A rapid immunochromatographic test for antibody detection as a new tool for monitoring malaria caused by Plasmodium vivax.

Eliminating malaria caused by Plasmodium vivax remains a challenge, especially in areas of low transmission, where the high proportion of asymptomatic and subpatent infections limits the effectiveness of national eradication program control strategies. Antibody levels against parasite's antigens wane several months after treatment. Since the acquisition and maintenance of antimalarial humoral immunity depends on the infection, antibodies can serve as biomarkers of parasite exposure, emerging as a promising alternative for monitoring recent exposure to the parasite. We developed and validated a rapid diagnostic test that detects IgG (Ab-RDT) against two blood-stage antigens of P. vivax. The Ab-RDT identified a gradual decrease in antibody levels in treated individuals, suggesting that a positive test reflects recent exposure to the parasite or maintenance of infection. In agreement, a longitudinal study showed that a positive test, on Ab-RDT or ELISA, was strongly associated with the risk of subsequent detection of parasitemia by qPCR, highlighting the tests' usefulness in identifying individuals who were recently exposed or are more likely to be infected. The field performance of the Ab-RDT was 80.1% sensitivity and 89.4% specificity, using ELISA as a reference method, reinforcing the potential of antibody detection as a valuable tool to support malaria surveillance for P. vivax, especially for monitoring transmission in regions moving towards eradication, thereby enabling more strategic efforts in malaria control.