Establishment of master stocks for preparation of inactivated vaccine against duck plague.

Comparing with the other two duck plaque virus (DPV) strains for immunogenicity and virulence, the duck embryos-adapted DPV AV1221 (AV1221 DE2) virus strain selected as the master stock. AV1221 DE2 virus was passed in duck embryos for 6 passages in succession and each passage was lyophiled. The virus titers ranged from 104.38 to 105.25 ELD50 per 0.2 mL and the viruses could be neutralized by DPV antiserum. The vaccines prepared with the viruses induce complete protection in ducks after challenge.