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International audience; Epizootic haemorrhagic disease virus (EHDV) was detected for the first time in Tunisia and in other Northern African countries in 2006.The objective of the present study was to investigate whether EHDV circulated in Tunisian livestock beforeand after the officially-reported outbreak of 2006.Thus, serum samples from cattle and dromedaries collected in different time periods (before and after 2006) and from different regions of Tunisia were screened for the presence of EHDV antibodies. Serological investigations conducted on cattle and dromedary sera collected in 2000 and 2001 demonstrated no virus circulation on these dates. However, viral circulation was evidenced in 2012 and 2013, although no EHDV cases were officially reported in these years. Serum-neutralization assessed on few ELISA positive samples, confirmed the presence of antibodies against EHDV serotype 6, which was the serotype involved in the EHDV outbreak in the Maghreb region in 2006.

Depuis 2014, de nombreux foyers de fièvre catarrhale ovine (FCO) sont déclarés en Europe chaque année, principalement de sérotype 4, mais aussi de sérotype 1 (Italie, Croatie, Espagne, Portugal) et de sérotype 8 (France, Chypre, Suisse). On observe une diminution du nombre de foyers de FCO-1 depuis 2014, ainsi qu'une augmentation du nombre de foyers de FCO-4 et, depuis 2015, de FCO-8. L'année 2017 a été marquée par une importante épizootie de sérotype 4 qui a frappé la Sardaigne et la Corse de fin juin à décembre 2017 et l'introduction de ce sérotype 4 en France continentale. Le sérotype 2 a été identifié en Italie en 2014, le sérotype 3 a été détecté pour la première fois en Europe en Sicile en 2017, et le sérotype 16 a été signalé à Chypre en 2014, puis en Grèce et en Turquie à partir de septembre 2017. La situation épidémiologique de la FCO en Europe est donc complexe et le maintien d'un niveau de vigilance élevé est nécessaire car le changement climatique, l'évolution des aires de distribution des insectes vecteurs et les mouvements d'animaux constituent des facteurs de risque d'introduction de nouveaux sérotypes en Europe.

Viruses have the largest diversity of genome architectures. Among them, segmented viruses possess a genome divided in several chromosomes or segments, encapsidated together. The most prevalent hypothesis to expia in the evolution of this genome organisation is an increased ability for genetic exchanges. Recently a hypothesis has suggested that this genome organisation could have evolved to favour the regulation of gene copy number and thus gene expression at the population level. ln an infected host, a viral population is composed of different genotypes, including defective genotypes lacking specific segments. Under this new hypothesis, the segment copy number in the population differs among segments, and consequently among the genes they bear. This situation would lead to a differential expression of viral genes at the host level, influencing phenotype. Our study aims to test whether variations in segment copy number exist in populations of Bluetongue virus, whose genome harbour a segment number among the highest described. Bluetongue virus follows a complex life cycle involving compulsory alternation between insect vectors and ruminants. This virus could thus use different segment copy numbers to differentially regulate gene expression in its highly unrelated hasts. To test our hypothesis, we designed a QPCR assay for each of the 10 genomic segments in order to monitor quantitative variations in different hosts. We first isolated a BTV genotype (BTV4 serotype) from sheeps infected in Corsica in 2017. This isolate was used to infect two different cell lines, a mammalian line (VERO) and an insect cell line (KC). Gene copy number variation in segmented genome virus could be a key mechanism underlying their high adaptive capacity and supporting an alternative way of adaptation to host alternation. This study is a prelude to Bluetongue virus gene copy number variation monitoring with time, space and environmental variations.

Schmallenberg virus (SBV) was discovered in Germany in late 2011 and then spread rapidly to many European countries. SBV is an orthobunyavirus that causes abortion and congenital abnormalities in ruminants. A virus-encoded nonstructural protein, termed NSs, is a major virulence factor of SBV, and it is known to promote the degradation of Rpb1, a subunit of the RNA polymerase II (Pol II) complex, and therefore hampers global cellular transcription. In this study, we found that NSs is mainly localized in the nucleus of infected cells and specifically appears to target the nucleolus through a nucleolar localization signal (NoLS) localized between residues 33 and 51 of the protein. NSs colocalizes with nucleolar markers such as B23 (nucleophosmin) and fibrillarin. We observed that in SBV-infected cells, B23 undergoes a nucleolus-to-nucleoplasm redistribution, evocative of virus-induced nucleolar disruption. In contrast, the nucleolar pattern of B23 was unchanged upon infection with an SBV recombinant mutant with NSs lacking the NoLS motif (SBVΔNoLS). Interestingly, unlike wild-type SBV, the inhibitory activity of SBVΔNoLS toward RNA Pol II transcription is impaired. Overall, our results suggest that a putative link exists between NSs-induced nucleolar disruption and its inhibitory function on cellular transcription, which consequently precludes the cellular antiviral response and/or induces cell death.

Genetic exchange by a process of genome-segment ‘reassortment’ represents an important mechanism for evolutionary change in all viruses with segmented genomes, yet in many cases a detailed understanding of its frequency and biological consequences is lacking. We provide a comprehensive assessment of reassortment in bluetongue virus (BTV), a globally important insect-borne pathogen of livestock, during recent outbreaks in Europe. Full-genome sequences were generated and analysed for over 150 isolates belonging to the different BTV serotypes that have emerged in the region over the last 5 decades. Based on this novel dataset we confirm that reassortment is a frequent process that plays an important and on-going role in evolution of the virus. We found evidence for reassortment in all ten segments without a significant bias towards any particular segment. However, we observed biases in the relative frequency at which particular segments were associated with each other during reassortment. This points to selective constraints possibly caused by functional relationships between individual proteins or genome segments and genome-wide epistatic interactions. Sites under positive selection were more likely to undergo amino acid changes in newly reassorted viruses, providing additional evidence for adaptive dynamics as a consequence of reassortment. We show that the live attenuated vaccines recently used in Europe have repeatedly reassorted with field strains, contributing to their genotypic, and potentially phenotypic, variability. The high degree of plasticity seen in the BTV genome in terms of segment origin suggests that current classification schemes that are based primarily on serotype, which is determined by only a single genome segment, are inadequate. Our work highlights the need for a better understanding of the mechanisms and epidemiological consequences of reassortment in BTV, as well as other segmented RNA viruses., Author Summary Segmented viruses have genomes that are separated into multiple segments, comparable to chromosomes in higher organisms. When two segmented viruses of the same species infect the same cell, their progeny may incorporate segments picked up from the “parental” viruses. This process is called “reassortment” and represents an important way for segmented viruses to evolve. Whereas reassortment has received a lot of attention in certain segmented viruses, especially influenza A, its frequency and biological consequences remain poorly understood for most of the others. Here, we present a comprehensive analysis of the reassortment patterns in bluetongue virus, an important pathogen of livestock, during its repeated emergence in Europe in recent decades. We confirm earlier reports that reassortment is common and can involve segments derived from live vaccines used to control outbreaks. However, the mixing of viral genomes is not strictly random and reassortment is commonly followed by novel adaptive changes in the progeny virus. This points to important functional links (paired associations) between certain segments. Our findings have important implications for the classification and control of segmented viruses and generate new insights and hypotheses about the biological interactions among different parts of the bluetongue virus genome.

International audience; Since 1998, Bluetongue virus (BTV) serotypes 1, 2, 4, 6, 8, 9, 11 and 16 have spread throughout Europe. In 2006, BTV serotype 8 (BTV-8) emerged unexpectedly in Northern Europe, in countries such as Belgium, France, Germany, Luxembourg, and the Netherlands, to spread rapidly in the following year throughout the rest of Europe. In 2007, BTV-1 spread in Southern Europe, in Spain and in South of France. In 2008, 2 more BTV serotypes were detected in Northern Europe: BTV-6 in the Netherlands and in Germany, and BTV-11 in Belgium. The European incursion of BTV has caused considerable economic losses, including direct losses from mortality and reduced production, as well as indirect losses generated by ensuing bans on trade of ruminants between infected and non-infected areas. Given the significance of the disease, all affected countries have established control and eradication measures that have evolved together with the availability of detection and prevention tools such as Polymerase Chain Reaction (PCR) tests and vaccines, respectively. This paper describes how the French National Reference Laboratory for BT has managed diagnosis during the fast and massive spread of BTV-1 and 8 in 2007 and 2008.

L'année 2014 a été caractérisée par une situation épidémiologique nouvelle vis-à-vis de la fièvre catarrhale ovine (FCO) en Europe. Suite à la première notification de foyers de sérotype 4 (BTV-4) en Grèce dans la région du Péloponnèse (mai 2014), onze pays de la région des Balkans ont été touchés par l'épizootie de BTV-4 avec un total de 6 485 foyers déclarés. Fin novembre 2014, en Italie, 25 foyers dus au BTV-4 avaient été confirmés. Une diffusion du virus BTV-1 a de plus été observée dans la partie continentale du pays. En Espagne, les premières suspicions impliquant une souche différente de BTV-4 ont été déclarées en septembre 2014. Aucun lien épidémiologique n'existe cependant avec l'épizootie dans les Balkans. Début décembre, 351 foyers avaient été déclarés en Espagne en dehors de la zone de restriction pour le BTV-4. Par ailleurs, sept foyers de BTV-1 ont été déclarés dans le sud du pays. Au vu des stratégies de lutte appliquées par les pays touchés, il ne fait aucun doute que la vaccination de masse reste le seul moyen réellement efficace de lutte contre la FCO. Les traitements insecticides des animaux permettent au mieux de limiter la transmission et ralentir la diffusion, sans la stopper.