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. ### Competing Interest Statement JBP reports support from the World Health Organization; JPB and SRM report non-financial support from Abbott Laboratories, which has performed laboratory testing in-kind as part of their hepatitis research, outside the submitted work. ### Funding Statement This study was supported by R01AI107949 to SRM and T32AI070114 to MDF from the National Institutes of Health National Institute for Allergy and Infectious Disease. This study was also supported by a Burroughs Wellcome Fund-American Society for Tropical Medicine and Hygiene fellowship to JBP and R01AI139520 to JAB. RV is jointly funded by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement and is also part of the EDCTP2 programme supported by the European Union. ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data used in this study from the Demographic Health Surveys Program are available upon request at (https://dhsprogram.com/what-we-do/survey/survey-display-421.cfm)59. Raw sequencing data is publicly available through the NCBI SRA (Ascension number: PRJNA545347). Molecular data included in this study are available from the corresponding author upon reasonable request. * DRC : Democratic Republic of the Congo DHS : Demographic and Health Survey PCR : polymerase chain reaction LLIN : long-lasting insecticide treated net SNP : single nucleotide polymorphism MIP : molecular inversion probe PCA : principal components analysis SP : Sulfadoxine/pyrimethamine