Limited Degradation of the Plasmodium falciparum Gametocyte Marker pfs25 mRNA Exposed to Tropical Temperatures: Considerations for Malaria Transmission Field Studies

Abstract An important aspect of many malaria molecular epidemiology and transmission studies is RNA-based detection of gametocytes. Ensuring RNA stability represents a challenge in tropical, resource-limited environments, as RNA may quickly degrade when samples are not preserved under adequate conditions. This study investigated the degradation of pfs25 messenger RNA (mRNA), the most widely used Plasmodium falciparum gametocyte marker, in whole blood spiked with cultured P. falciparum gametocytes, exposed to different temperatures for up to 48 hours, and collected with different anticoagulants. The levels of pfs25 mRNA were similar between samples stored at 4°C and 30°C for up to 48 hours before stabilization with RNAprotect (Qiagen, Hilden, Germany). We observed that pfs25 mRNA in heparin-collected blood degraded less than that in ethylenediaminetetraacetic acid (EDTA)–collected blood over the 48-hour period. For field studies aiming for P. falciparum gametocyte detection, immediate stabilization of blood samples is not necessary, as the pfs25 transcript is relatively stable, more so in heparin than EDTA collection tubes.