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The variation in viral gene frequencies remains a largely unexplored aspect of within-host genetics. This phenomenon is often considered to be specific to multipartite viruses. Multipartite viruses have segmented genomes, but in contrast to segmented viruses, their segments are each encapsidated alone in a virion. A main hypothesis explaining the evolution of multipartism is that, compared to segmented viruses, it facilitates the regulation of segment abundancy, and the genes the segments carry, within a host. These differences in gene frequencies could allow for expression regulation. Here, we show that wild populations of a segmented virus, bluetongue virus (BTV), also present unequal segment frequencies. BTV cycles between ruminants and Culicoides biting midges. As expected from a role in expression regulation, segment frequencies tended to show specific values that differed between ruminants and midges. Our results expand previous knowledge on gene frequency variation and call for studies on its role and conservation beyond multipartite viruses., Genome segmentation is mainly thought to facilitate reassortment. Here, we show that segmentation can also allow differences in segment abundance in populations of bluetongue virus (BTV). BTV has a genome consisting in 10 segments, and its cycle primarily involves periodic alternation between ruminants and Culicoides biting midges. We have developed a reverse transcription-quantitative PCR (RT-qPCR) approach to quantify each segment in wild BTV populations sampled in both ruminants and midges during an epizootic. Segment frequencies deviated from equimolarity in all hosts. Interestingly, segment frequencies were reproducible and distinct between ruminants and biting midges. Beyond a putative regulatory role in virus expression, this phenomenon could lead to different evolution rates between segments. IMPORTANCE The variation in viral gene frequencies remains a largely unexplored aspect of within-host genetics. This phenomenon is often considered to be specific to multipartite viruses. Multipartite viruses have segmented genomes, but in contrast to segmented viruses, their segments are each encapsidated alone in a virion. A main hypothesis explaining the evolution of multipartism is that, compared to segmented viruses, it facilitates the regulation of segment abundancy, and the genes the segments carry, within a host. These differences in gene frequencies could allow for expression regulation. Here, we show that wild populations of a segmented virus, bluetongue virus (BTV), also present unequal segment frequencies. BTV cycles between ruminants and Culicoides biting midges. As expected from a role in expression regulation, segment frequencies tended to show specific values that differed between ruminants and midges. Our results expand previous knowledge on gene frequency variation and call for studies on its role and conservation beyond multipartite viruses.

International audience; This report provides the first clinical, radiographic, echocardiographic, and biological description of SARS-CoV-2-associated myocarditis with a 6-month follow-up in a 5-year-old obese male domestic shorthair cat (Cat-1) presented for refractory congestive heart failure, with high cardiac troponin-I level (5.24 ng/ml), and a large lingual ulcer. The animal was SARS-CoV-2 positive on serology. The other cat living in the same household (Cat-2) never showed any clinical sign but was also confirmed SARS-CoV-2 positive on serology. Both cats were SARS-CoV-2 PCR negative. Cat-1 had closer contact than Cat-2 with their owner, who had been in close contact with a coworker tested PCR positive for COVID-19 (Alpha (B.1.1.7) variant) 4 weeks before Cat-1's first episode of congestive heart failure. A focused point-of-care echocardiography at presentation revealed for Cat-1 numerous B-lines, pleural effusion, severe left atrial dilation and dysfunction, and hypertrophic cardiomyopathy phenotype associated with focal pulmonary consolidations. Both myocarditis and pneumonia were suspected, leading to the prescription of cardiac medications and antibiotics. One month later, Cat-1 recovered, with normalization of left atrial size and function, and radiographic and echocardiography disappearance of heart failure signs and pulmonary lesions. An extensive literature review of SARS-CoV-2-related cardiac injury in pets in comparison with human pathology is discussed.

© 2020 Pascall et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The mechanisms underlying virus emergence are rarely well understood, making the appearance of outbreaks largely unpredictable. Bluetongue virus serotype 8 (BTV-8), an arthropod-borne virus of ruminants, emerged in livestock in northern Europe in 2006, spreading to most European countries by 2009 and causing losses of billions of euros. Although the outbreak was successfully controlled through vaccination by early 2010, puzzlingly, a closely related BTV-8 strain re-emerged in France in 2015, triggering a second outbreak that is still ongoing. The origin of this virus and the mechanisms underlying its re-emergence are unknown. Here, we performed phylogenetic analyses of 164 whole BTV-8 genomes sampled throughout the two outbreaks. We demonstrate consistent clock-like virus evolution during both epizootics but found negligible evolutionary change between them. We estimate that the ancestor of the second outbreak dates from the height of the first outbreak in 2008. This implies that the virus had not been replicating for multiple years prior to its re-emergence in 2015. Given the absence of any known natural mechanism that could explain BTV-8 persistence over this long period without replication, we hypothesise that the second outbreak could have been initiated by accidental exposure of livestock to frozen material contaminated with virus from approximately 2008. Our work highlights new targets for pathogen surveillance programmes in livestock and illustrates the power of genomic epidemiology to identify pathways of infectious disease emergence.

The aim of this study was to produce reference sera against the seven serotypes of Epizootic hemorrhagic disease virus (EHDV‑1, EHDV‑2, EHDV‑4, EHDV‑5, EHDV‑6, EHDV‑7, and EHDV‑8). In a high containment unit, seven Prim 'Holstein calves were inoculated at day 0 (D0) with the selected strains (1 EHDV serotype per calf ). Blood samples (EDTA and whole blood) were periodically taken from D0 until the end of the experiment (D31). Sera were tested with two commercially available EHDV competitive ELISAs (c‑ELISA). Viral genome was detected from EDTA blood samples using in‑house real‑time RT‑PCR. Sera taken on D31 post infection (pi) were tested and characterized by serum neutralization test (SNT) and virus neutralization test (VNT) (for calibration of reference sera). Viral RNA was first detected at D2 pi in five calves. All infected animals were RT‑PCR positive at D7 pi. Seroconversion was observed between D10 and D23 pi depending on the EHDV serotype. SNT and VNT have allowed to determine the neutralizing antibody titers of each serum and the potential cross‑reactions between serotypes. The two c‑ELISA used in this study showed similar results. The calibrated sera are now available for the serological identification of an EHDV isolated on tissue culture or to be used as positive control in seroneutralization assay.

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.

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.

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.

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.

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.

International audience; Bluetongue and other animal diseases caused by Orbivirus remain a priority and sometimes an emergency for the Veterinary Services and the livestock industry. In order to guarantee a fre trade of animals and related products, the World Organization for Animal Health (OIE) and the World Bank (WB) included these diseases among those that may need more attention and investments by enhancing food safety.

Objective: Bluetongue (BT) and epizootic haemorrhagic disease (EHD) are arthropod-borne diseases of wild and domestic ruminants caused respectively by viruses belonging to the species Bluetongue virus (BTV) and Epizootic haemorrhagic disease virus (EHDV) within the genus Orbivirus of the Reoviridae. The viruses are transmitted between ruminants by biting midges of the genus Culicoides (Diptera: Ceratopogonidae). BTV went undetected in Reunion Island between its first documented emergence in 1979 and two other serious outbreaks with both BTV-3/ EHDV-6 in 2003, and both BTV-2/EHDV-6 in 2009. In these outbreaks, infected animals developed symptoms including hyperthermia, anorexia, congestion, prostration and nasal discharge. In order to get an overview of the circulation of BT/EHD in Reunion island, an assessment of the prevalence in ruminants native to Reunion Island by a cross-sectional study was undertaken in2011on 67 farms, including a total of 276 cattle, 142 sheep and 71 goats with a total of 489 ruminant samples. Data concerning farm characteristics, type of production, and number of animals were collected through farmer questionnaires for an evaluation of the associated risk factors. In addition, investigation of clinical cases based on the observation of clinical signs was also performed in order to get BTV/EHDV isolates with the aim to track the origins of the circulating strains. Methods: Risk factors analysis Data concerning farm characteristics, type of production, number of animals, closeness to another farm and sugar cane fields, presence of organic and other waste on the farm, exposure to wind, distance to a permanent water point, type of animal housing, presence of ticks on animals, use of treatment against ectoparasites and insects, animal's contacts with other animals or humans, grazing practice, spreading of manure on pastures, presence of Tenrece caudatus, rodent control, number of abortions in the herd in the last 12 months, purchasing behaviour, quarantine of newly purchased animals, other biosecurity factors like hygienic precautions taken by the staff or other people entering the farm (truck driver, vets and other visitors) were taken from a questionnaire which was filled in during an interview with the farmers. This questionnaire was pre-tested on five farms in a preliminary study. The final questionnaire comprised 40 questions of which 75% were closed-ended. Serological assays Specific anti-BTV antibodies were tested in serum samples with a group-specific competitive ELISA based on the VP7 protein using a commercial kit (LSIVetTM Ruminant BT Advanced II- Serum, Life technologies, France). Specific anti-EHDV antibodies were tested using a blocking commercial kit (LSIVetTM Ruminant EHDV-Serum ELISA kit, Life technologies, France). A Sunrise ELISA reader was used for reading at 450 nm (Tecan, France). Optical density values were converted to percentage inhibition (PI). According to the cut-off value of the test, test samples with PI values > 40% for BT and > 60% for EHD were considered as positive. BTV/EHDV genome detection For the BTV group specific real-time RT-PCR, 6 μl of denatured double-stranded RNA prepared with the EZ1 robot and EZ1® Virus Mini Kit v2.0 (Qiagen, France) were reverse transcribed (RT) and amplified using the onestep QuantiTect Probe RT-PCRkit (Qiagen, France) based on segment 1 developed by Toussaint et al. 2007. For the EHDV group specific real-time RT-PCR, 5 μl of denatured double-stranded RNA were reverse transcribed (RT) and amplified using the commercial TaqVetTM EHDV (Life technologies, France).The subgroup-specific EHDV RTPCR based on segment 2 was performed according to Sailleau et al., 2012.Embryonated chicken eggs (ECE) were each inoculated as previously described in Sailleau et al., 2012 Sequence analysis, alignment and phylogenetic analysis To identify the genetic relatedness of the detected virus, phylogenetic analyses were performed with published EHDV sequences. Sixteen full-length VP2 gene sequences were cleaned by hand from the results of several BLAST nucleotide searches as well as direct references from available up-to-date literature and then aligned using the ClustalW translation alignment tool in MEGA (Ver. 5.05). Phylogenetic analysis was performed using the neighbour-joining method using distance measures generated by the p-distance algorithm running 1, 000 iterations with Geneious® Pro. Statistics A Fisher exact test was used to compare differences in prevalence between diseases and species. All statistical procedures were performed using R.3.0.1. A value of P < 0.05 was considered significant. The prevalence rates were estimated as the overall mean and 95% confidence interval (CI). Results: The observed EHD prevalence rate in cattle was 63.77% (95% CI [57.99–69.55]), 5.63% (95% CI [0.03–10.99]) in goats, and 3.70% (95% CI [0.05–6.88]) in sheep, suggesting that EHD occurs more often in cattle than in goats and sheep. These findings were supported by a significant statistical difference in the EHD prevalence rate between species (Fisher exact test, P <

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Le 2 septembre 2013, des signes cliniques évocateurs de fièvre catarrhale ovine (FCO) ont été observés dans deux élevages ovins en Corse. Les analyses du laboratoire national de référence en virologie pour la FCO ont confirmé la présence du sérotype 1 du virus de la FCO. L'épizootie s'est ensuite propagée à l'ensemble de l'île. Au 12 novembre 2013, plus de 120 élevages, essentiellement ovins, étaient déclarés infectés. L'impact de la maladie dans ces élevages a été très variable. La localisation des premiers foyers dans le sud de l'île et le séquençage du virus suggèrent que le virus a été introduit depuis la Sardaigne. Pour lutter contre cette épizootie, l'État a mis en place une campagne de vaccination obligatoire de l'ensemble de la population ovine, caprine et bovine de l'île.

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Since 2002, the livestock of Réunion Island has been subject to reoccurring outbreaks of Bluetongue (BT) and Epizootic Hemorrhage Disease (EHD). To find out a solution to this problem, that can have severe financial implications to ruminant farmers, a study was carried out between March and September of 2011. The aims of this study were: (1) to confirm the circulation of the viral agents in relation to both host reservoirs and insect vectors; (2) to assess the health status of Réunion Island's livestock; and (3) to identify major risk factors pertaining to ruminant farming due to these viruses. A total of 254 cows from 51 farms and 206 sheep and goats were chosen randomly for testing. Multiple blood samples were taken from all sampled animals. Farming procedures and environmental conditions were assessed for each farm via a questionnaire. Any animal exhibiting clinical symptoms of viral infection was also tested. Serology was done using commercially available LSIVET kits, viral detection was performed via RT-PCR and genotyping was performed externally. Logistic regression was used to assess potential risk factors after a fist of univariate analysis (Chi2). Serology studies suggested that ~50% of ruminants were positive for Bluetongue and ~40% for EHD. EHDV-1 virus was detected in ~5% of animals and bluetongue variant 2 was detected in ~1%. Statistical analysis showed that the major risk factors for Bluetongue and EHD viral infection of ruminant livestock include; the category of the reared livestock, the presence of organic waste, the presence of a water source and the proximity of another farm. Those results are the first step to a better understanding of what could happen in the futur in Western Europe. (Texte intégral)

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Outre sa parenté lointaine avec le virus de la fièvre de la vallée du Rift et sa proximité avec le virus Akabane, le nouveau virus Schmallenberg présente pour certains segments une grande proximité génétique avec un virus encore peu renseigné : le Shamonda (Nigeria, 1965). Fin janvier 2012, des foyers largement dispersés ont été confirmés dans un premier temps en Allemagne, puis aux Pays-Bas et en Belgique, pour être enfin identifié en France le 25 janvier 2012, d’abord exclusivement chez des ovins.Face à un agneau, veau ou chevreau, fœtus ou nouveau-né présentant des malformations, des prélèvements de cerveau et de sang sont à adresser au laboratoire départemental, qui les transmet au Laboratoire de santé animale de Maisons-Alfort (UMR de virologie), seul susceptible actuellement de procéder au diagnostic direct par RT-PCR.

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Le virus dela maladiehémorragiqueépizootique (epizootichemorrhagic disease,ou eHd) des cervidésconstitue unemenace sérieusepour le cheptelbovin européen.; Le virus dela maladiehémorragiqueépizootique (epizootichemorrhagic disease,ou eHd) des cervidésconstitue unemenace sérieusepour le cheptelbovin européen.La structure etles propriétésbiologiques duvirus de l’eHd etses manifestationscliniques sontdécrites. Lesespèces susceptiblesd’être réceptivesou sensibles àl’infection sont aussiindiquées, ainsique la distributiongéographiquemondiale du virus,la nature et lescaractéristiquesbiologiques desinsectes vecteurset les risquesd’introduction de cetagent pathogène. sicelui-ci émergeaiten europe, lesautorités vétérinairesseraient confrontéesaux mêmesdiffi cultés que cellesrencontrées pourle virus de la fi èvrecatarrhale ovineet les praticiensforment le premier“rempart” face àcette menace.

La Guadeloupe et la Réunion sont deux départements d'Outre-mer dans lesquels la fièvre catarrhale ovine est enzootique. Depuis 2010, il a été démontré qu'une autre arbovirose transmise par des Culicoides, la maladie épizootique hémorragique des cervidés est aussi présente dans ces îles. Cet article présente les particularités de l'épidémiologie de ces maladies en distinguant les quatre déterminants principaux de l'épidémiologie des maladies vectorielles : animaux/environnement/espèces vectrices de Culicoides/virus. Ces comparaisons montrent la pertinence de la notion de "pathosystème" qui illustre les différences observées pour une même maladie dans des contextes épidémiologiques différents.

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National audience; This paper describes the spread of two arboviral diseases in Europe, and the control measures implemented by health authorities. Bluetongue, which affects only animals, occurred for the first time in Europe in 1998, and West Nile Fever, which affects horses and humans, re-emerged in 1996. Up until 1998, bluetongue was considered as an exotic disease. In 2006 and 2007, its unexpected explosion in Northern Europe highlighted the emergence and expansion capacities of vector-borne diseases. Surprisingly, the disease became perennial in Europe, rapidly spreading to eight European countries and crossing the English Channel and contaminating several herds in England. Its expansion resulted from vector movements carried over long distances by the wind (100 km), and followed a centrifugal pattern in 2006/2007. By 2008, the bluetongue virus (BTV) was occupying a wider European territory. The only control measure available is vaccination, which has been largely implemented in 2008. West Nile fever is a viral disease transmitted by mosquitoes, whose amplifying hosts are birds, whereas horses and humans are incidental but particularly sensitive hosts. West Nile fever appeared in Europe in the 60’s and 70’s, especially in the Camargue region of France, with sporadic foci. At the end of the 90’s, besides the introduction and expansion of the virus on the American continent, major epidemics affected several hundreds of people in Europe (Romania in 1996 and Russia in 1999). Since then, four distinct episodes of West Nile virus (WNV) circulation, associated with clinical cases in horses, were reported in France: in the Camargue region in 2000 and 2004, in the Var department in 2003 and in the Eastern Pyrenees in 2006. An increase in WNV activity was observed in Europe in 2008, with cases of infection reported in Italy, Romania, Hungary and Austria. An inactivated vaccine (Fort Dodge) has recently received a marketing agreement from the European commission. However, until now, control measures rely exclusively on a reinforced surveillance of neurological conditions in humans and animals (horses and birds generally), and on information of exposed people.; Cet article décrit l’extension de deux arboviroses en Europe ainsi que les mesures de lutte mises en oeuvre par les autorités sanitaires. La fièvre catarrhale ovine (FCO), strictement animale, est apparue pour la première fois en Europe en 1998, tandis que la fièvre du Nil occidental, transmissible à l’homme, a ré-émergé en 1996. Jusqu’en 1998, la FCO était considérée comme une maladie exotique. En 2006 et 2007, son explosion inattendue dans le nord de l’Europe a fourni un éclairage nouveau sur les capacités d’émergence et d’extension des maladies vectorielles. De façon surprenante, la maladie s’est installée de façon pérenne en Europe gagnant rapidement huit pays européens et traversant la Manche pour contaminer plusieurs élevages en Angleterre. Son extension résulte du déplacement du vecteur porté par le vent sur de grandes distances (100 km), et a donc été centrifuge en 2006/7. L’année 2008 confirme cette extension et l’installation du virus sur un territoire européen élargi. La seule méthode de lutte est la vaccination mise en oeuvre de façon massive en 2008. La fièvre du Nil occidental, ou West Nile Fever, est une virose transmise par les moustiques dont les hôtes amplificateurs sont les oiseaux, tandis que le cheval et l’homme sont des hôtes accidentels particulièrement sensibles. Elle était apparue en Europe dans les années 1960-1970 et, en particulier, en France métropolitaine dans la région de la Camargue, en des foyers sporadiques. À la fin des années 1990, outre l’introduction et la progression du virus sur le continent américain, des épidémies importantes ont touché plusieurs centaines de personnes en Europe (Roumanie en 1996, Russie en 1999). Puis, quatre épisodes distincts de circulation du virus West Nile (VWN), associés à des cas cliniques chez le cheval, ont été décrits en France : en Camargue, en 2000 et 2004, dans le Var en 2003 et dans les Pyrénées-Orientales en 2006. Un regain de l’activité du virus a été observé en 2008 en Europe, l’Italie, la Roumanie, la Hongrie et l’Autriche ayant rapporté des cas d’infection par le VWN. Un vaccin inactivé (Fort Dodge) a récemment obtenu une AMM européenne. Cependant, jusqu’ici, les méthodes de lutte s’appuient jusqu’ci sur la surveillance renforcée des affections nerveuses chez l’homme et l’animal (chevaux et oiseaux généralement) et sur l’information des personnes exposées.

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