早期的研究发现,当非洲猪瘟病毒在某一个地区定殖后,其烈性程度降低,亚临床和慢性病例就会增多,而温和型的非洲猪瘟可能只有发热的临床症状[1]。早在2017年,研究人员从拉脱维亚一头被猎杀的野猪中分离出一种基因型II的非HAD型的非洲猪瘟病毒(ASFV),Lv17/WB/Rie1,其显著特征是编码CD2v蛋白的EP402R基因内存在单核苷酸缺失。家猪感染后表现为一种非特异性或亚临床形式的疾病,在某些情况下无临床症状,表现为间歇性的弱病毒血症和高抗体反应[2]。Monteagudo P L等人(2017)发现病毒CD2v(EP402R)基因的缺失使BA71毒株毒力减弱[3]。按照经验推断,随着该病的不断蔓延和关注度的不断提高,ASF分离毒株数量也在不断增加并出现多株自然弱毒株。
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