Hi all
Continuing the thread on bee viruses

[Excerpted for review purposes only]

> Beekeepers and extension personnel typically discover collapsing colonies in spring where attempts to a diagnosis them can only be made from those colonies exhibiting symptoms that are still alive. The virus types and levels found at that time of year may not represent an accurate picture of which pathogens are responsible for colony loss. Those viruses remaining in collapsing colonies could be opportunistic pathogens that thrive when the colonies immune responses are weakened by other factors. Virus prevalence analysis is commonly carried out on surviving colonies in spring in an attempt to help extension apiarists explain winter colony death as it might relate to fall pathogen composition, but the value of doing this is unclear. 

> Therefore, we compared virus prevalence, composition, and level between unhealthy (diseased) surviving colonies to healthy colonies sampled in fall both within a region (province of Manitoba) and to fall baseline levels for all provinces in Canada. Our results suggest that since unhealthy and healthy colonies had similar prevalence for all viruses within Manitoba and to most viruses across Canada, the identification of the mere presence or absence of bee viruses in colonies is not likely to be useful for assessing the impact of viruses on colonies or informing the development of successful management strategies for colonies.

> Of the potential viruses that infect bee colonies, DWV is emerging as one of the most serious and is frequently associated with severe winter loss of bees ... Our results suggest the impact of this virus is worthy of further study in Canada as it was ubiquitous, often occurred at high levels in healthy colonies sampled in fall, and was found at high levels in unhealthy colonies sampled in spring.

> The underlying causes of high rates of overwintering colony loss in the northern hemisphere remain unclear. ... The ability to manage bee colonies to prevent colony loss will likely depend developing the ability to directly or indirectly control bee virus epidemics. Increased knowledge of the relative impact of viruses and how to manage viral disease infections is critical. ... Our study suggests spring virus prevalence data from surviving colonies should not be used by extension personnel to explain colony loss in the absence of other supporting data. 

Desai, S. D., Kumar, S., & Currie, R. W. (2016). Occurrence, detection, and quantification of economically important viruses in healthy and unhealthy honey bee (Hymenoptera: Apidae) colonies in Canada. The Canadian Entomologist, 148(01), 22-35.

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