Is there preferential coverage for the most at risk? A survey-based analysis of malaria vector control by endemicity level

Abstract

BackgroundAlthough US$2·3 billion in 2011 was spent on malaria control globally, a financing gap of $2·8 billion remains. While equity in intervention coverage is the ultimate goal, with limited resources, it is crucial to target interventions strategically. Developments in cartographic methods for estimating Plasmodium falciparum parasite rate (PfPR) at low geospatial levels and availability of household surveys with global positioning system (GPS) coordinates now allow for estimation of malaria intervention coverage stratified by level of infection risk. Taking advantage of this information, we aim to identify whether malaria interventions are targeted to those populations most at risk of malaria infection. MethodsOur study spanned 24 countries and used all 38 Malaria Indicator Surveys and Demographic and Health Surveys with GPS coordinates and survey questions on use of insecticide-treated mosquito nets (ITNs). For these surveys, conducted between 2003 and 2011, we obtained cluster-level PfPR by matching coordinates of surveyed clusters to coordinates from Malaria Atlas Project PfPR maps. For each survey, we calculated the proportion of household availability of ITNs and prevalence of indoor residual spraying (IRS) by level of malaria endemicity (low, intermediate, high). We sought to further explain variation in coverage of vector control interventions by examining PfPR by wealth quintile and urban or rural residence. FindingsCoverage of ITNs or IRS by endemicity level varies greatly by country and year. In only four (Burundi, Ethiopia, Senegal, Zimbabwe) of the 24 surveyed countries did the coverage of IRS or availability of ITNs increase monotonically with increasing endemicity level. While coverage of ITNs or IRS in Senegal in 2010 among populations at low risk was 16·4% (95% CI 13·2–19·6), coverage among those at intermediate and high risk was 31·7% (27·8–35·5) and 64·6% (30·0–99·0), respectively. By contrast, coverage in Tanzania in the same year was 73·5% (95% CI 69·3–77·6) among those at lowest risk, and 67·5% (64·4–70·7) and 53·0 (48·2–57·8) among those at medium and high risk, respectively. Nearly all surveys indicate lower coverage of vector control interventions and higher PfPR in poorer, more rural areas. InterpretationIn the countries examined in this study, coverage of vector control interventions did not necessarily increase with increasing malaria risk. If limited resources preclude protecting all persons at risk of malaria with vector control interventions, strategies for targeting interventions (such as on the basis of malaria risk) should be devised to achieve their greatest lifesaving potential. FundingNone.