Poster Presentation Lorne Infection and Immunity 2013

Molecular epidemiology of the two recently described subspecies of Plasmodium ovale in Papua New Guinea (#131)

Charlie Jennison 1 2 , Benita Knox 1 2 , Raksmei Keo 1 , Celine Barnadas 1 2 3 , Mary Oguike 4 , Inoni Betuela 3 , Peter M Siba 3 , Ivo Mueller 1 2 5 , Colin J Sutherland 4 , Alyssa E Barry 1 2
  1. WEHI, Parkville, Vic, Australia
  2. Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
  3. Papua New Guinea Institute of Medical Research, Goroka, Papua New Guinea
  4. London School of Hygiene and Tropical Medicine, London, UK
  5. Centre de Recerca en Salut Internacional de Barcelona, Barcelona, Spain

Plasmodium ovale has been recognised as one of four human infecting malarias since it’s discovery by Stevens in 1922.  The last human malaria species to be described, P. ovale is frequently misdiagnosed as Plasmodium vivax and our understanding lags far behind that of the other human malarias. In 2010 multi-locus sequencing of P. ovale isolates from Africa and the Asia Pacific led to the discovery that P. ovale consists of two non-recombining species; P. ovale curtisi (Poc) and P. ovale wallikeri (Pow), which occur in sympatry.  Advances in molecular diagnostic techniques have shown P. ovale to be more common and widely spread than was previous thought.  Indeed, far from being a minor pathogen, P. ovale s.l. is now estimated to cause upwards of 15 million cases of malaria each year in Africa alone. Intensification of malaria control efforts have shown that strategies targeting falciparum malaria (which causes the most mortality and morbidity globally) are not as effective against other species due to significant biological and epidemiological differences, with perhaps the most important being relapsing liver stages of both P. vivax and P. ovale s.l.

The aim of this study was to investigate the prevalence of the two newly described P. ovale subspecies in Papua New Guinea (PNG), which has intense perennial malaria transmission. Using multi-locus sequencing and highly sensitive qPCR assays on a panel of 52 unconfirmed P. ovale isolates, we have detected both species with confirmation of 67.3% Poc and 7.7% Pow amongst the sample set. Sequence data of the three conserved loci surveyed do not indicate there is additional genetic diversity of P. ovale in PNG.

With improved diagnostic tools we now aim to achieve a more accurate understanding ofthe epidemiology of both P. ovale subspecies and ascertain the true burden of ovale malaria in PNG.