Plasmodium vivax parasites with chloroquine resistance (CQR) are already circulating in the BrazilianAmazon. Complete single-nucleotide polymorphism (SNP) analyses of coding and noncoding sequences of the pvmdr1 and pvcrt-o genes revealed no associations with CQR, even if some mutations had not been randomly selected. In addition, striking differences in the topologies and numbers of SNPs in these transporter genes between P. vivax and P. falciparum reinforce the idea that mechanisms other than mutations may explain this virulent phenotype in P. vivax.Plasmodium vivax is the most widely distributed human malaria parasite, causing approximately 80 to 300 million clinical cases of malaria each year (17). Numerous factors indicate that this burden will increase due to the emergence and spread of chloroquine-resistant parasites (3, 17).More than 50% of the malaria cases in Latin America occur in Brazil, and P. vivax predominates as the causative agent (16,21). Notably, failures of chloroquine treatment of P. vivax malaria in the Brazilian Amazon city of Manaus have been reported recently (1). The local confirmation of the presence of active P. vivax parasites resisting chloroquine at the proposed minimal effective concentration in plasma for sensitive strains is a public health concern deserving attention.Point mutations in two digestive-vacuole membrane proteins of P. falciparum, the P. falciparum chloroquine resistance transporter (PfCRT) and multidrug resistance 1 protein (PfMDR1), have been associated with chloroquine resistance (CQR), albeit to different extents (2, 10). Orthologues of these proteins in P. vivax (P. vivax CRT-O [PvCRT-O] and PvMDR1) have been identified previously (6, 15, 18), and recently, pvmdr1 mutant alleles were suggested to be associated with both in vitro and in vivo CQR in Southeast Asia (6,20).Here, we report a single-nucleotide polymorphism (SNP) analysis of pvmdr1 and pvcrt-o genes in P. vivax isolates from chloroquine-treated patients with and without recrudescent disease in the Brazilian Amazon region. In addition to complete coding sequences, we analyzed sequences from 5Ј flanking regions and introns.Field isolates were collected during a 28-day in vivo chloroquine efficacy study conducted in the city of Manaus, Brazil (8). Plasmatic chloroquine levels in all volunteers were measured by high-performance liquid chromatography on day 3 to confirm adequate dosing and good absorption of the oral chloroquine intake (three doses of 10, 7.5, and 7.5 mg/kg of body weight in 150-mg tablet form at 24-h intervals). Clinical treatment failure was defined as the occurrence of a positive blood smear result (confirmed by PCR diagnostic analysis) on day 14, 21, or 28 and the presence of parasites in peripheral blood (collected on the same day as the positive blood smear) containing Ͼ10 ng/ml of chloroquine as determined by high-performance liquid chromatography (7). Measurements of chloroquine and its active metabolite desethylchloroquine in whole blood were not obtained, as plasma samples were c...

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Changes in the course of pregnancy were very frequent during acute malaria attacks, despite the low frequency of abortion. The present results do not highlight specific risk factors, suggesting that any pregnant woman may be at risk for the threat of abortion or for abortion during acute malaria attacks.

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Introduction Plasmodium vivax is the most prevalent malaria species in the American region. Brazil accounts for the higher number of the malaria cases reported in pregnant women in the Americas. This study aims to describe the characteristics of pregnant women with malaria in an endemic area of the Brazilian Amazon and the risk factors associated with prematurity and low birth weight (LBW).Methods/Principal FindingsBetween December 2005 and March 2008, 503 pregnant women with malaria that attended a tertiary health centre were enrolled and followed up until delivery and reported a total of 1016 malaria episodes. More than half of study women (54%) were between 20–29 years old, and almost a third were adolescents. The prevalence of anaemia at enrolment was 59%. Most women (286/503) reported more than one malaria episode and most malaria episodes (84.5%, 846/1001) were due to P. vivax infection. Among women with only P. vivax malaria, the risk of preterm birth and low birth weight decreased in multigravidae (OR, 0.36 [95% CI, 0.16–0.82]; p = 0.015 and OR 0.24 [95% CI, 0.10–0.58]; p = 0.001, respectively). The risk of preterm birth decreased with higher maternal age (OR 0.43 [95% CI, 0.19–0.95]; p = 0.037) and among those women who reported higher antenatal care (ANC) attendance (OR, 0.32 [95% CI, 0.15–0.70]; p = 0.005).ConclusionThis study shows that P. vivax is the prevailing species among pregnant women with malaria in the region and shows that vivax clinical malaria may represent harmful consequences for the health of the mother and their offsprings particularly on specific groups such as adolescents, primigravidae and those women with lower ANC attendance.