Epidemiology of Urban Malaria in the Greater Accra Region of Ghana: Predictors and Effect Modification across a Transmission Season.

Abstract

Urban malaria transmission in sub-Saharan Africa remains heterogeneous and incompletely characterized, particularly in rapidly expanding metropolitan areas. We investigated predictors of Plasmodium falciparum infection and effect modification of key interventions across the Greater Accra Region of Ghana. Three cross-sectional household cluster visits were conducted during pre-rains, rains, and post-rains periods of the 2024 transmission season. Participants age ≥6 months were tested using multispecies rapid diagnostic tests, microscopy, and loop-mediated isothermal amplification confirmations. Structured administered questionnaires captured sociodemographic, travel, and vector-control information. Multilevel logistic regression models estimated adjusted odds ratios (aORs) with 95% CIs. Among 10,716 sampled participants from 3,904 households, P. falciparum prevalence ranged from 6.5% to 12% across visit rounds. Although older groups and males had higher odds of infection, participants in the highest socioeconomic status demographic had lower odds. Coverage of indoor residual spraying (IRS) and use of other vector-control methods, including bed nets, mosquito coils, mosquito spray, mosquito repellent, and burning leaves, was low, with no protective association observed for any method. However, interaction associations of bed net use and IRS coverage with malaria infection differed by residency (bed net aOR: 0.49, 95% CI: 0.29-0.86; IRS aORs: 0.59, 95% CI: 0.36-0.97), though stratified models demonstrated mixed findings, with no protective association for either method in either residency. Travel history was not associated with infection. Urban malaria risk in Greater Accra appears to be driven primarily by localized transmission dynamics with spatial heterogeneity in intervention effectiveness, underscoring the need for geographically targeted control strategies.