Exploring measures to increase detection of malaria cases through reactive case detection in a Southern Province of Zambia-like Setup: A modelling study

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Abstract
Introduction In Zambia, malaria prevalence varies spatially, posing challenges for intervention strategies. Asymptomatic and clinical carriers not accessing healthcare further complicate efforts, necessitating reactive case detection (RCD) to target undetected infections. However, operational hurdles, such as resource shortages and logistical complexities—including shortages of community health workers (CHWs), difficulties reaching residents, and limitations in malaria rapid diagnostic tests (RDTs)—hinder RCD’s effectiveness. Identifying effective improvement measures given circumstances that may lead to deficient intervention outcomes may improve the situation. Methods A mathematical model of malaria transmission conforming to Zambia’s low transmission areas defined as areas with an incidence of fewer than 200 malaria cases per 1,000 population per year was developed to simulate RCD using parameters and data from published articles. We explored the impact of literature-identified challenges on RCD performance in malaria detection and potential strategies to enhance detection rates. The examined factors and improvement measures included increasing CHWs, adjusting reaction time, RDT sensitivity, and implementing focal mass drug administration (fMDA). Results Simulation findings suggest that a shortage of CHWs and limited availability of RDTs have the highest negative impact on RCD compared to other challenges. In scenarios where CHWs or RDT availability for RCD were reduced by 50%, annual malaria cases were predicted to increase by approximately 17%. Only the incorporation of fMDA as an improvement measure succeeded in countering the situation. Increasing CHWs to offset RCD inefficiencies caused by limited RDT sensitivity or difficulties in finding individuals resulted in fewer cases than improving reaction time or increasing the screening radius. Conclusions Participation of CHWs is voluntary and primarily motivated by informal incentives, often provided by donors. Finding sustainable means to ensure the sufficient availability of CHWs may guarantee continued RCD contributions towards maintaining stable malaria prevalence and elimination. More research is required to explore the application of RCD in archetypical transmission areas suitable for RCD as improvement measures to the identified challenges hindering RCD. Furthermore, archetype-based targeting of interventions, including RCD, may also be explored to inform the optimisation of intervention resource allocation to overcome the widening gap in malaria funding.

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