Characterization of Plasmodium ovale curtisi and P. ovale wallikeri in Western Kenya utilizing a novel species-specific real-time PCR assay

Plasmodium ovale is comprised of two genetically distinct subspecies, P. ovale curtisi and P. ovale wallikeri. Although P. ovale subspecies are similar based on morphology and geographical distribution, allelic differences indicate that P. ovale curtisi and P. ovale wallikeri are genetically diverge...

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Bibliographic Details
Published in:PLoS neglected tropical diseases 2015-01, Vol.9 (1), p.e0003469-e0003469
Main Authors: Miller, Robin H, Obuya, Clifford O, Wanja, Elizabeth W, Ogutu, Bernhards, Waitumbi, John, Luckhart, Shirley, Stewart, V Ann
Format: Article
Language:English
Subjects:
Base Sequence
Chemical properties
Distribution
DNA sequencing
Genes
Genetic aspects
Genotype
Health aspects
Humans
Identification and classification
Kenya - epidemiology
Malaria
Malaria - epidemiology
Microscopy
Nucleotide sequencing
Parasites
Plasmodium
Plasmodium falciparum
Plasmodium ovale
Plasmodium ovale - genetics
Plasmodium ovale - isolation & purification
Polymerase chain reaction
Prevention
Real-Time Polymerase Chain Reaction - methods
Reproducibility of Results
Sequence Analysis, DNA
Species Specificity
Studies
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Summary:Plasmodium ovale is comprised of two genetically distinct subspecies, P. ovale curtisi and P. ovale wallikeri. Although P. ovale subspecies are similar based on morphology and geographical distribution, allelic differences indicate that P. ovale curtisi and P. ovale wallikeri are genetically divergent. Additionally, potential clinical and latency duration differences between P. ovale curtisi and P. ovale wallikeri demonstrate the need for investigation into the contribution of this neglected malaria parasite to the global malaria burden. In order to detect all P. ovale subspecies simultaneously, we developed an inclusive P. ovale-specific real-time PCR assay based on conserved regions between P. ovale curtisi and P. ovale wallikeri in the reticulocyte binding protein 2 (rbp2) gene. Additionally, we characterized the P. ovale subspecies prevalence from 22 asymptomatic malaria infections using multilocus genotyping to discriminate P. ovale curtisi and P. ovale wallikeri. Our P. ovale rbp2 qPCR assay validation experiments demonstrated a linear dynamic range from 6.25 rbp2 plasmid copies/microliter to 100,000 rbp2 plasmid copies/microliter and a limit of detection of 1.5 rbp2 plasmid copies/microliter. Specificity experiments showed the ability of the rbp2 qPCR assay to detect low-levels of P. ovale in the presence of additional malaria parasite species, including P. falciparum, P. vivax, and P. malariae. We identified P. ovale curtisi and P. ovale wallikeri in Western Kenya by DNA sequencing of the tryptophan-rich antigen gene, the small subunit ribosomal RNA gene, and the rbp2 gene. Our novel P. ovale rbp2 qPCR assay detects P. ovale curtisi and P. ovale wallikeri simultaneously and can be utilized to characterize the prevalence, distribution, and burden of P. ovale in malaria endemic regions. Using multilocus genotyping, we also provided the first description of the prevalence of P. ovale curtisi and P. ovale wallikeri in Western Kenya, a region holoendemic for malaria transmission.
ISSN:1935-2735
1935-2727
1935-2735
DOI:10.1371/journal.pntd.0003469