一株血清8a型禽腺病毒的分离鉴定及致病性分析

Isolation,identification and pathogenicity of an avian adenovirus serotype 8a

【目的】研究福建南平地区禽腺病毒(FAdV)血清8a型分离株的遗传演化情况及致病性,旨在为防控血清8a型FAdV感染提供参考。【方法】2022年8月,采集福建南平地区部分肉鸡养殖场出现的以包涵体肝炎为特征的肝脏病料,采用PCR技术检测FAdV核酸,将获得的阳性样品接种在无特定病原体(SPF)鸡胚上进行病原的分离纯化,利用hexon基因测序及序列分析等方法进行病毒鉴定,并在测定分离株毒力的基础上进行动物致病性试验。【结果】接种10 d后,鸡胚死亡,肝脏肿大、出血、坏死、呈土黄色;PCR鉴定和hexon基因序列分析表明,分离株与GenBank上的FAdV E型8a血清型澳大利亚TR59毒株的序列同源性高达99.5%,将该分离株命名为FJNP。FJNP株对1日龄SPF鸡的致死率为44%(11/25);剖检显示,感染鸡肝脏肿大、出血、边缘钝圆、呈土黄色、出现白色坏死点,脾脏和肾脏也出现肿大、出血等症状;肝脏组织病理学检查结果显示,感染鸡肝细胞大量变性坏死,肝细胞核可见嗜碱性包涵体及大量淋巴细胞浸润。实时荧光定量PCR检测显示,感染鸡体内多个组织器官均检测到病毒,且主要分布在肝脏,攻毒3、5、7、14、21 d在泄殖腔中均能检测到病毒。【结论】本研究从临床表现为包涵体肝炎的病鸡肝脏病料中分离到一株具有较强致病性的血清8a型FAdV。

【Objective】The genetic evolution and pathogenicity of fowl avian adenovirus(FAdV) serotype 8a isolates from Nanping,Fujian Province were studied to provide reference for the prevention and control of FAdV 8a infection.【Method】Liver samples characterized by inclusion body hepatitis were collected from broiler farms in Nanping,Fujian Province in August 2022,to detect FAdV nucleic acids by PCR.Then the positive samples were inoculated on specific pathogen free(SPF) chicken embryos for pathogen isolation and purification,and hexon gene was sequenced and analysed for virus identification.Lastly,pathogenicity tests of the FAdV isolates were carried out based on their virulence.【Result】After 10 days of inoculation,chicken embryos died with swollen,bleeding,necrotic,brittle and yellow liver.PCR identification and hexon gene sequence analysis showed that the FAdV isolate(named FJNP) had up to 99.5% homology with Australian TR59 strain of FAdV E serotype 8a.The infection of FJNP led to a fatality rate of 44%(11/25) in 1-day-old SPF chickens.Necropsy demonstrated swollen,bleeding and yellow liver with white necrotic spots and blunt edges in the infected chickens,and their spleen and kidney were also swollen and bleeding.Histopathological examination showed liver degeneration and necrosis with massive lymphocyte infiltration,as well as basophilic inclusions in liver nuclei.Real-time fluorescence quantitative PCR showed that the virus was detected in multiple tissues and organs,mainly in liver,of the infected chickens,and could be detected in cloaca at 3,5,7,14 and 21 d after being challenged.【Conclusion】In this study,a FAdV serotype 8a isolate with strong pathogenicity was isolated from liver samples of diseased chickens with clinical manifestations of inclusion body hepatitis.