The Geographical Distribution of Allele Polymorphisms of Plasmodium vivax in Different Regions of Thailand
Varakorn Kosaisavee DrPH*,**, Ian Hastings PhD***, Alister Craig PhD***, Usa Lek-Uthai DrPH*
Affiliation : * Department of Parasitology and Entomology, Faculty of Public Health, Mahidol University, Bangkok, Thailand ** Doctor of Public Health Programme (Parasitology), Faculty of Graduate Studies, Mahidol University, Nakornpathom, Thailand *** Department of Molecular and Biochemical Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
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 (HE) formula, F-STAT and LIAN programs.
Result: There was considerable variation in the PvMSP1 gene within 2 fragments for which HE was 0.8303, whereas PvCSP
showed low HE 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 (IS
A) were non-significant. There was no evidence of LD within the P. vivax populations.
Conclusion : HE at each locus of the PvMSP1 gene showed significant differences in allele frequencies between sites.
Keywords : Plasmodium vivax, PvMSP1, PvCSP, Heterozygosity, Linkage disequilibrium
