Global Distribution and Genetic Heterogeneity of Border Disease Virus.

Border disease virus (BDV) belongs to the genus Pestivirus of the family Flaviviridae. Interspecies transmission of BDV between sheep, cattle, and pigs occurs regularly, sometimes making diagnosis a challenge. BDV can yield substantial economic losses, including prenatal and postnatal infections in lambs, which are the primary source of infection and maintenance of the virus in the population. Since BDV is antigenically and genetically related to bovine viral diarrhea virus (BVDV), it might pose a significant risk to cattle, influencing BVDV eradication campaigns. Similarly, the presence of BDV in swine herds due to pestivirus spillover between small ruminants and pigs might cause uncertainty in classical swine fever virus (CSFV) diagnostics. Therefore, knowledge of BDV epidemiology in different geographical regions will help prevent its spread and optimize control measures. Previous epidemiological studies have shown that various BDV genotypes are predominant in different countries. This review provides an overview of the spread of BDV world-wide in different host species.

Characterization of internal ribosome entry sites according to secondary structure analysis to classify border disease virus strains.

Applying palindromic nucleotide substitutions (PNS) method, variable loci of the internal ribosome entry site (IRES) secondary structure in the 5' untranslated region (UTR) of Border disease virus sequences were analysed allowing their allocation into ten IRES classes within the species. Sequence characteristics of Turkish and Chinese strains were highly divergent from other genogroups, indicating geographic segregation and micro-evolutive steps within the species. Observed heterogeneity in the BDV species has to be considered for potential implications on diagnostic tests, control and preventive measures.

Border disease in cattle.

Within the family Flaviviridae, viruses within the genus Pestivirus, such as Border disease virus (BDV) of sheep, can cause great economic losses in farm animals. Originally, the taxonomic classification of pestiviruses was based on the host species they were isolated from, but today, it is known that many pestiviruses exhibit a broad species tropism. This review provides an overview of BDV infection in cattle. The clinical, hematological and pathological-anatomical findings in bovines that were transiently or persistently infected with BDV largely resemble those in cattle infected with the closely related pestivirus bovine viral diarrhoea virus (BVDV). Accordingly, the diagnosis of BDV infection can be challenging, as it must be differentiated from various pestiviruses in cattle. The latter is very relevant in countries with control programs to eradicate BVDV in Bovidae, as in most circumstances, pestivirus infections in sheep, which act as reservoir for BDV, are not included in the eradication scheme. Interspecies transmission of BDV between sheep and cattle occurs regularly, but BDV in cattle appears to be of minor general importance. Nevertheless, BDV outbreaks at farm or local level can be very costly.

Evidence of circulation of the novel border disease virus genotype 8 in chamois.

Evidence of association between the novel putative border disease virus genotype 8 (BDV-8) and fatal disease in an Alpine chamois (Rupicapra rupicapra) is reported. Diagnostically, we also demonstrated, as already previously reported, the failure of BDV-specific primers (PDB1 and PDB2) to detect BDV-8.

Spatial and Temporal Phylogeny of Border Disease Virus in Pyrenean Chamois (Rupicapra p. pyrenaica).

Border disease virus (BDV) affects a wide range of ruminants worldwide, mainly domestic sheep and goat. Since 2001 several outbreaks of disease associated to BDV infection have been described in Pyrenean chamois (Rupicapra pyrenaica pyrenaica) in Spain, France and Andorra. In order to reconstruct the most probable places of origin and pathways of dispersion of BDV among Pyrenean chamois, a phylogenetic analysis of 95 BDV 5'untranslated sequences has been performed on chamois and domestic ungulates, including novel sequences and retrieved from public databases, using a Bayesian Markov Chain Monte Carlo method. Discrete and continuous space phylogeography have been applied on chamois sequences dataset, using centroid positions and latitude and longitude coordinates of the animals, respectively. The estimated mean evolutionary rate of BDV sequences was 2.9×10-3 subs/site/year (95% HPD: 1.5-4.6×10-3). All the Pyrenean chamois isolates clustered in a unique highly significant clade, that originated from BDV-4a ovine clade. The introduction from sheep (dated back to the early 90s) generated a founder effect on the chamois population and the most probable place of origin of Pyrenean chamois BDV was estimated at coordinates 42.42 N and 1.9 E. The pathways of virus dispersion showed two main routes: the first started on the early 90s of the past century with a westward direction and the second arise in Central Pyrenees. The virus spread westward for more than 125 km and southward for about 50km and the estimated epidemic diffusion rate was about 13.1 km/year (95% HPD 5.2-21.4 km/year). The strong spatial structure, with strains from a single locality segregating together in homogeneous groups, and the significant pathways of viral dispersion among the areas, allowed to reconstruct both events of infection in a single area and of migrations, occurring between neighboring areas.

A new genotype of border disease virus with implications for molecular diagnostics.

Border disease virus (BDV) is a (+) single-stranded RNA pestivirus affecting mainly sheep and goats worldwide. Genetic typing of BDV has led to the identification of at least seven major genotypes. This study reports the detection of a BDV strain from a goat in northwestern Italy during routine investigations. Sequence analysis revealed mutations in the 5'-UTR of the virus with implications for BDV molecular diagnostics. Moreover, subsequent phylogenetic analysis based on the combined 5'-UTR and Npro/partial C genes, showed divergence from known BDV genotypes, revealing the detection of a novel pestivirus group, for which we propose the name BDV genotype 8.

Characterization of one sheep border disease virus in China.

BACKGROUND: Border disease virus (BDV) causes border disease (BD) affecting mainly sheep and goats worldwide. BDV in goat herds suffering diarrhea was recently reported in China, however, infection in sheep was undetermined. Here, BDV infections of sheep herds in Jiangsu, China were screened; a BDV strain was isolated and identified from the sheep flocks in China. The genomic characteristics and pathogenesis of this new isolate were studied. RESULTS: In 2012, samples from 160 animals in 5 regions of Jiangsu province of China were screened for the presence of BDV genomic RNA and antibody by RT-PCR and ELISA, respectively. 44.4% of the sera were detected positively, and one slowly grown sheep was analyzed to be pestivirus RNA positive and antibody-negative. The sheep kept virus positive and antibody negative in the next 6 months of whole fattening period, and was defined as persistent infection (PI). The virus was isolated in MDBK cells without cytopathic effect (CPE) and named as JSLS12-01. Near-full-length genome sequenced was 12,227 nucleotides (nt). Phylogenetic analysis based on 5'-UTR and N(pro) fragments showed that the strain belonged to genotype 3, and shared varied homology with the other 3 BDV strains previously isolated from Chinese goats. The genome sequence of JSLS12-01 also had the highest homology with genotype BDV-3 (the strain Gifhorn). Experimental infections of sheep had mild clinical signs as depression and short-period mild fever (5 days). Viremia was detected in 1-7 days post-infection (dpi), and seroconversion began after 14 dpi. CONCLUSIONS: This study reported the genomic and pathogenesis characterizations of one sheep BDV strain, which confirmed the occurrence of BDV infection in Chinese sheep. This sheep derived BDV strain was classified as BDV-3, together with the goat derived strains in China. These results might be helpful for further understanding of BDV infection in China and useful for prevention and control of BDV infections in the future.

Genetic characterization of border disease virus (BDV) isolates from small ruminants in Italy.

Border disease virus (BDV) belongs to the Pestivirus genus in the family Flaviviridae. Genetic analyses of pestiviruses that have been isolated from sheep and goat have led to the proposal that BDV isolates can be phylogenetically segregated into at least seven clusters, subtypes BDV-1 to BDV-7. In order to investigate the genetic heterogeneity of small ruminant pestivirus isolates in Italy, a selection of 5'-UTR sequences from isolates that were collected from clinical specimens between 2002 and 2014 was analysed. Phylogenetic reconstructions indicated that the BDV-positive samples clustered within the BDV-1, BDV-3, BDV-5, and BDV-7 groups. These results suggested high genetic diversity within the Italian BDV field isolates. The phylogenetic analysis indicated the first evidence of BDV-1 and BDV-5 circulation in Italy. The marked diversity of the pestivirus isolates might reflect the sheep trade with foreign countries.

Molecular characterization of border disease virus strain Aveyron.

For the pestivirus border disease virus (BDV) at least seven major genotypes have been described (BDV-1-BDV-7). So far, complete genomic sequences have been reported for four BDV genotypes (BDV-1-BDV-4). In this study we report the entire genomic sequence of the noncytopathogenic (ncp) BDV-5 reference strain Aveyron. The viral genome encompasses 12,284 nucleotides (nt) and contains one large open reading frame (11,700 nt) flanked by a 370 nt long 5'-untranslated region (UTR) and a 214 nt long 3'-UTR. The genome organization as well as the lengths of the viral polyprotein (3899 amino acids) and the 5'-UTR are very similar to the ones of other BDV strains, while the 3'-UTR of BDV Aveyron is considerably shorter when compared to other BDV strains. Comparative analysis of complete coding sequences revealed that BDV Aveyron shares nucleotide sequence identities of 76.9% to 79.0% with the other BDV strains, and less than 72% identity with other pestiviruses. In contrast to other BDV strains, a unique insertion of four amino acids (KAPD) of unknown origin is present in the C-terminal part of the viral autoprotease NS2 encoded by BDV Aveyron. Immunoblot analysis revealed that infection of cells with the ncp BDV strain Aveyron comprising this unique insertion in NS2 resulted in the expression of high amounts of NS3 and thereby showed that BDV Aveyron significantly differs from other ncp BDV strains in terms of NS2-3 processing and production of NS3.

Detection of border disease virus (BDV) genotype 3 in Italian goat herds.

In January 2011, cases of abortion, stillbirth and weak live kids were reported in two goat herds in northern Italy. Samples from 18 kids found dead, 12 fetuses, and two stillborn kids were analyzed for pestivirus antigen using an ELISA kit and a border disease virus (BDV)-specific RT-PCR. Positive results were obtained in six kids and one fetus. Phylogenetic analysis based on 225 bp of the 5'UTR fragment of the BDV genome from positive samples showed that the goats were infected with BDV genotype 3. Serum and blood samples collected from all animals in both herds were analyzed using competitive ELISA to detect p80 antibodies and RT-PCR to detect viraemia. Pestivirus antibodies were detected in 61/67 goats in herd A and in 38/169 in herd B. A persistently infected (PI) goat was found in herd A. The PI animal was submitted to the laboratory for BDV diagnosis with Ag-ELISA, viral isolation, and nested RT-PCR on tissue samples from the spleen, kidney, brain, liver, lung, ileocaecal valve, mesenteric lymph nodes, and skin. All of the tests were positive for BDV in each of the tissues analyzed. The BDV sequence of the PI was identical to BDV sequences found in other positive animals. This is the first description of a BDV PI goat and the first evidence of BDV genotype 3 circulation in Italy. The study raises questions about the real impact this virus has on breeding goats.

Genetic characterization of a border disease virus isolate originating from Slovakia.

In this study, a major part of genome of the pestivirus isolate 297 from Slovakia, comprising the 7195 nt-long 5΄-UTR-NS3 region was sequenced and analyzed. Conserved cleavage sites between individual viral proteins of this region were determined and the number of amino acids of respective proteins was estimated as follows: 168 for Npro, 100 for C, 227 for Erns, 195 for E1, 373 for E2, 70 for p7, 453 for NS2, and 683 for NS3. Based on sequence and phylogenetic analysis of 5΄-UTR, Npro, and E2 the isolate 297 was characterized as a border disease virus of genotype 3. It was found to be distinct from other BDV-3 strains analyzed so far, consequently forming a distinct branch within the phylogenetic clade. All these data expand a relatively limited knowledge of genetic properties of individual BDV genotypes and strains circulating in the Central Europe.

Detection of border disease virus (BDV) in goat herds suffering diarrhea in eastern China.

BACKGROUND: Border disease virus (BDV) is an important pathogen in sheep and goat production. Neither epidemiological investigation nor any reports of BDV infection was available in China. During Jan to Apr, 2012, several herd goats in Anhui and Jiangsu provinces in eastern China suffered unremitting diarrhea, with morbidity and mortality of about 28-37% and 10-15%, respectively. In the present study, sera and tissue samples from diseased goats of four farms were taken for BDV detection, isolation and identification. RESULTS: Panpesti generic primers and border disease virus (BDV)-specific primers targeting the 5'-UTR region produced RT-PCR positive bands for sera (24/28) and tissue samples (7/30). Twenty positive sera and tissue samples were inoculated onto Madin-Darby bovine kidney (MDBK) cells for virus isolation. Finally, three different strains of BDV, named AH12-01, AH12-02 and JS12/04, were successfully isolated as identified by RT-PCR using 5'-UTR and N(pro) gene primers, sequencing and electron microscopy. Sequences of 5'-UTR and N(pro) genes of them were used for phylogenetic analysis and comparison to other reference sequences available in GenBank. The results indicated AH12-01, AH12-02 and JS12/04 possess high relationship with the BDV 3 group viruses and differed with each other. CONCLUSION: This is the first detection of BDV from goats with diarrhea and confirmation of BDV infection in China.

Genetic variation of Border disease virus species strains.

The 5'-untranslated region of Pestivirus strains isolated from domestic and wild animals were analysed to determine their taxonomic status according to nucleotide changes in the secondary genomic structure using the palindromic nucleotide substitutions (PNS) method. A total of 131 isolates out of 536 Pestivirus strains evaluated, were clustered as Border disease virus (BDV) species. The BDV strains were further divided into at least 8 genotypes or subspecies. Thirty-two isolates from small ruminants suffering from clinical symptoms of Border disease were clustered into bovine viral diarrhoea virus 1 (BVDV-1), BVDV-2 and classical swine fever (hog cholera) virus species and also into the tentative BDV-2 species. Since the definition of an infectious disease is based primarily on a specific causative pathogen and taking into account the heterogeneity of the genus Pestivirus, clinical cases should be named according to the laboratory results. The PNS procedure could be useful for laboratory diagnosis of Border disease in domestic and wild ruminants.

Genetic and antigenic typing of border disease virus (BDV) isolates from Italy reveals the existence of a novel BDV group.

Border disease virus belongs to the Pestivirus genus, within the family Flaviviridae. Genetic analysis of pestiviruses isolated from sheep in continental Europe have led to the proposal that BDV isolates are segregated into at least seven clusters. In 2005 the molecular analysis of an Italian caprine BDV strain provided evidence for the presence of an atypical pestivirus, which may represent the first member of a putative novel pestivirus sub-group. To further build on this study, ovine pestivirus strains were isolated from small ruminant flocks and characterized both genetically and antigenically. A defined section of the 5'UTR and the complete N(pro) coding region were amplified and used for phylogenetic analysis. This revealed that these pestiviruses belong to the BDV species but differed significantly from all previously described ovine pestiviruses providing evidence for the presence of a novel genetic group. Four of the five isolates were also typed antigenically with a panel of pestivirus specific mAbs directed against NS2/3, E(rns) and E2 proteins. The four isolates reacted with a distinct set of mAbs, in particular against the BDV-E2 and the BDV-E(rns) epitopes. The isolates were greatly reactive for E(rns) and NS2/3 mAbs, which are otherwise typical for BVDV-2, and one E2 mAb that typically stains BVDV-1. The Italian pestiviruses analysed in this study, according to their antigenic and genetic properties, clustered into a novel phylogenetic group, that we propose to term BDV-7.

Border disease virus shedding and detection in naturally infected Pyrenean chamois (Rupicapra pyrenaica).

Pyrenean chamois (Rupicapra pyrenaica) populations of the central and eastern Pyrenees have been affected by severe outbreaks associated with Border disease virus (BDV) since 2001. Eight Pyrenean chamois (7 males and 1 female) from 1 to 8 years of age with clinical signs consistent with BDV infection were studied. At necropsy, whole blood, tissue samples (skin, brain, prescapular lymph node, thyroid gland, lung, liver, spleen, kidney, small intestine, bone marrow, and testicle), urine, and nasal, oral, and rectal swabs were obtained. The fetus from a pregnant female was also studied. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the virus in all samples, and virus isolation was performed. Sera and tissue samples were positive to RT-PCR, and the virus was isolated from all chamois. The nasal, oral, and rectal swabs and urine samples were RT-PCR positive in 100%, 85.71%, 71.43%, and 100% of chamois, respectively, confirming the excretion of the virus via these 4 routes. In addition, sera were tested for BDV antibodies using enzyme-linked immunosorbent assay and seroneutralization techniques, with negative results. Sequence analysis of the 5' untranslated region in 7 of the chamois confirmed that the virus is grouped into the BDV-4 genotype, the same BDV previously described in Pyrenean chamois. To the authors' knowledge, this is the first study of naturally infected Pyrenean chamois, providing evidence that infected animals shed BDV through nasal, oral, fecal, and urinary excretion routes.

Complete genomic sequence of a border disease virus isolated from Pyrenean chamois.

This report describes the full-length genome sequence of the pestivirus strain H2121 which was recently isolated from Pyrenean chamois and typed as Border disease virus (BDV) genotype 4. Comparison with full-length genomic sequences of the approved pestivirus species Bovine viral diarrhea virus-1 (BVDV-1), BVDV-2, BDV, and Classical swine fever virus, the tentative species represented by strain Giraffe-1, as well as the atypical pestivirus strain Th/04_KhonKaen confirmed that the chamois pestivirus strain is most similar to BDV. The viral genome of H2121 is 12,305 nucleotides long and contains one large open reading frame. The latter encodes a polyprotein consisting of 3899 amino acids and is flanked with 376 nucleotides long 5' untranslated region (UTR) and 229 nt long 3' UTR. The genome organization of the chamois virus is reminiscent to that of other pestiviruses. Compared to other BDV strains including BDV-1 strain X818 and BDV-2 strain Reindeer-1, the 5' UTR and ORF of the chamois virus are very similar in length, while the 3' UTR of H2121 is 31-44 nucleotides shorter. In contrast to other BDV strains, the genome of the chamois virus contains a unique four amino acid insertion at the N-terminus of NS2.

Antigenic and genetic characterisation of border disease viruses isolated from UK cattle.

Available empirical data on the natural occurrence of ruminant pestiviruses has shown that in cattle, bovine viral diarrhoea virus (BVDV) is nearly exclusively found, whereas both border disease virus (BDV) and BVDV can be isolated from sheep. During routine genetic typing of pestivirus RNA from UK cattle diagnosed as BVDV positive between 2006 and 2008, five samples that were classified as BDV positive yielded positive virus isolates in cell cultures. The samples originated from animals that had shown signs typical for BVD. Phylogenetic analysis of the bovine BDVs showed that two belonged to the BDV-1a group and three to the BDV-1b group, thereby matching the genetic diversity seen for previously described UK ovine BDVs. Antigenic typing with a set of monoclonal antibodies (MABs) showed that all bovine BDVs lacked one or more epitopes conserved among ovine BDV-1 isolates, and that they had gained reactivity with at least one BVDV-1 specific MAB. Serial passaging of two of the virus isolates in ovine cell cultures did not change the epitope expression pattern. These findings suggest that the presumed natural resistance of cattle against infection with BDV no longer holds. A consequence of this is that BVD diagnostic assays should be checked for their ability to also detect BDV, and also highlights the need for monitoring of the BDV status in sheep that may be in contact with cattle in areas with organised BVD control programmes.

Mucosal lesions in a sheep infected with the Border Disease Virus (BDV).

A 28-week-old sheep was presented at the animal hospital because of chronic emaciation, anemia and slight diarrhea. Due to poor general condition and bad prognosis the animal was euthanized and submitted for postmortem investigation. Multiple erosions and ulcerations were found in the dorsal region of the tongue, the pharynx, the hard palate, in the esophagus and the ruminal pillars. Histologically, these lesions consisted of necrosuppurative inflammation. The animal was tested positive for pestivirus antigen both by immunohistochemical and by virological examination (cell culture, antigen capture ELISA and RT-PCR). A non-cytopathic Border Disease Virus was identified, and sequencing revealed a virus belonging to the BDV-3 cluster. Based on the macroscopical, histological, immunohistological and virological results this case was diagnosed as Border Disease with mucosal lesions. This is the first report of such a case in Switzerland.

Border disease virus among chamois, Spain.

Approximately 3,000 Pyrenean chamois (Rupicapra pyrenaica pyrenaica) died in northeastern Spain during 2005-2007. Border disease virus infection was identified by reverse transcription-PCR and sequencing analysis. These results implicate this virus as the primary cause of death, similar to findings in the previous epizootic in 2001.

Border disease virus (BDV) infections of small ruminants in Turkey: a new BDV subgroup?

Blood samples from sheep and/or goats from eight small ruminant flocks in the Turkish provinces of Aydin and Burdur were tested for the presence of Pestiviruses using an antigen-capture ELISA. From clinically affected animals, pathological and immunohistochemical findings were recorded. Post mortem examination of a virus-positive lamb showing abnormal fleece and paralysis of the hind legs revealed nonsuppurative meningoencephalomyelitis with hypomyelinogenesis. By immunohistochemistry Pestivirus antigen was detected in all parts of the brain including cerebellum, cerebral hemispheres and midbrain. Two Pestivirus isolates from a sheep and a goat kid, respectively, were isolated from samples that were positive in the antigen-capture ELISA. Genetic typing using the 5'-NTR (288bp) and N(pro) (738bp) showed that both were Border disease virus (BDV) isolates. By phylogenetic analysis, they formed a cluster clearly separated from the known clusters BDV-1 to BDV-6 and might therefore represent a new subgroup (BDV-7?). This is the first report confirming the occurrence and partial characterisation of BDV infection in small ruminants in Turkey.