Colin J. SutherlandNaowarat TanomsingDebbie NolderMary OguikeCharlie JennisonSasithon PukrittayakameeChristiane DolecekTran Tinh HienVirgilio E. Do RosárioAna Paula ArezJoão PintoPascal MichonAnanias A. EscalanteFrancois NostenMartina BurkeRogan LeeMarie BlazeThomas Dan OttoJohn W. BarnwellArnab PainJohn WilliamsNicholas J. WhiteNicholas P.J. DayGeorges SnounouPeter J. LockhartPeter L. ChiodiniMallika ImwongSpencer D. PolleyHealth Protection AgencyLondon School of Hygiene & Tropical MedicineUCLChurchill HospitalSanger Genome CentreMahidol UniversityRoyal InstituteShoklo Malaria Research UnitUniversity of OxfordUniversidade Nova de Lisboa, Instituto de Higiene e Medicina TropicalPapua New Guinea Institute of Medical ResearchArizona State UniversityCenters for Disease Control and PreventionWestmead HospitalInsermFaculte de Medecine Pierre et Marie CurieNational University of SingaporeMassey University2018-09-242018-09-242010-05-15Journal of Infectious Diseases. Vol.201, No.10 (2010), 1544-1550002218992-s2.0-77951891892https://repository.li.mahidol.ac.th/handle/20.500.14594/29660Background. Malaria in humans is caused by apicomplexan parasites belonging to 5 species of the genus Plasmodium. Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease is not known. Dimorphism in defined genes has led to P ovale parasites being divided into classic and variant types. We hypothesized that these dimorphs represent distinct parasite species. Methods. Multilocus sequence analysis of 6 genetic characters was carried out among 55 isolates from 12 African and 3 Asia-Pacific countries. Results. Each genetic character displayed complete dimorphism and segregated perfectly between the 2 types. Both types were identified in samples from Ghana, Nigeria, São Tomé, Sierra Leone, and Uganda and have been described previously in Myanmar. Splitting of the 2 lineages is estimated to have occurred between 1.0 and 3.5 million years ago in hominid hosts. Conclusions. We propose that P ovale comprises 2 nonrecombining species that are sympatric in Africa and Asia. We speculate on possible scenarios that could have led to this speciation. Furthermore, the relatively high frequency of imported cases of symptomatic P ovale infection in the United Kingdom suggests that the morbidity caused by ovale malaria has been underestimated. © 2010 by the Infectious Diseases Society of America. All rights reserved.Mahidol UniversityMedicineArticleSCOPUS10.1086/652240