Plasmodium falciparum phenotypic and genotypic resistance profile during the emergence of Piperaquine resistance in Northeastern Thailand

Abstract

Malaria remains a public health problem in Thailand, especially along its borders where highly mobile populations can contribute to persistent transmission. This study aimed to determine resistant genotypes and phenotypes of 112 Plasmodium falciparum isolates from patients along the Thai-Cambodia border during 2013–2015. The majority of parasites harbored a pfmdr1-Y184F mutation. A single pfmdr1 copy number had CVIET haplotype of amino acids 72–76 of pfcrt and no pfcytb mutations. All isolates had a single pfk13 point mutation (R539T, R539I, or C580Y), and increased % survival in the ring-stage survival assay (except for R539I). Multiple copies of pfpm2 and pfcrt-F145I were detected in 2014 (12.8%) and increased to 30.4% in 2015. Parasites containing either multiple pfpm2 copies with and without pfcrt-F145I or a single pfpm2 copy with pfcrt-F145I exhibited elevated IC90 values of piperaquine. Collectively, the emergence of these resistance patterns in Thailand near Cambodia border mirrored the reports of dihydroartemisinin-piperaquine treatment failures in the adjacent province of Cambodia, Oddar Meanchey, suggesting a migration of parasites across the border. As malaria elimination efforts ramp up in Southeast Asia, host nations militaries and other groups in border regions need to coordinate the proposed interventions.

Molecular surveillance of dihydroartemisinin-piperaquine resistance in northwestern Thailand

“…Ampli cation of plasmepsin-2 is widely used as a marker to trace PPQ resistance [9,[12][13][14][15]. Previous studies suggested that this genotype was restricted to eastern GMS [10,14,15]. Consistent with these reports, none of the P. falciparum isolates in Tak province from 2013-2019 had plasmepsin-2 ampli cation.…”

“…It has been shown that whereas C580Y was the main mutation in the eastern GMS, F446I was more common in Myanmar [10]. C580Y has now been found in many parts of Thailand but become near xation along the Cambodian border [4,10,15,26]. The distributions of other kelch13 alleles in the country vary geographically -with Y493H and R539T found mainly in the east, P574L in the west and R561H in northwest [26].…”

“…Although this mutation has not been formally associated with clinical resistance, parasites carrying this mutation were recently shown to have elevated ring-stage survival compared to the wild-type parasite [18]. Ampli cation of plasmepsin-2 is widely used as a marker to trace PPQ resistance [9,[12][13][14][15]. Previous studies suggested that this genotype was restricted to eastern GMS [10,14,15].…”

“…Ampli cation of P. falciparum plasmepsin-2 and 3 genes on chromosome 14 was found to associate with PPQ resistance in Cambodian isolates [9,12]. This marker has since been adopted as a molecular marker of PPQ resistance [13][14][15]. Recent studies also reported that mutations in P. falciparum chloroquine resistance transporter (Pfcrt) gene at nucleotide positions downstream of the 4-aminoquinoline resistance locus (amino acids 72-76) particularly at codons T93S, H97Y, F145I may also contribute to PPQ resistance [13,16,17].…”

Learnings from Thailand in building strong surveillance for malaria elimination

“…As part of routine malaria care, treated patients are tracked for up to 90 days to confirm parasite clearance and monitor antimalarial drug efficacy 8 . In 2019, after iDES results, triangulated with external findings, documented subpar piperaquine performance, the National Drug Policy Committee approved pyronaridine-artesunate as a new first-line treatment for two provinces 7 , 9 .…”