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

Research Progress on Emerging Viral Pathogens of Small Ruminants in China during the Last Decade

China is the country with the largest number of domestic small ruminants in the world. Recently, the intensive and large-scale sheep/goat raising industry has developed rapidly, especially in nonpastoral regions. Frequent trading, allocation, and transportation result in the introduction and prevalence of new pathogens. Several new viral pathogens (peste des petits ruminants virus, caprine parainfluenza virus type 3, border disease virus, enzootic nasal tumor virus, caprine herpesvirus 1, enterovirus) have been circulating and identified in China, which has attracted extensive attention from both farmers and researchers. During the last decade, studies examining the etiology, epidemiology, pathogenesis, diagnostic methods, and vaccines for these emerging viruses have been conducted. In this review, we focus on the latest findings and research progress related to these newly identified viral pathogens in China, discuss the current situation and problems, and propose research directions and prevention strategies for different diseases in the future. Our aim is to provide comprehensive and valuable information for the prevention and control of these emerging viruses and highlight the importance of surveillance of emerging or re-emerging viruses.

First molecular evidence of border disease virus in wild boars in Turkey

Molecular studies on viral diseases in wildlife are limited in Turkey. Pestiviruses infect domestic animals such as pig, cattle, sheep, goats and many other wild ungulates. Cross-species transmission of pestiviruses between wildlife and domestic livestock is a subject of recent concern where wild ungulates are in close contact with domestic ruminants. The International Committee on Virus Taxonomy (ICTV) has named the genus Pestivirus, which belongs to the Flaviviridae family, using the format Pestivirus A, Pestivirus B, Pestivirus C, and so on. Pestivirus A-D replaces Bovine viral diarrhea virus-1 (BVDV-1), Bovine viral diarrhea virus-2 (BVDV-2), Classical swine fever virus (CSFV) and Border disease virus (BDV) respectively. During the 2013–2014 hunting season, a total of 40 samples were collected from wild boars (Sus scrofa ferus) in the area of Western Mediterranean Turkey. In the samples, nucleic acids were investigated for pestivirus, Aujeszky’s disease virus, Borna disease virus, coronavirus, mastadenovirus and rotavirus. RT-PCR was performed using primary sets to detect specific partial gene region specific to each virus. Sequence analysis was performed on a positive sample. Phylogenetic analysis revealed that the positive sample, TR/Burdur/13/Boar3, belonged to BDV genotype 1 (Pestivirus D). The first molecular findings of BDV in wild boars in Turkey are reported in this study. This study highlights the importance of further research into diseases that might be transmitted from wild boars to ruminants in Turkey.

In vitro Inhibition of Border Disease Virus Replication With Lentivirus-Mediated shRNAs

Background: Border disease is believed to be one of the most important diseases in the animal husbandry industry, which has not yet been eradicated in Iran. The development of approaches based on the application of interfering RNA (RNAi) for antiviral therapy has attracted a great deal of attention over the recent years. The present research was conducted to design, construct, and apply shRNA against the NS3 gene of BDV to evaluate the prevention of BDV proliferation in the cell culture system. For this purpose, the suitable oligonucleotide sequence of NS3 gene coding was selected utilizing BDV- X818 strain. Afterwards, using shRNA design software, shRNA molecules were designed and synthesized. These shRNAs were cloned into the desired vectors and were finally transfected in HEK293T cells employing the third generation of lentiviral packaging system. Subsequently, these shRNA expressing lentiviruses were transduced to the MDBK cell line to challenge to border virus. In order to evaluate the efficacy of shRNAs, the viral infectious titer and RNA copy number were calculated with TCID50 and Real-time RT-PCR tests, respectively. Results: The results revealed that shRNAs 1, 2, and 3 decreased viral RNA by more than 90% compared to the control groups. BDV titer noticeably decreased after the challenge with shRNAs 1, 2, and 3 from ~88% up to 99% in comparison with the control groups. Conclusions: Overall, it could be concluded that RNAi may be considered as a strong treatment proposal against viruses, such as BDV.

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.

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.

Distribution and Genetic Characterization of Border Disease Virus Circulating in Sardinian Ovine Flocks

Border Disease (BD) is a worldwide distributed pathology accountable for significant losses in the sheep and goat farming industry. The etiological agent is a Pestivirus within the family Flaviviridae called border disease virus (BDV). Despite the Sardinian ovine population being by far larger than any other Italian region, the prevalence and distribution of BD on the island are unknown. Here, we aim to determine the distribution of BDV in sheep flocks and to genetically characterize the circulating strains in Sardinia. The geographical distribution, antibody positivity, and viral genome presence have been analysed for 1286 sheep flocks distributed all over the island from bulk tank milk sampled between May 2014 and 2015. Of the flocks tested, 11.28% (95% CI 9.66–13.12) resulted positive for the presence of anti-pestivirus antibodies with an uneven distribution between Sardinian provinces. In addition, using RT-PCR, nine BDV genomes were amplified from milk pellets of the seropositive samples. Phylogenetic analysis revealed that all the viruses amplified clustered in the same group classified as BDV-7. This represents the first study on the distribution of pestivirus infection and genetic characterization of BDV strains circulating in the Sardinian sheep population. Future studies are needed to clarify the origin, the evolution, and the epidemiology of BDV-7 in Sardinia.

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.

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.

Influence of border disease virus (BDV) on serological surveillance within the bovine virus diarrhea (BVD) eradication program in Switzerland

BACKGROUND

In 2008, a program to eradicate bovine virus diarrhea (BVD) in cattle in Switzerland was initiated. After targeted elimination of persistently infected animals that represent the main virus reservoir, the absence of BVD is surveilled serologically since 2012. In view of steadily decreasing pestivirus seroprevalence in the cattle population, the susceptibility for (re-) infection by border disease (BD) virus mainly from small ruminants increases. Due to serological cross-reactivity of pestiviruses, serological surveillance of BVD by ELISA does not distinguish between BVD and BD virus as source of infection.

RESULTS

In this work the cross-serum neutralisation test (SNT) procedure was adapted to the epidemiological situation in Switzerland by the use of three pestiviruses, i.e., strains representing the subgenotype BVDV-1a, BVDV-1h and BDSwiss-a, for adequate differentiation between BVDV and BDV. Thereby the BDV-seroprevalence in seropositive cattle in Switzerland was determined for the first time. Out of 1,555 seropositive blood samples taken from cattle in the frame of the surveillance program, a total of 104 samples (6.7%) reacted with significantly higher titers against BDV than BVDV. These samples originated from 65 farms and encompassed 15 different cantons with the highest BDV-seroprevalence found in Central Switzerland. On the base of epidemiological information collected by questionnaire in case- and control farms, common housing of cattle and sheep was identified as the most significant risk factor for BDV infection in cattle by logistic regression.

CONCLUSION

This indicates that pestiviruses from sheep should be considered as a source of infection of domestic cattle and might well impede serological BVD surveillance.

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.

Evidence for Circulation of Bovine Viral Diarrhoea Virus Type 2c in Ruminants in Southern Italy

Recently, bovine viral diarrhoea virus type 2c (BVDV-2c) was responsible for a severe outbreak in cattle in northern Europe. Here, we present the results of an epidemiological survey for pestiviruses in ruminants in southern Italy. Pooled serum samples were obtained from 997 bovine, 800 ovine, 431 caprine and eight bubaline farms, and pestiviral RNA was detected by molecular methods in 44 farms consisting of 16 cattle and one buffalo herds and of 21 sheep and six goat flocks. Twenty-nine and 15 farms were infected by BVDV-1 and BVDV-2 strains, respectively. BVDV-1 strains were recovered mainly from cattle and were heterogeneous, belonging to the subtypes 1b, 1u, 1e, 1g and 1h. In contrast, all BVDV-2 viruses but two were detected in sheep or goats and were characterized as BVDV-2c by sequence analysis of 5'UTR. These strains displayed high genetic identity to BVDV-2c circulating in cattle in northern Europe and were more distantly related to a BVDV-2c isolate recovered from a cattle herd in southern Italy more than 10 years before. The circulation of a BVDV-2c in small ruminants suggests the need for a continuous surveillance for the emergence of pestivirus-induced clinical signs in southern Italian farms.

Genetic diversity of ruminant Pestivirus strains collected in Northern Ireland between 1999 and 2011 and the role of live ruminant imports

BACKGROUND

The genus pestivirus within the family Flaviviridae includes bovine viral diarrhoea virus (BVDV) types 1 and 2, border disease virus (BDV) and classical swine fever virus. The two recognised genotypes of BVDV are divided into subtypes based on phylogenetic analysis, namely a-p for BVDV-1 and a-c for BVDV-2.

METHODS

Three studies were conducted to investigate the phylogenetic diversity of pestiviruses present in Northern Ireland. Firstly, pestiviruses in 152 serum samples that had previously tested positive for BVDV between 1999 and 2008 were genotyped with a RT-PCR assay. Secondly, the genetic heterogeneity of pestiviruses from 91 serum samples collected between 2008 and 2011 was investigated by phylogenetic analysis of a 288 base pair portion of the 5' untranslated region (UTR). Finally, blood samples from 839 bovine and 4,437 ovine animals imported in 2010 and 2011 were tested for pestiviral RNA. Analysis of animal movement data alongside the phylogenetic analysis of the strains was carried out to identify any links between isolates and animal movement.

RESULTS

No BVDV-2 strains were detected. All of the 152 samples in the first study were genotyped as BVDV-1. Phylogenetic analysis indicated that the predominant subtype circulating was BVDV-1a (86 samples out of 91). The remaining five samples clustered close to reference strains in subtype BVDV-1b. Out of the imported animals, 18 bovine samples tested positive and 8 inconclusive (Ct ≥36), while all ovine samples were negative. Eight sequences were obtained and were defined as BVDV-1b. Analysis of movement data between herds failed to find links between herds where BVDV-1b was detected.

CONCLUSION

Given that only BVDV-1a was detected in samples collected between 1968 and 1999, this study suggests that at least one new subtype has been introduced to Northern Ireland between 1999 and 2011 and highlights the potential for importation of cattle to introduce new strains.

Evidence for Tunisian-Like Pestiviruses Presence in Small Ruminants in Italy Since 2007

The genus Pestivirus, which belongs to the Flaviviridae family, includes ssRNA+ viruses responsible for infectious diseases in pigs, cattle, sheep, goats and other domestic and wild ruminants. Like most of the RNA viruses, pestivirus has high genome variability with practical consequences on disease epidemiology, diagnosis and control. In addition to the officially recognized species in the genus Pestivirus, such as BVDV-1, BVDV-2, BDV and CSFV, other pestiviruses have been detected. Furthermore, most of the ruminant pestiviruses show low or absent species specificity observed in serological tests and are able to infect multiple species. Particularly, small ruminants are receptive hosts of the most heterogeneous group of pestiviruses. The aim of this study was to carry out the molecular characterization of pestiviruses isolated from sheep and goats in Sicily, Italy. Phylogenetic analysis of two viral genomic regions (a fragment of 5'-UTR and the whole N^pro regions) revealed the presence of different pestivirus genotypes in the analysed goat and sheep herds. Two of five viral isolates were clustered with BVDV-1d viruses, a strain widespread in Italy, but never reported in Sicily. The other three isolates formed a distinct cluster with high similarity to Tunisian isolates, recently proposed as a new pestivirus species. This represents the first evidence for Tunisian-like pestivirus presence in small ruminants in Italy. Furthermore, one of the isolates was collected from a goat, representing the first isolation of Tunisian-like pestivirus from this species.

The role of herpesviruses (BoHV-1 and BoHV-4) and pestiviruses (BVDV and BDV) in ruminant abortion cases in western Turkey

The economic impact of abortions in ruminant breeders is one of the biggest problems in livestock. Of the infectious agents, viruses, especially herpesviruses and pestiviruses, are the most important causative agents of abortion in ruminants. In the present study, the role of herpesviruses (bovine herpesvirus-1 (BoHV-1), bovine herpesvirus-4 (BoHV-4)) and pestiviruses (bovine viral diarrhea virus (BVDV), border disease virus (BDV)) was investigated in cases of ruminant abortion between 2007 and 2015 in western Turkey. Out of 81 aborted fetal samples (60 calves, 19 lambs, and 2 kids), 42 were positive, which included 31 calves, 9 lambs, and 2 goats; 39 aborted fetal samples were negative for the pestivirus antigen ELISA. BoHV-1 antigen ELISA was positive in 3 cases which included 2 calves and 1 lamb; the remainder 78 cases were negative. Pestivirus and BoHV-1 were positive in 51.85 and 3.70 %, respectively, of the samples. According to PCR analysis, BoHV-4 was not encountered in any of the tested samples. In one of the calf fetus samples, both BVDV and BoHV-1 were positive; in one of the lamb fetus samples, BoHV-1 was positive. There was a much higher level of pestivirus antigen than the other viral agents evaluated in the study (p < 0.0001). The results of this study indicate that pestiviruses are a common viral cause of ruminant abortions in the examined area.

Antigenic and molecular characterisation of Border disease virus associated with high mortality in lambs in Spain

Introduction

Border disease virus (BDV) causes congenital disorders in sheep and results in severe, but underestimated, economic losses worldwide. However, information about BDV strains affecting several ruminants worldwide is scarce. Therefore, antigenic and genetic classification of isolates from different geographical regions is important to enhance the knowledge of the epidemiology of BDV.

Materials and methods

Five pestiviruses isolated from lambs in an epidemic outbreak with an unusually high mortality in Spain in 1997 were characterised antigenically with a panel of monoclonal antibodies and genetically by sequencing within the 50 untranslated (50UTR) region of the genome.

Results

All the isolates were classified as BDV and showed a high homology with the Aveyron strain (Av), which was associated with an epidemic reported in sheep from the Aveyron region of France in 1984.

Conclusions

Classification of the isolates from this study provides valuable information on the molecular epidemiology of BDV.

The first case of a bull persistently infected with Border disease virus in New Zealand

CASE HISTORY

Poor reproductive performance was observed in 62 dairy heifers, with a pregnancy rate of 23% following 57 days mating with one 3-year-old and two 2-year old Belted Galloway bulls that were sourced from separate sheep and beef farms.

CLINICAL FINDINGS

The 3-year-old bull was small for its age with small testes. This bull was seropositive for bovine viral diarrhoea virus type I (BVDV 1) using an Ag-ELISA, and positive on PCR for border disease virus (BDV). DIAGNOSTIC INVESTIGATION: Phylogenetic analysis of the BDV isolate from the affected bull indicated that it was part of the BDV 1 group. For 40 of the heifers exposed to the bull that were tested, all of them had a positive VNT (virus neutralisation test) titre to both BDV (titre≥1:4) and BVDV 1 (titre>1:4). On the farm of origin of the affected bull there was no evidence of BDV circulating between cattle.

DIAGNOSIS

Persistent infection of a bull with BDV.

CLINICAL RELEVANCE

Cattle persistently infected with BDV can act as a source of virus for infection of other cattle. The benefit of testing cattle for bovine viral diarrhoea could be enhanced by using tests that also detect BDV.