>
> >DeRisi's paper in PlOS One, 6/7/11 tracked N. ceranae and N. apis
> extensively throughout the season in several large migratory operations,
> and
> Figure 2 is of great interest
>

This study, when published, really got my attention.  When we first became
aware of N ceranae (DeRisi was the first to publish finding it in the
U.S.), infection levels appeared to be highest in spring, with some
beekeepers reporting severe infections midsummer.  Back then, I could
easily supply infected bees to other researchers at pretty much any time of
the year.

But that seasonal prevalence was contrary to a number of findings
elsewhere.  To my surprise, a number of researchers found that N ceranae
prevalence was similar to that of N apis--being mainly a cool-weather
phenomenon.  The recent publication by Chen (in Taiwan) and my own
year-long monitoring now suggest that N ceranae confirm this.

So now what puzzles me is why N ceranae seemed to be more of a summer
infection in the early stages of its invasion.  And why does the odd
beekeeper now find it to go epidemic in the summer?

I certainly do not know the answers.  Could the summer spikes be due to
reinoculation when the honey supers are placed on the hives?  Eischen found
that the wet combs were sometimes full of spores.  Or was there some other
factor, such as pesticide, miticide, or plant allelochemical stress?  Or
some other pathogen?

Note in the DeRisi study that two other intestinal parasites also spiked in
summer--crithidia and spirosplasma.  As did BQCV, which has long been
associated with N apis.

I find N ceranae to be one of the most difficult subjects in all of bee
research!

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

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