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A cross-sectional study was conducted to evaluate the association between herd-level characteristics, management routines and farm-level antibody status of bovine coronavirus (BCV) and bovine respiratory syncytial virus (BRSV) in 257 Swedish dairy herds. The possible spatial clustering of positive herds compared with negative herds was also investigated. For each herd, a pooled milk sample from five primiparous cows was analysed for the presence of antibodies to BCV and BRSV. Herd-level information was obtained by a questionnaire. Logistic regression was used to evaluate the association between predictors and antibody status to BCV and BRSV. Large herd size, being located in southern Sweden, and not providing boots for visitors were found to be associated with being antibody-positive to BCV and BRSV. A short distance to the nearest cattle herd was an additional risk factor for BCV. One of the studied areas was suitable for spatial analysis. Positive herds were not spatially autocorrelated when compared with negative herds as estimated by the K-function regarding both BCV and BRSV. This indicates that local factors such as daily visiting milk trucks and wild animals were unlikely to be important sources of infection in this area. Moran's I statistics and semi-variogram showed no evidence of spatial autocorrelation in the residuals, indicating that remaining unidentified factors are not spatially dependent in the areas under study.

Bulk tank milk samples from 1070 dairy herds in England and Wales were tested by ELISA for antibodies to bovine virus diarrhoea virus (BVDV). A subset of 341 herds was tested by ELISA for antibodies to bovine herpesvirus 1 (BHV-1), bovine respiratory syncytial virus (BRSV) and bovine coronavirus (BCV). None of the herds had less than 40 dairy cows and none had been vaccinated against BVDV. The prevalence of BVDV antibody-positive herds in the national population was estimated at 95 per cent and approximately 65 per cent of the herds had a high level of bulk tank antibody suggestive of recent infection with BVDV. Dairy herds in East Anglia and the south-east of England had a significantly lower risk of being BVDV antibody-positive than herds in the rest of England and Wales. However, these regional differences tended to diminish with increasing herd size. Around 69 per cent of the herds were BHV-1 antibody-positive and all the herds were antibody positive to BRSV and BCV. Comparison with earlier serological surveys revealed that there had been little change in the prevalence and distribution of BVDV antibody-positive herds in England and Wales over the last 20 years, but that there had been an increase in the prevalence of BHV-1 antibody-positive herds.

A serological survey was carried out on pig sera from herds in Northern Ireland to investigate the incidence of reactivity to bovine respiratory syncytial virus (BRSV) antigens. A total of 529 pig sera from 61 herds were tested and 219 (41 per cent) were found to be reactive with BRSV-infected cell cultures in an indirect immunofluorescence test. None of the BRSV-reactive sera immunostained turkey rhinotracheitis virus-infected cell cultures, indicating specificity for BRSV epitopes. The specificity of this reactivity for BRSV antigen was confirmed by double immunolabelling, using monoclonal antibodies to BRSV and two pig sera with different reactivities to BRSV antigens. A longitudinal serological investigation of two litters of pigs indicated that BRSV-serum reactivity developed between six and 11 weeks after birth. The immunofluorescent staining pattern observed with the majority (73 per cent) of the BRSV-reactive pig sera was typical of that observed with known BRSV-reactive bovine sera. The other immunoreactive pig sera stained BRSV-infected cell cultures in an atypical staining pattern. These different reactivity patterns, combined with the results of the serum neutralisation tests, suggest that more than one serotype of a porcine pneumovirus may exist.

A severe outbreak of undifferentiated respiratory disease affecting 119 of 144 (82.6 per cent) two- to five-month-old housed beef calves was studied by monitoring their clinical signs and rectal temperatures daily or every second day for two months. New cases of respiratory disease, which were first identified three weeks after the calves were housed, occurred over a period of 29 days. The cause of the outbreak was not conclusively determined although 20 per cent of the calves sampled showed serological evidence of recent infection with bovine respiratory syncytial virus and parainfluenzavirus 3. Seventeen of 61 calves (27.9 per cent) which were treated with tilmicosin had to be treated again, compared with nine of 58 calves (15.5 per cent) which were treated with both tilmicosin and flunixin meglumine and did not need further treatment, but this difference was not statistically significant.

Antibody levels in bulk tank milk (BTM) against bovine respiratory syncytial virus (BRSV) are used to classify BRSV status of herds. The aim of this study was to investigate how these levels correspond with the time at which the herds were infected. Bulk tank milk, individual milk and serum samples from cows and young stock were investigated using an indirect ELISA. Screenings of BTM from 89 dairy herds during two winter seasons revealed a prevalence of positive herds from 82 per cent to 85 per cent. Eleven herds showed a marked increase in antibody levels between two screenings, indicating new infection. However, two of these herds had been free from BRSV for the last five to seven years. Two newly infected herds were monitored for four years and did not appear to get reinfected. Surprisingly, the BTM antibody levels in these herds remained high throughout the study period, but fluctuated significantly. This shows that the levels of antibodies in BTM can remain high for several years, even in herds where reinfection does not occur. BTM serology is a useful tool in the monitoring of infectious diseases in dairy herds, but has limitations as a diagnostic tool for BRSV infections.

COWS transfer antibody to their calves in colostrum. Although colostral antibody is critical for neonatal survival, it can interfere with endogenous antibody responses. This immunomodulation is significant when vaccination is integral to disease management (Kimman and others 1987). The inhibitory effect of maternally derived antibody on the endogenous immune response has been reported for bovine viral diarrhoea virus (Endsley and others 2003), bovine herpesvirus type 1 (BHV-1) (Bradshaw and Edwards 1996), bovine respiratory syncytial virus (BRSV) (Debouck and others 1994) and parainfluenza virus type 3 (PI3) (Marshall and Frank 1975). Other contributory factors include the dose of vaccine and site of administration, and the age (Siegrist and others 1998) and genetics (O’Neill and others 2006) of the recipient. Quantification of the inhibitory action of pre-existing (maternally derived) antibody on vaccine responses would allow better harmonisation of calf management and vaccination, while minimising non-responsiveness to vaccines and maximising herd immunity. This short communication describes a study to determine the threshold of pre-existing antibody below which vaccination against bovine respiratory viruses could be expected to induce a detectable antibody response in calves. The study population was the Robogen herd of HolsteinCharolais calves maintained at the Roslin Institute, Edinburgh (Young and others 2005). A total of 463 (244 male and 219 female) calves entered the study over four successive years. All the calves received approximately two litres of birth-dam colostrum within six hours of birth. Male calves had unrestricted suckling with their dams at grass, and female calves were weaned by 36 hours and raised indoors. At the start of sampling (day 0), the calves ranged from 60 to 167 days old. Blood samples were collected on days 0, 14, 28, 42, 63 and 77. On day 0, each calf received 2 ml of an attenuated BHV-1/ PI3 vaccine (Imuresp RP; Pfizer Animal Health), administered intranasally. On day 28, each calf received 2 ml of an attenuated BRSV vaccine (Rispoval RS; Pfizer Animal Health), administered intramuscularly; the calves received a second intramuscular dose of 2 ml of this vaccine on day 49. All the vaccinations were given in accordance with the manufacturer’s recommendations. The serum immunoglobulin G (IgG) responses to BHV1 were weak, and excluded from further analysis. The sera were tested by commercial ELISA for total BRSV/IgG (Svanovir BRSV-Ab; Svanova Biotech) and total PI3/IgG (Svanovir PIV3Ab; Svanova Biotech). Samples were tested in duplicate at a dilution of 1:25, using kit conjugate, and optical densities were read at 450 nm. The results were expressed as relative optical density (ROD) percentages compared with a common, strongly positive control. The mean (se) ROD for BRSV IgG on day 0 was 13·8 (20·4) per cent, and for PI3 IgG it was 39·6 (32·9) per cent. The changes (Δ) in antibody levels between the day of vaccination (day 0 or day 28) and days 14, 28, 42, 63 and 77 postvaccination were calculated for all the results. To facilitate regression analysis, all the ROD datasets were normalised by loge transformation. Antibody levels specific to both BRSV and PI3 were determined independently by Biobest Laboratories, using the serum neutralisation test (SNT). For each virus, a representative panel of 30 sera was analysed by SNT, and the relationship with the corresponding ELISA results was evaluated. Using linear regression, equations were developed for both vaccines, linking the SNT titres [~1/X] to the respective ELISA results

The infection dynamics of bovine respiratory syncytial virus (BRSV) were studied in randomly selected Norwegian dairy herds. A total of 134 herds were tested twice, six months apart. The herds were classified as positive for BRSV if at least one animal between 150 and 365 days old tested positive for antibodies against BRSV, thereby representing herds that had most likely had the virus present during the previous year. The prevalence of positive herds at the first and second sampling was 34 per cent and at 41 per cent, respectively, but varied greatly between regions. Negative herds were found in close proximity to positive herds. Some of these herds remained negative despite several new infections nearby. Of the herds initially being negative, 42 per cent changed status to positive during the six months. This occurred at the same rate during summer as winter, but a higher rate of animals in the herds was positive if it took place during winter. Of the herds initially being positive, 33 per cent changed to negative. This indicates that an effective strategy to lower the prevalence and the impact of BRSV could be to employ close surveillance and place a high biosecurity focus on the negative herds.

The prevalence of respiratory pathogens in diseased veal calves was determined in 24 respiratory disease outbreaks in 15 herds in Belgium. Bacteria were cultured from nasopharyngeal swabs and seroconversion against viruses and Mycoplasma bovis was determined on paired sera. At the individual calf level, Mycoplasma species, Mannheimia haemolytica and Pasteurella multocida, were isolated from 70.5 per cent, 21.5 per cent and 26.0 per cent of swabs, respectively. At the herd level, the presence of M bovis could be confirmed in 84.6 per cent of the herds examined. Seroconversion against bovine viral diarrhoea virus (BVDV) was present in 71.4 per cent of herds, parainfluenzavirus type 3 in 53.3 per cent, bovine respiratory syncytial virus in 40.0 per cent, bovine adenovirus type 3 in 46.7 per cent, bovine coronavirus in 30.0 per cent, and bovine herpesvirus type 1 in 26.7 per cent. At postmortem examination, Mycoplasma species could be cultured from 61.9 per cent of pneumonic lungs (n=21). Sixty per cent of calves tested were positive for BVDV (n=20), and 20.0 per cent were positive for bovine respiratory syncytial virus (n=16).