Malaria-related mortality is falling, due in part to the implementation of rapid diagnostic tests (RDTs) and artemisinin-based combination therapy (ACT) treatment programs. RDTs have become the primary modality for diagnosis of malaria globally, including in Sub-Saharan Africa. Most widely used RDTs rely on the detection of histidine-rich protein 2 (HRP2), an antigen specific to P? lasmodium falciparum? encoded by the ?pfhrp2? gene. However, false-negative results have recently been reported in individuals infected with P? . falciparum ?parasites harboring a deletion of the ?pfhrp2? gene with or without a deletion in a related histidine-rich protein gene, pfhrp3?. These parasites have been commonly described in South America and sporadically in other regions, including Africa. Until recently, the prevalence and impact of ?pfhrp2? deletions deletions in Africa was unknown. We recently completed a large cross-sectional survey of more than 7,000 children in the Democratic Republic of Congo (DRC), where RDTs have been the primary mode of diagnosis since 2011. We found that 6.4% of parasitemic children had false-negative RDTs due to a p? fhrp2? deletion. In Kinshasa province, more than 20% of infections were due to ?pfhrp2?-deleted parasites. Similar findings are being made in other parts of Sub-Saharan Africa, raising the possibility that HRP2-based RDTs are becoming ineffective. Currently, our collaborators are conducting a longitudinal cohort study in Kinshasa to evaluate the epidemiology of ?pfhrp2/3 deleted parasites. Our proposal will leverage this cohort to achieve our short-term goals to (1) understand the evolutionary drivers of these deletions in the DRC, the country in Africa with the second-highest malaria burden; and (2) to develop a simple PCR assay for ?pfhrp2/3? deletion surveillance so that malaria control programs can implement alternative diagnostics when needed. Our long-term goal is to develop alternate biomarkers and noninvasive diagnostic tests for malaria diagnosis and test them in an area of HRP2-based RDT failure. This proposal is unique in that it will help characterize an emerging public health problem while simultaneously seeking solutions. As a result, there is a high likelihood that the results of this research will significantly impact the next generation of point of care malaria diagnostic tests.
The emergence of ?diagnosis-resistant? malaria in Africa has the potential to be a public health disaster, as appropriate treatment relies on appropriate diagnosis. Our previous work has shown that parasites lacking the genes encoding the protein most rapid diagnostic tests use, which results in a false-negative test, are now quite common in some areas of Africa. This proposal will help answer important questions about how and why these parasites have emerged, and will discover and test new novel approaches for diagnosing malaria where current tests are failing.
