Department of Veterinary Medicine, University of Bari, Valenzano, Italy.
Department of Pathobiology, Institute of Parasitology, University of Veterinary Medicine Vienna, Vienna, Austria.
Vet Microbiol. 2021 Apr;255:109037. doi: 10.1016/j.vetmic.2021.109037. Epub 2021 Mar 10.
Ehrlichia canis is among the most prevalent tick-borne pathogens infecting dogs worldwide, being primarily vectored by brown dog ticks, Rhipicephalus sanguineus sensu lato (s.l.). The genetic variability of E. canis has been assessed by analysis of different genes (e.g., disulfide bond formation protein gene, glycoprotein 19, tandem repeat protein 36 - TRP36) in the Americas, Africa, Asia, and in a single dog sample from Europe (i.e., Spain). This study was aimed to assess the variations in the TRP36 gene of E. canis detected in naturally infected canids and R. sanguineus s.l. ticks from different countries in Asia and Europe. DNA samples from dogs (n = 644), foxes (n = 146), and R. sanguineus s.l. ticks (n = 658) from Austria, Italy, Iran, Pakistan, India, Indonesia, Malaysia, the Philippines, Singapore, Thailand, Vietnam, and Taiwan were included in this study. Ehrlichia canis 16S rRNA positive samples (n = 115 from the previous studies; n = 14 from Austria in this study) were selected for molecular examination by analyses of TRP36 gene. Out of 129 E. canis 16S rRNA positive samples from dogs (n = 88), foxes (n = 7), and R. sanguineus s.l. ticks (n = 34), the TRP36 gene was successfully amplified from 52. The phylogenetic analysis of the TRP36 pre-repeat, tandem repeat, and post repeat regions showed that most samples were genetically close to the United States genogroup, whereas two samples from Austria and one from Pakistan clustered within the Taiwan genogroup. TRP36 sequences from all samples presented a high conserved nucleotide sequence in the tandem repeat region (from 6 to 20 copies), encoding for nine amino acids (i.e., TEDSVSAPA). Our results confirm the US genogroup as the most frequent group in dogs and ticks tested herein, whereas the Taiwan genogroup was present in a lower frequency. Besides, this study described for the first time the US genogroup in red foxes, thus revealing that these canids share identical strains with domestic dogs and R. sanguineus s.l. ticks.
犬埃立克体是全球范围内感染犬类最普遍的蜱传病原体之一，主要由褐家犬蜱，即 Rhipicephalus sanguineus sensu lato (s.l.)传播。通过对美洲、非洲、亚洲以及来自欧洲（即西班牙）的单一犬样本中的不同基因（例如二硫键形成蛋白基因、糖蛋白 19、串联重复蛋白 36-TRP36）进行分析，已经评估了犬埃立克体的遗传变异性。本研究旨在评估在来自亚洲和欧洲不同国家的自然感染犬类和 R. sanguineus s.l. 蜱中检测到的犬埃立克体 TRP36 基因的变异情况。本研究纳入了来自奥地利、意大利、伊朗、巴基斯坦、印度、印度尼西亚、马来西亚、菲律宾、新加坡、泰国、越南和中国台湾的犬（n=644）、狐（n=146）和 R. sanguineus s.l. 蜱（n=658）的 DNA 样本。从之前的研究中（n=115）和本研究中奥地利的（n=14）埃立克体 16S rRNA 阳性样本中选择了分子检测，对 TRP36 基因进行分析。从犬（n=88）、狐（n=7）和 R. sanguineus s.l. 蜱（n=34）的 129 个埃立克体 16S rRNA 阳性样本中，成功扩增了 52 个 TRP36 基因。TRP36 前重复、串联重复和后重复区的系统发育分析表明，大多数样本在遗传上与美国基因群密切相关，而来自奥地利的两个样本和来自巴基斯坦的一个样本聚类在台湾基因群内。所有样本的 TRP36 序列在串联重复区（6-20 个拷贝）中具有高度保守的核苷酸序列，编码 9 个氨基酸（即 TEDSVSAPA）。我们的结果证实了美国基因群是本研究中检测到的犬和蜱中最常见的群体，而台湾基因群的频率较低。此外，本研究首次描述了红狐中的美国基因群，表明这些犬类与家养犬和 R. sanguineus s.l. 蜱共享相同的菌株。
