In Vitro and Molecular Surveillance for Antimalarial Drug Resistance in Plasmodium falciparum Parasites in Western Kenya Reveals Sustained Artemisinin Sensitivity and Increased Chloroquine Sensitivity

Abstract

Malaria control is hindered by the evolution and spread of resistance to antimalarials, necessitating multiple changes to drug policies over time. A comprehensive antimalarial drug resistance surveillance program is vital for detecting the potential emergence of resistance to antimalarials, including current artemisinin-based combination therapies. An antimalarial drug resistance surveillance study involving 203 Plasmodium falciparum malaria-positive children was conducted in western Kenya between 2010 and 2013. Specimens from enrolled children were analyzed in vitro for sensitivity to chloroquine (CQ), amodiaquine (AQ), mefloquine (MQ), lumefantrine, and artemisinin derivatives (artesunate and dihydroartemisinin) and for drug resistance allele polymorphisms in P. falciparum crt (Pfcrt), Pfmdr-1, and the K13 propeller domain (K13). We observed a significant increase in the proportion of samples with the Pfcrt wild-type (CVMNK) genotype, from 61.2% in 2010 to 93.0% in 2013 (P < 0.0001), and higher proportions of parasites with elevated sensitivity to CQ in vitro. The majority of isolates harbored the wild-type N allele in Pfmdr-1 codon 86 (93.5%), with only 7 (3.50%) samples with the N86Y mutant allele (the mutant nucleotide is underlined). Likewise, most isolates harbored the wild-type Pfmdr-1 D1246 allele (79.8%), with only 12 (6.38%) specimens with the D1246Y mutant allele and 26 (13.8%) with mixed alleles. All the samples had a single copy of the Pfmdr-1 gene (mean of 0.907 ؎ 0.141 copies). None of the sequenced parasites had mutations in K13. Our results suggest that artemisinin is likely to remain highly efficacious and that CQ sensitivity appears to be on the rise in western Kenya.A ntimalarial drug resistance has hampered progress in malaria control and has led to several changes in drug policies over time. To minimize the potential emergence of drug resistance, the World Health Organization (WHO) recommends the use of artemisinin-based combination therapy (ACT), which consists of an artemisinin derivative coformulated with another class of antimalarial (1). In Kenya, the use of chloroquine (CQ) as the first line of malaria treatment was discontinued in the late 1990s due to a high percentage of treatment failures. CQ was replaced by sulfadoxinepyrimethamine (SP) as the first line of treatment, with amodiaquine (AQ) as a second choice. However, the use of SP was shortlived, as the majority of circulating parasites rapidly developed resistance to SP (reviewed in reference 2). Therefore, in April 2004, the ACT artemether-lumefantrine (AL; Coartem) was recommended as the first-line therapy for the treatment of uncomplicated Plasmodium falciparum malaria in Kenya, although this was not fully implemented until late 2006, when the country was finally able to undertake delivery of large quantities of the drug. Thus, between 2004 and 2006, AQ was briefly used as the first-line treatment for malaria in Kenya. Dihydroartemisinin-piperaquine (DHAP) is the current second-line antimalarial drug treatment, while artesu...

Recovery and stable persistence of chloroquine sensitivity in Plasmodium falciparum parasites after its discontinued use in Northern Uganda.

“…However, with widespread discontinued use, numerous molecular-epidemiological studies showed that there was return of chloroquine susceptibility in P. falciparum field isolates [4]. This is supported by ex vivo [5][6][7][8][9][10][11][12][13][14][15][16] and in vivo drug-susceptibility studies [5,17,18]. Findings suggest that chloroquine might be reused in the future as an option for the treatment and/or chemoprophylaxis on the condition that chloroquine sensitivity is maintained in the area.…”

“…Findings suggest that chloroquine might be reused in the future as an option for the treatment and/or chemoprophylaxis on the condition that chloroquine sensitivity is maintained in the area. As the parasite is "skilled" in evading antimalarial treatments, continuous surveillance on longitudinal persistence of chloroquine susceptibility by molecular and phenotypic analysis [8,16,18,19] is needed.…”

Recovery and stable persistence of chloroquine sensitivity in Plasmodium falciparum parasites after its discontinued use in Northern Uganda

“…However, with widespread discontinued use, numerous molecular-epidemiological studies showed that there was return of chloroquine susceptibility in P. falciparum field isolates [4]. This is supported by ex vivo [5][6][7][8][9][10][11][12][13][14][15][16] and in vivo drug-susceptibility studies [5,17,18]. Findings suggest that chloroquine might be re-used in the future as an option for the treatment and/or chemoprophylaxis on the condition that chloroquine sensitivity is maintained in the area.…”

“…Findings suggest that chloroquine might be re-used in the future as an option for the treatment and/or chemoprophylaxis on the condition that chloroquine sensitivity is maintained in the area. As the parasite is "skilled" in evading anti-malarial treatments, continuous surveillance on longitudinal persistence of chloroquine susceptibility by molecular and phenotypic analysis [8,16,18,19] is needed.…”

Population Genetics and Molecular Epidemiology of Eukaryotes

“…The existence and importance of this reservoir could only be uncovered by a molecular method. Molecular surveillance of specific polymorphisms was also used to demonstrate high degrees of susceptibility (61, 70, 73, 87), sustained resistance (60) or high risk for resistance (89) in specific countries. In each case, ongoing molecular surveillance is suggested as an early warning mechanism for the arrival or development of resistance.…”