Emerging diseases are among the greatest threats to honey bees. Unfortunately, where and when an emerging disease will appear are almost impossible to predict. The arrival of the parasitic Varroa mite into the Hawaiian honey bee population allowed us to investigate changes in the prevalence, load, and strain diversity of honey bee viruses. The mite increased the prevalence of a single viral species, deformed wing virus (DWV), from ~10 to 100% within honey bee populations, which was accompanied by a millionfold increase in viral titer and a massive reduction in DWV diversity, leading to the predominance of a single DWV strain. Therefore, the global spread of Varroa has selected DWV variants that have emerged to allow it to become one of the most widely distributed and contagious insect viruses on the planet.

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SummaryHoney bee virus research is an enormously broad area, ranging from subcellular molecular biology through physiology and behaviour, to individual and colony-level symptoms, transmission and epidemiology. The research methods used in virology are therefore equally diverse.This article covers those methods that are very particular to virological research in bees, with numerous cross-referrals to other BEEBOOK papers on more general methods, used in virology as well as other research. At the root of these methods is the realization that viruses at their most primary level inhabit a molecular, subcellular world, which they manipulate and interact with, to produce all higher order phenomena associated with virus infection and disease. Secondly, that viruses operate in an exponential world, while the host operates in a linear world and that much of the understanding and management of viruses hinges on reconciling these fundamental mathematical differences between virus and host. The article concentrates heavily on virus propagation and methods for detection, with minor excursions into surveying, sampling management and background information on the many viruses found in bees. Métodos estándar para la investigación de virus en Apis mellifera ResumenLa investigación de los virus de la abeja de la miel es un área sumamente amplia, que abarca desde la biología molecular subcelular hasta la fisiología y el comportamiento, desde síntomas al nivel de individuo hasta al nivel de la colmena, transmisión y epidemiología. Los métodos de investigación en virología son, por tanto, diversos. Este artículo incluye aquellos métodos específicos de la investigación virológica en las abejas, con numerosas referencias cruzadas con otros artículos del BEEBOOK y otros más generales, usados tanto en virología como en otras disciplinas. La base de estos métodos es la comprensión de los virus en su nivel primario de hábitat molecular, ambiente subcelular, que manipulan y con el que interactúan, para producir otros fenómenos de orden superior asociados a la infección del virus y la enfermedad. En segundo lugar, estos virus actúan en un mundo exponencial, mientras que los hospedadores actúan en un mundo lineal y gran parte del entendimiento y manejo de los virus depende de los fundamentos matemáticos de las diferencias entre el virus y el hospedador. El artículo se centra principalmente en la propagación de virus y en los métodos para su detección, con inclusiones menores en su estudio, el manejo del muestreo y la información general sobre los numerosos virus que se encuentran en las abejas.

Reports of honey bee population decline has spurred many national efforts to understand the extent of the problem and to identify causative or associated factors. However, our collective understanding of the factors has been hampered by a lack of joined up trans-national effort. Moreover, the impacts of beekeeper knowledge and beekeeping management practices have often been overlooked, despite honey bees being a managed pollinator. Here, we established a standardised active monitoring network for 5 798 apiaries over two consecutive years to quantify honey bee colony mortality across 17 European countries. Our data demonstrate that overwinter losses ranged between 2% and 32%, and that high summer losses were likely to follow high winter losses. Multivariate Poisson regression models revealed that hobbyist beekeepers with small apiaries and little experience in beekeeping had double the winter mortality rate when compared to professional beekeepers. Furthermore, honey bees kept by professional beekeepers never showed signs of disease, unlike apiaries from hobbyist beekeepers that had symptoms of bacterial infection and heavy Varroa infestation. Our data highlight beekeeper background and apicultural practices as major drivers of honey bee colony losses. The benefits of conducting trans-national monitoring schemes and improving beekeeper training are discussed.