Evaluation of optimized strategies for the detection and treatment of asymptomatic malaria infections in the Peruvian Amazon

Malaria remains a public health problem in the Peruvian Amazon. To understand malaria transmission in riverine communities of Mazan district in the Peruvian Amazon, we combined parasitological, entomological, and environmental observations. Despite heterogeneity across communities, the prevalence of submicroscopic malaria infections was high and mainly due to Plasmodium vivax. Furthermore, housing with incomplete walls was the main risk factor for malaria, and communities in Mazan basin had higher entomological indicators, prevalence, and incidence rates than communities in the Napo basin. In that scenario and considering that routine malaria surveillance is based on passive case detection (PCD) using light microscopy (LM) for malaria diagnosis, we conducted two cross-sectional studies to estimate the economic costs associated with passive case detection (PCD) and management of uncomplicated malaria episodes and explore whether healthcare-seeking behaviours significantly influence those costs. Although malaria case management was free, there was a delay in seeking care, and the costs of uncomplicated malaria incurred by families were mainly indirect costs due to loss of working days. Since the Peruvian Ministry of Health (MoH) improved routine malaria surveillance by the addition of an optimized strategy recommended by the World Health Organization (WHO) known as active case detection (ACD) to overcome the limitations of the routine malaria surveillance based on PCD using LM for detecting both asymptomatic infected individuals and symptomatic individuals that do not attend the health services, a population-based cohort study was conducted to assess the effectiveness of this optimized strategy based on ACD using light microscopy (LM) compared with quantitative real-time polymerase chain reaction (qPCR). The optimized ACD-strategy using LM had less effectiveness than qPCR. Furthermore, qPCR results confirmed that most malaria infections were asymptomatic, submicroscopic, and mainly due to P. vivax. As asymptomatic and submicroscopic malaria infections are common, undetected, and untreated using a standard diagnostic test such as light microscopy due to low effectiveness, optimized strategies based on ACD using molecular tests added to PCD could reduce the malaria burden in the Peruvian Amazon. However, to ensure optimal allocation of resources for malaria elimination, Peruvian stakeholders should consider implementing mass drug administration (MDA) with a single treatment using artemisinin-based combination therapy (ACT) plus primaquine or tafenoquine for uncomplicated malaria by both P. falciparum and P. vivax infections. Furthermore, high heterogeneity in malaria transmission creates opportunities for targeted control interventions such as MDA in clusters of high malaria prevalence.