>On Sep 21, 2013, at 8:56 AM, randy oliver <[log in to unmask]>

>  wrote:
>

Hey Pete, I thought that you were going to erase our email addresses from
your posts : )

>Genersch writes:
> > While N. apis, the ‘classical’ Nosema-species infecting A. mellifera, is
> considered a rather benign honey bee pathogen rarely causing any colony
> losses


This was the opinion of Ingemar Fries, and is widely quoted.  However, in
both Australia and North America N apis was at times clearly a problem, and
any number of field trials found great benefit to making efforts to control
it.  With N apis, any time that over half the bees in the hive became
infected, there would be observable loss of colony strength, possibly
leading to collapse.



> >N. ceranae has been associated with or identified as causative agent of
> colony losses in some geographical regions leading to the assumption that
> N. ceranae is more virulent than N. apis (Higes et al., 2007).
>

This may have been a premature assumption.  Higes later explained to me
that there were at least two additional factor in the Spanish
collapses--the those beekeeper rarely replaced queens, and that the
colonies were often under nutritional stress.  I also strongly suspect that
viruses (other than DWV may have been involved).  The soon-to-be released
Monsanto trial data may help to answer this question.

>
> > However, reports on the virulence of N. ceranae for individual bees and
> for bee colonies are contradictory and several studies indicate an
> influence of climatic parameters like temperature on the virulence and
> assertiveness of N. ceranae
>

"Contradictory" is correct!

>
> > The interpretation of the results of all these studies comparing the
> epidemiology and virulence of N. ceranae and N. apis rely on the correct
> identification of and differentiation between these two microsporidian
> species infecting A. mellifera.
>

And we recently found out that the primers used by most labs for ID of the
nosema species underestimated the presence of N apis.

>
> > in Germany, involving about 220 honeybee colonies and a total of 1,997
> samples collected from these colonies each spring and autumn and analyzed
> via species-specific PCR-restriction fragment length polymorphism (RFLP),
> are described. Statistical analysis of the data revealed no relation
> between colony mortality and detectable levels of infection with N. ceranae
> or N. apis.


As I posted a few days ago.  The levels of infection in those colonies was
so low that no negative effects would have been expected.  Note also that
they only sampled in fall and spring.  In my own colonies, N ceranae
doesn't begin to build until after fall, and then disappears in late
spring.  So without winter sampling, they would likely have been unable to
detect any correlation.

However, my own data from Calif shows only a weak correlation between loss
of winter strength and the prevalence of N ceranae.

>
> > Although the Hawaiian honeybees have the highest known prevalence of N.
> ceranae in the world, with average number of spores been 2.7 million per
> bee, no acute Nosema related problems i.e. large-scale colony deaths, have
> been reported by Hawaiian beekeepers.
>

To further quote from the same paper:
"The average spore count of 2.7 million per bee in
Hawaii, which is typical for many studies, is well below the
10s-100s of millions detected from in-hive bees from CCD
colonies (Cox-Foster et al., 2007) or 10s of millions in
those that died in Spain (Higes et al., 2008)."

I've spoken with the Hawaiian queen producers.  One of them has long
considered nosema to be a problem [likely apis], and when I did spore
counts for another, we often found extremely high levels, and it appeared
to them that it may have been associated with lack of buildup.  On the Big
Island, and colony weakened by either varroa/virus or nosema in recent
years was rapidly invaded by Small Hive Beetle, which would mask that the
original problem was due to some other parasite.

Pete, this is a great discussion!  We are in the process of learning about
N ceranae.  There are few conclusions that can be legitimately made at this
date.

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

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