> Allen Dick and I have spent a few nights talking intensely on the issue
of how AFB might cycle through its life in a colony even though no visible
signs of disease can be seen in the brood nest.

That's the truth.  I think this is really a crucial question.

> The conversation about AFB cycling and no disease symptoms usually comes
up when we are talking about antibiotic resistance, because Allen questions
how resistance could possibly have evolved as a consequence of selection
from continued antibiotic use, when during antibiotic use you never see the
disease, and presumably, no generations of AFB pass.

I realise that this is a rather questionable assumption, but a useful one.
In the real world, no medication regimen is ever 100% on-dose and on-time.
With hygienic behavior, there are degrees of performance and the time lag
between infection and detection can vary considerably.  Other controls that
seem simple and obvious, like destruction of infected colonies and burning
the hives, can also have some unexpected complications and unanticiped
effects on the evolution of AFB as well.

> I have seen things over the last few months that make me think it is not
so crazy that AFB does cycle below levels where beekeepers can spot it.

I don't think that this has ever been in doubt.  To me one important
question is under what circumstances can this occur and what the mechanisms
are -- and the degree of spore formation and spread, compared to the
natural deterioration and elimination of spores in a colony.

> I am helping out on a big experiment looking into different ways to
detect AFB spores from colonies, and it is from this I am seeing things
about AFB I did not know about.

It is good to know that the assumptions are being tested.  An understanding
of the mechanisms of the various varieties of AFB is going to be very
important in determining the best approaches to AFB management in the
future.  This applies whether drugs, AFB resistant bees, depopulation,
burning, radiation, comb renewal or chemical disinfection are used, alone
or in combination.  Each of these methods applies differents pressures to
the survival of AFB and knowing how AFB lives and functions at sub-visible
levels will help us predict the potential failures and weaknesses of each
approach and tell us how to combine these very useful and potent controls
for optimal and long-lasting results.

> As many of you know, spores are not only found on ropey larvae or scale,
but they are also in honey, on wooden ware and on adult bees.  For years
people have noticed that even if you find spores in colonies, you might not
actually see any diseased larvae.  Where do these spores come from?

And how quickly do they dissipate?  What is the half-life of an average AFB
spore in a honey bee colony under varying conditions?

> ... Another theory is that larvae are continually being infected with the
disease and workers are ejecting them before we can see them, but not soon
enough to prevent a cloud of spores in the colonies <snip> I have noticed
the following remarkable things:
>
> 1) Larvae that have recently died from AFB are sometimes still white,
hold their shape and do not rope but are packed with spores (I only new
this because I grew some larvae out that were slightly funny looking... I
would not have picked them out of the line-up otherwise)

Were they "packed with spores" or with a vegetative stage?  This is one of
the crucial questions that has had me wondering.  If the larvae are thrown
out while the infection was still vegetative, would not the effect be
different, particularly in a medicated environment?  At what point do the
spores form?  Is dessication necessary, or what are the triggers?  It is
the sporulation that is the persistant and most potent factor in AFB
transmission as far as I know.

> 2) Many larvae that are inoculated with spores are ejected before they
show signs of symptoms.

While containing new spores, or vegetative growth?

> 3) Scales can form within a week of first observing ropey larvae

I am presuming you mean hard scales? That seems to me to require drier
conditions than I would expect in a normal brood area.

> 4) Following a flush of infected larvae from the inoculation there is
often a one week period where no symptoms can be seen, followed by a second
week were symptoms are ambiguous, followed by a 3rd week (which hasn't
actually happened yet, but I am expecting it) with diagnostic symptoms.

I am assuming that this is in the absence of any medication?

> Although we are waiting for a slow time to grow out the samples, I expect
there will be many times we go to the colonies and do not see clear AFB
symptoms but there are many spores floating around.

I think we are all agreed here.  The real questions are under what
conditions the spore load increases and under what conditons the spore load
diminishes, and what the normal rate of attrition is for existing spores if
there are no new ones being added to the colony.  Theoretically, at least,
the control measures listed above, and perhaps others, help a colony resist
formation of new spores while the old spores are germinating and either
failing to reproduce and/or physically being removed from the colony over
time.

> Allen, I hope I have not misrepresented you.

Nope, I think that is pretty close.  Of course there are too many
subtleties to cover all the questions and their supplementary issues in a
few paragraphs, but I think you covered one aspect of the question well
here.

I am also sure we all have, and will continue to have, slightly different
understandings of the various factors and priorities involved, and IMO that
is a good thing.  Through dialogue, questioning and observation we expand
our factual base, and reduce the assumptions we make.

I'm happy to hear that some of the assumptions are being tested. IMO, AFB
and its control is one of those topics where there is much more speculation
and assumption than actual knowledge.  Moreover, there may be more
variables than we have considered, and even some unique events that are
impossible to study.

> If I have, know that it is because I did not understand you properly,
likely because you had given me to much mead that particular night.  I
don't want to get into the evolution of antibiotic resistance, beacuse you
long ago showed me how complicated those questions are, but I thought you
all might appreciate the observations.

I sure do.

allen