Housing Quality as a Potential Risk Factor for Locally Acquired Malaria Infection in Swaziland
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Poor housing quality may confer greater risk of malaria infection by means of increased mosquito exposure; however, evidence in low transmission settings is lacking. In this study, surveillance data was used to examine the relationship between housing quality and locally-acquired infection in the low transmission setting of Swaziland. A retrospective analysis was conducted utilizing data collected from passive and active surveillance. Subjects included malaria index cases diagnosed at health facilities as well as their household and community members screened in reactive case detection from August 2012 to March 2015. Subjects reporting travel in the past 8 weeks and/or residing beyond 500m from the index case were excluded. Using bivariate and multivariable logistic regression, adjusted for household-level clustering, the relationships between infection (testing positive by Rapid Diagnostic Test (RDT), microscopy, or loop-mediated isothermal amplification (LAMP)) and housing quality, as well as other epidemiological factors were analyzed. Housing quality was assessed by individual components (wall, roof and window type) as well as a composite housing quality index. Cases included 280 index cases and 131 RDT or LAMP positive individuals identified in active surveillance. These cases were compared to 8668 non-infected household members and neighbors of index cases. In the multivariable model, poor quality external wall was associated with higher infection odds (OR 4.59 95%CI 1.93-10.95). There was a trend in the association with both poor quality roof and windows. Using the composite housing index, compared to good quality housing, moderate quality housing was significantly associated with higher infection odds (OR 1.67 95%CI 1.09-2.57). There was a notable, yet non-significant trend in the association with poor quality housing (OR 2.05 95%CI 0.99-4.26). In the composite housing model, coverage of vector control interventions was independently associated with protection. Compared to no vector control (neither sleeping under an insecticide treated bed net (ITN) nor a sprayed structure), coverage with either an ITN or spraying conferred protection (OR 0.61 95%CI 0.40-0.94), as did coverage with both interventions (OR 0.10 95%CI 0.01-0.73). The findings of this study suggest that housing quality, especially wall material, is an important determinant of locally-acquired infection in Swaziland, suggesting improved housing as a potential control and elimination strategy in low transmission settings.