Plasmodium vivax represents a special challenge to
malaria control because of the ability of a single
infection to relapse over months to years. P. vivax is more tolerant of low temperatures than P. falciparum, which spreads its potential range far beyond the tropics into sub-Arctic areas. Ordinary
malaria control measures such as residual
insecticide spraying and impregnated bed nets are effective for P. vivax, but long-lasting (up to 3 years) residual hepatic parasites (hypnozoites) mean that even well-executed
malaria control programs must maintain maximal efforts for an extended period in order to eliminate indigenous
infections. Hypnozoites are only eliminated by using an
8-aminoquinoline (currently only
primaquine), which requires compliance with a long regimen as well as care to avoid those at risk of
haemolysis due to the common genetic polymorphism,
glucose-6-phosphate dehydrogenase deficiency. Risk of reintroduction of P. vivax into areas without
malaria but still containing competent Anopheles vectors is enhanced as persons carrying hypnozoites are undetectable until they become symptomatic from activation of the quiescent liver parasite.
Mass drug administration using
drug combinations including
primaquine have successfully eliminated
malaria from small islands demonstrating proof of principal as a potential elimination method. It will be very difficult to maintain adequate
malaria surveillance measures for years after
malaria has ceased to be a public health problem, which will clearly be required to eliminate relapsing
malaria such as P. vivax. New interventions will likely be required to eliminate
vivax malaria; highly desirable new products include transmission-blocking
vaccines, new
drug combinations to treat
chloroquine resistant strains and a safe, long-lasting
8-aminoquinoline.