Abstract
A live infectious bursal disease virus vaccine increased in virulence when passaged six times in susceptible birds, as judged by damage to the bursa of Fabricius. It is suggested that the increase in virulence of this vaccine was due to the selection of a virulent subpopulation which had been present in the vaccine since its original isolation from the field and which had not been eliminated during its attenuation by passage in cell culture. The vaccine was then plaque purified and a virus strain was selected which protected against challenge, did not damage the bursa and appeared not to passage in birds.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
