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1.
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.  相似文献   

2.
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.  相似文献   

3.
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.  相似文献   

4.
An experiment was performed to develop a model to study the impact of stress on responsiveness to infection with bovine herpesvirus 1 (BHV1) in veal calves. Social isolation after previous group-housing was used as a putatively stressful treatment. Group-housed specific pathogen-free veal calves (n=8) were experimentally infected with BHV1 at the age of 12 weeks. Half of the calves were socially isolated at the time of infection. Clinical, virological and serological responses to BHV1, and adreno-cortical reactivity to exogenous ACTH were examined. In comparison with group-housed calves, calves socially isolated at the time of infection showed a diminished clinical and fever response, and delayed viral excretion after primary infection with BHV1. Four weeks after social isolation, basal cortisol levels before, and the integrated cortisol response after administration of a low dose of ACTH, were significantly depressed in socially isolated calves. The results suggest that social isolation in veal calves influences the response to an experimental BHV1 infection. A possible mechanism is discussed.  相似文献   

5.
The effect of vaccinating pregnant cows with an inactivated vaccine against Mannheimia haemolytica, BRSV and PI3V infections on selected immune responses in their offspring was examined. Blood samples were collected weekly for 12 weeks from six newborn calves from each of vaccinated (experimental) and unvaccinated (control) dams. Specific antibodies to M. haemolytica, BRSV and PI3V and mean values of IgA, IgG concentrations were significantly higher in the experimental calves compared with the controls. However, specific antibody titres to adenovirus type 3, BHV1 and BVDV in the experimental calves had constant levels while the control group levels changed. The IgM, Hp and SAA concentrations generally increased until week 8 in the experimental group, but the control group titres became higher after week 9. This study demonstrates that specific immunisation of cows pre-partum significantly stimulated parameters associated with immunity and it also controlled the acute phase response intensity in their offspring. Therefore the vaccination of dams may provide additional antibody protection against infection to their offspring.  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
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11.
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.  相似文献   

12.
Serological evidence of exposure of reindeer (Rangifer tarandus) to a virus related to bovine herpesvirus 1 (BHV1) (Synonym: Infectious bovine rhinotracheitis (IBR) virus) has been reported in Canada (El Azhary 1979) and the USA (Dieterich 1981). A serological survey conducted in Finnish Lapland also detected neutralising antibodies to BHV1 in reindeer sera; 23 % of 300 reindeer had detectable antibodies, whereas none of 300 cattle sera from the same region contained antibodies to BHV1 (Ek-Kommonen et al. 1982). There is currently no evidence of BHV1 infection of cattle in Finland, so the isolation and characterisation of the reindeer herpesvirus was of considerable interest. This short communication describes the isolation and preliminary characterisation of a herpesvirus from a reindeer following the administration of dexamethasone.  相似文献   

13.
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.  相似文献   

14.
Five calves were given live intranasal vaccine against bovid herpesvirus 1 (BHV1) two days after intranasal inoculation of bovine pestivirus (BVDV). Another 5 were vaccinated in the absence of BVDV. Control unvaccinated groups were also maintained. All calves were challenged with virulent BHV1. The unvaccinated calves developed signs of infectious bovine rhinotracheitis (IBR) and both vaccinated groups showed a similar degree of clinical protection from IBR. Those given BVDV before vaccination shed up to 140 times more BHV1 (P<0.01) in the nasal mucus following challenge than those which had received BHV1 vaccine alone. The epidemiological significance of this is discussed.  相似文献   

15.
The longstanding assumption that calves of more than 6 months of age are more resistant to Mycobacterium avium subspecies paratuberculosis (MAP) infection has recently been challenged. In order to elucidate this, a challenge experiment was performed to evaluate age- and dose-dependent susceptibility to MAP infection in dairy calves. Fifty-six calves from MAP-negative dams were randomly allocated to 10 MAP challenge groups (5 animals per group) and a negative control group (6 calves). Calves were inoculated orally on 2 consecutive days at 5 ages: 2 weeks and 3, 6, 9 or 12 months. Within each age group 5 calves received either a high – or low – dose of 5 × 109 CFU or 5 × 107 CFU, respectively. All calves were euthanized at 17 months of age. Macroscopic and histological lesions were assessed and bacterial culture was done on numerous tissue samples. Within all 5 age groups, calves were successfully infected with either dose of MAP. Calves inoculated at < 6 months usually had more culture-positive tissue locations and higher histological lesion scores. Furthermore, those infected with a high dose had more severe scores for histologic and macroscopic lesions as well as more culture-positive tissue locations compared to calves infected with a low dose. In conclusion, calves to 1 year of age were susceptible to MAP infection and a high infection dose produced more severe lesions than a low dose.  相似文献   

16.
Cryptosporidiosis is one of the major causes of diarrhea in calves. Cryptosporidium parvum is considered the most important calf diarrhea pathogen in the Cryptosporidium species. Not only could infected calves spread C. parvum, but infected adult cattle could also shed oocysts. The objectives of this study were (1) to investigate the prevalence of C. parvum in dairy herds in Taiwan, including calves, the dams in delivery enclosure, the floor, and the drinking water; (2) to clarify the relationship of diarrhea, management, and C. parvum infection. Twenty dairy herds in Taiwan were selected by random sampling, including 226 calves and 198 dams, and other environmental samples were collected. A questionnaire was filled out by the farm owners to collect information regarding the management of calves and the delivery enclosure. Hierarchical logistic regression was used to analyze the risk factors for C. parvum infection. The prevalence of C. parvum infection in calves was 26.5% (60/226), while in dams, it was 19.7% (39/198). The C. parvum infection in calves increased with environmental contamination of C. parvum and clinical signs of diarrhea, while it decreased with a yard provided in the delivery enclosure. In conclusion, the management of the delivery enclosure appears to be more important for preventing cryptosporidiosis in calves in Taiwan.  相似文献   

17.
Nineteen Holstein-Friesian bull calves were inoculated with 2.4 × 106 sporocysts of Eimeria zuernii by stomach tube. The calves were divided into three groups 10 days after infection. The first group (seven calves) was treated with monensin (1 mg/kg body weight daily) from the 10th–20th day after infection; the second group (six calves) with amprolium (10 mg/kg body weight daily) for the same period of time and the third group (six calves) acted as infected controls. Both drugs were effective in preventing clinical signs, in reducing rates of weight gain and in suppressing oocyst production. The calves were reinfected with E. zuernii 35 days after the initial infection. The calves of all three groups were resistant to the second infection with E. zuernii as measured by rates of weight gain, fecal oocyst output and lack of clinical signs.  相似文献   

18.
Five calves were given live intranasal vaccine against bovid herpesvirus 1 (BHV1) two days after intranasal inoculation of bovine pestivirus (BVDV). Another 5 were vaccinated in the absence of BVDV. Control unvaccinated groups were also maintained. All calves were challenged with virulent BHV1. The unvaccinated calves developed signs of infectious bovine rhinotracheitis (IBR) and both vaccinated groups showed a similar degree of clinical protection from IBR. Those given BVDV before vaccination shed up to 140 times more BHV1 (P less than 0.01) in the nasal mucus following challenge than those which had received BHV1 vaccine alone. The epidemiological significance of this is discussed.  相似文献   

19.
The gene expression of interleukin-2 and interleukin-10 in calves with a primary infection of Fasciola gigantica was studied. Five calves were infected orally with a dose of 1000 viable metacercariae of F. gigantica and five calves served as uninfected control animals. Expression of two cytokine genes i.e. IL-2 and IL-10 (Th1 and Th2) was measured at 10, 30 and 75 days post-infection (PI) by real-time polymerase chain reaction with the double stranded DNA-binding dye SYBR Green. Interleukin-2 was not detected in the peripheral blood mononuclear cells (PBMCs) of infected or control animals at 10, 30 and 75 days PI, however, IL-10 was present in detectable levels in PBMCs of infected animals at 10, 30 and 75 days PI, with no expression of this cytokine in the control animals. With an increased expression of IL-10 and no expression of IL-2 cytokine gene, the present study suggests that F. gigantica infection in calves evoked Th2 immune response.  相似文献   

20.
The physiological and production effects of feeding additional vitamin E and ruminally protected vitamin C were examined in cattle challenged with bovine herpesvirus 1 (BHV 1). Forty-eight individually penned 6-mo-old Angus and Angus crossbred heifer calves with a mean BW of 151 kg were allocated randomly to four diets in a 2 x 2 factorial arrangement of treatments. Pelleted diets provided either 15 or 185 IU/kg of DM of vitamin E, with or without 3.7 g of ruminally protected vitamin C/kg of DM. Blood samples were taken at start of the experiment and at wk 4, 5, and 6. At the start of wk 5, half of each of the dietary groups was challenged with BHV 1. Feeding additional vitamin E was associated with greater (P < 0.001) mean plasma alpha-tocopherol. In contrast, feeding ruminally protected vitamin C was not associated with greater (P = 0.59) mean plasma ascorbate concentration; however, feeding ruminally protected vitamin C was associated with lower (P = 0.03) mean blood total superoxide dismutase (Cu/Zn SOD and Mn SOD) concentration. Calves fed additional vitamin E had greater (P = 0.05) mean plasma beta-carotene concentrations. There were interactions between dietary intake of vitamins E and C with respect to serum ceruloplasmin concentration (P = 0.01) and G:F (P = 0.05). Bovine herpesvirus 1 challenge was associated with lower white cell count (P = 0.007), lymphocyte count (P < 0.001), and DMI (P = 0.03). Feeding additional vitamin E to calves challenged with BHV 1 was associated with a lower (P = 0.03) serum ceruloplasmin concentration. There was a non-significant trend towards an interaction (P = 0.06) between the feeding of vitamins E and C, with virus-challenged calves fed additional vitamin E alone having greater plasma retinol concentrations. The feeding of vitamins E and/or C in calves challenged with BHV 1 was associated with alterations in the concentrations of other antioxidants. More severe disease may have translated these cellular effects to changes in health and performance.  相似文献   

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