Abstract
BackgroundMalaria rapid diagnostic tests (RDTs) play a key role in malaria management and control. The PfHRP-2 based RDT is the most widely used RDT for malaria diagnosis in Ghana. Deletion of pfhrp2 in Plasmodium falciparum parasites affect the diagnostic accuracy of PfHRP-2 based RDT kits. Identifying the prevalence and distribution of P. falciparum parasites with deleted pfhrp2 is important for malaria control.AimThe purpose of this study was to identify and confirm the prevalence of pfhrp2 deletant P. falciparum parasites circulating within different regions of Ghana.MethodsDNA was extracted from the membrane of spent CareStart™ PfHRP-2 RDT kits and dried filter paper blood blots using Chelex-100. Exon 2 of pfhrp2 and pfhrp3 genes were amplified by polymerase chain reaction (PCR), resolved by agarose gel electrophoresis and visualized under UV light.ResultsMicroscopic analysis of blood smears from samples that were PfHRP-2 RDT positive revealed a parasite prevalence of 54/114 (47.4 %) and 2/26 (7.7 %) in Accra and Cape Coast, respectively. PCR analysis increased parasite prevalence in the RDT positive samples to 94/114 (82.5 %) and 6/26 (23.1 %) in Accra and Cape Coast respectively. The exon 2 of the pfhrp2 gene was deleted in 18/54 (33.3 %) of the microscopy confirmed and 36.2 % (34/94) of the PCR confirmed RDT positive samples collected in Accra. No RDT sample, confirmed to contain parasites by either PCR or microscopy was negative by pfhrp2 exon 2 PCR in Cape Coast. A survey of an additional 558 DBS revealed that 22.4 % (46/205) and 40 % (44/110) of PCR positive samples in Accra and Cape Coast, respectively, lacked the exon 2 region of pfhrp2 and possibly the entire pfhrp2 gene.ConclusionsA high number of P. falciparum parasites, which lack pfhrp2 exon 2 gene have been identified in two communities in Ghana. Continuous nationwide monitoring of the prevalence of pfhrp2 deletant parasites would be essential to malaria control. The use of RDT kits that are effective at malaria diagnosis despite deletion of pfhrp2, such as the PfHRP-2/PfLDH combo RDT kit could enhance the diagnosis of clinical malaria in Ghana.
Highlights
Malaria rapid diagnostic tests (RDTs) play a key role in malaria management and control
The exon 2 of the pfhrp2 gene was deleted in 18/54 (33.3 %) of the microscopy confirmed and 36.2 % (34/94) of the polymerase chain reaction (PCR) confirmed RDT positive samples collected in Accra
No RDT sample, confirmed to contain parasites by either PCR or microscopy was negative by pfhrp2 exon 2 PCR in Cape Coast
Summary
Malaria rapid diagnostic tests (RDTs) play a key role in malaria management and control. The PfHRP-2 based RDT is the most widely used RDT for malaria diagnosis in Ghana. Deletion of pfhrp in Plasmodium falciparum parasites affect the diagnostic accuracy of PfHRP-2 based RDT kits. Identifying the prevalence and distribution of P. falciparum parasites with deleted pfhrp is important for malaria control. RDTs offer a great potential for rapid immediate diagnosis of malaria infections, which has led to prompt and appropriate treatment of the disease, in highly endemic rural settings [3]. Malaria RDT kits are designed to detect either Plasmodium falciparum or discriminately detect both P. falciparum in addition to another human malaria parasite or indiscriminately detect all human malaria parasites [4, 5]. Forty-five of these products detect only P. falciparum, ten detect P. falciparum as a part of a mixed infection with other human malaria parasites, one is Plasmodium vivax specific and 115 detect and distinguishing P. falciparum from either P. vivax mixed infections or mixed infections containing all the other human malaria parasites, P. vivax, P. ovale and P. malariae [10]
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