BVD-2 outbreak leads to high losses in cattle farms in Western Germany

"Fading out" - genomic epidemiology of the last persistently infected BVDV cattle in Germany

Bovine viral diarrhea virus (BVDV) is one of the most important cattle pathogens worldwide, causing major economic losses and animal welfare issues. Disease eradication programs have been implemented in several countries, including Germany where an obligatory nationwide control program is in force since 2011. As molecular epidemiology has become an essential tool to understand the transmission dynamics and evolution of BVDV, 5' untranslated region (UTR) sequences are generated from viruses present in persistently infected animals since the beginning of the BVDV control program. Here, we report the results of the sequence-based subtyping of BVDV strains found from 2018 through 2022 in calves born in Germany. In 2018, 2019 and 2020, BVDV-1d and-1b were the dominant subtypes and cases were spread throughout the area that was not yet officially declared BVDV-free at that time. In addition, BVDV-1a, -1e, -1f and -1h could rarely be detected. From 2021 onwards, subtype 1d clearly took over the dominance, while the other subtypes could be gradually nearly eliminated from the cattle population. The eradication success not only results in a drastic reduction of cases, but also in a marked reduction of strain diversity. Interestingly, before vaccination has been banned in regions and farms with a disease-free status, two live-vaccine virus strains were repeatedly detected in ear tissue samples of newborn calves (n = 14) whose mothers were immunized during gestation. The field-virus sequences are an important basis for molecular tracing and identification of potential relationships between the last outbreaks in the final phase of the German BVDV eradication program, thereby supporting classic epidemiological investigations. Furthermore, the monitoring of the composition of virus subtypes in the cattle population helps to maintain effective diagnostic methods and control measures and is an early warning system for the introduction of new pestiviruses in the naïve cattle population.

Identification of Genomic Instability in Cows Infected with BVD Virus

An important factor for dairy cattle farmers is the profitability of cattle rearing, which is influenced by the animals' health and reproductive parameters, as well as their genomic stability and integrity. Bovine viral diarrhea (BVD) negatively affects the health of dairy cattle and causes reproductive problems. The aim of the study was to identify genomic instability in cows with reproductive disorders following infection with the BVD virus. The material for analysis was peripheral blood from Holstein-Friesian cows with reproductive problems, which had tested positive for BVD, and from healthy cows with no reproductive problems, which had tested negative for BVD. Three cytogenetic tests were used: the sister chromatid exchange assay, fragile sites assay, and comet assay. Statistically significant differences were noted between the groups and between the individual cows in the average frequency of damage. The assays were good biomarkers of genomic stability and enabled the identification of individuals with an increased frequency of damage to genetic material that posed a negative impact on their health. The assays can be used to prevent disease during its course and evaluate the genetic resistance of animals. This is especially important for the breeder, both for economic and breeding reasons. Of the three assays, the comet assay proved to be the most sensitive for identifying DNA damage in the animals.

[Genetic diversity and distribution of bovine pestiviruses (Flaviviridae: Pestivirus) in the world and in the Russian Federation]

The genus Pestivirus of the family Flaviviridae includes 11 species. Bovine pestiviruses are the causative agents of viral diarrhea/mucosal disease and include three genetically distinct species: pestivirus A (BVDV-1), B (BVDV-2), and H (BVDV-3). The number of BVDV-1 subtypes is 21, BVDV-2 - 4, and BVDV-3 - 4, which complicates the diagnosis of associated diseases, reduces the effectiveness of vaccination and control programs.We performed the search in the PubMed, Web of Science, Scopus, eLIBRARY.RU databases for articles published in 2000-2021.Pestivirus A is distributed everywhere, although the largest number of subtypes was found in cattle in Italy and China. The virus is widespread in the Central region of the Russia (subtypes 1a and 1m). In Siberia, eleven subtypes circulate among native and imported animals: 1a (5%), 1b (35%), 1c (5%), 1d (10%), 1f (20%), 1g, 1i (both 2.5%), 1j, 1k, 1p, and 1r (all for 5%). Pestivirus B subtype is more virulent, found less frequently and mainly in the North and South America, in some European countries, and in Asia. Three subtypes have been identified in Siberia: 2a (25%), 2b (10%), and 2c (5%). Pestivirus H circulates in Europe, Asia and South America. The main route of entry is contaminated biological products. In Russia, BVDV-3 of the Italian-Brazilian group (3a) was detected in 7 lots of fetal bovine serum.The role of the virus in the occurrence of respiratory diseases in calves, abortion, systemic infection and enteritis in calves and adult animals has been established. The source of the virus in such cases was a contaminated modified live vaccine.

The contribution of bovines to human health against viral infections

In the last 40 years, novel viruses have evolved at a much faster pace than other pathogens. Viral diseases pose a significant threat to public health around the world. Bovines have a longstanding history of significant contributions to human nutrition, agricultural, industrial purposes, medical research, drug and vaccine development, and livelihood. The life cycle, genomic structures, viral proteins, and pathophysiology of bovine viruses studied in vitro paved the way for understanding the human counterparts. Calf model has been used for testing vaccines against RSV, papillomavirus vaccines and anti-HCV agents were principally developed after using the BPV and BVDV model, respectively. Some bovine viruses-based vaccines (BPIV-3 and bovine rotaviruses) were successfully developed, clinically tried, and commercially produced. Cows, immunized with HIV envelope glycoprotein, produced effective broadly neutralizing antibodies in their serum and colostrum against HIV. Here, we have summarized a few examples of human viral infections for which the use of bovines has contributed to the acquisition of new knowledge to improve human health against viral infections covering the convergence between some human and bovine viruses and using bovines as disease models. Additionally, the production of vaccines and drugs, bovine-based products were covered, and the precautions in dealing with bovines and bovine-based materials.

A Herd Investigation Tool in Support of the Irish Bovine Viral Diarrhoea Eradication Programme

Bovine viral diarrhoea (BVD) is an important endemic disease of cattle. In Ireland, an industry-led compulsory eradication programme began in January 2013. The main elements of this programme are the identification and elimination of persistently infected (PI) calves by testing all new-borns, the implementation of biosecurity to prevent re-introduction of disease and continuous surveillance. In 2016, a standardised framework was developed to investigate herds with positive results. This is delivered by trained private veterinary practitioners (PVP). The investigation's aims are 3-fold: firstly, to identify plausible sources of infection; secondly, to ensure that no virus-positive animals remain on farm by resolving the BVD status of all animals in the herd; and thirdly, agreeing up to three biosecurity measures with the herd owner to prevent the re-introduction of the virus. Each investigation follows a common approach comprising four steps based on information from the programme database and collected on-farm: firstly, identifying the time period when each virus-positive calf was exposed in utero (window of susceptibility, taken as 30-120 days of gestation); secondly, determining the location of the dam of each positive calf during this period; thirdly, to investigate potential sources of exposure, either within the herd or external to it; and finally, based on the findings, the PVP and herdowner agree to implement up to three biosecurity measures to minimise the risk of reintroduction. Between 2016 and 2020, 4,105 investigations were completed. The biosecurity recommendations issued more frequently related to the risks of introduction of virus associated with contact with neighbouring cattle at pasture, personnel (including the farmer), the purchase of cattle and vaccination. Although each investigation generates farm-specific outcomes and advice, the aggregated results also provide an insight into the most commonly identified transmission pathways for these herds which inform overall programme communications on biosecurity. The most widely identified plausible sources of infection over these years included retained BVD-positive animals, Trojan births, contact at boundaries and indirect contact through herd owner and other personnel in the absence of appropriate hygiene measures. While generated in the context of BVD herd investigations, the findings also provide an insight into biosecurity practises more generally on Irish farms.

Epidemiology of Pestivirus H in Brazil and Its Control Implications

Along with viruses in the Pestivirus A (Bovine Viral Diarrhea Virus 1, BVDV1) and B species (Bovine Viral Diarrhea Virus 2, BVDV2), members of the Pestivirus H are mainly cattle pathogens. Viruses belonging to the Pestivirus H group are known as HoBi-like pestiviruses (HoBiPev). Genetic and antigenic characterization suggest that HoBiPev are the most divergent pestiviruses identified in cattle to date. The phylogenetic analysis of HoBiPev results in at least five subgroups (a–e). Under natural or experimental conditions, calves infected with HoBiPev strains typically display mild upper respiratory signs, including nasal discharge and cough. Although BVDV1 and BVDV2 are widely distributed and reported in many South American countries, reports of HoBiPev in South America are mostly restricted to Brazil. Despite the endemicity and high prevalence of HoBiPev in Brazil, only HoBiPev-a was identified to date in Brazil. Unquestionably, HoBiPev strains in BVDV vaccine formulations are required to help curb HoBiPev spread in endemic regions. The current situation in Brazil, where at this point only HoBiPev-a seems present, provides a more significant opportunity to control these viruses with the use of a vaccine with a single HoBiPev subtype. Despite the lack of differentiation among bovine pestiviruses by current BVDV tests, the reduced genetic variability of HoBiPev in Brazil may allow reliable identification of cases within the region. On the other hand, introducing foreign ruminants, biologicals, and genetic material to South America, especially if it originated from other HoBiPev-endemic countries, should consider the risk of introducing divergent HoBiPev subtypes.

Individual-based model for the control of Bovine Viral Diarrhea spread in livestock trade networks

Bovine Viral Diarrhea (BVD) is a cattle disease that causes substantial financial losses, in particular to the dairy industry. Hence, several countries including Germany introduced compulsory disease control programs. For the case of Germany in particular, all animals had to be tested and persistently infected animals (PI animals) were removed from the population. The program was successful in reducing the number of PI animals, but was overtly expensive. Alternative approaches were therefore discussed to eliminate the remaining PI animals and alter the testing system in order to reduce costs. Contributing to these efforts, we developed an agent-based model that aimed to cover all relevant aspects of the disease biology and would allow to evaluate different control strategies. For the biological part of the infection spread, the model includes horizontal and vertical transmission, transient and persistent infections. Moreover, several control strategies including import of animals, trade restrictions, vaccination, as well as various testing schemes were included. The model was furthermore defined to be stochastic, event-driven and hierarchical, with cattle movements as the main route of spreading between farms. For the spread within farms, we included susceptible-infected-recovered (SIR) dynamics with an additional permanently infectious class. The interaction between the farms was described by a supply and demand farm manager mechanism governing the network structure and dynamics. Additionally, we carried out a sensitivity analysis of the input parameters to study the impact of extreme values on the model. Since the population size in the model is limited, we tested the influence of the initial population size on the model results. Our results showed that the model could accurately describe the dynamics of the disease in the presence and absence of disease control. Although we developed the model for the spread of BVD, it may be adapted to similar diseases of cattle and swine.

Epidemiology of Bovine Pestiviruses Circulating in Italy

Pestiviruses are widespread and economically important pathogens of cattle and other animals. Pestivirus A (formerly known as Bovine viral diarrhea virus 1, BVDV-1), Pestivirus B (Bovine viral diarrhea virus 2, BVDV-2), and Pestivirus H (HoBi-like pestivirus, HoBiPeV) species are infecting primarily cattle. Like other RNA viruses, pestiviruses are characterized by a high degree of genetic variability. This high rate of variability is revealed by the existence of a number of viral subgenotypes within each species. In cattle, the highest number of pestivirus subgenotypes has been documented in European countries, particularly in Italy. The aim of this review is to report an up-to-date overview about the genetic diversity of pestiviruses in Italian cattle herds. All three bovine pestiviruses species have been identified in cattle population with variable frequency and geographical distribution. The genetic diversity of Italian pestiviral strains may have diagnostic and immunological implications, affecting the performance of diagnostic tools and the full cross-protection elicited by commercially available vaccines. Implementation and strengthening of coordinated approaches for bovine pestivirus control in Italy are recommended. Therefore, it would be extremely important to increase control and restriction measures to the trade of cattle and biological products of bovine origin, including those containing fetal bovine serum.

Non-discriminatory Exclusion Testing as a Tool for the Early Detection of Foot-and-Mouth Disease Incursions

Endemic circulation of foot-and-mouth disease (FMD) in Africa and Asia poses a continuous risk to countries in Europe, North America, and Oceania which are free from the disease. Introductions of the disease into a free region have dramatic economic impacts, especially if they are not detected at an early stage and controlled rapidly. However, farmers and veterinarians have an obvious disincentive to report clinical signs that are consistent with FMD, due to the severe consequences of raising an official suspicion, such as farm-level quarantine. One way that the risk of late detection can be mitigated is offering non-discriminatory exclusion testing schemes for differential diagnostics, wherein veterinarians can submit samples without the involvement of the competent authority and without sanctions or costs for the farmer. This review considers the benefits and limitations of this approach to improve the early detection of FMD in free countries and gives an overview of the FMD testing schemes currently in use in selected countries in Europe and the Americas as well as in Australia.

A Synthetic Modified Live Chimeric Marker Vaccine against BVDV-1 and BVDV-2

Bovine viral diarrhea virus (BVDV), a pestivirus which exists in the two distinct species BVDV-1 (syn. Pestivirus A) and BVDV-2 (syn. Pestivirus B), is the causative agent of one of the most widespread and economically important virus infections in cattle. For economic as well as for animal health reasons, an increasing number of national BVDV control programs were recently implemented. The main focus lies on the detection and removal of persistently infected cattle. The application of efficient marker or DIVA (differentiation of infected from vaccinated animals) vaccines would be beneficial for the eradication success in regions with a high BVDV prevalence to prevent fetal infection and it would allow serological monitoring of the BVDV status also in vaccinated farms. Therefore, a marker vaccine based on the cytopathic (cp) BVDV-1b strain CP7 was constructed as a synthetic backbone (BVDV-1b_synCP7). For serological discrimination of vaccinated from infected animals, the viral protein E^rns was substituted by the heterologous E^rns of Bungowannah virus (BuPV, species Pestivirus F). In addition, the vaccines were attenuated by a deletion within the type I interferon inhibitor N^pro protein encoding sequence. The BVDV-2 vaccine candidate is based on the genetic sequence of the glycoproteins E1 and E2 of BVDV-2 strain CS8644 (CS), which were introduced into the backbone of BVDV-1b_synCP7_ΔN^pro_E^rns Bungo in substitution of the homologous glycoproteins. Vaccine virus recovery resulted in infectious cytopathic virus chimera that grew to titers of up to 10⁶ TCID₅₀/mL. Both synthetic chimera BVDV-1b_synCP7_ΔN^pro_E^rns Bungo and BVDV-1b_synCP7_ΔN^pro_E^rns Bungo_E1E2 BVDV-2 CS were avirulent in cattle, provided a high level of protection in immunization and challenge experiments against both BVDV species and allowed differentiation of infected from vaccinated cattle. Our study presents the first report on an efficient BVDV-1 and -2 modified live marker vaccine candidate and the accompanying commercially available serological marker ELISA system.

Hierarchical Structures in Livestock Trade Networks-A Stochastic Block Model of the German Cattle Trade Network

Trade of cattle between farms forms a complex trade network. We investigate partitions of this network for cattle trade in Germany. These partitions are groups of farms with similar properties and they are inferred directly from the trade pattern between farms. We make use of a rather new method known as stochastic block modeling (SBM) in order to divide the network into smaller units. SBM turns out to outperform the more established community detection method in the context of disease control in terms of trade restriction. Moreover, SBM is also superior to geographical based trade restrictions and could be a promising approach for disease control.

Risk factors associated with the within-farm transmission of bovine viral diarrhea virus and the incidence of persistently infected cattle on dairy farms from Ibaraki prefecture of Japan

For understanding the factors affecting bovine viral diarrhea virus (BVDV) transmission, this study investigated the distribution of BVDV and the epidemiological features of persistently infected (PI) cattle in Ibaraki Prefecture of Japan, and identified farm-level risk factors associated with BVDV infection, with a focus on within-farm transmission and PI animal detection. Among all 377 dairy farms, forty-four PI cattle were identified on 22 farms. Thirty-eight and six PI cattle were born on their current farms or purchased, respectively. Twenty-six PI cattle were born from pregnancies on their current farms, seven from pregnancies in summer pastures, and eight from pregnancies on other farms. The within-farm seroprevalence on farms with PI animals was significantly higher than that on farms without PI cattle. Of 333 farms holding homebred cattle without movement records, antibody-positivity in homebred cattle was observed on 194 farms; these cattle were likely infected by within-farm transmission. Herd size, summer pasturing, and BVDV infection status of the nearest dairy farm were risk factors associated with within-farm transmission. Likewise, herd size, summer pasturing, and the proportion of purchased cattle were related to PI animal occurrence. This study shows the risk of within-farm transmission and occurrence of PI animals after the introduction of BVDV via purchasing and summer pasturing, and illustrates the significant role of PI cattle in circulating BVDV. More effective measures for screening BVDV infection and PI animals, including intensive tests targeting moved cattle and newborn calves, and bulk milk surveillance, are required to control the spread of BVDV in Japan.

Prevalence and genetic diversity of bovine viral diarrhea virus in dairy herds of China

To determine the nationwide prevalence and genetic diversity of bovine viral diarrhea virus (BVDV) in China, 92 dairy farms with more than 500 animals in 19 provinces of China were surveyed in 2017. At each farm, ear notch samples from calves less than six months old and bulk tank milk (BTM) samples were collected. A total of 901 ear notch samples and 329 BTM samples from 183 tanks were sampled. A total of 20 (20/901, 2.22 %) ear notch samples from 10 (10/92, 10.86 %) farms tested positive for BVDV by IDEXX Antigen Point-of-Care (POC) Test kit and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). In addition, 80 of 183 (80/183, 43.7 %) BTM samples from 43 (43/92, 46.7 %) farms were identified as positive by qRT-PCR. The RNA of positive and suspect samples identified by qRT-PCR was subjected to 5'- untranslated region (UTR) amplification by nested RT-PCR and then sequenced. A total of 119 sequences were obtained and phylogenetic analysis of these 5'-UTR sequences revealed the presence of eight different subgenotypes of BVDV-1 including 1a (n = 37, 31.09 %), 1b (n = 5, 4.20 %), 1c (n = 34, 28.57 %), 1d (n = 2, 1.68 %), 1m (n = 25, 21.01 %), 1q (n = 6, 5.04 %), and two unknown subgenotypes which were tentatively typed as "BVDV-1v" (n = 8, 6.72 %) and "BVDV-1w" (n = 2, 1.68 %), respectively. BVDV-1a, 1c, and 1m were the dominant strains, collectively accounting for 80.67 % (96/119) of all sequences. Phylogenetic analysis based on selected N-terminal autoprotease (N^pro) sequences confirmed the classification of the 5'-UTR sequences. In conclusion, the prevalence of BVDV persistent infection in dairy cattle was high and genetic diversity was high and increasing, revealing a serious threat to the health of cattle in China and highlighting the need for BVDV control.

An Epidemiological and Economic Simulation Model to Evaluate Strategies for the Control of Bovine Virus Diarrhea in Germany

Models can be used to plan, evaluate, and improve programs for animal disease control. In Germany, a nationwide compulsory program to eradicate Bovine viral diarrhea (BVD) is in force since January 2011. As it is associated with substantial expenditures, the program is currently under revision. To provide the basis for a science-based decision on the future course of BVD control in Germany, we evaluated 13 scenarios (sc1-13) with respect to the chance of reaching freedom from disease and their economic implications for a period of 20 years (2011–2030). To simulate the impact of different control strategies on disease dynamics, a disease spread model was developed. To estimate the effects of a transient infection (TI) on animal level, a gross margin analysis was performed. To assess the value of cattle that died prematurely, a valuation model was used. Finally, an economic model was developed to perform a cost-benefit analysis and to compare each control scenario with a baseline setting with no BVD control. Costs comprised the expenditures for diagnostics, vaccination, preventive culling, and trade restrictions. Benefits were animal and production losses avoided by having control measures in place. The results show that reducing the PI prevalence on animal level to 0% is only feasible in scenarios that combine antigen or antibody testing with compulsory vaccination. All other scenarios, i.e., those based exclusively on a “test and cull” approach, including the current control program, will, according to the model, not achieve freedom of BVD by 2030. On the other hand, none of the scenarios that may lead to complete BVD eradication is economically attractive [benefit-cost ratio (BCR) between 0.64 and 0.94]. The average direct costs of BVD in Germany are estimated at 113 million Euros per year (34–402 million Euros), corresponding to 28.3 million Euros per million animals. Only the concepts of the former and the current national BVD control program (“ear tag testing and culling”) may reduce the BVD prevalence to 0.01% with an acceptable BCR (net present value of 222 and 238 million Euros, respectively, with a BCR of 1.22 and 1.24).

Removal of bovine viral diarrhea virus (BVDV) from lumpy skin disease virus (LSDV) vaccine stocks by passage on chorioallantoic membranes of fertilized hens' eggs

Bovine viral diarrhea virus (BVDV) is a common contaminant of Madin-Darby bovine kidney (MDBK) cells as well as fetal calf serum (FCS). It is pathogenic to cattle and regulatory authorities require that veterinary vaccine stocks are free from BVDV. MDBK cells are used in the generation of recombinant lumpy skin disease virus (LSDV) and have been used for the growth of LSDV vaccines. This paper describes how vaccine stocks can be cleared of BVDV by passage through an avian host, nonpermissive to BVDV, but permissive to LSDV. LSDV vaccine stocks were shown to be cleared of BVDV after passage on the chorioallantoic membranes (CAMs) of fertilized 7-day old hens' eggs. Vaccines were passaged a second time on CAMs before being grown in primary lamb testes (LT) cells. Vaccines retained BVDV-negative status after passage on LT cells.

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.

Viral metagenomics reveals significant viruses in the genital tract of apparently healthy dairy cows

The virome in genital tract secretion samples collected from 80 dairy cattle in Shanghai, China, was characterized. Viruses detected included members of the families Papillomaviridae, Polyomaviridae, Hepeviridae, Parvoviridae, Astroviridae, Picornaviridae, and Picobirnaviridae. A member of a new species within the genus Dyoxipapillomavirus and six circular Rep-encoding single-stranded DNA (ssDNA) (CRESS-DNA) viral genomes were fully sequenced and phylogenetically analyzed. The prevalence of bovine polyomaviruses 1 and 2 was measured by PCR to be 10% (8/80) and 6.25% (5/80), respectively. PCR screening also indicated that the novel papillomavirus ujs-21015 and bovine herpesvirus 6 were present in three and two out of the 80 samples, respectively.

Global knowledge gaps in the prevention and control of bovine viral diarrhoea (BVD) virus

The significant economic impacts of bovine viral diarrhoea (BVD) virus have prompted many countries worldwide to embark on regional or national BVD eradication programmes. Unlike other infectious diseases, BVD control is highly feasible in cattle production systems because the pathogenesis is well understood and there are effective tools to break the disease transmission cycle at the farm and industry levels. Coordinated control approaches typically involve directly testing populations for virus or serological screening of cattle herds to identify those with recent exposure to BVD, testing individual animals within affected herds to identify and eliminate persistently infected (PI) cattle, and implementing biosecurity measures such as double-fencing shared farm boundaries, vaccinating susceptible breeding cattle, improving visitor and equipment hygiene practices, and maintaining closed herds to prevent further disease transmission. As highlighted by the recent DISCONTOOLS review conducted by a panel of internationally recognized experts, knowledge gaps in the control measures are primarily centred around the practical application of existing tools rather than the need for creation of new tools. Further research is required to: (a) determine the most cost effective and socially acceptable means of applying BVD control measures in different cattle production systems; (b) identify the most effective ways to build widespread support for implementing BVD control measures from the bottom-up through farmer engagement and from the top-down through national policy; and (c) to develop strategies to prevent the reintroduction of BVD into disease-free regions by managing the risks associated with the movements of animals, personnel and equipment. Stronger collaboration between epidemiologists, economists and social scientists will be essential for progressing efforts to eradicate BVD from more countries worldwide.

Identification of a new bovine viral diarrhea virus subtype in the Republic of Korea

Background

Bovine viral diarrhea virus (BVDV) is prevalent in Korean indigenous cattle, leading to substantial economic losses. This study was conducted to investigate the occurrence of BVDV. In 2016, a total of 143 blood samples were collected from asymptomatic Korean indigenous calves younger than 3-months of age from six different farms in the Republic of Korea (ROK).

Results

Eighty-seven calves (60.8%, 87/143) were tested positive for BVDV as evaluated by RT-PCR analysis. Phylogenetic analysis based on the 5′-untranslated region was used to classify these cases into three subtypes: BVDV-1b, BVDV-1o, and BVDV-2a. These results showed that BVDV-1b was the predominant subtype, while 2 samples clustered with BVDV-2a. Interestingly, one sample formed a separate group as a potentially new subtype, BVDV-1o. To our knowledge, this is the first report of BVDV-1o infection in Korean native calves. The BVDV-1o subtype identified in this study was closely related to cattle isolates obtained from Japan, indicating that this subtype is a new introduction to the ROK.

Conclusions

This study provides useful information for carrying out epidemiological surveys of BVDV in the ROK and developing a vaccine for future use in the ROK, particularly for the first detection of BVDV-1o in Korean indigenous calves. Further studies are required to investigate the prevalence and pathogenicity of this BVDV-1o subtype.

Establishment of a Bovine Viral Diarrhea Virus Type 2 Intranasal Challenge Model for Assessing Vaccine Efficacy

The objective of this study was to develop a bovine viral diarrhea virus type 2 (BVDV-2) challenge model suitable for evaluation of efficacy of BVDV vaccines; a model that mimics natural infection and induces clear leukopenia and viremia. Clinical, hematological and virological parameters were evaluated after infection of two age groups of calves (3 and 9 months) with two BVDV-2 strains (1362727 and 502643). Calves became pyrexic between 8 and 9 days post inoculation and exhibited symptoms, such as nasal discharge, mild depression, cough, and inappetence. Leukopenia with associated lymphopenia and neutropenia was evident in all groups with lowest leukocyte and lymphocyte counts reached 8 dpi and granulocyte counts between 11 and 16 dpi, dependent on the strain and age of the calves. A more severe thrombocytopenia was seen in those animals inoculated with strain 1362727. Leukocyte and nasal swab samples were positive by virus isolation, as early as 3 dpi and 2 dpi respectively, independent of the inocula used. All calves seroconverted with high levels of BVDV-2 neutralizing antibodies. BVDV RNA was evident as late as 90 dpi and provides the first evidence of the presence of replicating virus long after recovery from BVDV-2 experimental infection. In summary, moderate disease can be induced after experimental infection of calves with a low titer of virulent BVDV-2, with leukopenia, thrombocytopenia, viremia, and virus shedding. These strains represent an attractive model to assess the protective efficacy of existing and new vaccines against BVDV-2.

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.

Six Years (2011-2016) of Mandatory Nationwide Bovine Viral Diarrhea Control in Germany-A Success Story

Bovine viral diarrhea (BVD) is one of the most important infectious diseases in cattle, causing major economic losses worldwide. Therefore, control programs have been implemented in several countries. In Germany, an obligatory nationwide eradication program has been in force since 2011. Its centerpiece is the detection of animals persistently infected (PI) with BVD virus, primarily based on the testing of ear tissue samples of all newborn calves for viral genome or antigen, and their removal from the cattle population. More than 48,000 PI animals have so far been detected and removed. Between the onset of the program and the end of 2016, the prevalence of these animals among all newborn calves decreased considerably, from 0.5% to less than 0.03%. The number of cattle holdings with PI animals likewise decreased from 3.44% in 2011 to only 0.16% in 2016. Since a large number of naïve, fully susceptible animals are now confronted with BVD virus, which is still present in the German cattle population, the challenge of the coming years will be the identification of remaining PI animals as quickly and efficiently as possible, and the efficient protection of BVD-free farms from reinfection.

Engaging veterinarians and farmers in eradicating bovine viral diarrhoea: a systematic review of economic impact

Bovine viral diarrhoea (BVD) is a significant drain on efficient and successful cattle production in both dairy and beef systems around the world. Several countries have achieved eradication of this disease, but always through the motivation of stakeholders who accept the benefits of eradication. These include increased cattle welfare and fitness of cattle to withstand other diseases, and decreased costs of production, the latter resulting from both decreased costs spent on managing the disease and decreased losses. This paper provides a systematic review of 31 papers, published between 1991 and 2015, that address the economic impact of BVD. Each paper takes a different approach, in either beef or dairy production or both. However with the breadth of work collated, a stakeholder engaged in BVD eradication should find an economic figure of most relevance to them. The reported economic impact ranges from £0 to £552 per cow per year (£2370 including outliers). This range represents endemic or subclinical disease situations seen in herds with stable BVD virus infection, and epidemic or severe acute situations, most often seen in naïve herds. The outcome of infection is therefore dependent on the immune status of the animal and severity of the strain. The variations in figures for the economic impact of BVD relate to these immune and pathogenicity factors, along with the variety of impacts monitored.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine viral diarrhoea (BVD)

Bovine viral diarrhoea (BVD) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of BVD to be listed, Article 9 for the categorisation of BVD according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to BVD. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, BVD can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The assessment here performed on compliance with the criteria as in Section 3 of Annex IV referred to in point (c) of Article 9(1) is inconclusive. The animal species to be listed for BVD according to Article 8(3) criteria are mainly species of the families Bovidae, Cervidae and Camelidae as susceptible species and several mammalian species as reservoirs.

Eradication of bovine viral diarrhea virus in Germany-Diversity of subtypes and detection of live-vaccine viruses

Bovine viral diarrhea (BVD) causes high economic losses in the cattle population worldwide. In Germany, an obligatory control program with detection and removal of persistently infected animals is in force since 2011. For molecular tracing of virus transmission, a comprehensive sequence data base of the currently circulating BVD viruses was established. Partial sequences of 1007 samples collected between 2008 and 2016 were generated. As dominant viruses, subtypes 1b (47.0%) and 1d (26.5%) could be identified with no marked geographic or sampling year effect, a much higher amount of BVDV-2c was detected in 2013 compared to other years, predominantly in Western Germany. In addition, subtypes 1a, 1e, 1f, 1h, 1g, 1k, and 2a were found. Interestingly, besides field-viruses, two different live-vaccine viruses were detected in tissue samples of newborn calves (n=37) whose mothers were immunized during pregnancy.

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.

Analysis of bovine viral diarrhoea virus: Biobank and sequence database to support eradication in Scotland

Samples from bovine viral diarrhoea virus (BVDV)-positive cattle were gathered by Scottish diagnostic laboratories and used to produce a Biobank of samples with associated location and identification data in support of the Scottish BVDV eradication scheme. The samples were subject to direct amplification and sequencing of the 5'-untranslated region (5'-UTR) to define the viral types and subtypes present. From 2693 samples collected prior to 2016, approximately 2300 sequences were obtained, representing 8 BVDV type 1 subtypes. No BVDV type 2 samples were detected. The samples came from all regions of the UK but 66 per cent were from Scotland. Analysis of the sequences showed great diversity in the 5'-UTR, with 1206 different sequences. Many samples carried virus with identical 5'-UTR sequences; often from single locations, but there were also examples of the same sequence being obtained from samples at several different locations. This work provides a resource that can be used to analyse the movement of BVDV strains both within Scotland and between Scotland and other nations, particularly in the latter stages of the Scottish eradication programme, and so inform the advice available to both livestock keepers and policymakers.

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.

Genetic diversity of bovine viral diarrhea viruses from the Galicia region of Spain

This study examined the frequency and diversity of bovine viral diarrhoea viruses (BVDVs) infecting cattle in Galicia (northwestern Spain). A total of 86 BVDV strains were typed in samples of serum from 79 persistently infected animals and 3 viraemic animals and of abomasal fluid from 4 fetuses. Samples came from 73 farms participating in a voluntary BVDV control programme. Typing was based on a 288-bp sequence from the 5′ untranslated region amplified using primers 324 and 326. Of the 86 strains, 85 (98.8 per cent) belonged to species BVDV-1 and 1 (1.2 per cent) belonged to BVDV-2; 73 strains (84.9 per cent) were typed as BVDV-1b, 2 as BVDV-1e and 6 as BVDV-1d. One strain each was typed as belonging to 1a, 1h, 1k and 1l. The sole BVDV-2 strain was classified as 2a. These results identify BVDV-1b as the predominant species, and they indicate the presence of viral types not previously described anywhere in Spain. This is also the first report of BVDV-2 in Galicia and only the second report of BVDV-2 in Spain.