Baneth Gad, Florin-Christensen Monica, Cardoso Luís, Schnittger Leonhard
Koret School of Veterinary Medicine, Hebrew University, P.O. Box 12, Rehovot, 76100, Israel.
Institute of Pathobiology, Center of Research in Veterinary and Agronomic Sciences, INTA-Castelar, 1686, Hurlingham, Argentina.
Parasit Vectors. 2015 Apr 8;8:207. doi: 10.1186/s13071-015-0830-5.
Theileria annae is a tick-transmitted small piroplasmid that infects dogs and foxes in North America and Europe. Due to disagreement on its placement in the Theileria or Babesia genera, several synonyms have been used for this parasite, including Babesia Spanish dog isolate, Babesia microti-like, Babesia (Theileria) annae, and Babesia cf. microti. Infections by this parasite cause anemia, thrombocytopenia, and azotemia in dogs but are mostly subclinical in red foxes (Vulpes vulpes). Furthermore, high infection rates have been detected among red fox populations in distant regions strongly suggesting that these canines act as the parasite's natural host. This study aims to reassess and harmonize the phylogenetic placement and binomen of T. annae within the order Piroplasmida.
Four molecular phylogenetic trees were constructed using a maximum likelihood algorithm based on DNA alignments of: (i) near-complete 18S rRNA gene sequences (n = 76 and n = 93), (ii) near-complete and incomplete 18S rRNA gene sequences (n = 92), and (iii) tubulin-beta gene sequences (n = 32) from B. microti and B. microti-related parasites including those detected in dogs and foxes.
All phylogenetic trees demonstrate that T. annae and its synonyms are not Theileria parasites but are most closely related with B. microti. The phylogenetic tree based on the 18S rRNA gene forms two separate branches with high bootstrap value, of which one branch corresponds to Babesia species infecting rodents, humans, and macaques, while the other corresponds to species exclusively infecting carnivores. Within the carnivore group, T. annae and its synonyms from distant regions segregate into a single clade with a highly significant bootstrap value corroborating their separate species identity.
Phylogenetic analysis clearly shows that T. annae and its synonyms do not pertain to Theileria and can be clearly defined as a separate species. Based on the facts that T. annae and its synonyms have not been shown to have a leukocyte stage, as expected in Theileria, do not infect humans and rodents as B. microti, and cluster phylogenetically as a separate species, this study proposes to name this parasite Babesia vulpes sp. nov., after its natural host, the red fox V. vulpes.
泰勒虫属的安娜泰勒虫是一种通过蜱传播的小型梨形虫，在北美和欧洲感染犬类和狐狸。由于在其分类归属到泰勒虫属还是巴贝斯虫属上存在分歧，该寄生虫使用了多个同义词，包括西班牙犬巴贝斯虫分离株、微小巴贝斯虫样、巴贝斯虫（泰勒虫）安娜、疑似微小巴贝斯虫。这种寄生虫感染会导致犬类出现贫血、血小板减少和氮血症，但在赤狐（赤狐属）中大多为亚临床感染。此外，在遥远地区的赤狐种群中检测到了高感染率，强烈表明这些犬科动物是该寄生虫的自然宿主。本研究旨在重新评估并统一安娜泰勒虫在梨形虫目的系统发育位置和双名法命名。
使用最大似然算法基于以下DNA比对构建了四个分子系统发育树：（i）近乎完整的18S rRNA基因序列（n = 76和n = 93），（ii）近乎完整和不完整的18S rRNA基因序列（n = 92）以及（iii）来自微小巴贝斯虫和微小巴贝斯虫相关寄生虫（包括在犬类和狐狸中检测到的那些）的微管蛋白β基因序列（n = 32）。
所有系统发育树均表明，安娜泰勒虫及其同义词并非泰勒虫属寄生虫，而是与微小巴贝斯虫关系最为密切。基于18S rRNA基因的系统发育树形成了两个具有高自展值的独立分支，其中一个分支对应感染啮齿动物、人类和猕猴的巴贝斯虫物种，而另一个分支对应仅感染食肉动物的物种。在食肉动物组中，来自遥远地区的安娜泰勒虫及其同义词聚为一个具有高度显著自展值的单一进化枝，证实了它们独立的物种身份。
系统发育分析清楚地表明，安娜泰勒虫及其同义词不属于泰勒虫属，可明确界定为一个独立物种。基于安娜泰勒虫及其同义词未表现出如泰勒虫属预期的白细胞阶段、不像微小巴贝斯虫那样感染人类和啮齿动物以及在系统发育上聚为一个独立物种的事实，本研究提议以其自然宿主赤狐（赤狐属）为该寄生虫命名为新物种巴贝斯虫赤狐。
