Virus neutralising antibodies against 22 bovine viral diarrhoea virus isolates in vaccinated calves.

Seven of nine colostrum deprived calves, free from bovine viral diarrhoea virus (BVDV), were vaccinated with a commercially available vaccine containing two inactivated strains of BVDV, an inactivated strain of bovine herpesvirus-1 and modified-live strains of bovine respiratory syncytial virus and para-influenza-3 virus. The two other calves were kept as controls. The virus neutralising (VN) antibodies induced by vaccination were tested against 22 antigenically diverse BVDV isolates, including reference strains and field isolates, both cytopathic and non-cytopathic, as well as genotypes I and II. The strains were isolated in Belgium, France, Germany, the United Kingdom and the USA. While there were variations in the VN titres of the individual calves against all the strains, serum from the seven animals neutralised 20 or more of the strains tested. From the results, it can be concluded that the vaccine can stimulate the production of VN antibodies capable of neutralising a wide range of European and American isolates of BVDV, including genotypes I and II.     

Virus neutralizing antibodies against a panel of 18 BVDV isolates in calves vaccinated with Rispoval RS-BVD

Seven of nine colostrum-deprived calves, free from infection with bovine virus diarrhoea virus (BVDV), were vaccinated with Rispoval RS-BVD on two occasions, 21 days apart, while the other two were kept as BVDV infection controls. The virus neutralizing (VN) serum antibodies induced by vaccination were tested for their ability to neutralize 18 European BVDV isolates, including laboratory reference strains and recent field isolates, both cytopathic and non-cytopathic biotypes as well as genotypes I and II. The strains were isolated in Belgium, France, Germany and the United Kingdom. While there were large variations in the vaccine-induced VN titres of the individual calves against all the strains, e.g. the titres against Osloss NCP, the European reference strain ranged from 1.7 to 6.7 (1:log2), serum from each animal was capable of neutralizing between nine and all 18 of the strains tested. Nevertheless, from the results of this study, it can be concluded that in colostrum-deprived BVDV seronegative calves, Rispoval RS-BVD can stimulate the production of VN antibodies capable of neutralizing a wide range of antigenically diverse European isolates of BVDV, including genotypes I and II.     

Virus Neutralizing Antibodies Against a Panel of 18 BVDV Isolates in Calves Vaccinated with Rispoval™ RS‐BVD

Seven of nine colostrum‐deprived calves, free from infection with bovine virus diarrhoea virus (BVDV), were vaccinated with Rispoval^? RS‐BVD on two occasions, 21 days apart, while the other two were kept as BVDV infection controls. The virus neutralizing (VN) serum antibodies induced by vaccination were tested for their ability to neutralize 18 European BVDV isolates, including laboratory reference strains and recent field isolates, both cytopathic and non‐cytopathic biotypes as well as genotypes I and II. The strains were isolated in Belgium, France, Germany and the United Kingdom. While there were large variations in the vaccine‐induced VN titres of the individual calves against all the strains, e.g. the titres against Osloss NCP, the European reference strain ranged from 1.7 to 6.7 (1 : log₂), serum from each animal was capable of neutralizing between nine and all 18 of the strains tested. Nevertheless, from the results of this study, it can be concluded that in colostrum‐deprived BVDV seronegative calves, Rispoval^? RS‐BVD can stimulate the production of VN antibodies capable of neutralizing a wide range of antigenically diverse European isolates of BVDV, including genotypes I and II.     

Humoral immune response and assessment of vaccine virus shedding in calves receiving modified live virus vaccines containing bovine herpesvirus-1 and bovine viral diarrhoea virus 1a

Susceptible calves were administered modified live virus (MLV) vaccines containing bovine herpesvirus-1 (BHV1) and bovine viral diarrhoea type 1 (BVDV1a) strains intramuscularly, with one vaccine containing both MLV and inactivated BHV-1 and inactivated BVDV1a. There was no evidence of transmission of vaccine (BHV-1 and BVDV1a) strains to susceptible non-vaccinated controls commingled with vaccinates. No vaccinates had detectable BHV-1 in peripheral blood leucocytes (PBL) after vaccination. Each of three vaccines containing an MLV BVDV1a strain caused a transient BVDV vaccine induced viremia in PBL after vaccination, which was cleared as the calves developed serum BVDV1 antibodies. The vaccine containing both MLV and inactivated BHV-1 induced serum BHV-1 antibodies more rapid than MLV BHV-1 vaccine. Two doses of MLV BHV-1 (days 0 and 28) in some cases induced serum BHV-1 antibodies to higher levels and greater duration than one dose.     

Transmission of Bovine viral diarrhea virus 1b to susceptible and vaccinated calves by exposure to persistently infected calves

Bovine viral diarrhea virus (BVDV) persistently infected (PI) calves represent significant sources of infection to susceptible cattle. The objectives of this study were to determine if PI calves transmitted infection to vaccinated and unvaccinated calves, to determine if BVDV vaccine strains could be differentiated from the PI field strains by subtyping molecular techniques, and if there were different rates of recovery from peripheral blood leukocytes (PBL) versus serums for acutely infected calves. Calves PI with BVDV1b were placed in pens with nonvaccinated and vaccinated calves for 35 d. Peripheral blood leukocytes, serums, and nasal swabs were collected for viral isolation and serology. In addition, transmission of Bovine herpes virus 1 (BHV-1), Parainfluenza-3 virus (PI-3V), and Bovine respiratory syncytial virus (BRSV) was monitored during the 35 d observation period. Bovine viral diarrhea virus subtype 1b was transmitted to both vaccinated and nonvaccinated calves, including BVDV1b seronegative and seropositive calves, after exposure to PI calves. There was evidence of transmission by viral isolation from PBL, nasal swabs, or both, and seroconversions to BVDV1b. For the unvaccinated calves, 83.2% seroconverted to BVDV1b. The high level of transmission by PI calves is illustrated by seroconversion rates of nonvaccinated calves in individual pens: 70% to 100% seroconversion to the BVDV1b. Bovine viral diarrhea virus was isolated from 45 out of 202 calves in this study. These included BVDV1b in ranch and order buyer (OB) calves, plus BVDV strains identified as vaccinal strains that were in modified live virus (MLV) vaccines given to half the OB calves 3 d prior to the study. The BVDV1b isolates in exposed calves were detected between collection days 7 and 21 after exposure to PI calves. Bovine viral diarrhea virus was recovered more frequently from PBL than serum in acutely infected calves. Bovine viral diarrhea virus was also isolated from the lungs of 2 of 7 calves that were dying with pulmonary lesions. Two of the calves dying with pneumonic lesions in the study had been BVDV1b viremic prior to death. Bovine viral diarrhea virus 1b was isolated from both calves that received the killed or MLV vaccines. There were cytopathic (CP) strains isolated from MLV vaccinated calves during the same time frame as the BVDV1b isolations. These viruses were typed by polymerase chain reaction (PCR) and genetic sequencing, and most CP were confirmed as vaccinal origin. A BVDV2 NCP strain was found in only 1 OB calf, on multiple collections, and the calf seroconverted to BVDV2. This virus was not identical to the BVDV2 CP 296 vaccine strain. The use of subtyping is required to differentiate vaccinal strains from the field strains. This study detected 2 different vaccine strains, the BVDV1b in PI calves and infected contact calves, and a heterologous BVDV2 subtype brought in as an acutely infected calf. The MLV vaccination, with BVDV1a and BVDV2 components, administered 3 d prior to exposure to PI calves did not protect 100% against BVDV1b viremias or nasal shedding. There were other agents associated with the bovine respiratory disease signs and lesions in this study including Mannheimia haemolytica, Mycoplasma spp., PI-3V, BRSV, and BHV-1.     

Serological and molecular diagnosis of bovine viral diarrhoea virus and evidence of other viral infections in dairy calves with respiratory disease in Venezuela

An investigation based on 2 studies was carried out to assess the involvement of bovine virus diarrhoea virus (BVDV), bovine herpesvirus type 1 (BHV-1), and bovine respiratory syncytial virus (BRSV) in calf respiratory disease in dairy farms in Venezuela. In the first study, 8 farms were selected and paired serum samples from 42 calves with respiratory disease were tested by ELISA for antibodies to the 3 viruses. Seroconversion to BVDV, BHV-1, and BRSV was found to 5, 2, and 6 farms out of the 8, respectively. The proportion of calves that showed seroconversion to BVDV, BHV-1, and BRSV were 19%, 14%, and 26%, respectively. In the second study, another farm having previous serological evidence of BVDV infection was selected. The decline of maternal antibodies against BVDV was monitored in 20 calves and the half-life of maternal antibodies was 34 +/- 12 days presumably indicating an early natural infection with BVDV. Furthermore, sera free of BVDV antibodies that were collected in studies 1 and 2 and were assayed for the presence of BVDV by nested RT-PCR. Two BVDV strains were detected and compared to those of ruminant and porcine pestiviruses. Both strains were assigned to subgroup Ib of type I BVDV. This investigation provides information on BVDV genotypes circulating in Venezuela and may contribute to the establishment of official control programmes against the viruses studied.     

Disease in a dairy herd associated with the introduction and spread of bovine virus diarrhoea virus

In January 1982 an outbreak of diarrhoea among adult dairy cows in a closed herd of approximately 200 milking animals was shown to be caused by the introduction of bovine virus diarrhoea virus (BVDV). Affected animals showed a significant reduction in milk yield. One animal died and four were culled. Eight cows aborted and one weak calf was born. Of 121 calves born that year, 26 died, mostly from pneumonia, but five aged from three weeks to five months had enteric lesions of mucosal disease. Subsequent investigations of the whole herd in 1983 and 1984 showed that virus spread among the adults was slow and that BVDV continued to make a major contribution to calf losses. Again the greatest cause of loss was suppurative or fibrinous pneumonia. Overall, BVDV was isolated from 36 animals. Isolation of virus from a wide range of tissues of individual animals confirmed that they were viraemic at death. Viruses from calves dying of pneumonia and from aborted fetuses were non-cytopathic in tissue culture. Isolates showing varying degrees of cytopathogenicity were obtained only from tissues of one calf with a congenital neurological defect and the seven animals with enteric lesions consistent with a diagnosis of mucosal disease. Blood from all 89 BVDV antibody-free animals older than three months was tested for the presence of BVDV. Altogether, 12 calves were identified as persistently viraemic and all were apparently healthy when bled. Only two matured normally, four grew poorly and six died.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bovine viral diarrhea virus (BVDV) 1b: predominant BVDV subtype in calves with respiratory disease

The prevalence of bovine viral diarrhea virus (BVDV) infections was determined in 2 groups of stocker calves with acute respiratory disease. Both studies used calves assembled after purchase from auction markets by an order buyer and transported to feedyards, where they were held for approximately 30 d. In 1 study, the calves were mixed with fresh ranch calves from a single ranch. During the studies, at day 0 and at weekly intervals, blood was collected for viral antibody testing and virus isolation from peripheral blood leukocytes (PBLs), and nasal swabs were taken for virus isolation. Samples from sick calves were also collected. Serum was tested for antibodies to bovine herpesvirus-1 (BHV-1), BVDV1a, 1b, and 2, parainfluenza 3 virus (PI3V), and bovine respiratory syncytial virus (BRSV). The lungs from the calves that died during the studies were examined histopathologically, and viral and bacterial isolation was performed on lung homogenates. BVDV was isolated from calves in both studies; the predominant biotype was noncytopathic (NCP). Differential polymerase chain reaction (PCR) and nucleic acid sequencing showed the predominant subtype to be BVDV1b in both studies. In 1999, NCP BVDV1b was detected in numerous samples over time from 1 persistently infected calf; the calf did not seroconvert to BVDV1a or BVDV2. In both studies, BVDV was isolated from the serum, PBLs, and nasal swabs of the calves, and in the 1999 study, it was isolated from lung tissue at necropsy. BVDV was demonstrated serologically and by virus isolation to be a contributing factor in respiratory disease. It was isolated more frequently from sick calves than healthy calves, by both pen and total number of calves. BVDV1a and BVDV2 seroconversions were related to sickness in selected pens and total number of calves. In the 1999 study, BVDV-infected calves were treated longer than noninfected calves (5.643 vs 4.639 d; P = 0.0902). There was a limited number of BVDV1a isolates and, with BVDV1b used in the virus neutralization test for antibodies in seroconverting calves' serum, BVDV1b titers were higher than BVDV1a titers. This study indicates that BVDV1 strains are involved in acute respiratory disease of calves with pneumonic Mannheimia haemolytica and Pasteurella multocida disease. The BVDV2 antibodies may be due to cross-reactions, as typing of the BVDV strains revealed BVDV1b or 1a but not BVDV2. The BVDV1b subtype has considerable implications, as, with 1 exception, all vaccines licensed in the United States contain BVDV1a, a strain with different antigenic properties. BVDV1b potentially could infect BVDV1a-vaccinated calves.     

Detection of bovine viral diarrhoea virus in specimens from cattle in South Africa and possible association with clinical disease

Studies covering all aspects of bovine viral diarrhoea virus (BVDV) have been conducted in several countries in Europe, Asia and America. In southern Africa, more information is required about the nature of BVDV infection, the prevalence of different strains and the economic importance of the disease. The presence of BVDV in southern Africa has been known since the early 1970s through serological surveys but few reports confirming its presence by virus isolation and correlation with clinical disease are available. Specimens (n = 312) collected in 1998/99, from live and dead cattle from different farming systems, were obtained from private practitioners, feedlot consultants and abattoirs throughout the country. Specimens (n = 37) from African buffaloes (Syncerus caffer) in the Kruger National Park were also included. All specimens were processed for virus isolation in cell culture with confirmation by means of immunofluorescent antibody tests and some also by means of an antigen capture ELISA. BVDV was isolated from 15 (4.7%) cattle and were all noncytopathic biotypes. BVDV was not detected in 37 lymph nodes obtained from buffaloes in the Kruger National Park. Of the clinical signs in cattle from which virus were isolated, respiratory signs was the most frequent (10/15), followed by diarrhoea (5/15). Abortion, congenital malformations, haemorrhagic diarrhoea and poor growth were also included as criteria for selection of animals for specimen collection, but no BVD viruses were isolated from cattle manifesting these clinical signs.     

Diversity among bovine pestiviruses

Bovine viral diarrhoea virus (BVDV) isolates are characterized by an important genetic, antigenic and pathogenic diversity. The emergence of new hypervirulent BVDV strains in North America has provided clear evidence of pathogenic differences between BVDV strains. The origin of BVDV diversity is related to high mutation rate occurring in RNA viruses but the consequences of mutations obviously depend on the genes which are involved. Mutations in genes encoding for structural proteins of immunological importance may have practical implications.Knowledge of BVDV diversity is important for understanding the wide variety of pathogenesis of diseases caused by the virus, for monitoring the epidemiology of the different types and for the design of optimum laboratory tests and vaccines.This review focuses on the origin and consequences of BVDV diversity with regard to pathogenesis, biotypes, and antigenic and genetic variations.     

Immune responses to non-structural protein 3 (NS3) of bovine viral diarrhoea virus (BVDV) in NS3 DNA vaccinated and naturally infected cattle

Immune responses to non-structural protein 3 (NS3) of bovine viral diarrhoea virus (BVDV) were investigated. cDNA encoding NS3 from type 1a BVDV was used to vaccinate five calves, another five calves remained unvaccinated. Three weeks after final vaccination animals were challenged intranasally with heterologous type 1a BVDV. Anti-NS3 antibodies were detected in only one animal post-vaccination. Partial protection from virus challenge was observed in the vaccinates. Virus was not isolated from nasal mucosa of two vaccinates, and virus clearance from nasal mucosa was faster in the vaccinates compared to the controls. While elevated rectal temperatures were evident in both groups 7 days post-challenge, the mean increase in the controls was twice that observed in the vaccinates. In conclusion, NS3 DNA vaccination induced humoral immunity in one calf, and prevented fever and virus establishment in the nasal mucosa in 2/5 calves, demonstrating the efficacy of NS3 vaccination, which may benefit future development of pestivirus and flavivirus vaccines.     

Effect of experimentally induced type II bovine viral diarrhea virus infection on platelet function in calves

OBJECTIVE: To evaluate platelet aggregation responses in calves experimentally infected with a thrombocytopenia-inducing type II bovine viral diarrhea virus (BVDV) isolate (BVDV 890). ANIMALS: 9 neonatal male Holstein calves. PROCEDURE: 5 calves were inoculated with BVDV 890, and 4 were used as controls. Platelet aggregation studies and attempts to isolate BVDV from platelets were performed 2 days before, the day of, and every 2 days for 12 days after inoculation. Platelet function was assessed by means of optical aggregometry, using adenosine diphosphate and platelet-activating factor as agonists. Bovine viral diarrhea virus was isolated from purified platelet preparations by use of an immunoperoxidase monolayer assay. RESULTS: Maximum percentage aggregation and slope of the aggregation curve decreased over time in calves infected with BVDV. Bovine viral diarrhea virus was not isolated from platelets from control calves, but it was isolated from infected calves from 4 through 12 days after inoculation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that platelet function may be depressed in calves infected with type II BVDV. Although the mechanism for altered platelet function was not determined, it likely involved an increase in the percentage of aged platelets in the circulation, a direct virus-platelet interaction, or an indirect virus-platelet interaction. Platelet dysfunction, in addition to thrombocytopenia, may contribute to the hemorrhagic syndrome associated with acute type II BVDV infection in calves.     

Primary bovine viral diarrhoea virus infection in calves following direct contact with a persistently viraemic calf.

Six calves, aged 24 to 58 days and not previously exposed to bovine viral diarrhoea virus (BVDV), were infected with this agent by nose-to-nose contact with a persistently BVDV viraemic calf. The study was conducted in two trials, using 3 calves in each. All 6 calves showed a peak interferon level in serum at 4 days post infection (dpi), and they seroconverted to BVDV at 16-21 dpi. The calves in trial 1 had diarrhoea for 2 or 3 days between 2 and 6 dpi and one calf again from 9 to 11 dpi. During the periods of fever, the calves were slightly depressed. Those in trial 2 were more depressed and their oral and nasal mucous membranes were reddened but they never had diarrhoea. In both trials, fever (up to 41.3 degrees C) was a prominent symptom at 8 to 9 dpi and 2 calves showed a diphasic fever course. Respiratory affection was mild and no medical treatment was required. Haematological assessment demonstrated a transient but significant leukopenia and lymphopenia at 4 dpi (P less than 0.01 and P less than 0.05 respectively) and 11 dpi (P less than 0.05 and P less than 0.01 respectively). A significant decrease in thrombocyte count was seen at 4 dpi (P less than 0.05, n = 3). This study has demonstrated that nose-to-nose contact is an effective way of transmitting BVDV from persistently infected to susceptible cattle.     

An oculo-cerebellar syndrome caused by congenital bovine viral diarrhoea virus-infection

An epizootic characterized by birth of calves severly ataxic and blind were encountered in 3 herds 7–8 months after outbreaks of bovine virus diarrhoea. Serological and virological investigations indicated introduction of bovine viral diarrhoea virus (BVDV) into previously virus-free herds, followed by transplacental virus infection of the fetuses of cows in the first trimester. Clinical, pathological, serological, and microbiological examinations were performed on 10 calves. Pathological findings included microcephaly and cerebellar hypoplasia, ocular malformations, and thymic hypoplasia. BVDV was isolated from tissue and blood of 7 calves, and 4 calves, 1 of which had not received colostrum, had virus-specific neutralizing antibodies.This is the first report on natural occurrence of congenital bovine infection with BVDV among Danish cattle herds resulting in abortion and birth of calves with severe debilitating congenital anomalies. It draws attention to the importance of this virus for bovines of all age groups.     

Humoral Immune Response and Assessment of Vaccine Virus Shedding in Calves Receiving Modified Live Virus Vaccines Containing Bovine Herpesvirus‐1 and Bovine Viral Diarrhoea Virus 1a

Susceptible calves were administered modified live virus (MLV) vaccines containing bovine herpesvirus‐1 (BHV1) and bovine viral diarrhoea type 1 (BVDV1a) strains intramuscularly, with one vaccine containing both MLV and inactivated BHV‐1 and inactivated BVDV1a. There was no evidence of transmission of vaccine (BHV‐1 and BVDV1a) strains to susceptible non‐vaccinated controls commingled with vaccinates. No vaccinates had detectable BHV‐1 in peripheral blood leucocytes (PBL) after vaccination. Each of three vaccines containing an MLV BVDV1a strain caused a transient BVDV vaccine induced viremia in PBL after vaccination, which was cleared as the calves developed serum BVDV1 antibodies. The vaccine containing both MLV and inactivated BHV‐1 induced serum BHV‐1 antibodies more rapid than MLV BHV‐1 vaccine. Two doses of MLV BHV‐1 (days 0 and 28) in some cases induced serum BHV‐1 antibodies to higher levels and greater duration than one dose.     

Practical significance of heterogeneity among BVDV strains: impact of biotype and genotype on U.S. control programs

In the early 1990s research groups in North America noted that a newly recognized severe acute form of bovine viral diarrhea virus infection, referred to as hemorrhagic syndrome or severe acute BVDV (SA BVDV), was associated with a genetically distinct subgroup of BVDV strains. This new subgroup was named BVDV genotype 2 or BVDV2. All BVDV strains previously characterized in the literature belonged to a separate genotype, BVDV1. However, not all strains identified as BVDV2 were associated with severe acute infections. If I did this deletion, I did not mean to do it. I think it was already here, though. I see there are some other big edits that I did not do; fine. Hollis subsequent surveys of BVDV strains isolated from clinical submissions to diagnostic laboratories and contaminated fetal calf serum suggested that the ratio of BVDV2 to BVDV1 strains in the U.S. approached 50%. Further, while antigenic cross reactivity is seen between BVDV1 and BVDV2 strains, a log or more difference is typically observed in titers against viruses from different genotypes. These observations prompted vaccine manufacturers in North America to produce vaccines against BVDV that contained antigens from both BVDV1 and BVDV2 strains. Under experimental conditions, these new vaccines offered improved protection against type 2 strains, however field data are still insufficient to assess their efficacy in practice. The BVDV genotypes may also be segregated into subgenotypes. Two subgenotypes of both BVDV1 (BVDV1a and BVDV1b) and BVDV2 (BVDV2a and BVDV2b) have been reported in North American. BVDV2a predominates with BVDV2b isolation a rare event. In contrast, BVDV1a and BVDV1b are both commonly isolated. Antigenic differences observed between strains from the BVDV1a and BVDV1b subgenotypes have led to the suggestion that protection may be improved by inclusion of strains from both BVDV1a and BVDV1b in vaccines in addition to BVDV2. The cost to benefit ratio of this proposal is currently a matter of debate.     

Antigenic characterization of bovine viral diarrhoea virus isolates from Spain with a panel of monoclonal antibodies

A group of 47 bovine viral diarrhoea virus (BVDV) strains isolated from a variety of bovine tissues from eight different geographical areas of Spain and two BVDV strains isolated from a cell line were characterized antigenically with a panel of 23 monoclonal antibodies (mAbs). The mAbs were directed at one of three viral proteins: E2, Erns and NS2-3. A peroxidase-linked assay was used to test the mAbs for reactivity against infected cell monolayers. The data were analysed by two computational methods: the Antigenic Distance Program (MAP) and the Phylogeny Inference Package (PHYLIP), and compared with those obtained previously using the same mAbs with other pestiviruses, including reference strains and UK field isolates. All the Spanish field strains studied appeared to be broadly similar to reference strains of BVDV and were included in the subgroup of classical BVDV, meanwhile the two strains isolated from a cell line were included in the subgroup of atypical pestiviruses.     

Pathogenicity of an Indian isolate of bovine viral diarrhea virus 1b in experimentally infected calves

The aim of this study was to determine the pathogenicity of an Indian bovine viral diarrhea virus (BVDV) 1b isolate in 7-9-months-old male calves. Infected (four) and control (two) calves were bled at three days interval for hematological, virological and serological studies until day 27. All infected calves developed respiratory illness, biphasic pyrexia, mild diarrhea, leucopenia and mild thrombocytopenia. Viraemia was demonstrated between 3 and 15dpi and the infected calves seroconverted by 15dpi. Prominent kidney lesions were endothelial cell swelling, proliferation of mesangial cells and podocytes leading to glomerular space obliteration. Degeneration and desquamation of cells lining seminiferous tubules were observed in two infected calves. Consolidation of lungs with interstitial pneumonia, mild gastroenteritis and systemic spread were also evident. It was concluded that Indian BVDV isolate induced moderate clinical disease in calves and glomerulonephritis resulting from acute BVDV infection was observed for the first time.     

Monoclonal antibodies to the p80/125 gp53 proteins of bovine viral diarrhea virus: their potential use as diagnostic reagents.

Monoclonal antibodies reactive to the bovine viral diarrhea virus (BVDV) protein gp53 were produced and characterized. These antibodies and our panel of anti-p80/125 monoclonal antibodies were tested for their cross-reactivity with 11 different North American and European (Danish) BVDV strains and isolates including viruses of both cytopathic and noncytopathic biotypes. The four anti-gp53 monoclonal antibodies were neutralizing for the homologous Danish cytopathic isolate and cross-reacted with all BVDV strains examined except for the Draper strain. Further, anti-gp53 monoclonal antibodies neutralized the majority of BVDV strains examined. The anti-p80/125 monoclonal antibodies cross-reacted with all eleven strains and isolates tested. This indicated that various strains of BVDV have common epitopes. The broad cross-reactivities demonstrated by these monoclonal antibodies suggest that a pool of these antibodies may be used for detection of BVDV cellular contamination or for virus isolation, in place of polyclonal antiserum.     

Validation of a bulk tank milk antibody ELISA to detect dairy herds likely infected with bovine viral diarrhoea virus in New Zealand

AIMS: To assess the sensitivity and specificity of a bulk tank milk (BTM) antibody enzyme-linked immunosorbent assay (ELISA) to detect likely infection of a dairy herd with bovine viral diarrhoea virus (BVDV). The ELISA was subsequently used to estimate the prevalence of likely infected herds in parts of the North Island of New Zealand. METHODS: BTM samples from 724 randomly selected dairy herds in the Waikato, Bay of Plenty and Northland regions of New Zealand were tested for BVDV antibodies. From this group, 20 herds were again randomly selected from each of the quartiles of the ELISA percentage inhibition (%INH) result. From each participant herd, serum from 15 randomly selected calves aged 6-18 months and 15 cows was collected and tested using an indirect blocking ELISA for BVDV antibodies. RESULTS: Among serum results from calves from 50 herds available for analysis, 34 (68%) herds were classified as likely non-infected (0-3 seropositive among 15 calves) and 16 (32%) as likely infected (5-15 seropositive among 15 calves). Receiver-operator characteristic (ROC) analysis identified an optimal cut-off for BTM of 80%INH associated with 81% sensitivity and 91% specificity for likely herd infection. The prevalence of BVDV antibodies in cows within herds and %INH for BVDV in bulk milk were positively correlated (p<0.01). The association between bulk milk %INH and the prevalence of BVDV antibodies in calves was stronger than the same association in cows. Based on the threshold of 80%INH, the 95% confidence interval (CI) for prevalence of likely infection in the 724 herds in the Waikato, Bay of Plenty and Northland regions of New Zealand was 12-17%. Vaccination against BVDV was not significantly associated with the likely infection status of the herd based on prevalence of BVDV antibodies among calves. CONCLUSION: An ELISA test result for BVDV antibodies in BTM >/=80%INH can be used as a threshold to indicate the presence of likely infection with BVDV in dairy herds in New Zealand, with 81% sensitivity and 91% specificity.