Genetic Diversity of Plasmodium vivax Field Isolates from the Thai–Myanmar Border during the Period of 2006–2016

High levels of genetic variants of Plasmodium vivax have previously been reported in Thailand. Circumsporozoite surface protein (CSP), merozoite surface protein (MSP), and microsatellite markers were used to determine the genetic polymorphisms of P. vivax. This study aimed to investigate the molecular epidemiology of P. vivax populations at the Thai–Myanmar border by genotyping the PvCSP, PvMSP-3α, and PvMSP-3β genes. Four hundred and forty P. vivax clinical isolates were collected from the Mae Sot and Sai Yok districts from 2006–2007 and 2014–2016. Polymerase chain reaction with restriction fragment length polymorphism (RFLP) was used to investigate the genetic polymorphisms of the target genes. Based on PCR band size variations, 14 different PvCSP alleles were identified: eight for VK210 and six for VK247. The VK210 genotype was the dominant variant during both sample collection periods. Based on PCR genotyping, three distinct types (A, B, and C) for both PvMSP-3α and PvMSP-3β were observed. Following RFLP, 28 and 14 allelic variants of PvMSP-3α and 36 and 20 allelic variants of PvMSP-3β with varying frequencies were identified during the first and second periods, respectively. High genetic variants of PvMSP-3 and PvCSP were found in the study area. PvMSP-3β exhibited a higher level of genetic diversity and multiple-genotype infection versus PvMSP-3α.