The pathological features of severe cases of infectious bovine rhinotracheitis.

In recent outbreaks of infectious bovine rhinotracheitis (IBR) in Britain a proportion of the animals affected developed a severe clinical disease characterised, at necropsy, by widespread damage to the respiratory tract. They had necrotising rhinitis, pharyngitis, laryngotracheobronchitis with extensive pseudomembrane formation and severe pneumonia with or without interstitial emphysema. Renal infarction was seen in approximatley half of the cases. The central nervous system was not affected in any of the 25 animals with severe IBR examined in this study. Tissues from the respiratory tract of 14 animals were examined for the presence of bovine herpesvirus 1 and the virus was isolated from the nasal passages of 11 and the lungs of four. Mycoplasma bovis was frequently isolated in large numbers from both the upper and lower respiratory tract.