犬瘟热病毒SD(14)7株对比格犬的致病性研究

对3~4月龄比格犬经肌肉注射方式接种犬瘟热病毒(CDV)SD(14)7株1 mL(病毒含量为106.0 TCID50/mL),并进行体温、淋巴细胞数、眼鼻直肠排毒和组织病毒含量及分布等指标检测,评价变异株SD(14)7对比格犬的致病水平。结果显示,CDV感染后第2天比格犬出现CDV感染的典型特征,如眼和鼻分泌物增多,淋巴细胞明显减少,然而动物的体温变化无明显的“双相热”特征。CDV定量检测结果显示,比格犬攻毒后第10天开始通过眼鼻和直肠向外界排毒,CDV在脾中含量最高。病理剖检可见脾有坏死、肺炎症出血等,病理组织HE和免疫组织化学检测发现脾有严重的充血,淋巴细胞中有CDV抗原,证实该毒株主要感染淋巴组织和器官。此外,比格犬大脑部分神经细胞严重肿胀,在脑中可检测到CDV,表明SD(14)7株具有一定的神经嗜性。本试验结果为进一步鉴定犬瘟热病毒感染比格犬的毒力因子和免疫原性以及疫苗免疫效果的评价奠定了基础。

Pathogenicity of canine distemper virus SD(14)7 strain on beagle dogs

In order to assess the pathogenicity of variant SD(14)7,3-4 month old beagles were inoculated with 1 mL of CDV SD(14)7 strain(106.0 TCID50/mL)by intramuscular injection,and body temperature,number of lymphocytes,content or distribution of virus in tissues,eyes,nose and rectum were measured.The results showed that typical features of CDV infection including increased ocular and nasal secretions,and obvious decreased lymphocytes were found in beagles at 2 days of post-infectious.However,there is no obvious“dual phase fever”during the detection of body temperature.qRT-PCR showed that CDV could be detected in eyes,nose and rectum secretions after 10 days of post-infection,and the copy number of CDV is the highest in spleen.Pathological examination showed necrotic spots in the spleen and inflammation and hemorrhage in the lungs,histopathological HE and immunohistochemical examination revealed severe congestion in the spleen and CDV antigen in lymphocytes,indicating that the CDV strain mainly infected lymphoid tissues and organs.Besides,some nerve cells in the brain of Beagle dogs were severely swollen,and CDV was detected in the brain of the animal,suggesting that CDV SD(14)7 strain had neuronophagocysis.The elucidation of pathogenicity of CDV strain laid a foundation for further identification of virulence factors or immunogenicity,vaccine evaluation of CDV infection in beagle dogs.