鸭肝炎病毒A_(66)弱毒株的研究

鸭肝炎病毒I型A_(66)鸡胚化弱毒株,对雏鸭安全、稳定.鸡胚混合毒滴度为10~(7.36-8.09)CELD50/0.1毫升.以1.8万DLD50/0.1毫升的强毒攻击,其半数免疫量为10~(6.16)MID50/0.1毫升;皮下注射的免疫产生期为接种后48小时.免疫持续期测至45天,全部保护.用本弱毒苗免疫雏鸭,可预防I型鸭病毒性肝炎的发生.以该弱毒苗高度免疫成年鸭或猪血制备的抗血清,对雏鸭能产生坚强的被动免疫力.

STUDIES ON THE A66, AN ATTENUATED STRAIN OF DUCK HEPATITIS VIRUS (DHV)

The authors isolated a DHV-A strain type I from an affected Chaohupiebald duckling and have produced an attenuated strain DHV-A_(66) bysuccessively passing it on to embryonating chicken eggs until the 66th time.The attenuated strain A_(66) is lethal for the chicken embryos, causing 100%mortality in 8-10 day-old embryos within 32-48 hours postinoculation. Thetiters of the DHV-66 contained in the mixture of the chicken embryosand the allanto-amniotic fluid are 10~(7.8-8.00)CELD50/0.1m1. After duc-klings are inoculated with DHV-A_(66) by subcutaneous or oral administrationin five hundred-two million DMID_(50) per duckling, they live soundlythrough 10 days observation. We passed the DHV-A_(66) successively backto ducklings by 5 times in large dosages, the result then indicates thatall injected ducklings live well. The DHV-A_(66) DIMD_(50) is 10~(-6.16), 0.1ml, if we vaccinated ducklingswith DHV-A_(66) by subcutaneous in different dosages and challenged themwith 18000 DLD_(50) virulent DHV. The immunity engendering time vaccinatedwith DHV-A_(66) by subcutaneous in 1000 DIMD_(50) is at the 48th hour post-inoculation, and is at the 5th day by oral administration or intranasal cavity.The immunity duration period is at least 45days when challenged theimmunized ducklings with 23000 DLD_(50) virulent DHV. The titration test of DHV-A66 serum antibodies in hyperimmunizedbreeding ducks and castrated hogs have shown that the titers of antiserumin them are high (more than 1:320). Besides, the breeding ducks wouldtransmit to their progeny a high level of passive immunity after the secondvaccination with 2 doses of the attenuated vaccine DHV-A_(66) at least 2weeks interval.