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.     

Human respiratory syncytial virus infection in the pre-clinical calf model

Human respiratory syncytial virus (hRSV) is the most important respiratory pathogen in young children worldwide. Experimental modelling of hRSV disease by bovine RSV (bRSV) infection in calves provides an important tool for developing new strategies for prevention and treatment. Depending on the scientific hypothesis under investigation, this cognate host-virus model might have the disadvantage of using a highly related but not genetically identical virus. In this study, we aim to describe viral kinetics and (clinical) disease characteristics in calves inoculated with hRSV. Our results show that hRSV infects the upper and, to a lesser extent, the lower respiratory tract of calves. Infection causes upper airway clinical disease symptoms and neutrophilic infiltration of the lower airways. We conclude that a hRSV model in calves may aid future research involving distinct scientific questions related to hRSV disease in children.     

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.     

Effect of the bovine viral diarrhoea virus (BVDV) infection on dairy calf rearing

The aim of this study was to compare the cumulative incidence of mortality, clinical diarrhoea and respiratory disease in calves, during their first six months of age, in herds with different bovine viral diarrhoea virus (BVDV) infection status. Calves’ health indicators were tested by comparing proportions in 101 farms with dissimilar infection condition. The results indicate that there was a significant relationship between the BVDV status (actively infected herd or not) and the cumulative incidence of mortality and respiratory disorders.     

Acute phase protein changes in calves during an outbreak of respiratory disease caused by bovine respiratory syncytial virus

Bovine acute phase proteins (APPs), lipopolysaccharide binding protein (LBP), serum amyloid A (SAA), haptoglobin (Hp) and alpha₁-acid glycoprotein (AGP) were evaluated as inflammatory markers during an outbreak of bovine respiratory disease (BRD) caused by bovine respiratory syncytial virus (BRSV). Calves (n = 10) presented mild to moderate signs of respiratory disease. Secondary bacterial infections, Pasteurella multocida and Mycoplasma dispar as major species, were detected in tracheobronchial lavage samples. Concentrations of SAA and LBP increased at week 1 had the highest values at week 3 and decreased at week 4 of outbreak. Some calves had high Hp concentrations at week 3, but AGP concentrations did not rise during respiratory disease. Higher SAA, LBP and Hp concentrations at a later stage of BRD (week 3) were associated with the low BRSV-specific IgG₁ production, suggesting that these calves had enhanced inflammatory response to the secondary bacterial infection. In conclusion, APPs (especially SAA and LBP) are sensitive markers of respiratory infection, and they may be useful to explore host response to the respiratory infections in clinical research.     

牛呼吸道合胞体病毒RT-PCR检测方法的建立

根据GenBankTM上发表的牛呼吸道合胞体病毒核衣壳蛋白N基因序列,设计合成了一对特异性引物,扩增大小为596bp的目的片段,通过特异性试验、敏感性试验和重复性试验建立了牛呼吸道合胞体病毒的RT-PCR检测方法。所建立的牛呼吸道合胞体病毒的RT-PCR方法与牛腺病毒、牛副流感病毒、牛传染性鼻气管炎病毒、牛无浆体均无交叉反应,该方法的敏感性可达1TCID50。结果表明,该方法具有快速、敏感、特异性强和重复性好等特点,可作为牛呼吸道合胞体病毒检测的一种方法。     

High mortality rate associated with bovine respiratory syncytial virus (BRSV) infection in Belgian white blue calves previously vaccinated with an inactivated BRSV vaccine

In a group of 60 Belgian White Blue calves less than 8 months old still housed in barns, a bovine respiratory syncytial virus (BRSV) outbreak was revealed on the basis of a direct diagnosis (immunofluorescence and virus isolation) performed on the lungs of dead animals, and the kinetics of BRSV neutralizing antibodies. Clinical signs, macroscopical and microscopical pulmonary lesions were also compatible with a BRSV infection. This outbreak is peculiar because the 35 oldest calves (204 +/- 29 days old) had been vaccinated 3-4 months before with an inactivated BRSV vaccine and 30% of these animals had died of respiratory distress. While they experienced a mild respiratory symptomatology, no death was recorded among the 25 youngest calves (69 +/- 29 days old) which had been left unvaccinated. Another peculiarity was found at the histological level where a massive infiltration of eosinophils was demonstrated in the pulmonary tissues of the dead animals. Together these data parallel the dramatic story described 30 years ago in children previously vaccinated with a formalin-inactivated human RSV (HRSV) vaccine upon a natural HRSV challenge. This illustrates that an immunopathological phenomenon also takes place after BRSV vaccination in cattle.     

Atypical interstitial pneumonia (AIP) in calves and young cattle in Schleswig-Holstein in conjunction with an infection by the bovine respiratory syncytial virus (BRSV)

It is reported on atypical interstitial pneumonia (AIP) in 16 mostly Holstein-Frisian calves and feeders from 13 different farms in Schleswig-Holstein in association with an infection by the respiratory syncytial virus (BRSV). All animals were submitted with identical clinical histories. Macroscopically the lung lesions were characterized by alveolar and interstitial edema and emphysema. Microscopically there was a diffuse interstitial pneumonia with formation of hyaline membranes and multinucleated giant cells. From the investigation material of the 16 animals BRSV was confirmed by direct immunofluorescence with monoclonal antibodies in 4 animals from 4 different farms.     

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。     

牛呼吸道合胞体病毒RT-PCR检测方法的建立及初步应用

本研究旨在评估日粮补充以枯草芽孢杆菌、乳酸菌和酵母菌组成的复合益生菌对育肥猪生长性能、小肠绒毛形态及肝脏脂代谢相关指标的影响。试验将208头体重接近的18周龄三元育肥猪随机分为2组,每组4个重复,每个重复26头。对照组育肥猪饲喂基础日粮,处理组育肥猪饲喂基础日粮+1.5 g/kg由乳酸菌、枯草芽孢杆菌和酵母菌组成的复合益生菌,饲养试验时间为8周。结果：处理组试验28 d育肥猪体重、1～28 d和1～56 d平均日增重较对照组显著提高2.28%、10.33%和4.56%（P＜0.05）,但1～28 d和1～56 d料重比显著降低11.15%和5.72%（P＜0.05）。处理组空肠绒毛高度、绒毛高度与隐窝深度比值较对照组分别显著提高5.45%和17.52%（P＜0.05）,而隐窝深度显著降低10.27%（P＜0.05）,对照组与处理组育肥猪血清低密度脂蛋白和高密度脂蛋白浓度及肝脏胆固醇、高密度脂蛋白和低密度脂蛋白浓度无显著差异（P＞0.05）,但处理组育肥猪血清甘油三酯和胆固醇浓度及肝脏甘油三酯浓度显著低于对照组（P＜0.05）。结论：在本研究条件下,日粮添加1.5 g/kg以枯草芽孢杆菌、乳酸菌和酵母菌组成的复合益生菌可通过改善空肠绒毛形态,提高育肥猪生长前期和全期的平均日增重和饲料效率,降低肝脏和血清胆固醇浓度。 [关键词]益生菌|育肥猪|生长性能|绒毛形态|脂代谢     

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.     

Experimental infection of calves with bovine respiratory syncytial virus (Quebec strain).

An experiment was designed to evaluate the clinical, haematological, viral and serological aspects of bovine respiratory syncytial virus infection in calves. Eleven calves were inoculated intranasally with bovine respiratory syncytial virus (Quebec strain) in aerosol. Clinical, haemotological and serological responses of the calves and virus shedding were monitored. The experimentally infected animals manifested moderate to severe signs of respiratory disease. The parameters used to evaluate the severity of the disease included ocular discharge, conjunctivitis, lung sounds, nasal discharge, pyrexia and leukopenia. The animals were scored accordingly (scale infected 70.8-148.5, control 22-29.3). Highest disease scores were observed between day 6-9 after infection. Virological and serological assessment demonstrated that the observed clinical picture was due to bovine respiratory syncytial virus infection.     

Natural transplacental infection of dairy calves with bovine immunodeficiency virus and estimation of effect on neonatal health

Many experimental infection studies with bovine immunodeficiency virus (BIV) have been conducted, but neither virus transmission under natural conditions nor longitudinal clinical effects of naturally occurring infections in non-experimental populations are well explored. We tested the hypotheses that BIV is transmitted across the placenta during gestation and that intragestionally infected calves are at increased risk of neonatal disease. A cohort of 59 dairy cows on one farm were enrolled at parturition and the BIV serostatus of the cows and their pre-colostral calves determined with an indirect fluorescent-antibody assay. Moreover, the enrolled calves were monitored thrice weekly for specific clinical signs through the duration of the 30 day neonatal period and the occurrence of clinical signs analyzed for association with calf pre-colostral BIV serostatus and dam BIV serostatus. Confounding due to calf passive immunity and season of birth were also explored. Forty percent of seropositive cows (14/35) gave birth to seropositive calves but no seropositive calves (0/19) were born to seronegative dams (estimated relative risk 16, 95% exact confidence interval 2.6–5.8×10²⁹). Calf pre-colostral BIV serostatus was not associated with the occurrence or frequency of clinical signs — but dam BIV serostatus was associated with the odds of occurrence of calf hyperthermia and with the frequency of occurrence of calf hyperthermia and hyperventilatory events. This study is inconclusive about the effects of prenatal BIV infection on neonatal health — but it does provide evidence for the natural occurrence of transplacental BIV infection.     

Effects of experimental inoculation of bovine respiratory syncytial virus in different inbred mice lineages: establishment of a murine model for BRSV infection

Bovine respiratory syncytial virus (BRSV), a member of the subfamily Pneumovirinae, family Paramyxoviridae, is a major cause of respiratory disorders in young cattle. A number of studies were conducted to validate a reliable animal model for the infection, since BRSV inoculation on the natural host is costly and often unsuccessful. Unfortunately, after inoculation of BRSV in Balb/C mice, viral replication may be detected; however, evident pathological alterations are absent on the experimentally infected animals. In order to establish a mice model that could be used further for preliminary studies of pathological and immunological aspects of BRSV infection, three mice inbred lineages (Balb/C, A/J and C57BL6), possessing different genetic backgrounds, were tested about its susceptibility to the inoculation with BRSV. Animals were inoculated through the nasal and ocular routes and were observed after inoculation. At 7 days post-inoculation (dpi) animals were necropsied and virological (virus isolation and viral nucleic acid amplification) as well as histopathological examinations were performed. A/J and C57BL6 showed interstitial pneumonia, when compared to the Balb/C group. These findings shows that mice may constitute a suitable model for the study of BRSV infections, depending on the mice strain used for experimental inoculations.     

Evaluation of bovine respiratory syncytial virus (BRSV) and bovine herpesvirus (BHV) specific antibody responses between heterologous and homologous prime-boost vaccinated western Canadian beef calves

Bovine respiratory disease (BRD) is an economically important cause of morbidity and mortality in beef calves. Control of BRD is most often addressed through “homologous” vaccination utilizing the same injectable modified-live viral (MLV) vaccine for both priming and boosting. Heterologous prime-boosting uses different routes and antigenic forms for priming and boosting. Three vaccine protocols were compared: an injectable (IJ) MLV (IJ-MLV) group (IJ-MLV priming at ~48 days and boosted with IJ-MLV at weaning), intranasal (IN) MLV (IN-MLV) group (intranasal priming with MLV at ~24 hours, boosted twice with an IJ-MLV), and intranasal killed viral (IN-KV) group (primed with an IN-MLV at ~24 hours, boosted twice with an IJ-KV). Serum antibody concentrations determined by enzyme-linked immunosorbent assays (ELISAs) were compared and the IN-KV group had significantly higher BRSV-specific antibody concentrations after boosting compared with the 2 homologous groups. No differences in BHV-specific antibody concentrations were observed between any of the groups.     

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.     

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.     

Prevalence of and risk factors for bovine respiratory syncytial virus (BRSV) infection in non-vaccinated dairy and dual-purpose cattle herds in Ecuador

A cross-sectional study was carried out to determine the seroprevalence and risk factors associated with bovine respiratory syncytial virus (BRSV) infection in non-vaccinated dairy and dual-purpose cattle herds from Ecuador. A total of 2,367 serum samples from 346 herds were collected from June 2008 to February 2009. A questionnaire, which included variables related to cattle, health, management measures, and the environment, was filled out in each herd. Presence of antibodies against BRSV was analyzed using a commercial indirect ELISA test. A logistic regression model was used to determine risk factors associated with BRSV at herd level. The individual seroprevalence against BRSV in non-vaccinated herds in Ecuador was 80.48% [1,905/2,367; 95% confidence interval (CI)?=?78.9-82.1]. The herd prevalence was 91.3% (316/346; 95% CI?=?88.3-94.3), and the intra-herd prevalence ranged between 25% and 100% (mean, 90.47%). The logistic regression model showed that the existence of bordering cattle farms, the dual-purpose farms, and the altitude of the farm (more than 2,338?m above sea level) were risk factors associated with BRSV infection. This is the first study about BRSV prevalence in Ecuador. It shows the wide spread of the BRSV infection in the country. The risk factors found will help to design effective control strategies.     

Effect of infection with bovine respiratory syncytial virus on pulmonary clearance of an inhaled antigen in calves

OBJECTIVE: To evaluate the effect of infection with bovine respiratory syncytial virus (BRSV) on clearance of inhaled antigens from the lungs of calves. ANIMALS: Eleven 6- to 8-week-old Holstein bull calves. PROCEDURES: Aerosolized (99m)technetium ((99m)Tc)-labeled diethylene triamine pentacetate (DTPA; 3 calves), commonly used to measure integrity of the pulmonary epithelium, and (99m)Tc-labeled ovalbumin (OA; 8 calves), commonly used as a prototype allergen, were used to evaluate pulmonary clearance before, during, and after experimentally induced infection with BRSV or sham inoculation with BRSV. Uptake in plasma (6 calves) and lung-efferent lymph (1 calf) was examined. RESULTS: Clearance of (99m)Tc-DTPA was significantly increased during BRSV infection; clearance of (99m)Tc-OA was decreased on day 7 after inoculation. Clearance time was correlated with severity of clinical disease, and amounts of (99m)Tc-OA in plasma and lymph were inversely correlated with clearance time. Minimum amounts of (99m)Tc-OA were detected at time points when pulmonary clearance of (99m)Tc-OA was most delayed. CONCLUSIONS AND CLINICAL RELEVANCE: BRSV caused infection of the respiratory tract with peak signs of clinical disease at 7 or 8 days after inoculation. Concurrently, there was a diminished ability to move inhaled protein antigen out of the lungs. Prolonged exposure to inhaled antigens during BRSV infection may enhance antigen presentation with consequent allergic sensitization and development of chronic inflammatory lung disease. IMPACT FOR HUMAN MEDICINE: Infection of humans with respiratory syncytial virus early after birth is associated with subsequent development of allergic asthma. Results for BRSV infection in these calves suggested a supportive mechanism for this scenario.