Molecular evidence of the spotted fever group Rickettsiae in ticks from Yunnan Province, Southwest China

Ixodid ticks transmit many obligate intracellular Rickettsial species. Several previous studies have identified Rickettsia species in the northeastern and southern part of China, but few reports on the prevalence of infection of spotted fever group Rickettsiae (SFGR) in ticks in southwest China are available. Here, we investigated SFGR in 394 adult ticks of five species including Dermacentor nuttalli, Dermacentor silvarum, Haemaphysalis longicornis, Ixodes sinensis and Ixodes persulcatus, collected in the border region between China and Burma in Yunnan Province. PCR was used to detect the presence of the citrate synthase (gltA) gene of Rickettsia species. SFGR was found in 12.1% (15/124) of I. persulcatus ticks, which was significantly higher than the 7.2% (7/97) positive D. nuttalli, 5.4% (3/56) D. silvarum, 5.6% (4/72) H. longicornis and 4.4 (2/45) I. sinensis. A portion of the gltA and ompA gene data subjected to phylogenetic analysis revealed that the detected SFGR clustered into two species, Rickettsia raoultii and the new Rickettsia species Candidatus Rickettsia jingxinensis. Detection of both Rickettsia spp. in this region indicates a potential public health threat posed by SFGR infection in Yunnan Province.