A study of two avian adenovirus serotypes alone or in combination with avian infectious bronchitis in day-old chicks

Abstract

Administration of CELO but not GAL virus to 17-day embryos resulted in considerable embryo mortality. When in ovo inoculation of CELO virus was followed by administration of AIB virus on hatching, there was little difference in mortality between the group inoculated with CELO virus alone and the dually inoculated group. In contrast, in ovo inoculation of GAL virus prior to AIB virus resulted in lower chick mortality than did inoculation of GAL virus alone. Prior inoculation with CELO and GAL viruses caused very different effects on the course of an AIB infection. When CELO virus was inoculated prior to AIB virus, no respiratory signs were detected, AIB virus could not be recovered from tissues and no AIB neutralizing antibody was produced. When GAL virus was inoculated prior to AIB virus challenge, respiratory signs were as marked as in chicks inoculated with AIB virus alone, AIB virus could be recovered from most tissues but less easily and for a shorter time than after inoculation with AIB virus alone and there was only a very slight AIB neutralizing antibody response by 28 days after inoculation. Adenoviruses were readily recovered from all chicks, whether inoculated alone or with AIB virus. Neutralizing antibody titres to GAL virus were similar whether or not AIB virus was present. However, CELO virus neutralizing antibody reactions in the dually infected groups were initially delayed, but by 28 days after inoculation were similar to those in the group inoculated with CELO virus alone.