以来源于湖南省长沙生态动物园猎豹体内的狮弓蛔虫为研究对象，利用保守引物，通过聚合酶链反应（PCR），扩增猎豹狮弓蛔虫线粒体细胞色素c氧化酶I亚基基因（cox1）部分序列（pcox1），并用pcox1序列构建与其他相关蛔虫的进化关系。将获得的序列，用Clustal X 1.83程序进行比对，用Phy ML 3.0程序中的最大似然树法（ML）绘制种系进化树。结果显示：样品pcox1序列长度均为367 bp，种内相对保守（1.4%~6.8%），种间变异显著（9.7%~21.4%）；种系发育关系指示，猫科动物狮弓蛔虫分离株位于同一分支，犬科动物狮弓蛔虫分离株位于另一分支。由于狮弓蛔虫cox1序列种内相对保守，种间差异较大，故可作为狮弓蛔虫种间遗传变异研究的标记。
In order to analyze the sequence variation of the mitochondrial cytochrome c oxidase 1（cox1）gene of Toxascaris leonina isolated from cheetah in Hunan Province，the conserved primers were designed and partial sequence（pcox1）of cox1 gene was amplified by PCR. Then the evolutionary relationship of pcox1 sequences between the amplified strain and other related Ascaris lumbricoides was constructed. The obtained pcox1 sequences were compared by software ClustalX 1.81，and phylogenetic tree was drawn by the maximum likelihood tree-building method in software PhyML 3.0. Results showed that，the lengths of whole pcox1 sequence were 367 bp，which was relatively conserved within the species（1.4% to 6.8%），and the variation between species was significant（9.7% to 21.4%）. Results of phylogenetic relationship analysis indicated that Toxascaris leonina isolated from feline animals located in the same branch，while the Toxascaris leonina isolated from canine animals located in another branch. Given that the sequence of cox1 gene was relatively conserved within species and variable between different species，it could be used as a genetic marker for studying genetic variations between species.