Plasmodium vivax in Oceania

Abstract

Of the five species of malaria parasites infecting humans, Plasmodium vivax has the widest global distribution, with more than 80 million people infected each year (Price et al. Am J Trop Med Hyg 77:79-87, 2007) and 2.5 billion people at risk (Gething et al. PLoS Negl Trop Dis 6:e1814, 2012). Despite this, the majority of malaria research has focused on Plasmodium falciparum, responsible for the high burden of malaria-related morbidity and mortality in sub-Saharan Africa (Hay et al. Lancet Infect Dis 4:327-336, 2004), leaving P. vivax an important but neglected tropical disease requiring attention. Historically, malaria transmission in the Oceania region has been high with endemicity comparable to sub-Saharan Africa and ranging from holo-or hyperendemic in Papua/West Papua provinces of Indonesia and the coastal and lowland areas of Papua New Guinea to meso-and hypoendemic in the archipelago of islands that comprise the Solomon Islands and Vanuatu, respectively. P. vivax is endemic in all four of these locations and the predominant Plasmodium spp. infection in at least two of them. P. vivax resistance to chloroquine is widespread, and primaquine, the only drug currently available for radical cure, has poor compliance to its 14-day regime and carries the risk of potentially life-threatening haemolysis in individuals with glucose-6-phosphate dehydrogenase deficiency. As malaria vectors in Oceania are often outdoor biting and resting, P. vivax is less vulnerable to traditional vector control measures such as bed nets and indoor residual spraying, and P. vivax can cause a large-scale resurgence when control measures are weakened, as witnessed in this region in the 1970s. Thus there is a growing recognition that P. vivax poses major, unresolved challenges to the control of malaria in Oceania and that without new tools specifically addressing these challenges, endemic countries in this region will continue to struggle to meet their malaria control and elimination targets.