Response to several avian respiratory viruses as affected by infectious bursal disease virus.

After being inoculated with the infectious bursal disease virus (IBDV) at one day of age, specific-pathogen-free chickens were inoculated with either Newcastle disease virus (NDV), infectious bronchitis virus (IBV), or infectious laryngotracheitis virus (ILTV). Their immunity was challenged 2-3 weeks later with homologous virus, and antibody titers were determined for ILTV and IBV. Several studies were made to determine the effects of IBDV on the development of persistent or chronic virus infections. Chickens susceptible to IBDV were exposed to IBDV at one day and inoculated at two weeks of age with either NDV, IBV, or ILTV. Two, three, four, and five weeks postinoculation with the respiratory viruses, tracheal swabbings were collected for virus isolations. The birds were challenged with homologous virus at five weeks postinoculation. The results show that early (1-day) infections with IBDV affect the response of young birds to several avian respiratory viruses, as indicated by lowered resistance to challenge and humoral antibody levels for birds inoculated with ILTV and NDV. Birds infected with IBV and IBDV withstood IBV challenge but were much more prone to persistent infections than were birds not exposed to IBDV. High death rates and decreased weights in all IBDV-inoculated groups demonstrated the damaging effects of early IBDV infection.