Aspects of bovine herpesvirus-1 infection in dairy and beef herds in the Republic of Ireland

<p>Abstract</p> <p>Background</p> <p>Infection with bovine herpesvirus-1 (BHV-1) causes a wide range of disease manifestations, including respiratory disease and abortion, with world-wide distribution. The primary objective of the present study was to describe aspects of BHV-1 infection and control on Irish farms, including herd-level seroprevalence (based on pooled sera) and vaccine usage.</p> <p>Methods</p> <p>The characteristics of a diagnostic indirect BHV-1 antibody ELISA test when used on serum pools were evaluated using laboratory replicates for use in the seroprevalence study. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. A proposed cut off (PCO) PP was applied in a cross-sectional study of a stratified random sample of 1,175 Irish dairy and beef cattle herds in 2009, using serum pools, to estimate herd seroprevalence. The study was observational, based primarily on the analysis of existing samples, and only aggregated results were reported. For these reasons, ethical approval was not required. Bulk milk samples from a subset of 111 dairy herds were analysed using the same ELISA. Information regarding vaccine usage was determined in a telephone survey.</p> <p>Results</p> <p>A PCO PP of 7.88% was determined to give 97.1% sensitivity and 100% specificity relative to the use of the ELISA on individual sera giving maximization of the prevalence independent Youden's index, on receiver operating characteristics analysis of replicate results. The herd-level BHV-1 seroprevalence was 74.9% (95% CI - 69.9%-79.8%), with no significant difference between dairy and beef herds. 95.5% agreement in herd classification was found between bulk milk and serum pools. Only 1.8 percent of farmers used BHV-1 marker vaccine, 80% of which was live while 75% of vaccinated herds were dairy.</p> <p>A significant association was found between herd size (quartiles) and seroprevalence (quartiles).</p> <p>Conclusions</p> <p>The results from this study indicate BHV-1 infection is endemic, although BHV-1 vaccines are rarely used, in the cattle population in Ireland.</p

The Effect of Co-Administration of Inactivated Vaccines Against Bovine Respiratory Disease and Neonatal Calf Diarrhoea

A pilot study was performed to evaluate the safety and serological responses after co-administration of two multivalent inactivated vaccines to pregnant cattle. One vaccine was directed against bovine respiratory disease (BRD) and contained antigens of bovine respiratory syncytial virus (BRSV), parainfluenza 3 virus (PI3) and Mannheimia haemolytica (Mh). The second vaccine targeted neonatal calf diarrhoea (NCD) and was composed of inactivated antigens of bovine rotavirus (BRV), bovine coronavirus (BCV) and E. coli. The use of these combinations have been used more and more by veterinary practitioners as there exist some clear evidence that both vaccines improves the passive protection via the colostrum for the relevant pathogens. However, up until now, no safety or efficacy data has been available concerning such co-administrations. The safety of both vaccines and the serological responses to the BRD vaccine has been evaluated when used at the same time, but without mixing and compared to the responses to the administration of each vaccine independently. There was no evidence of any negative effect on calving or calf health in any of the vaccinated animals. The antibody levels against BRSV and Mh in the sera of the calves from cows vaccinated with both vaccines were not significantly different from the levels in the sera of calves vaccinated with the BRD vaccine alone. The results from this pilot study demonstrated that the co-administration of the two multivalent inactivated vaccines had no detrimental effect on the safety or serological responses to the BRD vaccine compared to the independent use of the vaccines

Clinical disease in sheep caused by bluetongue virus serotype 8, and prevention by an inactivated vaccine.

The ability to reduce clinical signs, induce neutralizing antibodies, and perhaps most importantly, to prevent or reduce viraemia (and therefore virus-transmission), represent primary criteria for assessment of bluetongue virus (BTV) vaccine efficacy. Identification of BTV challenge-strains that reliably induce viraemia and clinical signs comparable to those in naturally infected animals, is therefore important for vaccine evaluation. Texel cross-breed and Dorset Poll sheep vaccinated with inactivated BTV-8 vaccine ('Bovilis(®) BTV8' from MSD Animal Health), were challenged with low-passage BTV-8 (Northern European strain) grown in either insect (Culicoides) or mammalian cell-cultures. The severity of clinical signs was recorded (using a modified numerical scoring-system, which is described) along with viraemia and serum neutralizing (SN) antibody levels. Low level SN-antibodies were detected at the time of challenge (three weeks after vaccination). All unvaccinated control animals became infected after challenge, developing high SN-antibody titres by 21 days post challenge (dpc). Vaccinees showed faster increases in SN-antibody titres ('booster' response), with significantly higher titres at 6 dpc than unvaccinated controls. Although only limited clinical-signs could be attributed to BTV in younger animals infected with the mammalian-cell-culture derived virus, both BTV-8 challenge preparations induced severe clinical signs comparable to 'bluetongue' observed during natural outbreaks in older unvaccinated animals. Challenge with BTV-8 grown in Culicoides cell-cultures seemed to induce greater severity of clinical-scores and 'post-mortem lesions' than the mammalian-derived BTV-8 strain. Vaccination reduced clinical signs, fever, and viraemia equally well after challenge with either virus preparation

Clinical disease in sheep caused by bluetongue virus serotype 8, and prevention by an inactivated vaccine.

The ability to reduce clinical signs, induce neutralizing antibodies, and perhaps most importantly, to prevent or reduce viraemia (and therefore virus-transmission), represent primary criteria for assessment of bluetongue virus (BTV) vaccine efficacy. Identification of BTV challenge-strains that reliably induce viraemia and clinical signs comparable to those in naturally infected animals, is therefore important for vaccine evaluation. Texel cross-breed and Dorset Poll sheep vaccinated with inactivated BTV-8 vaccine ('Bovilis(®) BTV8' from MSD Animal Health), were challenged with low-passage BTV-8 (Northern European strain) grown in either insect (Culicoides) or mammalian cell-cultures. The severity of clinical signs was recorded (using a modified numerical scoring-system, which is described) along with viraemia and serum neutralizing (SN) antibody levels. Low level SN-antibodies were detected at the time of challenge (three weeks after vaccination). All unvaccinated control animals became infected after challenge, developing high SN-antibody titres by 21 days post challenge (dpc). Vaccinees showed faster increases in SN-antibody titres ('booster' response), with significantly higher titres at 6 dpc than unvaccinated controls. Although only limited clinical-signs could be attributed to BTV in younger animals infected with the mammalian-cell-culture derived virus, both BTV-8 challenge preparations induced severe clinical signs comparable to 'bluetongue' observed during natural outbreaks in older unvaccinated animals. Challenge with BTV-8 grown in Culicoides cell-cultures seemed to induce greater severity of clinical-scores and 'post-mortem lesions' than the mammalian-derived BTV-8 strain. Vaccination reduced clinical signs, fever, and viraemia equally well after challenge with either virus preparation