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

Haemaphysalis longicornis is the predominant tick vector of severe fever with thrombocytopenia syndrome virus (SFTSV), the causative agent responsible for severe fever with thrombocytopenia syndrome (SFTS). Defining the changes in tick salivary gland microbiome in the context of SFTSV transmission to the vertebrate host is essential for the development of new SFTS control strategies. However, how the tick salivary gland microbiome shifts in response to the tick-to-host transmission of pathogens has not been reported for any tick-borne pathogens. Here, after confirming the occurring of tick-to-host transmission of SFTSV in a tick-rabbit transmission model, 16S rRNA gene sequencing was used to sequence salivary glands from H. longicornis, revealing changes in the relative abundance of eight genera upon viral transmission. The relative abundance of three genera (Serratia, Bifidobacterium, and Akkermansia) increased, and another five genera (Flavobacterium, Staphylococcus, Enhydrobacter, Massilia, and Stenotrophomonas) decreased. Correlation network analyses reveal that Akkermansia was negatively correlated with Flavobacterium. Taken together, our findings highlight the changes in bacterial composition that occur in the salivary glands of H. longicornis in response to tick-to-host SFTSV transmission, and these results may benefit future functional studies and aid the development of new strategies for the control of SFTS.