Plasmodium falciparumDrug Resistance in Madagascar: Facing the Spread of Unusualpfdhfrandpfmdr-1Haplotypes and the Decrease of Dihydroartemisinin Susceptibility

Abstract

The aim of this study was to provide the first comprehensive spatiotemporal picture of Plasmodium falciparum resistance in various geographic areas in Madagascar. Additional data about the antimalarial resistance in the neighboring islands of the Comoros archipelago were also collected. We assessed the prevalence of pfcrt, pfmdr-1, pfdhfr, and pfdhps mutations and the pfmdr-1 gene copy number in 1,596 P. falciparum isolates collected in 26 health centers ( In recent decades, the emergence and subsequent spread of Plasmodium falciparum chloroquine (CQ)-and sulfadoxinepyrimethamine (SP)-resistant parasites across areas where malaria is endemic have been a challenge to malaria control programs (41, 44). Substantial advances toward gaining an understanding of the genetic basis of antimalarial drug resistance have been made (14). Molecular evolutionary studies have concluded that the CQ-resistant P. falciparum chloroquine resistance transporter (pfcrt) and high-level pyrimethamine-resistant dihydrofolate (pfdhfr) alleles have emerged in a limited number of independent foci, from which they have rapidly spread in the local vicinity and have then invaded areas continent-wide and transferred between continents (1, 36). These lessons of the past have, first, stimulated changes in antimalarial treatment policies by introducing combinations of drugs that act on different targets and, second, resulted in the implementation of effective monitoring systems to detect as early as possible the emergence of resistant parasites on the basis of the assessment of the therapeutic efficacies of antimalarials (25, 46), determination of the decreased sensitivity of the parasites to drugs in vitro (4), and the detection of an increasing prevalence of molecular markers related to drug resistance (24).According to data published from 2002 to 2006, the epidemiological features of P. falciparum CQ and SP resistance differ considerably between Madagascar and the Comoros Islands, two countries located close to each other in the southwestern Indian Ocean (43). In vitro CQ resistance was moderate in Madagascar (29,33,45), although the level of therapeutic efficacy was declining. During that time, the rate of CQ resistance was high in the Comoros Islands (22,23,30). Likewise, pyrimethamine resistance was absent in Madagascar (28, 32) but was present at high levels in the Comoros Islands (23). The most recent in vivo data obtained on the basis of the WHO 28-day follow-up protocol, conducted in 2006 and 2007 at multiple sites, have confirmed that resistance to all antimalarials except CQ in Madagascar remains rare. Indeed, the prevalence of the clinical failure of treatment with amodiaquine, SP and the combination artesunate and amodiaquine was Ͻ5%, while the rate of failure of treatment with CQ was 44% (19). However, the recent demonstration of the introduction of multidrug-resistant P. falciparum parasites into Madagascar from the Comoros Islands (18) and the emergence of the uncommon dihydrofolate reductase I164L genotype in P. falciparum parasi...

High Prevalence of Asymptomatic Malaria in a Tribal Population in Eastern India

“…It has been observed that P. falciparum infection can persist asymptomatically in semi-immune individuals for more than 18 months when the possibility of reinfection is excluded (14). Similar to the observation of our present study, the persistence of asymptomatic P. falciparum infection interseasonally, in areas with seasonal transmission (15), has been reported in African countries (12,16,17). Such findings have driven presumptive intermittent antimalarial treatment strategies for asymptomatic carriers, regardless of their infection status, to reduce the disease burden in African countries.…”

“…The region of the pfATPase6 gene spanning codon 769 was amplified as described previously (9). A portion of the pfdhfr gene spanning codons 16, 51, 59, 108, and 164 and a portion of the pfdhps gene spanning codons 436, 437, 540, 581, and 613 were amplified by two rounds of PCR using the primers described earlier (11,12).…”

Origins of the Recent Emergence of Plasmodium falciparum Pyrimethamine Resistance Alleles in Madagascar

“…For each patient with a positive RDT result and after informed consent had been obtained, blood samples either were collected from a finger prick and placed onto filter paper or were collected by venipuncture and placed into EDTA-containing tubes. The patients were then promptly treated according to the national malaria policy with a combination of artemether plus lumefantrine (Coartem; Novartis, Basel, Switzerland) in the Comoros Islands (17) (2). Venous blood samples collected in EDTA-containing tubes were transported to Antananarivo, Madagascar, at ϩ4°C within 24 to 48 h of collection.…”

“…However, recent studies performed in Madagascar have shown that the situation is deteriorating and have demonstrated the introduction of P. falciparum multidrug-resistant parasites into Madagascar from the Comoros Islands (17), the rapid rise in the frequency of P. falciparum parasites with both pfdhfr and dhps mutations, and the alarming emergence of the single pfdhfr 164L allele from isolates collected during the last 3 years (2).…”

Analogs of natural aminoacyl-tRNA synthetase inhibitors clear malaria in vivo

“…Because malaria parasites contain an essential organelle of bacterial origin, the apicoplast, numerous antibacterials kill malaria parasites (1-4) and are commonly used in malaria prophylaxis or as components of multiple drug therapies (5,6). However, the emergence of multiresistant parasites compromises the efficacy of many existing chemotherapies, leading to a growing urgency for the search of new antimalarials (7)(8)(9)(10)(11).…”