>But how can anyone assert that "AFB largely disappeared in recent years"

I should have said that compared to years ago, when U.S. beekeepers and bee
inspectors continually spoke about problems with AFB, when I ask them now,
few respond that they see much any more.  In many commercial discussions,
beekeepers have pointed out the AFB just seems to have disappeared.

I myself have found that the burning of all AFB combs is the most effective
way to deal with AFB, and suggest that all beekeepers adopt that practice.
But I get the impression that that's not why we don't see AFB as much
anymore.

In the U.S., we all used to hear that we "should" prophylactically treat
twice a year with oxytet to "prevent" AFB (please note my quotation
marks--I don't need to have the antibiotic resistance issue explained to
me).  Not surprisingly, oxytet-resistant strains of the *Paenibacillus*
bacterium became prevalent.  But back in those days, oxytet was generally
considered to be a *preventative* treatment, rather than a cure, since we
knew that it didn't kill the persistent spores in the combs of an infected
hive.  Infected hives were generally burned.

When oxytet-resistant strains appeared,  tylosin was then registered for
"the control" of AFB.  I feel that labeling any antibiotic for the
"control" of AFB was a huge mistake, since that is read as a "cure."  What
the treatment does is merely suppress the signs of disease--it isn't really
a "cure," since the combs still contain viable spores.

 That said, many commercial beekeepers started prophylactic/curative dosing
with tylosin in the fall.  This may well have been why we started hearing
less about AFB.  But it could also have been partly due to the ready
availability of preassembled frames, so that new beekeepers started out
"clean," rather than recycling old contaminated combs.  Another change was
that, thanks largely to Marla Spivak and BIP, a number of queen producers
have been selecting for freeze-kill hygienic behavior, which also helps
greatly to suppress AFB.

What now scares me is what happens when combs from an operation that has
dumped tylosin into their hives for many years, then sells those hives to
someone who stops doing so.  I've also, as you described, seen cases where
ABF then rises like the Phoenix from those old combs, once suppression by
tylosin ceases.  I saw it occur in a load of nucs purchased by another last
year.

I suspect that we are now sitting on a time bomb--millions of combs
containing dormant AFB spores, spread in operations throughout the
country.  And thousands of new beekeepers who either don't inspect their
hives for disease, or wouldn't recognize AFB if it were there (I've seen
this happen).  We may one day be talking about AFB as much as we used to.


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

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