Alterations in the salivary gland microbiota of Haemaphysalis longicornis during tick-to-host transmission of severe fever with thrombocytopenia syndrome virus.

Haemaphysalis longicornis serves as the primary tick vector for severe fever with thrombocytopenia syndrome virus (SFTSV), the etiological agent responsible for severe fever with thrombocytopenia syndrome (SFTS). Understanding alterations in tick salivary gland microbiota during SFTSV transmission to vertebrate hosts is essential for developing novel control strategies. However, microbial shifts in tick salivary glands during pathogen transmission to hosts have not been reported for any tick-borne pathogens. In this study, SFTSV transmission from H. longicornis to vertebrate hosts was confirmed using a tick-rabbit transmission model. Salivary gland microbiota profiling via 16S rRNA gene sequencing identified significant changes in bacterial composition associated with viral transmission. The relative abundance of three genera ( Serratia, Bifidobacterium, and Akkermansia) increased, whereas five genera (Flavobacterium, Staphylococcus, Enhydrobacter, Massilia, and Stenotrophomonas) decreased. Correlation network analysis revealed a negative association between Akkermansia and Flavobacterium. These findings demonstrated that SFTSV transmission alters the salivary gland microbiota of H. longicornis, providing insights for future functional studies and the development of targeted strategies for SFTS control.