Community-based surveys for Plasmodium falciparum pfhrp2 and pfhrp3 gene deletions in selected regions of mainland Tanzania

Background: Despite recent reports of false negative results among histidine-rich protein 2 (HRP2) based-malaria rapid diagnostic tests (mRDTs) caused by pfhrp2/3 gene deletions in different countries, there is paucity of data in Tanzania. Methods: This study assessed the status of pfhrp2/3 deletions in 7,543 blood sample using laboratory multiplex antigen detection (Plasmodium lactate dehydrogenase - pLDH, aldolase, and HRP2). Samples showing mRDT false negativity or aberrant relationship of HRP2 to pan-Plasmodium antigens were genotyped for pfhrp2/3 genes. Results: Of all samples, 2,417 (32.0%) were positive for any Plasmodium antigens while 5,126 (68.0%) were negative. About 99.8% (n=2,411) of antigen positive samples had HRP2, but 6 (0.2%) had only pLDH and/or pAldolase. Thirteen samples had atypical relationships between pan-Plasmodium antigens and HRP2, but were positive by PCR. An additional 16 samples with negative HRP2 mRDTs but positive by microscopy were also chosen; all giving 35 samples genotyped for pfhrp2/3. Of 35 samples, 4 (11.4%) failed to consistently amplify positive control genes (pfmsp1 and pfmsp2), and pfhrp2 and pfhrp3 genes were successfully amplified in 31 (88.6%) samples. Conclusions: Lack of pfhrp2 and/or pfhrp3 genes deletions in Plasmodium falciparum parasites supports continued use of HRP2-based mRDTs for routine malaria diagnosis in Tanzania.