First report on the occurrence of Rickettsia slovaca and Rickettsia raoultii in Dermacentor silvarum in China

In an attempt to assess the potential risk of rickettsial infection after exposure to ticks in Xinjiang Uygur Autonomous Region of China, a total of 200 Dermacentor silvarum ticks collected in Xinyuan district were screened by polymerase chain reaction based on the outer membrane protein A gene.22 of the 200 specimens (11%) were found to be positive by PCR. Phylogenetic analysis of OmpA sequences identified two rickettsial species, Rickettsia raoultii (4.5%) and Rickettsia slovaca (6.5%).This study has reported the occurrence of Rickettsia raoultii and Rickettsia slovaca in Xinjiang Autonomous Region of China and suggests that Dermacentor silvarum could be involved in the transmission of rickettsial agents in China. Further studies on the characterization and culture of rickettsial species found in Dermacentor silvarum should be performed to further clarify this. Additionally, the screening of human specimens for rickettsial disease in this region will define the incidence of infection.Tick-transmitted diseases are a focus of increasing medical interest worldwide. Ticks are the main vectors and reservoirs of rickettsial pathogens responsible for spotted fever. Rickettsioses are among both the longest known and most recently recognized infectious diseases. The clinical features include fever, headache, eruption, and incidental eschar formation at the site of tick bites [1]. The etiological agents belonging to the genus Rickettsia are currently divided into two groups: the typhus group and the spotted fever group. The latter group includes an increasing number of newly identified species.In China, many spotted fever group (SFG) rickettsiae belong to R. sibirica, including 2 subspecies, i.e., R. sibirica sibirica, the agent of North Asian tick typhus detected in Dermacentor silvarum and D. sinicus in northern China, and R. sibirica mongolotimonae, the agent of lymphangitis-associated rickettsiosis isolated from Hyalomma asiaticum in Inner Mongolia [2,3]. Rickettsia hei