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Am. J. Trop. Med. Hyg., 76(6), 2007, pp. 1079-1083
Copyright © 2007 by The American Society of Tropical Medicine and Hygiene

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PREVALENT PFMDR1 N86Y MUTANT PLASMODIUM FALCIPARUM IN MADAGASCAR DESPITE ABSENCE OF PFCRT MUTANT STRAINS

MARIE-ANGE RASON, HERILALAINA B. ANDRIANANTENAINA, FRÉDÉRIC ARIEY, ANDRIANIRINA RAVELOSON, OLIVIER DOMARLE, AND MILIJAONA RANDRIANARIVELOJOSIA*
Unité de Recherche sur le Paludisme, Antananarivo, Institut Pasteur de Madagascar, Madagascar; Institut Pasteur de Cambodge, Phnom Pehn, Cambodge; Service de Lutte Contre le Paludisme, Ministère de la Santé et du Planning Familial, Antananarivo Madagascar


ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
We assessed the status of point mutations associated with chloroquine resistance in pfcrt codon 76 and in pfmdr1 codon 86 among Plasmodium falciparum isolates from symptomatic patients in 3 sites in Madagascar. The in vitro susceptibility of P. falciparum isolates to quinoline-containing drugs was also determined. All isolates (N = 117) successfully typed were pfcrt wild-type, except one from Tsiroanomandidy (1 of 27). However, 67.5% (95% CI: 58.2–75.9%) of these isolates contained mutant pfmdr1 86Y. The pfmdr1 N86Y mutation is associated with higher mefloquine susceptibility, but it did not affect the sensitivity of parasites to chloroquine or quinine. Our findings demonstrate that pfmdr1 mutant P. falciparum are prevalent in Madagascar and confirm the low prevalence of pfcrt mutant P. falciparum after 60 years of chloroquine use. They provide additional field-based evidence for increased mefloquine susceptibility in pfmdr1 mutant P. falciparum and are suggestive of the intrahost selection of pfmdr1 mutant parasites.


INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The use of antimalarial drugs for curative and preventive purposes is pivotal in current strategies to control malaria in Madagascar. Chloroquine, first introduced into Madagascar in 1945, has been used as the first-line treatment of uncomplicated malaria.1–3 Between 1949 and 1962, widespread use of chloroquine for malarial chemoprophylaxis, mainly in children, had a major impact on malaria control.2 A shortage of chloroquine was one of the main causes of a malaria outbreak that killed thousands of people on the island in the 1980s. After this outbreak, chloroquine was widely distributed through 35,432 dispensatories to ensure its availability in all villages, and this drug was recommended for treatment of presumptive malaria (fever).4,5 Low-grade (R1 or R2) chloroquine resistance and late clinical and parasitological failures have been reported.6,7 Today, chloroquine is also available in groceries, even in rural areas. It remains the most widely used antimalarial drug, with or without medical prescription, and prepackaged chloroquine has been recommended by the Ministry of Health and Family Planning (MoH) since the end of 2003 for treatment at home of fever in children under the age of 5 years.3,8

The MoH and the Institut Pasteur de Madagascar (IPM) created the Réseau d’Etude de la Résistance-Paludisme (RER) in 1999. This national network for the surveillance of malaria resistance was designed to alleviate the lack of medical teams for (a) routine monitoring of the therapeutic effectiveness of antimalarial drugs at peripheral health centers and (b) malaria diagnosis by microscopy. IPM is responsible for malaria parasite phenotyping and genotyping.1,7,9 The Malagasy MoH approved the experimental protocols used for this study. The chloroquine-resistance marker gene, pfcrt, has been typed for clinical Plasmodium falciparum isolates collected in 2001 and 2002. No P. falciparum isolate harboring pfcrt 76T was detected in the seaport towns of Mahajanga (northwestern region), Toamasina (eastern region), Tolagnaro (southern costal region), or Moramanga (eastern foothill region).7,9 The prevalence of mutant pfcrt 76T was very low in Tsiroanomandidy (western foothill region) and in Andapa (northern coastal region).3 In this context, genotyping of chloroquine-resistance markers remains a useful tool for chloroquine-resistance surveillance.

We report herein the results of RER activities of 2004. The P. falciparum isolates collected from Tsiroanomandidy, Saharevo, and Sainte Marie were examined to assess their in vitro susceptibility to quinoline-based drugs and to monitor the status of point mutations in pfcrt codon 76 and in pfmdr1 codon 86, which have been associated with chloroquine resistance.10–14


MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Study sites and parasite samples. The three study sites—Tsiroanomandidy, Sainte Marie, and Saharevo—are shown in Figure 1Go. These sites are part of the national network for drug-resistance surveillance with health workers trained and equipped to diagnose malaria with microscopy. It is worth mentioning that parasitological malaria diagnosis is not possible in most of Madagascar.


Figure 1
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  		FIGURE 1. Map of Madagascar showing parasite collection sites. Legend: Black circles indicate the study sites involved in surveillance of malaria-drug resistance in 2004 reported herein. Black rhombi indicate sites where occurrence of pfcrt mutants has already been assessed. No pfcrt mutant was detected at Mahajanga, Toamasina, or Tolagnaro. The first cases of pfcrt K76T mutant P. falciparum were detected among samples collected in 2001 in Tsiroanomandidy (1 of 51 samples of CVIDT haplotype) and in Andapa (5 of 132 samples; both CVIET and CVIDT mutant haplotypes were present). Institut Pasteur de Madagascar is located at Antananarivo.

 
Tsiroanomandidy is in the midwestern part of Madagascar, in the foothill area. This region is characterized by meso- to hyperendemic malaria.15 The island of Sainte Marie is a tourist site on the rainy eastern coast, where most of the local population is poor. This region is characterized by hyperendemic malaria.15 Tsiroanomandidy and Sainte Marie are part of health districts in which malaria chemoprophylaxis using chloroquine was actively implemented from 1949 to 1962.2 Chloroquine is still used in these areas.

Saharevo is a village in the Moramanga district. A primary health care center has been built in this village, and permanent drug pressure related to chloroquine use has been recorded. The population of Saharevo ({approx} 300 inhabitants) was subjected to mass annual chloroquine treatment from 1995 to 2000. During this period and up to 2003, chloroquine was the systematic first-line antimalarial treatment of confirmed, uncomplicated malaria cases.

Clinical P. falciparum isolates were obtained in venous blood collected into EDTA-coated tubes. Blood samples were obtained from patients over the age of 2 years, after informed consent had been granted, from February to June 2004 in Saharevo (N = 64), Sainte Marie (N = 26), and Tsiroanomandidy (N = 27). Samples were transported, at +8°C, to the Malaria Research Unit of the IPM at Antananarivo. The medical teams at the local health centers were responsible for all decisions concerning treatment of their patients. Patients were not followed up, and treatment outcomes were therefore not recorded.

In vitro testing of antiplasmodial agents. The in vitro response of P. falciparum isolates was determined by the isotopic method.1,9,16 We tested 114 isolates against at least one of the following drugs: chloroquine, monodesethylamodiaquine, quinine, and mefloquine. All isolates tested met the following criteria: parasitemia ≥ 0.1%, absence of other Plasmodium species, no declared antimalarial drug intake during the last 7 days, and transport at +8°C to the IPM at Antananarivo within 48 hours of blood collection. P. falciparum-harboring red blood cells were washed with RPMI 1640 (Gibco-BRL Laboratories, Grand Island, NY) and resuspended in complete RPMI 1640 supplemented with 10% (v/v) AB+ human serum (Abcys, Chausson, Paris), at a hematocrit of 1.5%. In vitro testing was carried out in 96-well plates (200 µL of parasite suspension per well). Parasite growth was assessed by adding tritium-labeled hypoxanthine (Amersham Bioscience, Saclay, France) to the culture medium at a concentration of 0.5 µCi per well. Parasitemia ranged from 0.1% to 0.5% (high parasitemia was adjusted to 0.5% by adding freshly prepared uninfected erythrocytes). Plates were incubated at 37°C for 42 hours in a humidified MIC-101 modulator incubator chamber (Billups-Rothenberg, Del Mar, CA) flushed with a gas mixture containing 5% CO2, 5% O2, and 90% N2. Plates were then frozen and defrosted, and the contents of each well were harvested on fiberglass paper (Wallac, Turku, Finland). Tritium-labeled hypoxanthine incorporation was determined with a beta counter (Wallac, model 1450). Tests were considered to be interpretable if tritium-labeled hypoxanthine incorporation gave > 1,000 counts per minute in the drug-free wells. Growth curves were obtained, and 50% inhibitory concentration (IC50) values were calculated by log–probit approximation.17 The threshold IC50 values for in vitro resistance were 100 nM for chloroquine, 60 nM for monodesethylamodiaquine, 30 nM for mefloquine (although Woodrow and Krishna suggested a threshold at 50 nM14), and 800 nM for quinine.18,19

DNA extraction and PCR/RFLP to detect pfcrt K76T and pfmdr1 N86Y mutations. Red blood cell pellets from each sample were kept at –20°C until use. Parasite DNA was extracted from 200 µL of red blood cell pellets by phenol–chloroform purification.20 The pfcrt and pfmdr1 genes of P. falciparum were amplified by nested PCR, using a Mastercycler thermal cycler (Eppendorf, Hamburg, Germany) as described at http://medschool.umaryland.edu/cvd/2002_pcr_asra.asp.

The pfcrt and pfmdr1 nested-PCR products were digested with ApoI and with AflIII (New England Biolabs, Hitchin, UK), respectively. The restricted products (15 µL) were subjected to electrophoresis in a 2% agarose gel, stained with 0.5 µg/mL ethidium bromide, and viewed under ultraviolet light. The 145-bp pfcrt PCR product contains one ApoI site if codon 76 of the pfcrt gene encodes a lysine (K76), resulting in restriction fragments 99 and 46 bp in length. The 291-bp pfmdr1 PCR product contains a single AflIII site if codon 86 is mutated to encode tyrosine (86Y), resulting in the generation of fragments 165 and 126 bp long. If the pfmdr1 N86Y or the pfcrt K76T mutation was detected in a sample, a technician repeated the entire process, blind, from DNA extraction to PCR product analysis by digestion and electrophoresis.

For each PCR and each digestion, DNA from P. falciparum strains FCM29 (chloroquine-resistant) and 3D7 (chloroquine-susceptible), which are maintained in continuous culture in the laboratory, were used as positive controls. H2O was used as a negative control.

Data analysis. Statistical analyses were performed with Epi-Info software. The in vitro activity of the drugs was expressed as the mean IC50 for all isolates. Mean IC50s were compared by t tests. We analyzed the frequency of mutants with mixed genotypes (wild-type and mutated gene both present), which were counted as "mutation present." Frequencies were compared, using {chi}2 or Fisher’s exact test. The level of statistical significance was set at P = 0.05.


RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Genotyping. All 117 nested PCRs for pfcrt and pfmdr1 were successful (Table 1Go). All pfcrt PCR products were digested by ApoI, indicating that the P. falciparum isolates tested were all wild-type for pfcrt codon 76 (K76) except for one isolate (1 of 27) from Tsiroanomandidy (76T). Thus among examined samples, the frequency of isolates harboring pfcrt 76T mutant parasites was 3.7% (95% CI: 0.09–18.9%) in Tsiroanomandidy.


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TABLE 1
Detection of pfmdr1 N86Y mutation by PCR/RFLP in clinical P. falciparum isolates collected from Madagascar in 2004*
 
A pfmdr1 PCR product digested totally or partly by AflIII was obtained with 79 of the 117 isolates of P. falciparum. Thus, 67.5% (95% CI: 58.2–75.9%) of the tested isolates contained the pfmdr1 tyrosine-86 (86Y) mutation. Twenty-one isolates (17.9%) were mixed; they contained both mutant pfmdr1 86Y parasites and parasites with an AflIII-insensitive product. The frequency of isolates harboring pfmdr1 N86Y mutant parasites was 75% (48 of 64) for Saharevo, 53.8% (14 of 26) for Sainte Marie, and 62.9% (17 of 27) for Tsiroanomandidy.

In vitro testing of antimalarial drugs. We tested 114 P. falciparum isolates with at least one of the following drugs: chloroquine, monodesethylamodiaquine, quinine, and mefloquine. On average, about 65% (74 of 114) of tests could be interpreted. Because preliminary data analysis indicated no significant differences between sites, the results obtained for the three study sites were considered together.

Monodesethylamodiaquine and quinine. The successfully tested isolates were all susceptible to quinine (N = 71) and monodesethylamodiaquine (N = 71). The mean IC50 of quinine was 70.6 nM (95% CI: 59.2–82.0 nM), with a median of 64.6 nM. The mean IC50 of monodesethylamodiaquine was 10.8 nM (95% CI: 9.2–12.4 nM), with a median of 9.4 nM.

Chloroquine and mefloquine. The mean IC50 of chloroquine was 29.9 nM (N = 74; 95% CI: 24.9–34.9 nM), with a median of 22.8 nM. All but one of the successfully tested isolates (1.4%) were sensitive to chloroquine. The chloroquine-resistant isolate was from Saharevo. The IC50 of chloroquine was 106.4 nM for this strain, which was susceptible to the other drugs tested. It is of pfcrt wild-type. The mean IC50 of mefloquine was 9.8 nM (N = 59; 95% CI: 7.8–11.8 nM), with a median of 7.3 nM. All but one of the successfully tested isolates were mefloquine-sensitive. The mefloquine-resistant isolate was from Saharevo and had an IC50 of 54.6 nM for mefloquine. It was of pfmdr1 wild-type and showed susceptibility to the other drugs tested. However, our results indicate that mefloquine was the most potent of the four quinoline-containing drugs tested in vitro, with activity levels 3 times higher than those of chloroquine (P < 0.001) and 7.2 times higher than those of quinine (P < 0.001).

The in vitro susceptibility of reference strains of P. falciparum to quinoline-based antimalarials is reported in Table 3Go.


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TABLE 3
In vitro susceptibility of reference strains of P. falciparum to quinoline-based antimalarial drugs (n = 4)
 
Correlation between in vitro response of P. falciparum isolates to drugs and presence of mutant pfmdr1 N86Y parasites. The presence or absence of mutant pfmdr1 N86Y parasites did not affect the in vitro susceptibility of P. falciparum isolates to chloroquine and quinine (Table 2Go). The situation was different for mefloquine. The mean IC50 of mefloquine was 14.7 nM for the wild-type parasites (pfmdr1 N86) versus 6.9 nM for their counterparts containing mutant pfmdr1 86Y. Based on mean IC50s, P. falciparum isolates harboring mutant parasites were 2.13 times more sensitive to mefloquine than were wild-type parasites in vitro, and mutant parasites were 1.38 times less sensitive to monodesethylamodiaquine, although differences were not statistically significant.


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TABLE 2
Correlation between presence of pfmdr1 mutant parasites and in vitro susceptibility of P. falciparum isolates to quinoline-based antimalarial drugs in Madagascar in 2004
 

DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Our findings provide additional field-based evidence for the greater susceptibility to mefloquine of pfmdr1 mutant P. falciparum and demonstrate above all that pfmdr1 mutant P. falciparum is present at a high prevalence despite the absence of pfcrt mutant strains in Madagascar. The occurrence of pfmdr1 mutants probably results from the cumulative effects of drug pressure and the intrahost selection of pfmdr1 mutant parasites, related to the use of chloroquine over the last 60 years. Previously, the sequencing of pfmdr1 in 31 P. falciparum isolates collected in 2001 from Tolagnaro, in the southern costal area of Madagascar, showed that mutant pfmdr1 N86Y was present in 25 (80.6%) of these isolates, in the absence of the mutation at codon 1042 (Ariey, unpublished).

The situation in Madagascar looks unique and unusual as most parasites isolates are sensitive to chloroquine in vitro, and pfcrt mutant parasites are at low prevalence. It is worth mentioning that, in our previous work, we reported the occurrence of few pfcrt mutants in Tsiroanomandidy (1 of 51) as in 2001.3 Consequently, detection of the pfcrt mutant P. falciparum in Tsiroanomandidy (1 of 27 isolates) in our current results indicates circulation of mutant parasites in this region. The low frequency of isolates resistant to chloroquine in vitro contrasts interestingly with the non-negligible level of overall crude chloroquine treatment failure of 15–40% detected within a 14-day follow-up (late clinical or parasitological failure in almost all cases) recorded over the last few years in Madagascar and at the 3 study sites investigated here.7,21–23

Basco et al. reported a positive correlation between the asparagine to tyrosine mutation at position 86 (N86Y) in pfMDR1 and chloroquine resistance in vitro in Sub-Saharan Africa.24 These findings contrast with our results. Regardless of the status of the pfmdr1 codon 86, isolates from Madagascar do not display high levels of resistance to chloroquine, as does the reference strain P. falciparum FCM29. This would suggest that the genetic background of most P. falciparum parasites in Madagascar is not yet favorable for development of a high level of chloroquine resistance; the N86Y mutation of pfmdr1 is also not sufficient itself to generate measurable levels of resistance to chloroquine.

Our current results indicated that all the isolates tested were susceptible to quinine (the drug recommended for the management of severe malaria in Madagascar) and to monodesethylamodiaquine (a combination of amodiaquine and artesunate is recommended in the recently revised malaria therapy policy for Madagascar). Mefloquine is recommended for malaria prevention for travelers to Madagascar (http:// www.pasteur.mg/prevpal.html) but is very rarely used by local people because of its high cost.25 Our current study shows that P. falciparum is potentially susceptible to mefloquine in Madagascar, and this is reassuring to the health authorities. In vitro monitoring for assessing or predicting the susceptibility of malaria parasites to drugs is required to generate useful and usable information. The detection of parasites highly resistant to mefloquine in a country like Madagascar, where most parasites are mefloquine-susceptible, should facilitate identification of new genetic markers of resistance for this drug.

The triple mutations S1034C/N1042D/D1246Y in pfmdr1, highly prevalent in South America, have been shown to increase parasite susceptibility to mefloquine, halofantrine, and artemisinin.26 The tyrosine-86 allele of the pfmdr1 gene of P. falciparum is associated with greater susceptibility to artemisinin.13,27 Amplification of pfmdr1 has been shown to be associated with mefloquine treatment failure and in vitro resistance.14,28,29 Polymorphisms at amino-acid residues 86, 184, 1034, 1042, and 1246 have been associated with changes in susceptibility to chloroquine, quinine, mefloquine and artemisinin in vitro.25,30 A recent study on P. falciparum from Papua New Guinea31 suggested that pfmdr1 N86Y mutation plays a compensatory role in chloroquine-resistant isolates under chloroquine pressure, also increasing the level of chloroquine resistance in K76T parasites to a small extent. In Madagascar, with its virtually isolated malaria, a shift toward the use of ACT (artesunate + amodiaquine) is planned in the newly revised policy for treating malaria. Chloroquine will eventually be withdrawn at national level.32 Thus, chloroquine pressure will decrease while ACT pressure will increase. These findings on pfmdr1 in isolates from different malaria-infested continents suggest that the spatial and temporal monitoring of pfmdr1 (mutation and expression) would help to track the evolution of Malagasy P. falciparum in the era of ACT use.

Received December 19, 2006. Accepted for publication January 31, 2007.

Acknowledgments: The authors thank the Direction Provinciale de la Santé de Toamasina and the Service de Santé de District de Santé de Tsiroanomandidy for their collaboration. We also thank the medical team of the Groupe de Recherche sur le Paludisme de l’Institut Pasteur de Madagascar for sample collection.

Financial support: This study was supported financially by the French Government (FSP/RAI), the European Union (RESMALCHIP QLTR-2001-01503), the Institut Pasteur, and the IAEA in Vienna (RAF 6/025).

Disclaimer: We declare that we have no commercial or other association potentially posing a conflict of interest concerning the work reported in this paper.

* Address correspondence to Milijaona Randrianarivelojosia, BP 1274, Antananarivo 101, Madagascar. E-mail: milijaon{at}pasteur.mg Back

Authors’ addresses: Marie-Ange Rason, Herilalaina B. Andrianantenaina, Frédéric Ariey, Olivier Domarle, and Milijaona Randrianarivelojosia, Unité de Recherche sur le Paludisme, BP 1274, Institut Pasteur de Madagascar, Antananarivo (101), Madagascar, Telephone: +261 20 22 412 72, Fax: +261 20 22 415 34, E-mails: mieange{at}pasteur.mg, milijaon{at}pasteur.mg, and domarle{at}pasteur.mg. (Current address for Frédéric Ariey, Institut Pasteur de Cambodge, 5 Boulevard Monivong, BP 983 Phnom Pehn, Cambodge, E-mail: fariey{at}pasteur-kh.org). Andrianirina Raveloson, Service de Lutte Contre le Paludisme, Ministère de la Santé et du Planning Familial, Antananarivo, Madagascar, E-mail: a_raveloson{at}hotmail.com.

Reprint requests: Milijaona Randrianarivelojosia, Unité de Recherche sur le Paludisme, BP 1274 Antananarivo (101), Institut Pasteur de Madagascar, E-mail: milijaon{at}pasteur.mg.


REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Randrianarivelojosia M, Harisoa JL, Rabarijaona LP, Raharimalala LA, Ranaivo L, Pietra V, Duchemin JB, Rakotomanana F, Robert V, Mauclere P, Ariey F, 2002. In vitro sensitivity of Plasmodium falciparum to amodiaquine compared with other major antimalarials in Madagascar. Parassitologia 44: 141–147.[Medline]
  2. Ralamboson D, 1964. Evolution du paludisme à Madagascar et lutte antipalustre. Ann Univ Madagascar 2: 123–133.
  3. Randrianarivelojosia M, Fidock DA, Belmonte O, Valderramos SG, Mercereau-Puijalon O, Ariey F, 2006. First evidence of pfcrt mutant Plasmodium falciparum in Madagascar. Trans R Soc Trop Med Hyg 100: 826–830.[Web of Science][Medline]
  4. Mouchet J, 1998. L’origine des épidémies de paludisme sur les Plateaux de Madagascar et les montagnes d’Afrique de l’est et du sud. Bull Soc Pathol Exot 91: 64–66.[Web of Science][Medline]
  5. Lepers JP, Deloron P, Fontenille D, Coulanges P, 1988. Reappearance of falciparum malaria in central highland plateaux of Madagascar. Lancet 1: 586.[Web of Science][Medline]
  6. Milijaona R, Raharimalala L, Ramambanirina L, Ranaivo LH, Jambou R, 1998. Chimiorésistance de Plasmodium falciparum sur les marges des Hautes Terres malgaches: perspective pour le programme national de lutte. Med Trop (Mars) 58: 261–265.[Medline]
  7. Ariey F, Randrianarivelojosia M, Duchemin JB, Rakotondramarina D, Ouledi A, Robert V, Jambou R, Jahevitra M, Andrianantenaina H, Raharimalala L, Mauclere P, 2002. Mapping of a Plasmodium falciparum pfcrt K76T mutation: a useful strategy for controlling chloroquine resistance in Madagascar. J Infect Dis 185: 710–712.[Web of Science][Medline]
  8. Ratsimbasoa A, Randrianarivelojosia M, Millet P, Soares JL, Rabarijaona L, Rakotoson B, Malvy D, Menard D, 2006. Use of pre-packaged chloroquine for the home management of presumed malaria in Malagasy children. Malar J 5: 79.[Medline]
  9. Rason MA, Ariey F, Rafidimanantsoa L, Andrianantenaina BH, Sahondra Harisoa JL, Randrianarivelojosia M, 2002. Monitoring the drug-sensitivity of Plasmodium falciparum in coastal towns in Madagascar by use of in vitro chemosensitivity and mutation detection tests. Parasite 9: 247–253.[Web of Science][Medline]
  10. Djimde A, Doumbo OK, Cortese JF, Kayentao K, Doumbo S, Diourte Y, Dicko A, Su XZ, Nomura T, Fidock DA, Wellems TE, Plowe CV, Coulibaly D, 2001. A molecular marker for chloroquine-resistant falciparum malaria. N Engl J Med 344: 257–263.[Abstract/Free Full Text]
  11. Fidock DA, Nomura T, Talley AK, Cooper RA, Dzekunov SM, Ferdig MT, Ursos LM, Sidhu AB, Naude B, Deitsch KW, Su XZ, Wootton JC, Roepe PD, Wellems TE, 2000. Mutations in the P. falciparum digestive vacuole transmembrane protein PfCRT and evidence for their role in chloroquine resistance. Mol Cell 6: 861–871.[Web of Science][Medline]
  12. Duraisingh MT, Cowman AF, 2005. Contribution of the pfmdr1 gene to antimalarial drug-resistance. Acta Trop 94: 181–190.[Web of Science][Medline]
  13. Duraisingh MT, Jones P, Sambou I, von Seidlein L, Pinder M, Warhurst DC, 2000. The tyrosine-86 allele of the pfmdr1 gene of Plasmodium falciparum is associated with increased sensitivity to the anti-malarials mefloquine and artemisinin. Mol Biochem Parasitol 108: 13–23.[Web of Science][Medline]
  14. Woodrow CJ, Krishna S, 2006. Antimalarial drugs: recent advances in molecular determinants of resistance and their clinical significance. Cell Mol Life Sci 63: 1586–1596.[Web of Science][Medline]
  15. Robert V, Le Goff G, Andrianaivolambo L, Randimby FM, Domarle O, Randrianarivelojosia M, Raharimanga V, Raveloson A, Ravaonjanahary C, Ariey F, 2006. Moderate transmission but high prevalence of malaria in Madagascar. Int J Parasitol 36: 1273–1281.[Web of Science][Medline]
  16. Desjardins RE, Canfield CJ, Haynes JD, Chulay JD, 1979. Quantitative assessment of antimalarial activity in vitro by a semiautomated microdilution technique. Antimicrob Agents Chemother 16: 710–718.[Abstract/Free Full Text]
  17. Randrianarivelojosia M, Ariey F, Raharimalala LA, Parzy D, Rogier C, Jambou R, 2002. Current absence of pyrimethamine resistance of Plasmodium falciparum in Madagascar. Trans R Soc Trop Med Hyg 96: 557–559.[Web of Science][Medline]
  18. Lim P, Chim P, Sem R, Nemh S, Poravuth Y, Lim C, Seila S, Tsuyuoka R, Denis MB, Socheat D, Fandeur T, 2005. In vitro monitoring of Plasmodium falciparum susceptibility to artesunate, mefloquine, quinine and chloroquine in Cambodia: 2001–2002. Acta Trop 93: 31–40.[Web of Science][Medline]
  19. Aubouy A, Mayombo J, Keundjian A, Bakary M, Le Bras J, Deloron P, 2004. Short report: lack of prediction of amodiaquine efficacy in treating Plasmodium falciparum malaria by in vitro tests. Am J Trop Med Hyg 71: 294–296.[Abstract/Free Full Text]
  20. Ariey F, Chalvet W, Hommel D, Peneau C, Hulin A, Mercereau-Puijalon O, Duchemin JB, Sarthou JL, Reynes JM, Fandeur T, 1999. Plasmodium falciparum parasites in French Guiana: limited genetic diversity and high selfing rate. Am J Trop Med Hyg 61: 978–985.[Abstract]
  21. Randrianasolo L, Randriamanantena A, Ranarivelo L, Ratsimbasoa A, Domarle O, Randrianarivelojosia M, 2004. Monitoring susceptibility to sulfadoxine–pyrimethamine among cases of uncomplicated, Plasmodium falciparum malaria in Saharevo, Madagascar. Ann Trop Med Parasitol 98: 551–554.[Web of Science][Medline]
  22. Raharimalala AL, Randrianarivelojosia M, Randriamanantena A, Ranarivelo LA, Jaureguiberry S, Rason MA, Rakotomalala E, Ariey F, 2000. Sensibilité de Plasmodium falciparum à Sainte Marie dans l’est de Madagascar: études in vivo et in vitro. Arch Inst Pasteur Madagascar 66: 26–31.[Medline]
  23. Willcox ML, Rakotondrazafy E, Andriamanalimanana R, Andrianasolo D, Rasoanaivo P, 2004. Decreasing clinical efficacy of chloroquine in Ankazobe, central highlands of Madagascar. Trans R Soc Trop Med Hyg 98: 311–314.[Web of Science][Medline]
  24. Basco LK, Le Bras J, Rhoades Z, Wilson CM, 1995. Analysis of pfmdr1 and drug susceptibility in fresh isolates of Plasmodium falciparum from sub-Saharan Africa. Mol Biochem Parasitol 74: 157–166.[Web of Science][Medline]
  25. Randrianarivelojosia M, Randrianasolo L, Randremanana RV, Randriamanantena A, Ratsimbasoa A, Rakotoson JD, 2004. Susceptibility of Plasmodium falciparum to the drugs used to treat severe malaria (quinine) and to prevent malaria (mefloquine, cycloguanil) in Comoros Union and Madagascar. S Afr Med J 94: 47–51.[Web of Science][Medline]
  26. Sidhu AB, Valderramos SG, Fidock DA, 2005. pfmdr1 Mutations contribute to quinine resistance and enhance mefloquine and artemisinin sensitivity in Plasmodium falciparum. Mol Microbiol 57: 913–926.[Web of Science][Medline]
  27. Duraisingh MT, Roper C, Walliker D, Warhurst DC, 2000. Increased sensitivity to the antimalarials mefloquine and artemisinin is conferred by mutations in the pfmdr1 gene of Plasmodium falciparum. Mol Microbiol 36: 955–961.[Web of Science][Medline]
  28. Price RN, Uhlemann AC, Brockman A, McGready R, Ashley E, Phaipun L, Patel R, Laing K, Looareesuwan S, White NJ, Nosten F, Krishna S, 2004. Mefloquine resistance in Plasmodium falciparum and increased pfmdr1 gene copy number. Lancet 364: 438–447.[Web of Science][Medline]
  29. Uhlemann AC, McGready R, Ashley EA, Brockman A, Singhasivanon P, Krishna S, White NJ, Nosten F, Price RN, 2007. Intrahost selection of Plasmodium falciparum pfmdr1 alleles after antimalarial treatment on the northwestern border of Thailand. J Infect Dis 195: 134–141.[Web of Science][Medline]
  30. Rohrbach P, Sanchez CP, Hayton K, Friedrich O, Patel J, Sidhu AB, Ferdig MT, Fidock DA, Lanzer M, 2006. Genetic linkage of pfmdr1 with food vacuolar solute import in Plasmodium falciparum. EMBO J 25:3000–3011. Epub June 22, 2006.[Web of Science][Medline]
  31. Mita T, Kaneko A, Hombhanje F, Hwaihwanje I, Takahashi N, Osawa H, Tsukahara T, Masta A, Lum JK, Kobayakawa T, Ishizaki T, Bjorkman A, 2006. Role of pfmdr1 mutations on chloroquine resistance in Plasmodium falciparum isolates with pfcrt K76T from Papua New Guinea. Acta Trop 98: 137–144.[Web of Science][Medline]
  32. Service de Lutte Contre le Paludisme, 2005. Politique nationale de lutte contre le paludisme. Antananarivo: Ministère de la Santé et du Planning Familial, Madagascar.



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