The human malaria parasite Plasmodium vivax imposes unique challenges to its control and elimination. Primary among those is the hypnozoite reservoir of infection in endemic communities. It is the dominant source of incident malaria and exceedingly difficult to attack due to both inability to diagnose latent carriers and the potentially life-threatening toxicity of primaquine in patients with an inborn deficiency of G6PD, the only therapeutic option against hypnozoites. Large segments of endemic populations are not eligible for primaquine, and alternative strategies for managing the threat of relapse in any group have not been optimized or validated. Association of risk of primaquine failure against latent P. vivax with impaired alleles of P450 2D6 exacerbates the substantial pool of primaquine ineligibles. Resistance to chloroquine against acute P. vivax malaria commonly occurs; alternative therapies like ACTs are effective but seldom evaluated as a partner drug to primaquine in the essential radical cure. Many of the Anopheles mosquito vector of P. vivax in South and Southeast Asia, where >90% of infections occur, thrive in a diversity of habitats and exhibit wide ranges of feeding and breeding behavior. This chapter explores many of these challenges and possible approaches in controlling and eliminating endemic vivax malaria.
Part of the book: Towards Malaria Elimination
Resistance to antimalarial drugs is a threat to global efforts to eliminate malaria by 2030. Currently, treatment for vivax malaria uses chloroquine or ACT for uncomplicated P. vivax whereas primaquine is given to eliminate latent liver stage infections (a method known as radical cure). Studies on P. vivax resistance to antimalarials and the molecular basis of resistance lags far behind the P. falciparum as in vitro cultivation of the P. vivax has not yet been established. Therefore, data on the P. vivax resistance to any antimalarial drugs are generated through in vivo studies or through monitoring of antimalarial treatments in mixed species infection. Indirect evidence through drug selective pressure on the parasites genome, as evidenced by the presence of the molecular marker(s) for drug resistance in areas where P. falciparum and P. vivax are distributed in sympatry may reflect, although require validation, the status of P. vivax resistance. This review focuses on the currently available data that may represent the state-of-the art of the P. vivax resistance status to antimalarial to anticipate the challenge for malaria elimination by 2030.
Part of the book: Plasmodium Species and Drug Resistance