The bovine herpesvirus type 1 envelope protein Us9 acidic domain is crucial for anterograde axonal transport

In this study, we examined the functional role of bovine herpesvirus type 1 (BHV-1) Us9 acidic domain residues 83-90 in the anterograde axonal transport of the virus in calves (natural host), rabbits, and in cultured neurons. A mutant virus strain lacking Us9 residues 83-90 (BHV-1 Us9 Δ83-90) and the rescued virus (BHV-1 Us9 R83-90) replicated efficiently in the nasal and ocular epithelium during primary infection and established latency in the trigeminal ganglia (TG). However, upon reactivation from latency, only the BHV-1 Us9 R83-90 virus was detected in nasal and ocular swabs of animals. In compartmentalized, rabbit primary dorsal root ganglia (DRG) neuron cultures, the Us9-deleted BHV-1, BHV-1 Us9 Δ83-90 and BHV-1 Us9 R83-90 viruses were transported efficiently in the retrograde direction. However, only the BHV-1 Us9 R83-90 virus was transported in an anterograde direction. These studies suggested that the Us9 acidic domain residues located between 83 and 90 were required for axonal anterograde transport.     

Early embryonic death in heifers after inoculation with bovine herpesvirus-1 and reactivation of latent virus in reproductive tissues

Thirteen crossbred heifers seronegative for bovine herpesvirus-1 (BHV-1) were bred naturally to a seronegative bull. Eight heifers were inoculated with BHV-1, IV, on postbreeding day (PBD) 7 or 14. Viremia was detected in heifers 1 through 7, and virus also was isolated from nasal and vaginal secretions of heifers 2, 3, 4, 6, and 7. The pregnancy status of all heifers was monitored from PBD 14 to PBD 35 by determining plasma progesterone concentrations at 1- to 3-day intervals. Decreased progesterone values indicated that pregnancy was not maintained in BHV-1-inoculated heifers 2, 3, 4, 6, 7, and 8. The postbreeding interestrual period of these 6 heifers was normal or only slightly longer than would be expected in the absence of conception. All 5 noninoculated heifers were pregnant on PBD 35. Three to 4 months after acute infection, all BHV-1 inoculated heifers were treated with dexamethasone for 5 days and were euthanatized. Nasal and vaginal swab specimens were tested daily during dexamethasone treatment for excreted BHV-1, and reproductive tissues and adrenal glands were collected at necropsy for virologic tests and histopathologic examination. Virus reactivation was demonstrated in heifers 2 through 8. The BHV-1 isolations were made from adrenal glands of heifers 2, 3, 5, 6, 7, and 8, vaginal swab specimens of heifers 2, 3, 4, 6, and 7, and nasal swab specimens of heifers 2, 3, and 6. Only heifer 3 had virus in reproductive tissues; these isolations were made from ovary, infundibulum, and uterine tube, but not from endometrium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of a bovine herpesvirus-1 isolate on reproductive function in heifers: classification as a type-2 (infectious pustular vulvovaginitis) virus by restriction endonuclease analysis of viral DNA

A bovine herpesvirus-1 (BHV-1) isolate (FI) from an aborted fetus was used to infect 9 heifers at various stages of gestation. Two heifers were inoculated IV on postbreeding day (PBD) 1, 7, or 14, and 3 heifers were inoculated in the sixth month of pregnancy. Plasma progesterone assays were used to monitor corpus luteum function in heifers inoculated during early pregnancy. Low progesterone values and infertility were seen in the 2 heifers inoculated on PBD 1. Luteal function remained normal in heifers inoculated on PBD 7 or 14. These 4 heifers inoculated on PBD 7 or 14 carried their fetuses to term, and their calves were free of BHV-1 infection at birth. Three heifers inoculated during the sixth month of pregnancy also carried their fetuses to term. Two calves were born alive, and BHV-1 was not isolated from nasal swab samples of either calf; the third calf was stillborn. Virus was not isolated from the stillborn calf's tissues, but BHV-1 was isolated from the placenta. Lesions were not detected in several tissues examined by light microscopy, and BHV-1 antigen was not detected by immunohistochemical examination of paraffin sections. Restriction endonuclease analysis of viral DNA was used to compare the FI virus to other BHV-1 isolates (Colorado-1, Iowa, and K22). On the basis of restriction endonuclease analysis, the FI isolate should be classified as a type-2 (infectious pustular vulvovaginitis) virus, specifically subtype a.     

Efficacy of bovine herpesvirus-1 inactivated vaccine against abortion and stillbirth in pregnant heifers

OBJECTIVE: To evaluate the efficacy of an inactivated bovine herpesvirus-1 (BHV-1) vaccine to protect against BHV-1 challenge-induced abortion and stillbirth. DESIGN: Prospective study. ANIMALS: 35 beef heifers. PROCEDURES: Before breeding, heifers were vaccinated with a commercially available BHV-1 inactivated vaccine SC or IM. The estrous cycle was then synchronized, and heifers were artificially inseminated 30 to 60 days after vaccination. Heifers (n = 21) were challenge inoculated IV at approximately 180 days of gestation with virulent BHV-1. Fourteen control heifers were not vaccinated. Clinical signs of BHV-1 infection were monitored for 10 days following challenge; serologic status and occurrence of abortion or stillbirth were evaluated until time of calving. RESULTS: 18 of 21 (85.7%) heifers that received vaccine were protected from abortion following challenge, whereas all 14 control heifers aborted. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that an inactivated BHV-1 vaccine can protect against abortion resulting from a substantial challenge infection, with efficacy similar to that of modified-live BHV-1 vaccines.     

Dynamics of bovine herpesvirus type 1 infection in Estonian dairy herds with and without a control programme

Bovine herpesvirus type 1 (BHV-1) is an important bovine pathogen, exacerbating poor health and the productivity of cattle. The aims of this study were to detect the efficacy of vaccination programmes in lowering the seroprevalence of BHV-1 gE within the dairy herd and to follow the dynamics of the infection in non-vaccinated herds with uninfected heifers. A two-year longitudinal study was carried out on seven herds that were vaccinated, and in five herds with uninfected heifers without applying a control programme. After the start of the vaccination programme, calves born remained free from the virus. However, in one herd, 7 per cent (95 per cent CI 2 to 18) of these animals showed antibodies to BHV-1 two years after the first vaccination. A decline in BHV-1 antibody prevalence was found in vaccinating herds. Among the five herds not under the control programme, one experienced active virus spread, although one herd experienced self-clearance of the virus. In the herds with high BHV-1 prevalence, vaccinating all cattle from three months of age twice a year with a commercial inactivated marker vaccine efficiently protected offspring from becoming infected, and lowered the prevalence of BHV-1 within the herd. A small proportion of herds may experience self-clearance of the virus.     

Bovine herpesvirus-1 infection of cattle: kinetics of antibody formation after intranasal exposure and abortion induced by the virus

The kinetics of antibody formation in Holstein heifers after primary and secondary intranasal inoculation of bovine herpesvirus-1 (BHV-1) and after BHV-1-induced abortion was determined. Sera were fractionated by gel filtration and ion-exchange chromatography. The antibody activity within serum immunoglobulin (Ig) isotypes was assessed, using a plaque-reduction neutralization assay. The primary immune response to BHV-1 infection was characterized by the appearance of IgM and IgG antibodies in serum by postinoculation day (PID) 7. Maximal IgG antibody activity occurred at PID 35 in nonpregnant heifers and at PID 14 in pregnant heifers. Thereafter, IgG antibody activity declined slowly in both groups of heifers. Maximal IgM antibody activity occurred at PID 14 in both groups of heifers and declined rapidly thereafter. The IgG antibody activity during primary immune responses was restricted to the IgG1 subclass. Secondary responses were characterized by anamnestic IgG antibody responses. Antibody activity was present within the IgG1 and IgG2 subclasses during secondary immune responses, but the increase in antibody activity during this period was primarily in the IgG2 subclass. Secondary IgM antibody formation was elicited by abortion induced by the intra-amniotic inoculation of BHV-1, but not by reexposure by the intranasal route. Abortion occurred in 1 heifer 28 days after intranasal BHV-1 inoculation. Abortion in this heifer was not associated with a secondary antibody response. The nature of BHV-1 antigenic exposure in the bovine determined the relative distribution of anti-BHV-1 antibody activity in serum IgM, IgG1, and IgG2. The formation of IgM antibody, with the exception of secondary intranasal exposure, indicated recent BHV-1 antigenic exposure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental infection of bulls with a genital isolate of bovine herpesvirus-4 and reactivation of latent virus with dexamethasone

Five 13- to 18-month old Belgian Blue bulls were used in this experiment. Four bulls (Nos. 2, 3, 4 and 5) were inoculated intratesticularly with 10(5) plaque-forming units of bovine herpesvirus-4 (BHV-4) in each testicle (Day 0). The challenge BHV-4 strain was previously isolated from testicle cells of a bull exhibiting orchitis and azoospermia. The fifth bull (No. 1) was used as a control and received the same volume of uninfected cell culture supernatant. For 5 days, beginning on Day 51 post-infection, two bulls (Nos. 4 and 5) and the control bull (No. 1) received 0.1 mg kg-1 of dexamethasone. Unilateral castrations were then performed at regular intervals for viral examination. Treatment with dexamethasone reactivated latent BHV-4, but no clinical signs were observed in treated bulls until the end of the experiment (Day 93). Only Bull 3 showed conjunctivitis and temporary azoospermia. The virus was recovered from various samples showing that: (i) BHV-4 can be present in a latent state in the testicles and mononuclear blood cells; (ii) dexamethasone reactivates the virus; (iii) the virus is excreted by nasal and ocular routes. Each infected bull seroconverted and a booster antibody response appeared after dexamethasone treatment as shown by immunofluorescence. Neutralizing antibodies were detected in each bull by complement-dependent neutralization test with titres higher than those obtained by a classical neutralization test. No booster response of neutralizing antibodies was observed after dexamethasone treatment. The antigenically relevant envelope BHV-4 proteins were identified by Western blotting using sera samples from the animals. DNA restriction endonuclease profiles of viruses reisolated after primary infection and reactivation showed only small differences.     

Granular Vulvovaginitis Syndrome in Nelore pubertal and post pubertal replacement heifers under tropical conditions: role of <Emphasis Type="Italic">Mycoplasma</Emphasis> spp., <Emphasis Type="Italic">Ureaplasma diversum</Emphasis> and BHV-1

In order to determine the role of Mycoplasma spp, Ureaplasma diversum and BHV-1 as causal agents of Granular Vulvovaginitis Syndrome in Nelore heifers raised under tropical conditions and based on the hypothesis that stressful conditions during puberty or breeding season would be a determinant factor for the infection, 340 heifers not vaccinated against BHV-1 were divided in Post-pubertal, in the beginning of the first breeding season, and Pubertal heifers. The vaginal lesion score (VLS) Grade 1 to 4 was giving according to lesion area and severity. Vaginal mucus was used to isolate Mycoplasma spp., Ureaplasma diversum and BHV-1. The predominant VLS was 2. No sample was positive for BHV-1; 48% were positive for Mycoplasma spp., Ureaplasma diversum, or both, with predominance of Ureaplasma diversum. Serum neutralization for BHV-1 showed more positive animals in pubertal group (23%); 3 of the paired sera demonstrated seroconversion. These data indicated that post-pubertal and pubertal Nelore heifers raised under extensive conditions are more susceptible to Mycoplasma spp. and Ureaplasma diversum. The hypothesis that the stress of pubertal period could lead to an acute vaginal infection by HBV-1 was not proofed.     

Evaluation of the efficacy of a modified-live combination vaccine against abortion caused by virulent bovine herpesvirus type 1 in a one-year duration-of-immunity study

This study demonstrated that a multivalent vaccine containing modified-live bovine herpesvirus type 1 (BHV-1) protected pregnant heifers and their fetuses against virulent BHV-1 challenge exposure at 365 days after vaccination. The percentage of abortions or fetal deaths caused by BHV-1 was significantly higher in control heifers (10 of 10 [100.0%]) than BHV-1-vaccinated heifers (three of 19 [15.8%]).     

Comparison of humoral immune responses in dairy heifers vaccinated with 3 different commercial vaccines against bovine viral diarrhea virus and bovine herpesvirus-1

A randomized clinical trial was conducted to compare the humoral immune response to 3 different commercial vaccines in dairy heifers housed in 3 different dairy farms in Quebec. All heifers were seronegative to type 1 bovine viral diarrhea virus (BVDV) (Singer strain), type 2 BVDV (NVSL 125c strain), and bovine herpesvirus-1 (BHV-1) at the beginning of the trial. In addition, control heifers in group 1 remained seronegative to the 2 viruses till the end of the trial. Significant differences in humoral immune responses occurred among the 3 commercial vaccines at 4 weeks and 6 months following vaccination. The vaccine in group 2 elicited higher mean antibody titers and seroconversion rates to both type 1 and type 2 BVDV than that in groups 3 or 4. Vaccines in groups 2 and 3 induced higher mean antibody titers to BHV-1 than did the vaccine in group 4.     

Bovine herpesvirus type 1 (BHV-1) and bovine viral diarrhoea virus (BVDV) infections in dairy herds: self clearance and the detection of seroconversions against a new atypical pestivirus

The epidemiology of bovine herpesvirus type 1 (BHV-1) and bovine viral diarrhoea virus (BVDV) was studied in a population of small dairy herds that had not been vaccinated. Bulk tank milk samples of 186 herds in Thailand were collected four times between 2002 and 2004. Serum samples from individual animals in 11 herds were also taken on three occasions. The prevalence of BHV-1 in the 186 herds was 61% in 2002, decreasing to 48% in 2004 and for BVDV was 91% in 2002, decreasing to 72% in 2004. A BVDV antigen-positive calf was found in one of the 11 herds, and animals in this herd and three other herds seroconverted to a recently described atypical BVDV strain (HoBi). This study showed a significantly decreasing prevalence for both BHV-1 and BVDV due to a self-clearance process. Further studies are needed to find out how the atypical BVDV strain entered the cattle population.     

Meat quality and transport stress of cattle

This study evaluated the effect of transport time up to 14 hours and the effects of vehicle design on animal welfare, stress and meat quality. 18 transports (six short, medium and long) with a total of 486 animals (118 sample animals, heifers and bulls) were carried out on commercial vehicles in summer 2000 and winter 2001. Animal welfare and stress were evaluated by blood serum parameters, heart rate monitoring, behaviour recording and occurrence of carcass bruising. Meat quality was evaluated by post mortem muscle glycogen content, pH value, temperature, drip loss, colour and tenderness measurements. Heifers had lower heart rates than young bulls during loading (95 vs 114 beats per minute, bpm), whereas during transport, both had an average heart rate of 100 bpm, furthermore during unloading, heifers had higher heart rates than bulls (109 vs 100 bpm). Blood sampling during unloading could have marginally increased heart rates during the unloading procedure. Studied cattle had lower heart rates during medium and long distance transports compared with short transports. Monitoring of animal behaviour during transport showed that the former settled down faster than the latter. Single- and two-animal pens in medium and long distance vehicles prevented nervous and stressful movements of cattle, which were more prominent in large pens of short distance lorry. Present results suggest that larger pens of three or four animals could increase cattle stress during transport. Moreover during unloading, cattle loaded in single- or two-animals pens had significantly lower blood cortisol content than those loaded in larger groups of three or four animals (P < 0.01). The amount of severe carcass bruising was highest in animals transported over short times and loaded into groups of four cattle. Severe damages occurred most often on perianal and hipbone area of the carcass surface. Present results showed that muscle glycogen level was highest after long transport. These animals were fed more regularly from the last feeding up to stunning than medium or short distance animals. Animals in single-pens had the highest muscle glycogen level. Transport distance or number of animals in one pen had a minor effect on muscle pH values or temperatures during 24 hours post mortem (pm). Drip loss of the M. longissimus dorsi (LD) was highest after long transport, but animal number in one pen had no effect on drip loss. Colour of the LD muscle was independent on transport conditions. Light colour of three animal groups resulted from high amounts of heifers, which had lighter colour than bulls. All meat samples were quite tender. However, heifers had significantly tender meat than young bulls (P < 0.001). Higher amounts of heifers had the most tender meat after short transports. Mean DFD (dark, firm, dry) meat occurrence was 2.1% in this project, DFD frequency was lowest after short, then after long and highest after medium distance transports. Because of not evenly distributed numbers of bulls (low) and heifers (high) it was difficult to compare short and long distance transport effects.     

Intrapreputial infection of young bulls with bovine herpesvirus type 1.2 (BHV-1.2): acute balanoposthitis, latent infection and detection of viral DNA in regional neural and non-neural tissues 50 days after experimental reactivation

Venereal infection of bulls with bovine herpesvirus type 1.2 (BHV-1.2) may result in acute balanoposthitis followed by the establishment of latent infection, presumably in dorsal root nerve ganglia. We herein report the characterization of the acute and latent infection of young bulls with a Brazilian BHV-1.2 isolate and the investigation of neural and non-neural sites in which viral DNA persists during latent infection, i.e. 110 days after inoculation and 50 days after experimental reactivation. Intrapreputial inoculation of BHV-1.2 isolate SV-56/90 (10(6.5)pfu per animal) resulted in severe balanoposthitis, characterized by redness of the penis and preputial mucosa, coalescent vesicles and fibrinous exsudate in all four infected bulls. Virus shedding was detected in preputial secretions and semen up to days 14 and 13 pi, respectively. Dexamethasone administration at day 60 pi led to reactivation of the infection in all animals, resulting in virus shedding in preputial secretions and/or in semen. At day 50 post-reactivation (pr), the animals were euthanized and regional tissues were collected for PCR and virus isolation. Viral DNA was consistently detected in the dorsal root ganglia of nerves genito-femoral (4/4) and obturator (4/4); frequently in the pudendal (3/4), sciatic (3/4) and rectal caudal nerve ganglia (2/3). In addition, viral DNA was detected in the pelvic sympathetic plexus of one bull and in regional lymph nodes (deep inguinal (2/4); sacral (1/4); medial iliac (1/4)) of two bulls. No infectious virus could be recovered from homogenates of DNA positive tissues, indicating the absence of actively replicating virus. These results demonstrate that BHV-1.2 DNA may persist in several sacral nerve ganglia and in regional lymph nodes as well during latent infection, i.e. 50 days after experimental reactivation. These findings may help in understanding the pathogenesis of acute and latent genital infection by BHV-1.2.     

Association of herd BHV-1 seroprevalence with respiratory disease in youngstock in Estonian dairy cattle

The associations between herd bovine herpesvirus 1 (BHV-1) seroprevalence, along with other infectious and farm management factors with bovine respiratory disease (BRD) in dairy calves and heifers, were investigated. Serum samples from 103 dairy cattle herds were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhea virus (BVDV), and Mycoplasma bovis (M. bovis). A questionnaire was used to record herd management practices. A high occurrence of respiratory disease in unweaned calves was associated with low to moderate and high prevalence of BHV-1 among cows (OR=14.8, p=0.005 and OR=19.2, p=0.002, respectively) and positive BVDV status of a herd (OR=5.1, p=0.02). The presence of BVDV in a herd was related to a high incidence of respiratory disease in heifers 3-16 months old (OR=4.3, p=0.027). Based on the results of multiple correspondence analysis, holding youngstock separately from cows until pregnancy, introducing new animals and the activities of on-farm employees may contribute to a higher incidence of BRD.     

Detection of bovine herpesvirus-1-specific IgM using a capture enzyme immune assay with isotype-specific monoclonal antibodies

The detection of virus-specific immunoglobulin M (IgM) antibodies in acute-phase serum samples offers the possibility of making an accurate and rapid serologic diagnosis. We have developed a solid-phase capture assay that uses murine monoclonal antibodies specific for bovine IgM to separate the whole IgM fraction of a bovine serum sample. The IgM specific for bovine herpesvirus-1 (BHV-1) is then detected by the addition of viral antigen, which in turn is detected by BHV-1-specific monoclonal antibodies conjugated to horseradish peroxidase. A BHV-1 IgM antibody response was detected during the early postinfection period (7-40 days PI). Bovine herpesvirus-1 IgM antibody was not detected in sera taken from 3 animals following dexamethasone-induced viral reactivation. This method compares favorably with viral isolation, antigen detection in the clinical samples, and paired serology in the diagnosis of BHV-1 infection at a herd level.     

Rapid detection of bovine herpesvirus 1 in the semen of infected bulls by a nested polymerase chain reaction assay.

A nested polymerase chain reaction (PCR) assay was developed for the detection of bovine herpesvirus 1 (BHV-1) in bovine semen and compared with the virus isolation method. When extended semen, commonly used in the bovine artificial insemination industry, was inoculated with BHV-1, the PCR assay detected BHV-1 DNA in semen inoculated at 0.25-2.5 TCID50 per 0.5 mL. In contrast, the lower limit of detection for virus isolation was 250 TCID50 of BHV-1 inoculated in 0.5 mL of extended semen. These methods were also used to detect BHV-1 in the semen of four bulls which were experimentally infected with BHV-1. All infected bulls demonstrated balanitis at 3 d post-inoculation (DPI) and severe balanoposthitis at 4 DPI. BHV-1 was detected in raw semen by virus isolation and PCR at 2 DPI, before balanitis was evident. For virus isolation, the last day that BHV-1 was detected during primary infection was 7 DPI for two bulls and 9 and 11 DPI for the other two bulls. In contrast, PCR detected BHV-1 in the bulls' semen until 14 or 18 DPI. For individual animals, PCR detected BHV-1 during primary infection for at least 1-10 d longer than virus isolation. Reactivation of BHV-1 from latency without the presence of visible lesions was promoted twice by two series of 5 d dexamethasone injections. For the first series of dexamethasone treatments, a positive virus isolation result was obtained on the 5th d of treatment for only one bull. In contrast, two bulls demonstrated evidence of viral reactivation on this day by PCR. All bulls shed BHV-1 in semen on d 4 after dexamethasone treatment, as evidenced by positive virus isolation and PCR results. One bull was still PCR positive 13 d later. For the second series of dexamethasone treatments, a small amount of virus was isolated from semen collected on d 3 or 4 after treatment for two bulls but not from the other two bulls. In contrast, semen samples from all bulls were PCR positive for either or both of these 2 d. In total, from 80 semen samples, 45 were PCR positive and 26 were virus isolation positive. Thus, the PCR assay detected BHV-1 shedding in bulls earlier, more often, and for a longer duration, than did the virus isolation method.     

Response of proinflammatory and anti-inflammatory cytokines in calves with subclinical bovine viral diarrhea challenged with bovine herpesvirus-1

The aim of this work was to investigate the susceptibility of calves infected with bovine viral diarrhea virus (BVDV) against secondary infections. For this purpose, the profile of cytokines implicated in the immune response of calves experimentally infected with a non-cytopathic strain of BVDV type-1 and challenged with bovine herpesvirus 1.1 (BHV-1.1) was evaluated in comparison with healthy animals challenged only with BHV-1.1. The immune response was measured by serum concentrations of cytokines (IL-1β, TNFα, IFNγ, IL-12, IL-4 and IL-10), acute phase proteins (haptoglobin, serum amyloid A and fibrinogen) and BVDV and BHV-1.1 specific antibodies. BVDV-infected calves displayed a great secretion of TNFα and reduced production of IL-10 following BHV-1 infection, leading to an exacerbation of the inflammatory response and to the development of more intense clinical symptoms and lesions than those observed in healthy animals BHV-1-inoculated. A Th1 immune response, based on IFNγ production and on the absence of significant changes in IL-4 production, was observed in both groups of BHV-1-infected calves. However, whereas the animals inoculated only with BHV-1 presented an IFNγ response from the start of the study and high expression of IL-12, the BVDV-infected calves showed a delay in the IFNγ production and low levels of IL-12. This alteration in the kinetic and magnitude of these cytokines, involved in cytotoxic mechanisms responsible for limiting the spread of secondary pathogens, facilitated the dissemination of BHV-1.1 in BVDV-infected calves.     

Abortifacient property of bovine herpesvirus type 1 isolates that represent three subtypes determined by restriction endonuclease analysis of viral DNA.

Bovine herpesvirus type 1 (BHV-1) isolates are classified into 3 subtypes by use of restriction endonuclease analysis. Isolates from aborted fetuses have been either subtype 1 or 2a, whereas subtype 2b viruses have not been associated with abortion. We assessed the abortifacient property of isolates representing each of the 3 BHV-1 subtypes by IV inoculation of heifers with the virus 25 to 27 weeks after breeding. Three heifers were given Cooper (subtype 1) isolate, 3 heifers were given FI (subtype 2a) isolate, and 5 heifers were given K22 (subtype 2b) isolate. All heifers developed fever and viremia 2 to 5 days after inoculation. Heifers given Cooper or FI isolate aborted between 17 and 85 days after inoculation. The 5 heifers given K22 isolate delivered full-term calves. Placenta was obtained from 4 of the 5 heifers, and K22 virus was isolated from each placenta. Four calves had BHV-1 neutralizing antibody in precolostral serum, with titer ranging from 1:4 to 1:512.     

Comparative studies of BHV-1 variants by in vivo--in vitro tests.

The new encephalitogenic BHV-1.3 and previously characterized BHV-1 strains were studied with reference to their immunogenic and protective potency and their antigenic relationships using "in vitro" and "in vivo" tests. The "in vitro" results obtained by neutralization kinetics showed that the Los Angeles (LA) strain (BHV-1.1) and a vaginal isolate L-114 strain (BHV-1.2) had antigenic similarities. Conversely, the behavior of the encephalitogenic strain A-663 (BHV-1.3), was significantly distinct. The "in vivo" protection test was carried out in calves using LA and A-663 strains. Post-vaccination antibodies and challenge with A-663 strain showed that the immunogenic behavior and protective capacities of both strains were similar. Neutralization kinetics differences between BHV-1.1 and BHV-1.3 did not alter the "in vivo" protection against BHV-1.3 challenge.     

Safety of a modified-live combination vaccine against respiratory and reproductive diseases in pregnant cows

A combination vaccine (Bovi-Shield FP4 + L5, Pfizer Animal Health) containing modified-live virus (MLV) components against bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus BVDV), parainfluenza virus-3 (PI3), bovine respiratory syncytial virus (BRSV), and inactivated cultures of Leptospira canicola, grippotyphosa, hardjo, icterohaemorrhagiae, and pomona was evaluated for safety in pregnant beef and dairy animals. Heifers vaccinated prebreeding with the minimum immunizing dose (lowest antigen level initiating immunizing effects) of the vaccine's MLV BHV-1 or BVDV components and during pregnancy (approximately 200 days of gestation) with vaccine containing 10x doses of the same BHV-1 and BVDV components delivered live, healthy calves that were determined to be serologically negative (titer less than 1:2) for neutralizing antibodies to BHV-1 and BVDV prior to nursing. Additionally, in three field safety studies, previously vaccinated cows and heifers that received a field dose (vaccine containing antigen levels required for commercial sale of the MLV combination vaccine during either the first, second, or third trimester of pregnancy had abortion rates similar to those of pregnant cows and heifers vaccinated during the same stage of pregnancy with sterile water diluent.