Bovine model of respiratory syncytial virus infection.

Bovine respiratory syncytial virus (BRSV), which is an important cause of respiratory disease in young calves, is genetically and antigenically closely related to human (H)RSV. The epidemiology and pathogenesis of infection with these viruses are similar. The viruses are host-specific and infection produces a spectrum of disease ranging from subclinical to severe bronchiolitis and pneumonia, with the peak incidence of severe disease in individuals less than 6 months of age. BRSV infection in calves reproduces many of the clinical signs associated with HRSV in infants, including fever, rhinorrhoea, coughing, harsh breath sounds and rapid breathing. Although BRSV vaccines have been commercially available for decades, there is a need for greater efficacy. The development of effective BRSV and HRSV vaccines face similar challenges, such as the need to vaccinate at an early age in the presence of maternal antibodies, the failure of natural infection to prevent reinfection, and a history of vaccine-augmented disease. Neutralising monoclonal antibodies (mAbs) to the fusion (F) protein of HRSV, which can protect infants from severe HRSV disease, recognise the F protein of BRSV, and vice versa. Furthermore, bovine and human CD8(+) T-cells, which are known to be important in recovery from RSV infection, recognise similar proteins that are conserved between HRSV and BRSV. Therefore, not only can the bovine model of RSV be used to evaluate vaccine concepts, it can also be used as part of the preclinical assessment of certain HRSV candidate vaccines.

Pandemic (H1N1) 2009 outbreak on pig farm, Argentina.

In June-July 2009, an outbreak of pandemic (H1N1) 2009 infection occurred on a pig farm in Argentina. Molecular analysis indicated that the virus was genetically related to the pandemic (H1N1) 2009 influenza virus strain. The outbreak presumably resulted from direct human-to-pig transmission.

Bovine adenovirus type 3 pneumonia in dexamethasone-treated calves.

The effects of immunosuppression were examined in 1.5-month-old calves that were given dexamethasone (DM) before endobronchial inoculation with bovine adenovirus type 3 (BAV-3). Immunohistopathologically, severe necrotizing bronchiolitis with eosinophilic and basophilic intranuclear inclusion bodies was observed both in DM-treated 1.5-month-old infected calves and in non-DM-treated 7-day-old infected calves. These inclusion bodies were correlated with the detection of BAV-3 antigen and viral particles. The presence of inclusion bodies in the desquamated epithelial cells or of BAV-3 antigen, or both, correlated well with the isolated level of BAV-3 in bronchoalveolar lavage (BAL) fluid. Few immunoglobulin (IgG, IgM, and IgA)-containing B lymphocytes or CD8+ T lymphocytes infiltrated the pneumonic lesion in both the 7-day-old and the DM-treated 1.5-month-old infected calves. Thus, depletion of CD8+ T lymphocytes in calves might influence the clearance of BAV-3 from respiratory tissues.

Paramyxovirus infection in pigs with interstitial pneumonia and encephalitis in the United States.

In the last few years, newly recognized paramyxoviruses have been associated with severe disease in several animal species, including swine, as well as in human beings. Recently, a paramyxovirus was isolated from a swine herd in the northcentral United States that experienced an epizootic of respiratory and central nervous system disease. Affected pigs had interstitial pneumonia with necrotizing bronchiolitis and encephalitis characterized by lymphocytic perivasculitis and diffuse gliosis. Germ-free pigs inoculated with this isolate developed mild clinical illness and similar but less severe histopathologic lesions in lungs and brain.

Pathological studies on camelpox lesions of the respiratory system in the United Arab Emirates (UAE).

Three dromedary camels (Camelus dromedarius), which died from generalized camelpox with lesions in the respiratory system, were investigated. Histopathological lesions in the lung consisted of small, sometimes confluent foci of proliferated bronchial epithelium, necrosis and fibrosis. Orthopoxvirus cameli was demonstrated in all three cases by transmission electron microscopy and the virus was isolated from the lung and trachea on Dubca cells. It was proved by restriction enzyme analysis of the viral DNA that the isolates were identical. Immunohistochemical examination showed numerous poxvirus antigen-positive cells in the bronchial epithelia. Immunolabelled material was found in bronchial epithelial cells with hydropic degeneration and in infiltrating macrophages.

Pathogenesis of naturally acquired bovine respiratory syncytial virus infection in calves: morphologic and serologic findings.

Lesions in 32 calves that died or were euthanatized during the course of severe natural infection with bovine respiratory syncytial virus (BRSV) are described. All calves had been dyspneic for 1 to 2 days. At necropsy, lesions that could be related to dyspnea included congested and cyanotic mucosae and widespread petechiae. The lungs had various lesions in the cranioventral (CV) and caudodorsal (CD) portions. The CV portion of the lungs was consolidated, firm, and edematous. Histologically, the main characteristic was degenerative, necrotic bronchiolitis, with few syncytial cells. Signs of repair, such as epithelial hyperplasia, fibrosis, and bronchiolitis obliterans, often were observed. The CD portion of the lungs was markedly distended, owing to severe edema and emphysema. Bronchiolar lesions were lacking in the CD portion. In 14 calves, hyaline membranes were seen in the CV and CD portions. Results of immunofluorescence for BRSV were positive in 24 calves, but only in the CV portion of the lungs. The calves had variable concentrations of BRSV-specific IgG1 and IgM in serum, lung lavage fluid, or both. The BRSV-specific IgA, on the contrary, was seldom detected. Thus, 2 discrepancies existed. Although the clinical picture appeared to be acute, bronchiolar lesions and serotest results suggested infection of longer duration. Also, although virus and viral cytopathologic features were detected only in the CV portion of the lungs, the CD portion had extensive lesions that consisted of emphysema and edema.

Mycoplasma bovis infection in gnotobiotic calves and combined infection with respiratory syncytial virus.

Mycoplasma bovis was inoculated alone or in combination with respiratory syncytial virus into the respiratory tracts of 12 gnotobiotic calves. Clinical signs ranged from transient pyrexia to protracted fever accompanied by severe lower respiratory signs and in one case, arthritis. Pulmonary lesions included foci of coagulative necrosis surrounded by mononuclear cells and suppurative bronchiolitis with varying degrees of lympho-reticular hyperplasia. No enhancement of lesions occurred in the combined infections of M. bovis and respiratory syncytial virus. M. bovis was identified by immunoperoxidase labelling in lesions of necrosis, especially at interfaces between the lesion and mononuclear cells and in bronchiolar exudates. Organisms were also located in necrotic lesions of joint capsules, in tonsillar crypts, and in liver.

Severe respiratory disease in dairy cattle in New York State associated with bovine respiratory syncytial virus infection.

Severe respiratory disease associated with bovine respiratory syncytial virus (BRSV) infection has been identified in dairy cattle in New York State. The cases identified occurred in dairy calves and heifers. The disease was characterized in 4 animals by pathologic changes including interstitial pneumonia, necrotizing bronchiolitis with multinucleated syncytial epithelial cells and interstitial emphysema. BRSV antigen was demonstrated in lung samples or was isolated in tissue culture in all 4 cases. A retrospective survey of 6279 bovine diagnostic accessions between 1977 and 1982 revealed 66 cases of interstitial pneumonia, often with concurrent bronchiolitis. In this 5 year period, only 1 case in 1981 had interstitial pneumonia and bronchiolitis with pathologic features consistent with BRSV infection. It is concluded that pathogenic BRSV has entered New York State and that it is contributing to clinical respiratory disease in dairy cattle.

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.

Comparison of a microneutralisation test with ELISA and precipitin tests for detection of antibodies to infectious bronchitis virus in chickens.

A microneutralisation test for infectious bronchitis virus using virus antigens available in Australia, cell culture medium containing low concentrations of serum and an elevated incubation temperature is described. The technique was economical on reagents and of comparable sensitivity to the enzyme-linked immunosorbent assay (ELISA). The value of the microneutralisation, ELISA and precipitin tests in assessing the serological response of a flock of commercial chickens to vaccine and natural virus challenge was determined.

Equine infectious respiratory disease.

During the past 20 years the equine population of Great Britain and Ireland has increased with the result that the practising veterinary surgeon is more frequently called upon to advise on equine problems. A significant portion of this advice is concerned with the examination of horses showing signs of this advice is concerned with the examination of horses showing signs of respiratory disease. Numerous pathogens, which include viruses, bacteria, parasites and moulds invade the respiratory tract causing similar signs of illness. It is therefore difficult to provide an aetiological diagnosis based on a clinical examination. Field studies supported by laboratory investigations have established that influenza and herpes viruses are frequently responsible for outbreaks of disease. Epidemiological studies suggest that other factors including the immune state of the equine population influence the distribution and severity of respiratory disease. The aetiology, diagnosis, treatment and control of equine infectious respiratory disease are discussed below.