In the past centuries, viruses have benefited from globalization to spread across the globe, infecting new host species and populations. A growing number of viruses have been documented in the western honey bee, Apis mellifera. Several of these contribute significantly to honey bee colony losses. This review synthetizes the knowledge of the diversity and distribution of honey-bee-infecting viruses, including recent data from high-throughput sequencing (HTS). After presenting the diversity of viruses and their corresponding symptoms, we surveyed the scientific literature for the prevalence of these pathogens across the globe. The geographical distribution shows that the most prevalent viruses (deformed wing virus, sacbrood virus, black queen cell virus and acute paralysis complex) are also the most widely distributed. We discuss the ecological drivers that influence the distribution of these pathogens in worldwide honey bee populations. Besides the natural transmission routes and the resulting temporal dynamics, global trade contributes to their dissemination. As recent evidence shows that these viruses are often multihost pathogens, their spread is a risk for both the beekeeping industry and the pollination services provided by managed and wild pollinators.

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.

The parasitic mite Varroa destructor is a serious threat for western honey bee colonies and beekeepers are compelled to control it to keep their colonies healthy. Yet, by controlling varroa no resistance to the parasite can evolve. As a trial, honey bee colonies have been left untreated in isolated locations to allow development of resistance or tolerance to the mite. These colonies developed an ability to live without control measures against varroa, although the traits responsible for this resistance or tolerance are still unclear. Two of these resistant populations have been studied to test the involvement of specific varroa mite targeted hygienic behaviour varroa sensitive hygiene (VSH) in the acquired resistance. Individual mites were manually introduced into just capped brood cells, after which the brood combs were placed in colonies of the two resistant populations and in control colonies in which varroa had always been controlled. We followed the development of the mites, including possible removals. We found that VSH had increased strongly in one of the selections, up to 40% of the infested cells with mites and pupae were removed, but it had decreased in the other selection, compared to the control colonies. Further we could not conclude from our data that VSH only or preferentially targets reproducing mites, leaving non-reproducing mites undisturbed. The different VSH responses between the two selected resistant honey bee populations lead to conclude that more than one mechanism of resistance may evolve in response to the selection pressure by varroa mites. La higiene sensible a Varroa contribuye a la resistencia a varroa naturalmente seleccionada en abejas melíferas El ácaro parásito Varroa destructor es una seria amenaza para las colonias occidentales de abejas melíferas y los apicultores se ven obligados a controlarlo para mantener sus colonias sanas. Sin embargo, al controlar la varroa no puede evolucionar hacia ninguna resistencia al parásito. Como ensayo, se han dejado sin tratar colonias de abejas en lugares aislados para permitir el desarrollo de resistencia o tolerancia al ácaro. Estas colonias desarrollaron una capacidad para vivir sin medidas de control contra la varroa, aunque los rasgos responsables de esta resistencia o tolerancia aún no están claros. Dos de estas poblaciones resistentes han sido estudiadas para probar la implicació n de una varroa específica con un comportamiento higiénico específico sensible a varroa (VSH por sus siglas en inglés) en la resistencia adquirida. Los ácaros individuales se introdujeron manualmente en celdas de cría recién operculadas, después de lo cual los cuadros de cría se colocaron en colonias de las dos poblaciones resistentes y en colonias de control en las que la varroa siempre se había controlado. Seguimos el desarrollo de los ácaros, incluyendo posibles retiradas. Se encontró que el carácter VSH había aumentado fuertemente en una de las seleccionadas, hasta el 40% de las celdas infestadas con ácaros y pupas fueron eliminadas, pero había disminuido e...