Two nonrecombining sympatric forms of the human malaria parasite Plasmodium ovale occur globally.
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.
Sutherland
Colin J
CJ
Health Protection Agency Malaria Reference Laboratory, Immunology Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom. colin.sutherland@lshtm.ac.uk
Tanomsing
Naowarat
N
Nolder
Debbie
D
Oguike
Mary
M
Jennison
Charlie
C
Pukrittayakamee
Sasithon
S
Dolecek
Christiane
C
Hien
Tran Tinh
TT
do Rosário
Virgilio E
VE
Arez
Ana Paula
AP
Pinto
João
J
Michon
Pascal
P
Escalante
Ananias A
AA
Nosten
Francois
F
Burke
Martina
M
Lee
Rogan
R
Blaze
Marie
M
Otto
Thomas Dan
TD
Barnwell
John W
JW
Pain
Arnab
A
Williams
John
J
White
Nicholas J
NJ
Day
Nicholas P J
NP
Snounou
Georges
G
Lockhart
Peter J
PJ
Chiodini
Peter L
PL
Imwong
Mallika
M
Polley
Spencer D
SD
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
D012335:RNA, Ribosomal