Phylogeography and Genetic Diversity of Francisella tularensis subsp. holarctica in France (1947-2018)

In France, tularemia is caused by Francisella tularensis subsp. holarctica and is a sporadic disease affecting mainly wildlife animals and humans. F. tularensis species presents low genetic diversity that remains poorly described in France, as only a few genomes of isolates from the country are available so far. The objective of this study was to characterize the genetic diversity of F. tularensis in France and describe the phylogenetic distribution of isolates through whole-genome sequencing and molecular typing. Whole genomes of 350 strains of human or animal origin, collected from 1947 to 2018 in France and neighboring countries, were sequenced. A preliminary classification using the established canonical single nucleotide polymorphism (canSNP) nomenclature was performed. All isolates from France (except four) belonged to clade B.44, previously described in Western Europe. To increase the resolution power, a whole-genome SNP analysis was carried out. We were able to accurately reconstruct the population structure according to the global phylogenetic framework, and highlight numerous novel subclades. Whole-genome SNP analysis identified 87 new canSNPs specific to these subclades, among which 82 belonged to clade B.44. Identifying genomic features that are specific to sublineages is highly relevant in epidemiology and public health. We highlighted a large number of clusters among a single clade (B.44), which shows for the first time some genetic diversity among F. tularensis isolates from France, and the star phylogeny observed in clade B.44-subclades revealed that F. tularensis biodiversity in the country is relatively recent and resulted from clonal expansion of a single population. No association between clades and hosts or clinical forms of the disease was detected, but spatiotemporal clusters were identified for the first time in France. This is consistent with the hypothesis of persistence of F. tularensis strains found in Western Europe in the environment, associated with slow replication rates. Moreover, the presence of identical genotypes across long periods of time, and across long distances, supports this hypothesis but also suggests long-distance dispersal of the bacterium.This work was supported by the French National Research Agency (ANR) and the Direction Générale de l’Armement (DGA) (No. ANR-15-ASTR-0021-01). MK is a Ph.D. student co-supported by Université Paris-Est and DGA grants

Tularemia : situation in france, issues and public health risk

This is a retrospective study on natural foci of tularemia in animals as well as human cases reported in France between 1999 and 2004. Since 1999, approximately 20 to 60 animals foci of infection in hares are detected every year in 19 to 34 French departments. Human cases often occur in areas where animal foci have erupted, but not always. There are several reasons explaining the presence of this disease on French territory, its underestimation in animals, and probably in man, and its durability. The disease is generally poorly recognised, except amongst shooters who are aware of its existence. Several clinical forms are known in man, sometimes with severe symptoms. The diagnosis of tularemia can be difficult due to its non-specific clinical features. Tularemia is mostly described in hares but other species can be also affected, serving as reservoirs for the infection and sometimes acting as vectors as well. The animal population tested for tularemia should be widened to include other wild species, as well as some of our domestic animals. In man, this diagnosis should be considered in people presenting certain clinical signs. A background on epidemiological data is given. In addition, as Francisella tularensis is one of the bioterrorism agents, it is essential that clinicians and biologists recognise this bacteria and are aware of its dangers. Tularemia was removed from the list of Legally Contagious Disease in veterinary medicine in 1996. It has become a notifiable disease in human medicine in 2002.Il s’agit d’une étude rétrospective de foyers animaux de la tularémie et des cas de contamination humaine recensés en France entre 1999 et 2004. Depuis 1999, environ 20 à 60 foyers sont identifiés chaque année chez des lièvres, dans 19 à 34 départements français. Les cas humains se déclarent souvent dans les régions où sont détectés les cas animaux, mais pas toujours. Plusieurs raisons sont à l’origine de la présence de la maladie sur le territoire, de sa sous-estimation chez les animaux, et vraisemblablement aussi chez l’homme, et de sa pérennité. La maladie est généralement mal connue, sauf chez les chasseurs qui en sont informés. Elle se présente sous de multiples formes chez l’homme et peut occasionner des troubles assez graves. Le diagnostic clinique peut être difficile, à cause des symptômes relativement peu spécifiques. Le lièvre n’est pas la seule espèce animale en cause, il n’est qu’un révélateur d’un foyer de la maladie. Plusieurs autres espèces y sont sensibles et constituent des réservoirs d’infection, certaines jouant également un rôle de vecteur. Il faudrait élargir la recherche de la tularémie à d’autres espèces de la faune sauvage, mais aussi à certaines espèces domestiques. Chez l’homme, cette maladie potentiellement grave devrait faire l’objet d’une recherche systématique face à certains symptômes cliniques. Plusieurs facteurs épidémiologiques sont rappelés. Par ailleurs, Francisella tularensis faisant partie des agents du bioterrorisme, il est essentiel que les cliniciens et les biologistes apprennent à reconnaître cette bactérie et exercent une certaine vigilance. La tularémie ne fait plus partie des Maladies Légalement Contagieuses en médecine vétérinaire depuis 1996. Elle est à déclaration obligatoire en santé humaine depuis 2002

Discriminating Francisella tularensis and Francisella-like endosymbionts in Dermacentor reticulatus ticks: Evaluation of current molecular techniques

International audienceFrancisella tularensis, the causative agent of tularemia, is commonly transmitted by ticks. To ensure accurate F. tularensis reporting rates in epidemiological surveys, specific discrimination between F. tularensis and Francisella-like tick endosymbionts (FLEs) is absolutely critical. Four molecular available techniques capable of distinguishing Francisella spp. were compared here for the first time in French Dermacentor reticulatus ticks in order to estimate their specificity as well as their ease and speed of use. Results showed that tul4 and fopA real-time PCR assays can easily and effectively discriminate between F. tularensis and FLEs in D. reticulatus. In addition, a high prevalence of FLEs in D. reticulatus collected in France was reported by the use of fopA real-time PCR assay (79%). Finally, phylogenetic analysis showed that FLEs isolated from D. reticulatus correspond to a well-defined group compared to FLEs originating from various tick species. (C) 2013 Elsevier B.V. All rights reserved

Spatio-temporal dynamics of tularemia in French wildlife: 2002–2013

International audienceTularemia, caused by Francisella tularensis, is endemic in France. The surveillance of this disease in wildlife is operated by the SAGIR Network and by the National Reference Laboratory for Tularemia. Wild animals found dead or dying collected by the SAGIR network are necropsied and when tularemia is suspected culture and/or PCR are performed to confirm the diagnosis. The aim of this study was to present the results of tularemia surveillance in wildlife and to investigate the spatial and temporal pattern of tularemia observed between the 2002-2003 and 2012-2013 hunting seasons in French wildlife. Fourty-one to 121 cases were collected each hunting season for a total of 693 confirmed cases and 46 additional suspected cases. The main species affected was the European Brown Hare (Lepus europaeus) but 4 rabbits (Oryctolagus cuniculus), 2 roe deer (Capreolus capreolus) and one wild boar (Sus scrofa) were also found positive. The Standard Mortality Ratio was mapped and Kulldorff's retrospective space-time scan statistic was implemented and allowed the detection of several clusters: the nationwide outbreak of 2007-2008; 2 clusters in northern and central-western France in high hare-abundance areas and another in Northeastern France where the abundance of hares is low. Our results confirm the usefulness of brown hare as a sentinel of environmental risk

Protective and therapeutic effect of DNA-based immunization against hepadnavirus large envelope protein

Background & Aims: Studies in the murine model suggest that injection of DNA encoding hepatitis B virus structural proteins is promising for the induction of a specific immune response. We used the duck hepatitis B virus (DHBV) model to study the protective and therapeutic effects of naked DNA immunization against hepadnaviral large envelope protein.Methods: A pCI-preS/S plasmid expressing the DHBV large protein was used for intramuscular immunization of ducks. The humoral response was tested by enzyme-linked immunosorbent assay, immunoblotting, neutralization, and in vivo protection tests. For DNA therapy, DHBV-carrier ducks received four injections of this plasmid. Viremia was monitored for 10 months; thereafter, liver biopsies were performed.Results: Immunization with pCI-preS/S plasmid induced a specific, long-lasting, neutralizing, and highly protective anti-preS humoral response in uninfected animals. After pCI-preS/S treatment, a significant and sustained decrease in serum and liver DHBV DNA was observed for carrier ducks compared with the controls.Conclusions: DNA immunization against DHBV large protein results in a potent and protective anti-preS response in the duck model. The results of long-term follow-up of DNA-treated chronically infected ducks are promising and show the usefulness of this model for the study of genetic immunization in chronic hepatitis B therapy

Maximum Lifetime Target Coverage in Wireless Sensor Networks

International audienceThe challenge in the deployment of wireless sensor networks is to ensure the coverage of targets with high energy efficiency, particularly when coverage constraint and energy constraint must be taken into account. Many algorithms have been suggested over the years to enhance network lifetime as sensor nodes are powered by batteries. These algorithms divide a set of sensor nodes into a number of subsets which can monitor all targets. The subsets are either joint or disjoint. In this paper, we propose an efficient method to compute the maximum lifetime target coverage. Our proposed method is centered around a target that is covered by a minimum number of sensor nodes. Based on this approach, we also propose an algorithm to expand the network lifetime which guarantees the monitoring of all targets by forming subsets of sensor nodes. Our obtained results are compared with the work reported in [1]. They are also compared with a method of computing the maximum lifetime target coverage (MLTC). The results obtained by simulation show that the proposed algorithm enhances the network lifetime, which illustrates the efficiency of this algorithm

High-resolution melting PCR assay as a powerful tool for the epidemiological surveillance of tularemia in Western Europe

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Comparison of French and Worldwide <i>Bacillus anthracis</i> Strains Favors a Recent, Post-Columbian Origin of the Predominant North-American Clade

<div><p>Background</p><p><i>Bacillus anthracis</i>, the highly dangerous zoonotic bacterial pathogen species is currently composed of three genetic groups, called A, B and C. Group A is represented worldwide whereas group B is present essentially in Western Europe and Southern Africa. Only three strains from group C have been reported. This knowledge is derived from the genotyping of more than 2000 strains collected worldwide. Strains from both group A and group B are present in France. Previous investigations showed that the majority of sporadic French strains belong to the so-called A.Br.011/009 group A clade and define a very remarkable polytomy with six branches. Here we explore the significance of this polytomy by comparing the French <i>B</i>. <i>anthracis</i> lineages to worldwide lineages. We take advantage of whole genome sequence data previously determined for 122 French strains and 45 strains of various origins.</p><p>Results</p><p>A total of 6690 SNPs was identified among the available dataset and used to draw the phylogeny. The phylogeny of the French B group strains which belongs to B.Br.CNEVA indicates an expansion from the south-east part of France (the Alps) towards the south-west (Massif-Central and Pyrenees). The relatively small group A strains belonging to A.Br.001/002 results from at least two independent introductions. Strikingly, the data clearly demonstrates that the currently predominant <i>B</i>. <i>anthracis</i> lineage in North America, called WNA for Western North American, is derived from one branch of the A.Br.011/009 polytomy predominant in France.</p><p>Conclusions/Significance</p><p>The present work extends the range of observed substitution rate heterogeneity within <i>B</i>. <i>anthracis</i>, in agreement with its ecology and in contrast with some other pathogens. The population structure of the six branches A.Br.011/009 polytomy identified in France, diversity of branch length, and comparison with the WNA lineage, suggests that WNA is of post-Columbian and west European origin, with France as a likely source. Furthermore, it is tempting to speculate that the polytomy’s most recent common ancestor -MRCA- dates back to the Hundred Years' war between France and England started in the mid-fourteenth century. These events were associated in France with deadly epidemics and major economic and social changes.</p></div