Antibodies against bovine herpesvirus (BHV) 5 may be differentiated from antibodies against BHV1 in a BHV1 glycoprotein E blocking ELISA

We examined whether antibodies against bovine herpesvirus (BHV) 5 cross-react with BHV1 antigens and whether they could interfere with BHV1 eradication programmes. Six calves were experimentally infected with different doses of BHV5 strain N569; homologous antibodies were first detectable on day 11 post infection; they cross-reacted in a BHV1 virus neutralisation test, in a BHV1-glycoprotein (g)-B blocking ELISA and in a BHV1-gE ELISA, but not in a BHV1-gE blocking ELISA. This study indicates that, in ongoing BHV1 eradication programmes, based on vaccines that lack gE, BHV5 infections may not lead to false-positive serological reactions in case cattle are tested for BHV1-gE antibodies by the BHV1-gE blocking ELISA; antibodies against BHV5 may be differentiated from antibodies against BHV1. The BHV1-gE blocking ELISA may, therefore, offer opportunities for the serological differentiation between BHV1 and BHV5 infections.     

Vaccination of calves with contaminated batches of bovine herpes virus 1 vaccines did not result in infection with bovine virus diarrhea virus

The aim of the experiment was to study whether bovine herpesvirus 1 (BHV1) marker vaccine batches known to be contaminated with bovine virus diarrhoea virus (BVDV) type 1 could cause BVD in cattle. For this purpose, four groups of cattle were used. The first group (n = 4 calves, the positive control group), was vaccinated with vaccine from a batch contaminated with BVDV type 2. The second group (n = 4 calves, the negative control group), was vaccinated with vaccine from a batch that was not contaminated with BVDV. The third group (n = 39 calves), was vaccinated with a vaccine from one of four batches contaminated with BVDV type 1 (seronegative experimental group). The fourth group (n = 6 seropositive heifers), was vaccinated with a vaccine from one of three batches known to be contaminated with BVDV type 1. All cattle were vaccinated with an overdose of the BHV1 marker vaccine. At the start of the experiment, all calves except those from group 4 were seronegative for BVDV and BHV1. The calves from group 4 had antibodies against BVDV, were BVDV-free and seronegative to BHV1. After vaccination, the positive control calves became severely ill, had fever for several days, and BVDV was isolated from nasal swabs and white blood cells. In addition, these calves produced antibodies to BVDV and BHV1. No difference in clinical scores of the other groups was seen, nor were BVDV or BVDV-specific antibody responses detected in these calves; however, they did produce antibodies against BHV1. The remainder of each vaccine vial used was examined for the presence of infectious BVDV in cell culture. From none of the vials was BVDV isolated after three subsequent passages. This indicates that BVDV was either absent from the vials or was present in too low an amount to be isolated. Thus vaccination of calves with vaccines from BHV1 marker vaccine batches contaminated with BVDV type 1 did not result in BVDV infections.     

Reactivation of latent bovine herpesvirus 1 in cattle seronegative to glycoproteins gB and gE

Six heifers were vaccinated intranasally with the live bovine herpesvirus 1 (BHV1) temperature-sensitive (ts) vaccine strain RBL106 within 3 weeks of birth. These calves most likely still had maternal antibodies against BHV1. Thereafter, these heifers were vaccinated several times with an experimental BHV1 glycoprotein-D (gD) subunit vaccine. At the age of 3 years these 6 heifers were seronegative in the BHV1 gB and gE blocking ELISAs, but had neutralizing antibodies against BHV1, probably induced by the vaccinations with the gD subunit vaccine. Five of these 6 heifers excreted BHV1 after treatment with dexamethasone. Restriction enzyme analysis of the genome of the excreted viruses revealed that all 5 isolates had a BHV1.1 genotype and that isolates of 3 heifers were not obviously different from the ts-vaccine strain. The restriction enzyme fragment pattern of the isolate of 1 heifer was clearly different from the pattern of the ts-vaccine strain. It is concluded that cattle can be seronegative against BHV1 gB and gE but can still carry BHV1 in a latent form. This finding strongly suggests that there are completely BHV1 seronegative cattle that are latently infected with BHV1. The impact of this finding on BHV1 eradication programmes is discussed.     

Improvement of serological discrimination between herpesvirus-infected animals and animals vaccinated with marker vaccines

Control/eradication plans of bovine herpesvirus 1 (BHV1) and suid herpesvirus 1 (SHV1) infections involve vaccination with inactivated or attenuated gE-deleted marker vaccines and associated companion serological tests to discriminate naturally infected from vaccinated animals. Blocking or competitive enzyme-linked immunosorbent assays (ELISAs) have been designed for the detection of specific antibodies against BHV1 or SHV1 gE glycoprotein. The antigen source usually consists of a crude viral preparation in which gE is associated with other envelope glycoproteins. Such assays suffer from a lack of specificity which is not due to serological cross-reactions with other pathogens. Interestingly, false-positive results occur with sera collected from multivaccinated cattle or pigs. After multivaccination with a marker vaccine, the binding of the conjugated monoclonal antibody used as a tracer, could be hampered by antibodies directed against the other viral glycoproteins.In order to validate the steric hindrance hypothesis, a simple preadsorption of such samples was carried out with a preparation of antigen devoid of gE, prior to the blocking ELISA itself. The decrease in antibody concentrations against the major glycoproteins, clearly leads to a better discrimination between positive and negative samples; that is between infected and multivaccinated animals, without significant loss of sensitivity. This experiment confirms the steric hindrance hypothesis, therefore serum preadsorption could be an easy way to improve the specificity of currently available diagnostic tests.     

Establishment of latency associated with glycoprotein E (gE) seroconversion after bovine herpesvirus 1 infection in calves with high levels of passive antibodies lacking gE antibodies

This study was conducted to investigate the glycoprotein E (gE) antibody response raised after inoculation with a low infectious dose of bovine herpesvirus 1 (BHV-1) in six calves possessing high levels of passive immunity from cows repeatedly vaccinated with gE deleted marker vaccine. Four out of the six calves developed gE antibodies 3-5 weeks after infection, whereas the two other ones remained seronegative to gE. After 5 months of infection, the six calves were treated with dexamethasone. Virus was only re-excreted by the four calves which previously seroconverted against gE. The two other calves became seronegative against BHV-1, 30-32 weeks after infection. A second dexamethasone treatment performed 11 months after infection failed to demonstrate a latent infection in these two calves. Moreover, the lack of identification of a cell-mediated immune response, after the two dexamethasone treatments, and the failure to detect BHV-1 DNA sequences in trigeminal ganglia strongly suggest that these two calves were not latently infected. In conclusion, the presence of high levels of maternal immunity lacking gE antibodies does not prevent latency after infection with a low titre of BHV-1. Moreover, latency is associated with a serological response to gE. These results confirm that the gE deletion is a good marker to identify young calves latently infected with a field virus.     

Attempted reactivation of latent bovine herpesvirus 1 infection in calves by infection with ruminant pestiviruses

Three calves, latently infected with bovine herpesvirus 1 (BHV 1), were each inoculated intranasally with 9 strains of ruminant pestivirus (BVDV). All three calves developed a biphasic pyrexia and a lymphopenia followed by a neutrophilia. They did not shed BHV 1 in their nasal secretions in the 14 days following BVDV inoculation, and their BHV 1 antibody levels remained static, as did those of 2 control calves not given BVDV. All five calves were subsequently shown to be latently infected with BHV 1 by the production of recrudescent infections following the administration of dexamethasone. BHV 1 was recovered from nasal secretions and there was a marked rise in BHV 1 antibody titres in the second week after dexamethasone administration.     

Antibody response to glycoprotein E after bovine herpesvirus type 1 infection in passively immunised, glycoprotein E-negative calves

This study was conducted to determine whether young calves with maternal antibodies against bovine herpesvirus type 1 (BHV-1) but without antibodies against glycoprotein E (gE) can produce an active antibody response to gE after a BHV-1 infection. Five calves received at birth colostrum from gE-seronegative cows which had been vaccinated two or three times with an inactivated BHV-1, gE-deleted marker vaccine. After inoculation with a wild-type virulent strain of BHV-1, all the passively immunised gE-negative calves shed virus in large amounts in their nasal secretions. All the calves seroconverted to gE within two to four weeks after inoculation and then had high levels of gE antibodies for at least four months. The development of an active cell-mediated immune response was also detected by in vitro BHV-1-specific interferon-gamma assays. All the calves were latently infected, because one of them re-excreted the virus spontaneously and the other four did so after being treated with dexamethasone. The results showed that under the conditions of this work the gE-negative marker could also distinguish between passively immunised and latently infected calves.     

Construction and characterization of a glycoprotein E gene-deleted bovine herpesvirus type 1 recombinant

OBJECTIVE: To construct and characterize a recombinant glycoprotein (g)E gene-deleted bovine herpesvirus (BHV) type 1 (BHV-1). PROCEDURE: The BHV-1 gEgene-coding region and the flanking upstream and downstream sequences were cloned. The aforementioned cloned DNA was digested with suitable enzymes to release the amino terminal two thirds of that region, and was ligated to the beta-galactosidase (beta-gal) gene. The resulting plasmid DNA was cotransfected with DNA from full-length, wild-type (WT), BHV-1 Cooper strain of the virus. Recombinant viruses expressing beta-gal (blue plaques) were plaque purified and assayed further by blot hybridization for genetic characterization and by immunoblotting for reactivity against BHV-1 gE peptide-specific rabbit polyclonal antibody. One recombinant virus, gEdelta3.1IBR, was characterized in vitro and in vivo. The ability of the recombinant virus to induce BHV-1 neutralizing antibodies in infected calves was investigated by plaque-reduction tests. RESULTS AND CONCLUSIONS: The gEdelta3.1IBR virus contained a deletion in the viral gE gene-coding sequences where a stable chimeric reporter (beta-gal) gene was inserted. One-step growth kinetics and virus yield of the recombinant and parent viruses were similar, but early after infection, the recombinant virus yield was comparatively less. After intranasal inoculation, the recombinant gEdelta3.1IBR virus replicated in the upper respiratory tract of calves, but the amount of progeny viruses produced was hundredsfold reduced, and duration of virus shedding was shorter. Results of in vivo calf experiments and serum neutralization tests indicated that deleting the gE gene has little effect on inducing neutralizing antibodies against BHV-1, but is sufficient to reduce BHV-1 virulence in calves.     

Decreased periparturient transmission of bovine leukosis virus in colostrum-fed calves

BACKGROUND: The relation between calf bovine leukosis virus (BLV) infection status and colostrum ingestion is unclear. Two conclusions have been drawn from previous studies. One suggests that colostrum ingestion transmits BLV to neonatal calves. The second suggests that colostral antibodies are protective. HYPOTHESIS: Colostrum from BLV-positive cattle is protective in naturally exposed calves. ANIMALS: Twelve colostrum-deprived Holstein calves and 20 colostrum-fed Holstein calves born to BLV-infected cows. METHODS: Prospective study. Colostrum-deprived calves were tested weekly by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) tests for BLV antibody and provirus for 12 weeks or until the animal became positive for BLV infection. Colostrum-fed calves were fed colostrum derived from BLV-positive cows. Thereafter, ELISA and PCR tests for BLV antibody and provirus were performed every other week until 2 consecutive negative ELISA tests or 1 positive PCR test was achieved. The proportion of calves that converted to BLV-positive status was calculated for each group and compared between groups by using the Fisher exact test. RESULTS: Four of 12 colostrum-deprived calves (33%) became BLV positive, whereas 0 of 20 colostrum-fed calves (0%) became BLV positive. The proportion of calves that became infected was significantly higher in the colostrum-deprived group (P = .014). CONCLUSIONS AND CLINICAL RELEVANCE: Calves born to BLV-positive cows are exposed during parturition, and a proportion of these calves will become infected with BLV. Administration of colostrum from BLV-positive cows greatly decreases the risk of infection.     

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.     

Genomic and Pathogenic Studies on a Glycoprotein E Variant Field Isolate of Bovine Herpesvirus 1

Glycoprotein E-negative (gE–) laboratory strains of bovine herpesvirus 1 (BHV-1) were recently introduced as novel marker vaccines, allowing serological discrimination between vaccinated and naturally infected animals on the basis of lack or presence of antibodies against gE epitopes. The applicability of this approach is based on the genetic stability of the gE. However, mutant field variants of BHV-1 with a variable response in anti-gE ELISA have been isolated. The molecular characterization of a gE variant field isolate (Salwa strain) is presented here. By comparing the gE nucleotide and amino acid sequences of the Salwa strain with those of the wild strain Jura, ten mutated bases were found in the gE strain of Salwa, six of which alter the amino acid sequence, leading to changes in five amino acids. Both strains caused respiratory disease in experimentally infected calves, but Salwa generated slightly milder signs. Both viruses were excreted in nasal and ocular discharges, and were reactivated by dexamethasone treatment. In conclusion, the rather close similarities observed in the gE gene structure and pathogenicity features of the gE mutant and of the wild strain of BHV-1 confirm the genetic stability of gE. The findings indicate that the Salwa isolate is virulent, but less virulent than wild strains. Our data support the use of gE-negative marker vaccines in eradication programmes.     

Reactivation of Bovid herpesvirus 1 and 2 and Parainfluenza-3 virus in calves latently infected

Two experiments were carried out to determine whether Bovid herpsvirus (BHV) 2 is able to induce a recurrent infection in experimentally infected calves. In the first experiment the stress induced by dexamethasone (DMS) treatment failed to reactivate the clinical condition or to induce shedding of BHV2. However, treatment with DMS reactivated a latent BHV1 infection in all calves previously inoculated with BHV2 and also in two noninoculated controls. Probably, because of the interference by BHV1 the study failed to resolve the question as to whether BHV2 could induce a recurrent infection. Consequently, a second experiment was performed using calves devoid of antibody to BHV1 and, therefore, probably, free of virus. By this study it was demonstrated that BHV2 can remain as a latent infection in cattle, which, when immunosuppressed as with DMS, can be reactivated. A finding of considerable interest in this experiment was that in 1 calf a concurrent piroplasma infection was also, unexpectedly, discovered.Recrudescence of latent BHV1 infection was induced by DMS treatment of calves possessing antibody to the virus. The infection once reactivated, was readly transmitted by contact to three other calves devoid of antibody to BHV1. In the same experiment Parainfluenza-3 (PI-3) virus was unexpectedly isolated from all calves. It was speculated that all calves were latently infected with PI-3 virus with concurrent infection by BHV1 acting as a stress inducing PI-3 reactivation.These studies seem to indicate that mixed infections could have an important role in the mechanism involved in the establishment of latent infections and viral reactivation.     

The serological BHV1 status of dams determines the precolostral status of their calves

Precolostral calves and their dams were serologically investigated for the presence of antibodies against Bovine Herpesvirus 1 in diagnostic tests with a very high sensitivity and specificity. Although the syndesmo-chorial type of placenta of ruminants does not transfer gamma globulins, a large number of calves had antibodies, in most cases in a very low concentration. Significant correlations were found between the serological status of the dam, the status of the calf, and the titre of antibodies. Oral intake of maternal blood by the calf at birth or transmission or leakage of maternal antibodies during pregnancy might be possible causes of precolostrally positive calves. From the results it is concluded that to reduce the risk of obtaining BHV1-positive calves, BHV1-negative dams should be selected for breeding purposes.     

Airborne transmission of BHV1, BRSV, and BVDV among cattle is possible under experimental conditions

To control the diseases caused by bovine herpesvirus 1 (BHV1), bovine respiratory syncytial virus (BRSV), and bovine virus diarrhoea virus (BVDV), it is crucial to know their modes of transmission. The purpose of this study was to determine whether these viruses can be transmitted by air to a substantial extent. Calves were housed in two separate isolation stables in which a unidirectional airflow was maintained through a tube in the wall. In one stable, three of the five calves were experimentally infected with BHV1 and later with BRSV. In the BVDV experiment, two calves persistently infected with BVDV (PI-calves) instead of experimentally infected calves, were used as the source of the virus. In all the calves infections were monitored using virus and antibody detection. Results showed that all the three viruses were transmitted by air. BHV1 spread to sentinel calves in the adjacent stable within three days, and BRSV within nine days, and BVDV spread to sentinel calves probably within one week. Although airborne transmission is possibly not the main route of transmission, these findings will have consequences for disease prevention and regulations in control programmes.     

Sheep do not have a major role in bovine herpesvirus 1 transmission

With regard to BHV1 eradication programs in cattle it is important to know whether sheep can be a reservoir of BHV1. We therefore performed an experiment that consisted of three phases. In phase 1, 10 sheep were inoculated with high doses of BHV1 and kept in close contact with 5 sheep and 5 calves. All inoculated sheep excreted BHV1 between 8 and 15 days post inoculation and seroconverted. Although BHV1 was isolated from the nasal mucosa of 3 out of 5 sentinel sheep, none of the sentinel sheep produced antibodies against BHV1. One sentinel calf excreted BHV1 through days 12–17; the remaining 4 calves excreted BHV1 between days 18 and 24, suggesting that the first calf was infected by sheep and the remaining 4 sentinel calves were infected by that calf and not by sheep. The bacic reproduction ratio (R₀) of BHV1 between sheep and calves was estimated at 0.1, and among calves it was estimated at ≥9. In phase 2, all inoculated sheep were treated with dexamethasone and kept in close contact with 5 sheep and 5 calves. All dexamethasone treated sheep re-excreted BHV1 over a 6- to 9-day period. None of the sentinel animals seroconverted. In phase 3, the sentinel sheep and calves of phase 1 were kept in two groups and were treated with dexamethasone. None of the sentinel sheep re-excreted BHV1, whereas 3 out of 5 sentinel calves did. It is concluded that while BHV1 infection in sheep is possible, BHV1 does not spread from sheep easily to cattle.     

单克隆抗体ELISA检测犊牛粪便中冠状病毒抗原

用两株单克隆抗体混合后包被ＥＬＬＩＳＡ微孔板，加牛冠状病毒抗原，加经白陶土处理过的兔抗牛冠状病毒免血清，再加上辣根氧化物酶标记的羊抗兔ＩｇＧ抗体，加底物质显色间接ＥＬＩＳＡ检测牛冠状病毒抗原获得成功。用此方法检测细胞培养的牛冠状病毒上清液，其敏感度高出血凝试验（ＨＡ）８倍，从武汉市附近３个奶牛场采集犊牛腹泻粪便１０５份，用单抗ＥＬＩＳＡ检测牛冠状病毒抗原，共检出阳性３６份，并与血凝及血凝抑制试验，     

Comparison of the sensitivity of in vitro and in vivo tests for detection of the presence of a bovine viral diarrhoea virus type 1 strain

Veterinary vaccines are usually tested for the absence of contaminants. However, the quality control does not always imply that vaccines are not contaminated as, for example, illustrated by the bovine herpes virus 1 (BHV1) vaccine used in The Netherlands in 1999 that contained a small amount of bovine viral diarrhoea virus (BVDV1). Thousands of cows were vaccinated with BHV1 vaccine batches, and the question arose as to whether these small amounts of BVDV1, most likely not detected with in vitro tests, could have infected cattle. More in general, the question was whether the outcome of the in vitro tests, i.e. the in vitro infectivity, was indicative for the infectivity for cattle, i.e. the in vivo infectivity. We therefore carried out in vitro experiments to determine the sensitivity of a BVDV1 isolation assay. In addition, we performed two animal experiments, in which we estimated the lowest dose needed to infect calves with BVDV1. We extrapolated the experimental in vitro and in vivo results from a tissue culture infectious dose (TCID50) to a cattle infectious dose (CID50). We observed a partial response in the calves inoculated with this dose: four out of six calves turned out to be infected. In the tissue culture test, all 20 samples tested negative. The response in vivo, however, was not significantly higher than the in vitro response, which implies that no difference in susceptibility was observed between the animal test and the tissue culture test. Based on the results in our experiments, some cattle may have been infected with BVDV1 after the application of the contaminated BHV1 vaccine during the vaccination campaign. The question remains that how many cattle received contaminated vaccine, and became infected with BVDV1.     

Airborne transmission of bovine herpesvirus 1 infections in calves under field conditions

A small scale transmission experiment was performed with bovine herpesvirus 1 (BHV1) in a cattle population under field conditions. 10 calves were housed under strict hygienic conditions, with a distance of 4m between each calf. Five calves were experimentally infected with BHV1, two calves with strain Harberink and three with strain Lam, respectively. Experimentally infected calves were placed at 4 m distance from five susceptible sentinel calves. Airborne transmission to sentinel calves was detected using virus isolation and BHV1 specific polymerase chain reactions in samples of nasal fluids, and BHV1 specific antibodies in serum samples. Strain Harberink was hardly transmitted to sentinel calves, whereas strain Lam was transmitted to all sentinels. Estimating the rate of transmission per day, the total number of calves infected by one (strain Lam) infected calf was 1.18. Comparing this estimated transmission ratio between cattle at a distance of 4 m to the estimated transmission ratio R of BHV1 in susceptible commingled cattle reported before, the effect of the factor distance on the transmission ratio could be calculated. Extrapolating these results, a distance of 4.4 m between cattle populations would be necessary to reduce transmission for this strain to R<1.     

Immune production of interferon by cultured peripheral blood mononuclear cells from calves infected with BHV1 and PI3 viruses

Peripheral blood mononuclear cells (PBMC) from calves infected with bovine herpesvirus type 1 (BHV1) or parainfluenza 3 virus (PI3) were cultured in vitro in the presence of inactivated specific antigen presented on MDBK cells. In the presence of inactivated antigen, PBMC from both BHV1-infected and control calves produced interferon (IFN)-alpha in 24 hour cultures. Altering the culture conditions did not result in the detection of immune-specific IFN produced by mononuclear cells from BHV1-infected calves. However, spontaneous IFN was detected in the absence of antigen in 24 hour cultures from infected animals: this IFN was pH 2 labile and completely neutralised by antiserum to recombinant bovine IFN-gamma. Spontaneous IFN-gamma production was only seen in calves following a second BHV1 inoculation, given four to seven weeks after the primary dose. In contrast PBMC cultures from PI3 virus-infected calves did not produce IFN-gamma spontaneously, but did so in cultures which contained inactivated PI3 antigen. Mononuclear cells from control animals failed to produce either IFN-alpha or -gamma when cultured with inactivated PI3 virus. IFN-gamma was detected in PBMC cultures after the primary infection, with no increase in production occurring following subsequent PI3 virus inoculations. Immunospecific production of IFN-gamma provides a simple method for monitoring cell-mediated immunity in BHV1- and PI3 virus-infected calves and can be used for evaluating the efficacy of vaccines against these viruses.     

Protective effects against abortion and fetal infection following exposure to bovine viral diarrhea virus and bovine herpesvirus 1 during pregnancy in beef heifers that received two doses of a multivalent modified-live virus vaccine prior to breeding

Objective-To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection. Design-Randomized controlled clinical trial. Animals-33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves. Procedures-20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days. Results-After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers. Conclusions and Clinical Relevance-Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.