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Title: Utility of ultra-sensitive qPCR to detect Plasmodium falciparum and Plasmodium vivax infections under different transmission intensities
Authors: Maria Gruenberg
Clara Antunes Moniz
Natalie E. Hofmann
Cristian Koepfli
Leanne J. Robinson
Elma Nate
Wuelton Marcelo Monteiro
Gisely Cardoso de Melo
Andrea Kuehn
Andre M. Siqueira
Wang Nguitragool
Quique Bassat
Marcus Lacerda
Jetsumon Sattabongkot
Ivo Mueller
Ingrid Felger
Instituto de Salud Global de Barcelona
Papua New Guinea Institute of Medical Research
Walter and Eliza Hall Institute of Medical Research
University of Melbourne
Universitat Basel
Swiss Tropical and Public Health Institute (Swiss TPH)
University of Notre Dame
Mahidol University
Burnet Institute
Universidade do Estado do Amazonas
Institut Pasteur, Paris
Fundação de Medicina Tropical Dr. Heitor Vieira Dourado
Instituto Nacional de Infectologia Evandro Chagas
Keywords: Immunology and Microbiology;Medicine
Issue Date: 3-Sep-2020
Citation: Malaria journal. Vol.19, No.1 (2020), 319
Abstract: BACKGROUND: The use of molecular diagnostics has revealed an unexpectedly large number of asymptomatic low-density malaria infections in many malaria endemic areas. This study compared the gains in parasite prevalence obtained by the use of ultra-sensitive (us)-qPCR as compared to standard qPCR in cross-sectional surveys conducted in Thailand, Brazil and Papua New Guinea (PNG). The compared assays differed in the copy number of qPCR targets in the parasite genome. METHODS: Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) parasites were quantified by qPCR amplifying the low-copy Pf_ and Pv_18S rRNA genes or the multi-copy targets Pf_varATS and Pv_mtCOX1. Cross-sectional surveys at the three study sites included 2252 participants of all ages and represented different transmission intensities. RESULTS: In the two low-transmission areas, P. falciparum positivity was 1.3% (10/773) (Thailand) and 0.8% (5/651) (Brazil) using standard Pf_18S rRNA qPCR. In these two countries, P. falciparum positivity by Pf_varATS us-qPCR increased to 1.9% (15/773) and 1.7% (11/651). In PNG, an area with moderate transmission intensity, P. falciparum positivity significantly increased from 8.6% (71/828) by standard qPCR to 12.2% (101/828) by us-qPCR. The proportions of P. falciparum infections not detected by standard qPCR were 33%, 55% and 30% in Thailand, Brazil and PNG. Plasmodium vivax was the predominating species in Thailand and Brazil, with 3.9% (30/773) and 4.9% (32/651) positivity by Pv_18S rRNA qPCR. In PNG, P. vivax positivity was similar to P. falciparum, at 8.0% (66/828). Use of Pv_mtCOX1 us-qPCR led to a significant increase in positivity to 5.1% (39/773), 6.4% (42/651) and 11.5% (95/828) in Thailand, Brazil, and PNG. The proportions of P. vivax infections missed by standard qPCR were similar at all three sites, with 23%, 24% and 31% in Thailand, Brazil and PNG. CONCLUSION: The proportional gains in the detection of P. falciparum and P. vivax infections by ultra-sensitive diagnostic assays were substantial at all three study sites. Thus, us-qPCR yields more precise prevalence estimates for both P. falciparum and P. vivax at all studied levels of endemicity and represents a significant diagnostic improvement. Improving sensitivity in P. vivax surveillance by us-qPCR is of particular benefit, because the additionally detected P. vivax infections signal the potential presence of hypnozoites and subsequent risk of relapse and further transmission.
ISSN: 14752875
Appears in Collections:Scopus 2020

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