Efficacy of a modified live intranasal bovine respiratory syncytial virus vaccine in 3-week-old calves experimentally challenged with BRSV

Two experimental bovine respiratory syncytial virus (BRSV) challenge studies were undertaken to evaluate the efficacy of a single intranasal dose of a bivalent modified live vaccine containing BRSV in 3-week-old calves. In the first study, vaccine efficacy was evaluated in colostrum deprived (maternal antibody negative) calves 5, 10 and 21 days after vaccination. Nasal shedding of BRSV was significantly reduced in vaccinated calves challenged 10 or 21 days after vaccination. Virus excretion titres were also reduced in vaccinates challenged 5 days after vaccination but reduction in duration of shedding and total amount of virus shed were not statistically significant. Clinical disease after challenge in this study was mild. In the second study, vaccine efficacy was assessed in calves with maternal antibodies against BRSV by challenge 66 days post-vaccination. Vaccination significantly reduced nasal shedding after challenge and the severity of clinical disease was also reduced.     

The effect of an outbreak of respiratory disease on herd-level milk production of Norwegian dairy farms

This study was done to evaluate the effect of an outbreak of acute respiratory disease associated with bovine respiratory syncytial virus (BRSV) on the daily milk yield per cow in Norwegian dairy-cattle farms. Retrospective data from 184 dairy herds located in two neighbouring veterinary districts during the study period (December 1994–May 1995, during which an epidemic of acute respiratory disease associated with BRSV occurred in this area) were analysed. Data on the bulk-milk deliveries and the date of the outbreak were collected at herd level, whereas information on calving dates and parity was collected at cow-level. The effect of the herd outbreaks on the daily milk yield was analysed with a repeated-measurement approach. The average daily milk loss was estimated to be 0.70 kg per cow for 7 days after a herd outbreak (compared with the period >1 week prior to an outbreak), adjusted for the herd-level lactation stage, parity and their interaction term. We consider the estimated milk loss associated with a herd outbreak of epidemic respiratory disease to be of minor importance.     

Acute phase proteins in naturally occurring respiratory disease of feedlot cattle

The aim of this study was to evaluate three acute phase proteins (APP) [haptoglobin (HPT), lipopolysaccharide binding protein (LBP) and transferrin (Tf)] in feedlot cattle with naturally occurring respiratory disease diagnosed by a calf health scoring chart (CHSC). Seventy-seven beef calves were observed for signs of Bovine Respiratory Disease (BRD) during the first 28 days after arrival at the feedlot. Fourteen cases and pen matched controls were selected based on the CHSC. BRD cases were defined as a score of ≥5, while controls were defined as a score ≤4. The mean CHSC score in cases was 6.9 which was significantly greater than the controls 2.8 (P < 0.01). Mean plasma LBP and HPT concentrations were significantly greater in cases than controls (P < 0.01). Our study results show that measurement of HPT and LBP could be useful in detecting respiratory disease in feedlot conditions. Transferrin concentrations between the two groups were not statistically different.     

Bovine respiratory syncytial virus (BRSV) pneumonia in beef calf herds despite vaccination.

The present report describes the clinical, pathological, serological and virological findings in calves from 2 larger Danish beef herds experiencing outbreaks of pneumonia. The calves had been vaccinated with an inactivated bovine respiratory syncytial virus (BRSV) vaccine 2 months prior to the outbreak. The clinical signs comprised nasal discharge, pyrexia, cough and increased respiratory rates. A total of 28 calves died in the 2 herds. The laboratory investigations revealed that BRSV was involved and probably initiated both outbreaks. Furthermore, the serological results suggested that the vaccine induced only sparse levels of antibodies probably due to the presence of maternally derived antibodies at the time of vaccination. Necropsy findings in 5 calves revealed changes typical for infectious pneumonia with involvement of BRSV. In conclusion, vaccination of calves against BRSV in 2 Danish beef herds failed to protect the calves against severe or even fatal BRSV mediated respiratory disease 2 months later.     

Bovine respiratory disease: efficacy of different prophylactic treatments in veal calves and antimicrobial resistance of isolated Pasteurellaceae

The present study was conducted to evaluate the efficacy of two prophylactic antibiotic treatments against bovine respiratory disease (BRD) in veal calves. In addition, the antibiotic susceptibilities of isolated Pasteurellaceae were tested. The calves were treated either on the day of arrival by a single administration of tulathromycin (group A, n = 20), by a peroral administration of chlortetracycline, sulphadimidine, and tylosin (group B, n = 20) for seven consecutive days, or were not prophylactically treated (group C, n = 19). On the first day of clinically diagnosed BRD, transtracheal lavage samples were obtained prior to therapeutic treatment and were subsequently cultured. Pasteurellaceae isolates were tested for their susceptibility to 12 antimicrobial agents by the determination of the minimal inhibitory concentrations. During the first 56 d after arrival, different calves in group A and B suffered from one episode of clinically diagnosed BRD while calves of group C experienced two episodes. The average daily weight gain during the same period was significantly lower in group C (0.89 ± 0.04 kg/d) than in the two prophylactically treated groups (1.14 ± 0.05 and 1.15 ± 0.04 kg/d for group A and B, respectively). The improved performance of groups A and B in comparison to group C could be related to a lower incidence of respiratory disorders during the first days after arrival in the prophylactically treated animals. No differences in the clinical efficacy were seen between the two tested prophylactic treatments. The most prevalent bacterial pathogens isolated (n = 79) were Pasteurella multocida (23% of isolated pathogens), Mycoplasma bovis (18%), and Mannheimia varigena (16%). For the isolated Pasteurellaceae, a high resistance pattern was observed to tylosin (83% of the tested P. multocida and 88% of the Mannheimia spp. isolates resistant) and tilmicosin (56% of the tested P. multocida isolates non-sensitive).     

套式RT-PCR检测牛呼吸道合胞体病毒的研究

为了检测牛呼吸道合胞体病毒(BRSV),根据已发表的融合蛋白(F)基因序列,设计了套式RT-PCR引物,初步建立了BRSV的套式RT-PCR检测方法。对138份牛鼻腔棉拭子进行了检测,结果检测到了BRSV阳性样品54份,总的阳性检出率为39.1%。对大部分BRSV阳性样品的F基因扩增产物进行了序列测定与分析。用该套式RT-PCR对牛传染性鼻气管炎病毒、牛副流感病毒3型、牛病毒性腹泻病毒等进行了检测,结果无交叉反应,表明该检测方法具有良好的特异性。本研究首次用套式RT-PCR技术证实了我国部分省的牛群中存在BRSV感染。     

Role of Bibersteinia trehalosi, respiratory syncytial virus,and parainfluenza-3 virus in bighorn sheep pneumonia

Pneumonic bighorn sheep (BHS) have been found to be culture- and/or sero-positive for Bibersteinia trehalosi, respiratory syncytial virus (RSV), and parainfluenza-3 virus (PI-3). The objective of this study was to determine whether these pathogens can cause fatal pneumonia in BHS. In the first study, two groups of four BHS each were intra-tracheally administered with leukotoxin-positive (Group I) or leukotoxin-negative (Group II) B. trehalosi. All four animals in Group I developed severe pneumonia, and two of them died within 3 days. The other two animals showed severe pneumonic lesions on euthanasia and necropsy. Animals in Group II neither died nor showed gross pneumonic lesions on necropsy, suggesting that leukotoxin-positive, but not leukotoxin-negative, B. trehalosi can cause fatal pneumonia in BHS.     

Sequence and unique phylogeny of G genes of bovine respiratory syncytial viruses circulating in Japan

Bovine respiratory syncytial virus (BRSV) is an etiologic agent of bovine respiratory disease. The rapid evolutionary rate of BRSV contributes to genetic and antigenic heterogeneity of field strains and causes occasional vaccine failure. We conducted molecular epidemiologic characterization of BRSV circulating in Japan to obtain genetic information for vaccine-based disease control. Phylogenetic analysis of G and F gene sequences revealed that all of the isolated Japanese BRSV strains clustered in the same genetic subgroup, which was distinct from the 9 known groups. We assigned the Japanese group to subgenotype X. The Japanese isolates formed 2 temporal clusters: isolates from 2003 to 2005 clustered in lineage A; isolates from 2017 to 2019 formed lineage B. The alignment of the deduced amino acid sequences of the G gene revealed that the central hydrophobic region responsible for viral antigenicity is conserved in all of the isolates; unique amino acid mutations were found mainly in mucin-like regions. Our results suggest that BRSV has evolved uniquely in Japan to form the new subgenotype X; the antigenic homogeneity of the viruses within this group is inferred.     

The use of infrared thermography as an early indicator of bovine respiratory disease complex in calves

Bovine respiratory disease (BRD) complex causes considerable distress to domestic livestock and economic hardship to the beef industry. Furthermore, the resulting extensive use of antimicrobial treatments is a growing concern from the perspective of facilitating antibiotic resistant microbes. The earlier detection of BRD would enable an earlier, more targeted treatment regime and earlier isolation of infected individuals. The objective of the present study was to investigate the use of non-invasive infrared thermography in the early detection of BRD in cattle. Studies were conducted on 133 head of weaned calves. Data demonstrated that infrared thermography was able to identify animals at early stages of illness, often several days to over one week before clinical signs were manifest. Data indicated that 4-6 days prior to the onset of clinical symptoms of BRD, greater positive and negative predictive values and test efficiency for infrared thermography (80%, 65% and 71%, respectively) compared to the industry standard practice of clinical scoring (70%, 45% and 55%, respectively).     

An experimental infection model for reproduction of calf pneumonia with bovine respiratory syncytial virus (BRSV) based on one combined exposure of calves

Bovine respiratory syncytial virus (BRSV) has been recognised as an important pathogen in calf pneumonia for 30 years, but surprisingly few effective infection models for studies of the immune response and the pathogenesis in the natural host have been established. We present a reproducible experimental infection model for BRSV in 2-5-month-old, conventionally reared Jersey calves. Thirty-four colostrum-fed calves were inoculated once by aerosol and intratracheal injection with BRSV. Respiratory disease was recorded in 91% of the BRSV-inoculated calves, 72% had an accompanying rise in rectal temperature and 83% exhibited >5% consolidation of the lung tissue. The disease closely resembled natural outbreaks of BRSV-related pneumonia, and detection of BRSV in nasal secretions and lung tissues confirmed the primary role of BRSV. Nine mock-inoculated control calves failed to develop respiratory disease. This model is a valuable tool for the study of the pathogenesis of BRSV and for vaccine efficacy studies.     

Acute phase response in porcine reproductive and respiratory syndrome virus infection

This study was focused on the changes observed in the serum concentration of haptoglobin (Hp), C-reactive protein (CRP), serum amyloid A (SAA) and Pig-major acute protein (Pig-MAP), during experimental porcine reproductive and respiratory syndrome virus (PRRSV) infection and in their relationship with the expression of interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α). Hp and Pig-MAP serum levels were increased at 10 dpi, but CRP and SAA showed a delayed and highly variable increase. All three proinflammatory cytokines were poorly expressed, and only a mild increase in IL-1β was observed at 7 dpi. The increased expression of Hp coincided with the light enhancement observed in both IL-6 and TNF-α, and might be related with an increased expression of IL-10. The low expression of TNF-α might point to a possible mechanism of viral evasion of host-immune response. This issue and the delayed expression of CRP and SAA should be taken into account in future studies about modulation of the immune response by PRRSV infection.     

Seroprevalence to bovine virus diarrhoea virus and other viruses of the bovine respiratory complex in Venezuela (Apure State)

Six hundred and fifteen serum samples obtained from cows in five districts of Apure State, Venezuela, were tested by ELISA for antibodies to bovine virus diarrhoea virus (BVDV). The same samples were also ELISA-tested for antibodies to bovine herpesvirus type 1 (BHV-1) and bovine respiratory syncytial virus (BRSV). Additionally, the haemagglutination-inhibition (HI) test was used for detecting antibodies to parainfluenza virus type 3 (PIV-3). Overall, seroprevalence to BVDV was 36±7% (SE); seroprevalence varied by district (19–42%). BHV-1 seroprevalence was 67±4%; variation by district was similar to that of BVDV. However, the first 80 serum samples tested by BHV-1 ELISA all had a strong background reaction with the control antigen. Therefore, these sera were adsorbed to a homogenate of non-infected bovine kidney cell line (MDBK) and re-tested by ELISA. The non-specific reactivity was significantly reduced (p < 0.001 by Wilcoxon's signed-rank test). Compared to the virus-neutralisation (VN) test, the adsorbed BHV-1 ELISA showed 94% agreement and gave a κ value of 0.84, indicating that the adsorption did not interfere with test accuracy. Seroprevalence against BRSV was 85±3%, and showed differences across districts. Most of the cows (94±2%) were seropositive to PIV-3, and there were no significant differences among districts.     

Duration of immunity of a quadrivalent vaccine against respiratory diseases caused by BHV-1, PI3V, BVDV, and BRSV in experimentally infected calves

Several laboratory studies assessed the duration of immunity of a quadrivalent vaccine (Rispoval™4, Pfizer Animal Health) against bovine respiratory diseases (BRD) caused by bovine herpes-virus type-1 (BHV-1), parainfluenza type-3 virus (PI₃V), bovine viral-diarrhoea virus type 1 (BVDV), or bovine respiratory syncytial virus (BRSV). Calves between 7 weeks and 6 months of age were allocated to treatment and then were injected with two doses of either the vaccine or the placebo 3 weeks apart. Six to 12 months after the second injection, animals were challenged with BHV-1 (n = 16), PI₃V (n = 31), BVDV (n = 16), or BRSV (n = 20) and the course of viral infection was monitored by serological, haematological (in the BVDV study only), clinical, and virological means for ≥2 weeks. Infection induced mild clinical signs of respiratory disease and elevated rectal temperature in both vaccinated and control animals and was followed by a dramatic rise in neutralising antibodies in all treatment groups. Titres reached higher levels in vaccinated calves than in control calves after challenge with BHV-1, BVDV, or BRSV. On day 3 after PI₃V challenge, virus shedding was reduced from 3.64 log₁₀ TCID₅₀ in control animals to 2.59 log₁₀ TCID₅₀ in vaccinated animals. On days 6 and 8 after BRSV challenge, there were fewer vaccinated animals (n = 2/10 and 0/10, respectively) shedding the virus than control animals (n = 8/10 and 3/10, respectively). Moreover, after challenge, the mean duration of virus shedding was reduced from 3.8 days in control animals to 1 day in vaccinated animals in the BVDV study and from 3.4 days in control animals to 1.2 days in vaccinated animals in the BRSV study. The duration of immunity of ≥6 months for PI₃V, BHV-1 and BVDV, and 12 months for BRSV, after vaccination with Rispoval™4, was associated mainly with enhanced post-challenge antibody response to all four viruses and reduction of the amount or duration of virus shedding or both.     

表达牛呼吸道合胞体病毒G蛋白基因的重组Ⅰ型牛疱疹病毒的构建与鉴定

为构建表达牛呼吸道合胞体病毒(BRSV)G蛋白基因的牛疱疹病毒Ⅰ型(BHV-1)重组病毒,本研究将人工合成的BRSV全长G蛋白基因编码序列插入到巨细胞病毒(CMV)启动子之下构建TK基因缺失转移载体。利用磷酸钙-DNA沉淀法将该转移载体与亲本病毒BHV-1/TK-/LacZ+的基因组DNA共转染牛鼻甲细胞后收获增殖的病毒。通过反向蚀斑筛选,得到重组病毒BHV-1/TK-/G+。PCR检测结果证实G蛋白基因已经插入到了亲本病毒BHV-1/TK-/LacZ+的基因组中,间接免疫荧光试验和western blot证实BHV-1/TK-/G+中的G蛋白基因在感染的细胞中获得了表达。本研究为研制BRSV及其他重要牛传染病的BHV-1病毒活载体疫苗奠定了基础。     

Association of herd BRSV and BHV-1 seroprevalence with respiratory disease and reproductive performance in adult dairy cattle

Background

The aim of this study was to detect the associations between bovine herpesvirus 1 (BHV-1) status of a herd and respiratory disease (BRD) occurrence and reproductive performance in pregnant heifers and cows. The association between management-related factors and higher BRD occurrence was also estimated.

Methods

Serum samples, collected from cows and youngstock from 103 dairy cattle herds, were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhoea virus (BVDV), and Mycoplasma bovis. A questionnaire was used to collect data concerning herd management factors and reproductive performance, as well as the occurrence of clinical signs of respiratory disease in the last two years, as evaluated by the veterinarian or farm manager. Multiple correspondence analysis (MCA) and logistic regression analysis were performed to identify and quantify the risk factors.

Results

A low to moderate prevalence (1-49%) of BRSV antibodies among youngstock was associated with a high occurrence of respiratory disease (OR = 6.2, p = 0.010) in cows and in-calf heifers. Employees of the farm may participate in the spread of such disease. Larger herd size, loose-housing of cows, housing youngstock separately from cows until pregnancy, and purchasing new animals were factors possibly related to a high occurrence of respiratory disease symptoms in pregnant heifers and cows. The highest risk of abortions (> 1.3%) and increased insemination index (number of inseminations per pregnancy) (> 1.9) occurred in herds with a moderate prevalence of BHV-1 antibodies (1-49%) in cows.

Conclusions

BHV-1 was not associated with acute respiratory disease in adult dairy cattle, however was significantly related to reproductive performance. BRSV possesses the main role in respiratory disease complex in adult dairy cattle.     

Differential expression of pro-inflammatory and anti-inflammatory cytokines during experimental infection with low or high virulence bovine viral diarrhea virus in beef calves

The objective was to compare the mRNA expression of pro-inflammatory (TNF-α, IL-1β, IFN-γ, IL-2, IL-12, IL-15) and anti-inflammatory (IL-4, IL-10, TGF-β) cytokines, after experimental infection with low or high virulence noncytopathic (ncp) bovine viral diarrhea virus (BVDV). Thirty BVDV-naïve, beef calves were intranasally inoculated with low (LV; n = 10, SD-1) or high (HV; n = 10, 1373) virulence ncp BVDV or with BVDV-free cell culture medium (Control, n = 10). Calves were euthanized on day 5 post-inoculation, and tracheo-bronchial lymph node and spleen samples were collected for mRNA expression through quantitative-RT-PCR. mRNA levels of pro-inflammatory (TNF-α, IL-1β, IL-2, IFN-γ) and anti-inflammatory (IL-4 and IL-10) cytokines were up-regulated in tracheo-bronchial lymph nodes of HV, but not in LV, compared to the control group (P < 0.05). IL-12 mRNA level was up-regulated in tracheo-bronchial lymph nodes of both LV and HV groups (P ≤ 0.05). A significant up-regulation of IL-15 mRNA was observed in tracheo-bronchial lymph nodes for LV calves (P < 0.002), but not for HV calves. Experimental inoculation with BVDV-2 1373 stimulated significant mRNA expression of pro-inflammatory and anti-inflammatory cytokines. In contrast, inoculation with BVDV-1a SD-1 only resulted in up-regulation of IL-12 and IL-15 mRNA, which is associated with activation of macrophages and NK cells during innate immune response.     

Potential use of hematological and acute phase protein parameters in the diagnosis of acute Schmallenberg virus infection in experimentally infected calves

The initial viraemic phase of Schmallenberg virus (SBV) infection in bovine animals is characterized by the non-specific and inconspicuous clinical signs of pyrexia (>40 °C), drop in milk yield and sometimes diarrhea. As a result, the early detection of SBV epizootics can difficult, and typically only become apparent when the congenital form of the disease is observed. The aim of the study was to describe the course of the acute phase response and haematological findings in bovine calves following experimental SBV infection. No clinical signs except for increase in rectal temperature were observed in the calves inoculated subcutaneously with a Polish strain of SBV. Viral RNA was detected in serum at 2 and 4 days post inoculation (dpi). SBV antibodies were first detected by ELISA (9–21 dpi), and subsequently by virus neutralization test (14–32 dpi). The hematological parameters showed a reduction in mid-size leucocytes (MID), and also in red blood cell count (RBC). An increase in mean corpuscular hemoglobin was also observed in SBV infected calves. No significant difference in acute phase proteins (APP) was observed between experimentally infected and control calves, suggesting limited potential as diagnostic biomarker of acute SBV infection.