>
> >I was wondering about AFB resistance - what is the mechanism of that
> resistance - how does it manifest?
>

There are likely a number of mechanisms--antibacterial immune response in
the larvae, transgenerational immune priming via vitellogenin in the eggs,
and AFB-sensitive hygienic behavior by the nurses.   Not to mention the
presence of AFB-specific phage viruses in the combs.

> If so, might the disease manifest again when the hive encounters stress
such as a dearth period or a mite treatment?

Years ago, when I bred for Freeze Kill Hygiene, I found colonies to which I
could add a deep brood chamber fully infected with AFB, and they would
"disappear" the signs of disease within days.  The colonies would remain
free of signs of disease until there was a pollen dearth--and then I'd see
a few infected cells until a pollen flow resumed.  This indicated that the
spores remained present--just waiting for opportunity.

>
> >If a hive has a very few cells that show signs of AFB, is it possible
> for it to go into remission and overcome the disease?


I ran an experiment some years ago to answer the above question.  I
identified about ten colonies in which I found one or a few cells with
signs of AFB, but with the colony otherwise booming and healthy.  I marked
those colonies to track to see whether they went into "remission" and
cleared the infection.  Not a single one did--the infection increased in
each one over time.

My *guess* is that a colony that exhibits a "few cells" is likely
nonresistant,  Remission would be unlikely without treatment with Tylosin.
However, I am not an advocate for treating colonies with AFB, since the
treatment does not affect the spores in the combs, which may later spread
the disease to other colonies when combs are swapped.  I'm a very strong
proponent of burning every comb from infected colonies.  You can save the
bees if you want by shaking them into a new hive with foundation only (no
drawn combs) and treating with an effective antibiotic during the first
brood cycle.  I disinfect any boxes and other hive components in a hot tank.

>
>
> >How likely is it that a hive near one with AFB will also become
> diseased through drift rather than robbing out a dead/dying hive?
>

Although a study by Dr Mark Goodwin suggests that drifting may not be
important in transmission (Journal ofApicultural Research 33(4): 209-212
(1994) The effect of drifting honey bees on the spread of American
foulbrood infections), my own experience suggests that when an infected
colony is robbed out, that a proportion of nearby colonies then show signs
of infection.  I seldom see AFB in my operation any more, but when I used
to find an infected colony in a yard, I would inspect every other colony in
that yard, and only then give each of them a prophylactic treatment.  I
would burn any with ANY sign of infection.  Note that I put this in past
tense--once I got AFB under control years ago with a zero tolerance policy
and burning, I rarely see it any more.

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

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