Metagenomic insights into pathogen diversity and public health risk of Haemaphysalis longicornis in Gansu Province of China.

The tick Haemaphysalis longicornis vectors numerous zoonotic pathogens, yet its pathogen diversity and associated spatial health risks are not fully characterized. To profile this vector, we performed metagenomic sequencing on 290 H. longicornis ticks across 29 sites in Gansu Province, China. We resolved 25 bacterial and one protozoan genera, with computational analyses revealing population-level distribution patterns and identifying environmental factors as key drivers of spatial variation.We detected marker genes associated with 12 pathogenic microorganisms. Alongside established threats (Rickettsia conorii, R. rickettsii, Coxiella burnetii, and Francisella novicida), we additionally identified several pathogens not previously reported in this vector, including Candidatus Bartonella merieuxii, Acinetobacter lwoffii, Shigella flexneri, Staphylococcus chromogenes, Moraxella atlantae, Pseudomonas alabamensis, and Trypanosoma spp. Furthermore, four potentially novel strains were identified within R. conorii, Escherichia coli, and Acinetobacter pseudolwoffii. Spatial Bayesian risk modeling localized the highest exposure risks to the Linxia, Zhangye, and Wuwei regions. The tick microbiome contained 31 clinically prioritized antibiotic resistance genes (ARGs), many of which co-localized with mobile genetic elements (MGEs). Overall, these findings reveal the diversity of pathogens associated with H. longicornis and their public health relevance, supporting future efforts in disease surveillance and risk assessment.