Detection of spotted fever group Rickettsia in Haemaphysalis longicornis from Hebei Province, China.

DNA samples from 737 tick pools, representing 6,850 Haemaphysalis longicornis and 51 Dermacentor nuttalli collected from Hebei Province, China, were analyzed by polymerase chain reaction (PCR) for the presence of spotted fever group Rickettsia. Fifty (6.9%) of 724 H. longicornis in the tick pool were positive, but no positive samples were found in 13 D. nuttalli. Sequence analysis of the partial outer membrane protein A (ompA) genes from the 10 positive samples showed 97.4-99.8% identity, but were different from the homologous sequence of Rickettsia previously deposited in GenBank. Phylogenetic analysis of ompA genes indicated that the Rickettsia detected in this study belonged to a novel haplotype, and formed a clade distinct from Rickettsia heilongjiangii, Rickettsia sibirica, and Rickettsia hulinii in China. The new strain, named Candidatus Rickettsia hebeiii, appears to represent a distinct lineage and could constitute a new species with a minimum prevalence of about 0.7% in H. longicornis from Hebei Province, China.