Microgeographical Differences of Plasmodium vivax Relapse and Re-Infection in the Peruvian Amazon

Abstract

Abstract. To determine the magnitude of Plasmodium vivax relapsing malaria in rural Amazonia, we carried out a study in four sites in northeastern Peru. Polymerase chain reaction-restriction fragment length polymorphism of PvMSP3a and tandem repeat (TR) markers were compared for their ability to distinguish relapse versus reinfection. Of 1,507 subjects with P. vivax malaria, 354 developed 1 episode during the study; 97 of 354 (27.5%) were defined as relapse using Pvmsp-3a alone. The addition of TR polymorphism analysis significantly reduced the number of definitively defined relapses to 26 of 354 (7.4%) (P 0.05). Multivariate logistic regression modeling showed that the probability of having 1 infection was associated with the following: subjects in Mazan (odds ratio [OR] = 2.56; 95% confidence interval [CI] 1.87, 3.51), 15-44 years of age (OR = 1.49; 95% CI 1.03, 2.15), traveling for job purposes (OR = 1.45; 95%CI 1.03, 2.06), and travel within past month (OR = 1.46; 95% CI 1.0, 2.14). The high discriminatory capacity of the molecular tools shown here is useful for understanding the micro-geography of malaria transmission.

Epidemiology of Plasmodium vivax Malaria in Peru

“…Subjects in these clinical trials were tested for glucose-6-phosphate dehydrogenase deficiency, but clinically significant low levels that would limit the use of 8-aminoquinolines were not found among more than 300 subjects. The increasing focal distribution of malaria transmission,5,6 the logistical difficulties in accessing remote riverine populations,5 the specific limitations for the control of P. vivax infections,15 together with the fact that a large proportion of those infections are asymptomatic and not detected by standard diagnostic methods such as light microscopy (LM),5,6,16,17 pose major challenges to the Peruvian national malaria control program (NMCP).…”

“…Despite the increasing research conducted in Peru over the past decade on P. vivax malaria epidemiology,17–21 diagnostics,22,23 treatment,12,13,24 vector biology,25–28 and molecular genetics,29–31 several knowledge gaps still need to be addressed to support the Peruvian NMCP, so that malaria transmission hotspots can be readily identified and that the NMCP can more effectively implement strategies that target such areas with effective interventions 32. In this review, the trends in P. vivax incidence are described in relation to major control efforts implemented in Peru over the past 70 years.…”

Genome-Scale Protein Microarray Comparison of Human Antibody Responses in Plasmodium vivax Relapse and Reinfection

“…Reinfection was defined as different genotypes present in primary versus subsequent infection parasites by PvMSP3α PCR-RFLP patterns. 28,29,32,33 Protein microarray analysis using a P. vivax asexual bloodstage proteome array. A proteome array was designed containing 2,233 P. vivax recombinant proteins, representing 1,936 predicted P. vivax asexual blood-stage proteins and comprised as recently described.…”

“…More generally, we intended to systematically and comprehensively identify P. vivax antigens of potential use for seroepidemiological studies and possibly for identifying vaccine candidates. 28). Considering the region's geographical isolation from the rest of Peru, health services within the surrounding areas of Iquitos are relatively good and accessible.…”

“…[25][26][27] With the validation of molecular tools to distinguish P. vivax relapses and reinfections that are common in our Amazonian village study population, 28,29 we compared the level of IgG responses between consecutive episodes of symptomatic P. vivax malaria, in particular, to determine whether naturally acquired antibody responses were boosted by subsequent infection. More generally, we intended to systematically and comprehensively identify P. vivax antigens of potential use for seroepidemiological studies and possibly for identifying vaccine candidates.…”