BACKGROUND: In western Kenya, a cluster-randomized trial is assessing the impact of attractive targeted sugar baits (ATSBs) on malaria in children enrolled in three consecutive cohorts. Here, characteristics of children and households at enrolment, and factors associated with baseline malaria prevalence are described. METHODS: Children aged 1 to < 15 years were randomly selected by cluster (n = 70) from a census database. Cohorts were enrolled in March-April 2022, September-October 2022, and March-April 2023. ATSBs were deployed in March 2022. At enrolment, all participants were tested for malaria by rapid diagnostic test (RDT). After enrolment a household survey was conducted. Household structures were classified as 'improved' (finished walls and roofs, and closed eaves) or 'traditional' (all other construction). A generalized linear mixed model was used to assess factors associated with malaria prevalence. RESULTS: Of 3705 children screened, 220 declined and 523 were excluded, due to plans to leave the study area (n = 392), ineligible age (n = 64) or other reason (n = 67). Overall, 2962 children were enrolled. Bed net use the previous night was more common in children aged 1-4 years (746/777 [96%]) than those aged 5-<15 years (1806/2157 [84%], p < 0.001). Of the 2644 households surveyed (for 2,886 participants), information on house construction was available for 2595. Of these, only 199 (8%) were categorized as 'improved', as most houses had open eaves. While 99% of households owned at least one bed net, only 51% were adequately covered (one net per two household residents). Among 999 children enrolled in the first cohort (baseline), 498 (50%) tested positive by RDT. In an adjusted multivariable analysis, factors associated with RDT positivity included sub-county (Alego-Usonga vs Rarieda, adjusted odds ratio [aOR] 4.81; 95% CI: 2.74-8.45; p < 0.001), house construction (traditional vs improved, aOR 2.80; 95% CI: 1.59-4.95; p < 0.001), and age (5-< 15 vs 1-4 years, aOR 1.64; 95% CI: 1.13-2.37; p = 0.009). CONCLUSIONS: In western Kenya, the burden of malaria in children remains high. Most households owned a bed net, but coverage was inadequate. Residents of Alego-Usonga sub-county, those living in traditionally constructed households, and older children were more likely to test positive by RDT. Additional tools are needed to effectively control malaria in this area. Trial registration The ATSB trial is registered under Clinicaltrials.gov NCT05219565.

Characterization of serological responses to Plasmodium falciparum (Pf) is of interest to understand disease burden and transmission dynamics; however, their interpretation is challenging. Dried blood spots from 30,815 participants aged 6 months to 15 years from the 2018 Nigeria HIV/AIDS Indicator and Impact Survey were analyzed by multiplex bead-based assay to measure immunoglobulin G (IgG) to Pf-stage-specific MSP-1, AMA-1, GLURPR0, LSA-1, and CSP. These IgG levels were analyzed by principal component analysis (PCA). PC1 and PC2 scores explained 41% and 17% of the total variance, respectively. PC1 unit vectors represented seropositivity. PC2 unit vectors for blood-stage antigens were in opposite directions to liver-stage and sporozoite antigens. PC2 scores were correlated with MSP-1 positively (R = 0.52, P < 0.001) and CSP negatively (R=-0.65, P < 0.001) and may help identify areas with prior exposure but higher risk for increased infections or epidemics. PCA of Pf serology can provide summary scores to possibly inform future programmatic interventions.

Return to international travel in the COVID-19 pandemic recovery period is expected to increase the number of patients with imported malaria in the United States (US). Malaria prevention in travelers and preparedness for timely diagnosis and appropriate treatment are key to minimize imported malaria morbidity and mortality. Intravenous artesunate (IVAS) is now available from commercial distributors in the US for the treatment of severe malaria. Hospitals and pharmacists should have a plan for malaria treatment, including stocking artemether-lumefantrine for uncomplicated malaria, and stocking or planning for rapid procurement of IVAS for the treatment of severe malaria.