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Bluetongue (BT) and epizootic haemorrhagic disease (EHD) are vector‐borne viral diseases affecting domestic and wild ruminants. Both are notifiable under OIE rules. BT and EHD viruses (BTV and EHDV) are closely related Orbiviruses with structural, antigenic and molecular similarities. Both viruses can produce analogous clinical signs in susceptible animals. Serological tests are commonly used for BT and EHD diagnosis and surveillance. Competitive ELISA (c‐ELISA) is the most widely used serological test for the specific detection of BTV or EHDV viral protein 7 (VP7) antibodies (Abs). The specificity and sensitivity of the BTV c‐ELISA kits available on the market are recognized for the detection of BTV Abs. Concerning EHD, a single commercial EHDV c‐ELISA kit (ELISA A kit) commonly used for diagnosis in Europe and Africa was available between 2011 and 2018 but is now no longer on the market. In this study, we evaluated a new commercial c‐ELISA to detect ruminant EHDV VP7 Abs in 2,199 serum samples from cattle, sheep, goats, wild deer and zoo animals. The results showed that this ELISA kit is specific and can detect the presence of IgG anti‐EHDV VP7 with a very good diagnostic specificity and a satisfactory sensitivity in domestic ruminants, zoo animals and wild deer. Therefore, the evaluated c‐ELISA can detect the introduction of EHDV into an area where BTV‐seropositive domestic animals are present. The performance of this kit is similar to that of the c‐ELISA A kit and can thus be used for diagnosis. [ABSTRACT FROM AUTHOR]

Bluetongue virus serotype 8 (BTV‐8) caused an epizootic in Europe in 2006/09. Transplacental transmission of BTV‐8 was demonstrated leading to abortions, congenital malformations or nervous clinical signs in newborn calves. BTV‐8 re‐emerged in France in 2015. Although the re‐emergent strain is nearly genetically identical to the one that had circulated in 2006/2009, it has caused very few clinical cases. However, from mid‐December 2018 to April 2019, cases of calves with congenital malformations or displaying nervous clinical signs occurred in some departments (French administrative unit) in mainland France. Blood samples from these animals were sent to local laboratories, and the positive ones were confirmed at the French Bluetongue reference laboratory (BT‐NRL). Out of 580 samples found positive at the local laboratories, 544 were confirmed as RT‐PCR BTV‐8 positive. The 36 samples found positive in the local laboratories and negative in the BT‐NRL were all at the limit of RT‐PCR detection. Hundred eighty‐eight of the confirmed samples were also tested for the presence of Schmallenberg virus (SBV) and bovine virus diarrhoea virus (BVDV) infection: 4 were found positive for BVDV and none for SBV. The main clinical signs recorded for 244 calves, for which a reporting form was completed by veterinarians, included nervous clinical signs (81%), amaurosis (72%) and decrease/ no suckling reflex (40%). Hydranencephaly and microphthalmia were reported in 19 calves out of 27 in which a necropsy was practiced after death or euthanasia. These results indicate that the re‐emergent strain of BTV‐8 can cross the transplacental barrier and cause congenital malformations or nervous clinical signs in calves. [ABSTRACT FROM AUTHOR]

Competitive‐ELISA (c‐ELISA) is the most widely used serological test for the detection of Bluetongue virus (BTV) viral protein 7 (VP7) antibodies (Ab). However, these BTV c‐ELISAs cannot to distinguish between IgG and IgM. IgM Ab are generated shortly after the primary immune response against an infectious agent, indicating a recent infection or exposure to antigens, such as after vaccination. Because the BTV genome or anti‐VP7 Ab can be detected in ruminant blood months after infection, BTV diagnostic tools cannot discriminate between recent and old infections. In this study, we evaluated an IgM‐capture ELISA prototype to detect ruminant anti‐BTV VP7 IgM on 1,650 serum samples from cattle, sheep, or goats. Animals were BTV‐naive, infected, or/and vaccinated with BTV‐1, ‐2, ‐4, ‐8, ‐9, ‐16, or ‐27, and we also included 30 sera from cattle infected with the Epizootic haemorrhagic disease virus (EHDV) serotype 6. Results demonstrated that this ELISA kit is specific and can detect the presence of IgM with satisfactory diagnostic specificity and sensitivity from 1 to 5 weeks after BTV infection in domestic ruminants (for goats and cattle; for sheep, at least up to 24 days). The peak of anti‐VP7 IgM was reached when the level of infectious viruses and BTV RNA in blood were the highest. The possibility of detecting BTV‐RNA in IgM‐positive sera allows the amplification and sequencing of the partial RNA segment 2 (encoding the serotype specific to VP2) to determine the causative BTV serotype/strain. Therefore, BTV IgM ELISA can detect the introduction of BTV (or EHDV) in an area with BTV‐seropositive domestic animals regardless of their serological BTV status. This approach may also be of particular interest for retrospective epidemiological studies on frozen serum samples. [ABSTRACT FROM AUTHOR]

Abstract: In November 2017, a 15‐day‐old calf located in France (Haute‐Savoie department) was found positive for bluetongue virus (BTV) RNA by RT‐PCR. Laboratory investigations allowed the isolation and identification of the serotype: BTV‐4. The analysis of the full viral genome showed that all the 10 genome segments were closely related to BTV‐4 strains involved in a large BT outbreak in the Balkan Peninsula, in Italy since 2014 and in Corsica since the end of October 2016. These results together with epidemiological data suggest that BTV‐4 has been introduced to mainland France from Corsica or Italy where BTV‐4 outbreaks have been reported in summer and autumn 2016. This is the first report of the introduction of BTV‐4 in mainland France. [ABSTRACT FROM AUTHOR]