Geographical variation in Plasmodium vivax relapse

Abstract

BackgroundPlasmodium vivax has the widest geographic distribution of the human malaria parasites and nearly 2.5 billion people live at risk of infection. The control of P. vivax in individuals and populations is complicated by its ability to relapse weeks to months after initial infection. Strains of P. vivax from different geographical areas are thought to exhibit varied relapse timings. In tropical regions strains relapse quickly (three to six weeks), whereas those in temperate regions do so more slowly (six to twelve months), but no comprehensive assessment of evidence has been conducted. Here observed patterns of relapse periodicity are used to generate predictions of relapse incidence within geographic regions representative of varying parasite transmission.MethodsA global review of reports of P. vivax relapse in patients not treated with a radical cure was conducted. Records of time to first P. vivax relapse were positioned by geographic origin relative to expert opinion regions of relapse behaviour and epidemiological zones. Mixed-effects meta-analysis was conducted to determine which geographic classification best described the data, such that a description of the pattern of relapse periodicity within each region could be described. Model outputs of incidence and mean time to relapse were mapped to illustrate the global variation in relapse.ResultsDifferences in relapse periodicity were best described by a historical geographic classification system used to describe malaria transmission zones based on areas sharing zoological and ecological features. Maps of incidence and time to relapse showed high relapse frequency to be predominant in tropical regions and prolonged relapse in temperate areas.ConclusionsThe results indicate that relapse periodicity varies systematically by geographic region and are categorized by nine global regions characterized by similar malaria transmission dynamics. This indicates that relapse may be an adaptation evolved to exploit seasonal changes in vector survival and therefore optimize transmission. Geographic patterns in P. vivax relapse are important to clinicians treating individual infections, epidemiologists trying to infer P. vivax burden, and public health officials trying to control and eliminate the disease in human populations.

Prospective Study of Plasmodium vivax Malaria Recurrence after Radical Treatment with a Chloroquine-Primaquine Standard Regimen in Turbo, Colombia

“…In the Americas, more than 60% of the annual cases of malaria are caused by P. vivax (2). This parasite has a dormant stage known as hypnozoite, in which it remains in the liver for an indeterminate length of time (3). Hypnozoites might be activated months after a previous episode that has been treated and cured, causing relapses (3).…”

Relapse of a Plasmodium vivax Infection in an Iranian Patient: A Case Report

“…There are some reports of P. vivax relapses in the world with using an inadequate dosage of primaquine (7,9). It has been noted that there are geographical variations in the emergence and periodicity of P. vivax relapses from 3 weeks to 3 years following the initial infection (2,14). Despite tropical strains of P. vivax that are described with short latency, the strains in temperate and subtropical areas have a tendency to illustrate a long latency (2, 7).…”

“…Primaquine, 8-aminoquinoline" has remained the only drug to resolve the latent phase of P. vivax in the liver (2,9,12). Primaquine can lead to deadly hemolysis in patients with glucose 6 phosphate dehydrogenase (G6PD) deficiency (2).…”

“…Malaria continues to be an important febrile infectious disease in some areas of the world (1,2). Out of 5 Plasmodium species that infect humans, Plasmodium vivax is the most prevalent in the malaria endemic regions of Iran (3).…”

Hemozoin as an immune stimulant of the mosquitoAnopheles gambiaeresponse against the malaria parasite

“…Of these, Plasmodium falciparum (P. falciparum) and P. vivax are the most prevalent forms. P. falciparum malaria is the most deadly of both and predominates in Africa (Guerra et al, 2008), while P. vivax has a wider distribution (Battle et al, 2014), partly due to its higher adaptability and also because it is able to undergo a dormant liver stage (the hypnozoite), enabling its longer survival.…”