RT Journal Article
SR Electronic
T1 An observational study of malaria in British travellers: Plasmodium ovale wallikeri and Plasmodium ovale curtisi differ significantly in the duration of latency
JF BMJ Open
JO BMJ Open
FD British Medical Journal Publishing Group
SP e002711
DO 10.1136/bmjopen-2013-002711
VO 3
IS 5
A1 Debbie Nolder
A1 Mary C Oguike
A1 Hector Maxwell-Scott
A1 Hatoon A Niyazi
A1 Valerie Smith
A1 Peter L Chiodini
A1 Colin J Sutherland
YR 2013
UL http://bmjopen.bmj.com/content/3/5/e002711.abstract
AB Objectives Ovale malaria is caused by two closely related species of protozoan parasite: Plasmodium ovale curtisi and Plasmodium ovale wallikeri Although clearly distinct genetically, there have been no studies comparing the morphology, life cycle or epidemiology of these parasites. We tested the hypothesis that the two species differ in the duration of latency prior to presentation with symptoms of blood-stage infection. Design PCR was used to identify P ovale curtisi and P ovale wallikeri infections among archived blood from UK malaria patients. Latency periods, estimated as the time between entry into the UK and diagnosis of malaria, were compared between the two groups. Setting UK National Reference Laboratory. Participants None. Archived parasite material and surveillance data for 74 P ovale curtisi and 60 P ovale wallikeri infections were analysed. Additional epidemiological data were taken from a database of 1045 imported cases. Outcomes None. Results No differences between the two species were identified by a detailed comparison of parasite morphology (N=9, N=8, respectively) and sex ratio (N=5, N=4) in archived blood films. The geometric mean latency period in P ovale wallikeri was 40.6 days (95% CI 28.9 to 57.0), whereas that for P ovale curtisi was more than twice as long at 85.7 days (95% CI 66.1 to 111.1; p=0.002). Further, the proportion of ovale malaria sensu lato which occurred in patients reporting chemoprophylaxis use was higher than for Plasmodium falciparum (OR 7.56; p<0.0001) or P vivax (OR 1.82; p<0.0001). Conclusions These findings provide the first difference of epidemiological significance observed between the two parasites which cause ovale malaria, and suggest that control measures aimed at P falciparum may not be adequate for reducing the burden of malaria caused by P ovale curtisi and P ovale wallikeri.