pfhrp2 and pfhrp3 gene deletions that affect malaria rapid diagnostic tests for Plasmodium falciparum: analysis of archived blood samples from three African countries

Background Malaria rapid diagnostic tests (mRDT) that target histidine-rich protein 2 (HRP2) are important tools for Plasmodium falciparum diagnosis. Parasites with pfhrp2/3 gene deletions threaten the use of these mRDTs, and have been reported in Africa, Asia, and South America. We studied blood samples from three African countries to determine if these gene deletions were present. Methods We analysed 911 dried blood spots from Ghana (165), Tanzania (176) and Uganda (570). P.falciparum infection was confirmed by 18SrDNA polymerase-chain reaction (PCR), and pfhrp2/3 genes were genotyped. True pfhrp2/3 gene deletions were confirmed if samples were (1) microscopy positive, (2) 18SrDNA PCR positive, (3) positive for merozoite surface protein genes by PCR, or positive by loop-mediated isothermal amplification, and (4) quantitative PCR positive with > 5 parasites/µl. Results No pfhrp2/3 deletions were detected in samples from Ghana, but deletions were identified in Tanzania (three pfhrp2; two pfhrp3) and Uganda (seven pfhrp2; two pfhrp3). Of the 10 samples with pfhrp2 deletions, nine tested negative by HRP2-based mRDT. Discussion The presence of pfhrp2/3 deletions in Tanzania and Uganda, along with reports of pfhrp2/3-deleted parasites in neighbouring countries, reinforces the need for systematic surveillance to monitor the reliability of mRDTs in malaria-endemic countries.