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Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar

INTRODUCTION: Indoor residual spraying (IRS) and insecticide-treated bed nets (ITNs) are cornerstone malaria prevention methods in Madagascar. This retrospective observational study uses routine data to evaluate the impacts of IRS overall, sustained IRS exposure over multiple years and level of spra...

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Autores principales: Hilton, Emily R, Rabeherisoa, Saraha, Ramandimbiarijaona, Herizo, Rajaratnam, Julie, Belemvire, Allison, Kapesa, Laurent, Zohdy, Sarah, Dentinger, Catherine, Gandaho, Timothee, Jacob, Djenam, Burnett, Sarah, Razafinjato, Celestin
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BMJ Publishing Group 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10357738/
https://www.ncbi.nlm.nih.gov/pubmed/37463785
http://dx.doi.org/10.1136/bmjgh-2022-010818
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author Hilton, Emily R
Rabeherisoa, Saraha
Ramandimbiarijaona, Herizo
Rajaratnam, Julie
Belemvire, Allison
Kapesa, Laurent
Zohdy, Sarah
Dentinger, Catherine
Gandaho, Timothee
Jacob, Djenam
Burnett, Sarah
Razafinjato, Celestin
author_facet Hilton, Emily R
Rabeherisoa, Saraha
Ramandimbiarijaona, Herizo
Rajaratnam, Julie
Belemvire, Allison
Kapesa, Laurent
Zohdy, Sarah
Dentinger, Catherine
Gandaho, Timothee
Jacob, Djenam
Burnett, Sarah
Razafinjato, Celestin
author_sort Hilton, Emily R
collection PubMed
description INTRODUCTION: Indoor residual spraying (IRS) and insecticide-treated bed nets (ITNs) are cornerstone malaria prevention methods in Madagascar. This retrospective observational study uses routine data to evaluate the impacts of IRS overall, sustained IRS exposure over multiple years and level of spray coverage (structures sprayed/found) in nine districts where non-pyrethroid IRS was deployed to complement standard pyrethroid ITNs from 2017 to 2020. METHODS: Multilevel negative-binomial generalised linear models were fit to estimate the effects of IRS exposure overall, consecutive years of IRS exposure and spray coverage level on monthly all-ages population-adjusted malaria cases confirmed by rapid diagnostic test at the health facility level. The study period extended from July 2016 to June 2021. Facilities with missing data and non-geolocated communes were excluded. Facilities in IRS districts were matched with control facilities by propensity score analysis. Models were controlled for ITN survivorship, mass drug administration coverage, precipitation, enhanced vegetation index, seasonal effects and district. Predicted cases under a counterfactual no IRS scenario and number of cases averted by IRS were estimated using the fitted models. RESULTS: Exposure to IRS overall reduced case incidence by an estimated 30.3% from 165.8 cases per 1000 population (95% CI=139.7 to 196.7) under a counterfactual no IRS scenario, to 114.3 (95% CI=96.5 to 135.3) over 12 months post-IRS campaign in nine districts. A third year of IRS reduced malaria cases 30.9% more than a first year (incidence rate ratio (IRR)=0.578, 95% CI=0.578 to 0.825, p<0.001) and 26.7% more than a second year (IRR=0.733, 95% CI=0.611 to 0.878, p=0.001). There was no significant difference between the first and second year (p>0.05). Coverage of 86%–90% was associated with a 19.7% reduction in incidence (IRR=0.803, 95% CI=0.690 to 0.934, p=0.005) compared with coverage ≤85%, although these results were not robust to sensitivity analysis. CONCLUSION: This study demonstrates that non-pyrethroid IRS appears to substantially reduce malaria incidence in Madagascar and that sustained implementation of IRS over three years confers additional benefits.
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spelling pubmed-103577382023-07-21 Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar Hilton, Emily R Rabeherisoa, Saraha Ramandimbiarijaona, Herizo Rajaratnam, Julie Belemvire, Allison Kapesa, Laurent Zohdy, Sarah Dentinger, Catherine Gandaho, Timothee Jacob, Djenam Burnett, Sarah Razafinjato, Celestin BMJ Glob Health Original Research INTRODUCTION: Indoor residual spraying (IRS) and insecticide-treated bed nets (ITNs) are cornerstone malaria prevention methods in Madagascar. This retrospective observational study uses routine data to evaluate the impacts of IRS overall, sustained IRS exposure over multiple years and level of spray coverage (structures sprayed/found) in nine districts where non-pyrethroid IRS was deployed to complement standard pyrethroid ITNs from 2017 to 2020. METHODS: Multilevel negative-binomial generalised linear models were fit to estimate the effects of IRS exposure overall, consecutive years of IRS exposure and spray coverage level on monthly all-ages population-adjusted malaria cases confirmed by rapid diagnostic test at the health facility level. The study period extended from July 2016 to June 2021. Facilities with missing data and non-geolocated communes were excluded. Facilities in IRS districts were matched with control facilities by propensity score analysis. Models were controlled for ITN survivorship, mass drug administration coverage, precipitation, enhanced vegetation index, seasonal effects and district. Predicted cases under a counterfactual no IRS scenario and number of cases averted by IRS were estimated using the fitted models. RESULTS: Exposure to IRS overall reduced case incidence by an estimated 30.3% from 165.8 cases per 1000 population (95% CI=139.7 to 196.7) under a counterfactual no IRS scenario, to 114.3 (95% CI=96.5 to 135.3) over 12 months post-IRS campaign in nine districts. A third year of IRS reduced malaria cases 30.9% more than a first year (incidence rate ratio (IRR)=0.578, 95% CI=0.578 to 0.825, p<0.001) and 26.7% more than a second year (IRR=0.733, 95% CI=0.611 to 0.878, p=0.001). There was no significant difference between the first and second year (p>0.05). Coverage of 86%–90% was associated with a 19.7% reduction in incidence (IRR=0.803, 95% CI=0.690 to 0.934, p=0.005) compared with coverage ≤85%, although these results were not robust to sensitivity analysis. CONCLUSION: This study demonstrates that non-pyrethroid IRS appears to substantially reduce malaria incidence in Madagascar and that sustained implementation of IRS over three years confers additional benefits. BMJ Publishing Group 2023-07-14 /pmc/articles/PMC10357738/ /pubmed/37463785 http://dx.doi.org/10.1136/bmjgh-2022-010818 Text en © Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. https://creativecommons.org/licenses/by-nc/4.0/This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/ (https://creativecommons.org/licenses/by-nc/4.0/) .
spellingShingle Original Research
Hilton, Emily R
Rabeherisoa, Saraha
Ramandimbiarijaona, Herizo
Rajaratnam, Julie
Belemvire, Allison
Kapesa, Laurent
Zohdy, Sarah
Dentinger, Catherine
Gandaho, Timothee
Jacob, Djenam
Burnett, Sarah
Razafinjato, Celestin
Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar
title Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar
title_full Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar
title_fullStr Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar
title_full_unstemmed Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar
title_short Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar
title_sort using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in madagascar
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10357738/
https://www.ncbi.nlm.nih.gov/pubmed/37463785
http://dx.doi.org/10.1136/bmjgh-2022-010818
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