Four new viruses of honey bees

Nosema spores There are numerous threats facing honey bee populations and the recent losses of honey bee colonies in the United States, Canada, and Europe is alarming. In the U.S., annual honey bee colony losses increased from 17–20% to 32% during the winter of 2006/07 with some operations losing 90% of their hives. Average annual losses have remained high, averaging 32% from 2007–2010. One factor contributing to increased losses is Colony Collapse Disorder (CCD), an unexplained loss of honey bee colonies fitting a defined set of criteria. While factors such as pesticide exposure, transportation stress, genetic diversity, and nutrition affect colony health, the most significant CCD-associated variable characterized to date is increased pathogen incidence. Although greater pathogen incidence correlates with CCD, the cause is unknown in part due to insufficient knowledge of the pathogenic and commensal organisms associated with honey bees.

To gain a more complete understanding of the spectrum of infectious agents and potential threats found in commercially managed migratory honey bee colonies, researchers conducted a 10-month investigation. Analysis incorporated a suite of molecular tools (custom microarray, polymerase chain reaction (PCR), quantitative PCR (qPCR) and deep sequencing) enabling rapid detection of the presence (or absence) of all previously identified honey bee pathogens as well as facilitating the detection of novel pathogens. This study provides a comprehensive temporal characterization of honey bee pathogens and offers a baseline for understanding current and emerging threats to this critical component of U.S. agriculture.

Discovery and characterization of four new viruses will facilitate future monitoring of bee colones. Temporal characterization of these and other microbes offers a more complete view of the possible microbe-microbe and microbe-environment interactions. Further studies examining any subtle or combinatorial effects of these novel microbes are required to understand their role in colony health.

 

Temporal Analysis of the Honey Bee Microbiome Reveals Four Novel Viruses and Seasonal Prevalence of Known Viruses, Nosema, and Crithidia. (2011) PLoS ONE 6(6): e20656. doi:10.1371/journal.pone.0020656
Honey bees (Apis mellifera) play a critical role in global food production as pollinators of numerous crops. Recently, honey bee populations in the United States, Canada, and Europe have suffered an unexplained increase in annual losses due to a phenomenon known as Colony Collapse Disorder (CCD). Epidemiological analysis of CCD is confounded by a relative dearth of bee pathogen field studies. To identify what constitutes an abnormal pathophysiological condition in a honey bee colony, it is critical to have characterized the spectrum of exogenous infectious agents in healthy hives over time. We conducted a prospective study of a large scale migratory bee keeping operation using high-frequency sampling paired with comprehensive molecular detection methods, including a custom microarray, qPCR, and ultra deep sequencing. We established seasonal incidence and abundance of known viruses, Nosema sp., Crithidia mellificae, and bacteria. Ultra deep sequence analysis further identified four novel RNA viruses, two of which were the most abundant observed components of the honey bee microbiome (~10^11 viruses per honey bee). Our results demonstrate episodic viral incidence and distinct pathogen patterns between summer and winter time-points. Peak infection of common honey bee viruses and Nosema occurred in the summer, whereas levels of the trypanosomatid Crithidia mellificae and Lake Sinai virus 2, a novel virus, peaked in January.

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About Alan Cann

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