Fenger C K, Granstrom D E, Langemeier J L, Gajadhar A, Cothran G, Tramontin R R, Stamper S, Dubey J P
Department of Veterinary Sciences, University of Kentucky, Lexington 40546.
J Parasitol. 1994 Dec;80(6):966-75.
Sarcocystis neurona is a coccidial parasite that causes a neurologic disease of horses in North and South America. The natural host species are not known and classification is based on ultrastructural analysis. The small subunit ribosomal RNA (SSURNA) gene of S. neurona was amplified using polymerase chain reaction techniques and sequenced by Sanger sequencing reactions. The sequence was compared with partial sequences of S. muris, S. gigantea, S. tenella, S. cruzi, S. arieticanis, S. capracanis, Toxoplasma gondii, Eimeria tenella, and Cryptosporidium parvum. Alignments of available sites for all 10 species and alignments of the entire SSURNA sequence of S. neurona, S. muris, S. cruzi, T. gondii, and C. parvum were performed. Alignments were analyzed using maximum parsimony and maximum likelihood methods to determine relative phylogeny of these organisms. These analyses confirmed placement of S. neurona in the genus Sarcocystis and suggested a close relationship to S. muris, S. gigantea, and T. gondii. Molecular phylogeny suggests that Sarcocystis spp., which utilize the dog (Canis familiaris) as the definitive host, evolved from a common ancestor, whereas those species (including T. gondii) that utilize the cat (Felis domesticus) as the definitive host evolved from another common ancestor. This suggests a possible definitive host for S. neurona.
肉孢子虫是一种球虫寄生虫，在北美洲和南美洲可引发马的神经系统疾病。其天然宿主物种尚不明确，分类基于超微结构分析。利用聚合酶链反应技术扩增肉孢子虫的小亚基核糖体RNA（SSURNA）基因，并通过桑格测序反应进行测序。将该序列与鼠肉孢子虫、巨型肉孢子虫、柔嫩艾美耳球虫、克鲁斯肉孢子虫、羊肉孢子虫、山羊肉孢子虫、刚地弓形虫、柔嫩艾美耳球虫和微小隐孢子虫的部分序列进行比较。对所有10个物种的可用位点进行比对，并对肉孢子虫、鼠肉孢子虫、克鲁斯肉孢子虫、刚地弓形虫和微小隐孢子虫的整个SSURNA序列进行比对。使用最大简约法和最大似然法分析比对结果，以确定这些生物的相对系统发育。这些分析证实了肉孢子虫在肉孢子虫属中的位置，并表明它与鼠肉孢子虫、巨型肉孢子虫和刚地弓形虫关系密切。分子系统发育表明，以犬（家犬）作为终末宿主的肉孢子虫属物种是从一个共同祖先进化而来的，而那些以猫（家猫）作为终末宿主的物种（包括刚地弓形虫）则是从另一个共同祖先进化而来的。这提示了肉孢子虫可能的终末宿主。
