PvSeroRDT

The challenge

Most cases of malaria in sub-Saharan Africa are caused by Plasmodium falciparum (P.falciparum) However, a significant proportion are caused by a related species, Plasmodium vivax (P.vivax). This species, responsible for more than 500,000 cases a year, is particularly common in areas such as the Horn of Africa and is becoming more important as control of P. falciparum improves. Ultimately, eliminating malaria will require effective control of both P. vivax and P. falciparum.

A key difference between the two parasites is that P. vivax lies dormant in the liver before reactivating, leading to a resurgence of symptoms. Conventional malaria diagnostics do not detect this dormant form, which also serves as a reservoir of parasites in the population, contributing to ongoing disease transmission. 

P. vivax infections can be treated with primaquine. However, primaquine cannot be easily used in population-wide campaigns, because it is harmful to people with an enzymatic deficiency known as G6PD, which is relatively common in sub-Saharan Africa. 

The project

The PvSeroRDT project is assessing whether a newly developed rapid diagnostic test for P. vivax, which can detect dormant liver forms of the parasite, could be used in a test-and-treat strategy targeting entire communities.

Very few P. vivax parasites survive in the liver (potentially fewer than 10), so direct detection is challenging. Instead, the PvSeroRDT test detects antibodies to key P. vivax proteins that persist for several months after infection, covering the period when the parasite lies dormant in the liver. The plan is to use this diagnostic, along with a G6PD test, as part of a community-wide test-and-treat strategy (PvSeroTAT) to identify and treat asymptomatic cases of vivax malaria, thereby preventing relapses and reducing disease transmission.

The PvSeroRDT test is a lateral flow test type assay with a reader for interpretation of results, which should be available within 30 minutes. It has been shown to perform well in the laboratory but needs to be tested in the field. It is being evaluated further using stored blood samples and in field trials at sites in Ethiopia, Madagascar and Senegal. 

The device is being prototyped in the UK, with final production planned to be transferred to a diagnostics manufacturer based in Senegal. The PvSeroRDT project will include studies to investigate the acceptability and usability of the device, to inform final designs and implementation strategies. National policymakers are being engaged to draw up a roadmap for policy change and implementation. The project is also analysing costs and exploring what product attributes are most important and what policymakers would be willing to pay for different features.

Impact

The PvSeroRDT project is addressing a key challenge on the pathway to malaria elimination. It will:

• Reveal whether the PvSeroRDT test works well in the field and can be used to identify infected but asymptomatic individuals for treatment.
• Identify a pathway to regulatory and policy approvals to facilitate its uptake by countries.
• Provide a boost to the diagnostic manufacturing sector in Africa, with projected demand of up to a million tests a year.

The PvSeroRDT project could usher in a new approach to vivax malaria control. Modelling suggests a successful deployment could reduce the prevalence of P. vivax by 60–80%. This would deliver significant public health benefits, particularly in areas where P. vivax is most common and P. falciparum is becoming better controlled.