Experimental infection of turkeys with infectious bursal disease virus.

Commercial turkey poults 3 to 6 weeks old were infected experimentally by eyedrop with an infectious bursal disease virus (IBDV) inoculum obtained from chickens experiencing clinical IBD. The IBDV was passed 6 successive times in poults in an attempt to increase its pathogenicity for turkeys. Regardless of passage level, the IBDV infection in poults was subclinical, with no morbidity, mortality, or gross lesions observed. The bursae of Fabricius from infected poults, however, displayed various degrees of microscopic degeneration and IBDV specific fluorescence at 3, 4, and 5 days postinfection (PI). Infected turkeys also developed low levels of virus-neutralizing antibodies against IBDV at 12 days PI. Uninoculated poults kept in the same unit with infected poults also displayed microscopic changes and IBDV specific fluorescence 7 days after their appearance in inoculated poults. The IBDV was isolated from infected poults only after 5 successive passages of bursal material from infected poults in 9-day-old chick embryos. The IBDV from infected embryos was inoculated into susceptible 3-week-old chickens and 5-week-old poults and produced IBDV fluorescence and microscopic pathology in the bursae of infected poults and clinical IBD in infected chickens.