Susceptibility of chicken embryos to highly virulent infectious bursal disease virus.

The susceptibility of chicken embryos to highly virulent infectious bursal disease virus (hvIBDV), strains F539 and DV86, was examined with respect to three inoculation routes and compared with the classical type of IBDV, strain G691. Death patterns of embryos infected with strains F539 and DV86 of hvIBDV were observed constantly and most of the infected embryos died; however, the death pattern associated with the strain G691 of classical IBDV was erratic and not related to the virus titer inoculated. The chorioallantoic membrane (CAM) route was the most sensitive route of infection, while the allantoic sac (AS) route was the least, regardless of the strain. The difference in titer of hvIBDV between the CAM and yolk sac (YS) route was less than that of classical IBDV. Constant lethality to embryos seems to be distinctive characteristic of hvIBDV.