鸭肝炎病毒A66弱毒株的水平传播感染

Horizontal transmission of attenuated strain A66 of duck hepatitis virus

取10倍免疫剂量的鸭肝炎弱毒活疫苗(A66株),分别经皮下注射和口服途径接种1日龄易感雏鸭20只,5 d后每组取出接种鸭10只分别与20只1 d龄易感雏鸭共同饲养进行第1代同居感染试验,5 d后取第1代同居感染试验鸭10只再与20只1 d龄易感雏鸭共同饲养进行第2代同居感染试验,如此进行5次同居感染试验。定时采集各代次同居感染试验鸭的泄殖腔内容物进行PCR检测,测定鸭肝炎病毒A66弱毒株水平感染能力和排毒情况,并通过对各代次同居感染试验鸭的攻毒试验,测定水平感染的免疫保护作用。结果表明:鸭肝炎弱毒活疫苗(A66株)经皮下注射和口服途径接种雏鸭,均可以通过粪便向体外排泄病毒;同居易感雏鸭可接触感染,感染的雏鸭可获得一定的免疫保护作用;但这种同居感染能力随着同居代次的增加而逐渐减弱,至5代时基本终止。试验结果表明A66毒株可引起雏鸭间的水平传播感染,但这种水平传播能力有限,不会引起毒力返强。

Attenuated strain A66 of duck hepatitis virus was inoculated on 20 one-day-old susceptible ducklings by subcutaneous injection and oral administration,respectively.Five days post-inoculation,10 ducklings from each group were randomly selected,and cohabitated with 20 new one-day-old ducklings.Ten cohabitated ducklings were randomly selected again five days later for the second generation of cohabitation experiment.Such cohabitation experiments were performed 5 times successively.Anal swab samples were collected from each generation of cohabitated animals at designated time,and were analyzed by polymerase chain reaction（PCR） to determine the horizontal infection ability of the attenuated strain A66 and the viral excretion level by the ducklings.Protective immunity was assessed through attacking different generations of ducklings by cohabitation.The results indicated that inoculation of ducklings with the attenuated strain A66 by subcutaneous injection or oral administration was able to result in excretion of the virus through droppings.Cohabitated ducklings could be infected through fecal-oral route,and the infected animals could obtain certain protective immunity.However,the cohabitation infection capacity decreased gradually by the increase of cohabitation generations,and disappeared at the fifth generation.The results demonstrate that strain A66 can cause horizontal transmission of infection among ducklings,but the infection ability is limited and cannot result in reversion to virulence.