Spatial and epidemiological drivers of P. falciparum malaria among adults in the Democratic Republic of the Congo

Background: Malaria remains a significant public health problem in sub-Saharan Africa. Adults are frequently infected and may serve as a reservoir for further transmission, yet we know relatively little about risk factors for adult infections. In this study, we assessed malaria risk factors amongst adults using samples from the nationally representative, cross-sectional 2013-2014 Demographic and Health Survey (DHS) conducted in the Democratic Republic of Congo (DRC). We further explored differences in risk factors by urbanicity. Methods: Plasmodium falciparum infection was determined by polymerase chain reaction (PCR). Covariates were drawn from the DHS to model individual, community, and environmental level risk factors for infection. Additionally, we used deep sequencing data to estimate the community-level proportions of drug resistant infections and included these estimates as potential risk factors. All identified factors were assessed for differences in associations by urbanicity. Results: A total of 16,126 adults were included. Overall prevalence of malaria was 30.3% (SE = 1.1) by PCR; province-level prevalence ranged from 6.7-58.3%. Only 17% of individuals lived in households with at least one bednet for every two people, as recommended by the World Health Organization. Protective factors included increasing within-household bednet coverage (PR = 0.85, 95% CI = 0.76 - 0.95) and modern housing (PR = 0.58, 95% CI = 0.49 - 0.69). Community level protective factors included: increased average education and wealth (PR = 0.77, 95% CI = 0.65-0.91; PR - 0.84, 95% CI = 0.80 - 0.89). Education, wealth, and modern housing showed protective associations in cities but not in rural areas. Conclusions: The DRC continues to suffer from a high burden of malaria; interventions that target high-risk groups and sustained investment in malaria control are sorely needed. Differences in risk factors by urbanicity may be due to differences in transmission intensity or access to resources.