en Santé Rurale de Maferinyah, Maferinyah, Guinea
| | - Abdoul H Beavogui
- Centre National de Formation et de Recherche en Santé Rurale de Maferinyah, Maferinyah, Guinea
| | - James Orsborne
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Gena Lawrence
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Ryan E Wiegand
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Seth R Irish
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America.,President's Malaria Initiative, Bureau for Global Health, Office of Infectious Disease, United States Agency for International Development, Washington DC, United States of America
| | - Thomas Walker
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Louisa A Messenger
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America. .,American Society for Microbiology, 1752 N Street, NW, Washington DC, 20036, United States of America.
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Oumbouke WA, Koffi AA, Alou LPA, Rowland M, N’Guessan R. Evaluation of standard pyrethroid based LNs (MiraNet and MagNet) in experimental huts against pyrethroid resistant Anopheles gambiae s.l. M'bé, Côte d'Ivoire: Potential for impact on vectorial capacity. PLoS One 2019; 14:e0215074. [PMID: 30973948 PMCID: PMC6459542 DOI: 10.1371/journal.pone.0215074] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 03/26/2019] [Indexed: 11/19/2022] Open
Abstract
Background There is evidence from experimental hut and household studies that the entomological efficacy of long lasting pyrethroid treated nets (LLINs) is compromised in areas of pyrethroid resistance. The rapid increase in resistance intensity in African malaria vectors could further undermine the performance of these nets. The pyrethroid resistance intensity in Anopheles gambiae s.l. M’bé from central Côte d’Ivoire is reported to be high (> 1700 fold). Whether this translates into an increase in entomological indicators of malaria transmission needs investigation. Method The efficacy of two long lasting insecticidal nets (LN) MiraNet and MagNet, both alpha-cypermethrin based was evaluated in experimental huts against pyrethroid resistant Anopheles gambiae in M’bé, central Côte d’Ivoire. All nets were deliberately holed to simulate wear-and-tear and were tested unwashed and after 20 standardized washes. Results The entry rates of An. gambiae s.l. into huts with insecticide treated nets were 62–84% lower than entry into huts with untreated nets (p < 0.001). Exit rates of An. gambiae s.l. with unwashed MiraNet and MagNet LNs were significantly greater than with untreated nets (50–60% vs 26%) and this effect after washing 20 times nets did not decrease. Blood-feeding with both nets was significantly inhibited relative to the untreated reference net (31–55%) (p < 0.001). Washing MiraNet LN 20 times had no significant impact on protection against An. gambiae s.l. bites but it did cause a significant fall by 40% in protection with MagNet LN (p < 0.001). All insecticide treated nets induced higher mortality of An. gambiae s.l. than the untreated net (p < 0.05). The impact though significant was limited (14–30%). The personal protection against An. gambiae s.l. bites derived from all treatments was high (75–90%). The overall insecticidal effect was compromised by pyrethroid resistance and was not detectable in some treatments. Conclusion In this area of high pyrethroid resistance intensity (over 1700 fold), both MiraNet and MagNet LNs still conferred appreciable personal protection against mosquito bites despite inducing only slightly greater mortality of pyrethroid resistant Anopheles mosquitoes than untreated nets. The impact is comparable to moderately intense Benin resistance area (207 fold) and Burkina Faso (over 1000 fold). This preserved level of protection plus the small but sensitive killing of mosquitoes may continue to impact vectorial capacity despite high intensity of resistance. Nevertheless, there is an obvious need for strategies and nets with novel mode of action to enhance vector control.
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Affiliation(s)
- Welbeck A. Oumbouke
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d’Ivoire
- * E-mail:
| | - 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
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Raphael N’Guessan
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d’Ivoire
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Dhiman S. Are malaria elimination efforts on right track? An analysis of gains achieved and challenges ahead. Infect Dis Poverty 2019; 8:14. [PMID: 30760324 PMCID: PMC6375178 DOI: 10.1186/s40249-019-0524-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 01/31/2019] [Indexed: 01/30/2023] Open
Abstract
Background Malaria causes significant morbidity and mortality each year. In the past few years, the global malaria cases have been declining and many endemic countries are heading towards malaria elimination. Nevertheless, reducing the number of cases seems to be easy than sustained elimination. Therefore to achieve the objective of complete elimination and maintaining the elimination status, it is necessary to assess the gains made during the recent years. Main text With inclining global support and World Health Organisation (WHO) efforts, the control programmes have been implemented effectively in many endemic countries. Given the aroused interest and investments into malaria elimination programmes at global level, the ambitious goal of elimination appears feasible. Sustainable interventions have played a pivotal role in malaria contraction, however drug and insecticide resistance, social, demographic, cultural and behavioural beliefs and practices, and unreformed health infrastructure could drift back the progress attained so far. Ignoring such impeding factors coupled with certain region specific factors may jeopardise our ability to abide righteous track to achieve global elimination of malaria parasite. Although support beyond the territories is important, but well managed integrated vector management approach at regional and country level using scrupulously selected area specific interventions targeting both vector and parasite along with the community involvement is necessary. A brief incline in malaria during 2016 has raised fresh perturbation on whether elimination could be achieved on time or not. Conclusions The intervention tools available currently can most likely reduce transmission but clearing of malaria epicentres from where the disease can flare up any time, is not possible without involving local population. Nevertheless maintaining zero malaria transmission and checks on malaria import in declared malaria free countries, and further speeding up of interventions to stop transmission in elimination countries is most desirable. Strong collaboration backed by adequate political and financial support among the countries with a common objective to eliminate malaria must be on top priority. The present review attempts to assess the progress gained in malaria elimination during the past few years and highlights some issues that could be important in successful malaria elimination. Electronic supplementary material The online version of this article (10.1186/s40249-019-0524-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sunil Dhiman
- Vector Management Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, 474002, India.
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31
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Tokponnon FT, Sissinto Y, Ogouyémi AH, Adéothy AA, Adechoubou A, Houansou T, Oke M, Kinde-Gazard D, Massougbodji A, Akogbeto MC, Cornelie S, Corbel V, Knox TB, Mnzava AP, Donnelly MJ, Kleinschmidt I, Bradley J. Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: evidence from health facility data from Benin. Malar J 2019; 18:37. [PMID: 30744666 PMCID: PMC6371432 DOI: 10.1186/s12936-019-2656-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/16/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Insecticide-based interventions have averted more than 500 million malaria cases since 2000, but insecticide resistance in mosquitoes could bring about a rebound in disease and mortality. This study investigated whether insecticide resistance was associated with increased incidence of clinical malaria. METHODS In an area of southern Benin with insecticide resistance and high use of insecticide-treated nets (ITNs), malaria morbidity and insecticide resistance were measured simultaneously in 30 clusters (villages or collections of villages) multiple times over the course of 2 years. Insecticide resistance frequencies were measured using the standard World Health Organization bioassay test. Malaria morbidity was measured by cases recorded at health facilities both in the whole population using routinely collected data and in a passively followed cohort of children under 5 years old. RESULTS There was no evidence that incidence of malaria from routinely collected data was higher in clusters with resistance frequencies above the median, either in children aged under 5 (RR = 1.27 (95% CI 0.81-2.00) p = 0.276) or in individuals aged 5 or over (RR = 1.74 (95% CI 0.91-3.34) p = 0.093). There was also no evidence that incidence was higher in clusters with resistance frequencies above the median in the passively followed cohort (RR = 1.11 (0.52-2.35) p = 0.777). CONCLUSIONS This study found no association between frequency of resistance and incidence of clinical malaria in an area where ITNs are the principal form of vector control. This may be because, as other studies have shown, ITNs continue to offer some protection from malaria even in the presence of insecticide resistance. Irrespective of resistance, nets provide only partial protection so the development of improved or supplementary vector control tools is required to reduce Africa's unacceptably high malaria burden.
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Affiliation(s)
- Filémon T Tokponnon
- National Malaria Control Programme, Cotonou, Benin.,Ministry of Health, Cotonou, Benin
| | - Yolande Sissinto
- Faculté des Sciences de la Santé de l'Université d'Abomey Calavi, Cotonou, Benin
| | | | - Adicath Adéola Adéothy
- National Malaria Control Programme, Cotonou, Benin.,Faculté des Sciences de la Santé de l'Université d'Abomey Calavi, Cotonou, Benin
| | - Alioun Adechoubou
- National Malaria Control Programme, Cotonou, Benin.,Ministry of Health, Cotonou, Benin
| | | | - Mariam Oke
- National Malaria Control Programme, Cotonou, Benin.,Ministry of Health, Cotonou, Benin
| | | | - Achille Massougbodji
- Faculté des Sciences de la Santé de l'Université d'Abomey Calavi, Cotonou, Benin
| | | | - Sylvie Cornelie
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), CNRS, University of Montpellier, Montpellier, France
| | - Vincent Corbel
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), CNRS, University of Montpellier, Montpellier, France
| | - Tessa B Knox
- Global Malaria Programme, WHO, Geneva, Switzerland
| | | | - Martin J Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Immo Kleinschmidt
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - John Bradley
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK.
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32
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Kristan M, Abeku TA, Lines J. Effect of environmental variables and kdr resistance genotype on survival probability and infection rates in Anopheles gambiae (s.s.). Parasit Vectors 2018; 11:560. [PMID: 30367663 PMCID: PMC6204000 DOI: 10.1186/s13071-018-3150-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 10/14/2018] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Environmental factors, especially ambient temperature and relative humidity affect both mosquitoes and malaria parasites. The early part of sporogony is most sensitive and is affected by high temperatures and temperature fluctuation immediately following ingestion of an infectious blood meal. The aim of this study was to explore whether environmental variables such as temperature, together with the presence of the kdr insecticide resistance mutations, have an impact on survival probability and infection rates in wild Anopheles gambiae (s.s.) exposed and unexposed to a pyrethroid insecticide. METHODS Anopheles gambiae (s.s.) were collected as larvae, reared to adults, and fed on blood samples from 42 Plasmodium falciparum-infected local patients at a health facility in mid-western Uganda, then exposed either to nets treated with sub-lethal doses of deltamethrin or to untreated nets. After seven days, surviving mosquitoes were dissected and their midguts examined for oocysts. Prevalence (proportion infected) and intensity of infection (number of oocysts per infected mosquito) were recorded for each group. Mosquito mortality was recorded daily. Temperature and humidity were recorded every 30 minutes throughout the experiments. RESULTS Our findings indicate that apart from the effect of deltamethrin exposure, mean daily temperature during the incubation period, temperature range during the first 24 hours and on day 4 post-infectious feed had a highly significant effect on the risk of infection. Deltamethrin exposure still significantly impaired survival of kdr homozygous mosquitoes, while mean daily temperature and relative humidity during the incubation period independently affected mosquito mortality. Significant differences in survival of resistant genotypes were detected, with the lowest survival recorded in mosquitoes with heterozygote L1014S/L1014F genotype. CONCLUSIONS This study confirmed that the early part of sporogony is most affected by temperature fluctuations, while environmental factors affect mosquito survival. The impact of insecticide resistance on malaria infection and vector survival needs to be assessed separately for mosquitoes with different resistance mechanisms to fully understand its implications for currently available vector control tools and malaria transmission.
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Affiliation(s)
- Mojca Kristan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
| | | | - Jo Lines
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
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Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: trends in pyrethroid resistance during a WHO-coordinated multi-country prospective study. Parasit Vectors 2018; 11:550. [PMID: 30348209 PMCID: PMC6198431 DOI: 10.1186/s13071-018-3101-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 09/06/2018] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Increasing pyrethroid resistance has been an undesirable correlate of the rapid increase in coverage of insecticide-treated nets (ITNs) since 2000. Whilst monitoring of resistance levels has increased markedly over this period, longitudinal monitoring is still lacking, meaning the temporal and spatial dynamics of phenotypic resistance in the context of increasing ITN coverage are unclear. METHODS As part of a large WHO-co-ordinated epidemiological study investigating the impact of resistance on malaria infection, longitudinal monitoring of phenotypic resistance to pyrethroids was undertaken in 290 clusters across Benin, Cameroon, India, Kenya and Sudan. Mortality in response to pyrethroids in the major anopheline vectors in each location was recorded during consecutive years using standard WHO test procedures. Trends in mosquito mortality were examined using generalised linear mixed-effect models. RESULTS Insecticide resistance (using the WHO definition of mortality < 90%) was detected in clusters in all countries across the study period. The highest mosquito mortality (lowest resistance frequency) was consistently reported from India, in an area where ITNs had only recently been introduced. Substantial temporal and spatial variation was evident in mortality measures in all countries. Overall, a trend of decreasing mosquito mortality (increasing resistance frequency) was recorded (Odds Ratio per year: 0.79 per year (95% CI: 0.79-0.81, P < 0.001). There was also evidence that higher net usage was associated with lower mosquito mortality in some countries. DISCUSSION Pyrethroid resistance increased over the study duration in four out of five countries. Insecticide-based vector control may be compromised as a result of ever higher resistance frequencies.
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Carlier PR, Chen QH, Verma A, Wong DM, Mutunga JM, Müller J, Islam R, Shimozono AM, Tong F, Li J, Totrov M, Bloomquist JR. Select β- and γ-branched 1-alkylpyrazol-4-yl methylcarbamates exhibit high selectivity for inhibition of Anopheles gambiae versus human acetylcholinesterase. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2018; 151:32-39. [PMID: 30524149 PMCID: PMC6277143 DOI: 10.1016/j.pestbp.2018.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The widespread emergence of pyrethroid-resistant Anopheles gambiae has intensified the need to find new contact mosquitocides for indoor residual spraying and insecticide treated nets. With the goal of developing new species-selective and resistance-breaking acetylcholinesterase (AChE)-inhibiting mosquitocides, in this report we revisit the effects of carbamate substitution on aryl carbamates, and variation of the 1-alkyl group on pyrazol-4-yl methylcarbamates. Compared to aryl methylcarbamates, aryl dimethylcarbamates were found to have lower selectivity for An. gambiae AChE (AgAChE) over human AChE (hAChE), but improved tarsal contact toxicity to G3 strain An. gambiae. Molecular modeling studies suggest the lower species-selectivity of the aryl dimethylcarbamates can be attributed to a less flexible acyl pocket in AgAChE relative to hAChE. The improved tarsal contact toxicity of the aryl dimethylcarbamates relative to the corresponding methylcarbamates is attributed to a range of complementary phenomena. With respect to the pyrazol-4-yl methylcarbamates, the previously observed low An. gambiae-selectivity of compounds bearing α-branched 1-alkyl groups was improved by employing β- and γ-branched 1-alkyl groups. Compounds 22a (cyclopentylmethyl), 21a (cyclobutylmethyl), and 26a (3-methylbutyl) offer 250-fold, 120-fold, and 96-fold selectivity, respectively, for inhibition of AgAChE vs. hAChE. Molecular modeling studies suggests the high species-selectivity of these compounds can be attributed to the greater mobility of the W84 side chain in the choline-binding site of AgAChE, compared to that of W86 in hAChE. Compound 26a has reasonable contact toxicity to G3 strain An. gambiae (LC50 = 269 μg/mL) and low cross-resistance to Akron strain (LC50 = 948 μg/mL), which bears the G119S resistance mutation.
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Affiliation(s)
- Paul R Carlier
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061 USA
| | - Qiao-Hong Chen
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061 USA
| | - Astha Verma
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061 USA
| | - Dawn M Wong
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061 USA
| | - James M Mutunga
- Emerging Pathogens Institute and Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
- Department of Entomology, Virginia Tech, Blacksburg, VA 24061 USA
| | - Jasmin Müller
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061 USA
| | - Rafique Islam
- Emerging Pathogens Institute and Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Alex M Shimozono
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061 USA
| | - Fan Tong
- Department of Entomology, Virginia Tech, Blacksburg, VA 24061 USA
| | - Jianyong Li
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061 USA
| | - Max Totrov
- Molsoft LLC, 11199 Sorrento Valley Road, San Diego, California 92121, USA
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute and Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
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Onyiah AP, Ajayi IO, Dada-Adegbola HO, Adedokun BO, Balogun MS, Nguku PM, Ajumobi OO. Long-lasting insecticidal net use and asymptomatic malaria parasitaemia among household members of laboratory-confirmed malaria patients attending selected health facilities in Abuja, Nigeria, 2016: A cross-sectional survey. PLoS One 2018; 13:e0203686. [PMID: 30212496 PMCID: PMC6136754 DOI: 10.1371/journal.pone.0203686] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 08/24/2018] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION In Nigeria, malaria remains a major burden. There is the presupposition that household members could have common exposure to malaria parasite and use of long-lasting insecticidal net (LLIN) could reduce transmission. This study was conducted to identify factors associated with asymptomatic malaria parasitaemia and LLIN use among households of confirmed malaria patients in Abuja, Nigeria. METHODS A cross-sectional survey was conducted from March to August 2016 in twelve health facilities selected from three area councils in Abuja, Nigeria. Participants were selected using multi-stage sampling technique. Overall, we recruited 602 participants from 107 households linked to 107 malaria patients attending the health facilities. Data on LLIN ownership, utilization, and house characteristics were collected using a semi-structured questionnaire. Blood samples of household members were examined for malaria parasitaemia using microscopy. Data were analyzed using descriptive statistics, Chi-square, and logistic regression (α = 0.05). RESULTS Median age of respondents was 16.5 years (Interquartile range: 23 years); 55.0% were females. Proportions of households that owned and used at least one LLIN were 44.8% and 33.6%, respectively. Parasitaemia was detected in at least one family member of 102 (95.3%) index malaria patients. Prevalence of asymptomatic malaria parasitaemia among study participants was 421/602 (69.9%). No association was found between individual LLIN use and malaria parasitaemia (odds ratio: 0.9, 95% confidence interval (95%CI): 0.6-1.3) among study participants. Having bushes around the homes was associated with having malaria parasitaemia (adjusted OR (aOR): 2.7, 95%CI: 1.7-4.2) and less use of LLIN (aOR: 0.4, 95%CI: 0.2-0.9). Living in Kwali (aOR: 0.1, 95% CI: 0.0-0.2) was associated with less use of LLIN. CONCLUSION High prevalence of asymptomatic malaria and low use of LLIN among household members of malaria patients portend the risk of intra-household common source of malaria transmission. We recommend household health education on LLIN use and environmental management. Study to explore the role of preventive treatment of household members of confirmed malaria patient in curbing transmission is suggested. Strategies promoting LLIN use need to be intensified in Kwali.
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Affiliation(s)
- Amaka Pamela Onyiah
- Nigeria Field Epidemiology and Laboratory Training Programme, Abuja, FCT, Nigeria
- Department of Epidemiology and Medical Statistics, University of Ibadan, Ibadan, Oyo State, Nigeria
| | - IkeOluwapo O. Ajayi
- Nigeria Field Epidemiology and Laboratory Training Programme, Abuja, FCT, Nigeria
- Department of Epidemiology and Medical Statistics, University of Ibadan, Ibadan, Oyo State, Nigeria
| | - Hannah O. Dada-Adegbola
- Department of Medical Microbiology and Parasitology, University of Ibadan, Ibadan, Oyo State, Nigeria
| | - Babatunde O. Adedokun
- Department of Epidemiology and Medical Statistics, University of Ibadan, Ibadan, Oyo State, Nigeria
| | - Muhammad S. Balogun
- Nigeria Field Epidemiology and Laboratory Training Programme, Abuja, FCT, Nigeria
| | - Patrick M. Nguku
- Nigeria Field Epidemiology and Laboratory Training Programme, Abuja, FCT, Nigeria
| | - Olufemi O. Ajumobi
- Nigeria Field Epidemiology and Laboratory Training Programme, Abuja, FCT, Nigeria
- National Malaria Elimination Programme, Abuja, FCT, Nigeria
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Kleinschmidt I, Bradley J, Knox TB, Mnzava AP, Kafy HT, Mbogo C, Ismail BA, Bigoga JD, Adechoubou A, Raghavendra K, Cook J, Malik EM, Nkuni ZJ, Macdonald M, Bayoh N, Ochomo E, Fondjo E, Awono-Ambene HP, Etang J, Akogbeto M, Bhatt RM, Chourasia MK, Swain DK, Kinyari T, Subramaniam K, Massougbodji A, Okê-Sopoh M, Ogouyemi-Hounto A, Kouambeng C, Abdin MS, West P, Elmardi K, Cornelie S, Corbel V, Valecha N, Mathenge E, Kamau L, Lines J, Donnelly MJ. Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: a WHO-coordinated, prospective, international, observational cohort study. THE LANCET. INFECTIOUS DISEASES 2018; 18:640-649. [PMID: 29650424 PMCID: PMC5968369 DOI: 10.1016/s1473-3099(18)30172-5] [Citation(s) in RCA: 148] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 02/13/2018] [Accepted: 02/26/2018] [Indexed: 11/22/2022]
Abstract
BACKGROUND Scale-up of insecticide-based interventions has averted more than 500 million malaria cases since 2000. Increasing insecticide resistance could herald a rebound in disease and mortality. We aimed to investigate whether insecticide resistance was associated with loss of effectiveness of long-lasting insecticidal nets and increased malaria disease burden. METHODS This WHO-coordinated, prospective, observational cohort study was done at 279 clusters (villages or groups of villages in which phenotypic resistance was measurable) in Benin, Cameroon, India, Kenya, and Sudan. Pyrethroid long-lasting insecticidal nets were the principal form of malaria vector control in all study areas; in Sudan this approach was supplemented by indoor residual spraying. Cohorts of children from randomly selected households in each cluster were recruited and followed up by community health workers to measure incidence of clinical malaria and prevalence of infection. Mosquitoes were assessed for susceptibility to pyrethroids using the standard WHO bioassay test. Country-specific results were combined using meta-analysis. FINDINGS Between June 2, 2012, and Nov 4, 2016, 40 000 children were enrolled and assessed for clinical incidence during 1·4 million follow-up visits. 80 000 mosquitoes were assessed for insecticide resistance. Long-lasting insecticidal net users had lower infection prevalence (adjusted odds ratio [OR] 0·63, 95% CI 0·51-0·78) and disease incidence (adjusted rate ratio [RR] 0·62, 0·41-0·94) than did non-users across a range of resistance levels. We found no evidence of an association between insecticide resistance and infection prevalence (adjusted OR 0·86, 0·70-1·06) or incidence (adjusted RR 0·89, 0·72-1·10). Users of nets, although significantly better protected than non-users, were nevertheless subject to high malaria infection risk (ranging from an average incidence in net users of 0·023, [95% CI 0·016-0·033] per person-year in India, to 0·80 [0·65-0·97] per person year in Kenya; and an average infection prevalence in net users of 0·8% [0·5-1·3] in India to an average infection prevalence of 50·8% [43·4-58·2] in Benin). INTERPRETATION Irrespective of resistance, populations in malaria endemic areas should continue to use long-lasting insecticidal nets to reduce their risk of infection. As nets provide only partial protection, the development of additional vector control tools should be prioritised to reduce the unacceptably high malaria burden. FUNDING Bill & Melinda Gates Foundation, UK Medical Research Council, and UK Department for International Development.
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Affiliation(s)
- Immo Kleinschmidt
- MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK; School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
| | - John Bradley
- MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | | | | | - Hmooda Toto Kafy
- Federal Ministry of Health, Khartoum, Sudan; School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia
| | - Charles Mbogo
- KEMRI Centre for Geographic Medicine Research Coast, Kilifi, Kenya
| | - Bashir Adam Ismail
- School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia; Khartoum Malaria Free Initiative, Khartoum, Sudan
| | - Jude D Bigoga
- National Reference Unit (NRU) for Vector Control, The Biotechnology Center, University of Yaoundé I, Yaoundé, Cameroon
| | - Alioun Adechoubou
- Programme National de Lutte contre le Paludisme (PNLP), Ministère de la Santé, Cotonou, Benin
| | - Kamaraju Raghavendra
- National Institute of Malaria Research, Indian Council of Medical Research, Department of Health Research, New Delhi, India
| | - Jackie Cook
- MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Elfatih M Malik
- University of Khartoum, Faculty of Medicine, Department of Community Medicine, Khartoum, Sudan
| | | | | | - Nabie Bayoh
- KEMRI/CDC Research and Public Health Collaboration, Kisumu, Kenya
| | - Eric Ochomo
- KEMRI/CDC Research and Public Health Collaboration, Kisumu, Kenya
| | - Etienne Fondjo
- National Malaria Control Program, Ministry of Public Health, Yaoundé, Cameroon
| | - Herman Parfait Awono-Ambene
- Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
| | - Josiane Etang
- Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC), Yaoundé, Cameroon; Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon
| | - Martin Akogbeto
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Rajendra M Bhatt
- National Institute of Malaria Research, Indian Council of Medical Research, Department of Health Research, New Delhi, India
| | - Mehul Kumar Chourasia
- National Institute of Malaria Research, Indian Council of Medical Research, Department of Health Research, New Delhi, India
| | - Dipak K Swain
- National Institute of Malaria Research, Indian Council of Medical Research, Department of Health Research, New Delhi, India
| | - Teresa Kinyari
- University of Nairobi, School of Medicine, College of Health Sciences, Department of Medical Physiology, Nairobi, Kenya
| | | | | | - Mariam Okê-Sopoh
- Programme National de Lutte contre le Paludisme (PNLP), Ministère de la Santé, Cotonou, Benin
| | | | - Celestin Kouambeng
- National Malaria Control Program, Ministry of Public Health, Yaoundé, Cameroon
| | | | - Philippa West
- MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | | | - Sylvie Cornelie
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), CNRS, University of Montpellier, Montpellier, France
| | - Vincent Corbel
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), CNRS, University of Montpellier, Montpellier, France
| | - Neena Valecha
- National Institute of Malaria Research, Indian Council of Medical Research, Department of Health Research, New Delhi, India
| | - Evan Mathenge
- KEMRI Eastern and Southern Africa Centre of International Parasite Control, Nairobi, Kenya
| | - Luna Kamau
- KEMRI Centre for Biotechnology and Research Development, Nairobi, Kenya
| | - Jonathan Lines
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Martin James Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK; Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK
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Protopopoff N, Mosha JF, Lukole E, Charlwood JD, Wright A, Mwalimu CD, Manjurano A, Mosha FW, Kisinza W, Kleinschmidt I, Rowland M. Effectiveness of a long-lasting piperonyl butoxide-treated insecticidal net and indoor residual spray interventions, separately and together, against malaria transmitted by pyrethroid-resistant mosquitoes: a cluster, randomised controlled, two-by-two factorial design trial. Lancet 2018; 391:1577-1588. [PMID: 29655496 PMCID: PMC5910376 DOI: 10.1016/s0140-6736(18)30427-6] [Citation(s) in RCA: 239] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 02/13/2018] [Accepted: 02/13/2018] [Indexed: 11/29/2022]
Abstract
BACKGROUND Progress in malaria control is under threat by wide-scale insecticide resistance in malaria vectors. Two recent vector control products have been developed: a long-lasting insecticidal net that incorporates a synergist piperonyl butoxide (PBO) and a long-lasting indoor residual spraying formulation of the insecticide pirimiphos-methyl. We evaluated the effectiveness of PBO long-lasting insecticidal nets versus standard long-lasting insecticidal nets as single interventions and in combination with the indoor residual spraying of pirimiphos-methyl. METHODS We did a four-group cluster randomised controlled trial using a two-by-two factorial design of 48 clusters derived from 40 villages in Muleba (Kagera, Tanzania). We randomly assigned these clusters using restricted randomisation to four groups: standard long-lasting insecticidal nets, PBO long-lasting insecticidal nets, standard long-lasting insecticidal nets plus indoor residual spraying, or PBO long-lasting insecticidal nets plus indoor residual spraying. Both standard and PBO nets were distributed in 2015. Indoor residual spraying was applied only once in 2015. We masked the inhabitants of each cluster to the type of nets received, as well as field staff who took blood samples. Neither the investigators nor the participants were masked to indoor residual spraying. The primary outcome was the prevalence of malaria infection in children aged 6 months to 14 years assessed by cross-sectional surveys at 4, 9, 16, and 21 months after intervention. The endpoint for assessment of indoor residual spraying was 9 months and PBO long-lasting insecticidal nets was 21 months. This trial is registered with ClinicalTrials.gov, number NCT02288637. FINDINGS 7184 (68·0%) of 10 560 households were selected for post-intervention survey, and 15 469 (89·0%) of 17 377 eligible children from the four surveys were included in the intention-to-treat analysis. Of the 878 households visited in the two indoor residual spraying groups, 827 (94%) had been sprayed. Reported use of long-lasting insecticidal nets, across all groups, was 15 341 (77·3%) of 19 852 residents after 1 year, decreasing to 12 503 (59·2%) of 21 105 in the second year. Malaria infection prevalence after 9 months was lower in the two groups that received PBO long-lasting insecticidal nets than in the two groups that received standard long-lasting insecticidal nets (531 [29%] of 1852 children vs 767 [42%] of 1809; odds ratio [OR] 0·37, 95% CI 0·21-0·65; p=0·0011). At the same timepoint, malaria prevalence in the two groups that received indoor residual spraying was lower than in groups that did not receive indoor residual spraying (508 [28%] of 1846 children vs 790 [44%] of 1815; OR 0·33, 95% CI 0·19-0·55; p<0·0001) and there was evidence of an interaction between PBO long-lasting insecticidal nets and indoor residual spraying (OR 2·43, 95% CI 1·19-4·97; p=0·0158), indicating redundancy when combined. The PBO long-lasting insecticidal net effect was sustained after 21 months with a lower malaria prevalence than the standard long-lasting insecticidal net (865 [45%] of 1930 children vs 1255 [62%] of 2034; OR 0·40, 0·20-0·81; p=0·0122). INTERPRETATION The PBO long-lasting insecticidal net and non-pyrethroid indoor residual spraying interventions showed improved control of malaria transmission compared with standard long-lasting insecticidal nets where pyrethroid resistance is prevalent and either intervention could be deployed to good effect. As a result, WHO has since recommended to increase coverage of PBO long-lasting insecticidal nets. Combining indoor residual spraying with pirimiphos-methyl and PBO long-lasting insecticidal nets provided no additional benefit compared with PBO long-lasting insecticidal nets alone or standard long-lasting insecticidal nets plus indoor residual spraying. FUNDING UK Department for International Development, Medical Research Council, and Wellcome Trust.
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Affiliation(s)
- Natacha Protopopoff
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
| | - Jacklin F Mosha
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Eliud Lukole
- Pan-African Malaria Vector Research Consortium, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Jacques D Charlwood
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Alexandra Wright
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Charles D Mwalimu
- Ministry of Health Community Development Gender Elderly and Children, National Malaria Control Program, Dar es Salaam, Tanzania
| | - Alphaxard Manjurano
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Franklin W Mosha
- Pan-African Malaria Vector Research Consortium, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - William Kisinza
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Immo Kleinschmidt
- MRC Tropical Epidemiology Group, London School of Hygiene & Tropical Medicine, London, UK; School of Pathology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
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Measuring the effect of insecticide resistance: are we making progress? THE LANCET. INFECTIOUS DISEASES 2018; 18:586-588. [PMID: 29650425 DOI: 10.1016/s1473-3099(18)30216-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 03/12/2018] [Indexed: 11/22/2022]
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Dreyer SM, Morin KJ, Vaughan JA. Differential susceptibilities of Anopheles albimanus and Anopheles stephensi mosquitoes to ivermectin. Malar J 2018; 17:148. [PMID: 29615055 PMCID: PMC5883420 DOI: 10.1186/s12936-018-2296-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/24/2018] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Vector control is a crucial element of anti-malaria campaigns and works best when there is a thorough knowledge of the biology and behaviour of the Anopheles vector species responsible for transmitting malaria within a given locale. With the push to eradicate malaria stronger than ever, there is a growing need to develop and deploy control strategies that exploit the behavioural attributes of local vector species. This is especially true in regions where the vectors are exophagic (i.e., prefer to bite outdoors), exophilic (i.e., prefer to remain outdoors), and zoophagic (i.e., as likely to feed on non-humans as humans). One promising strategy targeting vectors with these behavioural traits is the administration of avermectin-based endectocides, such as ivermectin, to humans and livestock. When ingested in a blood meal, ivermectin has been shown to reduce mosquito survivorship and fecundity in a number of Anopheles species. In this study, the relative toxicity of ivermectin was compared between two zoophagic, exophilic malaria vectors-Anopheles albimanus and Anopheles stephensi. RESULTS Toxicity of ivermectin was assessed using membrane feedings, intrathoracic injections, and mosquito feedings on treated mice. When ingested in a blood meal, ivermectin was much less toxic to An. albimanus (4-day oral LC50 = 1468 ng/ml) than to An. stephensi (4-day oral LC50 = 7 ng/ml). However when injected into the haemocoel of An. albimanus, ivermectin was much more toxic (3-day parenteral LC50 = 188 ng/ml). Because the molecular targets of ivermectin (i.e., glutamate-gated chloride channels) reside outside the midgut in nerves and muscles, this suggests that ingested ivermectin was not readily absorbed across the midgut of An. albimanus. In contrast, ivermectin was considerably more toxic to An. stephensi when ingested (4-day oral LC50 = 7 ng/ml) than when injected (3-day parenteral LC50 = 49 ng/ml). This suggests that metabolic by-products from the digestion of ivermectin may play a role in the oral toxicity of ivermectin to An. stephensi. Blood meal digestion and subsequent oviposition rates were significantly hindered in both species by ingested ivermectin but only at concentrations at or above their respective oral LC50 concentrations. To test mosquitocidal activity of ivermectin in a live host system, two groups of three mice each received subcutaneous injections of either ivermectin (600 µg/kg BW) or saline (control). One day after injection, the ivermectin-treated mice (n = 3) exhibited significant mosquitocidal activity against both An. stephensi (85% mortality vs 0% in control-fed) and, to a lesser degree, An. albimanus (44% mortality vs 11% in control-fed). At 3 days, the mosquitocidal activity of ivermectin-treated mice waned and was effective only against An. stephensi (31% mortality vs 3% in control-fed). CONCLUSIONS Ivermectin was not uniformly toxic to both Anopheles species. Previous studies indicate that ivermectin is a good choice of endectocide to use against malaria vectors in southeast Asia and Africa. However, these data suggest that ivermectin may not be the optimal endectocide to use in Central America or the Caribbean where An. albimanus is a major malaria vector species. If endectocides are to be used to help eradicate malaria, then additional efficacy data will be needed to define the activity of specific endectocides against the major malaria vector species of the world.
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Affiliation(s)
- Staci M Dreyer
- Department of Biology, University of North Dakota, 10 Cornell Street, Stop 9019, Grand Forks, ND, 58202-9019, USA
| | - Kelsey J Morin
- Department of Biology, University of North Dakota, 10 Cornell Street, Stop 9019, Grand Forks, ND, 58202-9019, USA
| | - Jefferson A Vaughan
- Department of Biology, University of North Dakota, 10 Cornell Street, Stop 9019, Grand Forks, ND, 58202-9019, USA.
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Thiaw O, Doucouré S, Sougoufara S, Bouganali C, Konaté L, Diagne N, Faye O, Sokhna C. Investigating insecticide resistance and knock-down resistance (kdr) mutation in Dielmo, Senegal, an area under long lasting insecticidal-treated nets universal coverage for 10 years. Malar J 2018; 17:123. [PMID: 29566682 PMCID: PMC5863856 DOI: 10.1186/s12936-018-2276-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Accepted: 03/15/2018] [Indexed: 11/10/2022] Open
Abstract
Background The use of insecticides, through indoor residual spraying and long-lasting insecticide-treated nets (LLINs), is essential to control malaria vectors. However, the sustainability of these tools is challenged by the spread of insecticide resistance in Anopheles mosquitoes. This study was conducted to assess the susceptibility to insecticides and to determine the resistance mechanisms in malaria vectors in Dielmo, a rural area of western Senegal where LLINs were introduced a decade ago. Methods CDC bottle bioassays were used to determine the susceptibility of 2–5 day-old unfed Anopheles gambiae s.l. females to alphacypermethrin (12.5 µg/bottle), deltamethrin (12.5 µg/bottle), etofenprox (12.5 µg/bottle), lambdacyhalothrin (12.5 µg/bottle), permethrin (21.5 µg/bottle), DDT (100 µg/bottle), bendiocarb (12.5 µg/bottle), pirimiphos-methyl (20 µg/bottle) and fenitrothion (50 µg/bottle). The involvement of glutathione-S-transferases (GSTs) in insecticide resistance was assessed using a synergist, etacrynic acid (EA, 80 µg/bottle). Polymerase chain reaction (PCR) was used to investigate the presence of ‘knock-down resistance (kdr)’ mutation and to identify sibling species within the An. gambiae complex. Results CDC bottle bioassays showed that mosquitoes were fully susceptible to lambdacyhalothrin, bendiocarb and fenitrothion. Overall, mortality rates of 97, 94.6, 93.5, 92.1, and 90.1% were, respectively, observed for permethrin, deltamethrin, pirimiphos-methyl, etofenprox and alphacypermethrin. Resistance to DDT was observed, with a mortality rate of 62%. The use of EA significantly improved the susceptibility of An. gambiae s.l. to DDT by inhibiting GSTs (p = 0.03). PCR revealed that Anopheles arabiensis was the predominant species (91.3%; IC 95 86.6–94%) within An. gambiae complex from Dielmo, followed by Anopheles coluzzii (5.4%; IC 95 2.7–8.1%) and Anopheles gambiae s.s. (3.3%; IC 95 0.6–5.9%). Both 1014F and 1014S alleles were found in An. arabiensis population with frequencies of 0.08 and 0.361, respectively, and 0.233 and 0.133, respectively in An. coluzzii. In An. gambiae s.s. population, only kdr L1014F mutation was detected, with a frequency of 0.167. It was observed that some individual mosquitoes carried both alleles, with 19 specimens recorded for An. arabiensis and 2 for An. coluzzii. The presence of L1014F and L1014S alleles were not associated with resistance to pyrethroids and DDT in An. arabiensis. Conclusions The co-occurrence of 1014F and 1014S alleles and the probable involvement of GSTs enzymes in insecticide resistance in An. gambiae s.l. should prompt the local vector programme to implement non-pyrethroid/DDT insecticides alternatives.
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Affiliation(s)
- Omar Thiaw
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal.,Laboratoire d'Ecologie Vectorielle et Parasitaire (LEVP), Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Souleymane Doucouré
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Seynabou Sougoufara
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Charles Bouganali
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Lassana Konaté
- Laboratoire d'Ecologie Vectorielle et Parasitaire (LEVP), Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Nafissatou Diagne
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Ousmane Faye
- Laboratoire d'Ecologie Vectorielle et Parasitaire (LEVP), Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Cheikh Sokhna
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal.
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Impact of insecticide resistance in Anopheles arabiensis on malaria incidence and prevalence in Sudan and the costs of mitigation. Proc Natl Acad Sci U S A 2017; 114:E11267-E11275. [PMID: 29229808 PMCID: PMC5748194 DOI: 10.1073/pnas.1713814114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Emerging insecticide resistance in malaria vectors could presage a catastrophic rebound in malaria morbidity and mortality. In areas of moderate levels of resistance to pyrethroids, long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) with a carbamate insecticide were significantly more effective than IRS with pyrethroid insecticide. The impact on the effectiveness of LLINs could not be quantified. The incremental cost of using a carbamate insecticide to which vectors are susceptible was US $0.65 per person protected per year, which is considered acceptable by international standards. While the WHO recommends that different interventions, where possible, should use different insecticide classes, these data alone should not be used as the basis for a policy change in vector control interventions. Insecticide-based interventions have contributed to ∼78% of the reduction in the malaria burden in sub-Saharan Africa since 2000. Insecticide resistance in malaria vectors could presage a catastrophic rebound in disease incidence and mortality. A major impediment to the implementation of insecticide resistance management strategies is that evidence of the impact of resistance on malaria disease burden is limited. A cluster randomized trial was conducted in Sudan with pyrethroid-resistant and carbamate-susceptible malaria vectors. Clusters were randomly allocated to receive either long-lasting insecticidal nets (LLINs) alone or LLINs in combination with indoor residual spraying (IRS) with a pyrethroid (deltamethrin) insecticide in the first year and a carbamate (bendiocarb) insecticide in the two subsequent years. Malaria incidence was monitored for 3 y through active case detection in cohorts of children aged 1 to <10 y. When deltamethrin was used for IRS, incidence rates in the LLIN + IRS arm and the LLIN-only arm were similar, with the IRS providing no additional protection [incidence rate ratio (IRR) = 1.0 (95% confidence interval [CI]: 0.36–3.0; P = 0.96)]. When bendiocarb was used for IRS, there was some evidence of additional protection [interaction IRR = 0.55 (95% CI: 0.40–0.76; P < 0.001)]. In conclusion, pyrethroid resistance may have had an impact on pyrethroid-based IRS. The study was not designed to assess whether resistance had an impact on LLINs. These data alone should not be used as the basis for any policy change in vector control interventions.
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Strengthening Evidence in Cleft and Craniofacial Surgery. J Craniofac Surg 2017; 29:302-303. [PMID: 29135729 DOI: 10.1097/scs.0000000000004101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Wehner S, Stieglbauer G, Traoré C, Sie A, Becher H, Müller O. Malaria incidence during early childhood in rural Burkina Faso: Analysis of a birth cohort protected with insecticide-treated mosquito nets. Acta Trop 2017; 175:78-83. [PMID: 28336268 DOI: 10.1016/j.actatropica.2017.03.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 03/12/2017] [Accepted: 03/16/2017] [Indexed: 10/19/2022]
Abstract
BACKGROUND Even in the high transmission areas of sub-Saharan Africa (SSA), the incidence of falciparum malaria varies greatly depending on factors such as age, rainfall pattern, distance to breeding places, quality of houses, and existing vector control measures. Insecticide-treated mosquito nets (ITN) have now become the vector control standard in nearly all of SSA. This study aims to describe and analyse the incidence of malaria in a cohort of young children protected with ITN in rural West Africa. METHODS Data of a subsample from a large community trial in rural north-western Burkina Faso consisting of 420 children were analysed. The main aim of the trial was to evaluate the long-term effects of ITNs in two groups of new-borns; Group A was protected with ITN from birth onwards while Group B was protected only from month six onwards. The primary objective of this study was to describe malaria incidence in detail with an analysis of the impact of potentially relevant determinants of malaria incidence, in particular age, sex, ITN protection, village, month and season as secondary objective. Bivariate negative binomial regression analysis was used to calculate incidence rate ratios of malaria incidence. Moreover, relevant variables were included in a multivariate negative binomial regression model to examine possible risk factors for malaria. RESULTS Out of the 420 study children 387 (92.1%) developed a total of 1822 falciparum malaria episodes; the malaria incidence rate was 7.6 per 1000 child days. Group A children had lower malaria incidence rates compared to group B, but only in early infancy. Malaria incidence varied significantly between villages and increased with age, but no sex-specific differences were observed; these findings were confirmed in the multi-variate analysis. Malaria incidence peaked sharply towards the end of the rainy season in September but there were no differences in the seasonal pattern by study group. CONCLUSIONS The study, carried out in a high-transmission West African area, shows that malaria incidence remains high in spite of maximum ITN coverage.
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Kesteman T, Randrianarivelojosia M, Rogier C. The protective effectiveness of control interventions for malaria prevention: a systematic review of the literature. F1000Res 2017; 6:1932. [PMID: 29259767 PMCID: PMC5721947 DOI: 10.12688/f1000research.12952.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/27/2017] [Indexed: 12/22/2022] Open
Abstract
Background: Thanks to a considerable increase in funding, malaria control interventions (MCI) whose efficacy had been demonstrated by controlled trials have been largely scaled up during the last decade. Nevertheless, it was not systematically investigated whether this efficacy had been preserved once deployed on the field. Therefore, we sought the literature to assess the disparities between efficacy and effectiveness and the effort to measure the protective effectiveness (PE) of MCI. Methods: The PubMed database was searched for references with keywords related to malaria, to control interventions for prevention and to study designs that allow for the measure of the PE against parasitemia or against clinical outcomes. Results: Our search retrieved 1423 references, and 162 articles were included in the review. Publications were scarce before the year 2000 but dramatically increased afterwards. Bed nets was the MCI most studied (82.1%). The study design most used was a cross-sectional study (65.4%). Two thirds (67.3%) were conducted at the district level or below, and the majority (56.8%) included only children even if the MCI didn’t target only children. Not all studies demonstrated a significant PE from exposure to MCI: 60.6% of studies evaluating bed nets, 50.0% of those evaluating indoor residual spraying, and 4/8 showed an added PE of using both interventions as compared with one only; this proportion was 62.5% for intermittent preventive treatment of pregnant women, and 20.0% for domestic use of insecticides. Conclusions: This review identified numerous local findings of low, non-significant PE –or even the absence of a protective effect provided by these MCIs. The identification of such failures in the effectiveness of MCIs advocates for the investigation of the causes of the problem found. Ideal evaluations of the PE of MCIs should incorporate both a large representativeness and an evaluation of the PE stratified by subpopulations.
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Affiliation(s)
- Thomas Kesteman
- Fondation Mérieux, Lyon, France.,Malaria Research Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar
| | | | - Christophe Rogier
- Malaria Research Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar.,Ecole doctorale Sciences de la vie et de l'environnement, Université d'Antananarivo, Antananarivo, Madagascar.,Institute for Biomedical Research of the French Armed Forces (IRBA), Brétigny-Sur-Orge , France.,Unité de recherche sur les maladies infectieuses et tropicales émergentes - (URMITE), Marseille, France
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Minta AA, Landman KZ, Mwandama DA, Shah MP, Eng JLV, Sutcliffe JF, Chisaka J, Lindblade KA, Mathanga DP, Steinhardt LC. The effect of holes in long-lasting insecticidal nets on malaria in Malawi: results from a case-control study. Malar J 2017; 16:394. [PMID: 28969632 PMCID: PMC5625742 DOI: 10.1186/s12936-017-2033-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 09/18/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are a cornerstone of malaria prevention. Holes develop in LLINs over time and compromise their physical integrity, but how holes affect malaria transmission risk is not well known. METHODS After a nationwide mass LLIN distribution in July 2012, a study was conducted to assess the relationship between LLIN damage and malaria. From March to September 2013, febrile children ages 6-59 months who consistently slept under LLINs (every night for 2 weeks before illness onset) were enrolled in a case-control study at Machinga District Hospital outpatient department. Cases were positive for Plasmodium falciparum asexual parasites by microscopy while controls were negative. Digital photographs of participants' LLINs were analysed using an image-processing programme to measure holes. Total hole area was classified by quartiles and according to the World Health Organization's proportionate hole index (pHI) cut-offs [< 79 cm2 (good), 80-789 cm2 (damaged), and > 790 cm2 (too torn)]. Number of holes by location and size, and total hole area, were compared between case and control LLINs using non-parametric analyses and logistic regression. RESULTS Of 248 LLINs analysed, 97 (39%) were from cases. Overall, 86% of LLINs had at least one hole. The median number of holes of any size was 9 [interquartile range (IQR) 3, 22], and most holes were located in the lower halves of the nets [median 7 (IQR 2, 16)]. There were no differences in number or location of holes between LLINs used by cases and controls. The median total hole area was 10 cm2 (IQR 2, 125) for control LLINs and 8 cm2 (IQR 2, 47) for case LLINs (p = 0.10). Based on pHI, 109 (72%) control LLINs and 83 (86%) case LLINs were in "good" condition. Multivariable modeling showed no association between total hole area and malaria, controlling for child age, caregiver education, and iron versus thatched roof houses. CONCLUSIONS LLIN holes were not associated with increased odds of malaria in this study. However, most of the LLINs were in relatively good condition 1 year after distribution. Future studies should examine associations between LLIN holes and malaria risk with more damaged nets.
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Affiliation(s)
- Anna A Minta
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA. .,Epidemic Intelligence Service, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA.
| | - Keren Z Landman
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA
| | - Dyson A Mwandama
- Malaria Alert Centre, University of Malawi College of Medicine, Private Bag 360, Blantyre, Malawi
| | - Monica P Shah
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA
| | - Jodi L Vanden Eng
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA
| | - James F Sutcliffe
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA
| | - Joseph Chisaka
- Malaria Alert Centre, University of Malawi College of Medicine, Private Bag 360, Blantyre, Malawi
| | - Kim A Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA
| | - Don P Mathanga
- Malaria Alert Centre, University of Malawi College of Medicine, Private Bag 360, Blantyre, Malawi
| | - Laura C Steinhardt
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA
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Hennessee I, Chinkhumba J, Briggs-Hagen M, Bauleni A, Shah MP, Chalira A, Moyo D, Dodoli W, Luhanga M, Sande J, Ali D, Gutman J, Lindblade KA, Njau J, Mathanga DP. Household costs among patients hospitalized with malaria: evidence from a national survey in Malawi, 2012. Malar J 2017; 16:395. [PMID: 28969643 PMCID: PMC5625606 DOI: 10.1186/s12936-017-2038-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 09/21/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND With 71% of Malawians living on < $1.90 a day, high household costs associated with severe malaria are likely a major economic burden for low income families and may constitute an important barrier to care seeking. Nevertheless, few efforts have been made to examine these costs. This paper describes household costs associated with seeking and receiving inpatient care for malaria in health facilities in Malawi. METHODS A cross-sectional survey was conducted in a representative nationwide sample of 36 health facilities providing inpatient treatment for malaria from June-August, 2012. Patients admitted at least 12 h before study team visits who had been prescribed an antimalarial after admission were eligible to provide cost information for their malaria episode, including care seeking at previous health facilities. An ingredients-based approach was used to estimate direct costs. Indirect costs were estimated using a human capital approach. Key drivers of total household costs for illness episodes resulting in malaria admission were assessed by fitting a generalized linear model, accounting for clustering at the health facility level. RESULTS Out of 100 patients who met the eligibility criteria, 80 (80%) provided cost information for their entire illness episode to date and were included: 39% of patients were under 5 years old and 75% had sought care for the malaria episode at other facilities prior to coming to the current facility. Total household costs averaged $17.48 per patient; direct and indirect household costs averaged $7.59 and $9.90, respectively. Facility management type, household distance from the health facility, patient age, high household wealth, and duration of hospital stay were all significant drivers of overall costs. CONCLUSIONS Although malaria treatment is supposed to be free in public health facilities, households in Malawi still incur high direct and indirect costs for malaria illness episodes that result in hospital admission. Finding ways to minimize the economic burden of inpatient malaria care is crucial to protect households from potentially catastrophic health expenditures.
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Affiliation(s)
- Ian Hennessee
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | | | - Melissa Briggs-Hagen
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Andy Bauleni
- Malaria Alert Center, Malawi College of Medicine, Blantyre, Malawi
| | - Monica P. Shah
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Alfred Chalira
- National Malaria Control Programme, Malawi Ministry of Health, Lilongwe, Malawi
| | - Dubulao Moyo
- National Malaria Control Programme, Malawi Ministry of Health, Lilongwe, Malawi
| | | | - Misheck Luhanga
- National Malaria Control Programme, Malawi Ministry of Health, Lilongwe, Malawi
| | - John Sande
- National Malaria Control Programme, Malawi Ministry of Health, Lilongwe, Malawi
| | - Doreen Ali
- National Malaria Control Programme, Malawi Ministry of Health, Lilongwe, Malawi
| | - Julie Gutman
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Kim A. Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Joseph Njau
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Don P. Mathanga
- Malaria Alert Center, Malawi College of Medicine, Blantyre, Malawi
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Alout H, Roche B, Dabiré RK, Cohuet A. Consequences of insecticide resistance on malaria transmission. PLoS Pathog 2017; 13:e1006499. [PMID: 28880906 PMCID: PMC5589250 DOI: 10.1371/journal.ppat.1006499] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Affiliation(s)
- Haoues Alout
- Institut des Sciences de l’Evolution de Montpellier, CNRS, IRD, University of Montpellier, Montpellier, France
| | - Benjamin Roche
- Institut de recherche pour le développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Montpellier, France
- UMI IRD/UPMC 209, Unité de Modélisation Mathématique et Informatique des Sytèmes Complexes (UMMISCO lab), Bondy, France
| | - Roch Kounbobr Dabiré
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
| | - Anna Cohuet
- Institut de recherche pour le développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Montpellier, France
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48
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Ochomo E, Chahilu M, Cook J, Kinyari T, Bayoh NM, West P, Kamau L, Osangale A, Ombok M, Njagi K, Mathenge E, Muthami L, Subramaniam K, Knox T, Mnavaza A, Donnelly MJ, Kleinschmidt I, Mbogo C. Insecticide-Treated Nets and Protection against Insecticide-Resistant Malaria Vectors in Western Kenya. Emerg Infect Dis 2017; 23:758-764. [PMID: 28418293 PMCID: PMC5403037 DOI: 10.3201/eid2305.161315] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Insecticide resistance might reduce the efficacy of malaria vector control. In 2013 and 2014, malaria vectors from 50 villages, of varying pyrethroid resistance, in western Kenya were assayed for resistance to deltamethrin. Long-lasting insecticide-treated nets (LLIN) were distributed to households at universal coverage. Children were recruited into 2 cohorts, cleared of malaria-causing parasites, and tested every 2 weeks for reinfection. Infection incidence rates for the 2 cohorts were 2.2 (95% CI 1.9–2.5) infections/person-year and 2.8 (95% CI 2.5–3.0) infections/person-year. LLIN users had lower infection rates than non-LLIN users in both low-resistance (rate ratio 0.61, 95% CI 0.42–0.88) and high-resistance (rate ratio 0.55, 95% CI 0.35–0.87) villages (p = 0.63). The association between insecticide resistance and infection incidence was not significant (p = 0.99). Although the incidence of infection was high among net users, LLINs provided significant protection (p = 0.01) against infection with malaria parasite regardless of vector insecticide resistance.
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49
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Bradley J, Ogouyèmi-Hounto A, Cornélie S, Fassinou J, de Tove YSS, Adéothy AA, Tokponnon FT, Makoutode P, Adechoubou A, Legba T, Houansou T, Kinde-Gazard D, Akogbeto MC, Massougbodji A, Knox TB, Donnelly M, Kleinschmidt I. Insecticide-treated nets provide protection against malaria to children in an area of insecticide resistance in Southern Benin. Malar J 2017; 16:225. [PMID: 28549431 PMCID: PMC5446701 DOI: 10.1186/s12936-017-1873-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 05/23/2017] [Indexed: 11/22/2022] Open
Abstract
Background Malaria control is heavily reliant on insecticides, especially pyrethroids. Resistance of mosquitoes to insecticides may threaten the effectiveness of insecticide-based vector control and lead to a resurgence of malaria in Africa. Methods In 21 villages in Southern Benin with high levels of insecticide resistance, the resistance status of local vectors was measured at the same time as the prevalence of malaria infection in resident children. Results Children who used LLINs had lower levels of malaria infection [odds ratio = 0.76 (95% CI 0.59, 0.98, p = 0.033)]. There was no evidence that the effectiveness of nets was different in high and low resistance locations (p = 0.513). There was no association between village level resistance and village level malaria prevalence (p = 0.999). Conclusions LLINs continue to offer individual protection against malaria infection in an area of high resistance. Insecticide resistance is not a reason to stop efforts to increase coverage of LLINs in Africa.
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Affiliation(s)
- John Bradley
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
| | - Aurore Ogouyèmi-Hounto
- Unité d'Enseignement et de Recherche en Parasitologie-Mycologie de la Faculté des Sciences de la Santé de Cotonou, Cotonou, Benin
| | - Sylvie Cornélie
- Institut Régional de développement/Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Jacob Fassinou
- Unité d'Enseignement et de Recherche en Parasitologie-Mycologie de la Faculté des Sciences de la Santé de Cotonou, Cotonou, Benin
| | - Yolande Sissinto Savi de Tove
- Unité d'Enseignement et de Recherche en Parasitologie-Mycologie de la Faculté des Sciences de la Santé de Cotonou, Cotonou, Benin
| | - Adicath Adéola Adéothy
- Unité d'Enseignement et de Recherche en Parasitologie-Mycologie de la Faculté des Sciences de la Santé de Cotonou, Cotonou, Benin
| | | | - Patrick Makoutode
- Programme National de Lutte contre le paludisme Cotonou, Cotonou, Benin
| | - Alioun Adechoubou
- Programme National de Lutte contre le paludisme Cotonou, Cotonou, Benin
| | - Thibaut Legba
- Programme National de Lutte contre le paludisme Cotonou, Cotonou, Benin
| | | | - Dorothée Kinde-Gazard
- Unité d'Enseignement et de Recherche en Parasitologie-Mycologie de la Faculté des Sciences de la Santé de Cotonou, Cotonou, Benin
| | - Martin C Akogbeto
- Institut Régional de développement/Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Achille Massougbodji
- Unité d'Enseignement et de Recherche en Parasitologie-Mycologie de la Faculté des Sciences de la Santé de Cotonou, Cotonou, Benin
| | | | | | - Immo Kleinschmidt
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
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50
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Alout H, Labbé P, Chandre F, Cohuet A. Malaria Vector Control Still Matters despite Insecticide Resistance. Trends Parasitol 2017; 33:610-618. [PMID: 28499699 DOI: 10.1016/j.pt.2017.04.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/14/2017] [Accepted: 04/18/2017] [Indexed: 11/26/2022]
Abstract
Mosquito vectors' resistance to insecticides is usually considered a major threat to the recent progresses in malaria control. However, studies measuring the impact of interventions and insecticide resistance reveal inconsistencies when using entomological versus epidemiological indices. First, evaluation tests that do not reflect the susceptibility of mosquitoes when they are infectious may underestimate insecticide efficacy. Moreover, interactions between insecticide resistance and vectorial capacity reveal nonintuitive outcomes of interventions. Therefore, considering ecological interactions between vector, parasite, and environment highlights that the impact of insecticide resistance on the malaria burden is not straightforward and we suggest that vector control still matters despite insecticide resistance.
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Affiliation(s)
- Haoues Alout
- Institut des Sciences de l'Evolution de Montpellier, CNRS, IRD, University of Montpellier, ISEM - UMR 5554, Montpellier, France.
| | - Pierrick Labbé
- Institut des Sciences de l'Evolution de Montpellier, CNRS, IRD, University of Montpellier, ISEM - UMR 5554, Montpellier, France
| | - Fabrice Chandre
- Institut de recherche pour le développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UM-CNRS 5290 IRD 224, Montpellier, France
| | - Anna Cohuet
- Institut de recherche pour le développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UM-CNRS 5290 IRD 224, Montpellier, France.
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