BVDV Type Research Articles

Effects of respiratory virus vaccination and bovine respiratory disease on the respiratory microbiome of feedlot cattle.

The objectives of this study were to evaluate the impacts of two modified-live virus (MLV) vaccination protocols and respiratory disease (BRD) occurrence on the microbial community composition of the nasopharynx in feedlot cattle. The treatment groups included in this randomized controlled trial included: 1) no viral respiratory vaccination (CON), 2) intranasal, trivalent, MLV respiratory vaccine in addition to a parenteral BVDV type I and II vaccine (INT), and 3) parenteral, pentavalent, MLV respiratory vaccination against the same agents (INJ). Calves (n = 525) arrived in 5 truckload blocks and were stratified by body weight, sex, and presence of a pre-existing identification ear-tag. A total of 600 nasal swab samples were selected for DNA extraction and subsequent 16S rRNA gene sequencing to characterize the microbiome of the upper respiratory tract. Nasal swabs collected on d 28 from healthy cattle were used to evaluate the impact of vaccination on upper respiratory tract (URT) microbial communities. Firmicutes were less abundant in INT calves (n = 114; P < 0.05) and this difference was attributed to decreased relative abundance (RA) of Mycoplasma spp. (P = 0.04). Mannheimia and Pasteurella had lower RA in INT (P < 0.05). The microbiome in healthy animals on d 28 had increased Proteobacteria (largely Moraxella spp.) and decreased Firmicutes (comprised almost exclusively of Mycoplasma spp.) compared to animals that were treated for or died from BRD (P < 0.05). Cattle that died had a greater RA of Mycoplasma spp. in their respiratory microbiome on d 0 (P < 0.02). Richness was similar on d 0 and 28, but diversity increased for all animals on d 28 (P>0.05).

398 Young Scholar Award Talk: Influence of a Lifetime Regimen of a Modified-Live Viral or Killed Viral Vaccination Against Bovine Viral Diarrhea Virus on Beef Cattle Performance

Abstract Bovine viral diarrhea virus (BVDV) is a major viral pathogen affecting the cattle industry. Control of BVDV occurs through preventative vaccination or elimination of persistently infected animals. However, evaluation of the longevity of cows vaccinated during pregnancy has not been conducted. In experiment 1, heifers born in 2014 (n = 32) were randomly assigned to receive a modified-live viral vaccination (MLV; Bovishield Gold 5 FP) at 3 months of age, and subsequently receive a MLV or killed viral vaccination (KV; Cattlemaster Gold 5 FP) against BVDV beginning at weaning for the duration of their lifespan in the herd. Heifers born in 2015 (n = 29) were randomly assigned to receive a MLV or KV beginning at 3 months of age for the duration of their lifespan in the herd. Heifers were bled for analysis of antibody titers throughout their first year of life, and twice-yearly beginning at 2 years of age. Titers for infectious bovine rhinotracheitis (IBR) and BVDV, herd longevity, and reproductive performance were collected. Vaccination type did not influence IBR titer (P ≥ 0.18), herd longevity (P ≥ 0.86), or reproductive development (P ≥ 0.19). Cows born in 2015 and their calves were used in experiment 2 (n = 24) to evaluate responses in the preweaning period. Cow and calf samples of blood and ruminal contents, and colostrum and milk were collected at d 1, 7, 35, 63, and 205 of age. Cows receiving KV vaccinations have ~60% more colostral IgG than cows receiving MLV vaccination (P = 0.02). Experiment 3 observed postweaning feed efficiency and ruminal fermentation of calves from experiment 2. Cow vaccine treatment did not affect average daily gain, gain:feed, ruminal fermentation, or metabolites (P &amp;gt; 0.05). An immune challenge was conducted in experiment 4. Calves (n = 8) were early-weaned and inoculated with BVDV Type 2a strain 1373. Samples were collected over 28 days to evaluate blood counts, virus isolation, and metabolites. A tendency for increased clinical scores, including mucosal discharge, and temperatures were observed for calves born to MLV cows (P = 0.08). Calves born to KV cows had increased leukocyte and lymphocyte concentrations compared to MLV calves (P ≤ 0.03). Overall, blood metabolites (glucose, non-esterified fatty acids, and blood urea nitrogen) were unaffected by treatment (P ≥ 0.8), however, metabolites did differ by day post-challenge (P ≤ 0.01). Metabolites were altered by the viral challenge and indicate the nutritional status of the animal shifted to support immune responses. Vaccination treatment had little influence on the calf’s ability to mount an immune response. These four studies indicate that both KV and MLV vaccination programs can be used to protect against BVDV without negatively impacting cow longevity, calf growth performance, and calf immunocompetence.

An Assessment of Secondary Clinical Disease, Milk Production and Quality, and the Impact on Reproduction in Holstein Heifers and Cows from a Single Large Commercial Herd Persistently Infected with Bovine Viral Diarrhea Virus Type 2.

The aim of this study was to evaluate secondary clinical disease, milk production efficiency and reproductive performance of heifers and cows persistently infected (PI) with bovine viral diarrhea virus type 2 (BVDV type 2). PI animals (n = 25) were identified using an antigen capture ELISA of ear notch samples. They were distributed into three age groups: ≤ 12 (n = 8), 13 to 24 (n = 6) and 25 to 34 (n = 11) months old. A control group of BVDV antigen ELISA negative female cattle that were age matched to the PI animals was utilized from the same herd. The PI group had a 1.29 higher odds ratio for diarrhea than controls (p = 0.001, IC95% = 1.032–1.623) and 1.615 greater chance of developing bovine respiratory disease (BRD) (p = 0.012, IC95% = 1.155–2.259). The age at first insemination (p = 0.012) and number of insemination attempts required to establish the first pregnancy (p = 0.016) were both higher for PI than controls. Milk production was higher for control cows than PI cows during most of the sampling periods. Somatic cell counts (SCC) were higher in PI cows than the controls at all sampling points across lactation (p ≤ 0.042). PI cattle had a higher incidence of disease, produced less milk, a higher SCC, and poorer reproductive performance than control cattle in this study.

320 Carcass characteristics of Bos indicus-Bos taurus steers following BVDV type 1b challenge

Abstract Bovine Viral Diarrhea virus (BVDV), is a component of bovine respiratory disease (BRD) worldwide. Documentation of animal genetic influences and performance variability specific to BVDV challenge is limited. This study evaluated individual animal effects in the 14 d following BVDV Type 1b intranasal challenge in yearling, Nellore-Angus (Bos indicus-Bos taurus) F2 and F3 crossbred steers (n = 363) on carcass traits 180 d post-challenge. Prior to challenge steers were confirmed to be free of BVDV infection with families balanced across non-vaccinated control, killed (KV), or modified-live (MLV) commercial BRD vaccines. Hot carcass weight (HCW), adjusted fat thickness (AFT), longissimus muscle area (REA) and marbling score (MARB) were analyzed through mixed models with sire and pen(year) as random effects; potential fixed effects of vaccine, type of cross, pyrexia status, clinical sign presentation, and levels of feed intake and ADG 14 d post-challenge were investigated. Vaccine influenced AFT (P = 0.016); MLV steers had 0.26 cm less AFT than KV steers. Marbling was affected by type of cross (P = 0.023) with up to 0.60 marbling scores higher (P &amp;lt; 0.05) in some parental combinations; an interaction between type of cross and pyrexia status also affected MARB (P = 0.017) with one parental combination having higher MARB associated with pyrexia. Hot carcass weight was not affected by pyrexia, but was affected by feed intake (P = 0.019), with steers in the highest vs. lowest category averaging 24.0 kg heavier. No animals presented morbidity signs severe enough for therapeutic treatment, yet presence of mild clinical symptoms affected REA (P = 0.012), resulting in 3.4 cm2 lower REA, however, this pattern was inconsistent among feed intake levels. This study affirms the complexity of health impacts on beef carcass traits and the need for improved study of subclinical illness in beef production systems.

An immunomodulatory feed additive enhances in vitro viral vaccine recall antigen responses in dairy heifers

Enhancing immunological responses to vaccination is an important goal in many herd health management systems. OmniGen-AF®(OG) is an immunomodulatory feed additive that has been shown to enhance innate immune function in ruminants and its effects on adaptive immunity require additional study. The objective of this study was to evaluate post-vaccine antibody titers and circulating cellular memory development in heifers fed OG and administered a commercially available modified-live bovine respiratory disease (BRD) vaccine. Twenty-four Holstein heifers were assigned to one of two diets for 170 days: Control TMR (CON; n = 11), or TMR plus OG (TRT; 9 g/100 kg BW/day; n = 13). Samples for hematology, serology, and cellular assays were collected on D-110, 0, 21, 42, and 60 of the trial. Heifers were administered two priming doses of a modified-live BRD vaccine, with a third dose given on D0. There were no significant differences in total WBC and absolute number or the percentage of circulating lymphocytes, monocytes, neutrophils, RBC, or platelets on D-110 through D21. On D42 and D60, CON had significantly higher numbers of lymphocytes. On D0, mean serum neutralizing (SN) titer to BHV-1 was significantly higher for CON compared to TRT. SN titers were not significantly different between CON and TRT at any other time point for BHV-1, BVDV type 1, or BVDV type 2. TRT mounted a significantly stronger recall proliferative response to 0.5 multiplicity of infection (MOI) of BHV-1, BVDV type 1 and BVDV type 2 on D42 and D60; 0.25 MOI of BVDV type 1 on D21 and D42; and 0.25 MOI BVDV type 2 on D42 compared to CON. IL-4 production induced by 0.5 and 1.0 MOI BHV-1 (D42 and D60); 0.25 MOI of BVDV type 1 (D21); and 0.25 and 0.5 MOI of BVDV type 2 (D60) were significantly higher for TRT than CON. IL-17 production induced by 0.25 MOI of BVDV type 1 was significantly higher on D60 for TRT compared to CON. IFN-gamma and IL-10 were not significantly different between treatments. These data indicate feeding OG has a beneficial effect on responses to vaccine antigens in Holstein dairy heifers.

Vitamin E supplementation strategies during feedlot receiving: effects on beef steer performance, antibody response to vaccination, and antioxidant defense1.

This study utilized 204 Angus-based beef steers (249 ± 23 kg SD) from a single ranch with initial serum α-tocopherol concentrations of 3.9 ± 1.0 mg/L to determine the effect of varying doses of vitamin E (VE) on feedlot performance, antibody response to vaccination, and antioxidant defense. Seven days after arrival, steers were blocked by body weight and weaning protocol (preweaned, unweaned heavy, and unweaned light) and randomly assigned to pens within blocks (12 pens per block). Preweaned steers had been weaned for approximately 35 d prior to arrival, and unweaned steers were weaned when leaving the origin ranch. Pens within block were randomly assigned to supplemental VE (ROVIMIX E-50 Adsorbate, DSM Nutritional Products, Heerlen, The Netherlands) treatments (n = 9 pens per treatment): no supplemental VE (CON), 25 IU/kg dry matter (DM; LOW), 500 IU per steer daily (MED), or 1,000 IU per steer daily (HIGH). Back-calculated supplemental VE intake was 0, 151 (24.8 IU/kg DM), 484, and 995 IU/d for CON, LOW, MED, and HIGH, respectively. On day 6, all steers received a booster vaccine against bovine viral diarrhea virus (BVDV; Bovi-Shield Gold, One Shot, Zoetis, Parsippany, NJ). Steers were weighed on day -1, 0, 14, 26, and 27. One steer per pen representative of the average body weight of the pen was chosen as a sampling animal for blood (day -1, 6, 14, 26, and 28) and liver (day -3 and 24). Data were analyzed as a randomized complete block design using Proc Mixed of SAS with pen as the experimental unit and the fixed effects of treatment and block. Linear, quadratic, and cubic contrast statements were constructed using Proc IML; morbidity data were analyzed using Proc Glimmix. Day 24 liver and day 26 serum α-tocopherol concentrations were linearly increased by supplemental VE (P < 0.01). Supplemental VE did not affect DM intake, average daily gain, or gain:feed from day 0 to 27 (P ≥ 0.37), or the percentage of steers treated for respiratory disease (P ≥ 0.44). Day 24 liver glutathione concentrations decreased linearly due to supplemental VE (P ≤ 0.02). Total- and Mn-superoxide dismutase activities were quadratically affected by supplemental VE (P ≤ 0.07), with MED steers exhibiting the greatest activity. Over time, BVDV type 1 and 2 antibody titers numerically decreased, whereas the decrease in BVDV type 1 titers was lesser for HIGH steers (linear P = 0.04). Increasing doses of VE improved VE status but did not affect overall receiving period performance in steers with minimal to adequate VE status upon arrival.

Association between bovine viral diarrhea virus load in subsets of peripheral blood mononuclear cells (PBMC) in persistently infected animals and health outcome

Abstract Bovine viral diarrhea virus (BVDV) can cause acute and persistent infections. BVDV acute infection results in generalized immunosuppression characterized by lymphocytopenia typically associated with depletion of CD4+ and CD8+ T cells. BVDV persistent infection is the result of immune tolerance and is not associated with lymphocytopenia. The health outcome of persistently infected (PI) calves varies widely; some die of mucosal disease, some succumb to ill thrift and others survive to adulthood. Detection of BVDV at the single lymphoid cell level is important to the study of subsets of PBMC in acute and persistent infections, however there are few methods available for the detection and quantification of BVDV at the single cell level. To circumvent this difficulty, a novel PrimeFlow RNA assay using in-situ detection of BVDV was developed. This assay was used to evaluate differences in viral distribution within subsets of PBMC over time in PI calves carrying one of two different species of BVDV (type 1 and type 2). Calves were sampled at 3 different time points at least one month apart. During the course of the study, a subset of the calves died from ill thrift. Mucosal disease was not indicated in any of the deaths. Using RNA probes specific for the BVDV Npro-Erns coding region for each respective virus, BVDV RNA was detected in all PBMC of PI that appeared clinically healthy. Calves that succumbed to ill thrift were found to have no or little virus in T cells. The clearance of virus from T cells suggests a breakdown in immune tolerance in these calves. This is the first report of an association between viral load in the T cell populations and survival in PI calves.

Antibody titers to vaccination are not predictive of level of protection against a BVDV type 1b challenge in Bos indicus - Bos taurus steers

Subclinical illness associated with infection is thought to reduce performance and increase production costs in feedlot cattle, but underlying components remain largely unidentified. Vaccination is frequently used in feedlot settings but producers lack metrics that evaluate the effectiveness of vaccination programs. The goal of this study was to determine if levels of serum neutralizing antibody titers were predictive of levels of vaccine protection in a commercial setting. During this four-year study, Angus-Nellore steers housed in a production feedlot setting were assigned to 1 of 3 vaccine treatments: killed vaccine (kV), modified live virus (MLV) vaccine, or no vaccine (control), and were challenged with a noncytopathic 1b field strain of bovine viral diarrhea virus. Rectal temperature and levels of circulating lymphocytes and platelets were monitored following challenge. While no animals were diagnosed as clinically ill with respiratory disease, indicators of disease (pyrexia, lymphopenia, and thrombocytopenia) were observed. The MLV treatment elicited higher antibody titers to the vaccination than the kV, and calves in the MLV treatment had higher mean titers at challenge. The year that elicited the highest antibody response to the vaccination and the year with the lowest frequency of phenotypic responses to the challenge were not concurrent. The MLV treatment had the highest proportion, 34.68%, of animals that were protected against the challenge regardless of the pre-challenge antibody titer and had the fewest number of lymphopenia cases in response to the challenge. Both vaccine treatments mitigated thrombocytopenia when compared to the control treatment, and the MLV treatment reduced lymphopenia; however, these symptoms were not completely eliminated in vaccinated animals. Pyrexia was present in 40.11% of the animals, but no difference in the frequency of cases between treatments was observed. Pre-challenge vaccination response was not indicative of the level of protection nor was anamnestic antibody response correlated with health status.

One year duration of immunity of the modified live bovine viral diarrhea virus type 1 and type 2 and bovine herpesvirus-1 fractions of Vista® Once SQ vaccine

Three studies were performed to determine the duration of immunity of the bovine viral diarrhea virus type 1 and type 2 (BVDV-1 and BVDV-2) and bovine herpesvirus-1 (BHV-1) fractions of a commercially prepared modified-live vaccine. Vista® Once SQ (Vista®) vaccine contains five modified-live viruses, BVDV-1, BVDV-2, BHV-1, bovine respiratory syncytial virus, and bovine parainfluenza 3 virus, and two modified-live bacteria, Pasteurella multocida and Mannheimia haemolytica. For all three studies, calves were administered a single dose of vaccine or placebo vaccine subcutaneously, and were challenged with one of the three virulent viruses at least one year following vaccination. Calves were evaluated daily following challenge for clinical signs of disease associated with viral infection, nasal swab samples were evaluated for virus shedding, and serum was tested for neutralizing antibodies. Following the BVDV-1 and BVDV-2 challenges, whole blood was evaluated for white blood cell counts, and for the BVDV-2 study, whole blood was also evaluated for platelet counts. Calves vaccinated with BVDV type 1a, were protected from challenge with BVDV type 1b, and had significant reductions in clinical disease, fever, leukopenia, and virus shedding compared to control calves. Vaccinated calves in the BVDV-2 study were protected from clinical disease, mortality, fever, leukopenia, thrombocytopenia, and virus shedding compared to controls. Vaccinated calves in the BHV-1 study were protected from clinical disease and fever, and had significantly reduced duration of nasal virus shedding. These three studies demonstrated that a single administration of the Vista® vaccine to healthy calves induces protective immunity against BVDV-1, BVDV-2 and BHV-1 that lasts at least one year following vaccination.

Npro of Bungowannah virus exhibits the same antagonistic function in the IFN induction pathway than that of other classical pestiviruses

Bungowannah virus is the most divergent atypical pestivirus that had been detected up to now, and does not fit into any of the four approved species: Bovine viral diarrhea virus type 1 (BVDV-1) and type 2 (BVDV-2), Classical swine fever virus (CSFV) and Border disease virus (BDV). However, the presence of Npro and Erns coding regions, which are unique to pestiviruses, provides clear evidence of a pestivirus. Nevertheless, the amino acid identity of Bungowannah virus Npro and BVDV-1 Npro (strain CP7) is only 51.5%. By using a BVDV-1 backbone, a novel chimeric construct was generated, in which the genomic region encoding the non-structural protein Npro was replaced by that of Bungowannah virus (CP7_Npro-Bungo). In vitro studies of CP7_Npro-Bungo revealed autonomous replication with the same efficacy as the BVDV backbone CP7 and infectious high-titer virus could be collected. In order to compare the ability of interferon (IFN) suppression, two reporter gene assays, specific for type-I IFN, were carried out. In virus-infected cells, no significant difference in blocking of IFN expression between the parental virus CP7, Bungowannah virus and the chimeric construct CP7_Npro-Bungo could be detected. In contrast, an Npro deletion mutant showed an impaired replication in bovine cells and a marked type-I IFN response.Taken together, our findings reveal the compatibility of non-structural protein Npro of atypical Bungowannah virus with a BVDV type 1 backbone and its characteristic feature as an inhibitor of type-I IFN induction with an inhibitor-activity comparable to other pestiviruses.

An ultra-sensitive detection of a whole virus using dual aptamers developed by immobilization-free screening

In this study, we successfully developed a ssDNA aptamer pairs by using an advanced immobilization-free SELEX method with affinity-based selection and counter-screening process at every round. By implementing this method, two different aptamers specifically binding to bovine viral diarrhea virus type 1(BVDV type 1) with high affinity were successfully screened. This aptamer pair was applied to ultrasensitive detection platform for BVDV type 1 in a sandwich manner. The ultrasensitive detection of BVDV type 1 using one of aptamers conjugated with gold nanoparticles was obtained in aptamer–aptamer sandwich type sensing format, with the limit of detection of 800copies/ml, which is comparable to a real-time PCR method.

Immune, health, and growth responses of beef calves administered modified-live virus respiratory vaccine in the presence of maternal antibody versus a traditional vaccination regimen

Typical preconditioning guidelines recommend that calves be vaccinated against respiratory and other pathogens at or near weaning (~205 days) because of the historical belief that maternal antibodies from colostrum ingested by the neonatal calf may interfere with the immune response to vaccination. However, recent research investigating vaccination during the presence of maternal antibodies suggests that neonatal calves vaccinated with a modified-live virus (MLV) vaccine are protected from subsequent BVDV challenge and immature calves vaccinated at 67 days of age develop both an initial and anamnestic antibody response. Our objective was to determine the effects of administration of a pentavalent MLV respiratory vaccine to calves at approximately 60 days of age versus at a traditional vaccination regimen age (near weaning) on health, growth performance, and BVDV type la-specific antibody titers and T cell activation.

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

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

EPIDEMIOLOGICAL ASPECT OF BOVINE VIRAL DIARRHEA VIRUS- II INFECTION IN DAIRY CATTLE

The purpose of this study was to characterize the clinical and virologic features of the mucosal and thrombocytopenic BVDV infection in infected dairy cattle. Strategy of examination included clinical examination of diseased animals, serum samples (n=31) represented all diseased cattle, milk samples (n=8) represented clinically diseased cattle and vaginal swabs (n=8) from the hemorrhagic diseased and aborted cattle were tested. An international reference strain (NADL: National Animal Disease Laboratory) and local cytopathic BVDV genotype-II strain (Behera-CP 58/99) were used as positive controls. The virus was isolated from the 8 vaginal swabs and 5 out of the 8 milk samples. All the isolates were ncp that no CPEs were noticed over the 3 passages. By specific BVDV genotype -II monoclonal antibodies (MAbs) against gp53, the viral antigen was identified using Fluorescence isothiocyanate (FITC)-conjugated anti-bovine IgG (specific intra cytoplasmic fluoresce granules) and horseradish peroxidase (HRP)-conjugated anti-bovine IgG (specific intra cytoplasmic brown granules) were detected. By enzyme linked immunosorbant assay (ELISA) technique, all serum samples were positive against the BVDV that had neutralizing antibodies titer ranges from ≥ 1/128 to ≥ 1/512. In conclusion, BVDV type -II do exist in cattle population and the understanding the molecular epidemiology is fundamental. Improved diagnostic and control strategies are essential to reduce losses inflected by BVDVs infection.

Comparison of humoral and cellular immune responses to a pentavalent modified live virus vaccine in three age groups of calves with maternal antibodies, before and after BVDV type 2 challenge

The aim of this study was to evaluate the ability of a pentavalent (BVDV types 1 and 2, BHV-1, BRSV, and PI-3) modified live virus (MLV) vaccine given to 1–2-, 4–5-, and 7–8-week-old calves with maternal antibodies to induce humoral and cellular immune responses and protect calves from virulent BVDV type 2. Eight calves in each age group were vaccinated and four served as controls. All calves were challenged intranasally with BVDV type 2, 12 weeks after vaccination. SVN titers to all five viruses declined in all groups after vaccination (except 4–5-week-old calves to BVDV type 1). After challenge, the SVN titers for both types of BVDV showed anamnestic responses in calves vaccinated at 4–5 and 7–8 weeks, but not at 1–2 weeks of age. In all groups, T cell subsets responded specifically to BVDV types 1 and 2 but not to BHV-1, BRSV, or PI-3 after vaccination by increasing their expression of activation markers (CD25, IFN-γ and IL-4). All vaccinated calves were significantly protected from BVDV type 2 challenge.

Serological survey for antibodies against pestiviruses in sheep in Austria

The prevalence of antibodies to pestiviruses was investigated in 4931 sheep, in 377 flocks, in four federal states of Austria, by means of an indirect elisa that detected antibodies to...

Bovine viral diarrhoea virus infection in livestock in southern Africa.

Abstract Bovine viral diarrhoea virus (BVDV) is viewed as an economically important pathogen of cattle in southern Africa. During the last decade, a high priority was given to the diagnosis and control of BVDV-associated diseases, which was evident from the attention it received at conferences and meetings of both practitioners and producers. The presence of BVDV in southern Africa has been known since the early 1970s through serological surveys but only a few documented reports confirming its presence through virus isolation and correlation with clinical disease are available. Of the clinical signs in cattle from which virus was isolated, respiratory signs were the most frequent, followed by diarrhoea. Bovine viral diarrhoea viruses obtained by isolation in tissue culture or detected by means of antigen capture ELISA from clinically sick cattle were characterized on the basis of analysis of the 5′-non-translated (5′-NTR) region of the genome. All the BVDV strains analysed belong to subgroups of BVDV genotype 1. No association could be demonstrated between the geographic origins of the isolates. The findings suggest that an extensive genetic diversity can be found within BVDV type 1 isolates from southern Africa. Isolates that group with the classical BVDV type 1 strains, particularly of American origin, coexist with variants that appear to represent a local genetic pool and/or variants evolving from the classical strains.

Genetic typing of bovine viral diarrhoea virus: most Slovenian isolates are of genotypes 1d and 1f

A selection of 43 bovine viral diarrhoea viruses isolated from mainly persistently infected cattle on 23 Slovenian farms between 1997 and 2001 were characterised genetically. Viral RNA was extracted from infected cell cultures, reverse transcribed and amplified by PCR with primers targeting the 5′-UTR and the N pro gene, followed by direct sequencing of purified PCR products obtained for both genomic regions. The N pro sequences provided the best genetic resolution, and gave also higher statistical support for phylogenetic classification of the viruses. Thirty-eight of the Slovenian isolates were of genetic subtypes 1d and 1f, four were 1b, and one subtype 1g. No BVDV type 2 viruses were found. This genetic prevalence matched those previously reported for neighbouring countries, as opposed to findings reported for more distant European countries, e.g. France, Spain and the UK. From eight cattle herds several virus isolates were analysed; with one exception all isolates from each herd were of the same genetic group. Extended sequencing of the N pro and part of the C gene of virus isolates with identical 5′-UTR sequences allowed differentiation between isolates obtained at different times from one herd.

Molecular analysis of bovine viral diarrhoea virus isolates from South Africa.

The presence of bovine viral diarrhoea virus in South Africa has been confirmed by several serological surveys. However, little is known about its biological properties. Twenty five isolates obtained by isolation in tissue culture and detected by means of the antigen capture ELISA from clinically sick cattle and from foetal calf serum in South Africa were characterized on the basis of analysis of the 5' non-translated (NTR) region of the genome. A reverse-transcription polymerase chain reaction (RT-PCR) was used to amplify specific sequences from the 5'NTR of the genome. The oligonucleotide primers corresponding to positions 105-125 and 399-378, respectively, in the sequence of BVDV strain NADL were used to generate the PCR products. Both strands were sequenced directly with these primers and fluorescence-labelled dideoxynucleotides in an automated nucleic acid sequencer. Reference strains of pestiviruses [(BVDV type I, BVDV type II, border disease virus (BDV) and hog cholera virus (HCV)] and isolates from a previous investigation on BVDV in southern Africa were included for comparative purposes. All the BVDV strains obtained during this study belong to subgroups of BVDV genotype I. No association could be demonstrated between the geographic origin of the isolates. A number of isolates formed another branch separate from the existing branches Ia, Ib and Ic. These findings suggest that extensive genetic diversity can be found within BVDV type I isolates from southern Africa. Isolates that group with the classical BVDV type I strains, particularly of American origin, coexist with variants that appear to represent a local genetic pool and or variants evolving from the classical strains.

Genetic typing of ruminant pestivirus strains from Northern Ireland and the Republic of Ireland

A study was performed to investigate the genotypes and sub-groups of pestiviruses present in ruminants in Ireland. These comprised one ovine and eighteen bovine pestiviruses from Northern Ireland and six bovine pestiviruses from the Republic of Ireland. A 288 base pair (bp) portion of the 5′-non coding region (5′-NCR) from each of 25 pestiviruses collected over a period of 31 years was amplified by reverse-transcription-polymerase chain reaction (RT - PCR) and the product directly sequenced. From each pestivirus, nucleotide sequences corresponding to bases 130 to 374 of the 5′-NCR of NADL were aligned and compared with each other and with the corresponding sequences of a number of reference, field or vaccinal strains of BVDV types I and II, border disease virus and classical swine fever virus. All of the 25 sequenced pestiviruses were found to be BVDV type Ia. These were closely related to the constituent viruses of the 2 inactivated vaccines currently licenced for use in Northern Ireland and to recent bovine isolates from England.