Molecular detection and quantification of Plasmodium falciparum gametocytes carriage in used RDTs in malaria elimination settings in northern Senegal

BACKGROUND: Malaria surveillance requires powerful tools and strategies to achieve malaria elimination. Rapid diagnostic tests for malaria (RDTs) are easily deployed on a large scale and are helpful sources of parasite DNA. The application of sensitive molecular techniques to these RDTs is a modern tool for improving malaria case detection and drug resistance surveillance. Several studies have made it possible to extract the DNA of Plasmodium falciparum from RDTs. The knowledge of gametocyte carriage in the population is important to better assess the level of parasite transmission in elimination settings. The aim of this study was to detect P. falciparum gametocytes from used RDTs by quantitative PCR for molecular monitoring of malaria transmission. METHODS: DNA was extracted from 303 RDT devices (SD Bioline Malaria Pf) using the Chelex-100 protocol. qPCR was performed in a 20 μL reaction to detect and quantify transcripts of the pfs25 gene. The cycle threshold (Ct) was determined by the emission fluorescence corresponding to the initial amount of amplified DNA. RESULTS: The study found an overall prevalence of 53.47% with an average Ct of 32.12 ± 4.28 cycles. In 2018, the prevalence of gametocytes was higher in the Ranérou district (76.24%) than in the Saint-Louis district (67.33%) where an increase in the number of gametocyte carriers in 2018 was noted, in comparison with 2017. CONCLUSIONS: RDTs are a good source of DNA for molecular monitoring of gametocyte carriage. This method is a simple and effective tool to better understand the level of malaria transmission with a view to elimination.