Assessment of drug resistance associated genetic diversity in Mauritanian isolates of Plasmodium vivax reveals limited polymorphism

Abstract

BackgroundPlasmodium vivax is the predominant malaria species in northern Mauritania. Molecular data on P. vivax isolates circulating in West Africa are scarce. The present study analysed molecular markers associated with resistance to antifolates (Pvdhfr and Pvdhps), chloroquine (Pvmdr1), and artemisinin (Pvk12) in P. vivax isolates collected in two cities located in the Saharan zone of Mauritania.MethodsBlood samples were obtained from P. vivax-infected patients recruited for chloroquine therapeutic efficacy study in 2013 and febrile patients spontaneously consulting health facilities in Nouakchott and Atar in 2015–2016. Fragments of Pvdhfr (codons 13, 33, 57, 58, 61, 117, and 174), Pvdhps (codons 382, 383, 512, 553, and 585), Pvmdr1 (codons 976 and 1076) and Pvk12 (codon 552) genes were amplified by PCR and sequenced.ResultsMost of the isolates in Nouakchott (126/154, 81.8%) and Atar (44/45, 97.8%) carried the wild-type Pvdhfr allelic variant (IPFSTSI). In Nouakchott, all mutants (28/154; 18.2%) had double Pvdhfr mutations in positions 58 and 61 (allelic variant IPFRMSI), whereas in Atar only 1 isolate was mutant (S117N, allelic variant IPFSTNI). The wild-type Pvdhps allelic variant (SAKAV) was found in all tested isolates (Nouakchott, n = 93; Atar, n = 37). Few isolates in Nouakchott (5/115, 4.3%) and Atar (3/79, 3.8%) had the mutant Pvmdr1 allele 976F or 1076L, but not both, including in pre-treatment isolates obtained from patients treated successfully with chloroquine. All isolates (59 in Nouakchott and 48 in Atar) carried the wild-type V552 allele in Pvk12.ConclusionsPolymorphisms in Pvdhfr, Pvdhps, Pvmdr1, and Pvk12 were limited in P. vivax isolates collected recently in Nouakchott and Atar. Compared to the isolates collected in Nouakchott in 2007–2009, there was no evidence for selection of mutants. The presence of one, but not both, of the two potential markers of chloroquine resistance in Pvmdr1 in pre-treatment isolates did not influence the clinical outcome, putting into question the role of Pvmdr1 mutant alleles 976F and 1076L in treatment failure. Molecular surveillance is an important component of P. vivax malaria control programme in the Saharan zone of Mauritania to predict possible emergence of drug-resistant parasites.

Multi-locus genotyping reveals established endemicity of a geographically distinctPlasmodium vivaxpopulation in Mauritania, West Africa

“…However, the same studies reported between 10 and 20% of infections to have double mutant alleles of dhfr (combinations of variants at codons 58, 61 and 117) [38, 39], in contrast to results here that showed an absence of resistance-associated alleles at these codons (except for a single variant at codon 117 in infection sample NKT136 that had an overall genotype similar to Asian parasites). Antimalarial antifolate use in Mauritania is now limited to intermittent preventative treatment of pregnant women with sulphadoxine-pyrimethamine [38], although antifolates were previously used for therapy along with chloroquine. Comparing this and previous studies, the frequency of the mdr1 976F allele in Mauritania varied from 28% in 2007-9 to 14% in 2012-13, and 4% in 2013-16 [38, 39], which may reflect a decline due to fitness cost after chloroquine use officially stopped following introduction of Artemisinin Combination Therapy in 2006, although the allele is not a marker of chloroquine resistance and is at most a minor modulator [16].…”

“…Analysis of dhfr and dhps genotypes revealed a virtual absence of antifolate resistance-associated variants in P. vivax in Mauritania. Consistent with this, drug resistance genotyping of P. vivax samples previously taken from Nouakchott in 2007-9 and 2013-16 also showed no resistance-associated alleles in dhps [38, 39]. However, the same studies reported between 10 and 20% of infections to have double mutant alleles of dhfr (combinations of variants at codons 58, 61 and 117) [38, 39], in contrast to results here that showed an absence of resistance-associated alleles at these codons (except for a single variant at codon 117 in infection sample NKT136 that had an overall genotype similar to Asian parasites).…”

“…Consistent with this, drug resistance genotyping of P. vivax samples previously taken from Nouakchott in 2007-9 and 2013-16 also showed no resistance-associated alleles in dhps [38, 39]. However, the same studies reported between 10 and 20% of infections to have double mutant alleles of dhfr (combinations of variants at codons 58, 61 and 117) [38, 39], in contrast to results here that showed an absence of resistance-associated alleles at these codons (except for a single variant at codon 117 in infection sample NKT136 that had an overall genotype similar to Asian parasites). Antimalarial antifolate use in Mauritania is now limited to intermittent preventative treatment of pregnant women with sulphadoxine-pyrimethamine [38], although antifolates were previously used for therapy along with chloroquine.…”

“…Antimalarial antifolate use in Mauritania is now limited to intermittent preventative treatment of pregnant women with sulphadoxine-pyrimethamine [38], although antifolates were previously used for therapy along with chloroquine. Comparing this and previous studies, the frequency of the mdr1 976F allele in Mauritania varied from 28% in 2007-9 to 14% in 2012-13, and 4% in 2013-16 [38, 39], which may reflect a decline due to fitness cost after chloroquine use officially stopped following introduction of Artemisinin Combination Therapy in 2006, although the allele is not a marker of chloroquine resistance and is at most a minor modulator [16]. Clinical evidence indicates that most local P. vivax infections are sensitive to chloroquine treatment [40].…”

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“…Consistent with this, drug resistance genotyping of P. vivax samples previously taken from Nouakchott in 2007-9 and 2013-16 also showed no resistance-associated alleles in dhps [41,42]. However, the same studies reported between 10 and 20% of infections to have double mutant alleles of dhfr (combinations of variants at codons 58, 61 and 117) [41,42], in contrast to results here that showed an absence of resistance-associated alleles at these codons (except for a single variant at codon 117 in infection sample NKT136 that had an overall genotype similar to Asian parasites). Antimalarial antifolate use in Mauritania is now limited to intermittent preventative treatment of pregnant women with sulphadoxine-pyrimethamine [41], although antifolates were previously used for therapy along with PLOS NEGLECTED TROPICAL DISEASES chloroquine.…”