Honeybee pathogens in Vespa orientalis: investigation on samples from North-Eastern Italy, Malta and Cyprus.

The oriental hornet (Vespa orientalis Linnaeus, 1771) is an hymenoptera of the family Vespidae, native to southwestern Asia, India, the Middle East, northeastern Africa and the southeastern Mediterranean area. Due to the increase in global goods traffic and climate change, V. orientalis has expanded its range, colonizing several European countries (Spainnia, France and several island of Greece), Messico, Chile and China. Although it is already endemic in some regions of Southern and Central Italy, in recent years V. orientalis has been reported in other regions of Italy, including Friuli Venezia Giulia, where it is considered as a "neo-invasive" species. Because of its negative impact on health of Apis mellifera colonies, not only due to direct predation but also because it could act as a potential vector of bee pathogens, monitoring plans have been implemented to mitigate its spread across Italy. Between August and October 2024, 35 specimens of V. orientalis from Friuli Venezia Giulia region (province of Trieste), 8 specimens from Malta (Mosta) and 8 from Cyprus (Famagusta) were captured. For each specimen, molecular analysis were carried out for the detection of the most common pathogens of A. mellifera: Nosema apis/Nosema ceranae; Lotmaria passim; Crithidia mellificae; bee filamentous virus (AmFV), acute paralysis virus (ABPV), black queen cell virus (BQCV), chronic paralysis virus (CBPV), deformed wing virus (DWV), sacbrood virus (SBV), israeli acute paralysis virus (IAPV), Kashmir bee virus (KBV).The presence of replicative form of DWV virus was also investigated. The analysis revelaed N. ceranae only in one specimen from Malta; all the samples were negative for N. apis, L. passim, C. mellificae and the viruses KBV and IAPV. DVW and BQCV were the most frequently detected viruses across all sampling sites, followed by ABPV, SBV, and CBPV. AmFV virus was detected in all specimens from Cyprus, in 7/8 specimens from Malta, and in 10/35 specimens from Italy. Moreover, replicative form of DWV were detected in several specimens. This study confirmed the potential role of V. orientalis as a vector of A. mellifera pathogens in three different hornet populations, from areas where it is both endemic and neo-invasive. The data obtained not only confirmed the co-infection of some known honey bee viruses in V. orientalis, but also demonstrated, for the first time, the presence of AmFV in this hornet species. Furthermore, the presence of replicative form of the DWV virus in some samples suggests that this hornet may act not only as a mechanical but also as a biological vector, highlighting the need to implement monitoring, control and, where it is possible, eradication actions to slow its spread and contain its expansion, especially in recently introduced areas. This is crucial to ensure the health of honey bees, the well-being of the hive, and consequently the protection of beekeeping industry.