National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 102206 Changping District, Beijing, China.
Wuhan Center for Disease Control and Prevention, 430024 Wuhan, Hubei Province, China.
Ticks Tick Borne Dis. 2022 Mar;13(2):101884. doi: 10.1016/j.ttbdis.2021.101884. Epub 2021 Dec 5.
Rhipicephalus microplus is considered to be the most important tick infesting cattle, buffalo, horse, goats as well as other animals. They transmit diseases between domestic animals and act as vectors of a variety of zoonotic pathogens. Although pathogens harbored by R. microplus have been extensively studied, the Rickettsiales pathogens vectored by R. microplus in some areas of China remained largely unexplored. From August to October 2020, a total of 291 R. microplus ticks were collected from goats and cattle in three Southern China provinces, Guangxi (n = 138), Sichuan (n = 120) and Hubei (n = 33) provinces. Phylogenetic analysis based on COI gene sequences shows that these ticks are divided into three distinct clades, indicating the remarkable genetic diversity of R. microplus ticks in China. These samples were subsequently screened for the presence of Rickettsia, Anaplasma and Ehrlichia using conventional PCR and sequencing. Subsequently, five bacterial species were identified. Out of the 120 tick DNA samples from Sichuan province, 35.83% (43/120) were positive for Rickettsia sp. belonging to spotted fever group (SFG), 12.50% (15/120) were positive for Anaplasma marginale and 0.83% (1/120) was identified as A. platys. From the 138 DNA samples from Guangxi province, an Ehrlichia canis-like and Rickettsia sp. were detected, with a positive rate of 11.59% (16/138) and 2.17% (3/138), respectively. A. capra DNA was detected in 4 out of 33 (12.12%) samples from Hubei province. Notably, the 16S, gltA and groEL sequences of the E. canis-like are closely related to the E. canis strain previously identified from China, and form a distinct cluster in the phylogenetic trees. Collectively, our results expand the knowledge on tick-borne Rickettsiales pathogens in China. Because the state of engorgement of ticks was not recorded, it is not clear at this stage whether these pathogens are infecting the ticks or are simply present in the blood meal. Given the public health significance of SFG Rickettsia, A. capra, A. platys and E. canis, a thorough investigation of the diversity and presence of pathogens in R. microplus in areas with tick-associated diseases are needed.
璃眼蜱被认为是最重要的寄生在牛、水牛、马、山羊以及其他动物身上的蜱虫。它们在家畜之间传播疾病，并充当各种人畜共患病原体的媒介。尽管已经对璃眼蜱携带的病原体进行了广泛的研究，但中国一些地区由璃眼蜱传播的立克次体病原体仍在很大程度上未被探索。2020 年 8 月至 10 月，从中国南方三省（广西[ n = 138 ]、四川[ n = 120 ]和湖北[ n = 33 ]）的山羊和牛身上共采集了 291 只璃眼蜱。基于 COI 基因序列的系统发育分析表明，这些蜱虫分为三个不同的分支，表明中国璃眼蜱的遗传多样性非常显著。随后，这些样本通过常规 PCR 和测序检测是否存在立克次体、无形体和埃立克体。随后，鉴定出了 5 种细菌。在来自四川的 120 份蜱虫 DNA 样本中，35.83%（43/120）为斑点热群（SFG）立克次体阳性，12.50%（15/120）为边缘无形体阳性，0.83%（1/120）为平突硬蜱无形体阳性。在来自广西的 138 份 DNA 样本中，检测到犬埃立克体样和立克次体，阳性率分别为 11.59%（16/138）和 2.17%（3/138）。在来自湖北的 33 份样本中，有 4 份（12.12%）检测到绵羊无浆体 DNA。值得注意的是，犬埃立克体样的 16S、gltA 和 groEL 序列与中国先前鉴定的犬埃立克体株密切相关，并在系统发育树中形成一个独特的分支。总的来说，我们的研究结果扩展了中国蜱传立克次体病原体的知识。由于未记录蜱虫的吸血状态，目前尚不清楚这些病原体是正在感染蜱虫，还是仅仅存在于血餐中。鉴于 SFG 立克次体、绵羊无浆体、平突硬蜱无形体和犬埃立克体具有重要的公共卫生意义，需要对与蜱虫相关疾病地区璃眼蜱中的病原体多样性和存在情况进行全面调查。
