May I offer the following study with regard to this thread: Parasites in
bloom: flowers aid dispersal
and transmission of pollinator parasites within and between bee species,
http://dx.doi.org/10.1098/rspb.2015.1371  It is open access at Researchgate.

The study clearly demonstrates how incredibly quickly and efficiently
pathogens are transmitted from bee to bee, and thus colony to colony, via
exposure at flowers.

It very much makes me question the benefit of sterilizing combs, other than
in the case of AFB.

As a practical example, last year we created an isolated "sick yard"
consisting of those colonies too sick or weak to go to almond pollination
(about 45 hives), intending to go back and treat them all with OTC and
fumagillin.  But we never got around to it.  When we returned two months
later, roughly 2/3rds of the colonies had fully recovered.  We put the
deadouts on them as honey supers (still zero treatments).  All the colonies
continued to thrive and produced nice honey crops.

N. ceranae is endemic in my operation.  But as pointed out in meticulous
studies by White in the early 1900's, adding supers full of spores to
healthy colonies does not necessarily initiate a nosema infection in the
recipient colony.

My points are that the honey bee colony, given good nutrition, has an
innate capacity to purge a pathogen epidemic, other than in the case of
AFB, which leaves a persistent spore. All colonies are exposed to every
pathogen in the surrounding community by horizontal transmission via flower
visits.  Even the insult of adding "dirty" supers from non-AFB deadouts
does not (at least in my area) appear to initiate further disease.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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