Hi Lloyd,
I have been thinking about this post of yours for a few days now.  It is interesting and does make one think.
You wrote in part at the end of a very interesting list:

"Dr. Shiminuki recommends stopping the use of terramycin "one yard at a
time", presumably because he would expect at least some yards to show
resistance.

Something seems to be wrong here.  Either AFB is not as endemic as described
or resistance is widespread.

Comments?"


Hmm,  I also have observed similar things but not sure we are coming to the same conclusion but we probably are not far apart on this either.  First my observations here in MN are that nearly all spread of AFB is connected with used equipment - read used broodcombs.  There of course is some spread due to bees robbing out AFB killed colonies but that appears to be mostly a factor within a yard or over fairly short distances ( considerably less than what normal foraging distances ).  Really don't have an explanation for this observation but it seems to be the case.  If a beekeeper starts with new equipment they are very unlikely to have any disease problems for at least the first few years after which chalkbrood may start to show up.  Many old-timers are very good at identifying AFB and limiting its spread within their outfit but if they don't exchange used equipment with other beekeepers or buy used equipment their exposure to AFB is very limited.  At the same time AFB does occur nearly everywhere if you start to plot occurrences on a map.  But is tends to run within outfits more than in geographical areas.

My conclusion is used combs are the main source of AFB and AFB is really not that contagious compared to some other diseases of animals i.e. spread is fairly slow in an area unless you innoculate a colony with the huge amount of spores in used infected combs.  The clear implication of this is that we beekeepers are the main source of spread of AFB.  While that thought is not always easy to accept it means that we can control most spread of AFB and therefore vastly limit its damage to our beekeeping outfits and our beekeeping neighbors.

If a beekeeper has not acquired used combs they can likely stop using TM without any disease problems but if they have used combs in the outfit they better go slowly or they risk a major outbreak that will be difficult to deal with effectively at once.  Therefore the go one yard at a time advice.  Most beekeeping outfits have used comb from many sources ( talking commercial sized outfits here ) and often have scale scattered around the outfit as a result that can and will seed an outbreak if they stop using antibiotics.  We have seen this here with TM resistance i.e. major outbreaks of AFB in an outfit.  In many of these cases it is the same as if the beekeeper quit using antibiotics all at once.  Beekeepers can and do contain these outbreaks but it can be pretty costly since they must get rid of the infected comb.

My conclusion is:  Think infected of any used comb.  Inspect colonies regularly for disease and destroy AFB when you find it and you will probably never have a major outbreak whether or not   you use antibiotics.  Why treat if you don't have a problem?  If you don't know how to identify AFB you need to learn before you think about buying used combs.  Always think about infection control when moving frames from one colony to another.  Double that if you are moving combs from weak or dead hives to strong hives.  Medication can if properly used significantly reduce your exposure if you buy used equipment but you risk spreading disease throughout your outfit if you are not careful.

Resistant stock is out there but I am not sure it is as widespread as you seem to be thinking.  Absence of disease in itself is not necessarily due to resistance - it could just as easily be due to lack of exposure to infectious spores.  All colonies have some mechanisms to help limit the spread of AFB but some can easily handle truly enormous numbers of spores without becoming diseased.

This has gotten rather long.  Thanks again for bringing this up it is an interesting area that we all need to think about.

I quit using TM a few years back without any problems but no used equipment and confident I can identify AFB if and when it shows up and know what I need to do.

FWIW

blane


******************************************
Blane White
MN Dept of Agriculture
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