犬细小病毒病是由犬细小病毒(Canineparvovirus，CPV)引起的一种多发于幼犬的致死性传染病， 主要表现为出血性肠炎和心肌炎⋯。在自然条件下本病多呈散发，而在养犬比较集中的地方则常群发[2】。目前，预防本病的方法主要依靠接种疫苗(包括灭活疫苗和弱毒疫苗)， 国内外已研制出多种灭活疫苗和弱毒疫苗。但不管是灭活苗、弱毒苗或亚单位苗，其研制都是以大量培养微生物为基础的，这不仅给疫苗的制造带来了局限性，同时在疫苗的安全性、免疫性能、产量及保存方面存在缺陷。在其弱毒疫苗的研制和使用过程中，对疫苗用毒种的选育和鉴定、毒种的遗传稳定性以及毒种有无被强毒株污染等鉴定中都急需一种能准确检测弱毒疫苗株和强毒株的方法。以往是通过接种易感动物，观察易感动物的临床症状、组织学变化来鉴定对易感动物的致病性，据此来鉴定强、弱毒株。此方法影响因素较多，准确性低。本研究根据文献报道的犬细小病毒弱毒疫苗株(CPV．bl14)的序列，同CPV强毒株(GenBank中发表的)的序列比较，发现疫苗株在高度保守的NS1区有较多的突变和基因缺乏，其中有l5个基因缺失发生在CPV的2040bp．2056bp之间。本试验利用弱毒疫苗和强毒株基因组的差异，设计特异引物通过PCR技术从分子水平来鉴定CPV的弱毒疫苗株和强毒株。

Two pairs of PCR primers were designed according to the sequances of the vaccine strain andvirulent strain of CPV．Heminested PCR method was established．Result of the first PCR amplificationshowed the same am plified products of 574bp length ，after the second PCR am plification，the viru lentstrain produced the length 364bp fragment，but the vaccine strain couldn’t produce that．The products ofPCR were examined by electrophoresis an d restriction enzyme digestion．Th e result showed the lengthof the fragment an d enzyme sites were as the same as those designed．Th e PCR assay of CPV wasproved to be spec ific an d sensitive．It shows that this method may be used in discriminating the vaccinestrain an d viru lent strain of CPV or monitoring the vaccinated can ine in order to aviod disease andfinan ciallosing．