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

Abstract

To monitor drug resistance in Plasmodium vivax, a multidrug resistance 1 (Pvmdr1) gene and a putative transporter protein (Pvcrt-o) gene were used as molecular markers for chloroquine resistance. The biomarkers, the dihydrofolate reductase (Pvdhfr) gene and the dihydropteroate synthetase (Pvdhps) gene, were also used for the detection of resistance to sulphadoxine-pyrimethamine (SP); this drug is often accidentally used to treat P. vivax infections. Clinical blood samples (n = 120) were collected from patients who had been to one of eight malaria-endemic countries and diagnosed with P. vivax infection. The chloroquine resistance marker, the Pvmdr1 gene, showed F976:L1076 mutations and L1076 mutation. A K10 insertion in the Pvcrt-o gene was also found among the samples successfully sequenced. A combination of L/I57:R58:M61:T117 mutations in the Pvdhfr gene and G383:G553 mutations in the Pvdhps gene were also observed. Mutations found in these genes indicate that drug resistance is present in these eight countries. Whether or not countries are using chloroquine to treat P. vivax, there appears to be an increase in mutation numbers in resistance gene markers. The detected changes in mutation rates of these genes do suggest that there is still a trend towards increasing P. vivax resistance to chloroquine. The presence of the mutations associated with SP resistance indicates that P. vivax has had exposure to SP and this may be a consequence of either misdiagnosis or coinfections with P. falciparum in the past.

Genetic polymorphisms in genes associated with drug resistance in Plasmodium vivax parasites from northeastern Myanmar

“…Interestingly, the K10 insertion is rarely observed in Thailand, the border region between Thailand and Myanmar, and the border region between Thailand and Cambodia [ 44 , 52 ]. Other studies have reported no association between the K10 insertion and in vitro or ex vivo P. vivax CQ resistance [ 22 , 53 , 54 ]. Given the geographical genetic differences among parasite populations, the prevalence of the Pvcrt-o K10 insertion shows significant temporal and spatial heterogeneity [ 55 ] and the discrepancy may have resulted from differences in geography, population movement or sample size issues.…”

“…Sequence polymorphism is relatively limited in the Pvcrt-o locus but a lysine (AAG) insertion at amino acid position 10 (K10), which was initially discovered in Southeast Asian strains, has been suggested to be associated with CQ resistance [ 21 ]. Since then, this polymorphism has been observed in both Southeast Asian and South American parasites [ 17 , 22 , 23 ]. The Pvmdr1 gene encodes a transmembrane protein of the parasite’s digestive vacuole with 12 transmembrane domains and 1464 amino acids, and was characterized in 2005 [ 24 ].…”

The molecular basis of antimalarial drug resistance in Plasmodium vivax

“…Unlike pfcrt , and in contrast to pvmdr 1, very few SNPs (~10) in pvcrt have been reported, however, most occur at very low frequency ( Barnadas et al, 2008 ; Joy et al, 2018 ; Noisang et al, 2020 ). The most common PvCRT polymorphism is a lysine insertion at position 10 (K10) ( Barnadas et al, 2008 ; Joy et al, 2018 ; Noisang et al, 2020 ; Silva et al, 2018a ). The K10 insertion has been observed in both Southeast Asian and South American parasites ( Noisang et al, 2020 ; Silva et al, 2018b .…”

“…The most common PvCRT polymorphism is a lysine insertion at position 10 (K10) ( Barnadas et al, 2008 ; Joy et al, 2018 ; Noisang et al, 2020 ; Silva et al, 2018a ). The K10 insertion has been observed in both Southeast Asian and South American parasites ( Noisang et al, 2020 ; Silva et al, 2018b . ; Zhao et al, 2020 ).…”

An update on prevention of malaria in travelers

“… 82 The cause of resistance in P. vivax remains elusive due to the nature of the parasite’s dormant phase in the liver, low parasitemia, and difficulty in distinguishing relapse, recrudescence, and reinfection. 83 …”