New rapid one-step PCR diagnostic assay for Plasmodium falciparum infective mosquitoes

Abstract

An essential component of malaria vector control programmes is the detection of Plasmodium falciparum within its mosquito vectors, particularly in the salivary glands where the infective sporozoites reside. Several protocols have been developed for this purpose; however they require dissection of mosquito specimens prior to analysis. Here, a novel one-step RT-qPCR TaqMan diagnostic assay was developed for mosquitoes with infective Plasmodium falciparum sporozoites in the salivary glands. It is based on detection of the sporozoite-specific Pfslarp and Pfplp1 gene transcripts. These transcripts were chosen based on bioinformatics analysis, and experimentally verified to be overexpressed in the salivary gland sporozoite stage of the parasite compared to other mosquito parasite stages. The proof of principle and the performance of the assay were demonstrated using RNAlater preserved mosquito samples. Tests of analytical sensitivity showed the novel TaqMan assay to be 100% accurate, although its performance in the field needs to be further demonstrated. This method has no requirement for dissection and post-PCR processing and thus is simple and rapid to perform in individual mosquitoes or mosquito pools. It can be used in single or multiplex formats also targeting additional markers expressed in different tissues, such as detoxification enzymes associated with insecticide resistance.