Abstract
BackgroundPeru is one of the Latin American countries with the highest malaria burden, mainly due to Plasmodium vivax infections. However, little is known about P. vivax transmission dynamics in the Peruvian Amazon, where most malaria cases occur. The genetic diversity and population structure of P. vivax isolates collected in different communities around Iquitos city, the capital of the Peruvian Amazon, was determined.MethodsPlasmodium vivax population structure was determined by multilocus genotyping with 16 microsatellites on 159 P. vivax infected blood samples (mono-infections) collected in four sites around Iquitos city. The population characteristics were assessed only in samples with monoclonal infections (n = 94), and the genetic diversity was determined by calculating the expected heterozygosity and allelic richness. Both linkage disequilibrium and the genetic differentiation (θ) were estimated.ResultsThe proportion of polyclonal infections varied substantially by site (11% - 70%), with the expected heterozygosity ranging between 0.44 and 0.69; no haplotypes were shared between the different populations. Linkage disequilibrium was present in all populations (IAS 0.14 - 0.61) but was higher in those with fewer polyclonal infections, suggesting inbreeding and a clonal population structure. Strong population differentiation (θ = 0.45) was found and the Bayesian inference cluster analysis identified six clusters based on distinctive allele frequencies.ConclusionThe P. vivax populations circulating in the Peruvian Amazon basin are genetically diverse, strongly differentiated and they have a low effective recombination rate. These results are in line with the low and clustered pattern of malaria transmission observed in the region around Iquitos city.
Highlights
Peru is one of the Latin American countries with the highest malaria burden, mainly due to Plasmodium vivax infections
Parasite population structure can be analysed by microsatellites, simple sequence tandem repeats often used for studying the genetic diversity and population dynamics, such as those used in Brazil and Colombia where high heterogeneity and strong population structure was found [9,10,11]
The P. vivax population in Iquitos and neighbouring areas is diverse and highly structured, with strong genetic differentiation between geographically isolated sites, suggesting that transmission is extremely local and confined within each cluster [3,4]. These findings were comparable to those reported from Brazil where the P. vivax and P. falciparum parasite populations were spatially and temporally clustered [9,10,35,36,37]
Summary
Peru is one of the Latin American countries with the highest malaria burden, mainly due to Plasmodium vivax infections. Little is known about P. vivax transmission dynamics in the Peruvian Amazon, where most malaria cases occur. The genetic diversity and population structure of P. vivax isolates collected in different communities around Iquitos city, the capital of the Peruvian Amazon, was determined. Analysing the genetic diversity and the structure of the local parasite population in time and space provide new insights on the local distribution and dynamics of P. vivax transmission [7,8]. In settings like the Peruvian Amazon basin, where the malaria distribution is uneven and clustered [3,4,12,13], the P. vivax parasite population showed high diversity when genotyped using the Merozoite surface protein 3 alpha (MSP3α) marker alone [14]. The population structure of a set of P. vivax infected blood samples, collected around Iquitos city, the capital of Loreto Department, was analysed by multilocus genotyping
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