9株猪瘟分离毒株的致病特性

采用9株临床表现强、中、低致病特点的猪瘟野毒分离株第3代细胞毒作为种毒,按3mL/头剂量分别注射猪瘟抗原及抗体阴性猪,再用上一代传代猪发病后的血毒作为下一代接毒用种毒接种试验猪1头或2头,或上一代传代猪发病后,同圈放入1头或2头试验猪进行同居感染.如此进行,GDGZ1/95、BJCY1/96和JL1/94传至8代;FJFQ1/99传至7代;HeBHH1/95、HeNBY1/96、BJTX3/96、GXBH1/98和HeNXH2/98传至3代.结果显示:上述分离株传至3～5代过程中均表现出毒力增强的趋势,从3～5代传代到8(7)代的过程中毒力进一步增强并保持稳定,且均超过了标准石门强毒株的发病特点.所有试验猪均出现较典型的猪瘟临床症状,解剖后均表现出不同程度的病理变化,死后或解剖后的各种脏器经HCFA检查均为强阳性,这种现象进一步证实了猪是猪瘟病毒的敏感动物,各毒株之间毒力没有明显差异.对其中7株分离株传代血毒部分代次E2基因主要区域进行序列分析,结果仅GDGZ1/95株从F1～F8代中的F6代有2个核苷酸的差异,引起1个相应氨基酸的变异,其余毒株的不同代次没有碱基发生变异,初步说明猪瘟病毒基因型表现相对的稳定性.

Pathogenicity of nine Classical swine fever virus isolates

Studies were conducted to investigate the differences and stability of pathogenicity and virulence of some classical swine fever virus isolates in the swine host in China.Nine isolates with high,moderate and low virulence in the field were passaged in cell culture and the passage 3 were used as the seed virus.A dosage of 3 mL seed virus was inoculated into each group of susceptible pigs(negative in CSFV antigen and antibody detection).Blood of the previously inoculated pigs was used for following inoculation of one or two pigs to passage the virus.In this way,GDGZ1/95,BJCY1/96 and JL1/94 isolates were subjected to 8 passages;FJFQ1/99 isolate to 7 passages;and HeBHH1/95,HeNBY1/96,BJTX3/96,GXBH1/98 and HeNXH2/98 to 3 passages.It was revealed that virulence of all isolates was enhanced after 3-5 passages in pigs.The virulence of some isolates was further enhanced and then became stable or even excessive over that of reference virulent strain Shimen after being passaged 3-5 times.Typical signs and pathological lesions of CSF were observed in all inoculated pigs and HCFA positive stains were seen in tissue impressions of necropsied pigs.Sequence analysis was performed within the main domain of the E2 gene from some passages of 7 isolates and revealed that only GDGZ1/95 had one amino acid change in passage 1-8 with passage 6(2 nucleotide change) as exception,while other isolates had the same sequence.It was presumed that genome was conserved and no difference in virulence existed in these isolates.