Vet Pathol 31:358-365 (1994) Experimental Infection of Neonatal Calves with Neurovirulent Bovine Herpesvirus Type 1.3

Abstract. A type of bovine herpesvirus, BHV- 1.3, causes encephalitis in calves, whereas BHV- 1.1 causes respiratory disease. Three colostrum-deprived calves and two colostrum-fed calves were inoculated with BHV-1.3 by intranasal aerosolization. Two colostrum-deprived calves were inoculated with BHV- 1.1 by intranasal aerosolization. BHV- 1.3-inoculated calves demonstrated severe encephalitis with minimal respiratory lesions, and BHV- 1.1-inoculated calves demonstrated severe respiratory lesions and no clinical signs of neurologic disease. Calves fed colostrum that contained virus neutralizing antibodies were protected against neurologic disease. Colostrum-fed BHV- 1.3-inoculated calves did not develop disease although they did become infected; virus was shed in respiratory secretions for 10-1 3 days postinoculation, similar to infected colostrum-deprived calves. BHV- 1.3 was reactivated from a latent state from one colostrum-fed calf after administration of dexa-methasone 60 days postinoculation. Histopathologic examination of the three colostrum-deprived BHV- 1.3-inoculated calves revealed severe lesions of encephalitis. One of the two BHV- 1.1-inoculated calves had one focal lesion of encephalitis. Virus was isolated from brain tissue of colostrum-deprived BHV- 1.3-inoculated calves and from one BHV- 1.1-inoculated calf. Immunohistochemical staining for BHV- 1 antigen was observed in neurons from the colostrum-deprived BHV- 1.3-inoculated calves. Key words: Calves; encephalitis; herpesvirus; infectious bovine rhinotracheitis; meningoencephalitis; neu-rologic disease. Viruses known to cause encephalitis in cattle include rabies, pseudorabies, and malignant catarrhal fever. Natural outbreaks of meningoencephalitis due to bo-vine herpesvirus 1 (BHV-1) have been reported, as have experimental infections using viruses isolated fro