Genetic Characterization of a Caprine Pestivirus as the First Member of a Putative Novel Pestivirus Subgroup

Identification of border disease virus in naturally infected pigs in Mexico

Border disease virus (BDV) is a pathogen primarily infecting sheep and goats; however, infections in cattle, pigs, and wild ruminants have also been reported. Interspecies transmission of BDV occurs through close contact among infected animals. In this case report, we describe the detection of BDV in tonsil, mesenteric ganglia, and blood samples from piglets with severe clinical disease. Genetic characterization of evaluated samples resulted in the identification of BDV genotype 1 in Mexico. This represents the first report of BDV detected in pig populations in Mexico. Therefore, circulation of this virus in nonruminant populations should not be discarded.

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.

Detection of Pestivirus in small ruminants in Central Java, Indonesia

Background and Aim:

Globally, pestiviruses are among the most economically important viral pathogens of livestock. The genus Pestivirus comprises four species, including bovine viral diarrhea virus type 1 and 2 (BVDV-1 and BVDV-2), which infect cattle, border disease virus and classical swine fever virus which infect small ruminants and pigs, respectively. Accumulating evidence suggests that pestiviruses are no longer species-specific, creating new challenges for disease control. In Indonesia, investigations related to pestiviruses remain focused on cattle as the primary host and no research has been conducted on small ruminants (sheep and goats). Therefore, the present study aimed to study the possible occurrence of pestivirus (BVDV or BVD) infections in small ruminants in Indonesia, particularly in Central Java.

Materials and Methods:

We used 46 blood samples consisting of 26 sheep’s blood and 20 goat’s blood. Samples were selected from 247 small ruminant blood collected between July and October 2020 in Central Java, Indonesia, which met the following criteria: Female, local species, approximately 1-2 years old, never been pregnant, raised in the backyard, and had no close contact with cattle in either shelter or grazing area. We tested plasma samples from sheep and goats using competitive antibody enzyme-linked immunosorbent assay to detect specific antibodies against pestivirus followed by reverse transcription-polymerase chain reaction (RT-PCR) analysis for all positive samples to differentiate the species of pestivirus.

Results:

Two of the 20 samples collected from goats were positive for pestivirus at the serological and molecular levels, whereas 2 of 26 samples collected from sheep were doubtful but tested negative by RT-PCR. The genotyping test results obtained using nested PCR revealed that the positive samples collected from goats had a BVDV-1 genotype.

Conclusion:

The results of the present study demonstrated that BVDV-1 can infect species other than bovines, in Central Java, Indonesia. Further studies involving a larger number of samples are required to: (1) Determine the actual seroprevalence of pestiviruses in small ruminants and (2) Determine the potency of small ruminants as reservoirs for pestiviruses, both of which are important for the identification of the appropriate control program for pestiviruses in Indonesia.

Near-complete nucleotide sequence of a border disease virus genotype BDV-7 isolate from Italy

To gain further insight into the genomic features of border disease virus (BDV), we determined the nearly complete genome sequence of isolate TO/121/04 from an aborted ovine fetus. Its genome contains a single open reading frame (ORF), which comprises 11,681 nucleotides encoding a polyprotein of 3893 amino acids. Phylogenetic analysis of the near full-length genome sequence showed that the BDV isolate differed significantly from all ovine pestiviruses identified so far, thus re-affirming the presence in Italy of this novel genetic group, termed BDV-7.

Pathogen spread and globalization: The case of Pestivirus heterogeneity in southern Italy

Pestiviruses are responsible for widespread diseases affecting cattle, pigs and other ruminants, presenting a wide range of clinical manifestations, with significant impact on animal production. Given the recent various reports of a relatively high number of new strains and atypical genomic variants, in the present study, ninety-seven genomic sequences from southern Italy have been evaluated applying the palindromic nucleotide substitutions method, based on 5'-UTR secondary structure alignment and computing genetic distance among strains in the internal ribosome entry site. Sequence analysis revealed a highly heterogeneous virus population, indicating the introduction of virus variants of Bovine viral diarrhea virus and Border disease virus species from foreign countries. The application of different analytical procedures was useful to avoid interpretation difficulties. Circulation of heterogeneous virus populations showed the need for more accurate epidemiological investigations and stringent veterinary controls to protect animal health and welfare.

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.

Proposed revision to the taxonomy of the genus Pestivirus, family Flaviviridae

We propose the creation of seven new species in the genus Pestivirus (family Flaviviridae) in addition to the four existing species, and naming species in a host-independent manner using the format Pestivirus X. Only the virus species names would change; virus isolates would still be referred to by their original names. The original species would be re-designated as Pestivirus A (original designation Bovine viral diarrhea virus 1), Pestivirus B (Bovine viral diarrhea virus 2), Pestivirus C (Classical swine fever virus) and Pestivirus D (Border disease virus). The seven new species (and example isolates) would be Pestivirus E (pronghorn pestivirus), Pestivirus F (Bungowannah virus), Pestivirus G (giraffe pestivirus), Pestivirus H (Hobi-like pestivirus), Pestivirus I (Aydin-like pestivirus), Pestivirus J (rat pestivirus) and Pestivirus K (atypical porcine pestivirus). A bat-derived virus and pestiviruses identified from sheep and goat (Tunisian sheep pestiviruses), which lack complete coding region sequences, may represent two additional species.

Detection of border disease virus in Mexican cattle

The genus Pestivirus within Flaviviridae is comprised of four recognized species, namely, bovine viral diarrhoea virus 1 (BVDV-1), bovine viral diarrhoea virus 2 (BVDV-2), border disease virus (BDV) and classical swine fever virus (CSFV). BDV, while primarily infecting sheep and goats, has also been reported in cattle and wild animals. Infections of sheep and goats result in economic loss due to abortions and the birth of persistently infected animals that have poor production and reduced life expectancy. In this study, we report the detection of BDV in cattle serum collected as part of pestivirus surveillance programme from six regions of Mexico, where a 67.1% of BVDV seroprevalence was calculated previously. Phylogenetic analyses based on comparison of the 5'UTR region typed the Mexican strains as BDV-1. Border disease (BD) is listed as an exotic disease in Mexico, and the origin of BDV found in these cattle is unclear. This is the first identification of BDV in Mexican cattle.

Pestiviral E(rns) blocks TLR-3-dependent IFN synthesis by LL37 complexed RNA

The ribonuclease activity of the soluble glycoprotein E(rns) of pestiviruses represents a unique mechanism to circumvent the host's innate immune system by blocking interferon type-I synthesis in response to extracellularly added single- (ss) and double-stranded (ds) RNA. However, the reason why pestiviruses encode a ribonuclease in addition to the abundant serum RNases remained elusive. Here, we show that the 5' UTR and NS5B regions of various strains of the RNA genome of the pestivirus bovine viral diarrhea virus (BVDV) are resistant to serum RNases and are potent TLR-3 agonists. Inhibitory activity of E(rns) was restricted to cleavable RNA products, and did not extend to the synthetic TLR-7/8 agonist R-848. RNA complexed with the antimicrobial peptide LL37 was protected from degradation by E(rns)in vitro but was fully inhibited by E(rns) in its ability to induce IFN in cell cultures, suggesting that the viral protein is mainly active in cleaving RNA in an intracellular compartment. We propose that secreted E(rns) represents a potent IFN antagonist, which degrades viral RNA that is resistant to the ubiquitous host RNases in the extracellular space. Thus, the viral RNase prevents its own pathogen-associated molecular pattern (PAMP) to inadvertently activate the IFN response that might break innate immunotolerance required for persistent pestivirus infections.

Serological evidence for BVDV-1 infection in goats in Poland - short communication

A serological survey was conducted in 2007 in the breeding goat population in Poland to gain insights into the epidemiology of pestivirus infection. All breeding herds were included in the study and representative serum samples were taken in each herd to evaluate herd-level seroprevalence at 10% expected individual-level prevalence and 95% level of confidence. Altogether 1060 serum samples from 49 herds were tested with blocking ELISA and then the positive and inconclusive results were confirmed in a serum neutralisation test, which also allowed us to determine the pestivirus species responsible for seroconversion. Herd-level seroprevalence proved to be 10.2% and bovine viral diarrhoea virus type 1 (BVDV-1) was responsible for the seroconversion in seven out of eight cases. In the remaining serum sample the causative virus could not be identified due to a pronounced cross-neutralising activity possibly derived from multiple infections. This is the first report on the diagnosis of BVDV-1 infection in Polish goats.

Complementation studies with the novel "Bungowannah" virus provide new insights in the compatibility of pestivirus proteins

In recent years several atypical pestiviruses have been described. Bungowannah virus is the most divergent virus in this group. Therefore, heterologous complementation was used to clarify the phylogenetic relationship and to analyze the exchangeability of genome regions encoding structural proteins. Using a BVDV type 1 backbone, chimeric constructs with substituted envelope proteins E(rns), E1 and E2, were investigated. While all constructs replicated autonomously, infectious high titer chimeric virus could only be observed after exchanging the complete E1-E2 encoding region. The complementation of E1 and E2 alone resulted only in replicons. Complementation of BVDV-E(rns) was only efficient if Bungowannah virus-E(rns) was expressed from a bicistronic construct. Our data provide new insights in the compatibility of pestivirus proteins and demonstrate that heterologous complementation could be useful to characterize new pestiviruses.

Molecular detection of pestiviruses in aborted foetuses from provinces in northern Turkey

All pestiviruses are important veterinary pathogens causing economic losses in cattle, sheep and pigs. Besides the important economical losses, pestiviruses may compromise the normal immune response to other pathogens and increase the severity of other infections in sheep. In this study, aborted foetuses (cattle and sheep) in either coastal or inland Black Sea region of Turkey were surveyed for the presence of RNA from pestiviruses (bovine viral diarrhoea virus (BVDV), border disease virus (BDV)). The presence of BVDV RNA was found in 6 of 21 aborted calves (28.57%), although BDV RNA was detected in 14 of 21 aborted lambs (66.66%) by reverse transcriptase polymerase chain reaction. This study also investigates the distribution of viral RNA within the brain, liver and lung of aborted foetuses. The viral RNA positivity rates for the organs varied and were as follows: brain 40.47% and liver and lung 38.09%. The results revealed that pestiviruses are important abort pathogen in the provinces of northern Turkey.

Experimental infection of pigs with Border disease virus isolated from Pyrenean chamois (Rupicapra pyrenaica)

Between 2001 and 2007, several outbreaks of disease associated with Border disease virus (BDV) infection were reported in the central Pyrenees (northeast Spain) and were associated with a major reduction in chamois (Rupicapra pyrenaica) populations. At the same time, wild boars (Sus scrofa) from the same area were found to be seropositive to this pestivirus, without showing clinical signs. The present study examines the susceptibility of domestic swine and the course of the infection with a BDV strain isolated from naturally infected chamois. Twenty pigs were inoculated with 1 x 10(7) TCID(50) (50% tissue culture infective dose) by oronasal route, and 16 control pigs received Eagles sterile Minimal Essential Medium. Serologic (enzyme-linked immunosorbent assay and virus neutralization test) and reverse transcription polymerase chain reaction assays were performed on serum samples obtained at 0, 3, 7, 10, 14, 21, and 31 days postinoculation (dpi). All infected pigs were viremic from 3 to 14 dpi. After 14 dpi, all infected animals developed an antibody response against the homologous virus. Clinical signs or histologic lesions were not observed in inoculated pigs. The present work demonstrates the susceptibility of domestic swine to a BDV strain of chamois origin.

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.

Neuropathologic Study of Border Disease Virus in Naturally Infected Fetal and Neonatal Small Ruminants and Its Association With Apoptosis

The present study describes the pathologic changes and cellular apoptosis in the central nervous system (CNS) of fetal and neonatal small ruminants infected with border disease virus (BDV), as demonstrated by immunohistochemistry and in situ hybridization. Abortions of ewes and goats were observed, as were births of lambs and kids with poor survival rates and nervous signs. Lesions included cerebellar hypoplasia, porencephaly, hydranencephaly, and nonsuppurative meningoencephalomyelitis with hypomyelinogenesis. Viral antigens and RNA were present in neuropil, glial, and neuronal cells, especially in periventricular areas, cerebellum, and brainstem. TUNEL positivity and labeling of anti-bax and anti-caspases 3, 8, and 9 were detected in BDV-infected CNSs, especially in glial and neuronal cells. The double immunostaining and TUNEL assay revealed that in BDV-infected animals, not only were BDV-infected glial and neuronal cells undergoing apoptosis, but so were uninfected cells in close vicinity of BDV-infected cells. The expression of activated caspases 3, 8, 9; bax; and TUNEL in glial and neuronal cells of the infected fetal and neonatal kids were significantly ( P < .05) higher than those of the infected fetal and neonatal lambs. Yet, the expression of bcl-2 in the CNSs of the infected fetal and neonatal lambs was higher ( P < .05) in neuronal and glial cells than in those of the infected fetal and neonatal kids. The results suggest that cell death in the BDV-infected CNS is induced by intrinsic and extrinsic cascades of apoptotic pathways.

Pestivirus infection in sheep and goats in West Austria

Blood samples from 3112 sheep (185 flocks) and 1196 goats (163 flocks) from the Western region of Austria were tested for pestivirus-specific RNA. In this area, communal Alpine pasturing of sheep, cattle and goats is an important part of farming. The prevalence of sheep persistently-infected (PI) with pestivirus was 0.32% (10 animals) and the PI animals originated from five flocks (2.7% of those investigated). In goats, only one PI animal (0.08%) was detected. Sequence analysis of the 5'-end untranslated region (UTR) revealed that the strains of Border disease virus (BDV) detected were closely related to genotype 3 but the PI animals did not show any clinical signs of Border disease. The goat was PI with bovine viral diarrhoea virus-1 (BVDV-1). On one farm a high abortion rate among sheep had been observed 1year before the study was carried out but the other farms did not show any evidence of reproductive failures. Pestiviruses are endemic in small ruminants in some Alpine regions of Austria and PI healthy animals as described here have a key epidemiological role. A successful BVDV eradication programme in Austria will create highly pestivirus-susceptible cattle populations. Sheep and goats present a high risk for the reintroduction of pestiviruses to cattle herds because they are less likely to be considered to be PI. The results underline the need for the immediate consideration of small ruminants in eradication programmes.

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.

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.

Genetic and antigenic characterization of bovine viral diarrhea virus type 2 isolated from Indian goats (Capra hircus)

Recent studies have shown that bovine viral diarrhea virus (BVDV) type 1 is widely prevalent in Indian cattle. In a surveillance of randomly collected 562 blood samples from seven states during 2004-2006, BVDV type 2 was detected in two native Indian goats by nested reverse transcription polymerase chain reaction (nRT-PCR). The virus isolated from them was classified antigenically as BVDV 2 on the basis of virus neutralization test and reactivity with monoclonal antibodies. Phylogenetic analysis of three different genomic regions, 5' un-translated region (5' UTR), E(rns) structural coding region and NS5B nonstructural coding region typed Indian goat isolate as BVDV 2a having close similarity with strains from North America and Europe suggesting its probable introduction through trade. It was placed in a separate clade within the 2a branch having unique mutations in E(rns) and NS5B region. This is the first report of BVDV 2 in India and only second time recorded in goat species. The isolation of BVDV 2 from goat warrants intensive surveillance in cattle and sheep.

Genetic and antigenic typing of border disease virus isolates in sheep from the Iberian Peninsula

A selection of 10 pestiviruses isolated from sheep from the Iberian Peninsula from 2001 to 2004 was characterised at the molecular level. The 5' untranslated region (5'-UTR) and N(pro)-coding gene were amplified by the reverse transcription-polymerase chain reaction (RT-PCR) and sequenced directly from purified products. All isolates were also typed antigenically with a panel of monoclonal antibodies (mAbs) raised against representative isolates of the four recognised pestivirus species. The genetic typing placed all the isolates in a new tentative type 4 of border disease virus (BDV), which was closely related to a pestivirus recently found in Pyrenean chamois (Rupicapra pyrenaica pyrenaica). Overall, the genotyping indicated a relatively wide diversity of the BDV type 4, which was best defined on the basis of N(pro) sequences. Antigenically, the isolates were recognised by two pan-pestivirus specific anti-NS3 mAbs, but only by some of the anti-glycoprotein specific mAbs raised against BDV, indicating partial antigenic overlap with other BDV isolates.

Influence of Communal Alpine Pasturing on the Spread of Pestiviruses among Sheep and Goats in Austria: First Identification of Border Disease Virus in Austria

The purpose of this investigation was to determine the influence of communal Alpine pasturing on the spread of pestivirus infections among sheep and goats. The study included 481 sheep from 23 farms and 131 goats from 26 farms pastured on separated Alpine meadows in the western part of Austria. At the starting of pasturing on the sheep meadow, 325 (67.6%) animals were seropositive, on the goat meadows in 16 (12.2%) samples antibodies to pestiviruses were detected. At the end of pasturing, 74 seronegative sheep and two seronegative goats had seroconverted. Between the beginning and the end of pasturing the seroprevalence in sheep increased significantly from 67.6% to 83% (P<0.05). Moreover, in the peripheral blood mononuclear cells of four sheep, pestivirus-specific RNA was detected before as well as after pasturing; these animals remained serologically negative throughout the investigation. They were, therefore, identified as persistently infected. Sequence analysis in the N(pro) region revealed that the detected pestiviruses were the same at genetic level and they were grouped into the Border disease virus (BDV)-3 genotype. No pestivirus RNA was found in goat samples. The results of this survey indicate that communal Alpine pasturing does play a key role in the spread of BDV. Moreover, BDV has been identified and characterized for the first time in sheep in Austria, which until then had been regarded as being free from BD.

Identification of Bovine Viral Diarrhea Virus type 2 in Korean native goat (Capra hircus)

In the genus Pestivirus, four genetically distinct viral species are currently recognized: bovine viral diarrhea viruses type 1 and 2 (BVDV-1, BVDV-2), classical swine fever virus (CSFV) and border disease virus (BDV). BVDV-1 and BDV infections have been described in goat species. Since 1998, border disease (BD) like symptoms in goats have been reported repeatedly in two southern-most provinces of Korea, which until then had been regarded as being free from BD. As a result of retrospective investigations of BD-like syndrome in goat reported between 1998 and 2004, a pestivirus was identified from intestinal content of an affected kid submitted in 1999. Both sequences of 5'-non-coding region and complete N(pro) gene from the isolate were analyzed to identify the genotype. Interestingly, the results revealed that the isolate belonged to BVDV-2 that is rarely reported even in cattle. The isolate showed close relationship to North American and European strains rather than the geographically closer Japanese strains. To authors' knowledge, this is the first identification of BVDV-2 in goat species.

Genetic typing and prevalence of Border disease virus (BDV) in small ruminant flocks in Spain

Between 2001 and 2002, samples from 1,413 animals in 21 Spanish small ruminant flocks, most of them with animals showing clinical signs compatible with Border disease (BD), were screened for the presence of Pestivirus antigen and antibodies by an indirect peroxidase monolayer assay (IPMA) and the virus neutralization test (VNT), respectively. Although all flocks harboured seropositive animals, virus could only be isolated from animals in five of the flocks. Between 4 and 11 months later all animals older than 6 months in three of the flocks were resampled. At this time, 51-83% of them had neutralizing antibodies. The prevalence of persistently infected (PI) animals within two of the flocks was 0.3 and 0.6%, respectively. The third flock presumably had eliminated all the PI animals. Fourteen virus isolates were obtained. The 5' untranslated region (5'UTR) was amplified by RT-PCR and directly sequenced. Phylogenetic analyses classified them as a group of Border disease viruses (BDV), separated from BDV-1, but showing a relatively low bootstrap value. Three of the 14 isolates were in the same subgroup as a set of formerly characterised Spanish isolates from the Basque Country, which were allocated to subgroup BDV-C. In addition, they were in the group with an isolate from chamois, which is currently allocated in group BDV-4. Because of its close relation to the chamois isolate, these isolates were tentatively reallocated in a subgroup BDV-4a. The remaining isolates generated a new subgroup, related but not in the same cluster as the chamois isolate, and was therefore tentatively assigned to a new subgroup BDV-4b. Our results show that classification and nomenclature of BDV needs to be harmonised.

Pestiviruses in wild animals

Pestiviruses are not strictly host-species specific and can infect not only domestic but also wild animals. The most important pestivirus, CSFV, infects domestic pigs and wild boars, which may cause a major problem for successful CSFV eradication programmes. Mainly BVDV specific antibodies have been reported in captive and free-living animals. Virus has been isolated from some of these animal species, but since BVDV can contaminate cell cultures and foetal calf serum, early reports of BVDV isolation have to be considered with caution. Genetic typing of early pestivirus isolates from wild species revealed that the majority were BVDV-1. Of the pestiviruses identified so far three species (CSFV, BVDV-1, giraffe pestivirus) and three genotypes (BDV-2, BDV-4, pronghorn) appear to circulate in wildlife animal populations. The potential for pestiviruses to spread between farm animals and free-living animals is discussed as are epidemiological and technical problems, and the future direction of research.