Biology subjects

Chastagner, A.

Publications and source records attributed to Chastagner, A..

3 recordsLinked to original sources

bioRxiv2025

Map simulator of tick abundance in heterogeneous agricultural landscapes

Among vector-borne diseases, tick-borne diseases (TBD) are a major concern for human health. Mapping the distribution of important tick species is thus a major challenge for efficient prevention. Due to its specific ecological requirements, Ixodes ricinus, the main tick species in Europe responsible for TBD transmission, lives mostly in woodlands but also at the interface between woodlands and pastures or crops and along hedgerows. At the landscape scale, extensive variations in tick densities are observed but remain poorly understood. In that aim, we built a statistical model to identify the landscape variables influencing the abundance of questing I. ricinus nymphs, using GLMM approaches and MCMC estimates. This model was fitted on a data set based on a field sampling of ticks conducted during 3 years in 2 different agricultural landscapes in northwest and southwest France, for a total of 5390 sampling units. Among 12 variables investigated, 4 were finally kept in the model: woodland perimeter, woodland distance, road distance and building perimeter. Then, we developed a R package that simulates the abundance of questing nymphs within a given agricultural landscape, taking into account the influence of the different habitats as determined by the above statistical model. The maps obtained as an output from this simulator will be a useful tool for visualizing TBD risk, notably for stake-holders involved in landscape management and public health decisions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=88 SRC="FIGDIR/small/663759v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@f950aborg.highwire.dtl.DTLVardef@1f0f27org.highwire.dtl.DTLVardef@11bde05org.highwire.dtl.DTLVardef@8d2202_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsIxodes ricinus abondance is influenced by landscape characteristics Tick sampling was carried out in heterogeneous agricultural landscapes Informative variables related to habitats were identified by statistical analysis Woodlands, roads and buildings influence tick densities The resulting model was used to build a simulator of tick at-risk zones

ecology↗

bioRxiv2024

Major change in swine influenza virus diversity in France owing to emergence and widespread dissemination of a newly introduced H1N2 1C genotype in 2020

Swine influenza A viruses (swIAV) are a major cause of respiratory disease in pigs worldwide, presenting significant economic and health risks. These viruses can reassort, creating new strains with varying pathogenicity and cross-species transmissibility. This study aimed to monitor the genetic and antigenic evolution of swIAV in France from 2019 to 2022. Molecular subtyping revealed a marked increase in H1avN2 cases from 2020 onwards, altering the previously stable subtypes distribution. Whole-genome sequencing and phylogenetic analyses of H1av (1C) strains identified ten circulating genotypes, including five new genotypes, marked by a significant predominance of the H1avN2#E genotype. It was characterized by an HA-1C.2.4, an N2-Gent/84, and internal protein-encoding genes belonging to a newly defined genogroup within the Eurasian avian-like (EA) lineage, the EA-DK subclade. H1avN2#E emerged in Brittany, the countrys most pig-dense region, and rapidly became the most frequently detected swIAV genotype across France. This drastic change in the swIAV lineages proportions at a national scale was unprecedented, making H1avN2#E a unique case for understanding swIAV evolution and spreading patterns. Phylogenetic analyses suggested an introduction of the H1avN2#E genotype from a restricted source, likely originating from Denmark. It spread rapidly with low genetic diversity at the start of the epizootic in 2020, showing increasing diversification in 2021 and 2022, and exhibiting reassortments with other enzootic genotypes. Amino acid sequence alignments of H1avN2#E antigenic sites revealed major mutations and deletions compared to vaccine 1C strain (HA-1C.2.2) and previously predominant H1avN1 strains (HA-1C.2.1). Antigenic cartography confirmed significant antigenic distances between H1avN2#E and other 1C strains, suggesting the new genotype escaped from the swine population preexisting immunity. Epidemiologically, the H1avN2#E virus exhibited epizootic hallmarks with more severe clinical outcomes compared to H1avN1 viruses. These factors likely contributed to the spread of H1avN2#E within the pig population. The rapid rise of H1avN2#E highlighted the dynamic nature of swIAV genetic and antigenic diversity, underscoring the importance of adapted surveillance programs to support risk assessment in the event of new outbreaks. This also demonstrate the need to strengthen biosecurity measures when receiving pigs in a herd and to limit trading of swIAV-excreting live swine between European countries.

evolutionary biology↗

bioRxiv2019

Relationships between landscape structure and the prevalence of two tick-borne infectious agents, Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato, in small mammal communities

ContextBy modifying ecosystems, land cover changes influence the emergence, the spread and the incidence of vector-borne diseases. ObjectiveThis study aimed at identifying associations between landscape structure and the prevalence of two tick-borne infectious agents, Anaplasma phagocytophilum and Borrelia burgdorferi s.l., in small mammal communities. MethodsSmall mammals were sampled in 24 sites along a gradient of woodland fragmentation and hedgerow network density, and screened for infectious agents with real-time PCR techniques. For each site, structural variables (composition and configuration) of the surrounding landscape at various scales (0-500 m) and variables of wooded habitats connectivity based on graph theory and least cost path distances for the two dominant species, bank voles (Myodes glareolus) and wood mice (Apodemus sylvaticus), were computed. ResultsThe A. phagocytophilum prevalence increased with wooded habitats cover (0-500 m), likely through host population size, and increased slightly with bank vole abundance, which has a higher reservoir competence than wood mouse. The B. burgdorferi s.l. prevalence increased with wooded ecotones only at local scales (50-100 m). Wooded habitats connectivity measures did not improve models built with simple land cover variables. A more marked spatial pattern was observed for the prevalence of A. phagocytophilum than B. burgdorferi s.l.. ConclusionsThis study highlights the interest of considering together the ecology of infectious agents (e.g. host specificity) and the host species community ecology to better understand the influence of the landscape structure on the spatial distribution of vector-borne infectious agents.

ecology↗