Population genomics of Plasmodium ovale species in sub-Saharan Africa

Abstract

Plasmodium ovale curtisi (Poc) and Plasmodium ovale wallikeri (Pow) are relapsing malaria parasites endemic to Africa and Asia that were previously thought to represent a single species. Amid increasing detection of ovale malaria in sub-Saharan Africa, we present a population genomic study of both species across the continent. We conducted whole-genome sequencing of 25 isolates from Central and East Africa and analyzed them alongside 20 previously published African genomes. Isolates are predominantly monoclonal (43/45), with their genetic similarity aligning with geography. Pow shows lower average nucleotide diversity (1.8×10⁻⁴) across the genome compared to Poc (3.0×10⁻⁴) (p < 0.0001). Signatures of selective sweeps involving the dihydrofolate reductase gene have been found in both species, as are signs of balancing selection at the merozoite surface protein 1 gene. Differences in the nucleotide diversity of Poc and Pow may reflect unique demographic history, even as similar selective forces facilitate their resilience to malaria control interventions.

Genomic analyses, performed by Carey-Ewend et al., reveal that Plasmodium ovale curtisi and wallikeri in sub-Saharan Africa show similar low complexity of infection, relatedness by geography, and signatures of selection. However, P. ovale wallikeri harbors lower nucleotide diversity.