中文摘要：

目的 通过16S及内转录间区（ITS）rDNA基因序列的扩增、克隆以及序列分析。从分子水平对首次在我国分离的一株牛源贾第虫进行种类及基因型鉴定。方法 根据GenBank中登录的贾第虫rRNA基因序列。设计引物，采用热启动一降落PCR方法从牛源贾第虫基因组DNA中扩增出目的片段。经TA克隆至pMD18-T载体后测定其核苷酸序列，然后进行序列分析。结果 成功地扩增出该株牛源贾第虫的16SrRNA全基因及rDNAITS序列，大小为1715bp，包括1447bp的16SrDNA全长序列和243bp的ITS间区序列，以及25bp的26SrDNA基因5末端。序列分析表明此牛源贾第虫为E型蓝氏贾第虫。结论 本研究从分子水平鉴定我国首株牛源贾第虫为蓝氏贾第虫（E型），并首次报道了该虫株的rDNA 16S及ITS序列，为牛源贾第虫的进一步研究奠定了基础。

英文摘要：

The species and genotype of the first strain of calf-derived Giardia isolate from mainland of China were determined based on 16S ribosomal RNA gene and internal transcribed spacer （ITS） sequences. In which genomic DNA was extracted from the calf-derived Giardia and the 16S and ITS rDNA was amplified by hot-start and touch-down PCR. Then the amplicons was submitted for DNA sequencing after cloning into pMD18-T vector. Result showed that the 1.7kb fragment was successfully amplified and cloned, which consisted of the complete 16S＇ ITS and partial 26S DNA sequences. Sequence analysis revealed that the calf-derived Giardia was Giardia lamblia （Assemblage E）. It was the first time that Giardia was found in dairy cattle from China mainland and confirmed by sequence analysis. The complete sequence of the 16S and ITS rDNA of the Giardia isolates were reported and these results have laid a foundation for further studies of Giardia.