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BackgroundAn accurate diagnosis is essential for the rapid and appropriate treatment of malaria. The accuracy of the histidine-rich protein 2 (PfHRP2)-based rapid diagnostic test (RDT) Palutop+4® was assessed here. One possible factor contributing to the failure to detect malaria by this test is the diversity of the parasite PfHRP2 antigens.MethodsPfHRP2 detection with the Palutop+4® RDT was carried out. The pfhrp2 and pfhrp3 genes were amplified and sequenced from 136 isolates of Plasmodium falciparum that were collected in Dakar, Senegal from 2009 to 2011. The DNA sequences were determined and statistical analyses of the variation observed between these two genes were conducted. The potential impact of PfHRP2 and PfHRP3 sequence variation on malaria diagnosis was examined.ResultsSeven P. falciparum isolates (5.9% of the total isolates, regardless of the parasitaemia; 10.7% of the isolates with parasitaemia ≤0.005% or ≤250 parasites/μl) were undetected by the PfHRP2 Palutop+4® RDT. Low parasite density is not sufficient to explain the PfHRP2 detection failure. Three of these seven samples showed pfhrp2 deletion (2.4%). The pfhrp3 gene was deleted in 12.8%. Of the 122 PfHRP2 sequences, 120 unique sequences were identified. Of the 109 PfHRP3 sequences, 64 unique sequences were identified. Using the Baker’s regression model, at least 7.4% of the P. falciparum isolates in Dakar were likely to be undetected by PfHRP2 at a parasite density of ≤250 parasites/μl (slightly lower than the evaluated prevalence of 10.7%). This predictive prevalence increased significantly between 2009 and 2011 (P = 0.0046).ConclusionIn the present work, 10.7% of the isolates with a parasitaemia ≤0.005% (≤250 parasites/μl) were undetected by the PfHRP2 Palutop+4® RDT (7.4% by the predictive Baker’model). In addition, all of the parasites with pfhrp2 deletion (2.4% of the total samples) and 2.1% of the parasites with parasitaemia >0.005% and presence of pfhrp2 were not detected by PfHRP2 RDT. PfHRP2 is highly polymorphic in Senegal. Efforts should be made to more accurately determine the prevalence of non-sensitive parasites to pfHRP2.

BackgroundDuffy blood group polymorphisms are important in areas where Plasmodium vivax is present because this surface antigen is thought to act as a key receptor for this parasite. In the present study, Duffy blood group genotyping was performed in febrile uninfected and P. vivax-infected patients living in the city of Nouakchott, Mauritania.MethodsPlasmodium vivax was identified by real-time PCR. The Duffy blood group genotypes were determined by standard PCR followed by sequencing of the promoter region and exon 2 of the Duffy gene in 277 febrile individuals. Fisher's exact test was performed in order to assess the significance of variables.ResultsIn the Moorish population, a high frequency of the FYBES/FYBES genotype was observed in uninfected individuals (27.8%), whereas no P. vivax-infected patient had this genotype. This was followed by a high level of FYA/FYB, FYB/FYB, FYB/FYBES and FYA/FYBES genotype frequencies, both in the P. vivax-infected and uninfected patients. In other ethnic groups (Poular, Soninke, Wolof), only the FYBES/FYBES genotype was found in uninfected patients, whereas the FYA/FYBES genotype was observed in two P. vivax-infected patients. In addition, one patient belonging to the Wolof ethnic group presented the FYBES/FYBES genotype and was infected by P. vivax.ConclusionsThis study presents the Duffy blood group polymorphisms in Nouakchott City and demonstrates that in Mauritania, P. vivax is able to infect Duffy-negative patients. Further studies are necessary to identify the process that enables this Duffy-independent P. vivax invasion of human red blood cells.

Abstract. Mapping and anticipating risk is a major issue in the fight against malaria, a disease causing an estimated one million deaths each year. Approximately half the world's population is at risk and it is of prime importance to evaluate the burden of malaria at the spatial as well as the temporal level. The role of the environment with regard to the determinants of transmission and burden of the disease are described followed by a discussion of special issues such as urban malaria, human population mapping and the detection of changes at the temporal scale. Risk maps at appropriate scales can provide valuable information for targeted control and the present review discusses the essentials of principles, methods, advantages and limitations of remote sensing along with a presentation of ecological, meteorological and climatologic data which rule the distribution of malaria. The panel of commonly used analytic methods is examined and the methodological limitations are highlighted. A review of the literature details the increasing interest in the use of remotely sensed data in the study of malaria, by mapping or modeling several malariometric indices such as prevalence, morbidity and mortality, which are discussed with reference to vector breeding, vector density and entomological inoculation rate, estimates of which constitute the foundation for understanding endemicity and epidemics.

Polymorphisms in the

The prevalence of mutations associated with antifolate resistance is low in Mauritania. Further studies are required to determine the roles of pvmdr1 mutations and gene amplification in conferring drug resistance. These data will serve as a baseline for further monitoring of drug-resistant malaria.

BackgroundThe emergence of Plasmodium falciparum resistance to most anti-malarial compounds has highlighted the urgency to develop new drugs and to clarify the mechanisms of anti-malarial drugs currently used. Among them, doxycycline is used alone for malaria chemoprophylaxis or in combination with quinine or artemisinin derivatives for malaria treatment. The molecular mechanisms of doxycycline action in P. falciparum have not yet been clearly defined, particularly at the protein level.MethodsA proteomic approach was used to analyse protein expression changes in the schizont stage of the malarial parasite P. falciparum following doxycycline treatment. A comparison of protein expression between treated and untreated protein samples was performed using two complementary proteomic approaches: two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and isobaric tagging reagents for relative and absolute quantification (iTRAQ).ResultsAfter doxycycline treatment, 32 and 40 P. falciparum proteins were found to have significantly deregulated expression levels by 2D-DIGE and iTRAQ methods, respectively. Although some of these proteins have been already described as being deregulated by other drug treatments, numerous changes in protein levels seem to be specific to doxycycline treatment, which could perturb apicoplast metabolism. Quantitative reverse transcription polymerase chain reaction (RT-PCR) was performed to confirm this hypothesis.ConclusionsIn this study, a specific response to doxycycline treatment was distinguished and seems to involve mitochondrion and apicoplast organelles. These data provide a starting point for the elucidation of drug targets and the discovery of mechanisms of resistance to anti-malarial compounds.

The in vitro activity of ferroquine (FQ) (SR97193), a 4-aminoquinoline antimalarial compound that contains a ferrocenic nucleus, against 15 Plasmodium falciparum strains was assessed and compared with those of chloroquine (CQ), quinine (QN), monodesethylamodiaquine (MDAQ), and mefloquine (MQ). These 15 strains were genotyped for polymorphisms in quinoline resistance-associated genes such as Pfcrt, Pfmdr1, Pfmrp, and Pfnhe-1. FQ was highly active against CQ-resistant parasites or in parasites with reduced susceptibility to QN, MDAQ, or MQ. Encouragingly, we did not find a correlation between responses to FQ and those to other quinoline drugs. These results suggest that no cross-resistance exits between FQ and CQ or quinoline Two of the current options to reduce the morbidity and mortality of malaria are chemoprophylaxis and chemotherapy. During the past 20 years, many strains of Plasmodium falciparum have become resistant to chloroquine and other antimalarial drugs (24). This has prompted a search for an effective alternative antimalarial drug with minimal side effects. The emergence and spread of parasites that are resistant to antimalarial drugs has caused an urgent need for novel compounds to be discovered and developed.An approach to remove aminoquinoline resistance in parasites is to modify the position and the chemical nature of the substituents or the length of the side chain on the quinoline nucleus of the aminoquinoline (12, 34). Recently, many different metals have been incorporated into antimalarial agents (29). Indeed, several organometallic compounds based on chloroquine with a ferrocene nucleus localized at different sites have been synthesized (5-8). This approach is currently being developed by J. Brocard and colleagues (URA-CNRS 402, Lille, France), who have synthesized ferroquine (FQ) {i.e., 7-chloro-4-[(2-N,NЈ-dimethylaminomethyl)ferrocenylmethylamino]quinoline} (Fig. 1). FQ is currently under phase II clinical trial investigations.Only six previous studies investigated the activity of ferroquine against P. falciparum strains isolated from infected patients (1,2,10,21,28,30). The drug susceptibilities of P. falciparum strains vary among different locations, where isolates have different antimalarial resistance backgrounds. It seems that ferroquine activity is independent of chloroquine resistance in P. falciparum (21), and ferroquine antimalarial activity is not influenced by polymorphisms in the Pfcrt gene (Plasmodium falciparum chloroquine resistance transporter), which encodes a protein located in the parasite digestive vacuole and is involved in drug transport and chloroquine resistance (10, 11). The objective of this study was to determine whether genetic polymorphisms in genes associated with quinoline resistance modulate in vitro responses to ferroquine. We assessed polymorphisms in genes that are potentially associated with quinoline resistance: Pfcrt, Pfmdr1 (P. falciparum multidrug resistance gene 1), Pfnhe-1 (P. falciparum sodium/hydrogen exchanger), and Pfmrp (P. falciparum multidru...