Neural changes in recurrent genital infection of infectious bovine rhinotracheitis virus in calves treated with dexamethasone.

Recurrent genital infection with infectious bovine rhinotracheitis (IBR) virus was induced in calves by dexamethasone (DM) treatment 3 months after primary infection. The virus was first recovered from vaginal secretions on the 3rd day after the initiation of DM treatment; however, the virus was not recovered at all from nasal secretions or from the cerebrospinal fluid of the DM-treated calves. The significant neural changes in all recurrent infected calves were nonsuppurative poliomyelitis in the lumbosacral spinal cords and their ganglia, and they were more severe in the sacrospinal cords than in other parts of the spinal cord. The virus antigen was detected in the sacrospinal ganglia and peripheral nerve fibres in the submucosa of the vagina by the fluorescent antibody technique on the 4th and 6th days after the start of DM treatment. These observations indicated that nonsuppurative poliomyelitis may be a characteristic lesion in recurrent genital infection of IBR virus. The sacrospinal cords and ganglia are considered as latent sites of IBR virus.