In 2007, American beekeepers lost 30 percent of their approximately 2.4 million managed colonies to diseases, according to the U.S Department of Agriculture. The deaths are linked to a recent surge in diseases and pests, like parasitic mites, and to Colony Collapse Disorder, which leads bees to abandon their hives.
In a number of recent analyses, commercial apiaries have been shown to harbor a plethora of viruses and diseases simultaneously. Viruses are small entities that carry genomic information in the form of DNA or RNA and, with a few exceptions, are encapsulated by a shell of protein(s). The nucleic-acid:protein form is called a virion. In many cases, virions are located within higher structures, usually enveloped by a membrane or embedded within a proteinaceous matrix.
Assorted factors have been implicated in the reduced capability of bees to survive in recent years, including the dearth of resources and poor nutrition which are a key factor in bee and colony loss. Every doctor prescribes exercise and a healthy diet as preventive measures to disease. And every beekeeper knows that good forage over time is the ultimate cure. Bees, as a community, overcome almost all diseases easily when the weather is favorable and wild flowers bloom prolifically. However, in recent years, large scale monoculture has resulted in a lack of natural weeds, and all too often pesticide-laden crop forage.
The relatively restricted genetic pool from which bee queens are bred enables diseases to become more ubiquitous and have increased impact. Compounded by increased global travel, diseases spread quickly and virulent strains of viruses or other pathogens take advantage of this situation. Indeed, selection of traits for resistance is not naturally favored because of artificial selection for other commercially important bee traits, such as honey production and docile management. In some countries, feral bee populations are quickly diminishing and sometimes disappearing, thus making genetic pool further restricted to drones from managed colonies.
Global Honey Bee Viral Landscape Altered by a Parasitic Mite
Study Published in Science, June 8, 2012
Vol. 336 no. 6086 pp. 1304-1306
DOI: 10.1126/science.1220941
Authors: Stephen J. Martin1,*, Andrea C. Highfield2, Laura Brettell1, Ethel M. Villalobos3, Giles E. Budge4, Michelle Powell4, Scott Nikaido3, Declan C. Schroeder2,*
+ Author Affiliations
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
- The Marine Biological Association of the United Kingdom, Citadel Hill, Plymouth PL1 2PB, UK.
- Department of Plant and Environmental Protection Sciences, University of Hawaii at Manoa, Hawaii, USA.
- The Food and Environment Research Agency, Sand Hutton, York YO41 1LZ, UK.
Abstract
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 million-fold 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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