不同宿主源NDV毒株对SPF鸡致病性研究

Pathogenicity of Newcastle disease virus isolated from different avian species

为阐明不同宿主及不同基因型新城疫病毒(NDV)对SPF鸡致病性,选择分离自鸡、番鸭、鹅、健康野鸟的基因Ⅶd亚型NDV6株,鸡源基因Ⅲ型和鸽源基因Ⅵb型毒株各1株,以及基因Ⅸ型强毒F48E9,共9株NDV毒株进行致病性试验。在对各毒株的EID50及主要致病指数MDT、ICPI测定基础之上,以相同剂量感染15日龄SPF鸡,观察临床症状及剖检病变,计算发病率和死亡率,并在攻毒后不同时间采集主要组织样品,以SYBR GreenI Real-timePCR检测病毒最早出现时间及病毒载量。结果表明,6株基因Ⅶd亚型NDV毒株导致SPF鸡100%发病,死亡率90%以上,属于高致病性毒株;基因Ⅲ、Ⅵb型毒株导致SPF鸡发病但不死亡,属于中等毒力毒株。Ⅶd亚型毒株与F48E9株攻毒后SPF鸡在病理变化、组织嗜性及病毒载量上没有显著差异。根据毒株的MDT、ICPI指数及攻毒鸡病程综合判断,Ⅶd亚型毒株在致病性上与F48E9株差异不显著。健康野鸟携带基因Ⅶd亚型高致病性NDV,在NDV的自然生态传播过程中起重要作用,提示应该加强对野鸟的流行病学监测及相关研究。

To study the pathogenicity of different NDV genotype isolated from different avian species, nine NDV strains including 6 Ⅶd genotype NDV strains isolated from chicken, mallard duck, goose and healthy wild birds, 1 genotype Ⅲ NDV strain （chicken）, 1 genotype Ⅵb NDV strain （pigeon） and the F48E9 strain were used to infect 15-day old SPF chickens at the same dosage. Clinical symptom, pathological changes, morbidity and mortality of were monitored. Virus load in major tissues samples was detected by SYBR Green I Real-time PCR at various time points during infection. The results showed that all 6 strains of gild subgenotype NDV belonged to velogenic strains, which caused 100 % mobility and above 90 % mortality respectively; the genotype Ⅲ and genotype Ⅵb NDV belonged to lentogenic strains which caused clinical symptoms but no mortality. No differences were found between Ⅶd subgenotype strains and F48E9 on pathological change, tissue tropism and virus load. The existence of velogenic NDV in healthy wild bird has an important ecological significance, suggesting that urgent actions are required to study the epidemiology of NDV in wild birds populations.