Molecular Detection and Identification of Bacterial Pathogens in Qinghai Province, China

As a core pastoral region of the Qinghai-Tibet Plateau, Qinghai Province faces substantial threats to livestock production from tick-borne diseases. This study aimed to investigate the prevalence of six bacterial pathogens in dominant tick species from Qinghai Province, to provide baseline epidemiological data for local tick-borne disease surveillance. A total of 1025 questing ticks were collected from key pastoral regions of Qinghai Province during April to May in 2024 and 2025. All ticks were morphologically identified as belonging to 1 family (Ixodidae), 2 genera, and 4 species. <i>Dermacentor nuttalli</i> was the dominant species with a relative dominance of 66.83% (685/1025, 95% CI: 63.92-69.61%), followed by <i>Haemaphysalis qinghaiensis</i> at 30.83% (316/1025, 95% CI: 28.11-33.69%), <i>Dermacentor silvarum</i> at 1.95% (20/1025, 95% CI: 1.27-2.98%), and <i>Dermacentor niveus</i> at 0.39% (4/1025, 95% CI: 0.15-1.01%). PCR detection was performed for six target pathogens, with an overall <i>Brucella</i> spp. DNA detection rate of 0.78% (8/1025, 95% CI: 0.40-1.53%) and an overall <i>Rickettsia</i> spp. detection rate of 16.29% (167/1025, 95% CI: 14.16-18.67%). Statistical analysis showed that the prevalence of <i>Brucella</i> spp. and <i>Rickettsia</i> spp. differed significantly between the two dominant tick species (Fisher's exact test/χ² test, all <i>p</i> < 0.001). No <i>Brucella</i> or <i>Rickettsia</i> pathogens were detected in <i>D. silvarum</i> and <i>D. niveus.</i> Notably, detection of <i>Brucella</i> spp. DNA does not confirm the presence of viable bacteria or tick vector competence. This study fills the regional data gap of tick-borne pathogens in Qinghai, and provides reference for the prevention and control of local tick-borne zoonotic diseases.