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Impact of increased district-level insecticide-treated net (ITN) distribution on all-cause under-five mortality in Malawi, 2004-2010


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Presented at the November 2013 ASTHM Conference.

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Impact of increased district-level insecticide-treated net (ITN) distribution on all-cause under-five mortality in Malawi, 2004-2010

  1. 1. Impact of increased district-level insecticide-treated net (ITN) distribution on all-cause under-five mortality in Malawi, 2004-2010 Lia S. Florey¹; Adam Bennett²; Cameron Taylor¹; Christine Hershey³; Achuyt Bhattarai4; Carrie Nielsen4; S. Rene Salgado³; Doreen Ali5; Misheck Luhanga5; Thomas Eisele²; Yazoume Ye6 ¹ICF International, MEASURE DHS; ²Tulane University School of Public Health, Department of Global Health Systems and Development; ³United States Agency for International Development – President’s Malaria Initiative; 4Centers for Disease Control and Prevention – President’s Malaria Initiative; 5National Malaria Control Programme, Malawi; 6ICF International, MEASURE Evaluation Background Methods Interpretation Acknowledgments The increase in funding for malaria control efforts in the last decade resulted in the scale-up of key interventions. Partners are eager to know if this scale-up resulted in a reduction of malaria burden. Insecticide treated mosquito nets (ITN) have been shown to be highly effective at reducing malaria morbidity and mortality in children. However, there are limited studies that assess the association between increasing ITN distribution and child mortality over time at the district level and under programmatic conditions. We used a negative binomial regression model to assess the impact of scale-up of ITNs on all-cause mortality in children less than five years of age (ACCM) in Malawi from 2004 to 2010 using a district platform analysis. Other predictors of child survival were also examined including measures of socio-economic status, child and maternal health. • 2010 Demographic and Health Survey (DHS) birth history data • 2006 Multiple Indicator Cluster Survey (MICS) and 2010 DHS contextual factors • District-level ITN distribution data from the Malawi National Malaria Control Program • Mid-year district-level population estimates from 1998 and 2008 census data • District-level mean Plasmodium falciparum prevalence rate in children 2–10 years of age (PfPR2-10) from MAP • Mean annual district-level rainfall and anomaly from five- year average from USGS FEWS NET data portal Data sources • Data from women’s birth histories from the 2010 DHS were used to generate longitudinal records of child deaths • In order to construct annual estimates covariates that were collected cross-sectionally only during survey years, data from both the 2006 MICS and the 2010 DHS were used • Weighted averages of district-level means for these variables were constructed for interim years between surveys • District-level negative binomial regression models were employed using aggregated estimates of ITN ownership and other covariates including PfPR2-10 and rainfall anomaly data at the district-year-level looking for associations with counts of child deaths per district per year • ITN coverage was as population-adjusted numbers of ITNs distributed per district per year using census and program data. In Malawi, between 2004 and 2010, ITN distribution was significantly scaled-up and all-cause child mortality declined significantly. In a negative binomial regression model controlling for year, percent of households with protected sources of drinking water, percent of children whose mother’s have at least a primary school education, percent of children who are stunted, and percent of women who were immunized for tetanus during her most recent pregnancy, higher district ITN program intensity was significantly associated with lower all-cause under-five mortality (IRR = 0.89; 95% CI = 0.81–0.99). These findings represent a novel use of district-level data from nationally-representative surveys and suggest that increasing ITN coverage may have significantly contributed to the decline in all-cause under-five mortality during 2004-2010 in Malawi. Analysis The team would like to acknowledge the support of the Ministry of Health and Social Welfare, the National Malaria Control Programme and the Malawi National Bureau of Statistics. Funding for this research was provided by the United States Agency for International Development (USAID) through the MEASURE DHS project, implemented by ICF International in Calverton, Maryland, USA, and MEASURE Evaluation Project supported from the U.S. Agency for USAID)under the terms of Cooperative Agreement GPO-A-00-03-00003-00. Views expressed are those of the authors and do not necessarily reflect the views of USAID or the United States Government. Results 859 Figure 1: Ratio of ITNs to population, by district, 2004-2010 Table 1: Multivariable model of under-five mortality, 2004-2010Figure 2: Annual ACCM using DHS and IGME estimates, 1990-2010 This ecological analysis examines the effect of increasing ITN distribution over time on numbers of child deaths by district, controlling for other variables that affect child survival. This approach was possible in Malawi as the national household surveys used were sampled to be representative at the district-level. IRR LCI UCI p-value Year 2004 ref 2005 0.77 0.67 0.89 <0.001 2006 0.84 0.69 1.03 0.087 2007 0.68 0.57 0.80 <0.001 2008 0.65 0.57 0.74 <0.001 2009 0.80 0.68 0.94 0.006 2010 0.54 0.45 0.65 <0.001 ITN ratio ≤0.25 ITN/person ref >0.25 ITN/person 0.89 0.81 0.99 0.033 Proportion with improved water Low ref High 3.03 1.42 6.47 0.004 Mother’s education greater than primary Low ref High 0.56 0.34 0.90 0.017 Proportion with stunting Low ref High 2.61 1.04 6.54 0.04 Proportion with tetanus immunization Low ref High 2.27 1.27 4.08 0.006 © Diana Mrazikova, courtesy of Photoshare IRR = Incidence rate ratio; LCI = Lower confidence interval; UCI = Upper confidence interval