Identification of a mutant bovine herpesvirus-1 (BHV-1) in post-arrival outbreaks of IBR in feedlot calves and protection with conventional vaccination

Can J Vet Res. 2001 Apr;65(2):81-8.


Outbreaks of infectious bovine rhinotracheitis (IBR) have recently been observed in vaccinated feedlot calves in Alberta a few months post-arrival. To investigate the cause of these outbreaks, lung and tracheal tissues were collected from calves that died of IBR during a post-arrival outbreak of disease. Bovine herpesvirus-1 (BHV-1), the causative agent of IBR, was isolated from 6 out of 15 tissues. Of these 6 isolates, 5 failed to react with a monoclonal antibody specific for one of the epitopes on glycoprotein D, one of the most important antigens of BHV-1. The ability of one of these mutant BHV-1 isolates to cause disease in calves vaccinated with a modified-live IBR vaccine was assessed in an experimental challenge study. After one vaccination, the majority of the calves developed humoral and cellular immune responses. Secondary vaccination resulted in a substantially enhanced level of immunity in all animals. Three months after the second vaccination, calves were either challenged with one of the mutant isolates or with a conventional challenge strain of BHV-1. Regardless of the type of virus used for challenge, vaccinated calves experienced significantly (P < 0.05) less weight loss and temperature rises, had lower nasal scores, and shed less virus than non-vaccinated animals. The only statistically significant (P < 0.05) difference between the 2 challenge viruses was the amount of virus shed, which was higher in non-vaccinated calves challenged with the mutant virus than in those challenged with the conventional virus. These data show that calves vaccinated with a modified-live IBR vaccine are protected from challenge with either the mutant or the conventional virus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alberta / epidemiology
  • Animals
  • Antibodies, Viral / blood
  • Cattle
  • Disease Outbreaks / prevention & control
  • Disease Outbreaks / veterinary*
  • Herpesvirus 1, Bovine / classification
  • Herpesvirus 1, Bovine / genetics
  • Herpesvirus 1, Bovine / immunology
  • Herpesvirus 1, Bovine / isolation & purification*
  • Immunity, Cellular
  • Immunization, Secondary / veterinary
  • Infectious Bovine Rhinotracheitis / epidemiology
  • Infectious Bovine Rhinotracheitis / prevention & control
  • Infectious Bovine Rhinotracheitis / virology*
  • Mutation
  • Random Allocation
  • Time Factors
  • Viral Vaccines*
  • Virus Shedding


  • Antibodies, Viral
  • Viral Vaccines