Date Published: February 21, 2017
Publisher: Public Library of Science
Author(s): Lucy S. Tusting, Christian Bottomley, Harry Gibson, Immo Kleinschmidt, Andrew J. Tatem, Steve W. Lindsay, Peter W. Gething, Lorenz von Seidlein
Abstract: BackgroundImprovements to housing may contribute to malaria control and elimination by reducing house entry by malaria vectors and thus exposure to biting. We tested the hypothesis that the odds of malaria infection are lower in modern, improved housing compared to traditional housing in sub-Saharan Africa (SSA).Methods and FindingsWe analysed 15 Demographic and Health Surveys (DHS) and 14 Malaria Indicator Surveys (MIS) conducted in 21 countries in SSA between 2008 and 2015 that measured malaria infection by microscopy or rapid diagnostic test (RDT). DHS/MIS surveys record whether houses are built with finished materials (e.g., metal) or rudimentary materials (e.g., thatch). This information was used to develop a binary housing quality variable where houses built using finished wall, roof, and floor materials were classified as “modern”, and all other houses were classified as “traditional”. Conditional logistic regression was used to determine the association between housing quality and prevalence of malaria infection in children aged 0–5 y, adjusting for age, gender, insecticide-treated net (ITN) use, indoor residual spraying, household wealth, and geographic cluster. Individual survey odds ratios (ORs) were combined to determine a summary OR using a random effects meta-analysis.Of 284,532 total children surveyed, 139,318 were tested for malaria infection using microscopy (n = 131,652) or RDT (n = 138,540). Within individual surveys, malaria prevalence measured by microscopy ranged from 0.4% (Madagascar 2011) to 45.5% (Burkina Faso 2010) among children living in modern houses and from 0.4% (The Gambia 2013) to 70.6% (Burkina Faso 2010) in traditional houses, and malaria prevalence measured by RDT ranged from 0.3% (Senegal 2013–2014) to 61.2% (Burkina Faso 2010) in modern houses and from 1.5% (The Gambia 2013) to 79.8% (Burkina Faso 2010) in traditional houses. Across all surveys, modern housing was associated with a 9% to 14% reduction in the odds of malaria infection (microscopy: adjusted OR 0.91, 95% CI 0.85–0.97, p = 0.003; RDT: adjusted OR 0.86, 95% CI 0.80–0.92, p < 0.001). This association was consistent regardless of ITN usage. As a comparison, the odds of malaria infection were 15% to 16% lower among ITN users versus non-users (microscopy: adjusted OR 0.84, 95% CI 0.79–0.90, p < 0.001; RDT: adjusted OR 0.85, 95% CI 0.80–0.90, p < 0.001).The main limitation of this study is that residual confounding by household wealth of the observed association between housing quality and malaria prevalence is possible, since the wealth index may not have fully captured differences in socioeconomic position; however, the use of multiple national surveys offers the advantage of a large sample size and the elimination of many biases typically associated with pooling observational data.ConclusionsHousing quality is an important risk factor for malaria infection across the spectrum of malaria endemicity in SSA, with a strength of association between housing quality and malaria similar to that observed between ITN use and malaria. Improved housing should be considered a promising intervention for malaria control and elimination and long-term prevention of reintroduction.
Partial Text: Insecticide-treated nets (ITNs) and indoor residual spraying (IRS) have contributed to a 40% reduction in malaria incidence in endemic Africa since 2000 . These are highly effective methods of vector control, but additional interventions are needed for long-term, sustainable malaria control and elimination. Evidence from some tropical settings indicates that modern, well-built housing protects against malaria , with two postulated mechanisms. First, house entry by mosquito vectors is reduced by physical barriers such as closed eaves (the gap between the roof and top of the wall), tiled or metal roofs instead of thatch, and door and window screening [2,3]. Second, daytime indoor temperature is higher in metal-roofed than thatch-roofed houses , which may impair parasite development if it exceeds an optimal temperature range . House improvements could be an important pillar of malaria intervention as intersectoral approaches to malaria control and elimination are increasingly encouraged [6,7], especially given the new global target to ensure universal access to adequate, safe, and affordable housing by 2030 . Africa’s rapid economic and population growth—its population is projected to increase from 1.2 billion in 2015 to 2.1 billion in 2050 , and it has the world’s fastest rate of urbanisation —presents an unrivalled opportunity to build healthier homes.
We have conducted a comprehensive analysis of the relationship between housing quality and malaria across SSA and, to our knowledge, provided the first direct comparison with ITNs. Our analysis of 29 DHS and MIS surveys found living in a modern house to be associated with 9% to 14% lower odds of malaria infection in children aged 0–5 y, compared to living in a traditional house. As a comparison, ITN use was associated with a 15% to 16% reduction in the odds of malaria infection. Our study indicates that poor housing quality is an important risk factor for malaria in SSA and that improved housing is a promising intervention for malaria control and elimination and prevention of reintroduction.