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.     

A seroepidemiologic study of bovine respiratory syncytial virus (BRSV) in Turkey

In this study, a survey of cattle for neutralizing antibodies to respiratory syncytial virus (RSV) in Turkey is presented. 490 serum samples were collected from several state farms and some private flocks in different regions of Turkey. The serologic examination was done by the microtiter serum-neutralization technique. In this report, a positive serum antibody titer at dilutions of 1:2 was demonstrated in 226 (46.12%) of the 490 sera tested.     

Bovine respiratory syncytial virus (BRSV): a review

Bovine respiratory syncytial virus (BRSV) infection is the major cause of respiratory disease in calves during the first year of life. The study of the virus has been difficult because of its lability and very poor growth in cell culture. However, during the last decade, the introduction of new immunological and biotechnological techniques has facilitated a more extensive study of BRSV as illustrated by the increasing number of papers published. Despite this growing focus, many aspects of the pathogenesis, epidemiology, immunology etc. remain obscure. The course and outcome of the infection is very complex and unpredictable which makes the diagnosis and subsequent therapy very difficult. BRSV is closely related to human respiratory syncytial virus (HRSV) which is an important cause of respiratory disease in young children. In contrast to BRSV, the recent knowledge of HRSV is regularly extensively reviewed in several books and journals. The present paper contains an updated review on BRSV covering most aspects of the structure, molecular biology, pathogenesis, pathology, clinical features, epidemiology, diagnosis and immunology based on approximately 140 references from international research journals.     

Comparative evaluation of indirect and sandwich ELISA for the detection of antibodies to bovine respiratory syncytial virus (BRSV) in dairy cattle

Seroprevalence of bovine respiratory syncytial virus (BRSV) infection in both exotic and crossbred cattle were described. A baculovirus expressed recombinant purified nucleocapsid (N) protein was used in indirect and sandwich ELISA for screening of 499 bovine sera samples from all over the state for the presence of BRSV antibodies. The seroprevalence rate of BRSV was found to be 46.09% through indirect ELISA while it would found to be 65.33% by sandwich ELISA. The result also indicated that exotic breeds were more susceptible to BRSV infection compared to crossbred cattle. A comprehensive analysis on susceptibility to BRSV as regards to various factors like age and sex was also summarized.     

Prevalence and specificity of antibodies to bovine respiratory syncytial virus in sera from feedlot and range cattle

The specificity of serum antibodies for the polypeptides of bovine respiratory syncytial virus (BRSV) was examined, using sera obtained from feedlot and range cattle. Test results in sera from feedlot cattle indicated a 60% rate of seroconversion and 95% seropositivity to BRSV, associated with lack of clinical signs indicative of respiratory tract disease. Exposure to other common respiratory tract viruses also was high (greater than or equal to 92% to bovine herpesvirus type 1, bovine viral diarrhea virus, and para-influenza virus type 3). Test results in sera from range cattle indicated BRSV seropositive rates of 28% in calves, 49% in yearling cattle, and 70% in mature cows; clinical signs of respiratory tract disease were not observed in these cattle. Antibodies to BRSV in sera from cattle in both environments reacted predominantly with polypeptides of molecular weight 80,000 through 85,000, 40,000, and 28,000. Reactivity to a glycoprotein of molecular weight between 43,000 and 44,000 and to several glycopolypeptides of smaller molecular weight increased in serum specimens obtained from feedlot cattle between time of entry into the feedlot and slaughter.     

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.     

Immunology of bovine respiratory syncytial virus infection of cattle

Bovine respiratory syncytial virus (BRSV) is a respiratory pathogen of cattle that causes severe disease in calves alone and as one of several viruses and bacteria that cause bovine respiratory disease complex. Like human RSV this virus modulates the immune response to avoid stimulation of a vibrant CD8+ T cytotoxic cell response and instead promotes a Th2 response. The Th2 skew sometimes results in the production of IgE antibodies and depresses production of the Th1 cytokine interferon γ. Innate immune cells have a pivotal role in guiding the adaptive response to BRSV, with selective secretion of cytokines by pulmonary dendritic cells. Here we review some of the pertinent observations on immune responses to BRSV infection and vaccination and illustrate how experimental infection models have been used to elucidate the immunopathogenesis of BRSV infection. Recent experiments using intranasal vaccination and/or immune modulation with DNA based adjuvants show promise for effective vaccination by the stimulation of Th1 T cell responses.     

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.     

Serologic studies of bovine respiratory syncytial virus in Minnesota cattle

Serum antibody titers to bovine respiratory syncytial virus were determined for 559 cattle. Serum samples were obtained through the Minnesota State-Federal Brucellosis Laboratory and were collected over a 1-year period. Results of this study revealed an antibody prevalence of 65.5% to bovine respiratory syncytial virus. The distribution of antibody titers is presented, as well as analysis of titers based on breed, sex, and age of the cattle.     

Cell-mediated immune response in cattle to bovine respiratory syncytial virus

Cattle inoculated with bovine respiratory syncytial virus (BRSV) were evaluated for the development of a cell-mediated immune response. Results of the leukocyte migration-inhibition test under agarose and the delayed hypersensitivity test indicated that a cell-mediated immune response was elicited after intranasal inoculation of calves with BRSV. Migration inhibition in the leukocyte migration-inhibition test was detected by postinoculation day (PID) 5 and reached maximum inhibition on PID 21. Inhibition of leukocyte migration was still evident by PID 42 when values were still appreciably greater than preinoculation values. All of the calves inoculated with BRSV developed a delayed hypersensitivity skin response when challenge exposed intradermally with BRSV antigen.     

A bovine herpesvirus (BHV-4) as passenger virus in ethmoidal tumours in Indian cattle

A herpesvirus was isolated from tumours of the ethmoidal mucosa in two of three head of cattle in the State of Kerala, India. The virus designated M40 was cytopathic for a variety of cultured bovine and porcine cells and it did not kill suckling mice or chicken embryos. Sera from tumour-bearing cattle and goats reacted with the M40 virus. Immunofluorescence tests with FITC-conjugated IgG from a bovine monospecific antiserum to bovine herpesvirus 4 (BHV-4) stained the M40 virus specific antigen in infected cells. Experimental infection of goats with the M40 virus did not result in development of tumours. This virus is therefore considered to represent a "passenger" virus. A great similarity was found between restriction patterns of DNAs extracted from M40 virus and the strain 66-P-347, a reference strain of the BHV-4 group.     

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.     

Dot-enzyme linked immunosorbent assay as an alternative technique for the detection of bovine respiratory syncytial virus (BRSV) antibodies

A dot-ELISA test for the detection of anti-BRSV antibodies is described. The objective of this study was the standardisation of a test as a fast, inexpensive and effective alternative to detect anti-BRSV antibodies. Its sensitivity, specificity and usefulness were compared to a commercial ELISA-kit and to the standard serum neutralisation (SN) test. The standardisation of the technique was done using nitrocellulose disks soaked with a viral sample isolated in Brazil, BRSV-25-BR. The best results were obtained when the disks were sensitised with a purified antigen at a concentration of 0.7 microg/disk and the bovine serum was diluted 1: 200. The experiment used 423 samples of bovine serum collected in the main cattle breeding centres in Brazil. The standard SN, dot-ELISA technique and commercial ELISA kits scored 67.8%, 71.8% and 72.3% of the samples as positive, respectively. When compared to the SN test, the standardised dot-ELISA and the commercial ELISA tests presented relative sensitivities of 92.3% and 91.6% and relative specificities of 71.3% and 68.4% respectively. The results demonstrated that the dot-ELISA test is adequate for the objectives proposed by this study, being easy to use and economically viable. Thus, this test represents an alternative for BRSV serological diagnosis in the substitution of SN and commercial ELISA tests, recommendable for utilisation in laboratories with few resources.     

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.     

Prevalence of bovine herpesvirus 1 (BHV-1) infection in Hungarian cattle herds.

Hungarian cattle herds were surveyed for bovine herpesvirus 1 (BHV-1) infection by ELISA of milk and serum samples. In 1993, 75% of the large cattle herds (consisting of more than 50 cattle) and all small herds (small-scale producers' stocks), while in 1997 90% of the small herds were included in the survey. In the case of large herds, 79.3% of the herds and 64.1% of the samples tested were found to be positive. Of the small herds, 13.5% and 15.7% tested positive in 1993 and 1997, respectively. The majority of large herds were Holstein-Friesian dairy stocks. Small herds with an infection rate markedly exceeding the average were found in those counties where the small herds had been in close contact with the large-scale farms, or where new herds were established by using animals of uncontrolled infectious bovine rhinotracheitis (IBR) status originating from large farms. Attention is called to the importance of maintaining the IBR-free status of small herds that constitute one-third of the Hungarian cattle population.     

Prevalence of ovine and bovine respiratory syncytial virus infections in cattle determined with a synthetic peptide-based immunoassay.

Subgroup-specific peptide-based enzyme-linked immunosorbent assays from the G-protein of the ovine and bovine respiratory syncytial virus (RSV), respectively, were used to determine the prevalence of the ovine and bovine subgroup strains of RSV infections in cattle. A total of 1,102 bovine serum samples were obtained from 6 diagnostic laboratories located in the northwestern and the southeastern USA and were tested for antibody to either the bovine or ovine subgroups of RSV. Antibody to viruses from each subgroup was present in samples from each region and all states tested. The Southeast had a higher prevalence of the bovine subgroup strains (69.5%). Then did the Northwest (40.9%). The prevalence of the ovine strain was similar for the two regions (16.7% in the southeast, 14.9% in the northwest). The overall prevalence was 56.6% for the bovine strain and 15.9% for the ovine strain. These results suggest members of the ovine subgroup of RSV circulate in the cattle population but with less frequency than those viruses of the bovine subgroup.     

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.