title: Two nonrecombining sympatric forms of the human malaria parasite Plasmodium ovale occur globally.
abstract: BACKGROUND
  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.
authors.affiliation: Health Protection Agency Malaria Reference Laboratory, Immunology Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom. colin.sutherland@lshtm.ac.uk
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Sutherland
authors.forename: Naowarat
authors.initials: N
authors.lastname: Tanomsing
authors.forename: Debbie
authors.initials: D
authors.lastname: Nolder
authors.forename: Mary
authors.initials: M
authors.lastname: Oguike
authors.forename: Charlie
authors.initials: C
authors.lastname: Jennison
authors.forename: Sasithon
authors.initials: S
authors.lastname: Pukrittayakamee
authors.forename: Christiane
authors.initials: C
authors.lastname: Dolecek
authors.forename: Tran Tinh
authors.initials: TT
authors.lastname: Hien
authors.forename: Virgilio E
authors.initials: VE
authors.lastname: do Rosário
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Arez
authors.forename: João
authors.initials: J
authors.lastname: Pinto
authors.forename: Pascal
authors.initials: P
authors.lastname: Michon
authors.forename: Ananias A
authors.initials: AA
authors.lastname: Escalante
authors.forename: Francois
authors.initials: F
authors.lastname: Nosten
authors.forename: Martina
authors.initials: M
authors.lastname: Burke
authors.forename: Rogan
authors.initials: R
authors.lastname: Lee
authors.forename: Marie
authors.initials: M
authors.lastname: Blaze
authors.forename: Thomas Dan
authors.initials: TD
authors.lastname: Otto
authors.forename: John W
authors.initials: JW
authors.lastname: Barnwell
authors.forename: Arnab
authors.initials: A
authors.lastname: Pain
authors.forename: John
authors.initials: J
authors.lastname: Williams
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: White
authors.forename: Nicholas P J
authors.initials: NP
authors.lastname: Day
authors.forename: Georges
authors.initials: G
authors.lastname: Snounou
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lockhart
authors.forename: Peter L
authors.initials: PL
authors.lastname: Chiodini
authors.forename: Mallika
authors.initials: M
authors.lastname: Imwong
authors.forename: Spencer D
authors.initials: SD
authors.lastname: Polley
mesh_terms: D000818:Animals; D014644:Genetic Variation; D005838:Genotype; D014943:Global Health; D006801:Humans; D008288:Malaria / Q000453:epidemiology / Q000469:parasitology*; D010802:Phylogeny; D041122:Plasmodium ovale / Q000145:classification / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics
chemical_list: D012335:RNA, Ribosomal