The evidence for improving housing to reduce malaria: a systematic review and meta-analysis

Abstract

Background: The global malaria burden has fallen since 2000, sometimes before large-scale vector control programmes were initiated. While long-lasting insecticide-treated nets and indoor residual spraying are highly effective interventions, this study tests the hypothesis that improved housing can reduce malaria by decreasing house entry by malaria mosquitoes.

Methods: A systematic review and meta-analysis was conducted to assess whether modern housing is associated with a lower risk of malaria than traditional housing, across all age groups and malaria-endemic settings. Six electronic databases were searched to identify intervention and observational studies published from 1 January, 1900 to 13 December, 2013, measuring the association between house design and malaria. The primary outcome measures were parasite prevalence and incidence of clinical malaria. Crude and adjusted effects were combined in fixed- and random-effects meta-analyses, with sub-group analyses for: overall house type (traditional versus modern housing); screening; main wall, roof and floor materials; eave type; ceilings and elevation.

Results: Of 15,526 studies screened, 90 were included in a qualitative synthesis and 53 reported epidemiological outcomes, included in a meta-analysis. Of these, 39 (74%) showed trends towards a lower risk of epidemiological outcomes associated with improved house features. Of studies assessing the relationship between modern housing and malaria infection (n=11) and clinical malaria (n=5), all were observational, with very low to low quality evidence. Residents of modern houses had 47% lower odds of malaria infection compared to traditional houses (adjusted odds ratio (OR) 0°53, 95% confidence intervals (CI) 0°42-0°67, p< 0°001, five studies) and a 45-65% lower odds of clinical malaria (case-control studies: adjusted OR 0°35, 95 % CI 0°20-0°62, p<0°001, one study; cohort studies: adjusted rate ratio 0°55, 95% CI 0°36-0°84, p=0°005, three studies). Evidence of a high risk of bias was found within studies.

Conclusions: Despite low quality evidence, the direction and consistency of effects indicate that housing is an important risk factor for malaria. Future research should evaluate the protective effect of specific house features and incremental housing improvements associated with socio-economic development.

Figures

Fig. 1

Changes in housing in sub-Saharan Africa, 1975–2012. Despite limited data, there is evidence that the quality of both urban and rural housing is improving in parts of SSA, including Bioko, Kenya, Ethiopia and Tanzania. a. Trends in housing in Bioko, Equatorial Guinea, 2009–2012 [18]. b. Proportion of homes with thatch and iron roofs in Kenya, 1993–2009 [33]. c. Proportion of homes with thatch and iron roofs in Ethiopia, 2000–2011 [33]. d. Estimated proportion of homes with concrete walls and iron roofs in Korogwe, Tanzania, 1975–2008 [34]. e. Percent reduction in the proportion of households with natural or rudimentary flooring in SSA (comparing earliest and latest available Demographic and Health Surveys (DHS); dates are shown for each country) [35]

Fig. 2

Study selection

Fig. 3

Meta-analysis of the association between modern housing and malaria infection. Pooled effects from random-effects meta-analyses for crude (1°1°1) and adjusted (1°1°2) results are shown. Studies are divided into sub-groups by study design. Error bars show 95 % CIs; df = degrees of freedom. 1. Al-Makhlafi 2011 YEM: Good vs poor house quality; 2. Barber 1935 GRC: Modern (tiled roof, ceiling) vs traditional (thatched roof, reed or no ceiling); 3. Butraporn 1935 THA: Permanent vs semi-permanent or temporary; 4. Dahesh 2009 EGY: Painted brick walls and cement ceilings vs mud walls and wood or mud ceilings; 5. de Alemida 2010 TLS: Complete vs incomplete house; 6. Osterbauer 2012 UGA: Modern (iron roof, burnt brick or cement walls and cement floor) vs traditional; 7. van der Hoek 2003 LKA: Modern (brick walls and permanent roof material) vs traditional (mud walls or thatched roof); 8. Wolff 2001 MWI: Modern vs traditional; 9. Woyessa 2013 ETH: Good vs dilapidated house, 10. de Beaudrap 2001 UGA: Brick walls and iron roof vs mud walls and thatched roof (OR adjusted for age, weight, socio-economic status, education, altitude, ITNs), 11. Osterbauer 2012 UGA: Modern (iron roof, burnt brick or cement walls and cement floor) vs traditional (OR adjusted for age, HIV-exposure, enrolment period, gender, mother's age, prophylaxis); 12. van der Hoek 2003 LKA: Modern (brick walls and permanent roof material) vs traditional (mud walls or thatched roof) (OR adjusted for age, gender, distance to stream, distance to cattle shed, coil use, ITNs, IRS); 13. Wanzirah 2015 UGA: Modern (cement, wood or metal wall; tiled or metal roof and closed eaves) vs traditional (OR adjusted for age, gender, study site, household wealth); 14. Wolff 2001 MWI: Modern vs traditional (OR adjusted for water source, occupation, education, malaria knowledge, waste disposal method)

Fig. 4

Meta-analysis of the association between modern housing and clinical malaria. Pooled effects from random-effects meta-analyses for crude (1°2°1; 1°2°3) and adjusted (1°2°2; 1°2°4) results are shown. Studies are divided into sub-groups by study design. Error bars show 95 % CIs; df = degrees of freedom. 1. Danis-Lozano 2007 MEX: House constructed with non-perishable vs perishable materials; 2. Danis-Lozano 2007 MEX: House constructed with non-perishable vs perishable materials (OR adjusted for occupation, village); 3. Liu 2014 TZA: Highest quintile of housing index compared to lowest quintile (based on roof, wall and floor material and presence of ceiling, eaves, screening); 4. Peterson 2009a ETH: Medium or good vs poor house construction; 5. Peterson 2009b ETH: Good vs poor house construction; 6. Liu 2014 TZA: Highest quintile of housing index compared to lowest quintile (based on roof, wall and floor material and presence of ceiling, eaves, screening) (RR adjusted for age, mother's education, wealth index, prophylaxis, socio-economic status, urban site, intermittent preventive treatment in infants (IPTi) trial arm); 7. Peterson 2009b ETH: Good vs poor house construction (RR adjusted for ITNs, vegetation, temperature, rainfall, larval densities); 8. Wanzirah 2015 UGA: Modern (cement, wood or metal wall; tiled or metal roof and closed eaves) vs traditional (RR adjusted for age, gender, study site, household wealth)