Deployment of Molecular Tools to Track the Epidemiology of Plasmodium Vivax in Panama

Abstract Background: As the elimination of malaria in Mesoamerica progresses, detection of Plasmodium vivax asymptomatic patients using conventional diagnostic methods becomes more difficult. Highly sensitive molecular methods are key for the determination of the hidden reservoir of malaria transmission on the road to elimination in countries in the pre-elimination phase such as Panama. Here we describe the clinical validation of a qRT-PCR assay for the detection of P. vivax asexual and sexual stages from low blood volume field samples preserved at ambient temperature. Methods: We collected blood samples from a cross sectional cohort of P. vivax patients in Panama. Different storage formats (room temperature, frozen) and blood volumes were compared to establish the sensitivity of parasite detection including transmission stages (gametocytes) by qRT-PCR and diagnostic microscopy. Results: Study results indicated that blood storage at room temperature using an RNA preservation solution for up to 8 days was sufficient to preserve RNA for subsequent qRT-PCR assays. Detection of gametocytes by qRT-PCR was more sensitive than light microscopy using both our recently established marker PvLAP5 and the gold standard Pvs25, confirming that both markers are suitable for P. vivax gametocyte detection in the field using the above protocol.Conclusions: This study validates a low blood volume qRT-PCR assay system for the detection of P. vivax asexual and sexual stages in field samples preserved at ambient temperature. Results indicate that the assay system is a reliable tool to determine the transmission reservoir of P. vivax in remote areas such as endemic regions of Panama.