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Summary: Bluetongue virus (BTV) hitherto consisted of 26 recognized serotypes, of which all except BTV‐26 are primarily transmitted by certain species of Culicoides biting midges. Three variants of an additional 27th bluetongue virus serotype (BTV‐27v01‐v03) were recently detected in asymptomatic goats in Corsica, France, 2014–2015. Molecular characterization revealed genetic differences between the three variants. Therefore, in vivo characteristics were investigated by experimental infection of a total of 15 goats, 11 sheep and 4 cattle with any one of the three variants in separated animal trials. In goat trials, BTV‐naïve animals of the same species were kept in a facility where direct contact was unhindered. Of the 15 inoculated goats, 13 and 14 animals were found positive for BTV‐RNA and antibodies (Ab), respectively, until the end of the experiments. Surprisingly, BTV‐Ab levels as measured with ELISA and neutralization test (SNT) were remarkably low in all seropositive goats. Virus isolation from whole‐blood was possible at the peak of viremia until 49 dpi. Moreover, detection of BTV‐27v02‐RNA and Ab in one contact goat indicated that—similar to BTV‐26—at least one of three BTV‐27 variants may be transmitted by contact between goats. In the field, BTV‐27 RNA can be detected up to 6 months in the whole‐blood of BTV‐27‐infected Corsican goats. In contrast, BTV RNA was not detected in the blood of cattle or sheep. In addition, BTV‐27 Abs were not detected in cattle and only a transient increase in Ab levels was observed in some sheep. None of the 30 animals showed obvious BT‐like clinical signs. In summary, the phenotypes observed for BTV‐27v01‐v03 phenotypes correspond to a mixture of characteristics known for BTV‐25 and 26. [ABSTRACT FROM AUTHOR]

Summary: Undetected in Europe since 2010, bluetongue virus serotype 8 (BTV‐8) re‐emerged in August 2015 in Central France. To gain insight into the re‐emergence on the French territory, we estimated the seroprevalence in cattle before the detection of BTV‐8 in 2015, in areas differentially affected by the current outbreak. A retrospective survey based on the analysis of stored sera was thus conducted in the winter preceding the re‐emergence in seven French departments including the one where the virus was first detected. A total of 10,066 sera were retrieved from animals sampled in 444 different herds in winter 2014/15. Between‐herd seroprevalence revealed the presence of seropositive animals in almost all herds sampled (97.4%). The animal‐level seroprevalence averaged at 44%, with a strong age pattern reflecting the cumulative exposure to both natural infection and to vaccination. A multivariable analysis allowed separating the respective effects of both exposures. A higher proportion of seropositivity risk was attributed to vaccination (67.4%) than to exposure to natural infection (24.2%). The evolution of seroprevalence induced by the two main risk factors in 74 mainland departments was reconstructed between the vaccination ban (2013) and the re‐emergence (2015). We showed a striking decrease in seroprevalence with time after the vaccination ban, due to population renewal, which could have facilitated virus transmission leading to the current outbreak situation. [ABSTRACT FROM AUTHOR]

Summary: In November 2016, sheep located in the south of Corsica island exhibited clinical signs suggestive of bluetongue virus (BTV) infection. Laboratory analyses allowed to isolate and identify a BTV strain of serotype 4. The analysis of the full viral genome showed that all the 10 genomic segments were closely related to those of the BTV‐4 present in Hungary in 2014 and involved in a large BT outbreak in the Balkan Peninsula. These results together with epidemiological data suggest that BTV‐4 has been introduced to Corsica from Italy (Sardinia) where BTV‐4 outbreaks have been reported in autumn 2016. This is the first report of the introduction in Corsica of a BTV strain previously spreading in eastern Europe. [ABSTRACT FROM AUTHOR]

Summary: Bluetongue virus serotype 8 (BTV‐8) re‐emerged in Central France in August 2015. The viral strain identified is nearly identical to the one that circulated during the 2006/2009 massive outbreak throughout Europe. To address the question of an undetected BTV‐8 circulation on the French territory, a serological study was conducted on young cattle along a transect of seven departments, three of them located in areas where the virus presence had been confirmed by RT‐PCR by winter 2015/2016. Sera from 2,565 animals were collected during the winters preceding and following the re‐emergence, with 414 animals being sampled in each of the two consecutive years. All samples were tested by competitive ELISA (IDVet) and, when enough serum was available, ELISA‐positive samples were confirmed by seroneutralization tests. In areas with infected holdings, seropositive animals were found before the re‐emergence (N = 14 of 511), significantly more on the following year (N = 17 of 257), and eight animals (N = 158) seroconverted over 2015. Seropositive animals were also detected as early as winter 2014/2015 in one department without known infected holdings (N = 12 of 150), and in winter 2015/2016 in three of them (N = 21 of 555), where seven animals (N = 154) seroconverted over 2015. These results suggest that BTV‐8 may have spread at low levels before the re‐emergence, even in areas considered virus‐free. Unfortunately, whole blood from the seropositive animals was not available to definitely confirm the virus presence by RT‐PCR. [ABSTRACT FROM AUTHOR]

Bluetongue viruses ( BTV) are arboviruses responsible for infections in ruminants. The confirmation of BTV infections is based on rapid serological tests such as enzyme-linked immunosorbent assays ( ELISAs) using the BTV viral protein 7 ( VP7) as antigen. The determination of the BTV serotype by serological analyses could be only performed by neutralization tests ( VNT) which are time-consuming and require BSL3 facilities. VP2 protein is considered the major serotype-defining protein of BTV. To improve the serological characterization of BTV infections, the recombinant VP7 and BTV serotype 8 ( BTV-8) VP2 were synthesized using insect cells expression system. The purified antigens were covalently bound to fluorescent beads and then assayed with 822 characterized ruminant sera from BTV vaccinations or infections in a duplex microsphere immunoassay ( MIA). The revelation step of this serological duplex assay was performed with biotinylated antigens instead of antispecies conjugates to use it on different ruminant species. The results demonstrated that MIA detected the anti- VP7 antibodies with a high specificity as well as a competitive ELISA approved for BTV diagnosis, with a better efficiency for the early detection of the anti- VP7 antibodies. The VP2 MIA results showed that this technology is also an alternative to VNT for BTV diagnosis. Comparisons between the VP2 MIA and VNT results showed that VNT detects the anti- VP2 antibodies in an early stage and that the VP2 MIA is as specific as VNT. This novel immunoassay provides a platform for developing multiplex assays, in which the presence of antibodies against multiple BTV serotypes can be detected simultaneously. [ABSTRACT FROM AUTHOR]

At the end of August 2015, a ram located in central France (department of Allier) showed clinical signs suggestive of BTV (Bluetongue virus) infection. However, none of the other animals located in the herd showed any signs of the Bluetongue disease. Laboratory analyses identified the virus as BTV serotype 8. The viro and sero prevalence intraherd were 2.4% and 8.6% in sheep and 18.3% and 42.9% in cattle, respectively. Phylogenetic studies showed that the sequences of this strain are closely related to another BTV-8 strain that has circulated in France in 2006-2008. The origin of the outbreak is unclear but it may be assumed that the BTV-8 has probably circulated at very low prevalence (possibly in livestock or wildlife) since its first emergence in 2007-2008. [ABSTRACT FROM AUTHOR]

Since 2000, French Corsica Island has been exposed to the emergence of three different BT virus ( BTV) serotypes: serotype 2 in 2000 and 2001, serotype 4 in 2003 and serotype 16 in 2004. Between 2005 and August 2013, no outbreaks have been reported in the French Island. At the beginning of September 2013, sheep located in the south of the island showed clinical signs suggestive of BTV infection. Laboratory analyses identified the virus as BTV serotype 1. Phylogenetic studies showed that the sequences of this strain are closely related to the BTV-1 strain that was circulating in the Mediterranean basin and in Sardinia in 2012. [ABSTRACT FROM AUTHOR]