The geographical distribution of allele polymorphisms of Plasmodium vivax in different regions of Thailand

Abstract

Objective: To investigate the genetic structure of Plasmodium vivax circumsporozoite surface protein (PvCSP) and P. vivax merozoite surface protein 1 (PvMSP1) genes from field isolates of malaria parasites from four different regions of Thailand. Material and Method: The data was collected by cross-sectional survey, consisting of 273 P. vivax infected blood samples from malaria clinics in 4 different border regions of Thailand from February 2008 to February 2009. The dried blood spots were extracted for DNA and Plasmodium species confirmed by species-specific primer sets. PvCSP and PvMSP1 genes were amplified and their population genetics were analyzed by using the Heterozygosity (H E ) formula, F-STAT and LIAN programs. Result: There was considerable variation in the PvMSP1 gene within 2 fragments for which H E was 0.8303, whereas PvCSP showed low H E at 0.1418. Significant differences in allele frequencies between sites were quantified by Fst, Linkage disequilibrium (LD). The results showed PvMSP1 F2; Fst = 0.063, p = 0.07; PvMSP1 F2 RFLP pattern; Fst = 0.154, p = 0.005; PvMSP1 F3; Fst = 0.23, p = 0.005 and the overall loci showed Fst = 0.151, p = 0.005 (Fisher's exact test). All values of Index association (I S A ) were non-significant. There was no evidence of LD within the P. vivax populations. Conclusion: H E at each locus of the PvMSP1 gene showed significant differences in allele frequencies between sites.