National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan.
Veterinary Research Institute, Peradeniya, Sri Lanka.
Sci Rep. 2019 Nov 6;9(1):16132. doi: 10.1038/s41598-019-52512-y.
Theileria annulata is a haemoprotozoan parasite that causes a cancer-like illness known as tropical theileriosis in cattle. In the course of analyzing the genetic diversity of T. annulata in Sri Lanka, we observed that merozoite-piroplasm surface antigen (tams1) and surface protein (tasp)-like gene sequences obtained from bovine blood DNA samples, which were PCR-positive for T. annulata, were conserved but shared low identity with T. annulata GenBank sequences. Moreover, the 18S rRNA sequences from the Sri Lankan samples contained ten unique single-nucleotide polymorphisms compared with all known T. annulata sequences. The cytochrome b (cob) gene sequences isolated from the Sri Lankan samples were highly conserved and shared low identity scores with similarly conserved T. annulata sequences from GenBank. Phylogenetic analysis showed that the Sri Lankan tams1-like, tasp-like, 18S rRNA, and cob sequences clustered together and formed sister clades to the common ancestors of all known T. annulata and Theileria lestoquardi sequences. These findings demonstrated that the Sri Lankan cattle were not infected with T. annulata but with a new Theileria sp. (designated as Theileria sp. Yokoyama) closely related to T. annulata.
环形泰勒虫是一种血原虫寄生虫，可导致牛罹患一种类似癌症的疾病，称为热带泰勒虫病。在分析斯里兰卡环形泰勒虫的遗传多样性过程中，我们观察到从牛血液 DNA 样本中获得的裂殖子-血孢子表面抗原（tams1）和表面蛋白（tasp）样基因序列，对环形泰勒虫 PCR 检测呈阳性，但与环形泰勒虫 GenBank 序列具有保守性，但同源性较低。此外，与所有已知的环形泰勒虫序列相比，来自斯里兰卡样本的 18S rRNA 序列含有十个独特的单核苷酸多态性。从斯里兰卡样本中分离出的细胞色素 b（cob）基因序列高度保守，与来自 GenBank 的同样保守的环形泰勒虫序列的同源性得分较低。系统发育分析表明，斯里兰卡的 tams1 样、tasp 样、18S rRNA 和 cob 序列聚集在一起，并与所有已知的环形泰勒虫和莱氏泰勒虫序列的共同祖先形成姐妹枝。这些发现表明，斯里兰卡的牛并非感染了环形泰勒虫，而是感染了一种与环形泰勒虫密切相关的新型泰勒虫（命名为环形泰勒虫 Yokoyama 株）。
