Molecular detection of pathogens in ticks and rodents, Northeast and Middle-east China

Background In recent years, tick-borne and rodent-borne pathogens have increasingly threatened humans and domestic animals. However, the types and distribution of pathogens they carry remain poorly understood in China. Methods In this study, we collected a total of 1004 Haemaphysalis longicornis ticks (503 adults and 501 nymphs), divided into 670 groups, from Liaoning Province in northeastern China and Anhui Province in middle-eastern China, along with 42 Spermophilus dauricus from Heilongjiang Province in northeastern China. Morphological analysis and cytochrome oxidase I ( COI ) sequencing were used to identify tick and rodent species. Using nested PCR, all samples were first tested for severe fever with thrombocytopenia syndrome virus (SFTSV) and the bacterial 16S rRNA gene, followed by detection of the corresponding genus-specific genes. Samples were tested for Rickettsia 16S rRNA/ rrs , 17kDa , gltA , ompA , ompB , and sca4 genes; for Coxiella 16S rRNA, groEL , and rpoB genes; and for Legionella groEL and mip genes. Results Spotted fever group Rickettsia spp. (SFGR) were identified in a total of 14 tick groups: Candidatus Rickettsia jingxinensis (12/594) from Liaoning and Rickettsia heilongjiangensis (2/76) from Anhui. Four of the 14 groups were co-infected with Coxiella -like endosymbionts (CLE). Notably, Legionella pneumophila was detected in 2 of 42 S. dauricus from Heilongjiang, with genetic similarity to the OLDA strain from a U.S. patient exceeding 99.8% for 16S rRNA, groEL , and mip genes, confirming the high pathogenic potential of these strains in humans. Conclusions Our findings suggest that local residents should be cautious about potential infections from these two SFGR species, and we recommend further surveillance and investigation of H. longicornis and S. dauricu s as pathogen carriers.