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Application of real-time RT-PCR (rRT-PCR) for detection of swine vesicular disease virus (SVDV) in samples of archival SVDV isolates and clinical samples collected from SVDV infected pigs was described. A primer set that targets the IRES region of the SVDV genome and TaqMan probe specific for a highly conserved region in SVDV RNA IRES region were used. The assay detected viral RNA in all tested archival strains of SVDV isolated in Europe during years 1972-73 and 1992 as well as in clinical samples collected from experimentally infected pigs. The rRT-PCR can provide quantitative and qualitative information and is more sensitive and faster to perform than the conventional RT-PCR.
The aim of this study was to validate real-time RT-PCR (rRT-PCR) assays for the detection and typing of bluetongue virus (BTV) serotypes recently circulating in Europe. The universal rRT-PCR assay (for all BTV genotypes) was based on a highly conserved region in BTV RNA segment 1, and the serotype-specific (BTV typing) rRT-PCR was based on the BTV Seg-2 target gene encoding the highly variable outer shell protein VP2. The rRT-PCR techniques applied here are very fast (approximately 4 h), specific and sensitive for the detection and identification of BTV serotypes. Using the BTV-typing rRT-PCR, it was possible to identify European BTV serotypes 1, 2, 4, 6, 8, 11 and 16 in archival blood samples collected in 2008-2011 for the purpose of a ring trial for BTV genome and antibody detection. This assay may therefore be considered as a valuable tool complementing the routine diagnostic procedure for BTV diagnosis.
The aim of this study was to determine the prevalence of bluetongue virus (BTV) in the blood of susceptible animals, tested in the frame of the BT national monitoring programme. The rRT-PCR assay was applied to virological examination of animals imported from BT-affected countries. On December 5, 2007, the BTV RNA was detected for the first time in blood samples of seropositive cattle from Germany. So far, the presence of the RNA was detected in 37 samples of blood collected from German cows and in one sample taken from Dutch fallow deer. The presence of viral RNA was also found in the blood taken from a 4-week-old calf born from BT positive dam imported from Germany. It was an evidence of the vertical transmission of BTV. The long persistence of BTV in blood of infected animals was demonstrated. The viral RNA was detectable as long as one month after the first collection. Taking into consideration the above results, the implemented virological monitoring tests, in parallel with the surveillance studies, should be continued to monitor the actual BT status in Poland.
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Bluetongue vaccines in Europe

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The article reviews the history, present status and the future of BT vaccines in Europe. So far, an attenuated (modified live viruses, MLV) and inactivated virus vaccines against BT were developed and used in the field. Moreover, the virus-like particles (VLPs) produced from recombinant baculovirus, and live recombinant vaccinia or canarypox virus-vectored vaccines were tested in the laboratory. The main aims of BT vaccination strategy are: to prevent clinical disease, to reduce the spread of the BTV in the environment and to protect movement of susceptible animals between affected and free zones. Actually, all of the most recent European BT vaccination campaigns have used exclusively inactivated vaccines. The use of inactivated vaccines avoid risk associated with the use of live-attenuated vaccines, such as reversion to virulence, reassortment of genes with field strain, teratogenicity and insufficient attenuation leading to clinical disease. The mass vaccinations of all susceptible animals are the most efficient veterinary method to fight against BT and successful control of disease. The vaccination of livestock has had a major role in reducing BTV circulation and even in eradicating the virus from most areas of Europe.
Understanding the interaction between the bluetongue virus (BTV), the Culicoides vector and the ruminant host is essential to control bluetongue (BT). This triangle of interaction can be understood individually at the level of the virus, the level of vector and the host level. BTV-vector-host interactions involve physiological and ecological mechanisms, and they have evolved under a specific set of environmental conditions. Recent advances in understanding this interaction include increased knowledge of the virus replication cycle, BTV immunology and pathogenesis in the vertebrate host, as well as the virulence and pathogenicity features of newly discovered BTV serotypes. To understand the virus-host-vector interaction, new molecular biology techniques and experimental infection biology methods have been widely used. The next-generation sequencing, the establishment of a reverse genetics system for the virus, and development of novel infection models and refinement of the existing BTV experimental infection methodologies have proven very helpful. This progress in biotechnology has also made it possible to develop new-generation BTV vaccines, such as disabled infectious single cycle (DISC) vaccines and disabled infectious single animal (DISA) vaccines. However, several questions still need to be answered, such as those concerning cellular pathways involved in the induction of innate immunity and the function of NS4 in the BTV replication cycle. In addition, the identities of specific molecular determinants and the role of quasi-species diversity in determining BTV phenotype are still unclear and should be better explained.
The aim of this study was to determine the diagnostic specificity, sensitivity and repeatability of four commercially available ELISA kits for the detection of antibodies against bluetongue (BT) virus. The relative specificity of ELISAs was estimated using a panel of sera originated from healthy cattle never vaccinated nor exposed to BT virus. All ELISA kits had a high relative specificity (99.2-99.4%). The relative sensitivity of ELISAs estimated using a panel of sera collected from BTV infected cattle was also high and similar for all kits (97.4-100%). However, the relative sensitivity evaluated on the basis of testing of vaccinated animals was different for the used ELISAs: the LSI, ID VET and Ingenasa kits had a high sensitivity (85.2-98.2%) but the sensitivity of VMRD ELISA was much lower (68.6%). The repeatability of ELISAs was expressed as a coefficient of variation (CV) of results of sera tested 5 times in the same day and 10 times in different days through the period of 2 months, by the same person, in the same conditions, and by using of the same equipment. The CVs of sera tested in Ingenasa and ID VET kits ranged from 6.1 to 9.8% and were below the 10% threshold adopted as a maximal for the acceptable repeatability of a method. In conclusion, it can be stated that the applied ELISAs can be a valuable diagnostic tool for the serological monitoring studies in the BTV infected premises. Nevertheless, the Ingenasa and ID VET ELISAs can be the most useful in sero- -surveillance of livestock following vaccination.
A novel real-time RT-PCR (rRT-PCR) for the detection and typing of bluetongue virus (BTV) in EDTA treated blood samples taken from BTV infected animals was described. This rRT-PCR was based on BTV Seq-2 target gene encoding the highly variable outer shell protein VP2. The applied PCR was accurate, specific, and reliable technique for the detection of a specific sequence for a BTV type and endogenous internal positive control (IPC) in the same well. Using this technique, it was possible to identify the European BTV serotypes 1, 6, and 8 in archival blood samples supplied during 2008-2010 for the purpose of the ring trial for BTV genome and antibody detection. Moreover, it was shown that all archive BTV positive blood samples taken from seropositive cattle imported to Poland from Germany were positive for BTV8. This method was much faster (approximately 4 h) and more precise than conventional serological typing methods. In addition, the used thermal cycler allows the use of 96-well plate formats, which further increases the capacity and speed of the analysis. Therefore, it seems to be a valuable complementing tool for a routine diagnosis of BTV infection.
Peste des petits ruminants (PPR) is a highly contagious viral disease of domestic and wild small ruminants caused by the peste des petits ruminants virus (PPRV), which belongs to the genus Morbilivirus in the family Paramyxoviridae. The PPRV causes disease in goats and sheep, as well as in wild ruminants, such as gazelle, deer, antelope, Nubian ibex, gemsbok and others. PPR was first recorded in early 1942 in Ivory Coast, West Africa, and spread to around 70 countries in Africa, the Middle East and Asia – regions that are home to over 80% of the world’s sheep and goats. Until 2018, PPR had never been detected in Europe. On 24th June 2018, however, the Bulgarian authorities reported cases of PPR in sheep in the village of Voden, Bolyarovo municipality of Yambol region, on the border with the Thrace region of Turkey. It was the first occurrence of PPR in Bulgaria and in the European Union (EU). The control and eventual eradication of PPR is now one of the top priorities for the Food and Agriculture Organization (FAO) and the World Organization for Animal Health (OIE). In 2015, the international community agreed on a global strategy for PPR eradication, setting 2030 as a target date for elimination of the disease. The aim of this paper was to highlight future research that could be performed to guide and facilitate the PPR eradication programme. Such research includes studies on PPR transmission and epidemiology, as well as the development and application of new-generation PPR vaccines capable of differentiating infected from vaccinated animals (DIVA). Moreover, there is a need for research to improve and adapt existing diagnostic techniques as well as to develop novel PPRV recognition methods, such as a lateral flow device for in-field use, that accelerate decisions about the implementation of control measures.
The article reviews the policy of bluetongue (BT) control in Europe until 2000 and the new strategy adopted in November this year. The control strategy applied until 2000 was consistent with the Directive 92/119/EEC of 17 December 1992, which involved the use of direct control methods, such as the demarcation of a 3-km radius protection zone and a 10-km radius surveillance zone around each infected farm, as well as the slaughter of all susceptible animals on the infected farm and possibly on neighboring farms. This strategy was modified in the autumn of 2000 by the Directive 2000/75/EC, as it became obvious that the stamping-out approach was completely inadequate in dealing with vector-borne diseases, such us bluetongue or epizootic hemorrhagic disease (EHD). According to this directive, the primary strategy for BT control should be based on the strict control of the transfer of susceptible animals from zones considered infected and on vaccination in the protection zone. The areas subject to movement restrictions are defined on the basis of intensive clinical, serological and entomological surveillance. Moreover, a strict quarantine of animals and herds is applied, as well as a safe utilization of dead animals and disinfection of animals, buildings and environment with insecticides. By the Commission Decision 2008/655/WE, the strategy for BT control also includes vaccinations aimed at reducing the spread of the virus in the environment, and measures to ensure safe movement of susceptible animals between affected and free zones. A BT control policy that combines administrative methods with prophylactic vaccination of all susceptible animals, supplemented by the application of insecticides to control Culicoides midges in the environment, is currently the most effective strategy for BT eradication.
Bluetongue (BT) is an infectious, non-contagious disease of animals, especially domestic animals and wild ruminants. BT is considered endemic in wildlife in large parts of Africa and North America. Most species of wild ruminants are susceptible to BTV infection, though frequently asymptomatically. The pathogenicity of BT among wildlife ranges from asymptomatic to fatal. Wild sheep, such as as bighorn and mouflon, are susceptible to BTV infection and can develop fatal clinical disease just like domestic sheep. Clinical disease also results from experimental or natural infection of antelope, wapiti, musk, ox, bison, yak, white-tailed deer and African buffalo, whereas blesbock, mountain gazelle, roe deer, red deer and Eurasian elk do not show clinical signs after natural or experimental infection, which can only be recognized by the presence of BTV-specific antibodies or viral RNA. Some camelids are also reportedly susceptible to BTV infection. A severe clinical form of this lethal disease has been reported in naturally infected llamas, whereas an experimental infection of llamas induced antibodies against BTV, but no clinical signs were observed. No clinical signs of BT have been observed in experimentally infected dromedary camels, but all animals seroconverted, and RNA BTV was isolated from the blood during viraemia, which suggests that camels may act as a reservoir for BTV and play an important role in its transmission. Wild animals, particularly cervids (because of their wide distribution in Europe), could be used as sentinels for the surveillance of BTV.
Bluetongue virus (BTV), the aetiological agent of bluetongue (BT), is a small (about 70 nm in diameter) icosahedral virus with a genome composed of ten linear segments of double-stranded RNA (dsRNA), which is packaged within an icosahedral nucleocapsid composed of seven structural proteins. The BTV genome evolves rapidly via genetic drift, reassortment of genome segments (genetic shift) and intragenic recombination. This evolution, and random fixation of quasispecies variants during transmission of BTV between susceptible animals and vectors appear to be the main mechanism leading to the observed genetic diversity amongst BTV field strains. The individual BTV gene segments evolve independently of one another by genetic drift in a host-specific fashion, generating quasispecies populations in both ruminant and insect hosts. Reassortment of BTV genes is responsible for genetic shift among strains of BTV, and has been demonstrated after infection of either the ruminant host or insect vector with different strains or serotypes of BTV. Intragenetic recombination, whereby mosaic genes are generated from the “splicing” together of homologous genes from different ancestral viral strains, has been demonstrated for BTV. The genetic variation of BTV is likely responsible for differences in the virulence and other phenotypic properties of individual field strains of the virus.
A reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was applied for the detection of the RNA of bluetongue virus (BTV). A primer set that targets conserved segment 1 of the BTV genome was used. The assay detected the viral RNA in all archival BTV-positive samples. Results of the study show that the sensitivities of the RT-LAMP and real-time RT-PCR assays were equal, and the detection limit for both methods was the 1/160 dilution of BTV-infected blood samples. RNA isolated from blood samples taken from healthy uninfected cattle (negative control) was not detected in this assay. No cross-reactivity of the primers with the genes of symptomatic look-alike diseases, such as foot-and-mouth disease (FMDV) and peste des petits ruminants (PPR), was found. Including the time required for the extraction of RNA, its presence in archival EDTA-treated blood samples could be detected within 2 hours. RT-LAMP is a very fast, sensitive, and specific technique for the detection of BTV in biological samples. Therefore it can be a valuable tool complementing the routine diagnostic procedure for BTV diagnosis.
The aim of this study was to evaluate the occurrence of antibodies to the bluetongue virus (BTV) in animals imported to Poland in 2008, the calves born to bluetongue positive cows and Polish-origin animals kept together with imported cattle. From January 1 to December 15, 2008, a total of 25,495 samples of sera was tested using the c-ELISA and direct ELISA. Out of the tested sera, 1,511 (5.92 %) were found to be positive for BTV. The majority of seropositive cattle were imported to Poland from Germany (987; 65.3%) and the Netherlands (290; 19.2%). Maternal antibodies were detected in 129 (8.5%) samples of sera taken from calves born to seropositive dams of German and Dutch origin. The high number of seroreagents was the result of bluetongue vaccination implemented in BTV-infected EU member States in 2008. In conclusion, it can be stated that surveillance studies should be continued to monitor the actual bluetongue status of Poland. However, an ELISA for the differentiation of infected and vaccinated animals should be introduced to laboratory practice to determine the number of BTV post-infected seropositive animals in the population of imported animals.
The article reviews the occurrence of Schmallenberg disease in Europe from 2011 to September 2013. The first cases of disease caused by Schmallenberg virus (SBV) were reported in Germany and the Netherlands in the late summer/autumn of 2011 in adult dairy cows displaying hyperthermia, drop in milk production and diarrhea. In November 2011, by means of a metagenomic approach, for the first time the Friedrich-Löeffler Institute (Germany) detected viral RNA belonging to a new virus in blood samples from clinically affected dairy cows. This new virus was called Schmallenber virus after the place of origin of the collected samples. Phylogenetic analysis revealed that SBV belongs to the genus Orthobunyavirus within the family Bunyaviridae. Ortobunyaviruses are widely distributed in the world; mainly in Asia, Africa, Australia and Oceania, in tropical and subtropical areas, with a warm and humid climate. Their occurrence depends primarily on the presence of Culicoides spp. vector and a reservoir for the virus, which are diseased and infected animals. In Europe, since the first cases of SBV infection in 2011 until September 2013 the presence of SBV or specific antibodies were detected in 27 European countries, including twenty three EU Member States (Austria, Belgium, Czech Republic, Croatia, Denmark, Estonia, Finland, France, Hungary, Germany, Ireland, Italy, Latvia, Lithuania, Luxembourg, The Netherlands, Poland, Romania, Slovenia, Spain, Sweden, United Kingdom and Greece) and four non-Member States (Switzerland, Norway, Russia and Serbia). SBV infection was detected mainly in cows and sheep, in 5636 and 2922 farms, respectively. SBV has since been detected in approximately 9000 farms; the most being found in France (4557) and Germany (2046).
Peste des petits ruminants (PPR) is a highly contagious disease of small ruminants that leads to high morbidity and mortality, and thereby results in devastating economic consequences to the livestock industry. It is caused by the PPR virus (PPRV), which belongs to the genus Morbilivirus in the family Paramyxoviridae. PPR was first recorded in early 1942 in Ivory Coast, West Africa. In the following years, the disease extended its distribution to other parts of the world and now circulates throughout Northern, Eastern and West Africa, as well as Asia – in particular, China, Central Asia, Eurasia, the Indian subcontinent and the Middle East. The molecular epidemiology of PPRV, based on the sequence comparison of a small region of either the N or the F gene, has revealed the existence of four distinct lineages (I-IV) of the virus. Until June 2018, PPR had never been detected in Europe, with the exception of the European part of Turkish Thrace. However, on 24th June 2018 the Bulgarian authorities reported cases of PPR in sheep in the village of Voden, Bolyarovo municipality of Yambol region, on the border with the Thrace region of Turkey. It was the first occurrence of PPR in Bulgaria and in the European Union (EU). The source of PPR infection in Bulgaria is not clear, it could have been the illegal movement of animals, contaminated materials or humans, e.g. refuges. Due to the increased risk of introduction of PPR from North Africa and Turkey to neighbouring regions, the European Food Safety Authority (EFSA) has recently published a report assessing the risk of PPR spreading in Europe. According to a scientific opinion by the EFSA, the spread of PPRV in the territory of the UE could occur by the illegal transport of infected animals or infected animal products. In order to limit the spread and impact of PPR outbreaks in Europe, rapid detection, movement restriction, prompt culling of infected herds and disinfection measures should be introduced immediately. The control and eventual eradication of PPR is now one of the top priorities for the Food and Agriculture Organization (FAO) and the World Organization for Animal Health (OIE). In 2015, the international community agreed on a global strategy for PPR eradication, setting 2030 as a target date for elimination of the disease.
Rapid and accurate diagnosis plays an important role in the implementation of effective measures to control the spread of disease. Historically, the laboratory diagnosis and typing of BTV were carried out by various serological and virological methods, including virus neutralization (VN) assay, ELISA, as well as virus isolation (VI) in cell cultures or in embryonated chicken eggs. At present, various molecular techniques to detect BTV genome are increasingly used as primary diagnostic tools for the serotyping and epidemiological investigations of BTV. Initially, the viral RNA was detected by simple nucleic acid hybridization technologies. Then, conventional RT-PCR assays were developed and evaluated for the detection of BTV serotypes based on nucleotide sequences of different genome segments. Although RT-PCR, with its increased sensitivity, has advantages over hybridization, it is almost impossible to quantify accurately by regular and multiplex PCR procedures, and regular PCR may produce false positive results. Over the recent years, a number of real-time RT-PCR (rRT-PCR) methods have been described. The rRT-PCR offers certain advantages over conventional RT-PCR assay, as it is more rapid, sensitive, and can provide quantitative as well as qualitative genetic information. It does not use agarose gel electrophoresis, decreases the risk of contamination because it is run within an enclosed tube, and is suitable for large-scale testing and automation. The target amplicon is usually smaller, reducing the potential for problems caused by target degradation. Loop-mediated isothermal amplification (LAMP), a novel rapid, accurate and cost effective gene amplification method, is an autocycling and strand displacement DNA synthesis method. LAMP assays have been applied as a method of detecting a variety of animal pathogens, including BTV. RT- LAMP assay can be a valuable tool complementing the routine laboratory diagnosis of BTV.
The aim of this study was to estimate the diagnostic value of different commercially available ELISA kits for the detection of bluetongue virus (BTV) antibodies in infected and vaccinated animals. The relative specificity of ELISA kits was evaluated using a panel of sera originating from healthy cattle, never vaccinated nor exposed to BTV. All ELISA kits applied had a high relative specificity (99.3 - 100%). The relative sensitivity of ELISA kits assessed using a panel of sera collected from BTV infected cattle was also high and similar for all the kits (97.3 - 100%). However, the relative sensitivity evaluated on the basis of testing vaccinated animals was different: the highest sensitivity was found for Ingenasa, PrioCHECK and ID VET ELISAs (96.5 - 98.3%). Slightly lower sensitivity was calculated for Pourquier and LSI kits (82.8% and 85.4%, respectively) and much lower sensitivity was found for VMRD ELISA kit (69.5%). The repeatability of BTV ELISA kits was expressed as a coefficient of variation (CV) of results of sera tested 5 times in the same day and in different days by the period of 2 months, by the same person, in the same conditions, and by using the same equipment. The CVs of sera tested in all ELISA kits ranged from 6.1 to 9.8% and were below 10% threshold adopted as a maximum for the acceptable repeatability of the method. In conclusion, it can be stated that the applied ELISA kits can be a valuable diagnostic tool for the serological monitoring studies in the BTV contaminated premises. All the methods are very specific and sensitive when testing BTV infected animals. Nevertheless, the Ingenasa and PrioCHECK can be the most useful in sero-surveillance of livestock following vaccination.
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