Plasmodium vivax is geographically the most widely distributed cause of malaria in people, with up to 2·5 billion people at risk and an estimated 80 million to 300 million clinical cases every year—including severe disease and death. Despite this large burden of disease, P vivax is overlooked and left in the shadow of the enormous problem caused by Plasmodium falciparum in sub-Saharan Africa.

The technological advances enabling the sequencing of the P vivax genome and a recent call for worldwide malaria eradication have together placed new emphasis on the importance of addressing P vivax as a major public health problem. However, because of this parasite’s biology, it is especially difficult to interrupt the transmission of P vivax, and experts agree that the available methods for preventing and treating infections with P vivax are inadequate. It is thus imperative that the development of new methods and strategies become a priority.

Advancing the development of such methods needs renewed emphasis on understanding the biology, pathogenesis, and epidemiology of P vivax. This Review critically examines what is known about P vivax, focusing on identifying the crucial gaps that create obstacles to the elimination of this parasite in human populations.

An article published Online First and in a future edition of The Lancet reports that protecting houses with screening measures can substantially decrease both the numbers of malaria-carrying mosquitoes and the occurrence of anaemia related to malaria in children leaving in those homes. The article is the work of Dr Matthew J Kirby, Durham University, UK (now at Wageningen University, The Netherlands), and Professor Steve W Lindsay, Durham University, UK (now at the London School of Hygiene and Tropical Medicine [LSHTM], UK), and colleagues at the Medical Research Council’s (MRC) Laboratories in The Gambia and the LSHTM. The study was funded by the MRC.

The researchers considered two types of screening:

• Full screening of windows, doors, and closing eaves and other holes where mosquitoes could enter.
• Installation of screened ceilings only.

They examined whether either of these screenings could avoid house entry of mosquitoes and as a result reduce anaemia in children in an area of seasonal malaria transmission. They studied in this case the town of Farafenni in The Gambia. The authors assessed a total of 462 houses of which 188 had full screening, 178 had screened ceilings and 96 had no screening. Mosquitoes that entered the homes were caught using traps.

Results showed that the numbers of mosquitoes in the houses with screened ceilings fell by 49 percent and 59 percent with full screening. Children in either partly screened or fully-screened homes were about half as likely to have malaria-related anaemia as those in unscreened properties. The authors explain: “House screening could be easily incorporated into integrated vector management programmes, and because it does not rely on insecticides, it could be particularly beneficial in areas where insecticide resistance develops…We would encourage the initiation of a larger trial to assess whether this intervention reduces clinical episodes of malaria in diverse settings, including areas where use of insecticide-treated bednets is high. We also hope that the results of our trial will stimulate the development of additional sustainable methods that, in combination with improved health care and access to treatment, can help to strengthen efforts to eliminate malaria.”

In an associated note, Dr Laurence Slutsker, and Dr John E Gimnig, Centers for Disease Control and Prevention, Atlanta, GA, USA, mention that the contribution in the past of house screening in malaria control and elimination may have been more important than previously thought. However, additional research is necessary to establish when and how this strategy should be incorporated with other vector control interventions such as treated bed nets with long-lasting insecticide (LLINs) to provide added (or synergistic) benefits.