新城疫LaSota活疫苗对基因Ⅶ型分离株的免疫保护性试验

Immune protection assay of Newcastle disease live vaccine(LaSota Strain) against a genotype Ⅶ NDV isolate

从山东省发病鸡群分离鉴定了一株新城疫病毒(NDV),命名为SDLY01。经蚀斑纯化后进行毒力测定和序列分析表明分离株SDLY01属于基因Ⅶ型NDV强毒。20只7日龄SPF鸡免疫新城疫活疫苗LaSot a后14 d分别用NDV标准强毒F48E8和分离株SDLY01攻毒,同时设同日龄SPF鸡为对照组,未免疫任何疫苗。攻毒后观察10 d,免疫组在攻毒后食欲、精神均正常;对照组在攻毒后2～4d发病死亡,并表现ND典型的临床症状和病理变化。攻毒后第3、5、7、9 d对免疫组试验鸡取喉头、泄殖腔棉拭进行病毒分离,F48E8攻毒组病毒分离均为NDV阴性,SDLYO1攻毒组第5 d病毒分离NDV阳性,第3、7和9d病毒分离阴性。本研究结果表明LaSot a活疫苗对F48E8和SDLY01均能提供100%免疫保护,但不能完全抑制基因Ⅶ NDV分离株在体内的复制和排毒。

A NDV isolate SDLY01 was isolated from the chicken of Shandong Province. SDLY01 was determined as a virulent strain with MDT after plague-purification. Phylogenetic analysis showed SDLY01 isolate belonged to the genotype VII linkage. Twenty seven-day-old SPF chickens were vaccinated with NDV live vaccine （LaSota strain） intranasally and intraocularly. Twenty SPF chickens non-vaccinated were served as control. At 21 days of age, chickens were challenged with virus F48E8 or SDLY01 respectively. The chickens in control group began to show clinical signs of ND and died between 2 and 4 days after challenge. No signs of ND were observed in the immunized chickens. Virus was isolated from tracheal and cloacal swabs collected from chickens challenged with SDLY01 at 5 days post-challenge. No virus was detected from chichens challenged with F48ES. The results showed that LDLY01 could replicated in the vaccinated chickens although LaSota vaccine could protect chickens against the challenge with SDLY01 or F48E8.