Conrad Patricia A, Kjemtrup Anne M, Carreno Ramon A, Thomford John, Wainwright Katlyn, Eberhard Mark, Quick Rob, Telford Sam R, Herwaldt Barbara L
Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, 1126 Haring Hall One Shields Avenue, Davis, CA 95616-8745, USA.
Int J Parasitol. 2006 Jun;36(7):779-89. doi: 10.1016/j.ijpara.2006.03.008. Epub 2006 May 4.
The morphologic, ultrastructural and genotypic characteristics of Babesia duncani n.sp. are described based on the characterization of two isolates (WA1, CA5) obtained from infected human patients in Washington and California. The intraerythrocytic stages of the parasite are morphologically indistinguishable from Babesia microti, which is the most commonly identified cause of human babesiosis in the USA. Intraerythrocytic trophozoites of B. duncani n.sp. are round to oval, with some piriform, ring and ameboid forms. Division occurs by intraerythrocytic schizogony, which results in the formation of merozoites in tetrads (syn. Maltese cross or quadruplet forms). The ultrastructural features of trophozoites and merozoites are similar to those described for B. microti and Theileria spp. However, intralymphocytic schizont stages characteristic of Theileria spp. have not been observed in infected humans. In phylogenetic analyses based on sequence data for the complete18S ribosomal RNA gene, B. duncani n.sp. lies in a distinct clade that includes isolates from humans, dogs and wildlife in the western United States but separate from Babesia sensu stricto, Theileria spp. and B. microti. ITS2 sequence analysis of the B. duncani n.sp. isolates (WA1, CA5) show that they are phylogenetically indistinguishable from each other and from two other human B. duncani-type parasites (CA6, WA2 clone1) but distinct from other Babesia and Theileria species sequenced. This analysis provides robust molecular support that the B. duncani n.sp. isolates are monophyletic and the same species. The morphologic characteristics together with the phylogenetic analysis of two genetic loci support the assertion that B. duncani n.sp. is a distinct species from other known Babesia spp. for which morphologic and sequence information are available.
基于从华盛顿和加利福尼亚州受感染人类患者中获得的两个分离株（WA1、CA5）的特征，描述了邓肯巴贝斯虫（Babesia duncani n.sp.）的形态学、超微结构和基因型特征。该寄生虫的红细胞内期在形态上与微小巴贝斯虫（Babesia microti）无法区分，微小巴贝斯虫是美国人类巴贝斯虫病最常见的确诊病因。邓肯巴贝斯虫的红细胞内滋养体呈圆形至椭圆形，有一些梨形、环状和阿米巴样形态。通过红细胞内裂体增殖进行分裂，导致形成四联体型裂殖子（同义词：马耳他十字形或四联体型）。滋养体和裂殖子的超微结构特征与微小巴贝斯虫和泰勒虫属（Theileria spp.）所描述的特征相似。然而，在受感染人类中未观察到泰勒虫属特有的淋巴细胞内裂殖体阶段。在基于完整18S核糖体RNA基因序列数据的系统发育分析中，邓肯巴贝斯虫位于一个独特的进化枝中，该进化枝包括来自美国西部人类、狗和野生动物的分离株，但与狭义巴贝斯虫、泰勒虫属和微小巴贝斯虫分开。对邓肯巴贝斯虫分离株（WA1、CA5）的ITS2序列分析表明，它们在系统发育上彼此无法区分，并且与另外两种人类邓肯巴贝斯虫型寄生虫（CA6、WA2克隆1）无法区分，但与其他测序的巴贝斯虫和泰勒虫物种不同。该分析提供了有力的分子支持，即邓肯巴贝斯虫分离株是单系的且属于同一物种。形态学特征以及两个基因位点的系统发育分析支持了这样的论断，即邓肯巴贝斯虫是与其他已知巴贝斯虫物种不同的一个独特物种，对于这些已知物种已有形态学和序列信息。
