Cortez A P, Ventura R M, Rodrigues A C, Batista J S, Paiva F, Añez N, Machado R Z, Gibson W C, Teixeira M M G
Department of Parasitology, University of São Paulo, SP, Brazil.
Parasitology. 2006 Aug;133(Pt 2):159-69. doi: 10.1017/S0031182006000254. Epub 2006 May 2.
The taxonomic and phylogenetic relationships of Trypanosoma vivax are controversial. It is generally suggested that South American, and East and West African isolates could be classified as subspecies or species allied to T. vivax. This is the first phylogenetic study to compare South American isolates (Brazil and Venezuela) with West/East African T. vivax isolates. Phylogeny using ribosomal sequences positioned all T. vivax isolates tightly together on the periphery of the clade containing all Salivarian trypanosomes. The same branching of isolates within T. vivax clade was observed in all inferred phylogenies using different data sets of sequences (SSU, SSU plus 5.8S or whole ITS rDNA). T. vivax from Brazil, Venezuela and West Africa (Nigeria) were closely related corroborating the West African origin of South American T. vivax, whereas a large genetic distance separated these isolates from the East African isolate (Kenya) analysed. Brazilian isolates from cattle asymptomatic or showing distinct pathology were highly homogeneous. This study did not disclose significant polymorphism to separate West African and South American isolates into different species/subspecies and indicate that the complexity of T. vivax in Africa and of the whole subgenus Trypanosoma (Duttonella) might be higher than previously believed.
间日锥虫的分类学和系统发育关系存在争议。一般认为，南美以及东非和西非的分离株可被归类为间日锥虫的亚种或相关物种。这是首次对南美分离株（巴西和委内瑞拉）与西非/东非间日锥虫分离株进行比较的系统发育研究。利用核糖体序列构建的系统发育树将所有间日锥虫分离株紧密地聚集在包含所有涎源性锥虫的进化枝边缘。在使用不同序列数据集（小亚基核糖体RNA基因（SSU）、SSU加5.8S或整个内转录间隔区核糖体DNA（ITS rDNA））推断的所有系统发育树中，均观察到间日锥虫进化枝内分离株的相同分支情况。来自巴西、委内瑞拉和西非（尼日利亚）的间日锥虫密切相关，这证实了南美间日锥虫起源于西非，而分析的东非分离株（肯尼亚）与这些分离株之间存在较大的遗传距离。来自无症状或表现出明显病理症状的牛的巴西分离株高度同质。这项研究未发现能将西非和南美分离株分为不同物种/亚种的显著多态性，并表明非洲间日锥虫以及整个锥虫属（达顿锥虫亚属）的复杂性可能高于此前的认知。
