Objective: To investigate the prevalence and genetic variation of Theileria in yellow cattle in Xiangxi Autonomous Prefecture of Hunan Province.
Methods: A total of 184 blood specimens were collected from Fenghuang, Huanyuan and Baojing counties of Xiangxi Autonomous Prefecture during the period from August 2018 through August 2019, and were detect using PCR assay with the specific 18S ribosomal rRNA (18S rRNA) gene targeting Theileria. The gene sequences of positive specimens were aligned with the sequences recorded in GenBank, and a phylogenetic tree was created with Plasmodium ovale 18S rRNA as an outgroup.
Results: A total of 143 blood samples were positive for Theileria, with a mean detection rate of 77.7%. Theileria was prevalent in the blood samples from yellow cattle in all three counties, with detection rates of 85.0% in Fenghuang County, 88.3% in Huayuan County and 61.0% in Baojing County, respectively. There was no significant difference in the detection rate of Theileria between Xiangxi yellow cattle and normal yellow cattle (77.2% vs. 79.5%; χ2 = 0.08, P > 0.05), while the detection of Theileria was significantly lower in the housed yellow cattle than in free-range cattle (68.9% vs. 89.7%; χ2 = 22.36, P < 0.01). A total of 18 PCR positive samples were randomly selected for sequencing and analysis, and all samples showed more than 99.0% homology with T. luwenshuni isolates. Phylogenetic analysis showed that the 18 positive samples were clustered into the same branch with T. luwenshuni, but were far away from other isolates.
Conclusions: The prevalence of Theileria is high in yellow cattle from Xiangxi Autonomous Prefecture of Hunan Province, and T. luwenshuni may be the dominant parasite species.
［摘要］ 目的 了解湖南省湘西自治州黄牛泰勒虫感染率和遗传变异。方法 2018年8月至2019年8月, 从湘西自治州凤凰县、花垣县和保靖县采集184份黄牛血液样品, 用基于泰勒虫属18S核糖体RNA (18S rRNA) 基因的PCR方法对所有血液样品进行检测。将部分阳性产物基因序列与GenBank数据库中收录的相应虫株序列进行同源性比对, 以卵形疟原虫18S rRNA基因作为外群构建种系发育树。结果 共143份血液样品检测为泰勒虫阳性, 平均检出率为77.7%。凤凰县、花垣县和保靖县黄牛血液样品均检出泰勒虫, 检出率分别为85.0%、88.3%和61.0%; 湘西黄牛和普通黄牛泰勒虫检出率分别为77.2%和79.5% (χ2 = 0.08, P > 0.05); 舍饲牛群与散养牛群检出率分别为68.9%和89.7% (χ2 = 22.36, P < 0.01)。随机挑选18个PCR阳性样品进行测序与序列分析, 发现所有样品与已知吕氏泰勒虫分离株同源性超过99.0%; 系统进化树分析发现18个样品与吕氏泰勒虫聚为同一分支, 但与其他虫株所属分支相隔较远。结论 湖南省湘西地区黄牛泰勒虫感染率较高, 吕氏泰勒虫可能为优势虫种。.
Keywords:
18S ribosomal RNA; Molecular epidemiology;