Spotted Fever Group Rickettsia Infecting Ticks (Acari: Ixodidae), Yak (Bos grunniens), and Tibetan Sheep (Ovis aries) in the Qinghai-Tibetan Plateau Area, China

Yong-Cai He; Ji-Xu Li; Ya-Li Sun; Ming Kang; Hong-Xuan He; Yun-Hai Guo; Ping Ma; Yao-Ping Wei; Rui-Shan Li; Wang-Kai Chen; Zhi-Hong Chen; Jing Li; Tong-Sheng Qi; Jin-Fang Yang; Qing-Xun Zhang; Ye Wang; Jin-Shan Cai; Quan-Bang Zhao; Guang-Wei Hu; Ji-Yong Chen; Ying Li

doi:10.3389/fvets.2021.779387

Spotted Fever Group Rickettsia Infecting Ticks (Acari: Ixodidae), Yak (Bos grunniens), and Tibetan Sheep (Ovis aries) in the Qinghai-Tibetan Plateau Area, China

Front Vet Sci. 2022 Feb 8:8:779387. doi: 10.3389/fvets.2021.779387. eCollection 2021.

Authors

Yong-Cai He^{1

2}, Ji-Xu Li^{1

2}, Ya-Li Sun^{1

2}, Ming Kang^{1

2}, Hong-Xuan He³, Yun-Hai Guo⁴, Ping Ma^{1

2}, Yao-Ping Wei^{1

2}, Rui-Shan Li^{1

2}, Wang-Kai Chen^{1

2}, Zhi-Hong Chen^{1

2}, Jing Li⁵, Tong-Sheng Qi^{1

2}, Jin-Fang Yang^{1

2}, Qing-Xun Zhang³, Ye Wang³, Jin-Shan Cai⁵, Quan-Bang Zhao⁵, Guang-Wei Hu⁵, Ji-Yong Chen⁶, Ying Li^{1

2}

Affiliations

¹ State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, China.
² College of Agriculture and Animal Husbandry, Qinghai University, Xining, China.
³ National Research Center for Wildlife-Born Diseases, University of Chinese Academy of Sciences, Beijing, China.
⁴ National Institute of Parasitic Diseases Chinese Center for Disease Control and Prevention, Shanghai, China.
⁵ Qinghai Provincial Center for Animal Disease Control and Prevention, Xining, China.
⁶ Animal Disease Prevention and Control Center of Yushu, Yushu, China.

Abstract

The Qinghai-Tibet Plateau Area (QTPA) has a complex natural ecosystem, causing a greatly increased risk of spreading various tick-borne diseases including rickettsial infections, which are regarded as one of the oldest known vector-borne zoonoses. However, the information of one of its pathogen, spotted fever group Rickettsia (SFG Rickettsia), is limited in tick vectors and animals in this area. Therefore, this study focused on the investigation of SFG Rickettsia in tick vectors, yaks (Bos grunniens), and Tibetan sheep (Ovis aries) in the QTPA. A total of 1,000 samples were collected from nine sampling sites, including 425 of yaks, 309 of Tibetan sheep, 266 of ticks. By morphological examination, PCR, and sequencing, we confirmed the species of all collected ticks. All tick samples, all yak and Tibetan sheep blood samples were detected based on SFG Rickettsia ompA and sca4 gene. The results showed that all tick samples were identified to be Haemaphysalis qinghaiensis, and the positive rates of SFG Rickettsia were 5.9% (25/425), 0.3% (1/309), and 54.1% (144/266) in yaks, Tibetan sheep, and ticks, respectively. All positive samples were sequenced, and BLASTn analysis of the ompA gene sequences of SFG Rickettsia showed that all positive samples from animals and ticks had 99.04-100% identity with yak and horse isolates from Qinghai Province, China. BLASTn analysis of the sca4 gene sequences of SFG Rickettsia showed that all positive samples had 97.60-98.72% identity with tick isolates from Ukraine. In addition, the phylogenetic analysis showed that all the SFG Rickettsia ompA and sca4 sequences obtained from this study belong to the same clade as Rickettsia raoultii isolated from livestock and ticks from China and other countries. Molecularly, this study detected and characterized SFG Rickettsia both in the tick vectors and animals, suggesting that the relationship between SFG Rickettsia, tick species and animal hosts should be explored to understand their interrelationships, which provide a theoretical basis for preventing control of this pathogen.

Keywords: Haemaphysalis qinghaiensis; Qinghai-Tibetan Plateau Area; Spotted Fever Group Rickettsia; Tibetan sheep; yak.