House Structure Is Associated with Malaria among Febrile Patients in a High-Transmission Region of Zambia

Abstract

Since the late nineteenth century, the importance of house structure as a determinant of malaria risk has been recognized. Few studies to date have examined the association of housing and malaria in clinical populations. We conducted a cross-sectional study of febrile patients (n = 282) at two rural health clinics in a high malaria-transmission area of northern Zambia. Participants underwent testing for Plasmodium falciparum infection by PCR. Demographic and other risk factors including house structure, indoor residual spraying (IRS), bed net use, education level, and household income were collected. Data were fitted to logistic regression models for relational and mediation analyses. Residing in a house with a thatch roof was associated with higher odds of malaria than residing in a house with corrugated metal (odds ratio: 2.6; 95% CI: 1.0-6.3, P = 0.04). Lower income and educational attainment were also associated with greater odds of malaria. Living under a thatch roof accounted for 24% (95% CI: 14-82) of the effect of household income on malaria risk, and income accounted for 11% (95% CI: 8-19) of the effect of education. Neither IRS nor bed net use was associated with malaria risk despite large, local investments in these vector control interventions. The findings testify to malaria as a disease of rural poverty and contribute further evidence to the utility of housing improvements in vector control programs.

Figure 1.

Photographs of representative house types showing (A) fired-brick walls and metal roof and (B) sunbaked mud brick walls and thatch roof. This figure appears in color at www.ajtmh.org.

Figure 2.

Directed acyclic graph of the hypothesized relationships among education, income, housing, and malaria in febrile patients within a highly malarious area of Zambia. Graph A depicts the partial mediation of the association of income with malaria by housing, and graph B shows the partial mediation of the association of education with malaria by income. Odds ratios (ORs) were computed from logistic regression of malaria PCR test positivity on education (primary vs. secondary or higher), daily income (< 2 USD vs. ≥ 2 USD), and housing (thatch vs. metal roof). Percent contributions were calculated from mediation analyses conducted according to Imai et al.

Figure 3.

Malaria prevalence by house construction type. (A) shows comparison by roof construction (T = thatch and M = metal), (B) shows comparison by wall material (S = straw-and-pole and B = brick or cement block), and (C) shows results stratified by combinations of roof and wall types. Among patients presenting to rural health clinics with fever, living in a house with a thatch roof was associated with increased odds of malaria (adjusted OR: 2.6; 95% CI: 1.0–6.3, P = 0.04 denoted by asterisk). Error bars represent 95% CIs.