American foulbrood (AFB) is a common and serious bacterial disease of honeybee brood, caused by Paenibacillus larvae. P. larvae is a spore-forming bacterium which is found worldwide. Spores are extremely hardly and can survive in dormancy for thirty-five years or more.
At first, AFB is slow to establish and only a few larvae will be affected. In advanced cases the brood pattern will be irregular. However, just because there is no irregular brood pattern doesn't mean that the hive isn't infected with AFB. Infected larvae and pupae, die after their cells have been capped. Adult bees may later partly or totally remove the caps, and as a result the caps may be perforated.
TransmissionAFB is transmitted to larvae from nurse bees or from spores remaining in the bottom of the brood cell. Exchanging combs containing remains of diseased larvae or honey, or both, laden with spores of B. larvae is the quickest way the disease spreads from colony to colony. A colony that is weakened by American foulbrood may be robbed, and the robber bees inadvertently carry honey containing spores of B. larvae to healthy colonies.
AFB is extremely contagious and spreads easily through interchange of infected beekeeping equipment or beekeeper clothes, feeding colonies infected honey or pollen, by honey bees robbing honey from infected hives or from extraction sites, and from drifting honey bees visiting from infected colonies.