Bee Viruses: Routes of Infection in Hymenoptera

Abstract

Numerous studies have recently reported on the discovery of bee viruses in different arthropod species and their possible transmission routes, vastly increasing our understanding of these viruses and their distribution. Here, we review the current literature on the recent advances in understanding the transmission of viruses, both on the presence of bee viruses in Apis and non-Apis bee species and on the discovery of previously unknown bee viruses. The natural transmission of bee viruses will be discussed among different bee species and other insects. Finally, the research potential of in vivo (host organisms) and in vitro (cell lines) serial passages of bee viruses is discussed, from the perspective of the host-virus landscape changes and potential transmission routes for emerging bee virus infections.

Keywords: Apis; artificial infection; bee; natural infection; non-Apis; transmission; virus.

FIGURE 1

Graphical representation of the natural routes of inter- and intra-species transmission of viruses found in Hymenoptera. Transmission routes that are more likely to occur are represented by solid arrows, transmission routes that are less likely or less frequently observed are represented by dotted arrows. The most likely route of inter-species transmission is through the use of shared flowers (Singh et al., 2010; Alger et al., 2019), depicted in the middle surrounded by a red dotted line. Inter- and intra-species transmission in non-social bees, depicted on the left side can occur through contact at nest aggregations or the reuse of virus-contaminated old nest cavities (Krunicì and Stanisavljevicì, 2006). In social bees, depicted on the right side, the main intra-species transmission route is likely, via intense contact in the nest. Social behavior such as trophallaxis and body contact could mediate transmission (Amiri et al., 2014, ; Chen et al., 2014; Coulon et al., 2018 and others, see main text). Further intra-species transmission can also occur via vectors, for honey bees this is a very important transmission route for several viruses, mediated by V. destructor (Santillán-Galicia et al., 2010; Möckel et al., 2011; Gisder et al., 2018; Posada-Florez et al., 2019; Ryabov et al., 2019 and others, see main text). Intra-and inter-species transmission via vectors, other than V. destructor [e.g., the small hive beetle, phorid flies (Eyer et al., 2009; Core et al., 2012; Menail et al., 2016)] are less frequent. Robbing and drifting are also two potential routes of inter- and intra-species transmission, respectively, described in social bees. Yet their role in virus transmission is likely to be minor compared to other transmission routes. Lastly, social parasitism creates a high contact between individuals from different species and hence is likely to facilitate virus transmission, in social bees. Inter-species transmission in Vespidae sp. can occur through feeding on infected Hymenoptera, or other insects that are infected with a virus or contain the virus on their exterior (Loope et al., 2019). Another potential transmission route for wasps is the use of shared contaminated flowers (Mordecai et al., 2016b). Intra-species transmission in social Vespidae sp. is also likely to occur via intense contact within the nest.