vivax

Plasmodium vivax is a protozoan parasite and one of the species that cause human malaria. It is transmitted by Anopheles mosquitoes and is the primary cause of vivax malaria in many parts of Asia, the Americas, and parts of Europe. Compared with Plasmodium falciparum, P. vivax generally produces a slower, less lethal infection but can still cause significant illness and relapse due to dormant liver stages.

A defining feature of P. vivax is its ability to form hypnozoites, dormant parasites in liver cells that can reactivate weeks, months, or years after the initial infection. This relapsing biology complicates control and requires treatment targeting both blood-stage parasites and liver hypnozoites for a radical cure. P. vivax preferentially invades reticulocytes, or young red blood cells, which often results in lower levels of parasites in the blood but can still cause anemia and splenomegaly.

Clinical presentation typically includes fever, chills, and malaise, with temperature spikes often occurring every 48 hours (tertian malaria). Diagnosis relies on microscopic examination of thick and thin blood smears or rapid diagnostic tests that detect parasite antigens. Confirmation is followed by treatment tailored to local drug resistance patterns.

Treatment generally combines a blood-stage antimalarial (such as chloroquine in susceptible regions or artemisinin-based combination therapies in drug-resistant areas) with primaquine or, in some cases, other hypnozoite-targeting drugs to eradicate liver-stage parasites. Before primaquine or related drugs are given, patients should be tested for G6PD deficiency due to risk of hemolysis.

Epidemiologically, P. vivax remains a major malaria burden in many regions, though its prevalence varies with geography and local resistance. The term vivax derives from Latin for “lively” or “vigorous.”