The utilization of rapid diagnostic tests (RDTs) as an alternative to microscopic diagnosis of malarial infections is increasing, especially in remote rural communities with limited health facilities and a lack of trained personnel. Reports on parasites circulating in the Peruvian Amazon lacking regions of the Pfhrp2 and/or Pfhrp3 gene, thus restricting the reliability of HRP2-detecting RDTs for diagnosis of P. falciparum raise considerable concern, especially since HRP-2-based rapid diagnostic tests are currently the most commonly used for P. falciparum detection.
In a retrospective cross sectional molecular survey, we assessed the extent of deletions in the Pfhrp2, Pfhrp3 and flanking genes in 23 isolates from malaria positive patients collected in the period January to September 2010. The deletion screening method (CDC Atlanta) consists of a set of PCR-assays for amplification of the parasite Pfhrp2/Pfhrp3 genes (exon 2 and an overlapping region of exon 1 and exon 2) as well as their immediate upstream and downstream flanking genes Mal7P1.228 & 230 and Mal13P1.475 & 485. The test system was successfully set up in Suriname and the HRP-deletion analysis revealed that 91% of the tested samples displayed no sign of deletions in either hrp2, hrp3 or the flanking genes.
The extent of HRP-deletions in this study is at least 4.6% for the Pfhrp3 gene, which is considerably lower than the results in Peruvian samples, where a PCR failure was described of 36% and 67% for the Pfhrp2 and the Pfhrp3 genes respectively, with 15.78% of samples positive for both genes. In Suriname, we do not have documented evidence of RDT failure in the field and with more than 90% of Suriname’s P. falciparum samples still harboring intact Pfhrp2 and Pfhrp3 genes, we do not yet expect the performance of HRP-2 based rapid diagnostic tests to be significantly impaired.
Currently, an international survey is being conducted to assess the prevalence of hrp2/3 genetic deletions in South American countries. The samples from this study have been sent to CDC for inclusion in this collaborative endeavor.
Variation in Plasmodium falciparum Histidine-Rich Protein 2 (Pfhrp2) and Plasmodium falciparum Histidine-Rich Protein 3 (Pfhrp3) Gene Deletions in Guyana and Suriname
PLoS One 10(5): e 0126805 (2015)