Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya
Molecular surveillance of drug resistance markers through time provides crucial information on genomic adaptations, especially in parasite populations exposed to changing drug pressures. To assess temporal trends of established genotypes associated with tolerance to clinically important antimalarial...
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| Format: | Article |
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Elsevier
2014-12-01
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| Series: | International Journal for Parasitology: Drugs and Drug Resistance |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2211320714000165 |
| _version_ | 1828291417109168128 |
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| author | John Okombo Alice W. Kamau Kevin Marsh Colin J. Sutherland Lynette Isabella Ochola-Oyier |
| author_facet | John Okombo Alice W. Kamau Kevin Marsh Colin J. Sutherland Lynette Isabella Ochola-Oyier |
| author_sort | John Okombo |
| collection | DOAJ |
| description | Molecular surveillance of drug resistance markers through time provides crucial information on genomic adaptations, especially in parasite populations exposed to changing drug pressures. To assess temporal trends of established genotypes associated with tolerance to clinically important antimalarials used in Kenya over the last two decades, we sequenced a region of the pfcrt locus encompassing codons 72–76 of the Plasmodium falciparum chloroquine resistance transporter, full-length pfmdr1 – encoding multi-drug resistance protein, P-glycoprotein homolog (Pgh1) and pfdhfr encoding dihydrofolate reductase, in 485 archived Plasmodium falciparum positive blood samples collected in coastal Kenya at four different time points between 1995 and 2013. Microsatellite loci were also analyzed to compare the genetic backgrounds of parasite populations circulating before and after the withdrawal of chloroquine and sulfadoxine/pyrimethamine. Our results reveal a significant increase in the prevalence of the pfcrt K76 wild-type allele between 1995 and 2013 from 38% to 81.7% (p < 0.0001). In contrast, we noted a significant decline in wild-type pfdhfr S108 allele (p < 0.0001) culminating in complete absence of this allele in 2013. We also observed a significant increase in the prevalence of the wild-type pfmdr1 N86/Y184/D1246 haplotype from 14.6% in 1995 to 66.0% in 2013 (p < 0.0001) and a corresponding decline of the mutant pfmdr1 86Y/184Y/1246Y allele from 36.4% to 0% in 19 years (p < 0.0001). We also show extensive genetic heterogeneity among the chloroquine-sensitive parasites before and after the withdrawal of the drug in contrast to a selective sweep around the triple mutant pfdhfr allele, leading to a mono-allelic population at this locus. These findings highlight the importance of continual surveillance and characterization of parasite genotypes as indicators of the therapeutic efficacy of antimalarials, particularly in the context of changes in malaria treatment policy. |
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| format | Article |
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| institution | Directory Open Access Journal |
| issn | 2211-3207 |
| language | English |
| last_indexed | 2024-04-13T10:51:22Z |
| publishDate | 2014-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal for Parasitology: Drugs and Drug Resistance |
| spelling | doaj.art-8cdb7c60ed0440a494686bab656f03bd2022-12-22T02:49:38ZengElsevierInternational Journal for Parasitology: Drugs and Drug Resistance2211-32072014-12-014315216310.1016/j.ijpddr.2014.07.003Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal KenyaJohn Okombo0Alice W. Kamau1Kevin Marsh2Colin J. Sutherland3Lynette Isabella Ochola-Oyier4Kenya Medical Research Institute (KEMRI)/Wellcome Trust Collaborative Research Program, P.O. Box 230-80108, Kilifi, KenyaKenya Medical Research Institute (KEMRI)/Wellcome Trust Collaborative Research Program, P.O. Box 230-80108, Kilifi, KenyaKenya Medical Research Institute (KEMRI)/Wellcome Trust Collaborative Research Program, P.O. Box 230-80108, Kilifi, KenyaDepartment of Immunology & Infection, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UKKenya Medical Research Institute (KEMRI)/Wellcome Trust Collaborative Research Program, P.O. Box 230-80108, Kilifi, KenyaMolecular surveillance of drug resistance markers through time provides crucial information on genomic adaptations, especially in parasite populations exposed to changing drug pressures. To assess temporal trends of established genotypes associated with tolerance to clinically important antimalarials used in Kenya over the last two decades, we sequenced a region of the pfcrt locus encompassing codons 72–76 of the Plasmodium falciparum chloroquine resistance transporter, full-length pfmdr1 – encoding multi-drug resistance protein, P-glycoprotein homolog (Pgh1) and pfdhfr encoding dihydrofolate reductase, in 485 archived Plasmodium falciparum positive blood samples collected in coastal Kenya at four different time points between 1995 and 2013. Microsatellite loci were also analyzed to compare the genetic backgrounds of parasite populations circulating before and after the withdrawal of chloroquine and sulfadoxine/pyrimethamine. Our results reveal a significant increase in the prevalence of the pfcrt K76 wild-type allele between 1995 and 2013 from 38% to 81.7% (p < 0.0001). In contrast, we noted a significant decline in wild-type pfdhfr S108 allele (p < 0.0001) culminating in complete absence of this allele in 2013. We also observed a significant increase in the prevalence of the wild-type pfmdr1 N86/Y184/D1246 haplotype from 14.6% in 1995 to 66.0% in 2013 (p < 0.0001) and a corresponding decline of the mutant pfmdr1 86Y/184Y/1246Y allele from 36.4% to 0% in 19 years (p < 0.0001). We also show extensive genetic heterogeneity among the chloroquine-sensitive parasites before and after the withdrawal of the drug in contrast to a selective sweep around the triple mutant pfdhfr allele, leading to a mono-allelic population at this locus. These findings highlight the importance of continual surveillance and characterization of parasite genotypes as indicators of the therapeutic efficacy of antimalarials, particularly in the context of changes in malaria treatment policy.http://www.sciencedirect.com/science/article/pii/S2211320714000165Antimalarial policyDrug resistanceMicrosatellitespfcrtpfmdr1pfdhfr |
| spellingShingle | John Okombo Alice W. Kamau Kevin Marsh Colin J. Sutherland Lynette Isabella Ochola-Oyier Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya International Journal for Parasitology: Drugs and Drug Resistance Antimalarial policy Drug resistance Microsatellites pfcrt pfmdr1 pfdhfr |
| title | Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya |
| title_full | Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya |
| title_fullStr | Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya |
| title_full_unstemmed | Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya |
| title_short | Temporal trends in prevalence of Plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal Kenya |
| title_sort | temporal trends in prevalence of plasmodium falciparum drug resistance alleles over two decades of changing antimalarial policy in coastal kenya |
| topic | Antimalarial policy Drug resistance Microsatellites pfcrt pfmdr1 pfdhfr |
| url | http://www.sciencedirect.com/science/article/pii/S2211320714000165 |
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