Genetic diversity of pestivirus isolates in cattle from Western Austria

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.

Non-Bovine Species and the Risk to Effective Control of Bovine Viral Diarrhoea (BVD) in Cattle

Bovine viral diarrhoea virus (BVDV) is an economically important and highly prevalent virus of domestic cattle. Infections with BVDV may lead to both, reproductive and immunological effects that can result in widespread calf losses and increased susceptibility to diseases, such as mastitis and respiratory disease. While BVDV is generally considered to be host specific, it and other Pestivirus species, such as Border disease virus (BDV) in sheep, have been shown to be infecting species other than those from which they were originally isolated from. Recently BVDV was placed on the OIE’s list of notifiable disease and control and eradication programmes for BVDV have been developed throughout much of Europe, the United States, and the United Kingdom. While some countries, including Sweden and Ireland have successfully implemented eradication programmes, other countries such as New Zealand and Australia are still in the early stages of BVDV control. Despite effective control methods, incursions of BVDV into previously cleared herds still occur. While the cause of these incursions is often due to lapses in control methods, the ability of ruminant pestiviruses to infect species other than cattle poses the question as to whether non-bovine species could be impeding the success of BVDV eradication and control. As such, the aim of this review is to make mention of what is known about the cross-species transmission of BVDV, BDV and other pestiviruses between cattle and non-bovine ungulate species and draw conclusions as to the risk non-bovine species pose to the successful control and eradication of BVDV from cattle.

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.

Increased genetic variation of bovine viral diarrhea virus in dairy cattle in Poland

Background

Bovine viral diarrhea virus (BVDV) causes severe economic losses and is one of the most important viral pathogens of ruminants worldwide. The infection manifests itself in a variety of clinical symptoms. Phylogenetic studies based mainly on 5’UTR of its genome, identified many different subtypes of BVDV. Previous study indicated the predominance of BVDV-1b and BVDV-1d in Poland. The aim of this study was to genotype BVDV isolates currently circulating in Polish dairy herds.

Results

BVDV was detected in 30 herds. Viral subtypes were identified using sequences of the 5’UTR fragment and they were confirmed within a fragment of the N^pro region. Seven subtypes of BVDV-1 species have been identified: 1b, 1 g, 1f, 1d, 1r, 1 s and 1e.

Conclusion

The number of subtypes of BVDV in Poland evolves and 2 new subtypes have been identified for the first time. Such studies may have a positive impact on successful eradication of the virus using effective vaccines and diagnostic tests.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2029-z) contains supplementary material, which is available to authorized users.

Development and evaluation of real-time RT-PCR using ear hair for specific detection of sheep persistently infected with border disease virus (BDV)

The aim of this study was to develop an improved border disease virus (BDV) specific real time RT-PCR and to evaluate its performance on manually plucked hairs from sheep persistently infected with BDV that may act as a non-invasive alternate sample. The BDV real time RT-PCR assay reported here showed a high analytical sensitivity (10^0.6 TCID50/ml), specificity (no reactivity with BVDV-1, BVDV-2, HoBi-like pestivirus and CSFV) and reproducibility. When the assay was validated on 210 samples from BDV-infected and uninfected sheep, it showed a 100% diagnostic sensitivity and specificity with virus isolation. Further evaluation of the assay on manually plucked hair follicles from ear (mid-lateral, mid-medial) and tail tip from sheep persistently infected with BDV showed that a minimum of 20 hair follicles need to be tested for correct diagnosis of BDV. The BDV load was comparatively higher in hairs from mid-medial ear than those from other tested locations. Evaluation on other samples from PI sheep demonstrated that the test performance was similar to that of pestivirus generic real-time RT-PCR, but improved than the currently available BDV specific real-time RT-PCR. Although more number of PI animals need to be evaluated, the results of the study showed that manually plucked hairs from mid-medial ear pinna is a suitable alternative sample in real-time RT-PCR for detection of BDV persistently infected sheep. Use of the non-invasive ear hair samples and the improved BDV specific real-time RT-PCR reported here may be useful for BDV surveillance in several sheep rearing countries.

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.

Traces of history conserved over 600 years in the geographic distribution of genetic variants of an RNA virus: Bovine viral diarrhea virus in Switzerland

The first records of smallpox and rabies date back thousands of years and foot-and-mouth disease in cattle was described in the 16th century. These diseases stood out by their distinct signs, dramatic way of transmission from rabid dogs to humans, and sudden appearance in cattle herds. By contrast, infectious diseases that show variable signs and affect few individuals were identified only much later. Bovine viral diarrhea (BVD), endemic in cattle worldwide, was first described in 1946, together with the eponymous RNA virus as its cause. There is general agreement that BVD was not newly emerging at that time, but its history remains unknown. A search for associations between the nucleotide sequences of over 7,000 BVD viral strains obtained during a national campaign to eradicate BVD and features common to the hosts of these strains enabled us to trace back in time the presence of BVD in the Swiss cattle population. We found that animals of the two major traditional cattle breeds, Fleckvieh and Swiss Brown, were infected with strains of only four different subgenotypes of BVDV-1. The history of these cattle breeds and the events that determined the current distribution of the two populations are well documented. Specifically, Fleckvieh originates from the Bernese and Swiss Brown from the central Alps. The spread to their current geographic distribution was determined by historic events during a major expansion of the Swiss Confederation during the 15th and 16th centuries. The association of the two cattle populations with different BVD viral subgenotypes may have been preserved by a lack of cattle imports, trade barriers within the country, and unique virus-host interactions. The congruent traces of history in the distribution of the two cattle breeds and distinct viral subgenotypes suggests that BVD may have been endemic in Switzerland for at least 600 years.

Genetic diversity of Bovine Viral Diarrhea Virus from cattle in Chile between 2003 and 2007

BACKGROUND

Bovine Viral Diarrhea Virus causes significant economic losses in cattle. BVDV has high genomic diversity, with two species, BVDV-1 and BVDV-2, and at least twenty-one subgenotypes for BVDV-1 and four subgenotypes for BVDV-2. Vaccines are important tools to reduce the economic losses caused by this virus. However, vaccine strains must correspond to the antigenic profile of the viruses present in the region where the vaccine is applied. A restricted phylogenetic study with 14 viruses isolated from cattle between 1993 and 2001 showed that the genetic profile of BVDV in Chile consisted of viruses of both species and sub-genotypes 1a, 1b, 1c (currently 1j) and 2a. To determine more accurately the genetic profile of BVDV in Chile, in this study a larger number of viruses obtained from bovines between 2003 and 2007 were typed.

RESULTS

The study was performed using partial sequences from the 5' noncoding region (5'UTR) and E2 coding region of the viral genome of thirty-five Chilean viruses isolated from geographic regions that have 84.6% of the Chilean cattle. All tested viruses belonged to species BVDV-1. Eighteen viruses belonged to BVDV-1j subgenotype (51.4%), twelve belonged to BVDV-1b (34.3%) and five belonged to BVDV-1a (14.3%). The Chilean BVDV-1j viruses showed low genetic diversity, both among themselves and with the BVDV-1j present in other regions of the world. This could be explained by a relatively recent introduction of this viral subgenotype in cattle, which agrees with its low geographical distribution worldwide. Otherwise, Chilean BVDV-1b viruses grouped into a single cluster, different even than the viruses present in Argentina and Brazil, countries geographically close to Chile, a process of local evolution that could generate antigenic differences between the Chilean viruses and the viruses used as vaccine strains.

CONCLUSIONS

The high presence of viruses of the BVDV-1j subgenotype, which show major antigenic differences with BVDV-1a and BVDV-1b subgenotypes used in the commercial vaccines, suggest that BVDV-1j viruses could be an emergent subgenotype of BVDV in cattle in South America and suggest evaluating an update of the vaccines used in Chile.

Evidence of BVDV in Pigs from North Eastern Part of India- Genetic Profiling and Characterisation

Introduction:

The work has been attempted to detect and genetically characterise the nature of Bovine Viral Diarrhea Virus (BVDV) isolates from the porcine population of the north east.

Methods and Material:

The samples have been collected over a two year period and are from areas where there is a mixed and integrated rearing of livestock in close proximity. The isolates were identified, cloned and sequenced using BVD specific genomic primers for two important domains viz., E-2 and 5’ UTR.

Results:

Porcine BVD Sequences were analysed phylogenetically. Divergence in 3 sequences is noted in the 5’ UTR region that are forming a clear outlier group while E-2 sequences are coming close to BVDV group but forming a separate cluster.

Who's who in the Bovine viral diarrhea virus type 1 species: Genotypes L and R

The bovine viral diarrhea virus type 1 species is responsible for cosmopolitan diseases affecting cattle and other ruminants, with relevant impact on animal production. The species presents high genomic heterogeneity, with implications on control and prophylactic programs. Genomic traits of different genetic groups are often related to geographic origin. Atypical sequences have been reported from Pestivirus isolates originated from cattle in Turkey. Based on phylogenetic analysis of 5' untranslated region and Npro and secondary structure analysis of the 5'-UTR RNA, Turkish isolates have been segregated in two distinct genotypes. Out of the twenty-three identified BVDV-1 genotypes, the Turkish clusters, named L and R or 1.16 and 1.14, according to palindromic nucleotide substitution genotyping method, represent genomic clusters so far, not described elsewhere, suggesting geographic segregation. In order to avoid confusion in the current taxonomy of the species, nomenclature of described homonymous genotypes, referred to different genomic clusters, should be corrected.

Insemination with border disease virus-infected semen results in seroconversion in cows but not persistent infection in fetuses

BACKGROUND

This study examined various health variables in cows after artificial insemination with Border disease virus (BDV)-infected semen and the occurrence of persistent infection in ensuing fetuses. Five cows were inseminated (day 0) with BDV-infected semen as well as with semen from a fertile Eringer bull. One cow, inseminated with virus-free semen only, served as a control. Clinical examination, assessment of eating and rumination activities, measurement of intraruminal temperature and leukocyte count were used to monitor the health of the cows. Blood samples were collected at regular intervals for the detection of viral RNA and antibodies against BDV, and the cows were slaughtered on day 56. The uteri, placentae and fetuses were examined macroscopically, histologically, immunohistochemically and by means of molecular methods for the presence of pestiviruses.

RESULTS

The demeanour, eating and rumination activities and intraruminal temperature were not affected by insemination with BDV-infected semen, whereas the total leukocyte and lymphocyte counts dropped transiently and were significantly lower on day 6 than on day 0. Seroconversion occurred by day 28 in the five infected cows but not in the control cow. The uteri, placentae and fetuses had no macroscopic or histological lesions, and immunohistochemical examination and RT-PCR were negative for pestiviruses.

CONCLUSIONS

The findings showed that cows inseminated with BDV-infected semen seroconverted and fetuses thus produced were not persistently infected. Transmission of BDV to cattle through infected semen, therefore, seems to be of minor importance.

Bovine viral diarrhea virus type 1 current taxonomy according to palindromic nucleotide substitutions method

Pestivirus bovine viral diarrhea virus type 1 species is responsible for cosmopolitan diseases affecting cattle and other ruminants, presenting a wide range of clinical manifestations, with relevant impact on zootechnic production. Understanding genomic characteristic and virus taxonomy is fundamental in order to sustain control and prophylactic programs. Given the recent various studies reporting a relatively high number of new strains, in particular from Asian countries, in the present study, four hundred-eighty-two genomic sequences have been evaluated applying the palindromic nucleotide substitutions method for genotyping. Based on the secondary structure alignment and computing genetic distance among strains in the 5' untranslated region of Pestivirus RNA, the current taxonomy of the species was reviewed. Twenty-two genotypes have been identified, applying a nomenclature based on divergence in the genus.

Highlighting priority areas for bovine viral diarrhea control in Italy: A phylogeographic approach

The prevalence and genetic diversity of bovine viral diarrhea virus (BVDV) in a geographic area are largely influenced by live animal trade and management practices. Despite control and eradication programs currently underway in several European countries, the risk of BVDV spread within and among countries is still present. BVDV-1 is the predominant type circulating in European cattle population. In this study, a phylogeographic analysis was applied to the BVDV-1 highest prevalent subtypes in Italy to reconstruct the origin and spatial-temporal distribution and to trace main viral flows between different locations to highlight priority areas for BVDV control. A comprehensive dataset of BVDV-1b (n = 173) and 1e (n = 172) 5' UTR sequences was analysed, including both novel and published sequences from Italy and from European countries bordering and/or with commercial cattle flows with Italy. A common phylogeographic pattern was observed for BVDV-1b and 1e subtypes: interspersion from multiple Italian areas and European countries was widespread until the end of the last century, whereas significant local clusters were observed starting from 2000. These findings support a continuous viral flow among different areas over long time scales with no evidence of significant geographical structure, while local transmission networks are limited to more recent years. Northern Italy has been confirmed as the area of origin of the main clades of both BVDV subtypes at national level, acting both as a crucial area for introduction and a maintenance source for other areas. Piedmont, Central and Southern Italian regions contributed to limited geographical distribution and local BVDV-1b and 1e persistence. On the whole, priority control measures for BVDV-1b and 1e in Italy should be focused on: i) implementation of BVDV systematic control in all Northern Italian regions to break the viral flow from larger to smaller animal populations; and ii) breaking the dynamics of infections in regions with self-maintenance of BVDV by voluntary control programs.

Cycluridine: A novel antiviral effective against flaviviruses

This review describes the contemporary state of research for antivirals effective against flaviviruses, especially focusing on inhibitors of the pestivirus causative agent of bovine viral diarrhoea virus. We highlight cycluridine, an originally synthesized Mannich’s base [a tetrahydro-2(1H)-pyrimidinones derivative], as a highly effective antiviral possessing a strong inhibitory effect on bovine viral diarrhoea virus replication. Cycluridine was active against replication of a wide variety of bovine viral diarrhoea virus strains in cell cultures. The drug-sensitive period in the bovine viral diarrhoea virus replication cycle included the latent period and the exponential phase; a 90-min delay in the peak of viral RNA synthesis was observed. Cycluridine administered orally manifested a pronounced protective effect in calves with natural mucosal disease/viral diarrhoea and calves experimentally infected with bovine viral diarrhoea virus. Its magnitude of activity and selectivity places cycluridine in the lead among all known substances with anti- bovine viral diarrhoea virus activity. Additionally, cycluridine applied subcutaneously showed anti-tick-born encephalitis virus activity, manifesting a marked protective effect in mice infected with tick-born encephalitis virus. Cycluridine could be a prospective antiviral in veterinary and medical practice for the treatment of bovine viral diarrhoea virus and other flavivirus infections.

Variability and Global Distribution of Subgenotypes of Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is a globally-distributed agent responsible for numerous clinical syndromes that lead to major economic losses. Two species, BVDV-1 and BVDV-2, discriminated on the basis of genetic and antigenic differences, are classified in the genus Pestivirus within the Flaviviridae family and distributed on all of the continents. BVDV-1 can be segregated into at least twenty-one subgenotypes (1a–1u), while four subgenotypes have been described for BVDV-2 (2a–2d). With respect to published sequences, the number of virus isolates described for BVDV-1 (88.2%) is considerably higher than for BVDV-2 (11.8%). The most frequently-reported BVDV-1 subgenotype are 1b, followed by 1a and 1c. The highest number of various BVDV subgenotypes has been documented in European countries, indicating greater genetic diversity of the virus on this continent. Current segregation of BVDV field isolates and the designation of subgenotypes are not harmonized. While the species BVDV-1 and BVDV-2 can be clearly differentiated independently from the portion of the genome being compared, analysis of different genomic regions can result in inconsistent assignment of some BVDV isolates to defined subgenotypes. To avoid non-conformities the authors recommend the development of a harmonized system for subdivision of BVDV isolates into defined subgenotypes.

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.

Complete Genome Sequence of a Bovine Viral Diarrhea Virus Subgenotype 1e Strain, SLO/2407/2006, Isolated in Slovenia

Bovine viral diarrhea virus (BVDV) subgenotype 1e was isolated for the first time in Slovenia in 2006. Here, we report the complete genome sequence of BVDV-1e, strain SLO/2407/2006. The published genome will increase our understanding of the molecular characteristics of the BVDV-1e strains circulating in Europe.

Genetic typing of bovine viral diarrhoea virus in cattle on Irish farms

The aim was to carry out a phylogenetic study of bovine viral diarrhoea viruses (BVDV) circulating in Irish cattle herds from 2011 to 2014. Three hundred and twenty five viruses from 267 herds were subtyped by nucleotide sequence analysis of the 5'UTR and/or the N^pro regions. All viruses investigated in this study belonged to species BVDV-1 with BVDV-1a as the prominent subtype (97%). Subtypes BVDV-1b, BVDV-1d and BVDV-1e were also identified for the first time in Ireland. Pairwise alignments of 225 viruses with complete sequences for the 5'UTR and the N^pro regions were performed to determine a low conflict threshold for virus strain demarcation. One hundred and seventy seven unique virus strains were identified. The study revealed significant levels of herd specific clustering of strains but no geographical or temporal clustering. Similar virus strains were identified in different counties, provinces and years indicating the potential to investigate the epidemiology of the disease by combining sequence analysis with animal movement data.

Complete Genome Sequence of a Bovine Viral Diarrhea Virus Subgenotype 1e Strain Isolated in Switzerland

We sequenced the complete genome of the bovine viral diarrhea virus (BVDV) strain Carlito. It belongs to the subgenotype 1e that is described in Europe only and represents the second most prevalent subgenotype in Switzerland. This is the first report of a full-length sequence of BVDV-1e.

Transmission of border disease virus from a persistently infected calf to seronegative heifers in early pregnancy

Background

This study describes the transmission of border disease virus (BDV) from a persistently infected calf to seronegative heifers in early pregnancy, resulting in persistently infected fetuses. On day 50 of pregnancy (= day 0 of the infection phase), six heifers were co-housed in a free stall with a bull calf persistently infected with BDV (pi BVD) for 60 days. The heifers underwent daily clinical examination, and blood samples were collected regularly for detection of pestiviral RNA and anti-pestivirus antibodies. After day 60 (= day 110 of pregnancy), the heifers were slaughtered, and the fetuses and placentae underwent post-mortem and immunohistochemical examination and RT-PCR for viral RNA detection.

Results

Three heifers had mild viraemia from day 8 to day 14, and by day 40 all heifers had pestivirus antibodies identified as anti-BDV antibodies in the serum neutralisation test. The placenta of the three viraemic heifers had histological evidence of inflammation, and fetal organs from these heifers were positive for pestivirus antigen by immunohistochemical examination and for BD viral RNA by RT-PCR and sequencing. Thus, co-housing of heifers in early pregnancy with a pi-BDV calf led to seroconversion in all heifers and persistent fetal infection in three.

Conclusions

Considering that pi-BDV cattle can infect other cattle and lead to persistent infection of the fetus in pregnant cows, BDV should not be ignored in the context of the mandatory BVDV eradication and monitoring program. This strongly suggests that BDV should be taken into account in BVD eradication and control programs.

Extended genetic diversity of bovine viral diarrhea virus and frequency of genotypes and subtypes in cattle in Italy between 1995 and 2013

Genetic typing of bovine viral diarrhea virus (BVDV) has distinguished BVDV-1 and BVDV-2 species and an emerging putative third species (HoBi-like virus), recently detected in southern Italy, signaling the occurrence of natural infection in Europe. Recognizing the need to update the data on BVDV genetic variability in Italy for mounting local and European alerts, a wide collection of 5′ UTR sequences (n = 371) was selected to identify the frequency of genotypes and subtypes at the herd level. BVDV-1 had the highest frequency, followed by sporadic BVDV-2. No novel HoBi-like viruses were identified. Four distribution patterns of BVDV-1 subtypes were observed: highly prevalent subtypes with a wide temporal-spatial distribution (1b and 1e), low prevalent subtypes with a widespread geographic distribution (1a, 1d, 1g, 1h, and 1k) or a restricted geographic distribution (1f), and sporadic subtypes detected only in single herds (1c, 1j, and 1l). BVDV-1c, k, and l are reported for the first time in Italy. A unique genetic variant was detected in the majority of herds, but cocirculation of genetic variants was also observed. Northern Italy ranked first for BVDV introduction, prevalence, and dispersion. Nevertheless, the presence of sporadic variants in other restricted areas suggests the risk of different routes of BVDV introduction.

Complete genome sequence and pathogenesis of bovine viral diarrhea virus JL-1 isolate from cattle in China

Background

Bovine viral diarrhea virus (BVDV) is a pathogen found worldwide in calves. It can cause significant economic losses in agriculture. Many BVDV strains have been isolated in China. However, the pathogenesis and complete gene characteristics of BVDV isolate have yet not been reported in China. Here, a BVDV isolate was isolated and its pathogenesis and complete genome were studied.

Results

A new isolate of bovine viral diarrhea virus, named JL-1, was isolated from the spleen of a sick cow with diarrhea using MDBK cell culture. The complete genome of JL-1 is 12,276 nucleotides and contains a 5′-UTR of 382 nucleotides, a 3′-UTR of 188 nucleotides, and a large ORF encoding a polyprotein consisting of 3,901 amino acids. Genomic comparison and phylogenetic analyses of complete genomic sequence clearly showed that JL-1 fell into the BVDV-1b subtype. The result of pathogenesis of JL-1 strain showed that all infected calves developed clinical signs of elevated rectal temperatures, decreased leucopenia, and viral discharge. Viral antigen was detected in infected animal tissues using immunohistochemistry. Animals in the mock were normal. These results demonstrated that BVDV JL-1 was a virulent strain.

Conclusions

This is the first study to report the pathogenesis and complete gene characterization of the BVDV strain in China. This report may set a good foundation for further study of BVDV in China.

Sheep persistently infected with Border disease readily transmit virus to calves seronegative to BVD virus

Bovine viral diarrhea- and Border disease viruses of sheep belong to the highly diverse genus pestivirus of the Flaviviridae. Ruminant pestiviruses may infect a wide range of domestic and wild cloven-hooved mammals (artiodactyla). Due to its economic importance, programs to eradicate bovine viral diarrhea are a high priority in the cattle industry. By contrast, Border disease is not a target of eradication, although the Border disease virus is known to be capable of also infecting cattle. In this work, we compared single dose experimental inoculation of calves with Border disease virus with co-mingling of calves with sheep persistently infected with this virus. As indicated by seroconversion, infection was achieved only in one out of seven calves with a dose of Border disease virus that was previously shown to be successful in calves inoculated with BVD virus. By contrast, all calves kept together with persistently infected sheep readily became infected with Border disease virus. The ease of viral transmission from sheep to cattle and the antigenic similarity of bovine and ovine pestiviruses may become a problem for demonstrating freedom of BVD by serology in the cattle population.

Pestiviruses

Pestiviruses cause economically important diseases among domestic ruminants and pigs, but they may also infect a wide spectrum of wild species of even-toed ungulates (Artiodactyla). Bovine viral diarrhea virus (BVDV) and Border disease virus of sheep infect their hosts either transiently or persistently. Cellular and humoral immunotolerance to the infecting strain is a unique feature of persistent infection (PI) by ruminant pestiviruses. Persistence, caused by transplacental infection early in fetal development, depends on virally encoded interferon antagonists that inactivate the host's innate immune response to the virus without globally interfering with its function against other viruses. At epidemiological equilibrium, approximately 1-2% of animals are PI. Successful BVDV control programs show that removal of PI animals results in viral extinction in the host population. The nucleotide sequences of ruminant pestiviruses change little during persistent infection. Nevertheless, they display large heterogeneity, pointing to a long history of virus-host coevolution in which avirulent strains are more successful.

Complete genome sequences of both biotypes of a virus pair of bovine viral diarrhea virus subgenotype 1k

We determined the complete genome sequences of both biotypes of a virus pair of bovine viral diarrhea virus (BVDV) subgenotype 1k. The viruses were isolated from a persistently infected calf suffering from mucosal disease. Compared to the noncytopathic biotype, the cytopathic biotype contains an insertion of 84 nucleotides and 22 nucleotide changes.

A review of the infection, genetics, and evolution of Neospora caninum: from the past to the present

This paper is a review of current knowledge on Neospora caninum in the context of other apicomplexan parasites and with an emphasis on: life cycle, disease, epidemiology, immunity, control and treatment, evolution, genomes, and biological databases and web resources. N. caninum is an obligate, intracellular, coccidian, protozoan parasite of the phylum Apicomplexa. Infection can cause the clinical disease neosporosis, which most notably is associated with abortion in cattle. These abortions are a major root cause of economic loss to both the dairy and beef industries worldwide. N. caninum has been detected in every country in which a study has been specifically conducted to detect this parasite in cattle. The major mode of transmission in cattle is transplacental (or vertical) transmission and several elements of the N. caninum life cycle are yet to be studied in detail. The outcome of an infection is inextricably linked to the precise timing of the infection coupled with the status of the immune system of the dam and foetus. There is no community consensus as to whether it is the dam's pro-inflammatory cytotoxic response to tachyzoites that kills the foetus or the tachyzoites themselves. From economic analysis the most cost-effective approach to control neosporosis is a vaccine. The perfect vaccine would protect against both infection and the clinical disease, and this implies a vaccine is needed that can induce a non-foetopathic cell mediated immunity response. Researchers are beginning to capitalise on the vast potential of -omics data (e.g. genomes, transcriptomes, and proteomes) to further our understanding of pathogens but especially to identify vaccine and drug targets. The recent publication of a genome for N. caninum offers vast opportunities in these areas.

Immunology of BVDV vaccines

Providing acquired immune protection against infection with bovine viral diarrhea viruses (BVDV) is challenging due to the heterogeneity that exists among BVDV strains and the ability of the virus to infect the fetus and establish persistent infections. Both modified live and killed vaccines have been shown to be efficacious under controlled conditions. Both humoral and cellular immune responses are protective. Following natural infection or vaccination with a modified live vaccine, the majority of the B cell response (as measured by serum antibodies) is directed against the viral proteins E2 and NS2/3, with minor responses against the Erns and E1 proteins. Vaccination with killed vaccines results in serum antibodies directed mainly at the E2 protein. It appears that the major neutralizing epitopes are conformational and are located within the N-terminal half of the E2 protein. While it is thought that the E2 and NS2/3 proteins induce protective T cell responses, these epitopes have not been mapped. Prevention of fetal infections requires T and B cell response levels that approach sterilizing immunity. The heterogeneity that exists among circulating BVDV strains, works against establishing such immunity. Vaccination, while not 100% effective in every individual animal, is effective at the herd level.

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.

Molecular characteristics of bovine virus diarrhoea virus 1 isolates from Turkey: approaches for an eradication programme

Forty pestivirus isolates sampled from cattle in Turkey between 2002 and 2007 were characterized according to 5' untranslated region (5'UTR) sequences and autoprotease (N(pro) ) gene sequences. The sampling of Bovine virus diarrhoea viruses (BVDVs) from 15 farms in five different regions indicated that BVDV 1-l (18/40, 45%) was the predominant genotype in Turkey; the samples also contained the genotypes 1-f (10/40, 25%), 1-b (7/40, 17.5%), 1-d (3/40, 7.5%), and 1-a (2/40, 5%), respectively.

Genetic and antigenic characterization of bovine viral diarrhoea virus type 2 isolated from cattle in India

Previous studies have shown that bovine viral diarrhoea virus type 1 (BVDV-1) subtype b is predominantly circulating in Indian cattle. During testing for exotic pestiviruses between 2007 and 2010, BVDV-2 was identified by real time RT-PCR in two of 1446 cattle blood samples originating from thirteen states of India. The genetic analysis of the isolated virus in 5' UTR, N(pro), entire structural genes (C, E(rns), E1 and E2), nonstructural genes NS2-3 besides 3' UTR demonstrated that the nucleotide and amino acid sequences showed highest similarity with BVDV-2. The entire 5' and 3' UTR consisted of 387 and 204 nucleotides, respectively, and an eight nucleotide repeat motif was found twice within the variable part of 3' UTR that may be considered as a characteristic of BVDV-2. The phylogenetic analysis revealed that the cattle isolate and earlier reported goat BVDV-2 isolate fall into separate clades within BVDV-2a subtype. Antigenic typing with monoclonal antibodies verified the cattle isolate also as BVDV-2. In addition, cross-neutralization tests using antisera raised against Indian BVDV strains circulating in ruminants (cattle, sheep, goat and yak) displayed significant antigenic differences only between BVDV-1 and BVDV-2 strains. This is the first identification of BVDV-2 in Indian cattle that may have important implications for immunization strategies and molecular epidemiology of BVD.

Cytopathic bovine viral diarrhea viruses (BVDV): emerging pestiviruses doomed to extinction

Bovine viral diarrhea virus (BVDV), a Flaviviridae pestivirus, is arguably one of the most widespread cattle pathogens worldwide. Each of its two genotypes has two biotypes, non-cytopathic (ncp) and cytopathic (cp). Only the ncp biotype of BVDV may establish persistent infection in the fetus when infecting a dam early in gestation, a time point which predates maturity of the adaptive immune system. Such fetuses may develop and be born healthy but remain infected for life. Due to this early initiation of fetal infection and to the expression of interferon antagonistic proteins, persistently infected (PI) animals remain immunotolerant to the infecting viral strain. Although only accounting for some 1% of all animals in regions where BVDV is endemic, PI animals ensure the viral persistence in the host population. These animals may, however, develop the fatal mucosal disease, which is characterized by widespread lesions in the gastrointestinal tract. Cp BVD virus, in addition to the persisting ncp biotype, can be isolated from such animals. The cp viruses are characterized by unrestrained genome replication, and their emergence from the persisting ncp ones is due to mutations that are unique in each virus analyzed. They include recombinations with host cell mRNA, gene translocations and duplications, and point mutations. Cytopathic BVD viruses fail to establish chains of infection and are unable to cause persistent infection. Hence, these viruses illustrate a case of "viral emergence to extinction" - irrelevant for BVDV evolution, but fatal for the PI host.

Bovine viral diarrhea virus: global status

Despite the success of regional bovine viral diarrhea viruses (BVDV) eradication programs, infections remain a source of economic loss for producers. The wide variation among BVDV results in differences in genotype, biotype, virulence, and types of infections. BVDV infect a range of domestic and wild ruminants. Clinical presentation varies depending on strain of virus, species of host, immune status of host, reproductive status of host, age of host, and concurrent infections. Recent advances in BVDV research and diagnostics have led to the development of regional eradication/control programs, the most efficacious of which focus on biosecurity, surveillance, and control.

Prevalence and antigenic differences observed between Bovine viral diarrhea virus subgenotypes isolated from cattle in Australia and feedlots in the southwestern United States

Bovine viral diarrhea virus (BVDV) is divided into 2 different species within the Pestivirus genus, BVDV type 1 (BVDV-1) and BVDV type 2 (BVDV-2). Further phylogenetic analysis has revealed subgenotype groupings within the 2 types. Thus far, 12 BVDV-1 subgenotypes (a-l) and 2 BVDV-2 subgenotypes (a and b) have been identified. The purpose of the current study was to determine the prevalence of BVDV subgenotypes in the United States and Australia and to determine if there are detectable antigenic differences between the prevalent subgenotypes. To determine prevalence, phylogenetic analysis was performed on 2 blinded panels of isolates consisting of 351 viral isolates provided by the Elizabeth Macarthur Laboratory, New South Wales, and 514 viral isolates provided by Oklahoma State University. Differences were observed in the prevalence of BVDV subgenotypes between the United States (BVDV-1b most prevalent subgenotype) and Australia (BVDV-1c most prevalent subgenotype). To examine antigenic differences between the subgenotypes identified in samples from the United States and Australia, polyclonal antisera was produced in goats by exposing them at 3-week intervals to 2 noncytopathic and 1 cytopathic strain of either BVDV-1a, BVDV-1b, BVDV-1c, BVDV-2a, or Border disease virus (BDV). Virus neutralization (VN) assays were then performed against 3 viruses from each of the 5 subgenotypes. Comparison of VN results suggests that there are antigenic differences between BVDV strains belonging to different subgenotypes. The present study establishes a foundation for further studies examining whether vaccine protection can be improved by basing vaccines on the BVDV subgenotypes prevalent in the region in which the vaccine is to be used.

Genotyping of bovine viral diarrhea viruses from cattle in China between 2005 and 2008

Eighteen bovine viral diarrhea viruses (BVDV) from cattle in China between 2005 and 2008 were genetically typed by sequencing of the 5'-untranslated region (5'-UTR) of the viral genome and for selected isolates the N(pro) region. Phylogenetic reconstructions indicated that all of the 18 BVDV positive samples examined in this work clustered within the BVDV type 1 genotype. Of the 15 previously described subgenotypes of BVDV1 (1a-1o), 12 of the samples examined in this work clustered with the Chinese BVDV ZM-95 strain of pig origin, which was the prototype of BVDV1m, while 2 samples clustered with the BVDV1b. But 4 samples formed a separate group appearing to be a potentially new subgenotype, which was tentatively typed as "BVDV1p". Based on these results there appears to be highly genetic variation within the Chinese BVDV field isolates. As well, the phylogenetic reconstructions indicate that the clustering of the Chinese BVDV1m subgenotype in the phylogenetic tree is a result of geographic isolation. The information obtained from this work will be useful when carrying out epidemiological surveys of BVDV detected in China, especially for the BVDV1m detection in Chinese cattle.

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.