Re: American Foulbrood (afb)
Just thought I'd add a little snipet to that (if I may, Robert).
It can be hard to understand why hives can have bacillus larvae bacteria in them but not get sick. One of the main reasons is that a bee larva has to be killed by the disease and turn into the sticky stuff Robert described, for the disease to take hold in the hive. But the way the bacteria kill the larva, is when the larva pupates, the bacteria penetrate it's gut wall, and kill it. If there are only a few bacteria, they cannot cause enough damage at pupation to kill the larva. The larva survives, and the infection is not spread. If the bee larva only gets infected with one bacteria, the bacteria cannot multiply into enough bacteria by the time the larva pupates, to kill the bee larva. The bee larva has to ingest quite a few bacteria while it is still quite young, for the bacteria to multiply into enough to kill the larva.
Therefore there can be low levels of bacillus larvae bacteria in a hive, but the likelihood of a larva getting enough to cause a fatal infection is very low, so the hive never shows symptoms of the disease.
Actually looking back I think that's kinda what Robert already said, but I'll leave it there, understanding this bit is part of the key to understanding the mechanics of this disease.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).