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International audience; Accurate information regarding malaria prevalence at national level is required to design and assess malaria control/elimination efforts. Although many comparisons of microscopy and polymerase chain reaction (PCR)-based methods have been conducted, there is little published literature covering such comparisons in southeast Asia especially at the national level. Both microscopic examination and PCR detection were performed on blood films and dried blood spots samples collected from 8,067 individuals enrolled in a nationwide, stratified, multistage, cluster sampling malaria prevalence survey conducted in Cambodia in 2007. The overall malaria prevalence and prevalence rates of Plasmodium falciparum, Plasmodium vivax, and Plasmodium malariae infections estimated by microscopy (N = 8,067) were 2.74% (95% confidence interval [CI]: 2.39-3.12%), 1.81% (95% CI: 1.53-2.13%), 1.14% (95% CI: 0.92-1.40%), and 0.01% (95% CI: 0.003-0.07%), respectively. The overall malaria prevalence based on PCR detection (N = 7,718) was almost 2.5-fold higher (6.31%, 95% CI: 5.76-6.89%, P < 0.00001). This difference was significantly more pronounced for P. falciparum (4.40%, 95% CI: 3.95-4.90%, P < 0.00001) compared with P. vivax (1.89%, 95% CI: 1.60-2.22%, P < 0.001) and P. malariae infections (0.22%, 95% CI: 0.13-0.35%, P < 0.0001). The significant proportion of microscopy-negative but PCR-positive individuals (289/7,491, 3.85%) suggest microscopic examination frequently underestimated malaria infections and that active case detection based on microscopy may miss a significant reservoir of infection, especially in low-transmission settings.

International audience; BACKGROUND:Human population movement across country borders presents a real challenge for malaria control and elimination efforts in Cambodia and its neighbouring countries. To quantify Plasmodium infection among the border-crossing population, including asymptomatic and artemisinin resistant (AR) parasites, three official border crossing points, one from each of Cambodia's borders with Thailand, Laos and Vietnam, were selected for sampling.METHODS AND FINDINGS:A total of 3206 participants (of 4110 approached) were recruited as they crossed the border, tested for malaria and interviewed. By real-time polymerase chain reaction (RT-PCR), 5.4% of all screened individuals were found to harbour Plasmodium parasites. The proportion was highest at the Laos border (11.5%). Overall there were 97 P. vivax (55.7%), 55 P. falciparum (31.6%), two P. malariae (1.1%) and 20 mixed infections (11.5%). Of identified infections, only 20% were febrile at the time of screening. Of the 24 P. falciparum samples where a further PCR was possible to assess AR, 15 (62.5%) had mutations in the K13 propeller domain gene, all from participants at the Laos border point. Malaria rapid diagnostic test (RDT) pLDH/HRP-2 identified a positivity rate of 3.2% overall and sensitivity compared to RT-PCR was very low (43.1%). Main individual risk factors for infection included sex, fever, being a forest-goer, poor knowledge of malaria prevention methods and previous malaria infection. Occupation, day of the week and time of crossing (morning vs. afternoon) also appeared to play an important role in predicting positive cases.CONCLUSIONS:This study offers a novel approach to identify asymptomatic infections and monitor AR parasite flow among mobile and migrant populations crossing the borders. Similar screening activities are recommended to identify other hot borders and characterise potential hot spots of AR. Targeted "customised" interventions and surveillance activities should be implemented in these sites to accelerate elimination efforts in the region.

Molecular investigations performed following the emergence of sulfadoxine-pyrimethamine (SP) resistance in Plasmodium falciparum have allowed the identification of the dihydrofolate reductase (DHFR) enzyme as the target of pyrimethamine. Although clinical cases of Plasmodium malariae are not usually treated with antifolate therapy, incorrect diagnosis and the high frequency of undetected mixed infections has probably exposed non- P. falciparum parasites to antifolate therapy in many areas. In this context, we aimed to assess the worldwide genetic diversity of the P. malariae dhfr gene in 123 samples collected in Africa and Asia, areas with different histories of SP use. Among the 10 polymorphic sites found, we have observed 7 new mutations (K55E, S58R, S59A, F168S, N194S, D207G, and T221A), which led us to describe 6 new DHFR proteins. All isolates from African countries were classified as wild type, while new mutations and haplotypes were recognized as exclusive to Madagascar (except for the double mutations at nucleotides 341 and 342 [S114N] found in one Cambodian isolate). Among these nonsynonymous mutations, two were likely related to pyrimethamine resistance: S58R (corresponding to C59R in P. falciparum and S58R in Plasmodium vivax ; observed in one Malagasy sample) and S114N (corresponding to S108N in P. falciparum and S117N in P. vivax ; observed in three Cambodian samples).

International audience; Complex, high-dimensional data sets pose significant analytical challenges in the post-genomic era. Such data sets are not exclusive to genetic analyses and are also pertinent to epidemiology. There has been considerable effort to develop hypothesis-free data mining and machine learning methodologies. However, current methodologies lack exhaustivity and general applicability. Here we use a novel non-parametric, non-euclidean data mining tool, HyperCubeH, to explore exhaustively a complex epidemiological malaria data set by searching for over density of events in m-dimensional space. Hotspots of over density correspond to strings of variables, rules, that determine, in this case, the occurrence of Plasmodium falciparum clinical malaria episodes. The data set contained 46,837 outcome events from 1,653 individuals and 34 explanatory variables. The best predictive rule contained 1,689 events from 148 individuals and was defined as: individuals present during 1992-2003, aged 1-5 years old, having hemoglobin AA, and having had previous Plasmodium malariae malaria parasite infection #10 times. These individuals had 3.71 times more P. falciparum clinical malaria episodes than the general population. We validated the rule in two different cohorts. We compared and contrasted the HyperCubeH rule with the rules using variables identified by both traditional statistical methods and non-parametric regression tree methods. In addition, we tried all possible sub-stratified quantitative variables. No other model with equal or greater representativity gave a higher Relative Risk. Although three of the four variables in the rule were intuitive, the effect of number of P. malariae episodes was not. HyperCubeH efficiently sub-stratified quantitative variables to optimize the rule and was able to identify interactions among the variables, tasks not easy to perform using standard data mining methods. Search of local over density in m-dimensional space, explained by easily interpretable rules, is thus seemingly ideal for generating hypotheses for large datasets to unravel the complexity inherent in biological systems.

International audience; We present a case of severe malaria due to Plasmodium malariae. Genetic testing showed that the patient was homozygous for five important gene polymorphisms previously shown to be associated with increased susceptibility to, and/or severity of, severe sepsis. Our case suggests that P. malariae may cause life-threatening disease, and that disease severity may be linked, at least in part, to multiple susceptibility genes.

International audience; A laboratory-confirmed diagnosis is the basis of malaria case management. Rapid diagnostic tests (RDTs) create new opportunities for improved care in endemic areas. Diagnostic performance of OptiMAL-IT and Acon was assessed in comparison with microscopy at 2 sites in Gabon. Between February 2008 and January 2009, 2125 febrile children under 11 years old were diagnosed using microscopy and RDTs. Plasmodial infection was detected more frequently using Acon (27%) and OptiMAL-IT (27%) compared to microscopy (20%) (P < 0.01). Among the samples diagnosed positive by OptiMAL-IT, 78% were infected by Plasmodium falciparum, whereas 99% of positive blood smears were P. falciparum infections, 0.5% Plasmodium malariae, and 0.5% Plasmodium ovale. Both RDTs had similar sensitivity (Se) (94.0%; 95% confidence interval [CI], 92-96), which varied depending on the site. When parasite density was >100 p/microL, the Se of the 2 tests was >98% (95% CI, 96-100). Likewise, the negative predictive values were high and comparable (>98%). Overtreatment with antimalarial drugs was 12%. These tests should be considered as a good alternative to microscopy, allowing not only an efficient and rapid diagnosis of malaria in primary health facilities but also to aid in promoting changes for antimalarial prescription behavior.

To the Editor: We report a case of Plasmodium malariae–related multiple organ dysfunction syndrome (MODS) in a healthy immunocompetent patient. Despite extensive investigation, P. malariae was the only pathogen identified. The patient’s isolates had a combination of mutant alleles that could possibly explain the severity of the infection.

International audience; French Guiana is one of the areas in South America most affected by malaria and where the disease has become a serious public health problem. In spite of this situation, little recent entomological data are available from the main localities where the disease occurs, even though they are crucial for development of an effective vector control strategy. A longitudinal entomological survey was carried out from March 2000-February 2002 in three Amerindian villages, namely Twenké, Taluène and Cayodé, located in the Amazonian forest of the Upper-Maroni area, to assess anopheline mosquitoes and malaria transmission dynamics. Anopheles darlingi (Diptera: Culicidae) was the most abundant mosquito species caught during the study. This efficient American malaria vector was active the entire year, but showed an evident peak of abundance during the main rainfall season, from April-June, with an average human biting rate of 255.5 bites per person per night. Parity rates were homogeneous all year, indicating no significant seasonal variability in female survival rates. Estimated vectorial capacity indices were higher during the rainy season, even though the risk of transmission was present throughout the year (VCI > 1). A total of 14 An. darlingi were found infected with Plasmodium falciparum, Plasmodium vivax or Plasmodium malariae. The annual circumsporozoite indices were 0.15, 0.14 and 0.05, and the entomological inoculation rates were 22.8, 27.4 and 14.4 infected bites per person per year in Twenké, Taluène and Cayodé, respectively. An. darlingiwas endo-exophagic and rather exophilic in these localities. The species was collected throughout the night but was more aggressive between 21:30-03:30 h and after 05:30 h. Parity rates were homogeneous during the entire night. Impregnated hammock and/or bed nets, coupled with the use of mosquito repellents, as well as the early treatment of malarial cases, appear to be the most suitable tools for fighting malaria in these Amerindian villages since the spraying of residual insecticides is inefficient because of vector biology and the housing structure.

Background Malaria diagnosis is vital to efficient control programmes and the recent advent of malaria rapid diagnostic tests (RDTs) provides a reliable and simple diagnostic method. However a characterization of the efficiency of these tests and the proteins they detect is needed to maximize RDT sensitivity. Methods Plasmodial lactate dehydrogenase (pLDH) gene of wild isolates of the four human species of Plasmodium from a variety of malaria endemic settings were sequenced and analysed. Results No variation in nucleotide was found within Plasmodium falciparum, synonymous mutations were found for Plasmodium malariae and Plasmodium. vivax; and three different types of amino acid sequence were found for Plasmodium ovale. Conserved and variable regions were identified within each species. Conclusion The results indicate that antigen variability is unlikely to explain variability in performance of RDTs detecting pLDH from cases of P. falciparum, P. vivax or P. malariae malaria, but may contribute to poor detection of P. ovale.

International audience; INTRODUCTION:Malaria has been eradicated in Tunisia since 1979. Although it continues to be evoked in the case of fever after travel to an endemic zone, its diagnosis is however difficult during relapses, notably when they are delayed.OBSERVATION:A 50 year-old man having lived in Mauritania from 1978 to 1982 was hospitalized for interstitial pneumopathy and urarthritis. In spite of treatment with broad spectrum antibiotics, the fever accompanied by abundant sweating persisted. A thick blood drop and blood smear was requested and led to the diagnosis of Plasmodium malariae malaria.DISCUSSION:This observation recalls the possibility of parasitic upsurge of some plasmodial species. It should prompt physicians to be careful and evoke malaria in the case of fever in subjects having stayed, even several years before, in an endemic zone. This would permit early diagnosis and treatment.