The prevalence of molecular markers of drug resistance in Plasmodium vivax from the border regions of Thailand in 2008 and 2014

Abstract

The prevalence of Plasmodium vivax is increasing in the border regions of Thailand; one potential problem confounding the control of malaria in these regions is the emergence and spread of drug resistance. The aim of this study was to determine the genetic diversity in genes potentially linked to drug resistance in P. vivax parasites isolated from four different border regions of Thailand; Thai-Myanmar (Tak, Mae Hong Son and Prachuap Khiri Khan Provinces), and Thai-Cambodian borders (Chanthaburi Province). Isolates were collected from 345 P. vivax patients in 2008 and 2014, and parasite DNA extracted and subjected to nucleotide sequencing at five putative drug-resistance loci (Pvdhfr, Pvdhps, Pvmdr1, Pvcrt-o and Pvk12). The prevalence of mutations in Pvdhfr, Pvdhps and Pvmdr1 were markedly different between the Thai-Myanmar and Thai-Cambodian border areas and also varied between sampling times. All isolates carried the Pvdhfr (58R and 117N/T) mutation, however, whereas the quadruple mutant allele (I57R58M61T117) was the most prevalent (69.6%) in the Thai-Myanmar border region, the double mutant allele (F57R58T61N117) was at fixation on the Thai-Cambodian border (100%). The most prevalent genotypes of Pvdhps and Pvmdr1 were the double mutant (S382G383K512G553) (65.1%) and single mutant (M958Y976F1076) (46.5%) alleles, respectively on the Thai-Myanmar border while the single Pvdhps mutant (S382G383K512A553) (52.7%) and the triple Pvmdr1 mutant (M958F976L1076) (81%) alleles were dominant on the Thai-Cambodian border. No mutations were observed in the Pvcrt-o gene in either region. Novel mutations in the Pvk12 gene, the P. vivax orthologue of PfK13, linked to artemisinin resistance in Plasmodium falciparum, were observed with three nonsynonymous and three synonymous mutations in six isolates (3.3%).

Molecular Detection of Antimalarial Drug Resistance in Plasmodium vivax from Returned Travellers to NSW, Australia during 2008–2018

“…The increased rate of these mutations suggests that chloroquine resistance in P. vivax will become more common in the South Asia region where chloroquine has remained the first-line drug [39]. Our findings from clinical isolates from Southeast Asia were also similar to other studies in this location [5][6][7]16,40]. A clinical report of chloroquine-resistant P. vivax in a Thai pregnant woman indicated that recurrent parasites during Day 21 and 143 carried the double F976:L1076 mutation [40].…”

“…Tandem repeat variants found in the Pvdhfr gene locus have been described by different laboratories [26]; the typing of these variants in this study followed that of a recent Thai study from 2018 [7]. This group described three different tandem repeat variants found in the Pvdhfr gene sequence.…”

“…A clinical report of chloroquine-resistant P. vivax in a Thai pregnant woman indicated that recurrent parasites during Day 21 and 143 carried the double F976:L1076 mutation [40]. This double mutation was found in Thailand in 2008 (49.2%) and again in 2014 (18.4%) [7]. The same double mutations were found in 15.4% of samples in Myanmar between 2009 and 2016 [5].…”

“…Molecular markers of chloroquine resistance in P. vivax, Pvmdr1 and Pvcrt-o genes were used as they are orthologous to Pfmdr1 and Pfcrt genes, which are associated with chloroquine resistance in P. falciparum [6]. Among the studied samples herein, the presence of the F976 and L1076 mutations in the Pvmdr1 gene and the K10 insertion in the Pvcrt-o gene were shown previously to be related to chloroquine resistance in P. vivax by in vivo and in vitro studies [5,7,16,28,29].…”

“…A recurrent parasitemia with 100 ng/mL of the measured chloroquine concentration in whole blood on or before the 28th day of treatment is classified as resistant [3,6]. Chloroquine resistance in P. vivax was found around the late 1980s and resistance was first reported in Australian travellers, who were diagnosed with P. vivax infection after returning from Papua New Guinea (PNG) [7,8]. These travellers failed to clear the parasitemia by the standard chloroquine dose [3,6,9,10].…”