牛病毒性腹泻病毒致病机理研究进展

The Advance in Pathogenesis of Bovine Viral Diarrhea Virus

牛病毒性腹泻病毒 (BVDV)是危害养牛业的重要病原之一。BVDV感染能够引起广泛的临床症状 ,包括牛病毒性腹泻、粘膜病、持续感染与免疫耐受、繁殖障碍、血小板减少与出血综合征等 ,其相应的致病机理也非常复杂。持续感染是妊娠母畜在怀孕早期通过子宫内感染非致细胞病变 (NCP)型 BVDV引起的 ,是BVDV在自然环境中维持存在的一种重要形式。当持续感染动物再次感染抗原性相似或同源的致细胞病变 (CP)型病毒时就会发生粘膜病。本文将粘膜病发生过程中 CP型病毒的来源机制概括为五点 :1外源细胞序列的插入 ;2病毒基因的重排和拷贝 ;3外源细胞序列插入同时伴有病毒基因的复制 ;4缺陷干扰粒子 ;5点突变。BVDV感染导致奶牛繁殖力下降的机制可能有两条 :一是造成卵母细胞的质量下降 ,二是使性腺类固醇激素生成机制受到破坏 ,导致血浆中雌二醇、黄体酮等激素紊乱。血小板减少和出血性综合征是 BVDV感染引起的又一重要临床症状 ,其致病机理主要有两种 :1BVDV进入到外周循环 ,使外周循环中血小板受损程度增加 ,病理检查表现为血小板体积平均值较正常有明显增大 ;2 BVDV感染造成骨髓生成血小板的能力下降 。

Bovine Viral Diarrhea Virus(BVDV) is an economically important cattle pathogen with a worldwide distribution. Infection with BVDV may result in a wide spectrum of clinical symptoms, including bovine viral diarrhea (BVD), mucosal disease(MD), persistent infection(PI) and immunotolerant, reproductive failure, thrombocytopenia and hemorrhagic syndrome; And their corresponding pathogenesis are also very complicated. PI is crucial for the maintenance of BVDV in cattles. It is caused by infection of pregnant animals with the noncytopathogenic(NCP) BVDV through foetus during the first trimester of pregnancy. It has been shown previously that foetal infection with cytopathogenic(CP) BVDV does not result in persistent infection. MD is the most serious clinical type of BVDV infections. MD has been viewed as the result of persistent infection.It has been documented that super infection of persistently infected animals with an antigenically similar or homologous cpBVDV results in fatal MD, and the sources of the cpBVDV can be generalized from five pionts: ①Insertions of cellular sequences; ②Viral genomic rearrangement and duplications; ③Insertions of cellular sequences,accompaning the viral genomic rearrangement and duplications; ④Defective interference(DI); ⑤The piont mutation. Infection with BVDV can reduce fertility in dairy cow. The mechanism of reproductive disorders have two respects:During the infection with BVDV, ①the quality of the oocytes are impaired; ②the gonadal steroidogenesis encounter disruption, resulting in the disorder of estradiol and progesterone secretion. Thrombocytopenia and hemorrhagic syndrome are two important symptom of BVDV infection. We can classify the mechanism of thrombocytopenia into two ways: ①The platelets in the peripheral circulation were destructed because of the BVDV infection, platelets that have been recently released into the bloodstream from the bone marrow are larger, and therefore mean platelet latelet volume is increased at this situation. ②Thrombocytopenia is attributable to decreased marrow production, older platelets are smaller, and therefore mean plateletlatelet volume is decreased.