Viral contamination of bovine fetal lung cultures and bovine fetal serum

Commercial bovine fetal serum (BFS) and bovine fetal lung (BFL) cells were tested for viruses. The only virus detected in any samples was noncytopathogenic bovine viral diarrhea virus (BVDV). Of 37 BFL cultures initiated, 34 were negative for BVDV, 1 was positive, and 2 were suspicious in that the source of BVDV contamination was not certain. Of 9 lots of irradiated sera tested, 1 (10%) was positive for BVDV; of 21 lots of nonirradiated sera tested, 13 (62%) were positive for BVDV. As judged by intensity of fluorescence in infected cultures, some cell strains were much more susceptible to BVDV than other strains. Heat inactivation of serum at 56 C for 30 minutes was found to be an unreliable method of eliminating BVDV from sera.     

Prevalence of antibodies to bovine respiratory syncytial virus, bovine viral diarrhea virus, bovine herpesvirus-1, and bovine parainfluenza-3 virus in sheep and goats in Quebec

Serum samples were collected from 1,075 clinically normal sheep and goats from 77 flocks in 7 agricultural regions of Quebec from June to August 1982. Sheep and goats were tested for antibodies to bovine respiratory syncytial virus, bovine viral diarrhea virus, and bovine herpes-virus-1 by the indirect fluorescent antibody technique and for parainfluenza-3 virus by the hemagglutination inhibition test. The prevalence of antibodies in animals to respiratory syncytial virus was 31%; to bovine viral diarrhea virus, 22.2%; to bovine herpesvirus-1, 10.8%; and to parainfluenza-3 virus, 23.2%. Antibodies prevailed in similar proportions in young (less than 1 year) and adult (greater than 1 year) animals.     

Detection and molecular characterisation of bovine polyomavirus in bovine sera in New Zealand

AIM: To investigate the prevalence of bovine polyomavirus (BPyV) DNA in commercial batches of bovine serum products, cell lines and cattle in New Zealand and to characterise the viral DNA detected. METHODS: Two nested polymerase chain reaction (PCR) assays were applied to detect BPyV in bovine sera. One was used to screen for the VP1 gene of BPyV DNA in: 140 batches of commercial bovine serum products, including 66 batches of fetal bovine serum (FBS), 34 batches of calf serum, and 40 batches of adult bovine serum (ABS)/plasma; 112 individual adult bovine sera; and 16 cell lines of various species origin. Fifty batches of serum samples were also tested, using the second nested PCR assay that screened for the Large T gene. Restriction fragment length polymorphism (RFLP) was conducted with 36 PCR products amplified from the VP1 gene of BPyV using EcoRI. Five selected VP1 PCR products were subjected to DNA sequencing and phylogenetic analysis. RESULTS: BPyV DNA was detected in 46 (70%) batches of FBS, 11 (32%) batches of calf sera and two (5%) batches of ABS/plasma, an overall prevalence of 42%. None of 112 adult bovine sera was BPyV-positive. RFLP analysis demonstrated a uniform digestion pattern in the majority (31/36) of amplicons tested, while the remaining PCR amplicons did not show enzyme cleavage. Sequence analysis of the PCR products (a 263 base pair (bp) fragment of the VP1 gene) obtained from five batches of FBS showed 96.2-98.9% homology to that of published sequences of BPyV. CONCLUSION: BPyV is a frequent contaminant of commercial bovine serum in New Zealand. The incidence of BPyV in adult bovine serum products is much lower than in FBS and calf serum. Genomic variations exist among different viruses. The clinical significance of the high prevalence of BPyV DNA in bovine serum products is yet to be determined.     

Prevalence of bovine herpesvirus-1, bovine oral diarrhea, parainfluenza-3, bovine adenoviruses-3 and -7, and goat respiratory syncytial viral antibodies in goats

Sera from healthy goats were collected during October 1979 through October 1980. These sera were tested for bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV), parainfluenza-3 (PI-3) virus, bovine adenoviruses (BAV) -3 and -7, and goat respiratory syncytial virus (GRSV) antibodies by microtitration virus-neutralization test. The number of herds with seropositive goats for each virus were: 5/38 (13.2%) for BHV-1; 9/38 (23.7%) for BVDV; 8/38 (21.1%) for PI-3 virus; 1/38 (2.6%) for BAV-3; 15/38 (39.5%) for BAV-7; and 26/34 (76.5%) for GRSV. Seropositive rates for each virus for the individual goats tested were: 6/502 (1.2%) for BHV-1; 9/498 (1.8%) for BVDV; 49/458 (10.75) for PI-3 virus; 1/487 (0.025) for BAV-3; 40/448 (8.9%) for BAV-7; and 166/332 (50.0%) for GRSV.     

Serological detection of multiple retroviral infections in cattle: bovine leukemia virus, bovine syncytial virus and bovine visna virus

Individual experimental animals used in our studies on bovine leukemia virus (BLV) are routinely screened for the presence of antibodies to the three bovine lymphotropic retroviruses. We utilized these screening methods to examine frozen sera from eight herds for antibodies to BLV, bovine visna virus (BVV) and bovine syncytial virus (BSV). Serum samples from 235 animals in four dairy and four beef herds were analyzed. Detection methods used included indirect fluorescent antibody tests of virus-infected cell cultures (BLV, BSV, BVV) and agar gel immunodiffusion (BLV). Sera from the BLV-infected animals in the dairy herds showed the highest single (50%, 49/97) and multiple (30%, 29/97) infections compared with 5% (7/138) and less than 1% (1/138), respectively in the beef herds. Single BVV infections were not detected in the dairy herds, but 11% (11/97) of the sera contained antibodies to BVV plus BLV or BSV. Five sera from beef cattle had antibodies only to BVV and four were obtained from one herd. Only one beef serum of the 138 tested demonstrated multiple antibodies (BLV, BVV).     

Release of tumor necrosis factor-alpha from bovine alveolar macrophages stimulated with bovine respiratory viruses and bacterial endotoxins

The release of tumor necrosis factor-alpha (TNF-) from cultured bovine alveolar macrophages (BAM) was evaluated following stimulation of BAM with bovine herpesvirus-1 (BHV-1), parainfluenza-3 (PI-3) virus, bovine respiratory syncytial virus (BRSV), Escherichia coli 0111:B4 endotoxin, Pasteurella haemolytica type 1 endotoxin, Pasteurella multocida endotoxin, and virus/endotoxin combinations. A cytotoxic assay system using Georgia bovine kidney cells as targets was used to measure TNF- activity. The cytotoxic activity was neutralized by an anti-human TNF- monoclonal antibody.

Stimulation of BAM with 1 median tissue culture infectious dose (TCID₅₀) of live or ultraviolet (UV)-inactivated PI-3 virus/cell resulted in release of TNF- in significantly (P<0.05) higher amounts than sham-induced BAM. The quantities of TNF- released after live or UV-inactivated BHV-1 or BRSV induction were not significantly higher than sham-induced BAM. E. coli 0111:B4, P. haemolytica type 1 and P. multocida endotoxins stimulated TNF- release in a dose-dependent manner. Sequential exposure of BAM to 1 TCID₅₀ per cell of either live BHV-1, PI-3 virus or BRSV and then 5 μg ml⁻¹ of either E. coli 0111:B4, P. haemolytica type 1 or P. multocida endotoxin caused a significant (P<0.05) reduction in detectable TNF- in seven of nine virus/endotoxin combinations tested, when compared with 5 μg ml⁻¹ of endotoxin alone. Parainfluenza-3 virus/endotoxin combinations stimulated higher TNF- release when compared with other virus/endotoxin combinations. Five out of six test animals had serum-neutralizing antibodies to PI-3 virus, one out of six had serum-neutralizing antibodies to BHV-1, and two out of six had serum-neutralizing antibodies to BRSV, suggesting a possible relationship between serum neutralizing antibodies and TNF- release from in vitro cultivated BAM.     

A study of bovine and equine immunoglobulin levels in pony foals fed bovine colostrum

As part of a project to raise specific pathogen free (SPF) Welsh Mountain Pony foals, free from exposure to Equid herpesvirus type 1, foals were removed from their dams at birth and fed bovine colostrum. This study characterises the uptake of bovine colostral immunoglobulin and production of endogenous immunoglobulin, in 10 SPF foals. An enzyme-linked immunoadsorbent assay was developed to measure serum concentrations of bovine IgG1 (boIgG1) to assess the efficiency of transfer, and rate of elimination of boIgG1 by the foal. The endogenous production of equine IgG was studied using a single radial immunodiffusion test. Foals were given 1.2 to 2 litres of bovine colostrum achieving peak serum boIgG1 concentrations of 18.9 to 34.2 g/litre (mean 28.0). The mean half-life of boIgG1 in the foals was 7.4 days. Endogenous immunoglobulin production resulted in equine IgG concentrations greater than 2 g/litre in six of 10 foals by 14 to 19 days of age, and greater than 7 g/litre in eight of 10 foals by 37 to 50 days of age. All foals had equine IgG serum concentrations greater than 10 g/litre by 102 to 135 days of age.     

Prevalence of bovine herpesvirus-1, bovine viral diarrhea, parainfluenza-3, goat respiratory syncytial, bovine leukemia, and bluetongue viral antibodies in sheep

Sera from healthy sheep were collected in January and March 1982 from flocks of sheep located in southwestern and southeastern Louisiana. These sera were tested for bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV), parainfluenza-3 (PI-3) virus, and goat respiratory syncytial virus (GRSV) antibodies by microtitration virus-neutralization test. The sera were tested also for bovine leukemia virus (BLV) and bluetongue virus (BTV) antibodies by immunodiffusion tests. The number of flocks with seropositive sheep for each virus were: 2/8 (25%) for BVDV; 8/8 (100%) for PI-3 virus; 7/8 (87.5%) for GRSV; and 6/8 (75%) for BTV. Seropositive rates for each virus for the individual sheep tested were: 4/158 (2.5%) for BVDV; 117/158 (74.1%) for PI-3 virus; 77/158 (48.7%) for GRSV; and 21/158 (13.3%) for BTV. All sheep were seronegative for BHV-1 and BLV.     

Comparison of levels and duration of detection of antibodies to bovine viral diarrhea virus 1, bovine viral diarrhea virus 2, bovine respiratory syncytial virus,bovine herpesvirus 1, and bovine parainfluenza virus 3 in calves fed maternal colostrum or a colostrum-replacement product

Colostrum-replacement products are an alternative to provide passive immunity to neonatal calves; however, their ability to provide adequate levels of antibodies recognizing respiratory viruses has not been described. The objective of this study was to compare the serum levels of IgG at 2 d of age and the duration of detection of antibodies to bovine viral diarrhea virus 1 (BVDV-1), bovine viral diarrhea virus 2 (BVDV-2), bovine respiratory syncytial virus (BRSV), bovine herpesvirus 1 (BHV-1), and bovine parainfluenza virus 3 (BPIV-3) in calves fed maternal colostrum (MC) or a colostrum replacement (CR) at birth. Forty newborn male Holstein calves were assigned to the CR or the MC group. Group CR (n = 20) received 2 packets of colostrum replacement (100 g of IgG per 470-g packet), while group MC (n = 20) received 3.8 L of maternal colostrum. Blood samples for detection of IgG and virus antibodies were collected from each calf at birth, at 2 and 7 d, and monthly until the calves became seronegative. Calves in the MC group had greater IgG concentrations at 2 d of age. The apparent efficiency of absorption of IgG was greater in the MC group than in the CR group, although the difference was not significant. Calves in the CR group had greater concentrations of BVDV neutralizing antibodies during the first 4 mo of life. The levels of antibodies to BRSV, BHV-1, and BPIV-3 were similar in the 2 groups. The mean time to seronegativity was similar for each virus in the 2 groups; however, greater variation was observed in the antibody levels and in the duration of detection of immunity in the MC group than in the CR group. Thus, the CR product provided calves with more uniform levels and duration of antibodies to common bovine respiratory viruses.     

The immunogenicity and efficacy of replication-defective and replication-competent bovine adenovirus-3 expressing bovine herpesvirus-1 glycoprotein gD in cattle

Replication-competent and replication-defective bovine adenovirus type 3 recombinants expressing the bovine herpesvirus type 1 (BHV-1) glycoprotein D (gD) were tested for induction of gD specific immune responses in calves using intratracheal (1st and 2nd immunization) and sub-cutaneous (3rd immunization) route of immunization. The replication-defective recombinant BAV501 induced systemic immune responses against gD as low titers of anti gD-IgG were detected in the serum. However, the efficacy of the replication-competent BAV3.E3gD to induce gD-specific antibodies in the serum and the nasal secretions was superior to that of replication-defective BAV501 when both viruses were given at the same dosage. Partial protection from challenge was induced in calves immunized with replication-competent BAV3.E3gD. A dramatic increase in the titers of anti-gD IgG and IgA levels, both in serum and nasal secretions, following BHV-1 challenge (anamnestic response) suggested that the animals immunized with replication-defective BAV501 had been primed for gD-specific antibody responses.     

Synergistic effects of bovine respiratory syncytial virus and non-cytopathic bovine viral diarrhea virus infection on selected bovine alveolar macrophage functions.

The effect of bovine respiratory syncytial virus (BRSV) and non-cytopathic bovine viral diarrhea virus (ncpBVDV) infection on selected bovine alveolar macrophage (AM) functions was investigated. Alveolar macrophages were harvested from 2- to 6-month-old calves seronegative for BRSV and BVDV and inoculated with approximately 1 median cell culture infective dose of virus per AM. Control, BRSV infected, ncpBVDV-infected and BRSV-ncpBVDV coinfected AM cultures were evaluated for Fc receptor expression, phagosome-lysosome fusion, superoxide anion (O2-) production, and chemotactic activity on Days 1, 3, 5, and 7 post-infection. Both single and combined viral infections significantly depressed AM Fc receptor expression, phagosome-lysosome fusion, and secretion of chemotactic factors with a more significant synergistic depression seen in BRSV-ncpBVDV coinfection. Production of O2- by AM was not decreased by either BRSV or ncpBVDV infection, but was significantly decreased by coinfection with BRSV-ncpBVDV. The present study confirms previous reports of BRSV effects on AM functions and indicate that ncpBVDV affects AM functions in vitro. Coinfection with BRSV-ncpBVDV produced a synergistic depression on AM functions.     

Standardization and kinetics of in vitro bovine blood lymphocyte stimulation with bovine rotavirus

Two groups of 3-month old calves were immunized intramuscularly with attenuated bovine rotavirus and boosted 21 and 42 days later. The first group of three calves were vaccinated with live virus emulsified with incomplete Freund's adjuvant (IFA) and the second group was immunized with live virus suspended in phosphate buffered saline (PBS). Three other calves, serving as controls, were inoculated with PBS emulsified with IFA. The specific cell-mediated and antibody responses of the animals were studied. Preliminary analysis of in vitro peripheral blood lymphocyte transformation to bovine rotavirus determined optimal conditions as: 96 h culture period, 5 X 10(5) cells per culture in RPMI 1640 medium containing 10% heat-inactivated bovine fetal serum and the use of inactivated virus in the cell culture at a concentration of 5 X 10(6) median tissue culture infective dose before inactivation. Specific blastic stimulation was observed on calves immunized with the rotavirus emulsified with IFA after the second and third vaccine inoculation with stimulation index values varying from 2.00 to 5.73. Serum neutralizing antibody titers of 1/25,600 were also induced in the same calves. Calves immunized with rotavirus-PBS suspension developed a mean antibody titer of 1/1,600, but showed no specific lymphocyte stimulation. No increase in specific immune responses was detected in the control animals.     

In vitro interactions of cytokines and bovine viral diarrhea virus in phytohemagglutinin-stimulated bovine mononuclear cells

Bovine viral diarrhea (BVD) virus inhibited phytohemagglutinin (PHA)-stimulated bovine peripheral blood mononuclear cell (PBMC) proliferation and bovine interleukin-2 (IL-2) production. In the controls, the heat-inactivated BVD virus was not capable of suppressing the PHA-stimulated PBMC proliferation. Presence of exogenous cytokines, such as purified human IL-2, recombinant bovine interleukin-1 (rbovIL-1), recombinant bovine IL-2, and recombinant human IL-6 failed to reverse the BVD virus-induced immunosuppression. Also, we found that the BVD virus inhibited PHA and IL-2 induced proliferation of bovine PBMC in the early and late stages of activation. In summary, our data suggest that BVD virus induced immunosuppression was not due to destruction of the PBMC but may be inhibiting one or more of the important intracellular enzymes that may regulate PBMC proliferation.     

Analysis of bovine trigeminal ganglia following infection with bovine herpesvirus 1

Following primary infection of the eye, oral cavity, and/or nasal cavity, bovine herpesvirus 1 (BHV-1) establishes latency in trigeminal ganglionic (TG) neurons. Virus reactivation and spread to other susceptible animals occur after natural or corticosteroid-induced stress. Infection of calves with BHV-1 leads to infiltration of lymphocytes in TG and expression of IFN-gamma (interferon-gamma), even in latently infected calves. During latency, virus antigen and nucleic acid positive non-neural cells were occasionally detected in TG suggesting there is a low level of spontaneous reactivation. Since we could not detect virus in ocular or nasal swabs, these rare cells do not support high levels of productive infection and virus release or they do not support virus production at all. Dexamethasone (DEX) was used to initiate reactivation in latently infected calves. Foci of mononuclear or satellite cells undergoing apoptosis were detected 6h after DEX treatment, as judged by the appearance of TUNEL+ cells (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling). BHV-1 antigen expression was initially detected in lymphocytes and other non-neural cells in latently infected calves following DEX treatment. At 24h after DEX treatment, viral antigen expression and nucleic acid were readily detected in neurons. Our data suggest that persistent lymphocyte infiltration and cytokine expression occur during latency because a low number of cells in TG express BHV-1 proteins. Induction of apoptosis and changes in cytokine expression following DEX treatment correlates with reactivation from latency. We hypothesize that inflammatory infiltration of lymphoid cells in TG plays a role in regulating latency.     

Increased bovine Tim-3 and its ligand expressions during bovine leukemia virus infection

ABSTRACT: The immunoinhibitory receptor T cell immunoglobulin domain and mucin domain-3 (Tim-3) and its ligand, galectin-9 (Gal-9), are involved in the immune evasion mechanisms for several pathogens causing chronic infections. However, there is no report concerning the role of Tim-3 in diseases of domestic animals. In this study, cDNA encoding for bovine Tim-3 and Gal-9 were cloned and sequenced, and their expression and role in immune reactivation were analyzed in bovine leukemia virus (BLV)-infected cattle. Predicted amino acid sequences of Tim-3 and Gal-9 shared high homologies with human and mouse homologues. Functional domains, including tyrosine kinase phosphorylation motif in the intracellular domain of Tim-3 were highly conserved among cattle and other species. Quantitative real-time PCR analysis showed that bovine Tim-3 mRNA is mainly expressed in T cells such as CD4+ and CD8+ cells, while Gal-9 mRNA is mainly expressed in monocyte and T cells. Tim-3 mRNA expression in CD4+ and CD8+ cells was upregulated during disease progression of BLV infection. Interestingly, expression levels for Tim-3 and Gal-9 correlated positively with viral load in infected cattle. Furthermore, Tim-3 expression level closely correlated with up-regulation of IL-10 in infected cattle. The expression of IFN-γ and IL-2 mRNA was upregulated when PBMC from BLV-infected cattle were cultured with Cos-7 cells expressing Tim-3 to inhibit the Tim-3/Gal-9 pathway. Moreover, combined blockade of the Tim-3/Gal-9 and PD-1/PD-L1 pathways significantly promoted IFN-γ mRNA expression compared with blockade of the PD-1/PD-L1 pathway alone. These results suggest that Tim-3 is involved in the suppression of T cell function during BLV infection.     

Encephalitis induced by bovine herpesvirus 5 and protection by prior vaccination or infection with bovine herpesvirus 1.

Calves were intranasally challenged with bovine herpesvirus 5 (BHV5) and followed for the development of viral infection, clinical encephalitis, histologic lesions in the brain, and viral sequences in the trigeminal ganglia. Calves that were previously vaccinated with bovine herepesvirus 1 (BHV1, n = 4) or previously infected with BHV1 (n = 5) or that had not been exposed to either virus (n = 4) were compared. No calf developed signs of encephalitis, although all calves developed an infection as indicated by nasal secretion of BHV5 and seroconversion to the virus. Histologic lesions of encephalitis consisting of multifocal gliosis and perivascular cuffs of lymphocytes were observed in calves not previously exposed to BHV1. BHV5 sequences were amplified from the trigeminal ganglia of calves previously vaccinated and from calves not previously exposed to BHV1; calves sequentially challenged with BHV1 and later BHV5 had exclusively BHV1 sequences in their trigeminal ganglia. Administration of dexamethasone 28 days after BHV5 challenge did not influence clinical disease or histologic lesions in either previously unexposed calves (n = 2) or previously immunized calves (n = 2), although it did cause recrudescence of BHV5, as detected by nasal virus secretion.     

Development of a polymerase chain reaction and restriction typing assay for the diagnosis of bovine herpesvirus 1, bovine herpesvirus 2, and bovine herpesvirus 4 infections.

A multiplex polymerase chain reaction (PCR) method coupled with a restriction analysis of PCR products (PCR with restriction fragment length polymorphism) was developed for the simultaneous detection of bovine herpesvirus 1, bovine herpesvirus 2, and bovine herpesvirus 4 infections. The specificity, sensitivity, and practical diagnostic applicability of this method were evaluated. This assay may be also adapted to the diagnosis of suid herpesvirus 1 and equine herpesviruses 1 and 3 and could become a powerful diagnostic tool.     

Species preference of bovine thymocytes and fibroblasts for bovine interleukin 1

The purpose of this study was to determine whether bovine thymocytes and fibroblasts preferentially respond to bovine IL-1 as compared with human and murine interleukin 1 (IL-1). We compared equivalents units of recombinant murine and human IL-1 alpha, and purified monocyte-derived bovine IL-1, as measured in the murine thymocyte IL-1 assay, for their ability to stimulate the proliferation of bovine thymocytes and fibroblasts. Fetal and adult bovine thymocytes responded to bovine IL-1, but in contrast, did not respond to recombinant human or murine IL-1 alpha at the concentrations tested. Both adult and neonatal murine thymocytes responded similarly to the three IL-1 preparations. Thus, we concluded that the preferential response of bovine thymocytes for bovine IL-1 was not dependent upon the age of the thymus donor. Bovine fibroblasts also preferentially responded to bovine IL-1; fibroblast proliferation was stimulated by bovine but not human or murine IL-1. Our findings, therefore, imply that although IL-1 is highly conserved among mammalian species, its ability to stimulate the proliferation of thymocytes and fibroblasts may vary from species to species.     

Aspects of bovine herpesvirus 1 and bovine viral diarrhoea virus herd-level seroprevalence and vaccination in dairy and beef herds in Northern Ireland

Background

Infections with bovine herpesvirus 1 (BoHV-1) and bovine viral diarrhoea (BVD) virus cause diseases of cattle with a worldwide distribution. The primary objective of the present study was to describe aspects of herd-level BoHV-1 and BVDV seroprevalence (based on testing of pooled sera) and control on farms in Northern Ireland, including vaccine usage.An indirect antibody ELISA test (SVANOVA, Biotech AB, Uppsala, Sweden) was applied to serum pools which were constructed from serum samples taken for a cross-sectional study of a convenience sample of 500 Northern Irish dairy and beef cow herds in 2010, for which vaccination status was determined by telephone survey. The herd-level seroprevalence of BoHV-1 and BVDV in Northern Ireland was estimated in non-vaccinating herds and associations between possible risk factors (herd type and herd size (quartiles)) and herd-level prevalence were determined using chi-squared analysis.

Results

The herd-level seroprevalence (of BoHV-1 and BVDV) in non-vaccinating herds was 77.3% (95% CI: 73.6–80.9%) and 98.4% (95% CI: 97.3–99.5%) respectively in the cross-sectional study. A significant difference existed in BoHV-1 herd-level seroprevalence between dairy and beef herds (74.7% vs 86.5% respectively; p < 0.02) though not for BVDV seroprevalence (98.5% vs 98.3% respectively; p > 0.91). A significant association was found between herd size (quartiles) and herd-level classification for BoHV-1 herd-level seroprevalence based on cut-off percentage positivity (COPP) (p < 0.01) while no such association was found for BVDV (p = 0.22).15.5% and 23.8% of farmers used BoHV-1 and BVDV vaccines, respectively. BoHV-1 vaccine was used in 30% of dairy herds and in 11% of beef herds, while BVDV vaccine was used in 46% and 16% of dairy and beef herds, respectively.

Conclusions

The results from this study indicate that the true herd-level seroprevalences to bovine herpesvirus 1 and bovine virus diarrhoea virus in non-vaccinating herds in Northern Northern Ireland are 77.3% (95% CI: 73.6–80.9%) and 98.4% (95% CI: 97.3–99.5%), respectively. The present study will assist in guiding regional policy development and establish a baseline against which the progress of current and future control and eradication programmes can be measured.     

Chemotherapy and immunotherapy of bovine leukosis

To prevent the progression of the disease, we treated leukemic or preleukemic cows with (1) adriamycin (ADM) entrapped in liposomes conjugated with monoclonal antibody, c143, against tumor-associated antigens (TAA) of bovine leukemic cells and (2) an immunotherapy using an immunopotentiator consisting of the cell wall skeleton of Nocardia rubra (N-CWS). Five leukemic or preleukemic cows with TAA-positive peripheral blood lymphocytes (PBL) received four injections of ADM alone (0.4 mg/kg body weight) or c143-conjugated liposomes containing the same dose of ADM (L-ADM-c143) through the jugular vein at about 4-day intervals. In three animals treated with L-ADM-c143, the TAA-positive cells gradually decreased with treatment and finally two animals became TAA-negative during a 6-week period and a 14-week period after treatment, respectively. About 6 weeks later, however, TAA-positive cells gradually increased. In the control, two animals treated with ADM alone showed no decrease of TAA-positive cells. Five TAA-positive animals with enlarged subcutaneous lymphatic nodules, each nodule estimated to be from 1 to 4 cm3 in size, were treated by injection of N-CWS into the tumors. Complete regression of tumor was observed in seven out of ten tumors treated in five animals. Decrease of TAA-positive cells was also observed in PBL for all five treated animals. In one animal, the TAA-positive cells remained low for at least 280 days after treatment. This study documents that ADM treatment and intralesionally administered N-CWS are effective in the treatment of bovine leukosis.