High prevalence of <i>Rickettsia raoultii</i> in yaks from Xining City of Qinghai Province, China

Recent research on zoonotic diseases has increasingly focused on tick-borne illnesses due to their high prevalence in northwestern China. This study aimed to determine the prevalence of tick-borne pathogens in yaks (<i>Bos grunniens</i>) within Qinghai Province. A total of 299 blood samples were collected from yaks in Xining City of Qinghai Province and analysed using polymerase chain reaction. Results indicated the absence of several significant zoonotic pathogens, including <i>Borrelia burgdorferi</i> sensu lato, <i>Anaplasma</i> spp. and <i>Coxiella burnetii</i>. However, rickettsiae were detected in the sampled yaks. The overall prevalence of spotted fever group rickettsiae was 46·5%, with a significant difference between females (68·3%) and males (9·09%). Age was also identified as a significant factor influencing infection rates. Furthermore, sequencing analysis revealed that the obtained rickettsial sequences shared 99·04-100% nucleotide identity with <i>Rickettsia raoultii</i>, a species endemic to Qinghai, China. Phylogenetic analysis based on the <i>ompA</i> and <i>gltA</i> genes confirmed that these sequences clustered within the <i>R. raoultii</i> clade. This study demonstrates a high prevalence of <i>R. raoultii</i> infection in yaks from Qinghai. Consequently, the implementation of preventive and therapeutic measures for yaks is recommended to mitigate the risk of transmission. This study did not collect tick samples simultaneously, so the transmission vector cannot be identified. Additionally, uneven sample distribution across some age groups may affect the representativeness of the results.