背景：弓形虫是犬科动物和猫科动物最常见的肠道寄生虫之一。在这项研究中,我们表征了猎豹的T.leonina的整个线粒体（mt）基因组序列，并将其与狗的T.leonina进行了比较。
结果：来自猎豹的T.leonina的整个mt基因组序列大小为14,685bp，比狗长375个基点，比华南虎长408个基点。来自猎豹和狗的T.leonina的两个mt基因组之间的总核苷酸序列(除了非编码区)同一性为92.8%。对于12个蛋白质编码基因，猎豹和狗的T.leonina之间的序列差异在核苷酸水平上为5.0-9.7％，在氨基酸水平上为1.0-7.2％。此外，来自不同宿主的T.leonina分离株（n=23）中mtcox1序列的比较显示出明显的核苷酸差异（10.6％）。系统发育分析表明，利奥尼娜从犬科和猫科动物宿主中分离为三个不同的进化枝。
结论：综合来看，这些mtDNA数据集表明，来自canid和felid宿主的T.leonina代表一个物种复合体。我们的结果对分子流行病学的进一步研究有意义，这种线虫的系统学和种群遗传学。
BACKGROUND: Toxascaris leonina is one of the most common intestinal parasites of canids and felids. In this study, we characterised the entire mitochondrial (mt) genome sequence of T. leonina from the
cheetah and compared it with that of T. leonina from the dog.
RESULTS: The entire mt genome sequence of T. leonina from the
cheetah is 14,685 bp in size, which is 375 bp longer than that from the dog, and it is 408 bp longer than that from the South
China tiger. The overall nucleotide sequence (except for the non-coding region) identity was 92.8% between the two mt genomes of T. leonina from the
cheetah and the dog. For the 12 protein-coding genes, sequence difference between T. leonina from the
cheetah and the dog was 5.0-9.7% at the nucleotide level and 1.0-7.2% at the amino acid level. Moreover, comparison of mt cox1 sequences among T. leonina isolates (n = 23) from different hosts revealed substantial nucleotide differences (10.6%). Phylogenetic analysis showed the separation of T. leonina from canid and felid hosts into three distinct clades.
CONCLUSIONS: Taken together, these mtDNA datasets indicate that T. leonina from canid and felid hosts represents a species complex. Our results have implications for further studies of the molecular epidemiology, systematics and population genetics of this nematode.
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