Bluetongue Research Articles

Bluetongue virus non-structural protein 3 (NS3) and NS4 coordinatively antagonize type Ⅰ interferon signaling by targeting STAT1

Previous studies have pointed out that bluetongue virus (BTV) down-regulates the expression levels of type Ⅰ interferon (IFN-Ⅰ) and inhibits IFN-Ⅰ signaling by targeting on the Janus tyrosine kinase (JAK)-signal transducer and activator of transcription protein (STAT) pathway. However, individual viral protein could not effectively block IFN-Ⅰ signaling. There is a need to explore the underlying mechanisms by which viral proteins of BTV coordinate to antagonize the IFN-Ⅰ signaling. We investigated the coordinative role of BTV-1 nonstructural protein 3 (NS3) and NS4 in counteracting IFN-Ⅰ signaling in the JAK-STAT pathway by directly interacting with STAT1. The NS3 and NS4 targeted the SH2 domain of STAT1 to inhibit its phosphorylation, heterodimerization, nuclear translocation, as well as activation of downstream genes of the JAK-STAT pathway. NS3 and NS4 impaired STAT1 phosphorylation induced by IFN-Ⅰ in a dose dependent manner. Overall, this study confirmed that NS3 and NS4 of BTV participate in interfering with IFN-Ⅰ signaling process. Also, a new mechanism employed by BTV to evade host innate immune responses was revealed.

Inter-annual home range fidelity of wild and ranched white-tailed deer in Florida: implications for epizootic hemorrhagic disease virus and bluetongue virus intervention

Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) are vector-borne orbiviruses affecting ranched and wild white-tailed deer (Odocoileus virginianus) in North America. Currently, limited data exist on EHDV and BTV transmission dynamics in ranched and wild herds. To identify long-term site-specific EHDV and BTV intervention strategies (e.g., integrated pest or animal husbandry management), it is important to understand inter-annual home range fidelity (site fidelity). This study examined inter-annual site fidelity of ranched and wild deer in FL, USA. We estimated and compared inter-annual site fidelity of individual ranched and wild deer during the EHDV and BTV transmission season (May 1–October 31) for two consecutive years. GPS collars were attached to 11 wild and 4 ranched animals. Inter-annual site fidelity was calculated using the overlap function in the continuous-time movement modeling (ctmm) package in R, which estimates a Bhattacharyya coefficient (BC) between years. BC values range from 0 to 1, with values closer to 1 representing high degrees of overlap (site fidelity) between annual home ranges. The mean BC overlap was 0.876 (± 0.056 SE) and 0.831 (± 0.108 SE) for wild and ranched animals, respectively. We observed high levels of inter-annual site fidelity for 10 of 11 wild deer and 3 of 4 ranched deer. High inter-annual home range fidelity suggests EHDV and BTV intervention strategies, such as food plot (wild, ranches) or feeder (ranches) movements, or exclusion fencing to reduce deer time in vector habitat, may have multi-year impacts.

Soluble expression and purification of Bluetongue Virus Type 1 (BTV1) structure protein VP2 in Escherichia coli and its immunogenicity in mice.

BackgroundThe VP2 on the surface of the virus particle is the main structural protein of BTV, which can induce the host to produce neutralizing antibodies and play an important role in the antiviral immunity process. This study aimed to obtain the soluble VP2 and analyze its immunogenicity.MethodsThe gene encoding the full-length VP2 of BTV1 was amplified by PCR. The products from restriction enzyme digestion and ligase reaction between VP2 and vector pET-28a were transformed into E.coli DH5α. After PCR and sequencing detection, the positive plasmid PET28a-VP2 was transformed into E.coli BL21(DE3) and Rosetta(DE3) competent cells, expression induced by IPTG. The fusion protein was expressed in the optimized conditions with the induction of IPTG, purified by affinity chromatography and identified by SDS-PAGE and Western blotting. A total of 5 Balb/c mice aged 6–8 weeks were immunized with the fusion protein at a dose of 30 µg per mouse. Each mouse was immunized three times at an interval of 3 weeks.ResultsThe recombinant plasmid PET28a-VP2 was successfully constructed. The expression strains were induced by 0.4 mmol/L IPTG at 16 °C for 10 h, and BTV1 VP2 was expressed in a soluble form. The purity of the recombinant VP2 protein (∼109 kDa) was about 90% in the concentration at 0.2 mg/ml afterpurification. The purified VP2 had good immunoreactivity with BTV1 positive serum. Taken together, thisstudy offered a route for producing soluble BTV VP2, which retains activity and immunogenicity, to bebeneficial to the research on developing BTV vaccine, and lay the foundation for further research on BTV.

Development of recombinant NS1-NS3 antigen based indirect ELISA for detection of bluetongue antibodies in sheep

Bluetongue is an insect borne (Culicoides) viral disease of small ruminants. The virus blankets the globe with a wide serotypic variation, numbered from 1 to 28. In India 21 different serotypes have been reported to be circulating across the various agro-climatic zones of the country. Non-structural proteins (NSPs) of bluetongue virus have always remained ideal target for differentiation of infected from vaccinated animals. The current study is an extrapolation of our previous work where a novel fusion construct comprising of bluetongue viral segment NS1 and NS3 was successfully cloned, expressed, purified with an efficient strategy for its suitable implementation as a diagnostic antigen. In this study, the applicability of the fusion construct has been further evaluated and optimised for field applicability. The fusion construct used in an ELISA platform projected a relative diagnostic sensitivity and specificity of 98.1% and 95.5% respectively against a pre-established test panel. The rNS1-NS3 ELISA showed substantially good agreement with the commercial BTV antibody detection kit. Finally, the study brings together the diagnostic capability of two NSPs, which can be a handy tool for sero-surveillance of bluetongue.

Concurrent bluetongue and theileria infections in pattanam sheep flocks and their management

Astudy was undertaken to find out the concurrent mixed bluetongue and theileriosis in Pattanam sheep in the Cauvery delta region of Tamil Nadu. During September to October 2018, a total of 42 sheep (aged 3 months to 5 yrs.) from five flocks exhibiting symptoms of anorexia, oral lesions, lameness and lymph node enlargement was studied. On reverse transcriptase polymerase chain reaction (RT-PCR), the presence of bluetongue virus was confirmed in 2 (4.76%) sheep. Giemsa stained peripheral blood smears showed the presence of Theileria spp. in 8 (19.05%) animals. Besides these, 15 (35.71%) sheep had the concurrent infections of both bluetongue and theileria. Blue tongue virus antibodies could not be detected in all the serum samples by ELISA. The morbidity and mortality rates in flocks ranged from 10.0 to 85.7% and 3.1 to 16.0%, respectively. The mixed infections were predominantly seen in males aged between 7 months to 2 yrs. The positive animals were treated with oxytetracycline (10 mg/kg IV), buparvaquone (2.5 mg/kg IM) and meloxicam (0.5 mg/kg IM) along with supportive treatment. After treatment, 95% of animals recovered while 5% succumbed due to advanced stage of disease. Early diagnosis and screening of animals for concurrent/multiple pathogens and implementation of vector control measures are needed to reduce the losses associatedwith these diseases.

Pathogen detection and disease diagnosis in wildlife: challenges and opportunities.

The availability of rapid, highly sensitive and specific molecular and serologic diagnostic assays, such as competitive enzyme-linked immunosorbent assay (cELISA), has expedited the diagnosis of emerging transboundary animal diseases, including bluetongue (BT) and African horse sickness (AHS), and facilitated more thorough characterisation of their epidemiology. The development of assays based on real-time, reverse-transcription polymerase chain reaction (RT-PCR) to detect and identify the numerous serotypes of BT virus (BTV) and AHS virus (AHSV) has aided in-depth studies of the epidemiology of BTV infection in California and AHSV infection in South Africa. The subsequent evaluation of pan-serotype, real-time, RT-PCR-positive samples through the use of serotype-specific RT-PCR assays allows the rapid identification of virus serotypes, reducing the need for expensive and time-consuming conventional methods, such as virus isolation and serotype-specific virus neutralisation assays. These molecular assays and cELISA platforms provide tools that have enhanced epidemiologic surveillance strategies and improved our understanding of potentially altered Culicoides midge behaviour when infected with BTV. They have also supported the detection of subclinical AHSV infection of vaccinated horses in South Africa. Moreover, in conjunction with whole genome sequence analysis, these tests have clarified that the mechanism behind recent outbreaks of AHS in the AHS-controlled area of South Africa was the result of the reversion to virulence and/or genome reassortment of live attenuated vaccine viruses. This review focuses on the use of contemporary molecular diagnostic assays in the context of recent epidemiologic studies and explores their advantages over historic virus isolation and serologic techniques.

Diagnostic applications of molecular and serological assays for bluetongue and African horse sickness.

The availability of rapid, highly sensitive and specific molecular and serologic diagnostic assays, such as competitive enzyme-linked immunosorbent assay (cELISA), has expedited the diagnosis of emerging transboundary animal diseases, including bluetongue (BT) and African horse sickness (AHS), and facilitated more thorough characterisation of their epidemiology. The development of assays based on real-time, reverse-transcription polymerase chain reaction (RT-PCR) to detect and identify the numerous serotypes of BT virus (BTV) and AHS virus (AHSV) has aided in-depth studies of the epidemiology of BTV infection in California and AHSV infection in South Africa. The subsequent evaluation of pan-serotype, real-time, RT-PCR-positive samples through the use of serotype-specific RT-PCR assays allows the rapid identification of virus serotypes, reducing the need for expensive and time-consuming conventional methods, such as virus isolation and serotype-specific virus neutralisation assays. These molecular assays and cELISA platforms provide tools that have enhanced epidemiologic surveillance strategies and improved our understanding of potentially altered Culicoides midge behaviour when infected with BTV. They have also supported the detection of subclinical AHSV infection of vaccinated horses in South Africa. Moreover, in conjunction with whole genome sequence analysis, these tests have clarified that the mechanism behind recent outbreaks of AHS in the AHS-controlled area of South Africa was the result of the reversion to virulence and/or genome reassortment of live attenuated vaccine viruses. This review focuses on the use of contemporary molecular diagnostic assays in the context of recent epidemiologic studies and explores their advantages over historic virus isolation and serologic techniques.

Emerging threat of bluetongue in Eastern and North-Eastern Indian states

Albeit bluetongue (BT) in India is endemic to southern and western parts, eastern and north-eastern parts of the country didn't experience any outbreak or reported active disease. However, sero-epidemiology indicates bluetongue virus (BTV) is in circulation in animals and vectors of eastern and north-eastern states of India. Moreover, in recent years BTV has been isolated from sheep, Culicoides midges and goat from this region that substantiate the notion. All the epidemiological components of BT, viz. susceptible hosts, suitable climatic conditions for propagation of vectors, competent vectors are present that pose emerging disease threat in eastern and north-eastern parts of India. Hence, further surveillance and preparedness are recommended to avoid future BT outbreak, if any.

First seroprevalence investigation of epizootic haemorrhagic disease virus in Libya

Background: Epizootic haemorrhagic disease (EHD) is a vector-borne viral disease of domestic and wild ruminants. Epizootic haemorrhagic disease virus (EHDV) is transmitted by Culicoides spp. EHDV is a member of the Orbivirus genus within the Reoviridae family. It shares many morphological and structural characteristics with other members of the genus, such as the bluetongue virus, African horse sickness virus, and equine encephalosis virus.Aims:The purpose of our study was to investigate the epidemiological situation of EHDV in Libya in order to gain some knowledge about the presence of this virus in the country.Methods:In this study, we investigated the seroprevalence of EHDV in Libya, testing 855 blood samples collected during 2015. The samples were collected from domestic ruminants (cattle, sheep, and goats) originating from 11 provinces of Libya. Sera were tested by competitive enzyme-linked immunosorbent assays and positive samples confirmed by serum neutralization test.Results:The overall seroprevalence of EHDV was estimated to be 4% (95% confidence intervals = 2.8%–5.4%). Small ruminant seroprevalence was significantly (p = 0.016) higher than that found in cattle. Neutralizing antibodies against EHDV-6 were detected in a sheep from the western region of Libya.Conclusion:This study suggests that EHDV has circulated or is circulating in Libya, and sheep could play an important role in the epidemiology of EHDV, and the virus may still be circulating in North Africa.

Spina bifida, diplomyelia and multiple malformations in a Texel lamb

ABSTRACT: This report described the clinical and pathological aspects of open spina bifida and diplomyelia along with multiple congenital malformations in a Texel lamb. Clinically, paresis of the thoracic limbs, paralysis of the pelvic limbs and a cutaneous opening in the lumbosacral region were observed. At necropsy, there was a focally extensive disruption of the skin associated with an absence of the dorsal portions of the lumbosacral vertebrae. Additionally, diplomyelia of the lumbar segment, mild hydromyelia of thoracic segment, and moderate communicating hydrocephalus of the lateral and third ventricles were noted. Possible viral etiologies (bovine viral diarrhea virus, bluetongue virus, and Schmallemberg virus) were not detected by RT-PCR, and toxic plants were not identified. Therefore, a possible genetic cause may not be discarded.

Synthesis, Characterization and Antiviral Activity of Chrysin Derivatives

In this work, the isolation of chrysin (1), which is a significant constituent from hexanes concentrate of Derris scandens is reported. A progression of new 1,2,3-triazole subsidiaries of chrysin were planned, combined and assessed for their antiviral movement against newcastle disease virus (NDV) and blue tongue virus (BTV) cell lines. These synthetic derivatives have indicated great antiviral action. All the synthesized compounds (3a to 3g) were distinguished by using nuclear magnetic resonance (NMR) and mass spectroscopic techniques. Among derivatives, 3a, 3e, 3f and 3g displayed conspicuous action against NDV, then again compounds 3a, 3b, 3c, 3e, 3f and 3g showed a remarkable action against BTV than chrysin.

Blood meal analysis: host-feeding patterns of biting midges (Diptera, Ceratopogonidae, Culicoides Latreille) in Slovakia.

Biting midges of the genus Culicoides are vectors of important pathogens affecting domestic and wild animals and have played a major role in the re-emergence of new outbreaks of bluetongue (BTV) and Schmallenberg (SBV) viruses in Europe. To determine vector-host specificity, trophic preference from blood meal analysis is of major importance in the surveillance of arthropod-borne diseases. Of 28,752 specimens collected, we identified 17 Culicoides species and investigated a total of 48 host sequences from the blood meals. Culicoides obsoletus/C. scoticus, C. dewulfi, C. pulicaris, C. lupicaris, C. punctatus, C. newsteadi, C. riethi, and C. furcillatus were found to feed on mammals (cattle, horses, and humans), birds (domestic chickens), small rodents (Apodemus flavicollis), and hares (Lepus europaeus). To our knowledge, this is the first study investigating trophic preferences of Culicoides spp. in Slovakia. This study demonstrated that Culicoides species are able to feed on domesticated host vertebrates as well as birds, rodents, and humans.

Prevalence and Age Grading of Two Common Culicoides species, in Farms of Warangal Districts of Telangana State, South India

The prevalence and age grading of Culicoides midges from two districts of Warangal in Telangana State, South India was studied considering the species as pests and vectors. The study revealed the species composition, the abundance, host preference and age grading of Culicoides. The morphological characters were used for specific identification of biting midges. The midges were collected from two different farms from Warangal rural and urban districts (cattle and sheep) using CDC-UV light trap connected with suction fan for the period of one year (September 2017 to August 2018). A total of 28,000 flies were collected in which 25,000 (83.33%) were female and 3,000 (16.66%) were males. The species included 10,500 (58.33%) C. oxystoma, 7,500 (41.66 %) C. imicola from cattle farms 10,000 flies from sheep farms including C. imicola 6,500 (65%) and C. oxystoma 3,500 (35%). The age grading of Culicoides revealed significant proportion of parous females which play an important role in transmission of Blue Tongue disease virus.

A novel immunohistochemistry slide adhesive 3-(trimethoxysilyl) propyl methacrylate (tpm) for bluetongue virus serotype-1 antigen detection in ovine foetal tissues

The present study describes the use of 3-(trimethoxysilyl) propyl methacrylate (TPM) as a glass slide adhesive for better tissue adherence in immunohistochemistry. TPM is an alkoxysilane, dissolved in acidified water (pH 3.5) with glacial acetic acid. TPM formed a gel cast on the glass slide surface, which enhanced the net positive charge of the slide. Tissues with net negative charge adhered with gel cast adhesive on the slide surface with covalent bonding. Practically, foetal tissues have less tissue adherence capacity due to less net negative charge. Foetal brain, pancreas, lymph node and umbilical cord of sheep were included in the study. Foetal tissues were collected and fixed in Bouin’s fixative and processed as per standard paraffin embedding technique. Immunohistochemistry was performed on foetal tissues and umbilical cord using three different glass slide adhesive such as poly-L-lysin (PLL), aminopropyl triethoxy silane (APES) and TPM under different antigen retrieval system. TPM significantly enhanced the foetal tissue adherence, when compared with commercially available adhesives such as PLL and APES. In the present study, foetal tissues adhered with TPM coating well tolerated the harsh proteinase K antigen retrieval treatment. Comparatively, TPM coated slides revealed mild to zero tissue loss and less to no background staining. In addition, TPM was cost effective as many commercially available slide adhesives were either costlier or needed accessory chemicals for coating which in turn added the cost per slide. The present study showed that TPM was cost-effective, less hazardous, less time consuming, easy-to-use adhesive for manual preparation of coating slides when compared to other protein adhesive systems. The present experiment also emphasized that tissues with less adherence capacity could be coated with TPM adhesive for best IHC results.

Epidemiology and pathology of bluetongue virus in India: A systematic review

Epidemiology and pathology of bluetongue virus in India: A systematic review

Is Bluetongue Virus a Risk Factor for Reproductive Failure in Tropical Hair Sheep in Brazil?

Background: Bluetongue is a vector-borne viral disease transmitted by midges from the genus Culicoides. The disease can infect most of the ruminant and camelid species, but the severe disease is most often seen in european wool and mutton sheep breeds. In this sense, there is a gap in the knowledge on BTV infection in hair sheep breeds from tropical zones. Thus, this study aimed at establishing whether exposure to BTV is a risk factor for reproductive failure in Santa Inês ewes, a hair sheep breed, reared under tropical conditions in Brazil.Materials, Methods & Results: A retrospective cross-sectional study was carried out in sheep farms in São Paulo state, Brazil, after the rainy season. Serum samples from 110 Santa Inês ewes with a history of reproductive disorders, in the last 6 months, which were included: abortion, premature birth, stillbirth, retention of placenta, infertility, estrus repetition, fetal malformation, weak lamb birth and neonatal death were collected. The presence of antibodies against BTV was assessed by agar gel immunodiffusion method (AGID). Serology to the infectious agents Brucela ovis, Lepstopira spp., Toxoplasma gondii, Neospora caninum and Campylobacter sp. were also assessed. Bivariate associations between the outcome and individual explanatory variables were assessed using the Fisher's exact test. Abortion was the most common reproductive disorder (53%; 74/139) observed, followed by estrus repetition (12%; 17/139) and infertility (11%; 15/139). Other disorders related to the conceptus totaled nearly one fourth of the reported disorders. A total of 20% (22/110) of the ewes were seropositive to BTV. A higher frequency of BTV seropositive than BTV seronegative ewes with a history of abortion was found. Also, abortion with seroreactivity to BTV was tested for prevalence ratio that showed 1.38 [95% CI 1.10-1.74; P = 0.030]. With regards to the abortion involvement of other infectious diseases associated with the seropositive ewes to BTV, more than a half of ewes (53%; 10/19) were solely seropositive for BTV.Discussion: In the current study, it was detected 20% (22/110) of seropositive ewes to BTV. These findings demonstrated that even though the BTV has been considered endemic in tropical countries such as Brazil, there are regions or microclimates in which the virus cannot be present or in varied prevalence. The history of abortion was identified as the potential factor associated with BTV seropositivity in Santa Ines ewes. Equally, the differential diagnosis for other infectious agents related to abortion demonstrated the unique presence of antibodies against BTV in more than half of all cases. Other studies with native sheep flocks in Iran and Nepal also demonstrated a strong positive correlation between abortion history and seropositivity for BTV. Thus, it is possible that in other continents of the world, under tropical conditions, the virus does not behave the same asymptomatic infection such as have been reported for native sheep breeds in Africa. In conclusion, it was demonstrated that one-fifth animals were positive for antibodies against BTV clearly implying the viral spreading in the local hair sheep flocks. These findings highlight the importance of surveillance related to BTV in endemic areas. Therefore, it is recommended to strengthen the surveillance system for BTV within Brazil and to educate farmers about the management and control of this disease.

Infectious diseases surveillance of the Iberian ibex (Capra pyrenaica victoriae) in Western Spain: health and conservation implications

A survey was conducted between 2004 and 2011 to identify potential pathogens present in the main subpopulation of Iberian ibex subspecies Capra pyrenaica victoriae, located in Gredos Mountain range in Western Spain. Samples were collected from 144 animals and subjected to specific procedures to detect the presence of, or evidence of exposure to, viral, bacterial and parasitic agents. A wide diversity of parasites was found, including 17 species of gastrointestinal nematodes and lungworms, nine species of Coccidia and three of Cestoda. Overall, 54% (75/138) of animals were parasitized by ticks (Rhipicephalus bursa, Ixodes ricinus, Haemaphysalis sulcata, and Hyalomma marginatum marginatum). Null detection of Sarcoptes scabiei mites, causal agent of sarcoptic mange, must be highlighted. Serological assays revealed exposure to Babesia ovis (43%, 56/129), Neospora caninum (13%, 14/108), Oestrus spp. (10%, 4/42), Coxiella burnetii (10%, 5/50), Mycobacterium bovis (6%, 3/50), and Toxoplasma gondii (3%, 4/137). We did not detect the presence of antibodies against Chlamydia psittaci, Brucella spp., Mycobacterium avium subspecies paratuberculosis, Visna-Maedi virus and Bluetongue virus. Despite the fact that major pathogens for animal health were not evidenced, the implementation of periodic passive surveillance programs directed to both wildlife and livestock is highly desirable to predict outbreaks that may compromise survival of such wild goat subspecies.

VP2 Gene-Based Molecular Evolutionary Patterns of Major Circulating Bluetongue Virus Serotypes Isolated during 2014–2018 from Telangana and Andhra Pradesh States of India

Introduction: Bluetongue disease is an economically important viral disease of livestock caused by bluetongue virus (BTV) having multiple serotypes. It belongs to the genus Orbivirus of family Reoviridae and subfamily Sedoreovirinae. The genome of BTV is 10 segmented dsRNA that codes for 7 structural and 4 nonstructural proteins, of which VP2 was reported to be serotype-specific and a major antigenic determinant. Objective: It is important to know the circulating serotypes in a particular geographical location for effective control of the disease. The present study unravels the molecular evolution of the circulating BTV serotypes during 2014–2018 in Telangana and Andhra Pradesh states of India. Methods: Multiple sequence alignment with available BTV serotypes in GenBank and phylogenetic analysis were performed for the partial VP2 sequences of major circulating BTV serotypes during the study period. Results: The multiple sequence alignment of circulating serotypes with respective reference isolates revealed variations in antigenic VP2. The phylogenetic analysis revealed that the major circulating serotypes were grouped into eastern topotypes (BTV-1, BTV-2, BTV-4, and BTV-16) and Western topotypes (BTV-5, BTV-12, and BTV-24). Conclusion: Our study strengthens the need for development of an effective vaccine, which can induce the immune response for a range of serotypes within and in between topotypes.

Putative Novel Serotypes '33' and '35' in Clinically Healthy Small Ruminants in Mongolia Expand the Group of Atypical BTV.

Between 2015 and 2018, we identified the presence of three so-far-unknown Bluetongue virus (BTV) strains (BTV-MNG1/2018, BTV-MNG2/2016, and BTV-MNG3/2016) circulating in clinical healthy sheep and goats in Mongolia. Virus isolation from EDTA blood samples of BTV-MNG1/2018 and BTV-MNG3/2016 was successful on the mammalian cell line BSR using blood collected from surveillance. After experimental inoculation of goats with BTV-MNG2/2016 positive blood as inoculum, we observed viraemia in one goat and with the EDTA blood of the experimental inoculation, the propagation of BTV-MNG2/2016 in cell culture was successful on mammalian cell line BSR as well. However, virus isolation experiments for BTV-MNG2/2016 on KC cells were unsuccessful. Furthermore, we generated the complete coding sequence of all three novel Mongolian strains. For atypical BTV, serotyping via the traditional serum neutralization assay is not trivial. We therefore sorted the ‘putative novel atypical serotypes’ according to their segment-2 sequence identities and their time point of sampling. Hence, the BTV-MNG1/2018 isolate forms the ‘putative novel atypical serotype’ 33, the BTV-MNG3/2016 the ‘putative novel atypical serotype’ 35, whereas the BTV-MNG2/2016 strain belongs to the same putative novel atypical serotype ‘30’ as BTV-XJ1407 from China.

Viral Vector Vaccines against Bluetongue Virus.

Bluetongue virus (BTV), the prototype member of the genus Orbivirus (family Reoviridae), is the causative agent of an important livestock disease, bluetongue (BT), which is transmitted via biting midges of the genus Culicoides. To date, up to 29 serotypes of BTV have been described, which are classified as classical (BTV 1–24) or atypical (serotypes 25–27), and its distribution has been expanding since 1998, with important outbreaks in the Mediterranean Basin and devastating incursions in Northern and Western Europe. Classical vaccine approaches, such as live-attenuated and inactivated vaccines, have been used as prophylactic measures to control BT through the years. However, these vaccine approaches fail to address important matters like vaccine safety profile, effectiveness, induction of a cross-protective immune response among serotypes, and implementation of a DIVA (differentiation of infected from vaccinated animals) strategy. In this context, a wide range of recombinant vaccine prototypes against BTV, ranging from subunit vaccines to recombinant viral vector vaccines, have been investigated. This article offers a comprehensive outline of the live viral vectors used against BTV.