中文摘要：

近年来鸭甲型肝炎病毒血清3型引起的小鸭肝炎在我国广泛流行,严重危害着肉鸭养殖业。本研究采用鸭胚连续传代对血清3型鸭甲型肝炎病毒分离株进行致弱,通过检测不同代次的鸭胚组织毒的毒力、稳定性及免疫原性,结果发现该病毒在鸭胚中连续传代至第53代以后对雏鸭无致病性,在雏鸭体内连续继代不出现毒力返强。雏鸭经颈部皮下接种5×10^5.9ELD50的第54代病毒后可刺激机体产生坚强的免疫力。1日龄雏鸭免疫后4 d对强毒感染的保护指数为81.4%,免疫后6天的保护指数为100%。3日龄雏鸭免疫后5 d攻毒保护率为100%。1日龄雏鸭免疫后1周,血清中和抗体水平为10^-3.29,至第4周达到高峰,之后开始缓慢下降。试验结果表明,3型鸭甲型肝炎病毒株第54代弱毒具有良好的免疫原性、毒力稳定,雏鸭接种后诱导产生的免疫力完全可以保护小鸭渡过鸭肝炎易感期,可作为疫苗候选株

英文摘要：

In 2002,a new serotype of duck hepatitis virus（DHAV-3） was first reported in China.Then the infection has been found in many duck-growing areas and caused great economic losses due to the high mortality.To develop a live vaccine against DHAV-3 infection,an isolate was attenuated by serial passage in duck embryos.After 53 passages,the virus did not cause any clinical signs and microscopic lesion in tissues for high dose inoculation,and no virulence reversion was found after repeated passage in 3-day-old ducklings. Ducklings vaccinated with the 54^th virus （5×10^5.9ELD50） on 1 or 3-day-old of age were well protected. The protection index was 81.4% and 100% on day 4 and 6 respectively against the chal- lenge with virulent strain. The virus neutralizing antibody reached 10^-3.29 at day 7 after vaccination of 1- day-old ducklings and peaked at 4＇h week. The level of immunity was sufficient to protect ducklings through the susceptible period. These results demonstrate that the attenuated virus is a promising vaccine candidate for the prevention of DHAV-3 infection.