Detection of replicative deformed wing virus (DWV) in the European hornet (Vespa crabro, L.) and the yellow-legged hornet (Vespa velutina, Lepelieter).

Within the research network Stopvelutina in October 2016, in a destroyed nest of Vespa crabro L., some queens showed deformed wings. The abdomen and the thorax of asymptomatic and symptomatic specimens were analysed for Deformed Wing Virus (DWV) and they were found positive for the virus by strand specific RT-PCR, indicating active replication. This finding confirms the ability of the virus to infect not only bees but also wasps, suggesting a possible trans-mission route by ingestion of infected honey bees by hornet’s larva. In order to investigate the possible infection of DWV in Vespa velutina, in 2017 hornets were sampled in front of the apiaries in May (early season) and July (mid-season), while newly-emerged males and females were sampled in November (late season). By strand specific RT-PCR replicative DWV was detected in workers sampled in July and in the newly-emerged specimens collected in October, proving that DWV can infect the alien Asian hornet. This is the first report of DWV infection in V. velutina. The presence of replicating DWV with overt infection in V. velutina leads to hypothesize a possible role of DWV in a natural re-equilibrium of the relationship between prey and the alien predator, or even the development of a system to protect healthy honey bee’s colonies through the use of naturally highly infected bee colonies as possible prey for the predator.