A large outbreak of bovine botulism possibly linked to a massive contamination of grass silage by type D/C Clostridium botulinum spores on a farm with dairy and poultry operations.

Type D bovine botulism outbreaks associated with poultry litter are increasingly reported in European countries, but the circumstances of exposure to Clostridium botulinum toxins remain unclear. In spring 2015, a large type D/C bovine botulism outbreak affected a farm with dairy and poultry operations. Epidemiological and laboratory investigations strongly suggest that the outbreak was caused by feeding cattle with insufficiently acidified grass silage that was contaminated by type D/C C. botulinum spores. The source of the spores remains unclear, but could have been a stack of poultry litter stored in the grass silage pasture before harvesting. The presence of putrefied poultry carcasses mixed in with the litter is relatively unlikely considering the careful daily removal of poultry carcasses. These findings reinforce the importance of proper ensiling of feed materials and highlight the need for safe disposal of poultry litter, even in the case of good management of poultry deadstock, in order to prevent bovine botulism.

Detection by real-time RT-PCR of a bovine respiratory syncytial virus vaccine in calves vaccinated intranasally.

Seventeen four- to five-week-old calves that were not shedding bovine respiratory syncytial virus (BRSV) were vaccinated intranasally against the disease and sampled by nasal swabbing on 16 different days for up to 20 days after vaccination. BRSV vaccine virus was detected in 15 of the 17 calves. Five of the calves were PCR positive on only one swab, eight were PCR positive on two to five swabs and two were PCR positive on more than five swabs. Twelve of the calves were positive only before day 14 and three were positive after day 14. The nasal shedding of BRSV vaccine virus was very variable.

Evidence for biotype-specific effects of bovine viral diarrhoea virus on biological responses in acutely infected calves.

The relationship between the two biotypes of bovine viral diarrhoea virus (BVDV) and the biological responses they induce was studied in 3- to 6-month-old calves inoculated intranasally with a homologous pair of non-cytopathic and cytopathic strains. Marked differences in virological and serological events occurred following exposure to a specific BVDV strain. The non-cytopathic biotype was frequently recovered from nasal secretions and blood cells during the first 28 days post-inoculation whereas the cytopathic counterpart was detected infrequently in nasopharyngeal swabs only. There was no correlation of the recovery of infectious virus in vivo with the biotype-specific neutralizing humoral immune response. Furthermore, seroconversion did not correlate with resistance to reinfection as judged by the transient viraemia and/or shedding of virus observed in a challenge experiment.

Characterization of the immune response of cattle against non-cytopathic and cytopathic biotypes of bovine viral diarrhoea virus.

Cross-infection studies of normal calves infected with homologous pairs of non-cytopathic and cytopathic bovine viral diarrhoea virus (BVDV) showed significant differences in both humoral and cell-mediated immune responses against either biotype over a period of 5 months. Serological assays after primary intranasal inoculation showed striking significant (P < 0.05) differences between biotypes. Neutralizing titres were detected earlier and were much higher with the non-cytopathic strain than with the homologous cytopathic strain. Significant biotype-specific differences were also observed in the lymphocyte proliferative responses of cattle following in vitro stimulation by non-cytopathic/cytopathic BVDV and the non-structural p80 protein (NS3). The secondary immune response seems to be largely influenced by the biotype used for the primary inoculation and only to a lesser extent by the biotype inoculated for the second time after an interval of 91 days. Animals exposed twice to the cytopathic biotype, which exhibited the lowest antibody titres, showed evidence of BVDV-specific cell-mediated immunity as measured by lympho-proliferation against BVDV. In contrast, the antibody response in the subgroup of animals inoculated twice with homologous non-cytopathic virus was inversely correlated with the proliferative responses. These differences in the immune response were not readily apparent for the two other remaining subgroups which had received cytopathic or non-cytopathic biotypes alone following the second inoculation with non-cytopathic or cytopathic viruses, respectively. Taken together, these data suggest that the differences in immune responses against cytopathic or non-cytopathic strains may be due to a Th1/Th2-like regulatory mechanism.