Malaria treatment for prevention: a modelling study of the impact of routine case management on malaria prevalence and burden

Abstract Background Testing and treating symptomatic malaria cases is crucial for case management, but it may also prevent future illness by reducing mean infection duration. Measuring the impact of effective treatment on burden and transmission via field studies or routine surveillance systems is difficult and potentially unethical. This project uses mathematical modeling to explore how increasing treatment of symptomatic cases impacts malaria prevalence and incidence.Methods Leveraging the OpenMalaria stochastic agent-based transmission model, we first simulated an array of transmission intensities with baseline effective treatment coverages of 28%, 44%, and 54% incorporated to reflect the 2023 coverage distribution across Africa, as estimated by the Malaria Atlas Project. We assessed the impact of increasing coverage as high as 60%, the highest 2023 estimate on the continent. Subsequently, we performed simulations resembling the specific subnational endemicities of Kenya, Mozambique, and Benin, using publicly available estimates of intervention coverages to reproduce historical subnational prevalence. We estimated the impact of increasing effective treatment coverage in these example settings in terms of prevalence reduction and clinical cases averted in children under 5 and the total population.Results The most significant prevalence reduction – up to 50% – was observed in young children from lower transmission settings (prevalence below 0.2), alongside a 35% reduction in incidence, when increasing effective treatment from 28–60%. A nonlinear relationship between baseline transmission intensity and the impact of treatment was observed. Increasing effective treatment coverage to 60% led to an estimated 39% of young children in Benin and 20% in Mozambique that would no longer live in high-risk areas (prevalence in children under 5 years old > 0.3). In Kenya where most of the population lives in areas with prevalence below 0.15, and case management is high (53.9%), 0.39% of children were estimated to transition to lower-risk areas.Conclusion Improving case management directly reduces the burden of illness, but these results suggest it also reduces transmission, especially for young children. In synergy with vector control interventions, enhancing case management can be an important tool for reducing transmission intensity over time.