Abstract
The rapid and accurate diagnosis of Plasmodium falciparum malaria infection is an essential factor in malaria control. Currently, malaria diagnosis in the field depends heavily on using rapid diagnostic tests (RDTs) many of which detect circulating parasite-derived histidine-rich protein 2 antigen (PfHRP2) in capillary blood. P. falciparum strains lacking PfHRP2, due to pfhrp2 gene deletions, are an emerging threat to malaria control programs. The novel assay described here, named qHRP2/3-del, is well suited for high-throughput screening of P. falciparum isolates to identify these gene deletions. The qHRP2/3-del assay identified pfhrp2 and pfhrp3 deletion status correctly in 93.4% of samples with parasitemia levels higher than 5 parasites/µL when compared to nested PCR. The qHRP2/3-del assay can correctly identify pfhrp2 and pfhrp3 gene deletions in multiple strain co-infections, particularly prevalent in Sub-Saharan countries. Deployment of this qHRP2/3-del assay will provide rapid insight into the prevalence and potential spread of P. falciparum isolates that escape surveillance by RDTs.
Highlights
Malaria is an infectious disease with an estimated 219 million cases globally and was responsible for 435’000 deaths in 2017
This paper presents a novel, quantitative polymerase chain reaction (PCR)-based method for detecting pfhrp[2] and pfhrp[3] gene deletions suitable for high throughput screening of P. falciparum isolates
We aimed at improving the detection of pfhrp[2] and pfhrp[3] gene deletions by developing a quantitative PCR-based assay able to detect and quantify pfhrp[2] and pfhrp[3] genes in a single reaction
Summary
Malaria is an infectious disease with an estimated 219 million cases globally and was responsible for 435’000 deaths in 2017. In sub-Saharan Africa an estimated 75% of malaria tests conducted in 2017 were based on RDTs1. RDTs are critical diagnostic tools for identifying symptomatic malaria infections; due to the reduced performance in infections with low parasite density, its use for the diagnosis of malaria infection in asymptomatic individuals is rather limited[7]. Recent studies report on reduced diagnostic performance of PfHRP2-based RDTs which were attributed to genetic diversity of the pfhrp2/3 genes[6], differences in expression level of PfHRP2/3 antigen in parasite field strains[8] or isolates lacking pfhrp[2] and/or pfhrp[3] genes[9]. Since malaria control programmes depend on reliable diagnosis of malaria cases using RDTs, parasites lacking pfhrp2/3 genes pose a threat to malaria control and local elimination efforts[11]
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