I was glad for this interesting thread.  I have been thinking about some 
of these issues myself and I will pipe in on two issues:

1. Virulence and Hygienic Behaviour.  I liked Peter Edwards line of 
thinking regaring how lines of bees selected to hygienic behaviour would 
respond to a P. larvae strain that kills larvae early in life versus later 
in life.  I think his line of thinking is valuable and worth pursuing.  
The recent finding (which Peter Borst brought to BEE-Ls attention) 
demonstrates that fast killing strains kill about 80% of the larvae before 
the larvae are capped, compared to only about 30% with the strains most of 
us are use to.  Many of these fast killing strains were previously 
classified as P. pulvifaceans, although the current study observed that 
regular AFB-symptoms resulted from infection and not the powdery scale 
disease previously reported in the 1970s. 

Back to my point.  I wonder if hygienic behaviour is most useful with the 
slower-killing strains, as perhaps these infections are harder for a 
colony to find as the death is mostly post-capping (thus somewhat 
concealed under cappings).  An interesting and untested hypothesis.  This 
finding also leaves loose threads regarding how the speed at which a 
strain kills a larvae constitues virulence.  Which is more virulent, a 
fast or slow-killing strain?  I am interested in arguements which support 
either possibility and I am even more interested in an experimental test 
of this hypothesis.  


2. Testing for AFB from samples.  I work in a lab that has been taking 
bulk honey and adult bee samples from large (300-5000 colonies) operations 
in Western Canada with the hope of correlating the level of AFB in the 
samples with actual levels in the colonies.  This work is being done with 
the hope that it will help larger beekeepers and government inspection 
services who may be having difficulty inspecting a representative number 
of colonies.  Typically, from a very big operation (3000 colonies) a 
beekeeper would collect 70-120 honey samples during the duration of the 
honey harvest and we would correlate the number of spores back to the 
level of AFB found during inspection.  A summary of early results appears 
at this link:

http://www.apimondia.org/apiacta/articles/2006/pernal_1.pdf

A few interesting findings that relate to the current discussion are:
- We never found spores at any time in some beekeeping commercial 
beekeeping operations.  Some of these beekeepers stopped using antibiotic 
treatments and did not experience the reoccurance of AFB that Lloyd Spears 
experienced.  This test, consequently, may be useful in indicating when a 
beekeeper has a low risk of getting AFB.
- Over time, the level of tetracycline resistance increased even though 
oxytetracycline use was discontinued.  Consequently, oxytetracycline may 
not be useful in some beekeeping operations for a longer period of time 
than some might have expected.
- We observed a loose correlation between AFB prevalence and spore numbers 
in samples.  We are continuing to collect samples and analyse our data 
with hopes of finding stronger relationships.

Regards,
Adony

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