How prevalent are Plasmodium ovale and P. malariae in East Asia?

Plasmodium ovale and Plasmodium malariae, two of the four human malaria parasites, are usually found at very low prevalence in East Asia, even in areas with intense malaria transmission. In this article, Fumihiko Kawamoto, Qing Liu, Marcelo Ferreira and Indah Tantular review data obtained in recent field surveys, using alternative diagnostic methods such as acridine orange staining and PCR-based methods, to evaluate the prevalence of these two malaria species in East Asia. They argue that these species might be much more prevalent in East Asia than reported previously. In addition, they discuss the implications of sequence variations found in the small subunit ribosomal RNA genes of the two species targeted by diagnostic PCR and compare morphological criteria for speciation of malaria parasites stained with Giemsa and acridine orange.