> When using a dry heat in the lab and using a higher number of spores, it
> was found that after 6 hours at a number of 3.6 X 1,000,000,000 there as
> no vegetative growth when cultured.  Raise the number to 6.5 X
> 1,000,000,000 then there were some growth when cultured...
 
It is not necessary to *kill* the spores.  Weakening them is sufficient
to provide protection.  AFB has a very short window of opportunity
(hours) to complete the job of infecting a larva.  If sufficient growth
does not ocur in the necessary time, the disease does not progress to kill
the larva. (I don't know if there is any residual effect of a non-lethal
AFB infection on an individual larva).
 
As I recall from a talk by Peng, the action of oxytetracycline on AFB is
not necessarily to totally inhibit the AFB germination but rather to
cripple it enough that it cannot grow enough in the short time it has to
kill the larva.
 
It takes a fairly large number of fully viable spores to cause a
successful and visible breakdown of AFB.  The real test is in the hive
IMO.  On a medium, in a lab,  the vegetation may not be meaningful --
unless the growth is timed and the result compared to the necessary rate
of growth to cause a successful infection in the real world.
 
After all, we inject ourselves with weakened strains of bacteria that are
known to cause deadly diseases to 'innoculate' ourselves against the very
same diseases.  We can infer from that that only viable and robust
examples of the type are a threat.
 
Allen
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