Executive Summary : | Plasmodium falciparum encoded histidine rich protein (HRP2) based malaria rapid diagnostic tests (RDTs) are used in India. Deletion of PFHRP2 and PFHRP3 genes contributes to false negative test results. In this study, microscopically confirmed P. falciparum but RDT negative samples were assessed for presence of pfhrp2, pfhrp3, and their flanking genes using PCR. We also analysed natural variations in PfHRP2 and PfHRP3 sequences from Indian isolates and correlated these variations with RDT reactivity. Among 1521 microscopically positive P. falciparum samples screened, 50 were negative by HRP2 based RDT test. Molecular testing was carried out using these 50 RDT negative samples by assuming that 1471 RDT positive samples carried pfhrp2 gene. A total of 16 distinct repeat motifs were observed for PFHRP2 and 11 for Pfhrp3, including some new repeat types. No correlation was found between variations in the size of Pfhrp2 repeat types 2 and 7, nor between any combinations of repeat motifs, and performance of a commercial RDT at low parasite densities. Mixed Plasmodium spp. infections were detected by PCR in 17.4% (265/1,521) of blood samples that microscopy had shown to contain only P. falciparum. This study provides evidence for low level presence of pfhrp2 and pfhrp3 deleted P. falciparum parasites in different endemic regions of India, and periodic surveillance is warranted for reliable use of PFHRP2 based RDTs. The findings suggest that sequence diversity in Pfhrp2 and Pfhrp3 genes in Indian isolates is not likely to negatively influence performance of currently used PFHRP2 RDTs. |
Co-PI: | Dr. Praveen Kumar Bharti, Scientist D, National Institute for Research in Tribal Health (NIRTH), Madhya Pradesh, Dr. MM Shukla, Scientist, National Institute for Research in Tribal Health (NIRTH), Madhya Pradesh, Mr. M. P. Singh, Scientist, National Institute for Research in Tribal Health (NIRTH), Madhya Pradesh |