I had a beekeeper stop by yesterday with a question. She says her two hives have performed poorly for the last two years and she could not figure out why.
She said she had a deep brood box in the back of her car. We went out and looked through the box. By the time I had pulled the third frame I knew she had American Foulbrood ( AFB ). After further inspection she had 6 of the 9 frames infected with AFB scale.
Both of her colonies had it. The weakest hive had very little bees left was a Carniolan. The stronger hive was a MN - Hyg and was fitting the bill as a disease resistant bee. It still had AFB but was coping with it better.
The solution she was going to follow was to burn all the frames and start over next year with new bees and new comb.
Treating the hive with TM or Tylan does nothing if we don't get rid of the AFB scale. It is the scale that is infectious, and failure to get rid of it does not fix the problem.
I asked her how she thought she got it. She said she didn't use any used equipment ( the most common way to get AFB ) or feed any store bought honey. The most likely scenario is that her bees robbed out a dead or dying colony that were near hers and brought the AFB tainted honey back to her hive. Sometimes the general public will see honey bees and put out honey to " help " them out with food. Honey can have AFB spores in it. That is why we never feed honey to our bees unless it is only our personal honey. AFB spores in honey has no effect on people at all and are not a concern.