Asymptomatic Plasmodium vivax infections among Duffy-negative population in Kedougou, Senegal

International audienceBackground: In the southeastern Senegal, the report of Plasmodium vivax infections among febrile patients in Kedougou constitutes a new emerging health problem.Methods: Samples from 48 asymptomatic schoolchildren sampled twice a year over 2 years were used to explore the reservoir of P. vivax parasite infections in this region. Both Duffy genotyping and Plasmodium species diagnostic assays were performed.Results: PCR assays detected Plasmodium genomic DNA in 38.5% (74/192) of samples. Pure P. falciparum and P. vivax infections were identified in 79.7% (59/74) and 20.3% (15/74) of samples, respectively. All schoolchildren were classified as Duffy-negative by genotyping. P. vivax infections were detected in five children: in two children during both years, in one child in 2010 and on May 2011, and only in 2010 for the remaining two children.Conclusions: This unexpectedly high proportion of P. vivax infections in asymptomatic Duffy-negative children highlights to consider vivax malaria as an emerging problem in Senegal

Spatial distribution of overall incidence of confirmed clinical malaria episodes in the study area.

<p>Spatial distribution of overall incidence of confirmed clinical malaria episodes in the study area.</p

Map with the 8 villages involved in the study.

<p>Map with the 8 villages involved in the study.</p

Low genetic diversity and complexity of submicroscopic Plasmodium falciparum infections among febrile patients in low transmission areas in Senegal

International audienceWe examined rates of N 2 fixation from the surface to 2000 m depth in the Eastern Tropical South Pacific (ETSP) during El Niñ o (2010) and La Niñ a (2011). Replicated vertical profiles performed under oxygen-free conditions show that N 2 fixation takes place both in euphotic and aphotic waters, with rates reaching 155 to 509 mmol N m 22 d 21 in 2010 and 24614 to 118687 mmol N m 22 d 21 in 2011. In the aphotic layers, volumetric N 2 fixation rates were relatively low (,1.00 nmol N L 21 d 21), but when integrated over the whole aphotic layer, they accounted for 87-90% of total rates (euphotic+aphotic) for the two cruises. Phylogenetic studies performed in microcosms experiments confirm the presence of diazotrophs in the deep waters of the Oxygen Minimum Zone (OMZ), which were comprised of non-cyanobacterial diazotrophs affiliated with nifH clusters 1K (predominantly comprised of a-proteobacteria), 1G (predominantly comprised of c-proteobacteria), and 3 (sulfate reducing genera of the d-proteobacteria and Clostridium spp., Vibrio spp.). Organic and inorganic nutrient addition bioassays revealed that amino acids significantly stimulated N 2 fixation in the core of the OMZ at all stations tested and as did simple carbohydrates at stations located nearest the coast of Peru/Chile. The episodic supply of these substrates from upper layers are hypothesized to explain the observed variability of N 2 fixation in the ETSP

Year-specific incidence of confirmed clinical malaria episodes by village.

<p>Year-specific incidence of confirmed clinical malaria episodes by village.</p

Year-specific incidence of confirmed clinical malaria episodes.

<p>Year-specific incidence of confirmed clinical malaria episodes.</p

Malaria prevalence and malariometric indices among the randomly selected sample of 325 children, November 2010.

<p>IQR = interquartile range</p><p>Malaria prevalence and malariometric indices among the randomly selected sample of 325 children, November 2010.</p

One hundred malaria attacks since birth. A longitudinal study of African children and young adults exposed to high malaria transmissionResearch in context

Summary: Background: Despite significant progress in malaria control over the past twenty years, malaria remains a leading cause of child morbidity and mortality in Tropical Africa. As most patients do not consult any health facility much uncertainty persists about the true burden of the disease and the range of individual differences in susceptibility to malaria. Methods: Over a 25-years period, from 1990 to 2015, the inhabitants of Dielmo village, Senegal, an area of intense malaria transmission, have been monitored daily for their presence in the village and the occurrence of diseases. In case of fever thick blood films were systematically examined through microscopy for malaria parasites and patients received prompt diagnosis and treatment. Findings: We analysed data collected in 111 children and young adults monitored for at least 10 years (mean 17.3 years, maximum 25 years) enrolled either at birth (95 persons) or during the two first years of life. A total of 11,599 episodes of fever were documented, including 5268 malaria attacks. The maximum number of malaria attacks in a single person was 112. Three other persons suffered one hundred or more malaria attacks during follow-up. The minimum number of malaria attacks in a single person was 11. The mean numbers of malaria attacks in children reaching their 4th, 7th, and 10th birthdays were 23.0, 37.7, and 43.6 attacks since birth, respectively. Sixteen children (14.4%) suffered ten or more malaria attacks each year at ages 1–3 years, and six children (5.4%) each year at age 4–6 years. Interpretation: Long-term close monitoring shows that in highly endemic areas the malaria burden is higher than expected. Susceptibility to the disease may vary up to 10-fold, and for most children childhood is an endless history of malaria fever episodes. No other parasitic, bacterial or viral infection in human populations has such an impact on health. Funding: The Pasteur Institutes of Dakar and Paris, the Institut de Recherche pour le Développement, and the French Ministry of Cooperation provided funding