Rethinking spillover risks: first description of the Vespa orientalis gut microbiome and its impact on honeybee and human health

Vespa orientalis (Oriental hornet) is expanding its range worldwide, raising concerns about its predatory impact on honey bees and potential health risks to humans. This study provides the first comprehensive description of the V. orientalis gut microbiome, explores how diet and location influence microbial composition, and bee pathogens reservoir. Adult hornets with different feeding behaviors were sampled from four urban and natural sites in Malta. 16S rRNA gene sequencing revealed a gut microbiota dominated by Firmicutes and Proteobacteria, with key genera including Carnimonas , Arsenophonus , and Rosenbergiella. Significant compositional shifts were observed in relation to diet and sampling location, suggesting that environment and diet significantly shape the hornet gut community. Moreover, detection of certain honey bee-associated microbes, such as Gilliamella and Snodgrassella , points to potential microbial exchange between predator and prey. Quantitative PCR targeting bee and human pathogens detected high prevalence rates of Nosema ceranae , Crithidia bombi , and Serratia , while Listeria , Salmonella , and other bee pathogens were absent. Our findings suggest V. orientalis may function more as a pathogen reservoir rather than a primary spillover vector and lays the groundwork for targeted management strategies to mitigate its impact on apiculture and broader ecosystem services.