Parasite of the Month: Plasmodium vivax

Abstract

Plasmodium vivax is a eukaryotic human pathogen and the most frequent and widely distributed cause of the recurring disease malaria. P. vivax is one of five species of malaria parasites that commonly infect humans. Although less virulent than Plasmodium falciparum, P. vivax malaria infections can lead to severe disease and death. The disease is transmitted to humans by female anopheline mosquitoes during acquisition of a blood meal. An obligate liver stage of development precedes blood stage replication which accounts for all disease-associated morbidity and mortality and chloroquine is still used to treat the disease. Approximately 2.5 billion people are at risk of infection with P. vivax, and it is found mainly in Asia and Latin America where it accounts for 65% of malaria cases. In Africa, the widespread lack of the Duffy antigen in the population has constrained transmission. A dormant liver stage form, known as the hypnozoite can reactivate and causes disease relapses and the majority of blood stage infections are caused by relapse. The hypnozoite is thus a challenge for malaria eradication campaigns and primaquine and tafenoquine are the only drugs known to target the hypnozoite. However, these therapies are inadequate since primaquine cannot be administered to pregnant women and people with commonly occurring glucose-6-phosphate dehydrogenase deficiency and tafenoquine cannot be administered to children. There is no effective P. vivax vaccine