Seroepizootiologic study of bovine respiratory syncytial virus in a dairy herd

A 16-month seroepizootiologic study of bovine respiratory syncytial virus (BRSV) infection was conducted in a dairy herd. Results indicated that antibodies to BRSV present in serum from newborn calves were derived through the ingestion of colostrum. This passive immunity in calves became undetectable in an average of 99 days (SD = 36.5; range = 30 to 208 days). Two epizootics of respiratory tract disease occurred during the study period, and an association with BRSV was demonstrated in both epizootics. In the 2 epizootics, clinical signs of respiratory tract disease were only mildly to moderately severe, with no mortality or evidence of chronic pneumonia occurring. Seemingly, the passive immunity failed to protect calves from infection and disease caused by BRSV. Additionally, it was observed that if active immunity was induced by infection with BRSV, this immunity protected from the development of clinical disease, but not from reinfection upon subsequent exposures to BRSV.     

An epizootic of respiratory syncytial virus infection in a dairy herd

Respiratory syncytial virus was the cause of a severe epizootic of bovine respiratory tract disease. The virus, isolated from a sick cow during the epizootic, produced cytopathic effect in a bovine turbinate cell line 14 days after it was inoculated. Additional support for the diagnosis came from the results of pathologic and serologic examinations. Lesions consistently present were severe necrotizing bronchiolitis and epithelial syncytia projecting from bronchiolar and alveolar walls. Also, in the cow from which the virus was isolated, there was tracheitis with a syncytial-like change involving the mucosal epithelium.     

Bovine respiratory syncytial virus infection in an ontario cattle herd

Bovine respiratory syncytial virus was recovered from the lung of a six month old calf that died during an outbreak of respiratory disease in a cattle herd in Ontario. Lung tissue removed from the calf at necropsy, performed within two hours of death, was frozen at -70°C prior to virus isolation attempts. Syncytia and intracytoplasmic inclusions were demonstrated both in histological sections of the calf's lung and in stained cell culture preparations infected with the bovine respiratory syncytial virus isolate. Direct fluorescent antibody and virus neutralization tests serologically confirmed the identity of the isolate.     

Spread of bovine syncytial virus in a dairy herd over a two year period

During a two year period the spread of bovine syncytial virus was monitored in a closed herd of 50 to 100 milking cows. Out of a nucleus of 49 nonpregnant and pregnant heifers, six were found to be infected with bovine syncytial virus. Virus was detected only in the progeny of infected cows and not in the progeny of uninfected animals. Nineteen progeny of the bovine syncytial virus infected cows were studied in detail and virus was isolated from only four. Horizontal spread of the virus did not occur.     

Serological studies of parainfluenza type 3 virus, bovine adenovirus type 3 and bovine respiratory syncytial virus infection in beef calves

Six serum samples were taken at monthly intervals from birth to weaning from each of 41 newborn calves in the autumn and spring calf crops of a beef cow--calf herd. The serum hemagglutination-inhibition (HI) antibody titres to parainfluenza type 3 virus (PIV-3), virus-neutralization (VN) antibody titres to bovine adenovirus type 3 (BAV-3) and bovine respiratory syncytial virus (BRSV) were determined using microtitration techniques. There was serological evidence of a significantly higher incidence of infection with BAV-3 in the fall calves than in the spring calves. Serological responses to BAV-3 were not detected in calves with VN titres of greater than 1/256. Serological evidence of subclinical infection with PIV-3 occurred mainly in late February or early March during a period of marked environmental temperature fluctuations. Serological evidence of a high incidence of infection with BRSV was obtained for both the fall and spring calf crops. Serum antibody appeared to be unable to prevent infection with BRSV. An association between infection with BRSV and clinical pneumonia was found in 3 out of 9 calves. BAV-3 infection was related to pneumonia in only 1 instance; however, there was simultaneous evidence of BRSV infection in this calf. PIV-3 infection was found to be related to pneumonia in only 1 instance. There was serological evidence of infection with BAV-3 in association with the occurrence of diarrhea in 3 calves.     

Investigation of bovine viral diarrhea virus infections in a range beef cattle herd

Bovine viral diarrhea virus (BVDV) infections resulting in clinical disease developed in calves, despite vaccination of dams and high maternal BVDV antibody titers in calves. Eight persistently infected (PI) calves born to immunocompetent dams were identified in the herd. Neutralizing BVDV antibody titers of PI calves had decreased greatly by the time the calves were 1 to 2 months old. Antibody titers of PI calves decreased more rapidly than antibody titers of calves that were not PI. Reduced antibody titers in PI calves allowed detection of BVDV in serum specimens of all PI calves by the time they were 8 weeks old. Persistent infection in suspect calves was detectable serologically and was confirmed by virologic examination of serum specimens 4 months after weaning, when the calves were 9 months old. Growth rates were reduced in viremic calves.     

Laboratory diagnosis methods for bovine respiratory syncytial virus

Laboratory diagnosis of bovine respiratory syncytial (BRS) virus no longer poses a problem. Clinical diagnosis, based on signs of pulmonary emphysema manifest in autumn, should be confirmed by laboratory techniques. Direct isolation of the BRS virus from field samples in cell cultures is often unsuccessful, whereas detection of the viral antigens by staining ultra-thin tissue sections with fluorescein isothiocyanate antibody conjugates is highly effective. Complement fixation and especially indirect immunofluorescence tests are still very useful for the detection of BRS specific antibodies in serum and nasal mucus.

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Kurzfassung Die Erkrankungen der Atemwege die durch den Sinzizialatmungsvirus der Rinder hervorgerufen werden, können zur Zeit mit Leichtigkeit diagnostiziert werden. Die klinische Diagnostik, die auf die Anzeichen eines Lungenemphysems beruhen und im Herbst auftreten, muss durch eine Labordiagnose bestätigt werden. Die Sichtbarmachung der viralen Antigenen mittels Färbung ultradünner Schnitte mit einem durch Fluoreszeinisothiozianat markierten Serum erweist sich wirksam und zuverlässig. Die Isolierung des Virus in den Zellkulturen ist oft sehr schwierig. Bei der Aufstellung der Diagnose ist die Suche nach Antikörpern in den gekoppelten Seren, mit der Komplementbindungsmethode und besonders mit der indirekten Immuno-Fluoreszenz, von grosser Wichtigkeit.

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Resume En cas de troubles respiratoires dus au virus Respiratoire Syncytial Bovin (RSB) le diagnostic peut être posé actuellement sans grande difficulté. Le diagnostic clinique, basé sur les signes d'emphysème pulmonaire, apparaissant en automne, doit être confirmé par un diagnostic de laboratoire. L'isolement de l'agent viral sur culture cellulaire est souvent difficile. La mise en évidence des antigènes viraux par coloration de coupes ultra-fines à l'aide d'un sérum marqué à l'isothiocyanate de fluorescéine est efficace et fiable. La recherche d'anticorps dans des sérums couplés, par les méthodes de fixation du complément et principalement d'immunofluorescence indirecte, est de grande utilité pour l'établissement du diagnostic.

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Riassunto Attualmente la diagnosi sulle turbe respiratorie causate dal virus respiratorio sinciziale bovino (RSB) non presenta difficoltà di rilievo. La diagnosi clinica, basata sui sintomi di enfisema polmonare, che si manifestano in autunno, deve essere confermata mediante una diagnosi di laboratorio. L'isolamento dell'agente virale su coltura cellulare risulta spesso difficile. La messa in evidenza degli antigeni virali mediante colorazione di tagli ultrafini con un siero marcato all'isotiocianato di fluorescina è efficace e ed affidabile. Per stabilire la diagnosi è di grande utilità la ricerca di anticorpi nei sieri combinati, con i metodi del la fissazione del complemento e in particolare con l'immunofluorescenza indiretta.

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This article was originally written in French. Copies of the French version may be obtained free of charge by writing to: Mr J. Rodesch, Commission of the European Communities, DG XIII, Bâtiment Jean Monnet, Rue Alcide de Gasperi, Kirchberg, Luxembourg.     

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.     

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.     

The relationship between antibody status to bovine corona virus and bovine respiratory syncytial virus and disease incidence,reproduction and herd characteristics in dairy herds

Background

Bovine respiratory syncytial virus (BRSV) and bovine corona virus (BCV) affects cattle worldwide. Our objective was to evaluate the effects of these infections on general health and reproduction parameters measurable on herd level and to explore the association between antibody status and some herd characteristics.

Methods

We collected a pooled milk sample from five primiparous cows from 79 Swedish dairy herds in September 2006. The samples were analysed for immunoglobulin G antibodies to BCV and BRSV with indirect enzyme-linked immunosorbent assays. Herd level data from 1 September 2005 to 30 August 2006 were accessed retrospectively. The location of the herds was mapped using a geographical information system.

Results

Ten herds were antibody negative to both viruses and were compared with 69 herds positive to BCV or BRSV or both. Positive herds had a higher (P = 0.001) bulk tank milk somatic cell count (BMSCC) compared with negative herds. The medians for all other analyzed health and reproductive parameters were consistently in favour of the herds negative to both viruses although the differences were not statistically significant. A higher proportion (P = 0.01) of herds used professional technicians for artificial insemination, rather than farm personnel, amongst the 33 herds negative to BCV compared with the 46 positive herds.

Conclusions

Our result shows that herds that were antibody positive to BCV and/or BRSV had a higher BMSCC compared with herds negative to BCV and BRSV. There was also tendency that negative herds had a better general herd health compared with positive. A higher proportion amongst the BCV negative herds used external technicians for AI instead of farm personnel, indicating that it is possible to avoid infection although having regular visits. Negative herds were located in close proximity to positive herds, indicating that local spread and airborne transmission between herds might not be of great importance and that herds can stay free from these infection transmission although virus is circulating in the area.     

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.     

Detection of IgE antibodies to bovine respiratory syncytial virus

The role of IgE antibodies against respiratory syncytial virus has attracted attention for both human and bovine disease. To detect such antibodies, we have developed an enzyme-linked immunosorbent assay (ELISA) specific for bovine respiratory syncytial virus (BRSV). Firstly, anti-serum strongly positive for BRSV-specific IgE was produced by immunizing a levamisole-treated calf with BRSV. The presence and specificity of BRSV-specific IgE in this animal was confirmed with the Praunitz-Kustner (PK) technique. Potential interference in an ELISA by other BRSV-specific immunoglobulin isotypes was eliminated by preferential precipitation of serum samples with 27.5% saturated ammonium sulfate. The correlation between the PK and the ELISA assay was greater than 93% and the ELISA was found to be more specific than the PK. Indeed, in a pilot experimental infection study, the serum levels of BRSV-specific IgE were found to correlate with the symptom expression following repetitive live virus aerosolization. This may prove to be a useful rapid test to study both herd immunity and the potential pathogenic influence of IgE.     

Experimental reproduction of respiratory tract disease with bovine respiratory syncytial virus

An experiment was conducted to reproduce respiratory tract disease with bovine respiratory syncytial virus (BRSV) in one-month-old, colostrum-fed calves. The hypothesized role of viral hypersensitivity and persistent infection in the pathogenesis of BRSV pneumonia was also investigated. For BRSV inoculation a field isolate of BRSV, at the fifth passage level in cell culture, was administered by a combined respiratory tract route (intranasal and intratracheal) for four consecutive days. Four groups of calves were utilized as follows: Group I, 6 calves sham inoculated with uninfected tissue culture fluid and necropsied 21 days after the last inoculation; Group II, 6 calves inoculated with BRSV and necropsied at the time of maximal clinical response (4-6 days after the last inoculation); Group III, 6 calves inoculated with BRSV and necropsied at 21 days after the last inoculation; Group IV, 6 calves inoculated with BRSV, rechallenged with BRSV 10 days after initial exposure, and necropsied at 21 days after the initial inoculation. Clinical response was evaluated by daily monitoring of body temperature, heart rate, respiratory rate, arterial blood gas tensions, hematocrit, total protein, white blood cell count, and fibrinogen. Calves were necropsied and pulmonary surface lesions were quantitated by computer digitization. Viral pneumonia was reporduced in each principal group. Lesions were most extensive in Group II. Disease was not apparent in Group I (controls). Significant differences (p less than 0.05) in body temperature, heart rate, respiratory rate, arterial oxygen tension, and pneumonic surface area were demonstrated between control and infected calves. Results indicate that severe disease and lesions can be induced by BRSV in one-month-old calves that were colostrum-fed and seropositive to BRSV. BRSV rechallenge had minimal effect on disease progression. Based on clinical and pathological response, results did not support viral hypersensitivity or persistent infection as pathogenetic mechanisms of BRSV pneumonia.     

Ribavirin inhibits proliferation of bovine respiratory syncytial virus in vitro

Bovine respiratory syncytial virus (BRSV) is an important pathogen in bovine respiratory diseases in the United States. Proliferation of the disease can reach epidemic proportions with mortality reaching as high as 20%. In vitro work shown here suggests that the antiviral compound Ribavirin will be effective in the treatment of infected animals. Treatment at three dose levels with Ribavirin have shown significant inhibition of BRSV proliferation. Bovine turbinate cells were host cells for this study. Tissue culture specimens, infected and noninfected, were carried for 10 days. Presence of BRSV was verified with the use of monoclonal antibody. In addition, the infection with BRSV and consequential treatment with Ribavirin of calves demonstrated a noticeable reduction in viral symptom but no apparent systemic reaction to drug therapy.     

Reinfection of lambs with bovine respiratory syncytial virus.

Eight lambs which were experimentally infected with bovine respiratory syncytial virus (RSV) when they were six to eight weeks old were challenged with the same virus seven months later. After reinfection, lambs developed mild clinical disease and the virus was isolated from nasal swabs from three lambs and peripheral blood from two lambs. Reinfection resulted in changes in peripheral blood cell populations. There was an early increase in the number of CD8+ T lymphocytes and B (LCA p220+) lymphocytes but the proportions of CD4+ and CD4-CD8- T lymphocytes were significantly reduced. Peripheral blood mononuclear cells obtained from lambs reinfected with bovine RSV showed significantly higher responses to bovine RSV antigen in vitro than those obtained from control lambs but their responses to the mitogen phytohaemagglutinin were significantly lower than in control lambs. RSV-specific IgG, IgM and IgA levels of serum samples obtained 10 days after challenge were significantly higher than those of serum samples obtained before challenge.